Inhibition of dopamine release in the cat caudate nucleus by nigral application of glycine.

"Encéphale isolé" cats were implanted with two push-pull cannulae, one in the left caudate nucleus and the other in the ipsilateral substantia nigra. L-3,5(-3)H-Tyrosine was introduced continuously into the caudate nucleus to study the release of 3H-DA. Glycine (10(-5)M) added to the superfusing medium of the push-pull cannula inserted into the substantia nigra reduced (25%) the spontaneous release of 3H-DA. Conversely, strychnine (10(-5)M) slightly stimulated the 3H-transmitter release. The inhibiting effect of glycine (10(-5)M) on 3H-DA release was no longer seen in the presence of strychnine (10(-5) M). The results support the hypothesis of a tonic glycinergic inhibitory control of the activity of the nigrostriatal dopaminergic neurons.