MDL 72222, ketanserin, and methysergide pretreatments fail to alter breaking points on a progressive ratio schedule reinforced by intravenous cocaine.
The effects of three serotonin [5-hydroxytryptamine (5-HT)] receptor antagonists on cocaine self-administration behavior were investigated. Specifically, the effects of MDL 72222 (a specific 5-HT3 receptor antagonist), ketanserin (a specific 5HT2 receptor antagonist), and methysergide (an aselective 5-HT1/5-HT2 receptor antagonist) on the breaking points reached by rats on a progressive ratio schedule for cocaine reinforcement were examined. Pretreatments with MDL 72222 (7.5-1,920 micrograms/kg, SC), ketanserin (0.4-6.4 mg/kg, IP), and methysergide (2.5-20 mg/kg, IP) failed to alter breaking points from baseline values. Although tested at twice the highest doses previously reported to have significant behavioral effects, the three 5-HT receptor antagonists were without effect. These data suggest that relatively specific blockade of 5-HT receptor subtypes does not influence the reinforcing effects of cocaine.
Lacosta
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Department of Psychology, Carleton University, Ottawa, Canada.
Roberts
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DC
D000818:Animals; D003042:Cocaine / Q000008:administration & dosage / Q000494:pharmacology*; D003216:Conditioning, Operant / Q000187:drug effects*; D007275:Injections, Intravenous; D007650:Ketanserin / Q000494:pharmacology*; D008297:Male; D008784:Methysergide / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D012055:Reinforcement Schedule; D012646:Self Administration; D012702:Serotonin Antagonists / Q000494:pharmacology*; D014326:Tropanes / Q000494:pharmacology*
D012702:Serotonin Antagonists; D014326:Tropanes; D007650:Ketanserin; D003042:Cocaine; C042253:bemesetron; D008784:Methysergide