Transmitters for the afferent and efferent systems of the neostriatum and their possible interactions.

The surgical denervation techniques have been widely employed as a tool to identify the neuronal origin of various neurotransmitters in the basal ganglia. Besides the well known nigrostriatal dopaminergic pathway, there is a high glutamic acid-containing corticostriatal connection and the cholinergic thalamostriatal projection. On the other hand, it is strongly suggested that GABA is the transmitter for the strionigral and striopallidal efferent systems. Furthermore, no evidence was found to support strionigral or striopallidal cholinergic pathways. From the 6-OHDA experiments, it is proposed that the 6-OHDA not only has a selective toxic effect on dopaminergic neurons, but also affects the cholinergic neurons in the striatum, and may provide further evidence for dopaminergic-cholinergic interaction in the striatum. Finally, GABA may modulate dopamine metabolism in the striatum.