Effect of tryptamine on the behavior of mice.

The effects of tryptamine (TRM) on behavior were investigated in mice. TRM at a dose of 50 mg/kg i.p. induced an inhibition of locomotor activity and, at doses ranging from 150 to 300 mg/kg, induced peculiar behaviors such as head twitch, head weaving, forepaw treading, hindlimb abduction and Straub tail. These behavioral effects were continuous, although TRM rapidly disappeared from the brain. Methysergide, a 5-hydroxytryptamine (5-HT) receptor antagonist, completely abolished TRM-induced excitatory behaviors and p-chlorophenylalanine, a 5-HT depleter, significantly inhibited the behaviors. Our results show that TRM induced both the depression and excitation in the behavior of mice depending on the dosage and TRM-induced excitatory behaviors may be attributed to both its direct stimulation of 5-HT receptors and facilitation of 5-HT release.