Head-twitch response induced by ergometrine in mice: behavioural evidence for direct stimulation of central 5-hydroxytryptamine receptors by ergometrine.

Ergometrine (2.5-80 mg/kg IP) induced head twitches in mice. Pretreatment with cyproheptadine (1.5 and 3 mg/kg), methysergide (5 and 10 mg/kg) and (-)-propranolol (2.5 and 5 mg/kg) significantly decreased the number of head twitches induced by ergometrine. Pretreatment with p-chlorophenylalanine (100 mg/kg/day X 4 days) and clomipramine (5 and 10 mg/kg) significantly decreased the number of head twitches induced by fenfluramine (10 mg/kg) and p-chloramphetamine (5 mg/kg) but had no significant effect on the number of head twitches induced by ergometrine. The results indicate that ergometrine induces head twitches in mice by directly stimulating central 5-hydroxytryptamine receptors.