The influence of serotonergic agents on the body temperature.

The effects of serotonin precursors, tryptophan (TP) and L-5-hydroxytryptophan (5-HTP), administered together with peripheral decarboxylase inhibitor -- Ro 4-4602 on the rectal body temperature of rats was studied. TP caused a significant hypothermia which was prevented by pretreatment with p-chlorophenylalanine (PCPA), the serotonin synthesis inhibitor. 5-HTP did not influence the body temperature or slightly decreased it. However, the significant hypothermizing effect of 5-HTP was observed in rats pretreated with spiroperidol, haloperidol or phenoxybenzamine. Methysergide or cyproheptadine -- compounds regarded as potent serotonin receptor blockers -- did not prevent the TP-induced hypothermia. In methysergide pretreated rats 5-HTP produced a considerable hyperthermia. Cyproheptadine did not influence the effects of 5-HTP on the body temperature. The results obtained suggest that cyproheptadine and methysergide fail to block those central serotonin receptors which produce hypothermia after their stimulation.