Quipazine reduces food intake in the rat by activation of 5-HT2-receptors

Abstract

1 To determine which subtype(s) of 5-hydroxytryptamine (5-HT) receptor are involved in the anorectic action of quipazine, the ability of selective antagonists at 5-HT₂- and 5-HT₃-receptors, and an antagonist at 5-HT₁-like receptors, to block this response were investigated in non-deprived rats, trained to eat a palatable diet. 2 Quipazine (0.5–8 mg kg⁻¹, i.p.) produced a dose-related reduction in the intake of palatable diet. 3 The anorectic effect of 4 mg kg⁻¹ quipazine was antagonized by the nonselective 5-HT-receptor antagonist methysergide (5 mg kg⁻¹, i.p.) and by the selective 5-HT₂-receptor antagonists ketanserin (1 mg kg⁻¹ and 2.5 mg kg⁻¹, i.p.) and ritanserin (0.5 mg kg⁻¹ and 1 mg kg⁻¹, i.p.). The selective 5-HT₃-receptor antagonist GR38032F (1 mg kg⁻¹, i.p.) and (−)-pindolol (4 mg kg⁻¹, i.p.), which blocks some of the effects mediated at 5-HT₁-like receptors, did not block the reduction in food intake produced by this dose of quipazine. 4 None of the 5-HT-receptor antagonists had any effect on food intake when they were administered alone, suggesting that endogenous 5-HT is not involved in the tonic control of food intake under the conditions of these experiments. 5 It is concluded that the anorectic action of quipazine is mediated, at least in part, by activation of 5-HT₂-receptors.