SEROTONIN SYNTHESIS INCREASED IN TERMINALS 4 DAYS AFTER RESERPINE TREATMENT - AN AUTORADIOGRAPHIC STUDY IN RAT-BRAIN

The rate of 5-HT synthesis was determined in discrete rat brain region s 4 days after a single dose of reserpine (10 mg/kg) or reserpine carr ier (controls), using an autoradiographic method with labelled alpha-m ethyl-L-tryptophan as a tracer. The results show that the rate of 5-HT synthesis was unchanged in the dorsal and median raphe, significantly decreased in the raphe magnus, and significantly increased in areas r ich in serotonergic nerve terminals (i.e., hypothalamus, hippocampus, median geniculate body, parietal and visual cortices). An increase in tryptophan hydroxylase activity could account for the increase in the rate of serotonin synthesis seen in some regions. Since the 5-HT synth esis rate showed regional variability there seems to be a need for reg ional studies of the effect of drugs on the 5-HT synthesis. In additio n, the 5-HT synthesis rate was not significantly different from that i n controls in many of the brain regions.