Research Abstract |
The aim of the present study is to examine by immunohistochemistry whether dopamine produced from L-dopa plus a peripheral decarboxylase inhibitor, carbidopa, a cluster of dopamine-immunoreactive neurons was found in the dorsal raphe nucleus (DR). In L-dopa/carbidopa-injected rats that were pretreated with an intraperitoneal injection of a MAO inhibitor, pargyline, whem compared with the L-dopa/carbidopa-injected rats without the pargyline pretreatment, neurons of the cluster of the DR became much darker in dopamine staining. The distribution of dopamine-stained neurons in the DR of these rats corresponded very closely to the previously reported distribution of serotonin-immmunoreactive neurons of normal rats. In normal or only pargyline-injected rats, dopamine-stained neurons were scarcely observed in the DR.We previously showed that serotonin neurons of the rat DR were induced to contain dopamine by the injection of L-dopa plus carbidopa. These findings suggest that the newly produced dopamine from L-dopa in serotonin neurons of the rat DR is degraded by endogenous MAO.
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