Top panel: Dark-adapted ERGs in response to response saturating high-energy flashes (2–2.3 log sc td s) recorded in a single experimental session from a single anesthetized hRhoG/hRhoG mice after the following (temporal sequence from left to right): 30 min of instillation of topical atropine (A, grey trace), 1 hour of instillation of topical atropine + phenylephrine (A+P, black trace) and 1 hour of intravitreal injection of GABA in the A+P instilled eye (traced with black dots). Bottom panel: Averaged dark-adapted ERGs in response to high-energy flashes (2–2.3 log sc td s) recorded from single experimental sessions from anesthetized hRhoG/hRhoG mice (n=4) after the following (temporal sequence from left to right): instillation of topical atropine (A, grey trace), instillation of topical atropine + phenylephrine (A+P, black trace) and intravitreal injection of GABA (traced with black dots).