Intracerebroventricular naltrexone treatment attenuates acquisition of intravenous cocaine self-administration in rats.
The influence of centrally administered naltrexone, an opiate antagonist, on acquisition of intravenous cocaine self-administration behaviour in rats was examined. On five consecutive days, three hours per day, they could self-administer a cocaine solution (30 micrograms per infusion) through an indwelling cannula. Treatment consisted of daily injections of naltrexone (2 or 5 micrograms) or placebo into the lateral ventricle 30 minutes before testing. Naltrexone treatment dose dependently attenuated the rate of cocaine self-infusion. Both self-infusion rate and rate of responding on the reinforcement lever in the group treated with 5 micrograms naltrexone differed from placebo, whereas rate of responding on a dummy lever did not. These findings a) support the notion that opioid systems play a role in cocaine reinforcement, and b) suggest that naltrexone exerts its effect on cocaine reinforcement through action in the central nervous system.
Ramsey
N F
NF
Department of Pharmacology, Rudolf Magnus Institute, Medical Faculty, State University of Utrecht, The Netherlands.
van Ree
J M
JM
D000818:Animals; D001921:Brain / Q000187:drug effects; D003042:Cocaine / Q000008:administration & dosage*; D004347:Drug Interactions; D007262:Infusions, Intravenous; D007276:Injections, Intraventricular; D008297:Male; D009271:Naltrexone / Q000008:administration & dosage*; D051381:Rats; D011919:Rats, Inbred Strains; D012054:Reinforcement, Psychology; D012646:Self Administration
D009271:Naltrexone; D003042:Cocaine