heroin and Disease-Models--Animal

Chronic drug exposure is hypothesized to recruit negative reinforcement processes that increase the magnitude and alter the mechanisms of drug reinforcement. Candidate substrates of negative reinforcement include increased signaling via stress-related neurotransmitters such as corticotropin releasing factor (CRF, acting at CRF receptors) or dynorphin (acting at kappa opioid receptors) and/or decreased signaling via reward-related neurotransmitters such as dopamine. Determinants of drug reinforcement can be examined with choice procedures, in which subjects choose between a drug of interest (e.g. heroin or cocaine) and a non-drug alternative reinforcer (e.g. food). This review summarizes evidence collected from studies of drug choice in rhesus monkeys to address the negative reinforcement hypothesis. In monkeys choosing between heroin and food, chronic heroin exposure and subsequent withdrawal produces a robust increase in heroin choice. This withdrawal-associated increase in heroin choice is blocked by morphine and by other mu opioid agonists used to treat opioid use disorder (methadone, buprenorphine); however, withdrawal-associated increases in heroin choice are not reliably blocked by antagonists of CRF or kappa opioid receptors or by an indirect dopamine agonist. In monkeys choosing between cocaine and food, chronic cocaine exposure and withdrawal fail to increase cocaine choice or alter sensitivity of cocaine choice to treatment with candidate therapeutics including an indirect dopamine agonist and a kappa opioid receptor antagonist. These results support a role for negative reinforcement in self-administration of heroin but not cocaine. The constellation of neurobiological changes that constitutes the negative reinforcing stimulus in opioid-dependent rhesus monkeys remains to be determined.

Topics: Animals; Choice Behavior; Cocaine; Cocaine-Related Disorders; Disease Models, Animal; Food; Heroin; Heroin Dependence; Humans; Macaca mulatta; Narcotic Antagonists; Opioid-Related Disorders; Reinforcement, Psychology; Substance Withdrawal Syndrome

Opioid abuse in humans is characterized by discontinuous periods of drug use and abstinence. With time, the probability of falling into renewed drug consumption becomes particularly high and constitutes a considerable problem in the management of heroin addicts. The major problem in the treatment of opioid dependence still remains the occurrence of relapse, to which stressful life events, renewed use of heroin, and exposure to drug-associated environmental cues are all positively correlated. To study the neurobiology of relapse, many research groups currently use the reinstatement animal model, which greatly contributed to disentangle the mechanisms underlying relapse to drug-seeking in laboratory animals. The use of this model is becoming increasingly popular worldwide, and new versions have been recently developed to better appreciate the differential contribution of each opioid receptor subtype to the relapse phenomenon. In this chapter we review the state of the art of our knowledge on the specific role of the opioid receptors as unrevealed by the reinstatement animal model of opioid-seeking behavior.

Topics: Analgesics, Opioid; Animals; Behavior, Addictive; Disease Models, Animal; Heroin; Humans; Opioid-Related Disorders; Receptors, Opioid; Substance-Related Disorders

The inability to maintain drug abstinence is often referred to as relapse and consists of a process by which an abstaining individual slips back into old behavioral patterns and substance use. Animal models of relapse have been developed over the last decades and significantly contributed to shed light on the neurobiological mechanisms underlying vulnerability to relapse. The most common procedure to study drug-seeking and relapse-like behavior in animals is the "extinction-reinstatement model." Originally elaborated by Pavlov and Skinner, the concepts of reinforced operant responding were applied to addiction research not before 1971 (Stretch et al., Can J Physiol Pharmacol 49:581-589, 1971), and the first report of a reinstatement animal model as it is now used worldwide was published only 10 years later (De Wit and Stewart, Psychopharmacology 75:134-143, 1981). According to the proposed model, opioids are typically self-administered intravenously, as humans do, and although rodents are most often employed in these studies, a variety of species including nonhuman primates, dogs, cats, and pigeons can be used. Several operant responses are available, depending on the species studied. For example, a lever press or a nose poke response typically is used for rodents, whereas a panel press response typically is used for nonhuman primates. In this chapter we describe a simple and easily reproducible protocol of heroin-seeking reinstatement in rats, which proved useful to study the neurobiological mechanisms underlying relapse to heroin and vulnerability factors enhancing the resumption of heroin-seeking behavior.

Topics: Administration, Intravenous; Analgesics, Opioid; Animals; Behavior Control; Behavior, Addictive; Conditioning, Operant; Cues; Disease Models, Animal; Drug-Seeking Behavior; Heroin; Infusions, Intravenous; Male; Opioid-Related Disorders; Rats; Rats, Sprague-Dawley; Rats, Wistar; Reinforcement, Psychology; Reward; Self Administration; Substance-Related Disorders

Cocaine and heroin cause impairment of neural plasticity in the brain including striatum. This study aimed to identify genes differentially expressed in the striatum of cynomolgus monkeys in response to cocaine and heroin. After chronic administration of cocaine and heroin in the monkeys, we performed large-scale transcriptome profiling in the striatum using RNA-Seq technology and analysed functional annotation. We found that 547 and 1238 transcripts were more than 1.5-fold up- or down-regulated in cocaine- and heroin-treated groups, respectively, compared to the control group, and 3432 transcripts exhibited differential expression between cocaine- and heroin-treated groups. Functional annotation analysis indicated that genes associated with nervous system development (NAGLU, MOBP and TTL7) and stress granule disassembly (KIF5B and KLC1) were differentially expressed in the cocaine-treated group compared to the control group, whereas gene associated with neuron apoptotic process (ERBB3) was differentially expressed in the heroin-treated group. In addition, IPA network analysis indicated that genes (TRAF6 and TRAF3IP2) associated with inflammation were increased by the chronic administration of cocaine and heroin. These results provide insight into the correlated molecular mechanisms as well as the upregulation and down-regulation of genes in the striatum after chronic exposure to cocaine and heroin.

Topics: Animals; Cocaine; Cocaine-Related Disorders; Corpus Striatum; Disease Models, Animal; Female; Gene Expression Regulation; Heroin; Heroin Dependence; Humans; Kinesins; Macaca fascicularis; Neuronal Plasticity; RNA-Seq; Self Administration; Transcriptome

Patients with opioid use disorder experience high rates of relapse during recovery, despite successful completion of rehabilitation programs. A key factor contributing to this problem is the long-lasting nature of drug-seeking behavior associated with opioid use. We modeled this behavior in a rat drug self-administration paradigm in which drug-seeking is higher after extended abstinence than during the acute abstinence phase. The goal of this study was to determine the contribution of discrete or discriminative drug cues and drug dosage to time-dependent increases in drug-seeking. We examined heroin-seeking after 2 or 21 days of abstinence from two different self-administration cue-context environments using high or low doses of heroin and matched animals for their drug intake history. When lower dosages of heroin are used in discriminative or discrete cue protocols, drug intake history contributed to drug-seeking after abstinence, regardless of abstinence length. Incubation of opioid craving at higher dosages paired with discrete drug cues was not dependent on drug intake. Thus, interactions between drug cues and drug dosage uniquely determined conditions permissible for incubation of heroin craving. Understanding factors that contribute to long-lasting opioid-seeking can provide essential insight into environmental stimuli and drug-taking patterns that promote relapse after periods of successful abstinence.

Topics: Animals; Craving; Cues; Disease Models, Animal; Dose-Response Relationship, Drug; Drug-Seeking Behavior; Heroin; Male; Opioid-Related Disorders; Rats, Sprague-Dawley; Recurrence; Self Administration; Substance Withdrawal Syndrome

It is difficult to translate results from animal research on addiction to an understanding of the behavior of human drug users. Despite decades of basic research on neurobiological mechanisms of drug addiction, treatment options remain largely unchanged. A potential reason for this is that mechanistic studies using rodent models do not incorporate a critical facet of human addiction: volitional choices between drug use and non-drug social rewards (e.g., employment and family). Recently, we developed an operant model in which rats press a lever for rewarding social interaction with a peer and then choose between an addictive drug (heroin or methamphetamine) and social interaction. Using this model, we showed that rewarding social interaction suppresses drug self-administration, relapse to drug seeking, and brain responses to drug-associated cues. Here, we describe a protocol for operant social interaction using a discrete-trial choice between drugs and social interaction that causes voluntary abstinence from the drug and tests for incubation of drug craving (the time-dependent increase in drug seeking during abstinence). This protocol is flexible but generally requires 8-9 weeks for completion. We also provide a detailed description of the technical requirements and procedures for building the social self-administration and choice apparatus. Our protocol provides a reliable way to study the role of operant social reward in addiction and addiction vulnerability in the context of choices. We propose that this protocol can be used to study brain mechanisms of operant social reward and potentially impairments in social reward in animal models of psychiatric disorders and pain.

Topics: Animals; Choice Behavior; Conditioning, Operant; Disease Models, Animal; Drug-Seeking Behavior; Female; Heroin; Male; Methamphetamine; Models, Psychological; Rats; Rats, Long-Evans; Rats, Sprague-Dawley; Remifentanil; Self Administration; Social Behavior; Substance-Related Disorders

Relapse into drug use is a major problem faced by recovering addicts. In humans, an intensification of the desire for the drug induced by environmental cues-incubation of drug craving-has been observed. In rodents, this phenomenon has been modeled by studying drug seeking under extinction after different times of drug withdrawal (or using a natural reinforcer). Although much progress has been made, an integrated approach simultaneously studying different drug classes and natural reward and examining different brain regions is lacking. Lewis rats were used to study the effects of cocaine, heroin, and sucrose seeking incubation on six key brain regions: the nucleus accumbens shell/core, central/basolateral amygdala, and dorsomedial/ventromedial prefrontal cortex. We analyzed PSD95 and gephyrin protein levels, gene expression of glutamatergic, GABAergic and endocannabinoid elements, and amino acid transmitter levels. The relationships between the areas studied were examined by Structural Equation Modelling. Pathways from medial prefrontal cortex and basolateral complex of the amygdala to central nucleus of the amygdala, but not to the nucleus accumbens, were identified as common elements involved in the incubation phenomenon for different substances. These results suggest a key role for the central nucleus of amygdala and its cortical and amygdalar afferences in the incubation phenomenon, and we suggest that by virtue of its regulatory effects on glutamatergic and GABAergic dynamics within amygdalar circuits, the endocannabinoid system might be a potential target to develop medications that are effective in the context of relapse.

Topics: Analgesics, Opioid; Animals; Behavior, Animal; Central Amygdaloid Nucleus; Cocaine; Cocaine-Related Disorders; Disease Models, Animal; Dopamine Uptake Inhibitors; Heroin; Male; Opioid-Related Disorders; Rats; Rats, Inbred Lew; Reinforcement, Psychology; Self Administration; Sucrose

Drug addiction is a chronic disorder that is characterized by compulsive drug seeking and involves cycling between periods of compulsive drug use, abstinence, and relapse. In both human addicts and animal models of addiction, chronic food restriction has been shown to increase rates of relapse. Previously, our laboratory has demonstrated a robust increase in drug seeking following a period of withdrawal in chronically food-restricted rats compared with sated rats. To date, the neural mechanisms that mediate the effect of chronic food restriction on drug seeking have not been elucidated. However, the paraventricular nucleus of the thalamus (PVT) appears to be a promising target to investigate. The objective of the current study was to examine the role of the PVT in the augmentation of heroin seeking induced by chronic food restriction. Male Long-Evans rats were trained to self-administer heroin for 10 days. Rats were then removed from the training chambers and experienced a 14-day withdrawal period with either unrestricted (sated) or mildly restricted (FDR) access to food. On day 14, rats underwent a 1-hour heroin-seeking test under extinction conditions, during which neural activity in the PVT was either inhibited or increased using pharmacological or chemogenetic approaches. Unexpectedly, inhibition of the PVT did not alter heroin seeking in food-restricted or sated rats, while enhancing neural activity in the PVT-attenuated heroin seeking in food-restricted rats. These results indicate that PVT activity can modulate heroin seeking induced by chronic food restriction.

Topics: Animals; Behavior, Animal; Disease Models, Animal; Food Deprivation; Heroin; Heroin Dependence; Male; Paraventricular Hypothalamic Nucleus; Rats; Rats, Long-Evans

We have previously demonstrated that heroin's first metabolite, 6-acetylmorphine (6-AM), is an important mediator of heroin's acute effects. However, the significance of 6-AM to the rewarding properties of heroin still remains unknown. The present study therefore aimed to examine the contribution of 6-AM to heroin-induced reward and locomotor sensitization. Mice were tested for conditioned place preference (CPP) induced by equimolar doses of heroin or 6-AM (1.25-5 μmol/kg). Psychomotor activity was recorded during the CPP conditioning sessions for assessment of drug-induced locomotor sensitization. The contribution of 6-AM to heroin reward and locomotor sensitization was further examined by pretreating mice with a 6-AM specific antibody (anti-6-AM mAb) 24 hours prior to the CPP procedure. Both heroin and 6-AM induced CPP in mice, but heroin generated twice as high CPP scores compared with 6-AM. Locomotor sensitization was expressed after repeated exposure to 2.5 and 5 μmol/kg heroin or 6-AM, but not after 1.25 μmol/kg, and we found no correlation between the expression of CPP and the magnitude of locomotor sensitization for either opioid. Pretreatment with anti-6-AM mAb suppressed both heroin-induced and 6-AM-induced CPP and locomotor sensitization. These findings provide evidence that 6-AM is essential for the rewarding and sensitizing properties of heroin; however, heroin caused stronger reward compared with 6-AM. This may be explained by the higher lipophilicity of heroin, providing more efficient drug transfer to the brain, ensuring rapid increase in the brain 6-AM concentration.

Topics: Analgesics, Opioid; Animals; Brain; Conditioning, Psychological; Disease Models, Animal; Heroin; Locomotion; Male; Mice; Mice, Inbred C57BL; Morphine Derivatives; Opioid-Related Disorders; Reward

Opiate addiction has a high rate of relapse. The accumulating evidence shows that electroacupuncture (EA) may be effective for the treatment of opiate relapse. However, the change of expression of CB1-Rs and CB2-Rs involve in 2Hz EA anti-relapse pathway is still unclear. To explore the changes of expression of CB1-Rs and CB2-Rs, heroin self-administration (SA) model rats were adopted and treated using 2Hz EA. The expressions of CB1-Rs and CB2-Rs were observed using immunohistochemistry method. The results showed that, compared with the control group, active pokes in the heroin-addicted group increased, while the active pokes decreased significantly in 2Hz EA group compared with heroin-addicted group. Correspondingly, the expression of CB1-Rs in prefrontal cortex (PFC), hippocampus (Hip), nucleus accumbens (NAc) and ventral tegmental area (VTA) all increased significantly while the expression of CB2-Rs in those relapse-relevant brain regions decreased obviously in heroin-addicted group when compared with the control group. In addition, the expression of CB1-Rs obviously decreased in the 2Hz EA group while the expression of CB2-Rs in those relapse-relevant brain regions increased significantly when compared with the heroin-addicted group. It indicated that 2Hz EA could attenuate the heroin-evoked seeking behaviors effectively. The anti-relapse effects of 2Hz EA might be related to the decrease of CB1-Rs and increase of CB2-Rs expression in relapse-relevant brain regions of heroin SA rats.

Topics: Animals; Behavior, Animal; Brain; Disease Models, Animal; Drug-Seeking Behavior; Electroacupuncture; Extinction, Psychological; Heroin; Heroin Dependence; Locomotion; Male; Narcotic Antagonists; Rats, Sprague-Dawley; Receptor, Cannabinoid, CB1; Receptor, Cannabinoid, CB2; Recurrence; Self Administration; Signal Transduction

Many preclinical studies examined cue-induced relapse to heroin and cocaine seeking in animal models, but most of these studies examined only one drug at a time. In human addicts, however, polydrug use of cocaine and heroin is common. We used a polydrug self-administration relapse model in rats to determine similarities and differences in brain areas activated during cue-induced reinstatement of heroin and cocaine seeking. We trained rats to lever press for cocaine (1.0 mg/kg per infusion, 3-hr/day, 18 day) or heroin (0.03 mg/kg per infusion) on alternating days (9 day for each drug); drug infusions were paired with either intermittent or continuous light cue. Next, the rats underwent extinction training followed by tests for cue-induced reinstatement where they were exposed to either heroin- or cocaine-associated cues. We observed cue-selective reinstatement of drug seeking: the heroin cue selectively reinstated heroin seeking and the cocaine cue selectively reinstated cocaine seeking. We used Fos immunohistochemistry to assess cue-induced neuronal activation in different subregions of the medial prefrontal cortex, dorsal striatum, nucleus accumbens, and amygdala. Fos expression results indicated that only the prelimbic cortex (PL) was activated by both heroin and cocaine cues; in contrast, no significant cue-induced neuronal activation was observed in other brain areas. RNA in situ hybridization indicated that the proportion of glutamatergic and GABAergic markers in PL Fos-expressing cells was similar for the heroin and cocaine cue-activated neurons. Overall, the results indicate that PL may be a common brain area involved in both heroin and cocaine seeking during polydrug use.

Topics: Amygdala; Animals; Brain; Cocaine; Conditioning, Operant; Corpus Striatum; Cues; Disease Models, Animal; Drug-Seeking Behavior; Extinction, Psychological; Heroin; Male; Nucleus Accumbens; Prefrontal Cortex; Rats, Long-Evans

Addiction is a chronic disease characterized by persistent vulnerability to relapse during abstinence. In animal models of addiction, accumulating evidence suggests that exposure to environmental enrichment (EE) during periods of abstinence can have curative effects on addiction and reduce the risks of relapse. However, until present most studies have mainly focused on cocaine. In this study, we investigated whether EE could have beneficial effects on cue-induced seeking for several psychoactive drugs belonging to different pharmacological classes such as methamphetamine (METH), heroin (HER) and nicotine (NIC).. After self-administration training of METH, HER and NIC, rats were housed in enriched (EE) or standard environments (SE) for 21-28 days of forced abstinence and then drug-seeking behavior was assessed in the absence of the drug.. We found that, compared to SE housing, exposure to EE reduced drug seeking behavior for all drugs tested.. These findings suggest that the anti-craving effects of EE are general for a wide variety of drugs and support the hypothesis that environmental stimulation may be a general intervention for attenuating relapse in humans.

