Differential role of delta-opioid receptors in the development and expression of behavioral sensitization to cocaine.
The present study was designed to determine whether the selective delta-opioid receptor antagonist naltrindole hydrochloride can prevent the expression and development of sensitization to the locomotor-activating effects of cocaine. Rats were sensitized to the motor stimulant effects of cocaine (20 mg/kg i.p. x 3 days). 48 h after withdrawal of pretreatment, rats were pretreated with naltrindole (0.1-1.0 mg/kg s.c.) or its vehicle and 15 min later challenged with either saline or the sensitizing dose of cocaine. In a second set of experiments, naltrindole (0.1-1.0 mg/kg s.c.) or its vehicle were given in combination with either saline or cocaine (20 mg/kg i.p.) for 3 days. Activity in response to saline and to cocaine (20 mg/kg i.p.) was assessed on days 4 and 5, respectively. Additional experiments determined whether naltrindole prevents the development of sensitization to the locomotor-activating effects of nicotine: naltrindole (0.3, 1.0 mg/kg s.c.) or its vehicle were given in combination with nicotine (0.6 mg/kg s.c.) for 3 days. Naltrindole blocked the development but not expression of sensitization to the locomotor-activating effects of cocaine. In contrast, naltrindole failed to modify nicotine-induced sensitization in nicotine-treated animals. These data suggest that delta-opioid receptors are involved in the development but not expression of behavioral sensitization to cocaine.
Heidbreder
C
C
National Institute of Health (NIH), National Institute on Drug Abuse (NIDA), Preclinical Pharmacology Laboratory, Baltimore, MD 21224, USA.
Shoaib
M
M
Shippenberg
T S
TS
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D003042:Cocaine / Q000494:pharmacology*; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology*; D009538:Nicotine / Q000494:pharmacology; D018722:Nicotinic Agonists / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017465:Receptors, Opioid, delta / Q000187:drug effects / Q000502:physiology*
D009292:Narcotic Antagonists; D009294:Narcotics; D018722:Nicotinic Agonists; D017465:Receptors, Opioid, delta; D009271:Naltrexone; D009538:Nicotine; C055382:naltrindole; D003042:Cocaine