Figure 1. Acetylcholine‐generated light responses in a subpopulation of rat ganglion cells.

A, the light responses of two ON‐OFF and an ON sustained retinal ganglion cell under control conditions, then in the presence of 100 μM hexamethonium (HEX). The top ON‐OFF cell was designated HEX‐sensitive, as its spiking was blocked completely by HEX (see text for details). The spiking in the lower two cells was unaffected, and designated HEX‐insensitive. The 1s light stimulus, a 200 μm diameter green spot (2.4 × 10⁴ R^*/rod/s), is represented by the solid bar above each trace. B, summary of relative number of spikes in HEX‐sensitive and HEX‐insensitive neurons in control, then in the presence of HEX, after recovery, and in the presence of d‐tubocurarine (Tubo) (^* P < 0.005). HEX‐sensitive neurons were all ON‐OFF cells (n = 20), while HEX‐insensitive neurons were either ON‐OFF transient (n = 20), ON sustained (n = 9) or OFF sustained (n = 9). C, the L‐EPSP of a HEX‐sensitive neuron recorded in whole cell configuration in control and HEX. D, the average L‐EPSP (spikes not included) of HEX‐sensitive cells (n = 7) in control, HEX and wash (^* P < 0.005). E, the L‐EPSPs of a HEX‐insensitive neuron in control and HEX. F, the average L‐EPSP in HEX‐insensitive neurons in control, HEX and wash (n = 7).