EFFECT OF RESERPINE ON 5-HYDROXYTRYPTOPHAN (5HTP)-IMMUNOREACTIVE NEURONS IN THE RAT-BRAIN

By immunohistochemistry of rat brain in conjunction with a specific an tibody against 5-hydroxytryptophan (5HTP), we examined immunoreactivit y to 5HTP in neurons, from which 5-hydroxytryptamine (5HT; serotonin) was depleted by reserpine treatment. The distribution patterns of 5HTP -positive neurons overlapped with those of 5HT neurons. Treatment with reserpine (5 mg/kg, 90 min before death) caused a complete suppressio n of 5HT-positive staining, but 5HTP-immunostaining remained in perika rya of the nuclei raphe dorsalis, centralis superior and obscurus. Tre atment with reserpine (25 mg/kg, 90 min before death) suppressed the 5 HTP-immunoreaction in certain perikarya (e.g. of the nucleus raphe dor salis) and fibres; however, 5HTP-immunostaining remained in perikarya of the nuclei centralis superior and raphe obscurus. This suggests tha t these neurons synthesize more 5HTP by a process which appears to be stimulated by reserpine.