Figure 3: Cholinergic signalling powerfully controls the light-evoked action potential output of ON-DSGCs.

(a) Physiological activation of the retinal microcircuit (summarized in the inset schematic) by light bars moved across the receptive field of an ON-DSGCs (inset morphological reconstruction) leads to the generation of powerful action potential (AP) firing when moved in a preferred direction, but sparse AP output when moved in a null direction (control, black traces, APs have been truncated for clarity). The antagonism of nAChRs leads to a reduction of preferred direction light-evoked AP firing and the generation of pure inhibitory responses when light stimuli are moved in the null direction (hexamethonium (Hex); red traces). (b) Peri-stimulus histogram of preferred and null direction light-evoked AP firing under the indicated conditions (bin size 20 μm). (c) Quantification of the reduction of preferred direction light-evoked AP firing by nAChR antagonists (mecamylamine (MMA); blue symbols). (d) Quantification of the voltage integral of median filtered (10 ms) preferred and null direction light responses under the indicated conditions (control versus Hex: preferred: P<0.0001, T=10.19; null: P<0.0001, T=11.47; control versus MMA: preferred: P<0.0001, T=15.86; null: P=0.0038, T=6.02). All light stimuli were applied under photopic conditions. Stimulus intensity was twice that of background illumination.