Single unit responses of substantia nigra and globus pallidus neurons to GABA agonist and antagonist drugs.

The studies reported here shed some new light upon the role of GABA within the basal ganglia. Although the proposed inhibitory interaction between the striatonigral GABA pathway and nigral dopamine neurons has, over the years, received the greatest attention, it now appears that this interaction may constitute only one part of a more extensive and perhaps more physiologically significant network of GABA-mediated effects upon populations of non-dopaminergic neurons. Specifically, evidence has been presented which indicates that the substantia nigra pars reticulata and the globus pallidus, two regions known to receive striatal GABAergic fibers, each contain groups of cells with a more marked ability to be affected by GABA and GABAmimetic drugs than the nigrostriatal dopamine neurons. Since reticulata and pallidal neurons seem at least as likely as dopamine neurons to be targets of this striatal GABAergic pathway, a much more expanded role for GABA within the basal ganglia might now be explored. Given their marked sensitivities to GABA, if reticulata and pallidal cells do lie postsynaptic to GABA terminals then function in several motor-related areas to which these cells project might be greatly affected by striatal and pallidal GABAergic efferents. Future studies aimed at elucidating the nature and importance of these GABA-mediated interactions may ultimately provide new clues about how the basal ganglia influence motor function.