Intraventricular carbachol mimics the phase-shifting effect of light on the circadian rhythm of wheel-running activity

Intraventricular injections of carbachol, a cholinergic agonist, into free-running mice can cause phase dependent phase shifts, in both directions, in the circadian rhythm of wheel-running activity. These effects mimic the action of light in entraining the circadian pacemaker, and suggest that acetylcholine may play a role in photoentrainment.