Time dependence of the effect of ethanol on serotonin synthesis and tryptophan hydroxylase expression in the dorsal and median raphe of young rats

Serotonin (5-hydroxytryptamine, 5-HT) has been implicated in the pathophysiology of many neuropsychiatric disorders, and alcohol is reported to influence serotonergic neuronal activity in the dorsal raphe. In the present study, the effects of ethanol on the synthesis of 5-HT and the expression of tryptophan hydroxylase (TPH), the rate-limiting enzyme of 5-HT synthesis, in the dorsal and median raphe of rats were investigated, using immunohistochemial methods. Results showed that the density of 5-HT-positive and TPH-positive cells was reduced by ethanol treatment in a time-dependent manner. Based on these results, it is suggested that the pathogenesis of ethanol-induced neuropsychological disorders involves ethanol-induced suppression of 5-HT synthesis and TPH expression in the raphe region.