fg-9041 and Substance-Withdrawal-Syndrome

Rostromedial tegmental nucleus (RMTg) GABA neurons exert a primary inhibitory drive onto midbrain dopamine neurons and are excited by a variety of aversive stimuli. There is, however, little evidence that the RMTg-ventral tegmental area (VTA)-nucleus accumbens shell (Acb) circuit plays a role in the aversive consequences of alcohol withdrawal. This study was performed in adult male Long-Evans rats at 48-h withdrawal from chronic alcohol drinking in the intermittent schedule. These rats displayed clear anhedonia and depression-like behaviors, as measured with the sucrose preference, and forced swimming tests. These aberrant behaviors were accompanied by a substantial increase in cFos expression in the VTA-projecting RMTg neurons, identified by a combination of immunohistochemistry and retrograde-tracing techniques. Pharmacological or chemogenetic inhibition of RMTg neurons mitigated the anhedonia and depression-like behaviors. Ex vivo electrophysiological data showed that chemogenetic inactivation of RMTg neurons reduced GABA release and accelerated spontaneous firings of VTA dopamine neurons. Finally, using a functional hemispheric disconnection procedure, we demonstrated that inhibition of unilateral RMTg, when combined with activation of D1 and D2 dopamine receptors in the contralateral (but not ipsilateral) Acb, mitigated the anhedonia and depression-like behaviors in alcohol-withdrawal rats. These data show that the integrity in the RMTg-VTA-Acb pathway in a single hemisphere is sufficient to elicit depression-like behavior during ethanol-withdrawal. Overall, the present results reveal that the RMTg-VTA-Acb pathway plays a crucial role in the depression-like behavior in animals undergoing alcohol withdrawal, further advocating the RMTg as a potential therapeutic target for alcoholism.

Topics: 2-Amino-5-phosphonovalerate; 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; Animals; Behavior, Animal; Clozapine; Dopaminergic Neurons; Ethanol; gamma-Aminobutyric Acid; Male; Microinjections; Neural Inhibition; Neural Pathways; Nucleus Accumbens; Proto-Oncogene Proteins c-fos; Quinoxalines; Quinpirole; Rats; Substance Withdrawal Syndrome; Tegmentum Mesencephali; Ventral Tegmental Area

Alcoholism and psychiatric disorders like depression and anxiety are often comorbid. Although the mechanisms underlying this comorbidity are unclear, emerging evidence suggests that maladaptation of the glial glutamate transporter GLT-1 may play a role. Findings from animal and human studies have linked aversive states, including those related to drugs of abuse and depression, to aberrant activity in the lateral habenula (LHb). The relationship between GLT-1 maladaptation, LHb activity, and abnormal behaviors related to alcohol withdrawal, however, remains unknown. Here we show that dihydrokainic acid (DHK), a GLT-1 blocker, potentiated glutamatergic transmission to LHb neurons in slices from ethanol naïve rats; this potentiation, though, was not observed in slices from rats withdrawn from repeated in vivo ethanol administration, suggesting reduced GLT-1 function. Furthermore, GLT-1 protein expression was reduced in the LHb of withdrawn rats. This reduction was restored by systemic administration of ceftriaxone, a β-lactam antibiotic known to increase GLT-1 expression. Systemic ceftriaxone treatment also normalized the hyperactivity of LHb neurons in slices from withdrawn rats, which was reversed by bath-applied DHK. Finally, systemic administration of ceftriaxone alleviated depression- and anxiety-like behaviors, which was fully blocked by intra-LHb administrations of DHK, suggesting that GLT-1's function in the LHb is critical. These findings highlight the significant role of LHb astrocytic GLT-1 in the hyperactivity of LHb neurons, and in depressive- and anxiety-like behaviors during ethanol withdrawal. Thus, GLT-1 in the LHb could serve as a therapeutic target for psychiatric disorders comorbid with ethanol withdrawal.

Topics: Alcoholism; Amino Acid Transport System X-AG; Animals; Antidepressive Agents; Anxiety; Ceftriaxone; Central Nervous System Depressants; Depression; Ethanol; Excitatory Amino Acid Agonists; Excitatory Postsynaptic Potentials; Habenula; In Vitro Techniques; Kainic Acid; Male; Maze Learning; Nerve Tissue Proteins; Quinoxalines; Rats; Rats, Sprague-Dawley; Sodium Channel Blockers; Substance Withdrawal Syndrome; Swimming; Tetrodotoxin

