Evidence for a GABAergic inhibitory influence on serotonergic neurons originating from the dorsal raphe.

Systemic administration of progabide, dipropylacetamide and gamma-acetylenic-GABA diminished striatal 5-HTP accumulation; the effect of progabide was abolished after hemitransection. Intradorsal raphé (but not intrastriatal) infusion of GABA or GABA agonist agents reduced striatal 5-HTP accumulation. Infusion of picrotoxinin or bicuculline into the dorsal raphé was without effect. It is concluded that GABA exerts an inhibitory influence on striatal serotonergic transmission via stimulation of GABA receptors located in the dorsal raphé.