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MDL 72222, ketanserin, and methysergide pretreatments fail to alter breaking points on a progressive ratio schedule reinforced by intravenous cocaine

1993; Elsevier BV; Volume: 44; Issue: 1 Linguagem: Inglês

10.1016/0091-3057(93)90295-5

1873-5177

Susan Lacosta, David C. S. Roberts,

Neuroendocrine regulation and behavior

The effects of three serotonin [5-hydroxytryptamine (5-HT)] receptor antagonist 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 μg/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.