Topics: Amphetamine-Related Disorders; Animals; Craving; Cues; Disease Models, Animal; Drug-Seeking Behavior; Environment; Generalization, Psychological; Heroin; Heroin Dependence; Housing, Animal; Male; Methamphetamine; Nicotine; Psychotropic Drugs; Rats, Sprague-Dawley; Self Administration; Tobacco Use Disorder

In recent years, drug conjugate vaccines have shown promise as therapeutics for substance use disorder. As a means to improve the efficacy of a heroin conjugate vaccine, we systematically explored 20 vaccine formulations with varying combinations of carrier proteins and adjuvants. In regard to adjuvants, we explored a Toll-like receptor 9 (TLR9) agonist and a TLR3 agonist in the presence of alum. The TLR9 agonist was cytosine-guanine oligodeoxynucleotide 1826 (CpG ODN 1826), while the TLR3 agonist was virus-derived genomic doubled-stranded RNA (dsRNA). The vaccine formulations containing TLR3 or TLR9 agonist alone elicited strong antiheroin antibody titers and blockade of heroin-induced antinociception when formulated with alum; however, a combination of TLR3 and TLR9 adjuvants did not result in improved efficacy. Investigation of month-long stability of the two lead formulations revealed that the TLR9 but not the TLR3 formulation was stable when stored as a lyophilized solid or as a liquid over 30 days. Furthermore, mice immunized with the TLR9 + alum heroin vaccine gained significant protection from lethal heroin doses, suggesting that this vaccine formulation is suitable for mitigating the harmful effects of heroin, even following month-long storage at room temperature.

Topics: Adjuvants, Immunologic; Analgesics, Opioid; Animals; Disease Models, Animal; Drug Overdose; Heroin; Heroin Dependence; Humans; Male; Mice; Oligodeoxyribonucleotides; Toll-Like Receptor 3; Toll-Like Receptor 9; Vaccination; Vaccines, Conjugate

Understanding the process of relapse to abused drugs and ultimately developing treatments that can reduce the incidence of relapse remains the primary goal for the study of substance dependence. Therefore, exploring the metabolite characteristics during the relapse stage is valuable.. A heroin self-administered rat model was employed, and analysis of the. Sixteen metabolites in the serum of rats, including phospholipids, intermediates in TCA (Tricarboxylic Acid Cycle) cycle, keto bodies, and precursors for neurotransmitters, underwent a significant change in the reinstatement stage compared with those in the control group. In particular, energy production was greatly disturbed as evidenced by different aspects such as an increase in glucose and decrease in intermediates of glycolysis and the TCA cycle. The finding that the level of 3-hydroxybutyrate and acetoacetate increased significantly suggested that energy production was activated from fatty acids. The concentration of phenylalanine, glutamine, and choline, the precursors of major neurotransmitters, increased during the reinstatement stage which indicated that an alteration in neurotransmitters in the brain might occur along with the disturbance in substrate supply in the circulatory system.. Heroin reinforcement resulted in impaired energy production via different pathways, including glycolysis, the TCA cycle, keto body metabolism, etc. A disturbance in the substrate supply in the circulatory system may partly explain heroin toxicity in the central nervous system. These findings provide new insight into the mechanism underlying the relapse to heroin use.

Topics: Animals; Brain; Disease Models, Animal; Heroin; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Male; Metabolomics; Rats, Sprague-Dawley; Self Administration

Drug dependence and withdrawal syndrome induced by abrupt cessation of opioid administration remain a severe obstacle in the clinical treatment of chronic pain and opioid drug addiction. One of the key symptoms during opioid withdrawal is hyperalgesia. The mechanism of opioid withdrawal-induced hyperalgesia remains unclear. P2X2 and P2X3 receptors, members of P2X receptor subunits, act as the integrator of multiple forms of noxious stimuli and play an important role in nociception transduction of chronic neuropathic and inflammatory pain. The process of P2X2 and P2X3 receptor antagonism inhibits inflammatory hyperalgesia, involving the spinal opioid system. However, the role of P2X receptors involved in opioid withdrawal-induced hyperalgesia has seldom been discussed. To explore the role of P2X2 and P2X3 receptors in the opioid-induced hyperalgesia, heroin self-administration rats were adopted, and the thermal and mechanical nociceptive thresholds were evaluated using the paw withdrawal test after abstinence from heroin for 8 days. In addition, the expressions of P2X2 and P2X3 receptors in dorsal root ganglia were analyzed by immunofluorescence. The results showed that after 8 days of abstinence, heroin self-administration rats showed thermal hyperalgesia and mechanical allodynia. Meanwhile, the expressions of the P2X2 and P2X3 receptors in dorsal root ganglia were increased. These results suggest that upregulation of P2X2 and P2X3 receptors might partially play a role in heroin withdrawal-induced hyperalgesia.

Topics: Analgesics, Opioid; Animals; Disease Models, Animal; Ganglia, Spinal; Heroin; Heroin Dependence; Hot Temperature; Hyperalgesia; Male; Pain Threshold; Rats, Sprague-Dawley; Receptors, Purinergic P2X2; Receptors, Purinergic P2X3; Self Administration; Substance Withdrawal Syndrome; Touch; Up-Regulation

The changes in brain function that perpetuate opiate addiction are unclear. In our studies of human narcolepsy, a disease caused by loss of immunohistochemically detected hypocretin (orexin) neurons, we encountered a control brain (from an apparently neurologically normal individual) with 50% more hypocretin neurons than other control human brains that we had studied. We discovered that this individual was a heroin addict. Studying five postmortem brains from heroin addicts, we report that the brain tissue had, on average, 54% more immunohistochemically detected neurons producing hypocretin than did control brains from neurologically normal subjects. Similar increases in hypocretin-producing cells could be induced in wild-type mice by long-term (but not short-term) administration of morphine. The increased number of detected hypocretin neurons was not due to neurogenesis and outlasted morphine administration by several weeks. The number of neurons containing melanin-concentrating hormone, which are in the same hypothalamic region as hypocretin-producing cells, did not change in response to morphine administration. Morphine administration restored the population of detected hypocretin cells to normal numbers in transgenic mice in which these neurons had been partially depleted. Morphine administration also decreased cataplexy in mice made narcoleptic by the depletion of hypocretin neurons. These findings suggest that opiate agonists may have a role in the treatment of narcolepsy, a disorder caused by hypocretin neuron loss, and that increased numbers of hypocretin-producing cells may play a role in maintaining opiate addiction.

Topics: Animals; Brain; Cataplexy; Cell Count; Disease Models, Animal; Dose-Response Relationship, Drug; Heroin; Humans; Male; Mice, Inbred C57BL; Morphine; Narcolepsy; Neurogenesis; Neurons; Opiate Alkaloids; Orexins; Rats, Sprague-Dawley; Substance-Related Disorders

Drug addiction is a complex disease that is impacted by numerous factors. One such factor, time of day, influences drug intake, but there have been no investigations of how time of day affects the amount of drug taken and the development of addiction-like behavior. Previous data from our group show circadian disruption in rats given access to heroin during the light phase, which is important because circadian disruption, itself, can increase drug intake. Thus, the goal of this experiment was to determine how time of day of access affects heroin self-administration and the development of addiction-like behaviors including escalation of heroin intake, willingness to work for heroin on a progressive ratio schedule of reinforcement, seeking during extinction, incubation of seeking, and reinstatement of heroin-seeking behavior.. Male Sprague Dawley rats were given the opportunity to self-administer heroin for 6 h per trial during the second half of either the light or dark phase for 18 trials, including one progressive ratio challenge. Rats then underwent 14 days of abstinence, with a 5-h extinction test occurring on both the first and the 14th days of abstinence. The second extinction test was followed by a heroin prime and 1 h of reinstatement testing. On the following day, a subset of rats were tested in an additional extinction test where rats were tested either at the same time of the day as their previous self-administration sessions or during the opposite light/dark phase.. Relative to Light Access rats, Dark Access rats took more heroin, exhibited more goal-directed behavior, exhibited more seeking during the dark phase, failed to extinguish seeking during the 5-h extinction test in the dark phase, and exhibited greater incubation of heroin seeking following abstinence. However, Dark Access rats did not escalate drug taking over trials, work harder for drug, or seek more during drug-induced reinstatement than Light Access rats.. These results show that time of access to heroin affects overall heroin intake and seeking in extinction, but does not affect other addiction-like behaviors in rats.

Topics: Animals; Behavior, Addictive; Circadian Rhythm; Disease Models, Animal; Extinction, Psychological; Heroin; Heroin Dependence; Male; Rats; Rats, Sprague-Dawley; Reinforcement, Psychology; Self Administration

Vaccines may offer a new treatment strategy for opioid use disorders and opioid-related overdoses. To speed translation, this study evaluates opioid conjugate vaccines containing components suitable for pharmaceutical manufacturing and compares analytical assays for conjugate characterization. Three oxycodone-based haptens (OXY) containing either PEGylated or tetraglycine [(Gly)

Topics: Adjuvants, Immunologic; Animals; Brain; Carrier Proteins; Disease Models, Animal; Drug Carriers; Drug Compounding; Drug Overdose; Haptens; Hemocyanins; Heroin; Humans; Male; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Nociception; Opioid-Related Disorders; Oxycodone; Tissue Distribution; Vaccines, Conjugate

To evaluate regulation of the endoplasmic reticulum stress (ERS) response by acupuncture and to investigate its neuroprotective effect on brain injury caused by heroin addiction.. A total of 48 male Sprague-Dawley rats were randomly divided into a healthy control group (Control), an untreated heroin exposed group (Heroin) and a heroin exposed group receiving electroacupuncture (EA) treatment at GV14 and GV20 (Heroin+acupuncture) with n=16 rats per group. A rat model of heroin addiction was established by intramuscular injection of incremental doses of heroin for 8 consecutive days. A rat model of heroin relapse was established according to the exposure (addiction) → detoxification method. Apoptotic changes in nerve cells in the hippocampus and ventral tegmental area (VTA) were evaluated in each group of rats using terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) assay. PERK, eIF2a, CHOP, IRE1 and JNK gene expression and protein expression were measured using quantitative real-time PCR (RT-qPCR) assay and immunohistochemical assay, respectively.. The total number of positive nerve cells in the hippocampus and VTA was significantly lower in the Heroin+acupuncture group than in the Heroin group (p<0.01). Compared with the Heroin group, mRNA and protein expression of PERK, eIF2a, CHOP, IRE1 and JNK in the hippocampus and VTA were significantly downregulated in the Heroin+acupuncture group (p<0.05).. The acupuncture-regulated ERS response appears to mediate the neuroprotective effect of acupuncture in heroin-addicted rats with brain injury. Inhibition of CHOP and JNK upregulation and reduction of nerve cell apoptosis may be the main mechanisms underlying the effects of acupuncture on heroin addiction-induced brain injury.

Topics: Acupuncture Therapy; Animals; Apoptosis; Brain; Brain Injuries; Disease Models, Animal; Electroacupuncture; Endoplasmic Reticulum Stress; Heroin; Heroin Dependence; JNK Mitogen-Activated Protein Kinases; Male; Neuroprotective Agents; Rats, Sprague-Dawley; Transcription Factor CHOP

The dopamine (DA) D3 receptor (D3R) is highly expressed in the basolateral nucleus of the amygdala (BLA), a neural region critical for processing opiate-related reward and withdrawal aversion-related memories. Functionally, D3R transmission is linked to downstream Cdk5 and calcineurin signaling, both of which regulate D3R activity states and play critical roles in memory-related synaptic plasticity. Previous evidence links D3R transmission to opiate-related memory processing, however little is known regarding how chronic opiate exposure may alter D3R-dependent memory mechanisms. Using conditioned place preference (CPP) and withdrawal aversion (conditioned place aversion; CPA) procedures in rats, combined with molecular analyses of BLA protein expression, we examined the effects of chronic opiate exposure on the functional role of intra-BLA D3R transmission during the acquisition of opiate reward or withdrawal aversion memories. Remarkably, we report that the state of opiate exposure during behavioural conditioning (opiate-naïve/non-dependent vs. chronically exposed and in withdrawal) controlled the functional role of intra-BLA D3R transmission during the acquisition of both opiate reward memories and withdrawal-aversion associative memories. Thus, whereas intra-BLA D3R blockade had no effect on opiate reward memory formation in the non-dependent state, blockade of intra-BLA D3R transmission prevented the formation of opiate reward and withdrawal aversion memory in the chronically exposed state. This switch in the functional role of D3R transmission corresponded to significant increases in Cdk5 phosphorylation and total expression levels of calcineurin, and a corresponding decrease in intra-BLA D3R expression. Inhibition of either intra-BLA Cdk5 or calcineurin reversed these effects, switching intra-BLA associative memory formation back to a D3R-independent mechanism.

Topics: Analgesics, Opioid; Animals; Association Learning; Avoidance Learning; Basolateral Nuclear Complex; Calcineurin; Conditioning, Psychological; Cyclin-Dependent Kinase 5; Disease Models, Animal; Heroin; Male; Memory; Opioid-Related Disorders; Ranolazine; Rats, Sprague-Dawley; Receptors, Dopamine D3; Reward; Signal Transduction; Spatial Behavior; Substance Withdrawal Syndrome

Addiction is a chronic brain disorder that progressively invades all aspects of personal life. Accordingly, addiction to opiates severely impairs interpersonal relationships, and the resulting social isolation strongly contributes to the severity and chronicity of the disease. Uncovering new therapeutic strategies that address this aspect of addiction is therefore of great clinical relevance. We recently established a mouse model of heroin addiction in which, following chronic heroin exposure, 'abstinent' mice progressively develop a strong and long-lasting social avoidance phenotype. Here, we explored and compared the efficacy of two pharmacological interventions in this mouse model. Because clinical studies indicate some efficacy of antidepressants on emotional dysfunction associated with addiction, we first used a chronic 4-week treatment with the serotonergic antidepressant fluoxetine, as a reference. In addition, considering prodepressant effects recently associated with kappa opioid receptor signaling, we also investigated the kappa opioid receptor antagonist norbinaltorphimine (norBNI). Finally, we assessed whether fluoxetine and norBNI could reverse abstinence-induced social avoidance after it has established. Altogether, our results show that two interspaced norBNI administrations are sufficient both to prevent and to reverse social impairment in heroin abstinent animals. Therefore, kappa opioid receptor antagonism may represent a useful approach to alleviate social dysfunction in addicted individuals.

Topics: Animals; Antidepressive Agents, Second-Generation; Behavior, Animal; Disease Models, Animal; Fluoxetine; Grooming; Heroin; Heroin Dependence; Male; Mice; Mice, Inbred C57BL; Naltrexone; Narcotic Antagonists; Receptors, Opioid, kappa; Social Behavior; Time; Treatment Outcome

Addiction is characterized by drug craving, compulsive drug taking and relapse, which is attributed to aberrant neuroadaptation in brain regions implicated in drug addiction, induced by changes in gene and protein expression in these regions after chronic drug exposure. Accumulating evidence suggests that the dorsal hippocampus (DH) plays an important role in mediating drug-seeking and drug-taking behavior and relapse. However, the molecular mechanisms underlying these effects of the DH are unclear. In the present study, we employed a label-free quantitative proteomic approach to analyze the proteins altered in the DH of heroin self-administering rats. A total of 4015 proteins were quantified with high confidence, and 361 proteins showed significant differences compared with the saline control group. Among them, cyclin-dependent kinase 5 (CDK5) and ras homolog family member B (RhoB) were up-regulated in rats with a history of extended access to heroin. Functionally, inhibition of CDK5 in the DH enhanced heroin self-administration, indicating that CDK5 signaling in the DH acts as a homeostatic compensatory mechanism to limit heroin-taking behavior, whereas blockade of the Rho-Rho kinase (ROCK) pathway attenuated context-induced heroin relapse, indicating that RhoB signaling in the DH is required for the retrieval (recall) of addiction memory. Our findings suggest that manipulation of CDK5 signaling in the DH may be essential in determining vulnerability to opiate taking, whereas manipulation of RhoB signaling in the DH may be essential in determining vulnerability to relapse. Overall, the present study suggests that the DH can exert dissociative effects on heroin addiction through CDK5 and RhoB signaling.

Topics: Animals; Behavior, Animal; Cyclin-Dependent Kinase 5; Disease Models, Animal; Drug-Seeking Behavior; Heroin; Heroin Dependence; Hippocampus; Male; Narcotics; Proteomics; Rats; Rats, Sprague-Dawley; Recurrence; rhoB GTP-Binding Protein; Self Administration; Signal Transduction

Opioid addiction, including addiction to heroin, has markedly increased in the past decade. The cost and pervasiveness of heroin addiction, including resistance to recovery from addiction, provide a compelling basis for developing novel therapeutic strategies. Deep brain stimulation may represent a viable alternative strategy for the treatment of intractable heroin addiction, particularly in individuals who are resistant to traditional therapies. Here we provide preclinical evidence of the therapeutic potential of high-frequency stimulation of the subthalamic nucleus (STN HFS) for heroin addiction. STN HFS prevented the re-escalation of heroin intake after abstinence in rats with extended access to heroin, an animal model of compulsive heroin taking. STN HFS inhibited key brain regions, including the substantia nigra, entopeduncular nucleus, and nucleus accumbens shell measured using brain mapping analyses of immediate-early gene expression and produced a robust silencing of STN neurons as measured using whole-cell recording ex vivo. These results warrant further investigation to examine the therapeutic effects that STN HFS may have on relapse in humans with heroin addiction.

