The behavioural effects of intravenously administered tryptamine in mice

The behavioural effects of intravenously administered tryptamine were examined in mice. Tryptamine in a dose greater than 15 mg/kg induced distinct head-weaving and hindlimb abduction. These behavioural syndromes appeared immediately after the injection and disappeared within 3 min. The changes in time course of the behaviour induced by tryptamine were consistent with those of the levels of tryptamine in the brain. Pretreatment with p-chlorophenylalanine, a depleter of 5-hydroxytryptamine (5-HT), failed to alter the effects of tryptamine on head-weaving or hindlimb abduction but did result in head-twitches which were never seen after tryptamine alone. Metergoline strongly antagonized the behavior induced by tryptamine. Pirenperone and haloperidol inhibited the behavioural syndrome, antagonizing the head-weaving in particular. alpha-Methyl-p-tyrosine, a depleter of dopamine, reduced the head-weaving without affecting the hindlimb abduction. These results indicate that the 5-HT syndrome induced by intravenous administration of tryptamine is due to the direct effect of tryptamine on the 5-HT receptor. Tryptamine-induced behaviour, especially head-weaving, seems to be linked with dopaminergic neurones.