Intracellular analysis and structural correlates of the organization of inputs to ganglion cells in the retina of the turtle.

Intracellular recording from the ganglion cells of the retina of the turtle Pseudemys scripta elegans shows that the photoresponses are characterized by either of two reversal potentials. These have been related to the bipolar and amacrine cell inputs to ganglion cells. Of the recorded ganglion cells, 33% (type A) are driven predominantly by one type of input, attributed to bipolar cells. Other ganglion cells (66%, type B) receive a mixed input from bipolar and amacrine cells. Type A ganglion cells show a higher conduction velocity (up to 3 m/s) and a higher firing frequency (up to 160 spikes per second) than type B cells. By injecting Procion yellow into bipolar, amacrine and ganglion cells it may be observed that type A ganglion cells ramify only in those regions of the inner plexiform layer that contain cell processes originating exclusively from the bipolar cell type predicted from the recordings. Type B ganglion cells ramify throughout the inner plexiform layer in either a multi-stratified or a diffuse fashion.