Topics: Analgesics, Opioid; Animals; Compulsive Behavior; Deep Brain Stimulation; Disease Models, Animal; Drug-Seeking Behavior; Heroin; Heroin Dependence; Male; Membrane Potentials; Proto-Oncogene Proteins c-fos; Rats, Wistar; Self Administration; Subthalamic Nucleus; Tissue Culture Techniques

Topics: Analgesics, Opioid; Animals; Dentate Gyrus; Disease Models, Animal; Drug-Seeking Behavior; Entorhinal Cortex; Glutamic Acid; Heroin; Heroin Dependence; Male; MAP Kinase Signaling System; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Saccharin; Synaptic Transmission

Opioid abuse remains a significant public health problem; together with the greater availability of marijuana in some regions there is an increasing likelihood that opioids and marijuana will be used together. Polydrug abuse is associated with increased toxicity and poorer treatment outcome; thus, a better understanding of the consequences of repeated coadministration of these drugs will facilitate the development of better prevention and treatment strategies. This study examined the effects of daily treatment with the cannabinoid receptor agonist delta-9-tetrahydrocannabinol (Δ-THC) and its discontinuation on self-administration of heroin in rhesus monkeys (n=4) lever-pressing under a fixed-ratio 30 schedule. Heroin self-administration (0.32-32 μg/kg/infusion, intravenously) generated an inverted U-shaped dose-effect curve. Administered acutely, Δ-THC (0.01-0.32 mg/kg, subcutaneously) dose dependently decreased responding for heroin and flattened the self-administration dose-effect curve. Daily treatment with Δ-THC (0.01-0.1 mg/kg/12 h, subcutaneously) either had no effect on or decreased responding for heroin. In addition, daily treatment did not significantly impact extinction of heroin self-administration or resumption of responding for heroin after extinction. Discontinuation of daily Δ-THC treatment did not systematically impact rates of heroin self-administration. These data suggest that repeated administration of a cannabinoid receptor agonist likely does not increase, and possibly decreases, the positive reinforcing effects of a mu opioid receptor agonist.

Topics: Analgesics, Non-Narcotic; Analysis of Variance; Animals; Conditioning, Operant; Disease Models, Animal; Dronabinol; Female; Heroin; Heroin Dependence; Macaca mulatta; Male; Narcotics; Reinforcement, Psychology; Self Administration

Opioid users experience increased incidence of infection, which may be partially attributable to both direct opiate-immune interactions and conditioned immune responses. Previous studies have investigated the neural circuitry governing opioid conditioned immune responses, but work remains to elucidate the mechanisms mediating this effect. Our laboratory has previously shown that hippocampal IL-1 signaling, specifically, is required for the expression of heroin conditioned immunosuppression following learning. The current studies were designed to further characterize the role of hippocampal IL-1 in this phenomenon by manipulating IL-1 during learning. Experiment 1 tested whether hippocampal IL-1 is also required for the acquisition of heroin conditioned immunosuppression, while Experiment 2 tested whether hippocampal IL-1 is required for the expression of unconditioned heroin immunosuppression. We found that blocking IL-1 signaling in the dorsal hippocampus with IL-1RA during each conditioning session, but not on interspersed non-conditioning days, significantly attenuated the acquisition of heroin conditioned immunosuppression. Strikingly, we found that the same IL-1RA treatment did not alter unconditioned immunosuppression to a single dose of heroin. Thus, IL-1 signaling is not a critical component of the response to heroin but rather may play a role in the formation of the association between heroin and the context. Collectively, these studies suggest that IL-1 signaling, in addition to being involved in the expression of a heroin conditioned immune response, is also involved in the acquisition of this effect. Importantly, this effect is likely not due to blocking the response to the unconditioned stimulus since IL-1RA did not affect heroin's immunosuppressive effects.

Topics: Animals; Behavior, Animal; Conditioning, Psychological; Disease Models, Animal; Heroin; Hippocampus; Immunosuppression Therapy; Interleukin 1 Receptor Antagonist Protein; Interleukin-1; Male; Narcotics; Rats; Rats, Inbred Lew; Signal Transduction

Autism susceptibility candidate 2 (AUTS2) is a gene associated with autism and mental retardation. Recent studies have suggested an association of the AUTS2 gene with heroin dependence, and reduced AUTS2 gene expression may confer increased susceptibility to heroin dependence. However, the functional role of the AUTS2 protein in regulating enduring neuroadaptations in response to heroin exposure has not been established. Here, we investigated the effects of acute and chronic heroin exposure on AUTS2 mRNA and protein expression in the nucleus accumbens (NAc) and caudate-putamen (CPu) to determine whether changes in AUTS2 expression are associated with heroin-induced locomotor sensitization in mice. Moreover, we explored whether AUST2 knockdown affects heroin-induced locomotor sensitization. AUTS2 mRNA and protein expression in the NAc, but not the CPu, was decreased after chronic heroin (1mg/kg) administration. In the NAc, the expression of heroin-induced locomotor sensitization was enhanced through the lentiviral-AUTS2-shRNA-mediated knockdown of AUTS2, while the overexpression of AUTS2 attenuated the locomotor-stimulant effects of heroin. Together, these results indicate that AUTS2 in the NAc, but not the CPu, suppresses the initiation and expression of heroin-induced behavioral sensitization, suggesting that AUST2 may be a potential target for the treatment of heroin dependence.

Topics: Animals; Caudate Nucleus; Cytoskeletal Proteins; Disease Models, Animal; Gene Knockdown Techniques; Heroin; Heroin Dependence; Male; Mice, Inbred C57BL; Motor Activity; Narcotics; Neuropeptides; Nuclear Proteins; Nucleus Accumbens; Putamen; rac1 GTP-Binding Protein; RNA, Messenger; Transcription Factors

The inability to maintain drug abstinence is often referred to as relapse and consists of a process by which an abstaining individual slips back into old behavioral patterns and substance use. Animal models of relapse have been developed and validated over the last decades, and significantly contributed to shed light on the neurobiological mechanisms underlying vulnerability to relapse. The most common procedure to study drug-seeking and relapse-like behavior in animals is the "reinstatement model." Originally elaborated by Pavlov and Skinner, the concepts of reinforced operant responding and conditioned behavior were applied to addiction research not before 1971 (Stretch et al., Can J Physiol Pharmacol 49:581-589, 1971), and the first report of a reinstatement animal model as it is now used worldwide was published only 10 years later (De Wit and Stewart, Psychopharmacology 75:134-143, 1981). According to the proposed model, opioids are typically self-administered intravenously, as humans do, and although rodents are most often employed in these studies, this model has been used with a variety of species including nonhuman primates, dogs, cats, and pigeons. A variety of operant responses are available, depending on the species studied. For example, a lever press or a nose poke response typically is used for rodents, whereas a panel press response typically is used for nonhuman primates. Here, we describe a simple and easily reproducible protocol of heroin-seeking reinstatement in rats, which proved useful to study the neurobiological mechanisms underlying relapse to heroin and vulnerability factors enhancing the resumption of heroin-seeking behavior.

Topics: Analgesics, Opioid; Animals; Behavior, Addictive; Cocaine; Conditioning, Operant; Disease Models, Animal; Heroin; Humans; Opioid-Related Disorders; Rats; Receptors, Opioid; Substance-Related Disorders

Mu-opioid receptors (MOPRs) are the target of heroin and other prescription opioids, which are currently responsible for massive addiction morbidity in the US. The gene coding for the human MOPR (OPRM1) has an important functional single nucleotide polymorphism (SNP), A118G. The OPRM1 A118G genotype results in substantially increased risk of heroin addiction in humans; however, the neurobiological mechanism for this increased risk is not fully understood. This study examined heroin self-administration (SA) behavior in A112G (G/G) mice, harboring a functionally equivalent SNP in Oprm1 with a similar amino acid substitution, in extended (4 h) SA sessions. Adult male and female G/G mice and 'wild-type' litter mates (A/A) were allowed to self-administer heroin (0.25 mg/kg/unit dose, FR1 with a nose poke response) for 4 h/day, for 10 consecutive days. Half of the mice then continued in a heroin dose-response study, while extinction from heroin SA was studied in the other half. In vivo microdialysis was used to measure acute heroin-induced increases of striatal dopamine in the GG vs AA genotypes. Male and female G/G mice responded for heroin significantly more (and thus had greater intake) than A/A mice, in the initial 10 days of heroin SA, and in the subsequent dose-response study. There were no significant differences in extinction of SA between the A/A and G/G mice. Heroin-induced increases in striatal dopamine levels are higher in the GG mice than in the AA mice. Both male and female G/G mice self-administered more heroin than did A/A mice over a 10-day period, possibly because of the greater increases of heroin-induced striatal dopamine in the GG mice. Furthermore, G/G male mice escalated the amount of heroin self-administration across 10 extended-access sessions more than A/A male mice did. These are the first studies to examine the acquisition of heroin SA in this mouse model. These studies may lead to a better understanding of the neurobiological and behavioral mechanisms that underlie greater risk of heroin addiction in carriers of the A118G SNP.

Topics: Animals; Catheters, Indwelling; Corpus Striatum; Disease Models, Animal; Dopamine; Dose-Response Relationship, Drug; Drug-Seeking Behavior; Female; Heroin; Heroin Dependence; Male; Mice, Transgenic; Microdialysis; Narcotics; Polymorphism, Single Nucleotide; Receptors, Opioid, mu; Self Administration

The hypocretin/orexin (HCRT) system has been associated with both positive and negative drug reinforcement, implicating HCRT receptor 1 (HCRT-R1) signaling in drug-related behaviors for all major drug classes, including opioids. However, to date there are limited studies investigating the role of HCRT receptor 2 (HCRT-R2) signaling in compulsive-like drug seeking. Escalation of drug intake with extended access has been suggested to model the transition from controlled drug use to compulsive-like drug seeking/taking. The current study examined the effects of a HCRT-R2 antagonist, NBI-80713, on heroin self-administration in rats allowed short- (1 h; ShA) or long- (12 h; LgA) access to intravenous heroin self-administration. Results indicate that systemically administered NBI-80713 dose-dependently decreased heroin self-administration in LgA, but not in ShA, animals. Quantitative PCR analyses showed an increase in Hcrtr2 mRNA levels in the central amygdala, a stress-related brain region, of LgA rats. These observations suggest a functional role for HCRT-R2 signaling in compulsive-like heroin self-administration associated with extended access and indicate HCRT-R2 antagonism as a potential pharmacological target for the treatment of heroin dependence.

Topics: Animals; Central Amygdaloid Nucleus; Disease Models, Animal; Dose-Response Relationship, Drug; Drinking Behavior; Drug-Seeking Behavior; Feeding Behavior; Heroin; Heroin Dependence; Locomotion; Male; Narcotics; Orexin Receptor Antagonists; Orexin Receptors; Rats, Wistar; RNA, Messenger; Self Administration; Substance Withdrawal Syndrome; Time Factors

Cocaine abuse in HIV patients accelerates the progression and severity of neuropathology, motor impairment and cognitive dysfunction compared to non-drug using HIV patients. Cocaine and HIV interact with the dopamine transporter (DAT); however, the effect of their interaction on DAT binding remains understudied. The present study compared the dose-response functions for intravenous self-administration of cocaine and heroin between male HIV-1 transgenic (HIV-1 Tg) and Fischer 344 rats. The cocaine and heroin dose-response functions exhibit an inverted U-shape for both HIV-1 Tg and F344 rats. For cocaine, the number of infusions for each dose on the ascending limb was greater for HIV-1 Tg versus F344 rats. No significant changes in the heroin dose-response function were observed in HIV-1 Tg animals. Following the conclusion of self-administration experiments, DAT binding was assessed in striatal membranes. Saturation binding of the cocaine analog [(125)I] 3β-(4-iodophenyl)tropan-2β-carboxylic acid methyl ester ([(125)I]RTI-55) in rat striatal membranes resulted in binding curves that were best fit to a two-site binding model, allowing for calculation of dissociation constant (Kd) and binding density (Bmax) values that correspond to high- and low-affinity DAT binding sites. Control HIV-1 Tg rats exhibited a significantly greater affinity (i.e., decrease in Kd value) in the low-affinity DAT binding site compared to control F344 rats. Furthermore, cocaine self-administration in HIV-1 Tg rats increased low-affinity Kd (i.e., decreased affinity) compared to levels observed in control F344 rats. Cocaine also increased low-affinity Bmax in HIV-1 Tg rats as compared to controls, indicating an increase in the number of low-affinity DAT binding sites. F344 rats did not exhibit any change in high- or low-affinity Kd or Bmax values following cocaine or heroin self-administration. The increase in DAT affinity in cocaine HIV-1 Tg rats is consistent with the leftward shift of the ascending limb of the cocaine dose-response curve observed in HIV-1 Tg vs. F344 rats, and has major implications for the function of cocaine binding to DAT in HIV patients. The absence of HIV-related changes in heroin intake are likely due to less dopaminergic involvement in the mediation of heroin reward, further emphasizing the preferential influence of HIV on dopamine-related behaviors.

Topics: Animals; Behavior, Animal; Cocaine; Disease Models, Animal; Dopamine Plasma Membrane Transport Proteins; Dopamine Uptake Inhibitors; Dose-Response Relationship, Drug; Heroin; HIV Infections; Male; Narcotics; Neostriatum; Protein Binding; Rats; Rats, Inbred F344; Rats, Transgenic; Self Administration

Memory processes may be involved in the transition from drug lapses to relapse. This study explored the role of noradrenaline (NA) in reacquisition of place preference, an animal model of relapse that involves the updating of memories about drugs and associated stimuli. Experiments involved 7 phases: habituation, conditioning (1 mg/kg heroin and vehicle; 4 pairings each), test of conditioning (Test I), extinction (vehicle and vehicle; 4 pairings each), test of extinction (Test II), reconditioning (1 mg/kg heroin and vehicle; 1 re-pairing each), and test of reconditioning (Test III). To target memory stabilization processes, various treatments were administered post-reconditioning: systemic clonidine (0, 10, 40, 100 μg/kg; α2 adrenergic receptor agonist); intra-locus coeruleus (LC) clonidine (0, 4.5, 18 nmol); and intra-basolateral amygdala (BLA) propranolol/prazosin (0, 34/2.4 nmol; β and α1 adrenergic receptor antagonists, respectively). The effect of post-reconditioning systemic clonidine on BLA c-fos expression was also assessed. It was found that systemic clonidine dose-dependently blocked heroin reacquisition when given immediately or 4 h post-reconditioning, but not 8 h later or 4 h prior to Test III. Similar effects were observed following intra-LC clonidine infusions. Post-reconditioning systemic clonidine also blocked reacquisition of cocaine place preference (20 mg/kg). Finally, BLA c-fos expression was reduced by clonidine, and blockade of BLA β and α1 receptors prevented heroin reacquisition. These findings in rats support the hypothesis that relapse involves memory stabilization processes that can be disrupted by suppression of central NA activity.

Topics: Adrenergic alpha-1 Receptor Antagonists; Adrenergic alpha-2 Receptor Agonists; Animals; Basolateral Nuclear Complex; Clonidine; Cocaine; Conditioning, Psychological; Disease Models, Animal; Dopamine Uptake Inhibitors; Dose-Response Relationship, Drug; Heroin; Locus Coeruleus; Male; Memory; Narcotics; Norepinephrine; Prazosin; Propranolol; Rats, Sprague-Dawley; Spatial Behavior; Substance-Related Disorders

Pain management in opioid abusers engenders ethical and practical difficulties for clinicians, often resulting in pain mismanagement. Although chronic opioid administration may alter pain states, the presence of pain itself may alter the propensity to self-administer opioids, and previous history of drug abuse comorbid with chronic pain promotes higher rates of opioid misuse. Here, we tested the hypothesis that inflammatory pain leads to increased heroin self-administration resulting from altered mu opioid receptor (MOR) regulation of mesolimbic dopamine (DA) transmission. To this end, the complete Freund's adjuvant (CFA) model of inflammation was used to assess the neurochemical and functional changes induced by inflammatory pain on MOR-mediated mesolimbic DA transmission and on rat intravenous heroin self-administration under fixed ratio (FR) and progressive ratio (PR) schedules of reinforcement. In the presence of inflammatory pain, heroin intake under an FR schedule was increased for high, but attenuated for low, heroin doses with concomitant alterations in mesolimbic MOR function suggested by DA microdialysis. Consistent with the reduction in low dose FR heroin self-administration, inflammatory pain reduced motivation for a low dose of heroin, as measured by responding under a PR schedule of reinforcement, an effect dissociable from high heroin dose PR responding. Together, these results identify a connection between inflammatory pain and loss of MOR function in the mesolimbic dopaminergic pathway that increases intake of high doses of heroin. These findings suggest that pain-induced loss of MOR function in the mesolimbic pathway may promote opioid dose escalation and contribute to opioid abuse-associated phenotypes.. This study provides critical new insights that show that inflammatory pain alters heroin intake through a desensitization of MORs located within the VTA. These findings expand our knowledge of the interactions between inflammatory pain and opioid abuse liability, and should help to facilitate the development of novel and safer opioid-based strategies for treating chronic pain.

Topics: Action Potentials; Analgesics, Opioid; Animals; Conditioning, Operant; Disease Models, Animal; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Excitatory Amino Acid Antagonists; Glycine Agents; Heroin; Hyperalgesia; Inflammation; Inhibitory Postsynaptic Potentials; Male; Neurons; Pain; Pain Threshold; Quinoxalines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, mu; Strychnine; Sucrose; Ventral Tegmental Area

Because the role of dopamine (DA) D3 receptors has been investigated primarily in relation to cocaine-related behaviors little is known of the role of these receptors in heroin seeking.. To investigate the effect of the selective DA D3 receptor antagonist, SR 21502, on cue-induced reinstatement of heroin seeking and heroin conditioned place preference (CPP).. In experiment 1, rats were trained to self-administer intravenous heroin for 15 days followed by extinction. Following extinction animals were treated with one of several SR 21502 doses (0, 7.5, 10 or 15mg/kg) and a cue-induced reinstatement test was conducted. In experiment 2, animals were conditioned to experience heroin in one compartment of a CPP apparatus and saline in the other. On the test day animals were treated with 0, 3.75, 7.5, 10 or 15mg/kg of SR 21502 and tested for their CPP.. The results from experiment 1 showed a significant dose-related reduction in cue-induced reinstatement of active lever pressing in the 7.5 and 10mg groups and an absence of the reinstatement effect in the 15mg group. In experiment 2, animals treated with vehicle or 3.75mg of SR 21502 showed significant heroin place preferences but those treated with the higher doses showed no CPP.. Our findings suggest that DA D3 receptors play a significant role in heroin approach behaviors driven by conditioned stimuli. As such, we propose that SR 21502 holds potential as an effective pharmacotherapeutic agent for relapse prevention and should be studied further.

