Pharmacological effects of oxaprotiline enantiomers on the central serotonin system

The study examined the effect of both oxaprotiline (OXA) enantiomers on the serotonin system in rats and mice. (+)-OXA and (-)-OXA partly inhibit the behavioral syndrome induced by 8-OH-DPAT and 5-methoxy-dimethyltryptamine (5-MeODMT) in normal and reserpinized rats. Imipramine and desipramine produced a similar but less potent effect. (+)-OXA and, to a lesser extent, (-)-OXA antagonized the m-chlorophenylpiperazine (m-CPP)-induced hypothermia in mice. Imipramine and desipramine produced no such effect. (+)-OXA attenuated the head-twitch response to L-5-HTP in mice, but (-)-OXA has no such action. Neither enantiomer inhibited the fenfluramine-induced hyperthermia in rats nor antagonized m-CPP-induced stimulation of hind limb flexor reflex of spinal rat. The obtained results indicate that both enantiomers may have a 5-HT1B-antagonistic action and a less potent 5-HT1A-antagonistic one; on the other hand, they shown no 5-HT2-antagonistic activity.