Figure 1. Pharmacological isolation of mouse ipRGCs.

. Representative raw voltage traces from a wildtype mouse retina (C57Bl6) recorded simultaneously from 15 electrodes of a multielectrode array. Most electrodes recorded spikes originating from more than one cell. Timing of full-field light stimulus is indicated by the step above the traces and by the time scales below the traces. Left column: Spike responses recorded in control Ames' medium to a relatively dim scotopic flash (2.3 Rh^*/rod/s; 500 nm; 1 second) that should excite rods but not cones or melanopsin[59]. Multiunit light responses are detectable on every channel, and exhibit various forms (ON, OFF or ON-OFF; transient or sustained). Right column: Light-evoked spike activity recorded on the same electrode in the presence of drugs blocking rod and cone signaling to ganglion cells. To permit activation of melanopsin, the stimulus was longer and >10,000-fold brighter than that at left (∼2×10⁵ Rh^*/rod/s sampled at 500 nm; 10 sec). This evoked responses on a minority of channels (arrows) and these exhibited the long onset latency and persistent post-stimulus discharge typical of melanopsin-mediated intrinsic responses (note the slower time scale).