Topics: Animals; Conditioning, Classical; Cues; Disease Models, Animal; Dose-Response Relationship, Drug; Extinction, Psychological; Female; Heroin; Heroin Dependence; Imidazoles; Male; Pyridines; Rats; Rats, Long-Evans; Receptors, Dopamine D3; Recurrence; Self Administration; Substance Abuse, Intravenous

Reducing the enduring vulnerability to relapse is a therapeutic goal in treating drug addiction. Studies with animal models of drug addiction show a marked increase in extrasynaptic glutamate in the core subcompartment of the nucleus accumbens (NAcore) during reinstated drug seeking. However, the synaptic mechanisms linking drug-induced changes in extrasynaptic glutamate to relapse are poorly understood. Here, we discovered impaired glutamate elimination in rats extinguished from heroin self-administration that leads to spillover of synaptically released glutamate into the nonsynaptic extracellular space in NAcore and investigated whether restoration of glutamate transport prevented reinstated heroin seeking. Through multiple functional assays of glutamate uptake and analyzing NMDA receptor-mediated currents, we show that heroin self-administration produced long-lasting downregulation of glutamate uptake and surface expression of the transporter GLT-1. This downregulation was associated with spillover of synaptic glutamate to extrasynaptic NMDA receptors within the NAcore. Ceftriaxone restored glutamate uptake and prevented synaptic glutamate spillover and cue-induced heroin seeking. Ceftriaxone-induced inhibition of reinstated heroin seeking was blocked by morpholino-antisense targeting GLT-1 synthesis. These data reveal that the synaptic glutamate spillover in the NAcore results from reduced glutamate transport and is a critical pathophysiological mechanism underling reinstated drug seeking in rats extinguished from heroin self-administration.

Topics: Animals; Aspartic Acid; Ceftriaxone; Conditioning, Operant; Disease Models, Animal; Down-Regulation; Drug-Seeking Behavior; Excitatory Postsynaptic Potentials; Glutamic Acid; Heroin; Heroin Dependence; In Vitro Techniques; Male; Morpholinos; Neurons; Nucleus Accumbens; Potassium; Rats; Rats, Sprague-Dawley; Secondary Prevention; Synapses

Addiction is a chronic disorder involving recurring intoxication, withdrawal, and craving episodes. Escaping this vicious cycle requires maintenance of abstinence for extended periods of time and is a true challenge for addicted individuals. The emergence of depressive symptoms, including social withdrawal, is considered a main cause for relapse, but underlying mechanisms are poorly understood. Here we establish a mouse model of protracted abstinence to heroin, a major abused opiate, where both emotional and working memory deficits unfold. We show that delta and kappa opioid receptor (DOR and KOR, respectively) knockout mice develop either stronger or reduced emotional disruption during heroin abstinence, establishing DOR and KOR activities as protective and vulnerability factors, respectively, that regulate the severity of abstinence. Further, we found that chronic treatment with the antidepressant drug fluoxetine prevents emergence of low sociability, with no impact on the working memory deficit, implicating serotonergic mechanisms predominantly in emotional aspects of abstinence symptoms. Finally, targeting the main serotonergic brain structure, we show that gene knockout of mu opioid receptors (MORs) in the dorsal raphe nucleus (DRN) before heroin exposure abolishes the development of social withdrawal. This is the first result demonstrating that intermittent chronic MOR activation at the level of DRN represents an essential mechanism contributing to low sociability during protracted heroin abstinence. Altogether, our findings reveal crucial and distinct roles for all three opioid receptors in the development of emotional alterations that follow a history of heroin exposure and open the way towards understanding opioid system-mediated serotonin homeostasis in heroin abuse.

Topics: Animals; Antidepressive Agents, Second-Generation; Depression; Disease Models, Animal; Dorsal Raphe Nucleus; Fluoxetine; Heroin; Heroin Dependence; Male; Memory Disorders; Memory, Short-Term; Mice, 129 Strain; Mice, Inbred C57BL; Mice, Knockout; Narcotics; Receptors, Opioid, kappa; Receptors, Opioid, mu; Social Behavior; Spatial Memory; Substance Withdrawal Syndrome

Drug administration to avoid unpleasant drug withdrawal symptoms has been hypothesized to be a crucial factor that leads to compulsive drug-taking behavior. However, the neural relationship between the aversive motivational state produced by drug withdrawal and the development of the drug-dependent state still remains elusive. It has been observed that chronic exposure to drugs of abuse increases brain-derived neurotrophic factor (BDNF) levels in ventral tegmental area (VTA) neurons. In particular, BDNF expression is dramatically increased during drug withdrawal, which would suggest a direct connection between the aversive state of withdrawal and BDNF-induced neuronal plasticity. Using lentivirus-mediated gene transfer to locally knock down the expression of the BDNF receptor tropomyosin-receptor-kinase type B in rats and mice, we observed that chronic opiate administration activates BDNF-related neuronal plasticity in the VTA that is necessary for both the establishment of an opiate-dependent state and aversive withdrawal motivation. Our findings highlight the importance of a bivalent, plastic mechanism that drives the negative reinforcement underlying addiction.

Topics: Animals; Brain-Derived Neurotrophic Factor; Disease Models, Animal; Gene Expression Regulation; Glutamate Decarboxylase; Heroin; In Vitro Techniques; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Narcotics; Opioid-Related Disorders; Rats; Rats, Wistar; Signal Transduction; Substance Withdrawal Syndrome; Ventral Tegmental Area

Drug abuse is associated with epigenetic changes, such as histone modifications and DNA methylation. The purpose of the present study was to examine the effect of chronic cocaine and heroin administration on global DNA methylation in brain and liver. Male, 8 week old, C57BL/6J mice received heroin in a chronic 'intermittent' escalating dose paradigm, or cocaine in a chronic escalating dose 'binge' paradigm, which mimic the human pattern of opioid or cocaine abuse respectively. Following sacrifice, livers and brains were removed and DNA was extracted from them. The extracted DNA was hydrolyzed and 2'-deoxycytidine and 5-methyl-2'-deoxycytidine were determined by HPLC-UV. The % 5-methyl-2'-deoxycytidine content of DNA was significantly higher in the brain compared to the liver. There were no differences between the control animals and the cocaine or heroin treated animals in neither of the tissues examined, which is surprising since cocaine administration induced gross morphological changes in the liver. Moreover, there was no difference in the % 5-methyl-2'-deoxycytidine content of DNA between the cocaine and the heroin treated animals. The global DNA methylation status in the brain and liver of mice chronically treated with cocaine or heroin remains unaffected, but this finding cannot exclude the existence of anatomical region or gene-specific methylation differences. This is the first time that global DNA methylation in the liver and whole brain has been studied following chronic cocaine or heroin treatment.

Topics: Animals; Biomarkers; Brain; Chromatography, High Pressure Liquid; Cocaine; Cocaine-Related Disorders; Deoxycytidine; Disease Models, Animal; DNA Methylation; Heroin; Heroin Dependence; Liver; Male; Mice; Mice, Inbred C57BL; Spectrophotometry, Ultraviolet; Time Factors

Anxiety is one of the early symptoms of opioid withdrawal and contributes to continued drug use and relapse. The acoustic startle response (ASR) is a component of anxiety that has been shown to increase during opioid withdrawal in both humans and animals. We investigated the role of corticotropin-releasing factor (CRF) and norepinephrine (NE), two key mediators of the brain stress system, on acute heroin withdrawal-potentiated ASR. Rats injected with heroin (2 mg/kg s.c.) displayed an increased ASR when tested 4 h after heroin treatment. A similar increase in ASR was found in rats 10-20 h into withdrawal from extended access (12 h) to i.v. heroin self-administration, a model that captures several aspects of heroin addiction in humans. Both the α 2 adrenergic receptor agonist clonidine (10 μg/kg s.c.) and CRF1 receptor antagonist N,N-bis(2-methoxyethyl)-3-(4-methoxy-2-methylphenyl)-2,5-dimethyl-pyrazolo[1,5-a] pyrimidin-7-amine (MPZP; 20 mg/kg s.c.) blocked heroin withdrawal-potentiated startle. To investigate the relationship between CRF1 and α 2 adrenergic receptors in the potentiation of the ASR, we tested the effect of MPZP on yohimbine (1.25 mg/kg s.c.)-potentiated startle and clonidine on CRF (2 μg i.c.v.)-potentiated startle. Clonidine blocked CRF-potentiated startle, whereas MPZP partially attenuated but did not reverse yohimbine-potentiated startle, suggesting that CRF may drive NE release to potentiate startle. These results suggest that CRF1 and α 2 receptors play an important role in the heightened anxiety-like behaviour observed during acute withdrawal from heroin, possibly via CRF inducing the release of NE in stress-related brain regions.

Topics: Acoustic Stimulation; Adrenergic alpha-2 Receptor Agonists; Adrenergic alpha-2 Receptor Antagonists; Analysis of Variance; Animals; Clonidine; Conditioning, Operant; Corticotropin-Releasing Hormone; Disease Models, Animal; Heroin; Male; Narcotics; Norepinephrine; Psychoacoustics; Pyrimidines; Rats; Rats, Wistar; Receptors, Adrenergic, alpha-2; Reflex, Startle; Self Administration; Substance Withdrawal Syndrome; Time Factors; Yohimbine

Most animal research on drug relapse involves the reinstatement model where abstinence is a result of drug removal (extinction). However, abstinence in humans often results from the aversive consequences that accompany drug seeking (conflict situation). This study was aimed at using a conflict-based animal model of abstinence/relapse in rats self-administering heroin or cocaine.. Rats were trained to self-administer heroin (0.05 mg kg(-1) injection(-1)) or cocaine (0.5 mg kg(-1) injection(-1)) with each injection paired with a light cue. After stable responding was demonstrated, the floor near the levers was electrified, creating a barrier, in order to model the negative consequences of continued drug seeking. Shock intensities were increased over sessions until no responses occurred for three consecutive sessions. During a relapse test, where shock was maintained,the capacity of noncontingent drug cue presentations to induce active lever pressing was assessed.. Ten of ten heroin animals and three of eight cocaine animals exposed to noncontingent cue presentations resumed responding. During the relapse test, for both drug groups, active lever pressing was significantly higher than during abstinence but only in the heroin group was it significantly higher than inactive lever pressing.. The implementation of negative consequences for drug seeking can result in its cessation just as they might in human addicts. Similarly, exposure to drug cues can lead to resumption of drug seeking. This model may be useful for studying the mechanisms underlying abstinence and relapse and for developing strategies to prevent relapse.

Topics: Animals; Cocaine; Cocaine-Related Disorders; Conflict, Psychological; Cues; Disease Models, Animal; Electroshock; Extinction, Psychological; Heroin; Heroin Dependence; Male; Rats; Rats, Long-Evans; Recurrence; Self Administration

Previous research with an animal model of relapse has shown that acute food deprivation will reinstate extinguished drug seeking. Recent evidence with humans, however, suggests that chronic food restriction rather than acute food deprivation is related to increases in drug taking and relapse, emphasizing a need for an animal model to elucidate the neural mechanisms mediating the effects of chronic food restriction on drug seeking. Here we studied the effects of chronic food restriction during a period of abstinence on heroin seeking in rats.. Rats were trained to self-administer heroin over 10 days (0.1 mg/kg/infusion; i.v.). Rats were then removed from the operant conditioning chambers and exposed to a mild food restriction (resulting in 10-15 % decrease in body weight) or given unrestricted access to food for 14 days while abstinent. The abstinence period was followed by a drug-seeking test under extinction conditions. Subsequent experiments manipulated the length of restriction and test conditions.. Rats that were food restricted throughout the abstinence period demonstrated a robust increase in cue-induced heroin seeking compared to sated rats. Re-feeding prior to testing or decreasing the length of the food restriction period prevented the augmentation of drug seeking.. A combination of chronic food restriction and a concurrent state of hunger appears to be necessary for an increase in cue-induced heroin seeking following abstinence. The procedure presented here may serve as a useful model to study the increased risk for relapse following dietary manipulations in abstinent subjects.

Topics: Animals; Behavior, Addictive; Conditioning, Operant; Cues; Disease Models, Animal; Eating; Food Deprivation; Heroin; Heroin Dependence; Hunger; Male; Rats; Rats, Long-Evans; Recurrence; Self Administration; Time Factors

In humans, hyperalgesia, tolerance and anxiety disorders are common symptoms during heroin withdrawal syndrome. Significant evidence supports a role of NMDA receptors in these phenomena. Because polyamines may positively modulate the functioning of NMDA receptors and mainly originate from dietary intake, one hypothesis is that a polyamine deficient diet (PD diet) may reduce withdrawal symptoms. To address this question, we investigated the ability of a PD diet to prevent or to alleviate some symptoms of withdrawal syndrome as hyperalgesia, and increased anxiety-like behaviour in rats receiving 14 once daily subcutaneous heroin injections. Here, we show that a PD diet has both preventive and curative properties for reducing certain signs of withdrawal such as hyperalgesia, tolerance and increased anxiety-like behaviour observed in rats fed with a standard diet. Moreover, in heroin-withdrawn rats which were returned to basal pain sensitivity level, hyperalgesia following acute analgesia induced by a single heroin dose was observed in heroin-treated rats fed with standard diet, not in rats fed with a PD diet. Similarly, a stress-induced hyperalgesia induced by a non-nociceptive environmental stress session was observed in heroin-treated rats fed with standard diet. In contrast, a stress-induced analgesia was observed in heroin-treated rats fed with a PD diet, as it was observed in non heroin-treated rats. Since a PD diet for several weeks did not induce appreciable side-effects in rats, these preclinical results suggest that a PD diet could be an effective strategy for improving the relief of certain negative emotional states of heroin withdrawal syndrome and to allow reducing other medications generally used, such as opioid maintenance drugs.

Topics: Analgesics, Opioid; Animals; Anxiety; Diet; Disease Models, Animal; Drug Tolerance; Heroin; Hyperalgesia; Male; Maze Learning; Memory, Short-Term; Motor Activity; Pain Measurement; Polyamines; Rats; Rats, Sprague-Dawley; Substance Withdrawal Syndrome

The aim of the present study was to investigate the effects of pretreatment with risperidone on heroin self-administration and heroin-seeking behaviour induced by cues and heroin priming. Rats were trained to self-administer heroin under a fixed ratio 1 schedule for 2 wk and nose-poke responding was extinguished for 10 d, after which reinstatement of drug seeking was induced by conditioned cues or heroin priming. Acute risperidone administration at doses 10-100 μg/kg potently and dose-dependently inhibited reinstatement of conditioned cue-induced heroin seeking; the minimum dose of inhibition was 30 μg/kg. In contrast, risperidone at the same doses did not attenuate reinstatement induced by two priming doses of heroin (100 or 250 μg/kg s.c.). Risperidone at these doses failed to alter heroin self-administration and locomotion activity. These data demonstrate that acute treatment with low-dose risperidone inhibits conditioned cue-induced heroin seeking and risperidone may be an adjunctive therapy for the treatment of heroin addiction.

Topics: Analgesics, Opioid; Animals; Conditioning, Operant; Cues; Disease Models, Animal; Dopamine Antagonists; Dose-Response Relationship, Drug; Drug-Seeking Behavior; Extinction, Psychological; Heroin; Heroin Dependence; Male; Rats; Rats, Sprague-Dawley; Reinforcement, Psychology; Risperidone; Secondary Prevention; Self Administration

Currently, there are no existing procedures that model in animals the situation where exposure to prolonged mild food restriction results in relapse to drug abuse. Here, reinstatement of extinguished heroin-seeking behavior was assessed in rats under extinction conditions. Ten, but not 7, days of food restriction (∼80% of sated body weight) induced reinstatement of heroin seeking, over and above the spontaneous recovery of the behavior. It is suggested that chronic, mild, food restriction following extinction of drug seeking behavior might serve as a useful model to study the increased risk for relapse to drug abuse due to dietary challenges.

Topics: Animals; Conditioning, Psychological; Disease Models, Animal; Drug-Seeking Behavior; Extinction, Psychological; Food Deprivation; Heroin; Heroin Dependence; Male; Narcotics; Rats; Recurrence; Self Administration; Time Factors

Although high anxiety is commonly associated with drug addiction, its causal role in this disorder is unclear.. In light of strong evidence for dissociable neural mechanisms underlying heroin and cocaine addiction, the present study investigated whether high anxiety predicts the propensity of rats to lose control over intravenous cocaine or heroin self-administration.. Sixty-four rats were assessed for anxiety in the elevated plus-maze, prior to extended access to intravenous cocaine or heroin self-administration.. High-anxious rats, identified in the lower quartile of the population, showed a greater escalation of cocaine, but not heroin, self-administration compared with low-anxious rats selected in the upper quartile of the population. Anxiety scores were also positively correlated with the extent of escalation of cocaine self-administration.. The present data suggest that high anxiety predisposes rats to lose control over cocaine-but not heroin-intake. High anxiety may therefore be a vulnerability trait for the escalation of stimulant but not opiate self-administration.

Topics: Animals; Anxiety; Cocaine; Disease Models, Animal; Heroin; Male; Maze Learning; Rats; Self Administration; Substance-Related Disorders

Once dependent on alcohol or opioids, negative affect may accompany withdrawal. Dependent individuals are hypothesized to "self-medicate" in order to cope with withdrawal, which promotes escalated alcohol and drug use.. The current study aimed to develop a reliable animal model to assess symptoms that occur during spontaneous alcohol and opioid withdrawal.. Dependence was induced using intermittent alcohol exposure or pulsatile heroin delivery and assessed for the presence of withdrawal symptoms during acute withdrawal by measuring somatic signs, behavior in the forced swim test (FST), and air-puff-induced 22-kHz ultrasonic vocalizations (USVs). Additional animals subjected to 8 weeks of alcohol vapor exposure were evaluated for altered somatic signs, operant alcohol self-administration, and 22-kHz USV production, as well as performance in the elevated plus maze (EPM).. During spontaneous withdrawal from pulsatile heroin or intermittent alcohol vapor, animals displayed increased somatic withdrawal signs, FST immobility, and 22-kHz USV production but did not show any behavioral change in the EPM unless the duration of alcohol exposure was extended to 4 weeks. Following 8 weeks of alcohol vapor exposure, animals displayed somatic withdrawal signs, escalated alcohol self-administration, and increased 22-kHz USVs.. These paradigms provide consistent methods to evaluate the behavioral ramifications, and neurobiological substrates, of alcohol and opioid dependence during spontaneous withdrawal. As immobility in the FST and percent open-arm time in the EPM were dissociable, with 22-kHz USVs paralleling immobility in the FST, assessment of air-puff-induced 22-kHz USVs could provide an ethologically valid alternative to the FST.

