binaltorphimine and Substance-Withdrawal-Syndrome

Chronic intermittent alcohol vapor exposure leads to increased dynorphin (DYN) A-like peptide expression and heightened kappa-opioid receptor (KOR) signaling in the central nucleus of the amygdala (CeA) and these neuroadaptive responses differentiate alcohol-dependent from non-dependent phenotypes. Important for therapeutic development efforts is understanding the nature of the stimulus that drives dependence-like phenotypes such as escalated alcohol self-administration. Accordingly, the present study examined the impact of intra-CeA KOR antagonism on escalated operant alcohol self-administration and physiological withdrawal symptoms during acute withdrawal and protracted abstinence in rats previously exposed to chronic intermittent alcohol vapor. Following operant training, rats were implanted with intra-CeA guide cannula and exposed to long-term intermittent alcohol vapor exposure that resulted in escalated alcohol self-administration and elevated physiological withdrawal signs during acute withdrawal. Animals received intra-CeA infusions of the KOR antagonist nor-binaltorphimine (nor-BNI; 0, 2, 4, or 6 μg) prior to operant alcohol self-administration sessions and physiological withdrawal assessment during acute withdrawal and protracted abstinence. The results indicated that site-specific KOR antagonism in the CeA ameliorated escalated alcohol self-administration during both acute withdrawal and protracted abstinence test sessions, whereas KOR antagonism had no effect on physiological withdrawal scores at either time point. These results dissociate escalated alcohol self-administration from physiological withdrawal symptoms in relation to KOR signaling in the CeA and help clarify the nature of the stimulus that drives escalated alcohol self-administration during acute withdrawal and protracted abstinence.

Topics: Administration, Intranasal; Alcoholism; Animals; Central Amygdaloid Nucleus; Central Nervous System Depressants; Conditioning, Operant; Disease Models, Animal; Dose-Response Relationship, Drug; Ethanol; Male; Motivation; Naltrexone; Narcotic Antagonists; Rats, Wistar; Receptors, Opioid, kappa; Self Administration; Substance Withdrawal Syndrome

The present study was undertaken to determine whether acute physical dependence occurred in guinea-pigs in vivo and guinea-pig isolated ileum following a single dose of the kappa-opioid receptor agonist U50,488H. Administration of naloxone hydrochloride, 15 and 30 mg/kg s.c., to guinea-pigs treated 1 h before with U50,488H, 10 mg/kg s.c., induced increased locomotor activity accompanied by behavioural responses which differed from those previously found in this species with morphine withdrawal. Nor-binaltorphimine, 10 mg/kg s.c., given 1 h after administration of U50,488H, 10 mg/kg s.c., produced a small but significant increase in locomotor activity but no other withdrawal behaviours. The morphine withdrawal response was not significantly affected by U50,488H, 1 or 10 mg/kg s.c. On the guinea-pig isolated ileum, nor-binaltorphimine, 1 microM, produced a withdrawal contracture following 2 min contact of the ileum with U50,488H 1 microM. U50,488H, 1 microM, abolished the [Met5]enkephalin withdrawal response of the ileum. It is concluded that dependence occurs following activation of kappa-opioid receptors, which is largely non-morphine-like in the central nervous system, but which is morphine-like in the enteric nervous system.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics, Opioid; Animals; Behavior, Animal; Female; Guinea Pigs; Ileum; In Vitro Techniques; Male; Morphine Dependence; Motor Activity; Muscle Contraction; Muscle, Smooth; Naloxone; Naltrexone; Pyrrolidines; Receptors, Opioid, kappa; Substance Withdrawal Syndrome; Substance-Related Disorders

Butorphanol has been shown to act on mu-, delta-, and kappa-opioid receptors. However, the relative involvement of different opioid receptor subtypes in butorphanol dependence is not known. In the present study, nor-binaltorphimine, a long-acting non-peptide kappa-opioid receptor antagonist, was employed to mask central kappa-opioid receptors before and during the induction of butorphanol dependence in rats, so that the involvement of kappa-opioid receptors could be elucidated. The results revealed that treatment with nor-binaltorphimine markedly blocked naloxone-precipitated withdrawal signs of escape behavior, teeth-chattering, wet shakes, ptosis, body weight loss, and hypothermia at all doses tested, and attenuated the withdrawal symptoms of forepaw tremors (24 nmol: P < 0.001) and diarrhea (12 nmol: P < 0.05; 24 nmol: P < 0.01). In contrast, nor-binaltorphimine had no effect on yawning, ejaculation, nor urination in butorphanol-infused rats undergoing withdrawal. Three days of butorphanol infusion significantly increased KD values (in the cortex and striatum), decreased Bmax (in the cortex only) of [3H]U-69,593 binding, and shifted Ki of nor-binaltorphimine against [3H]U-69,593 (4.5 nM) binding in the cortex by more than 10-fold. Treatment with nor-binaltorphimine blocked the effects of butorphanol on kappa-opioid receptors. It is therefore concluded that kappa-opioid receptors are involved in mediating escape behavior, teeth-chattering, wet shakes, forepaw tremors, ptosis, diarrhea, weight loss, and hypothermia in butorphanol-dependent rats undergoing withdrawal. Furthermore, kappa-opioid receptors become desensitized to agonists (in the cortex and striatum), down-regulated (in the cortex), and supersensitive to antagonists in butorphanol-dependent rats.

Topics: Animals; Benzeneacetamides; Body Temperature; Body Weight; Butorphanol; Diarrhea; Down-Regulation; Drug Administration Schedule; Escape Reaction; Male; Naltrexone; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Substance Withdrawal Syndrome; Substance-Related Disorders; Tremor