Phencyclidine-induced head-twitch responses as 5-HT₂ receptor-mediated behavior in rats

This study was designed to assess whether phencyclidine (PCP)-induced head-twitch was antagonized by ritanserin, a selective serotonin (5-HT₂) receptor antagonist, in mice and rats to confirm the involvement of 5-hydroxytryptamine (5-HT) neurons in PCP actions in comparison with 5-methoxy-N,N-dimethyltryptamine (5-MeODMT)-induced behavior. PCP (7.5, 10 and 12.5 mg/kg. i.p.)-induced head-twitch was completely antagonized by ritanserin (1 mg/kg, s.c.) in mice and rats, and 5-MeODMT (2 and 4 mg/kg, i.p.)-induced head-twitch was also completely antagonized by ritanserin in mice. PCP and 5-MeODMT induced head-weaving in mice after ritanserin treatment, but this did not occur in rats. In rats, 5-MeODMT failed to induce head-twitch. These results suggest that PCP-induced head-twitch response in rats is developed via 5-HT₂ receptors and it is a useful 5-HT₂ receptor model, while 5-MeODMT-induced head-weaving in rats is developed via 5-HT₁ receptors and is a useful 5-HT₁ receptor model.