Topics: Affect; Alcoholism; Animals; Conditioning, Operant; Disease Models, Animal; Ethanol; Heroin; Heroin Dependence; Male; Maze Learning; Rats; Rats, Wistar; Self Administration; Substance Withdrawal Syndrome; Swimming; Time Factors; Vocalization, Animal

In a rat model of context-induced relapse to heroin, we identified sparsely distributed ventral medial prefrontal cortex (mPFC) neurons that were activated by the heroin-associated context. Selective pharmacogenetic inactivation of these neurons inhibited context-induced drug relapse. A small subset of ventral mPFC neurons formed neuronal ensembles that encode the learned associations between heroin reward and heroin-associated contexts; re-activation of these neuronal ensembles by drug-associated contexts during abstinence provoked drug relapse.

Topics: Analgesics, Opioid; Animals; Disease Models, Animal; Heroin; Heroin Dependence; Nerve Net; Neurons; Prefrontal Cortex; Rats; Secondary Prevention; Substance Withdrawal Syndrome

The prevalence of opioid abuse and dependence has been on the rise in just the past few years. Animal studies indicate that extended access to heroin produces escalation of intake over time, whereas stable intake is observed under limited-access conditions. Escalation of drug intake has been suggested to model the transition from controlled drug use to compulsive drug seeking and taking. Here, we directly compared the pattern of heroin intake in animals with varying periods of heroin access. Food intake was also monitored over the course of escalation. Rats were allowed to lever press on a fixed-ratio 1 schedule of reinforcement to receive intravenous infusions of heroin for 1, 6, 12, or 23h per day for 14 sessions. The results showed that heroin intake in the 12 and 23h groups markedly increased over time, whereas heroin intake in the 1h group was stable. The 6h group showed a significant but modest escalation of intake. Total heroin intake was similar in the 12 and 23h groups, but the rate of heroin self-administration was two-fold higher in the 12h group compared with the 23h group. Food intake decreased over sessions only in the 12h group. The 12 and 23h groups showed marked physical signs of naloxone-precipitated withdrawal. These findings suggest that 12h heroin access per day may be the optimal access time for producing escalation of heroin intake. The advantages of this model and the potential relevance for studying drug addiction are discussed.

Topics: Animals; Behavior, Animal; Disease Models, Animal; Drug-Seeking Behavior; Heroin; Heroin Dependence; Humans; Male; Naloxone; Rats; Rats, Wistar; Self Administration; Substance Withdrawal Syndrome; Time Factors

The present investigations sought to determine whether the ventral tegmental area (VTA), basolateral amygdala (BLA), and nucleus accumbens shell (NAC) comprise a circuitry that mediates heroin-induced conditioned immunomodulation. Rats were given conditioning trials in which they received an injection of heroin upon placement into a distinctive environment. Prior to testing, rats received unilateral intra-BLA microinfusion of a D(1) antagonist concomitantly with unilateral intra-NAC shell microinfusion of an NMDA antagonist. Disconnection of the VTA-BLA-NAC circuit impaired the ability of the heroin-paired environment to suppress lipopolysaccharide-induced immune responses, defining for the first time a specific neural circuit involved in conditioned neural-immune interactions.

Topics: Amygdala; Analgesics, Opioid; Animals; Conditioning, Psychological; Disease Models, Animal; Heroin; Heroin Dependence; Immunomodulation; Male; Neural Pathways; Nucleus Accumbens; Rats; Rats, Inbred Lew; Ventral Tegmental Area

Heroin has been shown to cause spongiform leukoencephalopathy (SLE) in heroin addicts. In this study, we found that heroin could induce apoptosis of primary cultured cerebellar granule cells (CGC) and c-Jun N-terminal kinase (JNK) pathway is activated during CGCs apoptosis. Inhibiting JNK with a specific inhibitor, SP600125, reduced the levels of c-Jun phosphorylation and caspase-3 activation. We also showed that use the JNK inhibitor SP600125, caspase inhibitor z-VAD, or use SP600125 and z-VAD together significantly suppressed cell death induced by heroin. These results indicate that JNK pathway is an important mediator of the neurotoxic effects of heroin and inhibiting JNK activity may represent a new and effective strategy to treat heroin-induced SLE.

Topics: Animals; Animals, Newborn; Apoptosis; Caspase 3; Caspase Inhibitors; Cerebellum; Cytoplasmic Granules; Disease Models, Animal; Enzyme Activation; Heroin; Heroin Dependence; MAP Kinase Signaling System; Mitogen-Activated Protein Kinase 8; Narcotics; Neurons; Primary Cell Culture; Rats; Rats, Sprague-Dawley

Heroin use has seriously threatened public heath in many countries, but the existing therapies continue to have many limitations. Recently, immunotherapy has shown efficacy in some clinical studies, including vaccines against nicotine and cocaine, but no opioid vaccines have been introduced in clinical studies. The development of a novel opioid antigen designed specifically for the prevention of heroin addiction is necessary. A morphine-keyhole limpet hemocyanin conjugate was prepared and administered subcutaneously in rats. Antibody titers in plasma were measured using an enzyme-linked immunosorbent assay (ELISA). Competitive ELISA was used to assess the selectivity of the antibodies. Dopamine concentrations in the nucleus accumbens in rats after vaccine administration were determined by high-performance liquid chromatography with electrochemical detection. The effects of the vaccine on the heroin-primed restatement of self-administration and locomotor sensitization were evaluated. A novel hapten, 6-glutarylmorphine, was produced, and the vaccine generated a high antibody titer response. This vaccine displayed specificity for both morphine and heroin, but the anti-morphine antibodies could not recognize dissimilar therapeutic opioid compounds, such as buprenorphine, methadone, naloxone, naltrexone, codeine, and nalorphine. The morphine antibody significantly decreased morphine-induced locomotor activity in rats after immunization. Importantly, rats immunized with this vaccine did not exhibit heroin-primed reinstatement of heroin seeking when antibody levels were sufficiently high. The vaccine reduced dopamine levels in the nucleus accumbens after morphine administration, which is consistent with its behavioral effects. These results suggest that immunization with a novel vaccine is an effective means of inducing a morphine-specific antibody response that is able to attenuate the behavioral and psychoactive effects of heroin.

Topics: Animals; Antibodies; Antibody Specificity; Chromatography, High Pressure Liquid; Conditioning, Operant; Disease Models, Animal; Dopamine; Enzyme-Linked Immunosorbent Assay; Extinction, Psychological; Hemocyanins; Heroin; Heroin Dependence; Male; Motor Activity; Nucleus Accumbens; Rats; Rats, Sprague-Dawley; Reinforcement, Psychology; Self Administration; Vaccines, Conjugate

Cell therapies in animal models of neurobehavioral defects are normally derived from neural stem cells (NSC) of the developing cortex. However, the clinical feasibility of NSC therapies would be greatly improved by deriving transplanted cells and from a tissue culture source that is self-renewing, containing cells that potentially differentiate into the desired neuronal phenotypes. These cultures can be engineered to contain the appropriate factors to support their therapeutic action and likely evoke lesser immune reactions. In the current study, we employed our model of mice neurobehaviorally impaired via prenatal exposure to heroin, to test the therapeutic efficacy of NSC derived from murine embryonic stem cells culture (ESC). The culture contained elongated bipolar cells, 90% of which are positive for nestin, the intermediate filament protein found in neural precursors. After removal of growth factors, the NSC differentiated into neurons (34.0% +/- 3.8% NF-160 positive), including cholinergic cells (ChAT positive), oligodendrocytes (29.9% +/- 4.2% O(4)), and astrocytes (36.1% +/- 4.7% GFAP positive). Reverse transcriptase polymerase chain reaction (RT-PCR) analysis confirmed the immunocytochemical findings. Mice made deficient in Morris maze behavior by prenatal heroin exposure (10 mg/kg heroin s.c. on gestational days 9-18) were transplanted into the hippocampus region on postnatal day 35 with the ES culture-derived NSC (ES-NSC) labeled with dialkylcarbocyanine (Dil) cell tracker. Dil+ and NF160+ cells were detected in the hippocampal region (50% +/- 8% survival). The transplantation completely restored maze performance to normal; e.g., on day 3, transplantation improved the behavior from the deficient level of 11.9-sec latency to the control of 5.6-sec latency (44.5% improvement).

Topics: Animals; Cell Differentiation; Cell Survival; Cognition Disorders; Disease Models, Animal; Embryonic Stem Cells; Female; Heroin; Male; Maze Learning; Mice; Narcotics; Neurogenesis; Neurons; Opioid-Related Disorders; Pregnancy; Prenatal Exposure Delayed Effects; Stem Cell Transplantation; Stem Cells

Stress and drug-associated cues can trigger craving and relapse in abstinent drug-dependent individuals. Although the role of these two critical factors in relapse has been extensively studied, the interaction between stress and drug-associated cues in relapse has been less well characterized. Using an animal model of relapse, we assessed the effects of the pharmacological stressor, yohimbine (1.25 or 2.5mg/kg), on reinstatement of extinguished heroin-seeking in rats either in the presence or absence of heroin-associated cues. Yohimbine, in the absence of heroin-associated cues, and cues by themselves reliably reinstated heroin-seeking over extinction levels. Notably, animals showed significantly potentiated responding when yohimbine preceded cue-induced reinstatement (3-4x higher over cues or yohimbine alone). These results demonstrate that exposure to heroin-paired cues during yohimbine-induced stress greatly potentiates heroin-seeking, and support the simultaneous targeting of both stress and cue activation during relapse intervention.

Topics: Animals; Behavior, Addictive; Behavior, Animal; Conditioning, Operant; Cues; Disease Models, Animal; Extinction, Psychological; Heroin; Male; Rats; Rats, Sprague-Dawley; Reinforcement, Psychology; Self Administration; Stress, Psychological; Yohimbine

The success of methadone in treating opiate addiction has suggested that long-acting agonist therapies may be similarly useful for treating cocaine addiction. Here, we examined this hypothesis, using the slow-onset long-acting monoamine reuptake inhibitor 31,345, a trans-aminotetralin analog, in a variety of addiction-related animal models, and compared it with methadone's effects on heroin's actions in the same animal models. Systemic administration of 31,345 produced long-lasting enhancement of electrical brain-stimulation reward (BSR) and extracellular nucleus accumbens (NAc) dopamine (DA). Pretreatment with 31,345 augmented cocaine-enhanced BSR, prolonged cocaine-enhanced NAc DA, and produced a long-term (24-48  h) reduction in cocaine self-administration rate without obvious extinction pattern, suggesting an additive effect of 31,345 with cocaine. In contrast, methadone pretreatment not only dose-dependently inhibited heroin self-administration with an extinction pattern but also dose-dependently inhibited heroin-enhanced BSR and NAc DA, suggesting functional antagonism by methadone of heroin's actions. In addition, 31,345 appears to possess significant abuse liability, as it produces dose-dependent enhancement of BSR and NAc DA, maintains a low rate of self-administration behavior, and dose-dependently reinstates drug-seeking behavior. In contrast, methadone only partially maintains self-administration with an extinction pattern, and fails to induce reinstatement of drug-seeking behavior. These findings suggest that 31,345 is a cocaine-like slow-onset long-acting monoamine transporter inhibitor that may act as an agonist therapy for cocaine addiction. However, its pattern of action appears to be significantly different from that of methadone. Ideal agonist substitutes for cocaine should fully emulate methadone's actions, that is, functionally antagonizing cocaine's action while blocking monoamine transporters to augment synaptic DA.

Topics: Animals; Brain; Cocaine; Cocaine-Related Disorders; Delayed-Action Preparations; Disease Models, Animal; Dopamine; Dose-Response Relationship, Drug; Electric Stimulation; Extinction, Psychological; Heroin; Male; Methadone; Nucleus Accumbens; Plasma Membrane Neurotransmitter Transport Proteins; Rats; Rats, Long-Evans; Self Administration; Tetrahydronaphthalenes

A high incidence of relapse can be triggered by exposure to conditioned cues previously associated with heroin. Extended access to drug and withdrawal are thought to affect the motivation for drug seeking.. The present study evaluated how different periods of training to self-administer heroin and different periods of withdrawal affected drug seeking.. Following 1 to 14 days of heroin self-administration, rats were left in the home environment for 1 or 14 days. Subsequently, rats were evaluated for extinction of nose poke during the first hour after being returned to the training apparatus. One hour later, a conditioned stimulus was presented to initiate cue-induced reinstatement.. Extending the training period from 1 to 14 days caused an escalation of reinstatement of drug seeking induced by conditioned cues. Increasing the withdrawal period from 1 to 14 days produced a similar increase in reinstatement of drug seeking induced by cues. Reinstatement of drug seeking induced by cues was augmented by pretreatment with naltrexone (1, 5 mg/kg) 24 h prior to reinstatement on day 1, but not at 14 days of withdrawal from heroin self-administration.. These experiments demonstrate that increasing the duration of either heroin self-administration or the withdrawal periods from heroin self-administration augments the reinstatement induced by cues that were associated previously with heroin reinforcement. Additionally, we provide one of the first demonstrations that opiate withdrawal induces heroin seeking, as assessed in the reinstatement model.

Topics: Animals; Behavior, Addictive; Behavior, Animal; Conditioning, Operant; Cues; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Administration Schedule; Exploratory Behavior; Heroin; Heroin Dependence; Male; Naltrexone; Narcotic Antagonists; Narcotics; Rats; Rats, Sprague-Dawley; Reinforcement, Psychology; Secondary Prevention; Self Administration; Substance Withdrawal Syndrome

In brain regions that have been implicated in the reinstatement of drug-seeking, the prelimbic cortex has emerged as a critical regulator of relapse behaviours. Here, the effects of prelimbic cortex dopamine (DA) D(1) receptor antagonism on drug-seeking produced by heroin-paired cues, or by a single priming dose of heroin are examined. Rats lever-pressed daily for i.v. heroin discretely paired with a conditioned stimulus during 3-h sessions for a period of 2 wk, followed by extinction and reinstatement of drug-seeking by previously heroin-paired cues (tone+light) or heroin-priming injections (0.25 mg/kg) in the absence of heroin reinforcement. Intracranial infusion of the DA D(1) receptor antagonist, SCH 23390 (0.02-2.0 microg/side), into the prelimbic cortex potently and dose dependently attenuated heroin-seeking in response to either cue presentations or a priming dose of heroin. These results suggest that DA D1 receptors regulate prefrontal cortex pathways necessary for the reinstatement of heroin-seeking.

Topics: Analysis of Variance; Animals; Behavior, Addictive; Benzazepines; Disease Models, Animal; Dose-Response Relationship, Drug; Heroin; Limbic System; Male; Motor Activity; Narcotics; Rats; Rats, Sprague-Dawley; Receptors, Dopamine D1; Reinforcement, Psychology

In humans, exposure to environmental contexts previously associated with heroin intake can provoke relapse to drug use. In rats, exposure to heroin-associated contexts after extinction of drug-reinforced responding in different contexts reinstates heroin seeking. This effect is attenuated by blockade of D(1)-family receptors in lateral or medial accumbens shell, but not accumbens core.. In this study, we further characterized the role of striatal D(1)-family receptors in context-induced reinstatement by assessing the effect of dorsolateral or dorsomedial injections of the D(1)-family receptor antagonist SCH 23390 on this reinstatement.. Rats were trained to self-administer heroin (0.05-0.10 mg/kg per infusion) for 12 days; drug infusions were paired with a discrete tone-light cue. Subsequently, heroin-reinforced lever pressing was extinguished in the presence of the discrete cue in a nondrug context. During reinstatement tests under extinction conditions, the D(1)-family receptor antagonist SCH 23390 (0.3-1.0 microg per side) was injected into the dorsolateral or dorsomedial striatum prior to exposure to heroin self-administration context or the nondrug (extinction) context. We then used a disconnection procedure to examine whether D(1)-family receptors in the dorsolateral striatum and lateral accumbens shell jointly or independently support context-induced reinstatement.. Dorsolateral but not dorsomedial SCH 23390 injections attenuated context-induced reinstatement of heroin seeking. SCH 23390 injections into the dorsolateral striatum of one hemisphere and lateral accumbens shell of the other hemisphere were ineffective.. Results indicate that dorsolateral striatum D(1)-family dopamine receptors are critical for context-induced reinstatement of heroin seeking. Results also suggest that D(1)-receptor-mediated dopamine transmission in the dorsolateral striatum and lateral accumbens shell independently support this reinstatement.

Topics: Animals; Behavior, Addictive; Behavior, Animal; Benzazepines; Conditioning, Psychological; Corpus Striatum; Disease Models, Animal; Extinction, Psychological; Heroin; Heroin Dependence; Male; Nucleus Accumbens; Rats; Rats, Long-Evans; Receptors, Dopamine D1; Reinforcement Schedule; Reward; Secondary Prevention; Self Administration

There remains debate regarding the impact of cannabis on neuropsychiatric disorders. Here, we examined the effects of cannabidiol (CBD), a nonpsychoactive constituent of cannabis, on heroin self-administration and drug-seeking behavior using an experimental rat model. CBD (5-20 mg/kg) did not alter stable intake of heroin self-administration, extinction behavior, or drug seeking induced by a heroin prime injection. Instead, it specifically attenuated heroin-seeking behavior reinstated by exposure to a conditioned stimulus cue. CBD had a protracted effect with significance evident after 24 h and even 2 weeks after administration. The behavioral effects were paralleled by neurobiological alterations in the glutamatergic and endocannabinoid systems. Discrete disturbances of AMPA GluR1 and cannabinoid type-1 receptor expression observed in the nucleus accumbens associated with stimulus cue-induced heroin seeking were normalized by CBD treatment. The findings highlight the unique contributions of distinct cannabis constituents to addiction vulnerability and suggest that CBD may be a potential treatment for heroin craving and relapse.

