Bromocriptine self-administration and bromocriptine-reinstatement of cocaine-trained and heroin-trained lever pressing in rats.
Rats were trained to lever press for intravenous cocaine (1.0 mg/kg/injection) and then switched to bromocriptine (0.3, 1.0, or 3.0 mg/kg/injection) on a FR-1 reinforcement schedule. Bromocriptine sustained responding at all three doses; hourly drug intake increased linearly with log-dose. In a second experiment, animals were trained to respond for cocaine (1.0 mg/kg/injection) or heroin (0.1 mg/kg/injection) reinforcement; drug was available for the first 2 h of each daily session; saline was substituted for cocaine or heroin for 5 subsequent hours. One hour into each saline substitution session, an intravenous injection of saline or bromocriptine (0.0, 0.5, 1.0, or 2.0 mg/kg) was given. Bromocriptine reinstated both cocaine-trained and heroin-trained lever pressing; under these conditions, the drug was most effective in the heroin-trained animals. Reinforcing doses of clonidine (0.0625 and 0.125 mg/kg), methohexital, and nicotine (0.05 and 0.1 mg/kg), and a sub-intoxicating dose of ethanol (2 g/kg) failed to reinstate cocaine-trained responding. These data indicate that bromocriptine has cocaine-like and heroin-like stimulus and reinforcing effects.
Wise
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RA
Department of Psychology, Concordia University, Montreal, Canada.
Murray
A
A
Bozarth
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MA
D000818:Animals; D001971:Bromocriptine / Q000494:pharmacology*; D003000:Clonidine / Q000494:pharmacology; D003042:Cocaine / Q000494:pharmacology*; D003216:Conditioning, Operant / Q000187:drug effects*; D000431:Ethanol / Q000494:pharmacology; D003932:Heroin / Q000494:pharmacology*; D008297:Male; D009538:Nicotine / Q000494:pharmacology; D051381:Rats; D012055:Reinforcement Schedule; D012054:Reinforcement, Psychology; D012646:Self Administration
D001971:Bromocriptine; D000431:Ethanol; D009538:Nicotine; D003932:Heroin; D003042:Cocaine; D003000:Clonidine