cp-154526 and Morphine-Dependence

Intense associative memories develop between drug-paired contextual cues and the drug withdrawal associated aversive feeling. They have been suggested to contribute to the high rate of relapse. Our study was aimed to elucidate the involvement of hypothalamic-pituitary-adrenocortical (HPA) axis activity in the expression and extinction of aversive memory in Swiss and C57BL/6J (B6) mice. The animals were rendered dependent on morphine by i.p. injection of increasing doses of morphine (10-60 mg/kg). The negative state associated with naloxone (1 mg/kg s.c.) precipitated morphine withdrawal was examined by using conditioned place aversion (CPA) paradigm. B6 mice obtained a higher aversion score and took longer to extinguish the aversive memory than Swiss mice. In addition, corticosterone levels were increased after CPA expression. Moreover, corticosterone levels were decreased during CPA extinction in Swiss mice without changes in B6 mice. Pre-treatment with the selective CRF1 receptor antagonist CP-154,526 before naloxone, impaired morphine-withdrawal aversive memory acquisition and decreased the extinction period. CP-154,526 also antagonized the increased levels of corticosterone observed after CPA expression in Swiss mice, without any changes in B6 mice. These results indicate that HPA axis could be a critical factor governing opioid withdrawal memory storage and retrieval, but in a strain or stock-specific manner. The differences observed between Swiss and B6 mice suggest that the treatment of addictive disorders should consider different individual predisposition to associate the aversive learning with the context.

Topics: Animals; Avoidance Learning; Conditioning, Operant; Extinction, Psychological; Hypothalamo-Hypophyseal System; Male; Memory; Mice; Mice, Inbred C57BL; Morphine; Morphine Dependence; Naloxone; Narcotic Antagonists; Narcotics; Pituitary-Adrenal System; Pyrimidines; Pyrroles; Receptors, Corticotropin-Releasing Hormone; Substance Withdrawal Syndrome

Different neurotransmitter systems are involved in behavioural and molecular responses to morphine. The brain stress system is activated by acute administration of drugs of abuse, being CRF the main neuropeptide of this circuitry. In this study we have studied the role of CRF1R in the rewarding effects of morphine using the CPP paradigm. For that, animals were treated with a CRF1R antagonist (CP-154,526) or vehicle during 6 days. Thirty min after receiving the antagonist, mice were injected with morphine on the same days that CP-154,526 was administered; another group received saline on the same days that vehicle was administered, and both groups were immediately conditioned. Control animals received vehicle and saline every day. On day 7, animals were tested for morphine-induced CPP. c-Fos, TH and OXA immunohistochemistry, NA turnover (HPLC), and corticosterone plasma concentration (RIA) were evaluated. Administration of a CRF1R antagonist CP-154,526 blocked the morphine-induced CPP and the increased NA turnover in the NAc in morphine-paired mice. CP-154-526 antagonised the enhancement in c-Fos expression evoked by morphine-induced CPP in the VTA and NAc, and the activation of the orexinergic neurons in the LLH. Present work demonstrates that morphine-induced CPP activates different brain areas involved in reward, and points out a critical role of CRF1R in molecular changes involved in morphine-conducted behaviours. Thus, our study supports a therapeutic potential of CRF1R antagonists in addictive disorders.

Topics: Animals; Conditioning, Operant; Hormone Antagonists; Locus Coeruleus; Male; Mice; Morphine; Morphine Dependence; Narcotics; Neurons; Nucleus Accumbens; Pyrimidines; Pyrroles; Random Allocation; Receptors, Corticotropin-Releasing Hormone; Reward; Spatial Behavior; Ventral Tegmental Area

Corticotropin-releasing factor (CRF) acts as neuro-regulator of the behavioral and emotional integration of environmental and endogenous stimuli associated with drug dependence. Thioredoxin-1 (Trx-1) is a functional protein controlling the redox status of several proteins, which is involved in addictive processes. In the present study, we have evaluated the role of CRF1 receptor (CRF1R) in the rewarding properties of morphine by using the conditioned place preference (CPP) paradigm. We also investigate the effects of the CRF1R antagonist, CP-154,526, on the morphine CPP-induced activation of CRF neurons, CREB phosphorylation and Trx expression in paraventricular nucleus (PVN) and dentate gyrus (DG) of the mice brain. CP-154,526 abolished the acquisition of morphine CPP and the increase of CRF/pCREB positive neurons in PVN. Moreover, this CRF1R antagonist prevented morphine-induced CRF-immunoreactive fibers in DG, as well as the increase in pCREB expression in both the PVN and DG. In addition, morphine exposure induced an increase in Trx-1 expression in DG without any alterations in PVN. We also observed that the majority of pCREB positive neurons in DG co-expressed Trx-1, suggesting that Trx-1 could activate CREB in the DG, a brain region involved in memory consolidation. Altogether, these results support the idea that CRF1R antagonist blocked Trx-1 expression and pCREB/Trx-1 co-localization, indicating a critical role of CRF, through CRF1R, in molecular changes involved in morphine associated behaviors.