Topics: Animals; Cannabidiol; Cannabinoid Receptor Modulators; Conditioning, Psychological; Cues; Disease Models, Animal; Glutamic Acid; Heroin; Heroin Dependence; Limbic System; Male; Narcotic Antagonists; Narcotics; Neural Pathways; Nucleus Accumbens; Rats; Rats, Long-Evans; Receptor, Cannabinoid, CB1; Receptors, AMPA; Treatment Outcome; Ventral Tegmental Area

Numerous findings suggest that drug seeking and ingestive behaviors share common neurobiological mechanisms, but the relevant pathways are unknown. Dietary manipulations result in changes in endocrine the and/or neuropeptide signals, such as the hormones leptin and ghrelin, which are dynamically linked to energy balance and the regulation of feeding behavior. We have recently demonstrated that food deprivation-induced reinstatement of heroin seeking can be blocked with leptin, and others have suggested a role for ghrelin in drug-related behaviors. The feeding-relevant effects of leptin and ghrelin involve the inhibition or activation, respectively, of neuropeptide Y/agouti-related peptide (NPY/AGRP) neurons in the hypothalamus. However, the effects of NPY, a highly potent orexigenic peptide, on drug-related behaviors have not been thoroughly studied. Here we examined the effect of acute NPY administration on the rate of heroin self-administration and the reinstatement of extinguished heroin-seeking behavior. Heroin intake (0.05mg/kg/infusion) was tested using a self-administration procedure (FR-1), 10-min post-NPY injections (0.0, 4.0, and 10microg/rat, ICV). In a different group of rats, NPY-induced reinstatement (0.0, 4.0, and 10microg/rat, ICV) of extinguished heroin seeking was assessed. NPY injections increased on-going heroin self-administration, and induced a reinstatement of extinguished heroin-seeking behavior. These findings suggest that NPY can modulate the rewarding and conditioned reinforcing effects of drugs of abuse.

Topics: Animals; Behavior, Animal; Conditioning, Operant; Disease Models, Animal; Food Deprivation; Heroin; Heroin Dependence; Male; Narcotics; Neuropeptide Y; Rats; Rats, Long-Evans; Reinforcement Schedule; Reinforcement, Psychology; Self Administration

To investigate the expression of caspase 3 in the brain regions related to addiction, learning and memory in mice prenatally exposed to heroin and to ascertain whether postnatal apoptotic mechanism participates in neurobehavioral teratogenicity induced by maternal heroin abuse.. A mouse model was established by administration of diacetylmorphine (heroin, purity 98.5%, product ID No.171206-200614) 10 mg/(kg x d) subcutaneously to pregnant BALB/c mice on embryonic day (E)E8-E18. The offspring were divided into heroin(Her) and saline(Sal) groups according to the maternal treatment. The expression of caspase 3 in prefrontal lobe cortex(PFC), hippocampus(HP) and nucleus accumbens(Acb) was detected by RT-PCR and Western blot on mouse postnatal day(P)14.. The mRNA and protein expression of caspase 3 were significantly increased in the areas of PFC, HP and Acb in Her group compared with Sal group(P < 0.05).. E8-E18 prenatal exposure to heroin can induce apoptosis through caspase 3 activation in brain regions related to addiction, learning and memory, which indicates that apoptotic mechanism may be involved in neurobehavioral teratogenicity by heroin exposure in uterus.

Topics: Animals; Caspase 3; Disease Models, Animal; Female; Gene Expression; Heroin; Heroin Dependence; Hippocampus; Humans; Learning; Male; Maternal Exposure; Memory; Mice; Mice, Inbred BALB C; Nucleus Accumbens; Prefrontal Cortex; Pregnancy

Previous studies show that the acute administration of N-acetylcysteine (NAC) inhibits the desire for cocaine in addicts and cocaine-seeking in animals.. Rats were trained to self-administer heroin, and the reinstatement model of drug seeking was used to determine whether chronic NAC treatment inhibited heroin-seeking.. Daily NAC administration inhibited cue- and heroin-induced seeking. Moreover, repeated NAC administration during extinction training reduced extinction-responding and inhibited cue- and heroin-induced reinstatement for up to 40 days after discontinuing daily NAC injection.. These data show that daily NAC inhibits heroin-induced reinstatement and produces an enduring reduction in cue- and heroin-induced drug seeking for over 1 month after the last injection of NAC. Both the inhibitory effect of NAC on the reinstatement of heroin-seeking and the ability of NAC to reduce extinction-responding support clinical evaluation of repeated NAC administration to decrease in drug-seeking in heroin addicts.

Topics: Acetylcysteine; Animals; Behavior, Animal; Cues; Disease Models, Animal; Drug Interactions; Extinction, Psychological; Free Radical Scavengers; Heroin; Heroin Dependence; Male; Narcotics; Rats; Rats, Sprague-Dawley; Time Factors

Grafting of neural progenitors has been shown to reverse a wide variety of neurobehavioral defects. While their role of replacing injured cells and restoring damaged circuitries has been shown, it is widely accepted that this cannot be the only mechanism, as therapy can occur even when an insufficient number of transplanted cells are found. We hypothesized that one major mechanism by which transplanted neural progenitors exert their therapeutic effect is by enhancing endogenous cells production. Consequently, in an allographic model of transplantation, prenatally heroin-exposed genetically heterogeneous (HS) mice were made defective in their hippocampal neurobehavioral function by exposing their mothers to heroin (10 mg kg(-1) heroin on gestation days 9-18). Hippocampal damage was confirmed by deficient performance in the Morris maze (P<0.009), and decreased production of endogenous cells in the dentate gyrus by 39% was observed. On postnatal day 35, they received an HS-derived neural progenitors transplant followed by repeated bromodeoxyuridine injections. The transplant returned endogenous cells production to normal levels (P<0.006) and reversed the behavioral defects (P<0.03), despite the fact that only 0.0334% of the transplanted neural progenitors survived and that they differentiated mainly to astrocytes. An immunological study demonstrated the presence of macrophages and T cells as a possible explanation for the paucity of the transplanted cells. This study suggests one mechanism for the therapeutic action of neural progenitors, the enhancement of the production of endogenous cells, pointing to future clinical applications in this direction by use of neural progenitors or by analogous cell-inducing techniques.

Topics: Animals; Animals, Newborn; Behavior, Animal; Brain Injuries; Bromodeoxyuridine; Cell Count; Cell Differentiation; Cell Proliferation; Disease Models, Animal; Female; Glial Fibrillary Acidic Protein; Heroin; Hippocampus; Male; Maze Learning; Mice; Neurons; Pregnancy; Prenatal Exposure Delayed Effects; Stem Cell Transplantation; Stem Cells; Time Factors

Escalation of drug consumption-a hallmark of addiction-has been hypothesized to be associated with a relative devaluation of alternative nondrug rewards and thus with a decrease in their ability to compete with or to substitute for the drug. In a behavioral economic framework, decreased substitutability of nondrug rewards for drug would explain why drug consumption is behaviorally dominant and relatively resistant to change (eg price-inelastic) in drug-addicted individuals. The goal of the present study was to test this hypothesis using a validated rat model of heroin intake escalation. Escalation was precipitated by long (6 h, long access (LgA)), but not short (1 h, short access (ShA)), daily access to i.v. heroin self-administration. After escalation, the effects of price (ie fixed-ratio value) on heroin consumption were assessed under two alternative reward conditions: in the presence or absence of a nondrug substitute for heroin (ie four freely available chow pellets). As expected, escalated heroin consumption by LgA rats was less sensitive to price than heroin consumption by ShA rats, showing that heroin had acquired greater reinforcing strength during escalation. However, supplying a substitute during access to heroin was sufficient to reverse this post-escalation increase in the reinforcing effectiveness of heroin. Thus, escalated heroin consumption is not associated with a decreased sensitivity to competing nondrug rewards. Escalated drug use may therefore persist, not so much because of a relative devaluation of nondrug substitutes, but because of a loss or reduction of their availability.

Topics: Analysis of Variance; Animals; Behavior, Addictive; Behavior, Animal; Conditioning, Operant; Disease Models, Animal; Eating; Extinction, Psychological; Feeding Behavior; Heroin; Male; Narcotics; Rats; Rats, Wistar; Reinforcement Schedule; Self Administration; Time Factors

As with other drugs of abuse, heroin use is characterized by a high incidence of relapse following detoxification that can be triggered by exposure to conditioned stimuli previously associated with drug availability. Recent findings suggest that cannabinoid CB(1) receptors modulate the motivational properties of heroin-conditioned stimuli that induce relapse behavior. However, the neural substrates through which CB(1) receptors modulate cue-induced heroin seeking have not been elucidated. In this study, we evaluated alterations in cue-induced reinstatement of heroin-seeking behavior produced by infusions of the CB(1) receptor antagonist SR 141716A (0, 0.3 and 3 microg per side) delivered into the prefrontal cortex (PFC), nucleus accumbens (NAC), and basolateral amygdala (BLA) of rats. Results show that following extinction of operant behavior the presentation of a discriminative stimulus conditioned to heroin availability reinstated nonreinforced lever pressing to levels comparable to preextinction levels. Intra-PFC SR 141716A dose-dependently reduced cue-induced reinstatement of heroin seeking, with a significant reduction following the 3 microg per side dose. In the NAC, both SR 141716A doses induced a significant reduction in cue-induced reinstatement, with the highest dose completely blocking the effect of the cue. In contrast, intra-BLA SR 141716A did not alter cue-induced reinstatement of responding while systemic administration of this antagonist (3 mg/kg, i.p.) significantly blocked cue-induced reinstatement in all three-placement groups (BLA, PFC, and NAC). These findings provide new insights into the neural mechanisms through which CB(1) receptors modulate the motivational properties of heroin-associated cues inducing relapse.

Topics: Amygdala; Animals; Conditioning, Operant; Cues; Disease Models, Animal; Dose-Response Relationship, Drug; Extinction, Psychological; Heroin; Heroin Dependence; Male; Motivation; Narcotics; Nucleus Accumbens; Piperidines; Prefrontal Cortex; Pyrazoles; Rats; Rats, Wistar; Receptor, Cannabinoid, CB1; Reinforcement, Psychology; Reward; Rimonabant

Addictive drugs have been shown to severely influence many neuronal functions, which are considered as the underlying mechanisms for physiological and psychological dependences. We previously showed that in vivo LTP in rat hippocampal CA1 region is significantly reduced during withdrawal following chronic opiates treatment, and the reduced LTP can be restored by re-exposure of animals to corresponding drugs. Here, we further demonstrated that during opiates withdrawal, the re-exposure of morphine either systemically (subcutaneously) or locally (intracerebroventricularly) could restore the reduced LTP in heroin-dependent rats, but heroin could not restore the reduced LTP, in morphine-dependent rats, indicating differential modulations of hippocampal functions by those two opiates. In contrast, DAMGO, a mu-opioid receptor (MOR) agonist, could restore the reduced LTP, and CTOP, a MOR antagonist, could block the restoration in rats dependent on both opiates, showing that MOR is functional under such conditions. However, the upregulation of hippocampal PKA activity during morphine withdrawal could be suppressed by re-exposure of morphine but not that of heroin, suggesting a likely underlying mechanism of the differential modulation of LTP by two opiates. Taken together, our study clearly demonstrates that chronic abuse of opiates inevitably leads to severe alteration of hippocampal LTP, and reveals the interesting differences between morphine and heroin in their effects on the differential modulation of hippocampal synaptic plasticity.

Topics: Animals; Behavior, Animal; Conditioning, Operant; Disease Models, Animal; Dose-Response Relationship, Drug; Dose-Response Relationship, Radiation; Drug Interactions; Electric Stimulation; Heroin; Hippocampus; Long-Term Potentiation; Male; Morphine; Narcotic Antagonists; Narcotics; Opioid-Related Disorders; Rats; Rats, Sprague-Dawley

Opioid overdose, which is commonly associated with opioid induced respiratory depression, is a problem with both therapeutic and illicit opioid use. While the central mechanisms involved in the effects of opioids are well described, it has also been suggested that a peripheral component may contribute to the effects observed. This study aimed to further characterise the effects of the peripherally acting naloxone methiodide on the respiratory, analgesic and withdrawal effects produced by various opioid agonists. A comparison of the respiratory and analgesic effects of morphine, methadone and heroin in male Swiss-Albino mice was conducted and respiratory depressive ED(80) doses of each opioid determined. These doses (morphine 9 mg/kg i.p., methadone 7 mg/kg i.p., and heroin 17 mg/kg i.p.) were then used to show that both naloxone (3 mg/kg i.p.) and naloxone methiodide (30-100 mg/kg i.p.) could reverse the respiratory and analgesic effects of these opioid agonists, but only naloxone precipitated withdrawal. Further investigation in female C57BL/6J mice using barometric plethysmography found that both opioid antagonists could reverse methadone induced decreases in respiratory rate and increases in tidal volume. Its effects do not appear to be strain or sex dependent. It was concluded that naloxone methiodide can reverse the respiratory and analgesic actions of a variety of opioid agonists, without inducing opioid withdrawal.

Topics: Analgesics, Opioid; Animals; Disease Models, Animal; Drug Interactions; Female; Heroin; Male; Methadone; Mice; Mice, Inbred C57BL; Morphine; Naloxone; Plethysmography, Whole Body; Quaternary Ammonium Compounds; Respiration; Respiratory Insufficiency; Substance Withdrawal Syndrome

To investigate the effect of heroin on purine nucleotides catabolism, a rat model of heroin administration and withdrawal was established. Concentrations of uric acid, creatinine, and urea nitrogen in plasma and ADA in plasma, brain, liver, and small intestine were tested. When two heroin administration groups were compared with the control group, the concentrations of plasma uric acid and ADA in plasma, brain, liver, and small intestine increased, whereas the plasma urea nitrogen concentrations in two heroin administration groups and the plasma creatinine concentration in the 3-day heroin administration group did not increase. It seemed that heroin exposure for a short time did not affect renal clearance rate notably. When two withdrawal groups were compared with two heroin administration groups, the concentrations of plasma uric acid and ADA in liver and small intestine decreased, but there was no significant reduction in ADA concentrations of the brain, while the plasma ADA concentrations in the two withdrawal groups were significantly higher than those of two heroin administration groups. When the two withdrawal groups were compared with the control group, there was no significant difference in the concentrations of plasma uric acid and ADA in liver and small intestine, while the concentrations of ADA in plasma and brain were still higher than those of the control group. The results imply that heroin administration may enhance the catabolism of purine nucleotides in the brain and other tissues by increased concentration of ADA and the effect may last for a long time in the brain.

Topics: Adenosine Deaminase; Animals; Brain; Disease Models, Animal; Heroin; Heroin Dependence; Male; Purine Nucleotides; Rats; Rats, Wistar; Substance Withdrawal Syndrome; Urea; Uric Acid

Several self-administration models have been used to study the interactions between cocaine and heroin, and the schedule of reinforcement used is an important consideration for these studies. Behavior maintained by cocaine, heroin or their combination was studied using a discrete trial schedule that has been described for cocaine self-administration previously. This schedule permits 24 h access to drug without mortality associated with unlimited access to cocaine, and provides unique measures related to the circadian pattern of drug self-administration. Cocaine and heroin combined maintained higher rates of responding compared to either drug alone when a maximum of three infusions were available each hour (DT3), and decreased food intake compared to cocaine alone. There were significantly greater numbers of hours in both the light and dark cycles during which animals self-administered heroin or the combination of cocaine/heroin compared to cocaine alone. When the FR was increased to 4 under the DT3 access conditions, responding maintained by cocaine or heroin extinguished to levels not different than those maintained by saline while food reinforcement remained intact. The combination of cocaine and heroin maintained robust responding under these conditions. This schedule of reinforcement appears to elucidate behavioral interactions between cocaine and heroin that are more complex than rate of drug consumption and may provide a procedure to address some of the issues related to co-abuse of these drugs.

Topics: Animals; Circadian Rhythm; Cocaine; Disease Models, Animal; Drug Interactions; Feeding Behavior; Heroin; Male; Rats; Rats, Inbred F344; Reinforcement, Psychology; Self Administration

The goal of the present study was to develop and validate an animal model of unlimited access to intravenous heroin self-administration combined with responding for food and water to characterize the transition to drug dependence. Male Wistar rats were allowed to lever press for heroin (60 microg/kg/0.1 ml infusion/s; fixed ratio 1; 20-s time out) and nosepoke for food and water in consecutive, daily 23-h sessions. Daily heroin intake increased over days, reaching significance by Day 14. Drug-taking increased across the circadian cycle, reflected as increases in both the nocturnal peak and diurnal nadir of heroin intake. Changes in the circadian pattern of food intake and meal patterning preceded and paralleled the changes in heroin intake. By Day 7, the circadian amplitude of feeding was blunted. Nocturnal intake decreased because rats consumed smaller and briefer meals. Diurnal intake increased due to increased meal frequency, whereas total daily food intake decreased. To control for time or experience in the self-administration boxes as a possible confound, rats with saline (no drug) tethers were tested and did not display significant changes in food intake pattern. Body weight gain slowed slightly in heroin rats relative to saline controls. Separate groups of rats revealed that significant physical dependence as measured by physical signs of opiate withdrawal following a naloxone injection (1.0 mg/kg, subcutaneous (s.c.)) was reached by Day 14. Significant increases in heroin intake could be produced using low doses of naloxone (0.003-0.03 mg/kg, s.c.) on days 28-31 of heroin access. After 6 weeks of heroin self-administration, rats injected with buprenorphine (0, 0.01, 0.04, and 0.2 mg/kg, s.c.) showed a dose-dependent reduction in heroin intake. Changes in the pattern of drug and food intake in the present unlimited heroin access model may serve as independent motivational markers for the transition to a drug-dependent state.

