GLYCINE STIMULATES STRIATAL DOPAMINE RELEASE IN CONSCIOUS RATS

1 Glycine is an inhibitory neurotransmitter in the spinal cord and bra instem. The mechanism of this inhibition is via binding of glycine to specific receptors, increasing transmembrane Cl- conductance and hyper polarizing neurones. Strychnine selectively antagonizes these effects. The role of glycinergic neurones in supraspinal regions is poorly und erstood. 2 Effects of glycine on release of catecholamines in the stri atum were examined by microdialysis in freely-moving rats. Transcripti on of the genes encoding strychnine-sensitive glycine receptors was as sessed in the striatum and substantia nigra, by use of reverse transcr iption followed by the polymerase chain reaction. 3 Glycine administer ed via the microdialysis probe dose-dependently increased concentratio ns of dopamine and its metabolites, dihydroxyphenylacetic acid and hom ovanillic acid, in the perfusate, indicating increased local release a nd metabolism of dopamine. Strychnine markedly attenuated these respon ses. Whereas striatal tissue did not contain mRNA for either the adult or neonatal form of strychnine-sensitive glycine receptor, nigral tis sue contained a message for the adult form. 4 The results suggest that dopaminergic cells in the substantia nigra synthesize strychnine-sens itive glycine receptors and transport the receptors to terminals in th e striatum. Occupation of the glycine receptors then exerts a net stim ulatory effect on striatal dopamine release in vivo.