The inhibition of retinal ganglion cells by catecholeamines and γ-aminobutyric acid

1. l-Dopa, the metabolic precursor of Dopamine, was found to depress the amplitude of the evoked potential in the optic tract, when applied intravenously. 2. Electrophoretic application of Dopamine on retinal ganglion cells produced inhibition of spontaneous and light driven activity, increase of latency of light evoked excitation and occasional suppression of the antidromic invasion. Dopamine and Glutamate interacted in an antagonistic manner. 3. Noradrenaline andd-Amphetamine were likewise effective in depressing spontaneous and induced activity of ganglion cells. Serotonine was ineffective or weakly depressant. 4. The effect of electrophoretically applied GABA was similar to that of Dopamine. It differed by a faster onset, quicker reversibility and slight diminuition with time. 5. Substances suspected to be transmitters by virtue of their presence in the retina are thus shown to produce the expected pharmacological effects.