Topics: Analgesics, Opioid; Animals; Biomarkers; Body Weight; Brain; Buprenorphine; Circadian Rhythm; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Interactions; Eating; Feeding Behavior; Heroin; Injections, Intravenous; Male; Motivation; Narcotic Antagonists; Narcotics; Opioid-Related Disorders; Rats; Rats, Wistar; Self Administration; Substance Withdrawal Syndrome

Several medications are approved for treatment of opiate abuse, but determinants of their clinical effectiveness are not completely understood. States of opiate dependence or withdrawal may constitute one important set of determinants. To test this hypothesis, the effects of naloxone, buprenorphine, and methadone were assessed on choice between heroin and food in nondependent rhesus monkeys and in heroin-dependent monkeys undergoing withdrawal. A choice procedure was used to permit dissociation of medication effects on the relative reinforcing properties of heroin from nonselective effects on response rates. In nondependent monkeys, increasing unit doses of heroin (0-0.1 mg/kg/injection) maintained dose-dependent increases in heroin choice. Chronic 5-day treatment with naloxone (0.01-0.32 mg/kg/h) or buprenorphine (0.01-0.1 mg/kg/day) produced dose-dependent rightward shifts in heroin choice dose-effect curves, whereas chronic methadone (0.1-0.56 mg/kg/h) had little effect on heroin choice up to doses that suppressed responding. In heroin-dependent monkeys, opiate withdrawal produced overt abstinence signs as well as increases in heroin choice, manifested as leftward shifts in heroin choice dose-effect curves. The withdrawal-associated increases in heroin choice suggest that opiate withdrawal increased the relative reinforcing efficacy of heroin in comparison with food, an effect that may be related to relapse in humans. Methadone prevented withdrawal-associated increases in heroin choice, whereas buprenorphine was less effective. These findings suggest that agonist medications such as methadone may derive their clinical utility from their ability to attenuate withdrawal-associated increases in opiate reinforcement. Moreover, this procedure may be useful for exploring mechanisms underlying withdrawal-associated increases in opiate reinforcement and for testing candidate medications.

Topics: Animals; Buprenorphine; Disease Models, Animal; Feeding Behavior; Heroin; Heroin Dependence; Macaca mulatta; Male; Methadone; Naloxone; Self Administration; Substance Withdrawal Syndrome

Immunohistochemical distribution patterns of neuropeptide FF (NPFF) and neuropeptide tyrosine (NPY) were studied in the brain of rats submitted to two different protocols of heroin treatment. In drug-naive rats, acutely injected heroin significantly depleted NPFF-immunoreactive material within the neurons of the nucleus of solitary tract (NTS), significantly decreased the density of NPFF-immunoreactive nerve fibers within the median eminence, pituitary stalk, and neurohypophysis, and markedly increased NPY-immunoreactive neurons and nerve fibers in the thalamic paraventricular nucleus and bed nucleus of stria terminalis. In drug-sensitized rats, heroin significantly increased the number and immunostaining intensity of the NPFF-immunoreactive neurons within the NTS and induced minor changes in the NPFF-immunoreactive nerve fiber network of the median eminence, pituitary stalk, and neurohypophysis and a relatively minor increase in NPY neurons in the thalamic paraventricular nucleus and bed nucleus of stria terminalis. These heroin-induced changes suggest that NPFF is involved in regulating the effects of the heroin injection and in the mechanisms underlying behavioral sensitization. They also add further support to the key role of NPY in any conditions tending to change the animal homeostasis.

Topics: Animals; Brain; Brain Chemistry; Disease Models, Animal; Heroin; Heroin Dependence; Hypothalamo-Hypophyseal System; Immunohistochemistry; Male; Midline Thalamic Nuclei; Narcotics; Neuropeptide Y; Oligopeptides; Pituitary Gland; Presynaptic Terminals; Rats; Rats, Sprague-Dawley; Septal Nuclei; Solitary Nucleus

Prenatal exposure of mice to heroin resulted in behavioral deficits present at adulthood, and related to septohippocampal cholinergic innervation accompanied by both pre- and postsynaptic cholinergic hyperactivity; including an increase in membrane PKC activity, and a desensitization of PKC to cholinergic input, which correlated highly with the behavioral performance, and was reversed by cholinergic grafting. The effect was shown in the behaviorally relevant PKCgamma and beta whereas the less behaviorally relevant PKCalpha isoform was not affected. The present study was designed to establish the effect of heroin exposure on the expression of the PKC isoforms level and on the more functionally relevant cholinergic translocation/activation of the isoforms throughout postnatal development. The hippocampi of mice pups, exposed to heroin transplacentally, were assayed after incubation with carbachol for PKC isoforms on postnatal days (PN) 1, 7, 14, 21, 30 and 50. Prenatal heroin exposure increased basal PKCgamma, beta and alpha levels. PKCgamma and alpha levels returned to control levels on PN50. While in PKCbeta, this increase lasted until PN50. Translocation/activation of the PKC isoforms gamma and beta by cholinergic receptor stimulation was present from PN1, concurrent with the presence of the isoforms. Prenatal exposure to heroin completely abolished the translocation/activation throughout the entire postnatal development. This defect was shown from the very beginning, PN1, the day when the PKC isoforms appear. The results suggest that the PKCgamma and beta isoforms are functional concurrent with their developmental appearance. Unlike findings on some other teratogens, the prenatal heroin effect on the isoforms function is similar throughout postnatal development.

Topics: Acetylcholine; Analgesics, Opioid; Animals; Animals, Newborn; Cholinergic Agonists; Cholinergic Fibers; Disease Models, Animal; Enzyme Activation; Female; Heroin; Heroin Dependence; Hippocampus; Male; Mice; Neural Pathways; Organ Culture Techniques; Pregnancy; Prenatal Exposure Delayed Effects; Protein Isoforms; Protein Kinase C; Protein Transport; Receptors, Cholinergic; Septal Nuclei

Aspects of drug withdrawal may become conditioned to previously neutral environmental stimuli via classical conditioning processes. Nevertheless, the significance of conditioned withdrawal effects in motivating drug intake remains largely unexplored. Here, we investigated the effects of conditioned withdrawal in modulating heroin consumption and brain reward sensitivity in rats. Rats intravenously self-administered heroin (20 microg/infusion) during 0 h (control), 1 h (nondependent), or 23 h (dependent) sessions and had daily intracranial self-stimulation (ICSS) thresholds assessed. ICSS thresholds remained stable and unaltered in control rats. In nondependent rats, heroin self-administration induced a transient activation of reward systems, reflected in lowering of ICSS thresholds. In dependent rats, heroin intake escalated across sessions and was associated with a gradual decrease in reward sensitivity, reflected in progressively elevated ICSS thresholds. Thus, as dependence develops, heroin may be consumed not only for its acute reward-facilitating effects, but also to counter persistent deficits in reward sensitivity. In nondependent rats, the opioid receptor antagonist naloxone (30 microg/kg) increased heroin consumption and reversed heroin-induced lowering of ICSS thresholds, effects resistant to classical conditioning. In contrast, in dependent rats naloxone (30 microg/kg) increased heroin consumption and also elevated ICSS thresholds above their already elevated baseline levels (i.e., precipitated withdrawal). Most importantly, stimuli repeatedly paired with naloxone-precipitated withdrawal provoked heroin consumption and elevated ICSS thresholds in dependent rats. Thus, conditioned stimuli predicting the onset of heroin withdrawal, and hence the reward deficits coupled with this state, may play a critical role in provoking craving and relapse in human opiate addicts.

Topics: Animals; Conditioning, Classical; Disease Models, Animal; Electric Stimulation; Heroin; Heroin Dependence; Male; Naloxone; Narcotic Antagonists; Rats; Reward; Self Stimulation; Substance Withdrawal Syndrome

In heroin overdose deaths the blood morphine concentration varies substantially. To explore possible pharmacokinetic explanations for variable sensitivity to opiate toxicity we studied mortality and drug concentrations in male Sprague-Dawley rats. Groups of rats were injected intravenously (i.v.) with heroin, 21.5 mg/kg, or morphine, 223 mg/kg, causing a 60-80% mortality among drug-naïve rats. Additional groups of rats were pre-treated with morphine for 14 days, with or without 1 week of subsequent abstinence. Brain, lung and blood samples were analyzed for 6-acetylmorphine, morphine, morphine-3-glucuronide and morphine-6-glucuronide. i.v. morphine administration to drug-naïve rats resulted in both rapid and delayed deaths. The brain morphine concentration conformed to an exponential elimination curve in all samples, ruling out accumulation of morphine as an explanation for delayed deaths. This study found no support for formation of toxic concentration of morphine-6-glucuronide. Spontaneous death among both heroin and morphine rats occurred at fairly uniform brain morphine concentrations. Morphine pre-treatment significantly reduced mortality upon i.v. morphine injection, but the protective effect was less evident upon i.v. heroin challenge. The morphine pre-treatment still afforded some protection after 1 week of abstinence among rats receiving i.v. morphine, whereas rats given i.v. heroin showed similar death rate as drug-naïve rats.

Topics: Animals; Brain; Disease Models, Animal; Drug Overdose; Heroin; Inactivation, Metabolic; Injections, Intraperitoneal; Injections, Intravenous; Lung; Male; Morphine; Rats; Rats, Sprague-Dawley

Topics: Animals; Conditioning, Classical; Disease Models, Animal; Electric Stimulation; Heroin; Heroin Dependence; Male; Naloxone; Narcotic Antagonists; Rats; Reward; Self Stimulation; Substance Withdrawal Syndrome

Understanding the mechanism of neurobehavioral teratogenicity is the primary prerequisite for reversal of the defect. Progress in such studies can be best achieved if the investigation focuses on behaviors related to a specific brain region and innervation. Our model focused on teratogen-induced deficits in hippocampus-related eight-arm and Morris maze behaviors. Different "cholinergic" teratogens, mainly heroin, induced both pre- and postsynaptic hyperactivity in the hippocampal cholinergic innervation that terminated in desensitization of Protein Kinase C (PKC) isoforms to cholinergic receptor stimulation. Understanding this mechanism enabled its reversal with a pharmacological therapy-nicotine infusion. Studies by others provided similar findings by targeting the deficits respective to the model investigated. Consistently, destruction of the A10-septal dopaminergic pathways that downregulate the septohippocampal cholinergic innervation ameliorated maze performance. Grafting of embryonic differentiated cholinergic cells or neural progenitors similarly reversed the biochemical/molecular alterations and the resulting deficits. Reversal therapies offer a model for the understanding of neurobehavioral teratogenicity and, clinically, offer a model for potential treatment of these deficits. Whereas neural progenitor grafting appears to be the most effective treatment, pharmacological reversal with nicotine infusion seems to possess the most feasible and immediate therapy for neurobehavioral birth defects produced by various teratogens, including drugs. This is true even though the effect of pharmacological therapies is diffuse, affecting multiple areas of the brain. "Everybody is talking about the weather but nobody does anything about it." (Mark Twain).

Topics: Animals; Behavior, Animal; Chickens; Disease Models, Animal; Female; Heroin; Hippocampus; Mice; Phenobarbital; Pregnancy; Pregnancy, Animal; Prenatal Exposure Delayed Effects; Teratogens

The role of heroin-related stimuli in motivating the resumption of heroin use is not fully understood.. The objective was to characterize the relative importance of drug-related contextual stimuli, discriminative stimuli (DS), or discrete conditioned stimuli (CSs) on drug seeking when rats were reintroduced into the operant context after withdrawal.. Nose-poke responding by male rats was reinforced with intravenous heroin (0.05 mg/kg per infusion, 4-h session daily) under a progressive ratio schedule of reinforcement for 14 days. Each session began with the illumination of a green light in the active hole that served as DS. Each earned heroin injection was paired with a 5-s compound cue light and the sound of the infusion pump that served as the discrete CSs.. Response rates of heroin seeking induced by the contextual stimuli were comparable to the average rates of responding during self-administration training, but rates induced by either DS or CSs were greater than those induced by the contextual stimuli alone (P<0.05). The responding induced by contingent presentations of CSs was higher than that of DS after extinction of instrumental behavior. The drug seeking induced by CSs can be maintained after 3 days extinction with DS in the original context, although the responding elicited by DS cannot be recovered after 3 days of extinction with CSs.. The relapse to drug seeking can be elicited separately by environmental cues, heroin-predictive DS, or discrete CSs in the same rat after withdrawal.

Topics: Analgesics, Opioid; Animals; Cues; Disease Models, Animal; Extinction, Psychological; Heroin; Heroin Dependence; Infusions, Intravenous; Male; Rats; Rats, Sprague-Dawley; Recurrence; Reinforcement Schedule; Self Administration; Signal Detection, Psychological; Substance Withdrawal Syndrome; Time Factors

Using c-Fos protein immunohistochemistry we previously demonstrated various sites of activation in the rat forebrain according to the animal's drug history. This study originates from a more detailed evaluation ex-post of the same specimens. A discrete number of c-Fos protein immunoreactive nuclei could be observed in some circumventricular organs, including the vascular organ of terminal lamina (OVLT) and subfornical organ (SFO) and in the nucleus of solitary tract near the area postrema, but only in specimens from sensitized rats. We therefore suggest that repeated drug injections activate the normally low drug metabolizing enzyme activity in the circumventricular organs thus implicating these organs in the complex mechanisms underlying behavioral sensitization.

Topics: Animals; Area Postrema; Disease Models, Animal; Enzyme Activation; Enzymes; Heroin; Heroin Dependence; Hypothalamus; Immunohistochemistry; Narcotics; Neural Pathways; Proto-Oncogene Proteins c-fos; Rats; Rats, Sprague-Dawley; Solitary Nucleus; Subfornical Organ; Up-Regulation

We investigated immune, endocrine, and somatic alterations using two animal models of human heroin administration. In a heroin self-administration paradigm, we observed changes in immune function which suggest that the cycle of intermittent drug use is actually a stressor, which in turn not only exacerbates craving and drug-seeking behavior but also collaterally causes suppression of immune function and therefore susceptibility to disease. In another model of rats made physically dependent to heroin, we show that immune function is more broadly compromised, leading to evidence of infection, followed by chronic activation of innate immune function, cachexia, and weight loss.

Topics: Animals; Behavior, Animal; Body Weight; Disease Models, Animal; Drug Administration Routes; Drug Administration Schedule; Heroin; Heroin Dependence; Immune System; Neurosecretory Systems; Rats; Self Administration

Although it is well established that methadone can be an effective treatment for opiate addiction, it is not clear how methadone maintenance affects cocaine use and cravings in individuals who self-administer both opiates and cocaine. In our attempt to explore the effect of methadone maintenance on the effects of cocaine, we first assessed the locomotor stimulatory effects of cocaine in rats maintained on methadone (0, 10, 20, or 30 mg/kg/day, via osmotic minipumps). Chronic methadone elevated baseline locomotion in a dose-dependent manner and did not reduce the direct stimulatory effects of cocaine (5 mg/kg). We then investigated the effects of the highest methadone maintenance dose (30 mg/kg/day) on heroin and cocaine seeking in extinction, and when it was precipitated by exposure to heroin, cocaine, or foot-shock stress in rats trained to self-administer both drugs in the same experimental context (heroin 0.05 mg/kg/inf; cocaine 0.5 mg/kg/inf, eight 3-h sessions each). In tests of reinstatement, rats responded selectively on the appropriate drug-associated lever after priming injections of heroin (0.25 mg/kg) or cocaine (20 mg/kg). Methadone maintenance blocked both cocaine- and heroin-induced reinstatement, but not stress-induced reinstatement, which was not lever selective. These results suggest that although methadone maintenance may not reduce the direct stimulatory effects of cocaine, it has the potential to reduce both spontaneous and cocaine-primed cocaine-seeking behavior.

Topics: Analysis of Variance; Animals; Behavior, Addictive; Behavior, Animal; Cocaine; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Interactions; Heroin; Locomotion; Methadone; Narcotics; Rats; Rats, Long-Evans; Secondary Prevention; Self Administration; Stress, Psychological; Substance-Related Disorders

Using a rat relapse model, recent studies reported time dependent increases in cocaine seeking induced by re-exposure to cocaine cues, but not cocaine itself, over withdrawal periods of up to 3 months.. In the present study, we explored the time course of cocaine seeking induced by priming injections of heroin over the first 3 months of withdrawal from cocaine.. Rats were trained to self-administer intravenous cocaine for 6 h/day over a period of 10 days. Cocaine seeking induced by heroin priming was then assessed in different groups of rats after 1 day, and 1 and 3 months of withdrawal from cocaine. During the test day, rats were first given six 1-h extinction sessions. Subsequently, reinstatement of cocaine seeking induced by non-contingent saline and heroin injections (0.125 and 0.25 mg/kg, s.c.) was assessed during three 1-h sessions.. As in previous studies, extinction responding was substantially greater after 1 and 3 months of withdrawal than after 1 day. More importantly, we also found that the effect of heroin priming on reinstatement of cocaine seeking is time dependent, with higher responding occurring after 1 and 3 months than after 1 day.. The present results replicate previous findings on the time dependent increases in resistance to extinction after withdrawal from cocaine, and further indicate that the duration of the drug withdrawal period is a critical modulator of the effect of heroin priming on cocaine seeking. These data may have implications for the treatment of cocaine relapse induced by other drugs.

Topics: Animals; Behavior, Addictive; Cocaine; Conditioning, Operant; Disease Models, Animal; Drug Administration Schedule; Extinction, Psychological; Forecasting; Heroin; Injections, Intravenous; Injections, Subcutaneous; Male; Rats; Rats, Long-Evans; Recurrence; Self Administration; Substance Withdrawal Syndrome; Time Factors

Environmental stimuli and conditioned cues associated with heroin can induce drug-seeking behavior, but how heroin lapse interacts with cues is unclear. Rats were trained to nose-poke for i.v. heroin for 14 days and then tested for heroin seeking after withdrawal from heroin self-administration. Heroin seeking induced by cues persisted over several weeks after withdrawal, and the responding was not easily extinguished after 4 weeks withdrawal. A single injection of heroin (250 micro g/kg) enhanced the responding at early stage of withdrawal, but a low dose of heroin (50, 250 micro g/kg) suppressed the responding induced by contextual or conditioned cues at 4 weeks of withdrawal. The results suggest that prolonged withdrawal may increase the risk of relapse to heroin seeking.

