title: Chronic pretreatment with naltrexone facilitates acquisition of intravenous cocaine self-administration in rats.
abstract: Opioid systems may be involved in the reinforcing effects of drugs of abuse. It has been shown that the opioid antagonist naltrexone attenuates acquisition of intravenous cocaine self-administration behaviour in rats. Using a similar experimental set-up the effect of chronic blockade of opioid systems prior to cocaine exposure was examined. Rats were tested for acquisition of self-administration of one of 3 graded unit doses of cocaine (0.08, 0.16 and 0.32 mg.kg-1 per infusion) or saline. Chronic pretreatment with naltrexone (10 mg.kg-1 per day for 12 days) enhanced acquisition of intravenous cocaine self-administration but only in rats tested with the medium cocaine unit dose. It is concluded that chronic blockade of opioid systems facilitates acquisition of cocaine self-administration, probably by enhancing the reinforcing effect of cocaine.
authors: Department of Pharmacology, Rudolf Magnus Institute, Faculty of Medicine, University of Utrecht, The Netherlands.
authors: N F
authors: NF
authors: Ramsey
authors: J M
authors: JM
authors: van Ree
mesh_terms: D000818:Animals; D003042:Cocaine / Q000494:pharmacology*; D003216:Conditioning, Operant / Q000187:drug effects*; D007275:Injections, Intravenous; D008297:Male; D009271:Naltrexone / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012646:Self Administration
chemical_list: D009271:Naltrexone; D003042:Cocaine