Topics: Animals; Blotting, Western; Cells, Cultured; Conditioning, Psychological; Cyclic AMP Response Element-Binding Protein; Dentate Gyrus; Fluorescent Antibody Technique; Immunoenzyme Techniques; Male; Mice; Morphine; Morphine Dependence; Narcotics; Neurons; Phosphorylation; Pyrimidines; Pyrroles; Receptors, Corticotropin-Releasing Hormone; Thioredoxins

Stress induces the release of the peptide corticotropin-releasing factor (CRF) into the ventral tegmental area (VTA), and also increases dopamine (DA) levels in brain regions receiving dense VTA input. Since the role of stress in drug addiction is well established, the present study examined the possible involvement of CRF1 receptor in the interaction between morphine withdrawal and catecholaminergic pathways in the reward system. The effects of naloxone-precipitated morphine withdrawal on signs of withdrawal, hypothalamo-pituitary-adrenocortical (HPA) axis activity, dopamine (DA) and noradrenaline (NA) turnover in the nucleus accumbens (NAc) and activation of VTA dopaminergic neurons, were investigated in rats pretreated with vehicle or CP-154,526 (selective CRF1R antagonist). CP-154,526 attenuated the increases in body weight loss and suppressed some of withdrawal signs. Pretreatment with CRF1 receptor antagonist resulted in no significant modification of the increased NA turnover at NAc or plasma corticosterone levels that were seen during morphine withdrawal. However, blockade of CRF1 receptor significantly reduced morphine withdrawal-induced increases in plasma adrenocorticotropin (ACTH) levels, DA turnover and TH phosphorylation at Ser40 in the NAc. In addition, CP-154,526 reduced the number of TH containing neurons expressing c-Fos in the VTA after naloxone-precipitated morphine withdrawal. Altogether, these results support the idea that VTA dopaminergic neurons are activated in response to naloxone-precipitated morphine withdrawal and suggest that CRF1 receptors are involved in the activation of dopaminergic pathways which project to NAc.

Topics: Animals; Corticosterone; Dopamine; Male; Morphine; Morphine Dependence; Naloxone; Neurons; Norepinephrine; Nucleus Accumbens; Phosphorylation; Proto-Oncogene Proteins c-fos; Pyrimidines; Pyrroles; Rats; Rats, Sprague-Dawley; Receptors, Corticotropin-Releasing Hormone; Serine; Substance Withdrawal Syndrome; Tyrosine 3-Monooxygenase; Ventral Tegmental Area

The possible effects on the morphine withdrawal signs of the nonspecific corticotropin-releasing factor (CRF) receptor antagonist alpha-helical CRF, the selective CRF receptor subtype 1 antagonist CP-154,526 and the selective CRF receptor subtype 2 antagonist antisauvagine-30 (AS-30) were investigated in rats. The most withdrawal signs, including jumping, teeth chatter, writhing, shakes, lacrimation, piloerection, irritability and diarrhoea, were attenuated by pretreatment with alpha-helical CRF (10 microg i.c.v.) and CP-154,526 (30 mg/kg i.p.). However, no morphine withdrawal signs except for diarrhea were significantly affected by pretreatment with AS-30 (10 microg, i.c.v.). To investigate the possible role of different CRFR antagonists (alpha-helical CRF, CP-154,526 and AS-30) in relapse to opiate dependence, the 28-day extinction of morphine-conditioned place preference (CPP) was used. The morphine-CPP disappeared following a 28-day extinction and then was reactivated by a single injection of 10 mg/kg morphine. Pretreatment with alpha-helical CRF (10 microg, i.c.v.) and CP-154, 526 (30 mg/kg, i.p.) could significantly block this reactivation of morphine-CPP. In contrast, pretreatment with AS-30 (1 or 10 microg i. c.v.) did not affect this reactivation of morphine-CPP. The present study demonstrated that activation of the CRF receptor is involved in morphine withdrawal signs and relapse to morphine dependence, and that the role of CRF receptor subtypes 1 and 2 in withdrawal and reactivation of morphine dependence is not identical. CRF receptor subtype 1, but not subtype 2, is largely responsible for the action of the CRF system on opiate dependence. These results suggest that the CRF receptor antagonists, particularly the CRF receptor subtype 1 antagonist, might be of some value in the treatment and prevention of drug dependence.

Topics: Animals; Cerebral Ventricles; Choice Behavior; Corticotropin-Releasing Hormone; Hormone Antagonists; Injections, Intraventricular; Male; Morphine; Morphine Dependence; Naloxone; Peptide Fragments; Pyrimidines; Pyrroles; Rats; Rats, Sprague-Dawley; Receptors, Corticotropin-Releasing Hormone; Substance Withdrawal Syndrome