Topics: Animals; Conditioning, Operant; Cues; Disease Models, Animal; Dose-Response Relationship, Drug; Heroin; Heroin Dependence; Male; Rats; Rats, Sprague-Dawley; Recurrence; Reward; Risk Factors; Self Administration; Substance Withdrawal Syndrome; Time Factors

Addiction to opium and heroin is not only an important social and individual problem in the world but it also affects the human physiology and multiple systems. The aim of this study is to determine the effects of chronic heroin consumption on basal and vagus electrical-stimulated total gastric acid and pepsin secretion in rats.. The study was carried out in the Department of Physiology, Kerman University of Medical Sciences, Iran from August 2002 to June 2003. Both male and female rats weighing 200-250 g were used. Rats received daily doses of heroin intraperitoneally starting from 0.2 mg/kg to 0.1 mg/kg/day up to the maintenance level of 0.7 mg/kg and continued until day 12. After anesthesia, tracheotomy and laparotomy, gastric effluents were collected by washout technique with a 15 minutes interval. The total titrable acid was measured by manual titrator, and the total pepsin content was measured by Anson's method. Vagal electrical stimulation was used to stimulate the secretion of acid and pepsin.. Heroin results in a significant decrease in total basal acid and pepsin secretions (4.10 +/- 0.18 mmol/15 minutes versus 2.40 +/- 0.16 mmol/15 minutes for acid, p<0.01, and 3.63 +/- 0.18 mg/15 minutes versus 3.11+/- 0.18 mg/15 minutes for pepsin, p<0.05). But, it does not produce any significant changes in acid and pepsin secretions in vagotomized condition. Heroin also causes a significant decrease in vagal-electrically stimulated acid and pepsin secretions (14.70 +/- 0.54 mmol/15 minutes versus 4.30 +/- 0.21 mmol/15 minutes for acid, p<0.01, and 3.92 +/-0.16 mg/15 minutes versus 3.37+/- 0.16 mg/15 minutes for pepsin, p<0.05).. Heroin consumption decreases the total gastric basal and vagus stimulation of acid and pepsin secretion, but not in vagotomized condition. Heroin may decrease acid secretion by inhibiting vagal release of acetylcholine within the gastric wall. Other probable mechanisms include: presynaptic inhibition of acetylcholine release or depressing the vagal center, inhibition of pentagastrin induced acid secretion, inhibitory effects via central mechanisms, probably mediated by the opiate receptors. Further studies are needed to recognize the actual mechanism.

Topics: Animals; Basal Ganglia; Chronic Disease; Disease Models, Animal; Electric Stimulation; Female; Gastric Acid; Gastric Acidity Determination; Gastric Mucosa; Heroin; Heroin Dependence; Male; Pepsin A; Probability; Rats; Rats, Inbred Strains; Reference Values; Sensitivity and Specificity; Vagotomy; Vagus Nerve

It has been presumed that the combination of cocaine (COC)+heroin (HER) is more reinforcing than either of the two drugs alone, thus leading to their coadministration ("speedballing"). An alternative hypothesis is that HER serves to attenuate the undesired negative effects of COC. To test this notion, male Sprague-Dawley rats (n=31) were trained to run a straight alley for a daily intravenous (IV) injection of COC (1.0 mg/kg/injection) for 14 trials. Studies in our laboratory have shown that such animals begin to exhibit approach-avoidance behaviors ("retreats") stemming from concurrent positive and negative associations with the goal box (which, in turn, are the result of COC's immediate rewarding and subsequent dysphoric actions). Thus, retreats can be used as a reliable index of COC's anxiogenic side effects. Following 14 COC-reinforced trials, animals were split into three groups matched on mean retreat frequency. One group (n=11) received IV COC (1.0 mg/kg/injection) for seven additional trials; the remaining two groups (n=10 each) received an IV injection of COC mixed in a single solution with either a low dose (0.025 mg/kg/injection) or a high dose (0.1 mg/kg/injection) of HER. It was hypothesized that adding HER would attenuate the negative consequences of COC administration and thereby produce a reliable decrease in the occurrence of retreats. The resulting data were consistent with this hypothesis, suggesting that "speedballing" in human addicts may be motivated by a desire to reduce the negative impact of COC use.

Topics: Animals; Avoidance Learning; Cocaine; Conditioning, Operant; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Interactions; Heroin; Male; Rats; Rats, Sprague-Dawley; Reinforcement, Psychology; Self Administration; Substance-Related Disorders

We examined the role of withdrawal in relapse to drug-seeking and drug-taking by testing the effects of opiate abstinence on extinction behaviour in rats trained to self-administer heroin. Male Long-Evans rats responded for IV heroin under a heterogeneous chain (VI 120 s; FR 1) schedule in which "seeking" responses preceded a "taking" response which produced a drug infusion. Responding was then measured in extinction during acute (6, 12, and 24 hr) and prolonged (3, 6, 12, and 25 day) abstinence. Sucrose consumption and somatic withdrawal were assessed at each testing period. During acute abstinence, responses on the "drug-seeking" manipulandum increased at 24 hr, whereas responses on the "drug-taking" manipulandum increased at 6 hr. Both responses were elevated during the 12-day abstinence test. Sucrose consumption was reduced and somatic withdrawal scores were increased in opiate-experienced rats at each test period. Results suggest that heroin abstinence has different effects on drug-seeking and drug-taking and that these effects do not temporally coincide with somatic measures of opioid withdrawal.

Topics: Acute Disease; Animals; Conditioning, Operant; Disease Models, Animal; Extinction, Psychological; Heroin; Heroin Dependence; Male; Rats; Rats, Long-Evans; Self Administration; Substance Withdrawal Syndrome

Studies in rats have shown that intermittent footshock stress reinstates drug seeking after prolonged drug-free periods. Recently, we found that another environmental stressor, acute 1 d food deprivation, potently reinstates heroin seeking in rats. Here we report that this effect of food deprivation can be blocked by leptin, a hormone involved in the regulation of energy balance and food intake. Rats were trained to self-administer heroin (0.05-0.1 mg/kg, i.v., per infusion, three 3 hr sessions per day) for 8-10 d. The heroin-reinforced behavior was then extinguished for 10-13 d, during which lever presses had no reinforced consequences. Subsequently, rats were tested for reinstatement after 1 d of food deprivation (experiment 1) or exposure to intermittent footshock (15 min, 0.6 mA) and heroin priming injections (0.25 mg/kg, s.c.) (experiment 2). Acute food deprivation reinstated heroin seeking, an effect that was attenuated by leptin (2 or 4 microgram/rat, i.c.v.; two infusions, given 21 hr and 20-30 min before the start of the test sessions). In contrast, leptin had no effect on reinstatement of heroin seeking induced by intermittent footshock or priming injections of heroin. These data indicate that food deprivation can provoke relapse to heroin seeking via a leptin-dependent mechanism, which is not involved in relapse induced by footshock stress or reexposure to heroin.

Topics: Animals; Behavior, Animal; Disease Models, Animal; Electroshock; Food Deprivation; Heroin; Heroin Dependence; Injections, Intraventricular; Injections, Subcutaneous; Leptin; Male; Rats; Rats, Long-Evans; Secondary Prevention; Self Administration; Stress, Physiological; Treatment Outcome

The present study was designed to explore the relationship between the cannabinoid and opioid receptors in animal models of opioid-induced reinforcement. The acute administration of SR141716A, a selective central cannabinoid CB1 receptor antagonist, blocked heroin self-administration in rats, as well as morphine-induced place preference and morphine self-administration in mice. Morphine-dependent animals injected with SR141716A exhibited a partial opiate-like withdrawal syndrome that had limited consequences on operant responses for food and induced place aversion. These effects were associated with morphine-induced changes in the expression of CB1 receptor mRNA in specific nuclei of the reward circuit, including dorsal caudate putamen, nucleus accumbens, and septum. Additionally, the opioid antagonist naloxone precipitated a mild cannabinoid-like withdrawal syndrome in cannabinoid-dependent rats and blocked cannabinoid self-administration in mice. Neither SR141716A nor naloxone produced any intrinsic effect on these behavioral models. The present results show the existence of a cross-interaction between opioid and cannabinoid systems in behavioral responses related to addiction and open new strategies for the treatment of opiate dependence.

Topics: Animals; Avoidance Learning; Cannabinoids; Caudate Nucleus; Conditioning, Operant; Disease Models, Animal; Heroin; Heroin Dependence; Male; Mice; Morphine; Morphine Dependence; Naloxone; Narcotic Antagonists; Nucleus Accumbens; Piperidines; Putamen; Pyrazoles; Rats; Rats, Wistar; Receptors, Cannabinoid; Receptors, Drug; Receptors, Opioid; Rimonabant; RNA, Messenger; Self Administration; Septum of Brain

The authors investigated several features of polydrug use in rats. Heroin and cocaine were self-administered following responses on different levers, with only 1 drug and 1 lever available on alternate days of training. Four doses of each drug (heroin: 25, 50, 100, and 200 microg/kg/infusion; cocaine: 0.25, 0.5, 1, and 2 mg/kg/infusion) were tested, and each rat was exposed to a single dose combination. Rats readily developed drug-specific and dose-related responding. During extinction, rats displayed a significant bias for responding on the cocaine- associated lever. Priming injections of either cocaine (20 mg/kg) or heroin (0.25 mg/kg) reinstated responding that was selective for the lever previously associated with each drug. These results suggest that in this type of polydrug use, drugs have the capacity to activate drug-seeking behavior selectively oriented toward stimuli previously associated with their administration.

Topics: Animals; Cocaine; Cocaine-Related Disorders; Conditioning, Operant; Disease Models, Animal; Dose-Response Relationship, Drug; Extinction, Psychological; Heroin; Heroin Dependence; Infusions, Intravenous; Male; Narcotics; Rats; Rats, Long-Evans; Recurrence; Self Administration

Previous experiments have demonstrated that presenting independently established discriminative stimuli in compound can substantially increase operant responding maintained by food reinforcement or shock avoidance. Recently, this phenomenon was also shown to occur with cocaine self-administration. The present study further assessed the generality of these stimulus-compounding effects by systematically replicating them with heroin self-administration. Rats' nose-poke responses produced intravenous heroin (0.025 mg/kg per infusion) on a variable-ratio schedule when either a tone or a light was present. In the absence of these stimuli, responding was not reinforced. Once discriminative control by the tone and light had been established, the stimuli were presented in compound under extinction (with heroin discontinued) or maintenance conditions (with heroin available during test-stimulus presentations). In extinction, the tone-light compound increased responding approximately threefold compared to tone or light alone. Under maintenance conditions, compounding increased heroin intake approximately twofold. These effects closely matched those obtained earlier with cocaine. This consistency across pharmacological classes and across drug and nondrug reinforcers further confirms that (a) self-administered drugs support conditioning and learning in a manner similar to that supported by other reinforcers; and (b) multiple drug-related cues interact in lawful and predictable ways to affect drug seeking and consumption.

Topics: Animals; Behavior, Animal; Disease Models, Animal; Heroin; Heroin Dependence; Male; Motivation; Rats; Rats, Sprague-Dawley; Reinforcement, Psychology; Self Administration

The present studies employ multitudinous approaches in order to overcome the methodological obstacles in the understanding of the relationship between neurochemical alterations and behavioral deficits induced by heroin during prenatal development. Mice were exposed prenatally to heroin via daily subcutaneous injections of 10 mg/kg, on gestation days 9-18. At age 50 days, the heroin-exposed offspring displayed behavioral deficits as assessed in the eight-arm and Morris mazes, pointing to possible alteration in the septohippocampal cholinergic innervations. Biochemically there was increased presynaptic activity of these innervations as attested to by the increased [3H]hemicholinium-3 (HC-3) binding sites and by K+-stimulated inositol phosphate (IP) formation. Postsynaptically, there was global hyperactivation along the different components of the nerve conduction cascade, including an increase in M1 muscarinic receptor Bmax, a general increase in G-proteins (GP) including the most relevant, G subtype, and an increase in IP formation and in basal protein kinase C (PKC) activity. However, there was desensitization of PKC activity in response to cholinergic agonist in the heroin-exposed offspring. Transplantation of normal embryonic cholinergic cells to the impaired hippocampus reversed the behavioral deficits and both the pre- and postsynaptic hyperactivity and resensitized PKC activity. To support and further strengthen the findings of the neural grafting study, correlation of the heroin-induced behavioral deficits with the biochemical alterations, done within individuals, was applied. The results showed high r values for IP formation, basal PKC, and PKC desensitization. The r values for HC-3 binding were statistically significant but relatively low. Taken together, the findings of the neural grafting and correlation studies bring us closer to understanding the relationship between the prenatal heroin-induced biochemical and behavioral changes. However, mammalian models possess the inherent methodological hindrances, stemming from possible maternal effects. To provide a control for these confounding variables, a chick embryo model was applied in which filial imprinting, a behavior related to a specific hyperstriatal nucleus, served as an endpoint. Heroin was administered to developing chick embryos by injecting the eggs (20 mg/kg) on incubation days (ID) 0 or 5. Prehatch exposure to heroin markedly diminished the ability for filial imprinting in the hatched

Topics: Acetylcholine; Animals; Behavioral Symptoms; Brain Chemistry; Brain Tissue Transplantation; Chick Embryo; Chickens; Disease Models, Animal; Female; Hemicholinium 3; Heroin; Hippocampus; Imprinting, Psychological; Male; Maze Learning; Mice; Narcotics; Pregnancy; Prenatal Exposure Delayed Effects; Protein Kinase C; Septum Pellucidum; Statistics as Topic; Time Factors

Abuse of cocaine-opiate combinations ("speedballs") reported clinically was simulated in a rhesus monkey model of simultaneous cocaine and heroin self-administration. The reinforcing effects of nine cocaine-heroin combinations (cocaine [0.001, 0.01 and 0.10 mg/kg per injection i.v.] and heroin [0.0001, 0.001 and 0.01 mg/kg per injection i.v.]) were evaluated for 10 days on a second-order fixed ratio of 4 (variable ratio of 16:S) schedule and compared with self-administration of cocaine and heroin alone. Dose-effect curves for cocaine-heroin combinations usually were similar to those for cocaine and heroin alone, and intermediate doses maintained equivalent high levels of drug self-administration. No toxic effects were observed. In drug discrimination studies, cocaine (0.004-1.3 mg/kg) substitution resulted in a dose-dependent generalization to the training dose (0.4 mg/kg i.m.) in all five monkeys. Heroin substitution (0.01-1.0 mg/kg i.m.) resulted in dose-dependent and complete generalization to cocaine in three of five monkeys. Heroin pretreatment (0.1-0.18 mg/kg i.m.) did not change the cocaine discrimination dose-effect curve. Pretreatment with an opiate antagonist, quadazocine (0.1 mg/kg i.m.), had no effect on the discriminative stimulus effects of cocaine but antagonized the cocaine-like discriminative stimulus effects of heroin. Pretreatment with a dopamine antagonist, flupenthixol (0.018 mg/kg), antagonized the discriminative stimulus effects of cocaine but did not affect the cocaine-like effects of heroin. These findings demonstrate the feasibility of maintaining self-administration of cocaine-heroin combinations and suggest that cocaine and heroin have similar reinforcing and discriminative stimulus effects in rhesus monkeys.

Topics: Animals; Azocines; Cocaine; Discrimination Learning; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Combinations; Food; Heroin; Macaca mulatta; Male; Narcotic Antagonists; Narcotics; Self Administration; Substance-Related Disorders

The effects of ascending and descending doses of buprenorphine (0.014-0.789 mg/kg/day) and methadone (0.179-11.86 mg/kg/day) on opiate and food intake were studied in Macaque monkeys over 195 to 245 days. Food (1-g banana pellets) and i.v. drug self-administration (heroin 0.01 or 0.02 mg/kg/injection or Dilaudid 0.02 mg/kg/injection) were maintained on a second-order schedule of reinforcement [FR 4 (VR 16:S)]. Buprenorphine (0.282-0.789 mg/kg/day) produced a significant suppression of opiate self-administration at 2.5 to 7 times the dose shown to be effective in human opiate abusers (P less than .05-.001). Methadone (1.43-11.86 mg/kg/day) did not suppress opiate self-administration in four of five monkeys across a dose range equivalent to 100 to 800 mg/day in man. The distribution of opiate self-administration across drug sessions did not account for the absence of methadone suppression as monkeys took 43% of the total daily opiate injections during the first daily drug session, 2.5 hr after methadone administration. During buprenorphine maintenance, food intake remained stable or increased significantly above base-line levels. Methadone maintenance was associated with significant decrements in food intake in four of five monkeys. Buprenorphine appeared to be significantly more effective in suppressing opiate self-administration than methadone across the dose range studied. Buprenorphine had none of the toxic side effects (seizures, respiratory depression, profound psychomotor retardation) associated with high doses of methadone over 6 to 8 months of daily drug treatment. These data are consistent with clinical studies of buprenorphine effects on heroin self-administration in human opiate addicts.

Topics: Animals; Buprenorphine; Depression, Chemical; Disease Models, Animal; Feeding Behavior; Heroin; Humans; Hydromorphone; Macaca mulatta; Macaca nemestrina; Methadone; Morphinans; Opioid-Related Disorders; Self Administration

A model of "overdose" deaths among heroin addicts is proposed which emphasizes recent findings concerning the contribution of drug-associated environmental cues to drug tolerance. Results of animal experiments performed to evaluate this model suggest that conditioned drug-anticipatory responses, in addition to pharmacological factors, affect heroin-induced mortality.

Topics: Animals; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Tolerance; Environment; Heroin; Humans; Male; Rats; Substance-Related Disorders

Topics: 5-Hydroxytryptophan; Animals; Behavior, Animal; Delayed-Action Preparations; Disease Models, Animal; Drug Synergism; Heroin; Humans; Male; Morphine; Morphine Dependence; Motor Activity; Naloxone; Rats; Substance Withdrawal Syndrome; Theophylline