Strychnine-sensitive and -insensitive inhibitions in the cat's retina.

Effects of strychnine on intraretinal inhibition were investigated by recording unitary discharges from the optic tract fibers. Units were classed as on, off and on off according to their discharge patterns in response to diffuse illumination of the retina. Strychnine enhanced the firing rate of spontaneous discharge in the dark. ' On' inhibition of an off unit was greatly suppressed by strychnine, whereas 'off' inhibition of an on unit was not affected to an appreciable extent. The latter, however, was suppressed by picrotoxin. This difference was discussed in the light of the recent concept of inhibitory mechanisms and also of morphological find ings on synapses in the inner plexiform layer.