The medial prefrontal cortex (mPFC) is a key neural region involved in opiate-related reward memory processing. AMPA receptor transmission in the mPFC modulates opiate-related reward memory processing, and chronic opiate exposure is associated with alterations in intra-mPFC AMPA receptor function.. The objectives of this study were to examine how pharmacological blockade of AMPA receptor transmission in the prelimbic (PLC) division of the mPFC may modulate opiate reward memory acquisition and whether opiate exposure state may modulate the functional role of intra-PLC AMPA receptor transmission during opiate reward learning.. Using an unbiased conditioned place preference (CPP) procedure in rats, we performed discrete, bilateral intra-PLC microinfusions of the AMPA receptor antagonist, 6,7-dinitroquinoxaline-2,3-dione, prior to behavioral morphine CPP conditioning, using sub-reward threshold conditioning doses of either systemic (0.05 mg/kg; i.p.) or intra-ventral tegmental area (VTA) morphine (250 ng/0.5 μl).. We show that, in both opiate-naïve and opiate-dependent states, intra-PLC blockade of AMPA receptor transmission, but not the infralimbic cortex, increases the behavioral reward magnitude of systemic or intra-VTA morphine. This effect is dependent on dopamine (DA)ergic signaling because pre-administration of cis-(Z)-flupenthixol-dihydrochloride (α-flu), a broad-spectrum dopamine receptor antagonist, blocked the morphine-reward potentiating effects of AMPA receptor blockade.. These findings suggest a critical role for intra-PLC AMPA receptor transmission in the processing of opiate reward signaling. Furthermore, blockade of AMPA transmission specifically within the PLC is capable of switching opiate reward processing to a DA-dependent reward system, independently of previous opiate exposure history.

Topics: Analgesics, Opioid; Animals; Conditioning, Psychological; Dose-Response Relationship, Drug; Excitatory Amino Acid Antagonists; Male; Microinjections; Morphine; Prefrontal Cortex; Quinoxalines; Rats; Rats, Sprague-Dawley; Receptors, AMPA; Reward; Substance Withdrawal Syndrome; Ventral Tegmental Area

Withdrawal anxiety is a significant factor contributing to continued alcohol abuse in alcoholics. This anxiety is long-lasting, can manifest well after the overt physical symptoms of withdrawal, and is frequently associated with relapse in recovering alcoholics. The neurobiological mechanisms governing these withdrawal-associated increases in anxiety are currently unknown. The basolateral amygdala (BLA) is a major emotional center in the brain and regulates the expression of both learned fear and anxiety. Neurotransmitter system alterations within this brain region may therefore contribute to withdrawal-associated anxiety. Because evidence suggests that glutamate-gated neurotransmitter receptors are sensitive to acute ethanol exposure, we examined the effect of chronic intermittent ethanol (CIE) and withdrawal (WD) on glutamatergic synaptic transmission in the BLA. We found that slices prepared from CIE and WD animals had significantly increased contributions by synaptic NMDA receptors. In addition, CIE increased the amplitude of AMPA-receptor-mediated spontaneous excitatory postsynaptic currents (sEPSCs), whereas only WD altered the amplitude and kinetics of tetrodotoxin-resistant spontaneous events (mEPSCs). Similarly, the frequency of sEPSCs was increased in both CIE and WD neurons, although only WD increased the frequency of mEPSCs. These data suggest that CIE and WD differentially alter both pre- and postsynaptic properties of BLA glutamatergic synapses. Finally, we show that microinjection of the AMPA-receptor antagonist, DNQX, can attenuate withdrawal-related anxiety-like behavior. Together, our results suggest that increased glutamatergic function may contribute to anxiety expressed during withdrawal from chronic ethanol.

Topics: Administration, Inhalation; Amygdala; Animals; Anxiety; Central Nervous System Depressants; Data Interpretation, Statistical; Electrophysiology; Ethanol; Excitatory Amino Acid Antagonists; Excitatory Postsynaptic Potentials; Glutamates; Male; Microinjections; Neurotransmitter Agents; Patch-Clamp Techniques; Quinoxalines; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Substance Withdrawal Syndrome; Synapses; Synaptic Transmission; Tetrodotoxin

We have previously reported that acute and chronic nicotine exposure lower the threshold for long-term potentiation (LTP) induction in the rat hippocampal CA1 region, and acute application of nicotine in the chronic-nicotine-treated hippocampus further reduces the threshold. However, it is unknown how withdrawal from chronic nicotine exposure affects the induction of LTP. Here, we show that, following nicotine withdrawal, the threshold for LTP induction fluctuates before returning to the basal level and acute nicotine is no longer effective in lowering the threshold at 4 days after withdrawal. Chronic nicotine-induced enhancement of N-methyl-d-aspartate receptor responses slowly diminishes and returns to the control level by 8 days of withdrawal. In 4-day-withdrawn hippocampi, there is functional up-regulation of postsynaptic alpha7 nicotinic acetylcholine receptors (nAChRs) on interneurons in the stratum radiatum, whereas the release of gamma-aminobutyric acid from their terminals is reduced. In both control and chronic nicotine-exposed hippocampi, acute nicotine depresses monosynaptic inhibitory postsynaptic currents recorded in pyramidal cells but has almost no effect at 4 days of withdrawal. The lack of effect is due, at least in part, to the loss of a presynaptic nicotine effect. These withdrawal-induced changes are accompanied by decreases in normal nicotine-induced enhancement of N-methyl-d-aspartate receptor responses, which may be responsible for the lack of acute nicotine-mediated facilitation of LTP induction in 4-day-withdrawn hippocampi. These withdrawal-induced changes may contribute to the cellular basis of unpleasant withdrawal symptoms and, thus, nicotine dependence.

