Effect of acute fluoxetine treatment on the brain serotonin synthesis as measured by the alpha-methyl-L-tryptophan autoradiographic method.

The effect of treatment with acute fluoxetine, a serotonin reuptake inhibitor, on the rate of serotonin synthesis in the rat brain was studied through autoradiography following intravenous administration of alpha-methyl-L-[3H]tryptophan. The rate of serotonin synthesis in fluoxetine-treated rats was compared with the rate measured in sham-treated rats (saline injection). Results showed a significant increase in the rate of synthesis in the majority of cerebral structures examined. The greatest increase (given as a percentage of rates in control animals) in the rate of serotonin synthesis was observed in the substantia nigra compacta (344%), hippocampus-CA3 (337%), dorsal hippocampus (283%), and caudate-putamen (232%). Fluoxetine had a less significant effect on the rate of synthesis in the pineal body (44%). Data suggest that acute fluoxetine treatment (30 mg/kg, i.p.) enhances the rate of serotonin synthesis in all the structures of rat brain examined in this work.