Topics: Animals; Azetidines; Dose-Response Relationship, Drug; Drug Administration Schedule; Drug Interactions; Electric Stimulation; Excitatory Amino Acid Antagonists; Excitatory Postsynaptic Potentials; Female; GABA Antagonists; Hippocampus; Inhibitory Postsynaptic Potentials; Long-Term Potentiation; Male; Nicotine; Nicotinic Agonists; Picrotoxin; Quinoxalines; Rats; Substance Withdrawal Syndrome; Time Factors; Up-Regulation

The present study sought to assess whether the blockade of ionotropic glutamate receptors in the ventral tegmental area could modulate morphine withdrawal in morphine-dependent rats and the expression of stable DeltaFosB isoforms in the nucleus accumbens during morphine withdrawal. Rats were injected (i.p.) with increasing doses of morphine for 1 week to develop physical dependence, and withdrawal was then precipitated by one injection of naloxone (2 mg/kg, i.p.). Abstinence signs such as jumping, wet-dog shake, writhing posture, weight loss, and Gellert-Holtzman scale score were recorded to evaluate naloxone-induced morphine withdrawal. Two ionotropic glutamate receptor antagonists, dizocilpine (MK-801) and 6, 7-dinitroquinnoxaline-2, 3-dione (DNQX), were microinjected unilaterally into the ventral tegmental area 30 min before naloxone precipitation. A second injection of naloxone (2 mg/kg i.p.) was given 1 h after the first naloxone injection to sustain a maximal level of withdrawal so that the expression of stable DeltaFosB isoforms in the nucleus accumbens could be measured. This would enable determination of the correlation between the MK-801 or DNQX-induced decrease in somatic withdrawal signs and the change in neuronal activity in the nucleus accumbens. The results showed that both MK-801 and DNQX significantly alleviated all symptoms of morphine withdrawal except for weight loss and reduced the expression of stable DeltaFosB isoforms within the nucleus accumbens. These data suggest that ionotropic glutamatergic neurotransmission in the ventral tegmental area regulates the levels of stable DeltaFosB isoforms in the nucleus accumbens, which play a very important role in modulating opiate withdrawal.

Topics: Animals; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Immunohistochemistry; Male; Microinjections; Morphine; Morphine Dependence; Naloxone; Nucleus Accumbens; Protein Isoforms; Proto-Oncogene Proteins c-fos; Quinoxalines; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Substance Withdrawal Syndrome; Synaptic Transmission; Ventral Tegmental Area

The present study sought to assess whether the blockade of ionotropic glutamate receptors in the ventral tegmental area (VTA) could modulate the morphine withdrawal in male Sprague-Dawley rats. The effects of dizocilpine (MK-801) or 6,7-dinitroquinnoxaline-2,3-dione (DNQX), ionotropic glutamate receptor antagonists, microinjected unilaterally into the VTA 30 min before naloxone [2 mg/kg, intraperitoneally (i.p.)] administration on the morphine withdrawal were assessed. Morphine dependence was developed with increasing morphine injection (i.p.), and morphine withdrawal was induced by injection of naloxone (2 mg/kg, i.p.). Jumping, wet-dog shakes, writhing posture, wall clamber, weight loss and Gellert-Holtzman scale were used as the indices to evaluate the intensity of morphine withdrawal. The results showed that unilateral microinjection of MK-801 or DNQX into the VTA significantly increased the incidence of wall clamber, had no effect on weight loss, and reduced all other symptoms of morphine withdrawal. These data suggest that the ionotropic glutamate receptors in the VTA are involved in mediating naloxone-precipitated opiate withdrawal.

Topics: Animals; Behavior, Animal; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Microinjections; Morphine; Naloxone; Narcotic Antagonists; Narcotics; Quinoxalines; Rats; Rats, Sprague-Dawley; Receptors, Glutamate; Substance Withdrawal Syndrome; Synaptic Transmission; Ventral Tegmental Area; Weight Loss

The effects of the excitatory amino acid (EAA) receptor antagonists MK-801 (non-competitive NMDA receptor antagonist), DNQX (competitive non-NMDA receptor antagonist) and 5,7-DCKA (antagonist of glycine site of NMDA receptor) have been examined on the naloxone (4 mg/kg, i.p.)-precipitated withdrawal jumping behaviour in morphine-dependent mice. The results indicate that withdrawal jumping behaviour in morphine-dependent mice was attenuated by all three EAA receptor antagonists, MK-801, DNQX and 5,7-DCKA. However, MK-801, DNQX and 5,7-DCKA inhibited the jumping behaviour in a relatively narrow dose range.

Topics: Animals; Behavior, Animal; Dizocilpine Maleate; Glycine; Kynurenic Acid; Male; Mice; Morphine Dependence; Naloxone; Quinoxalines; Receptors, Amino Acid; Receptors, Glycine; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter; Substance Withdrawal Syndrome