Loss of eye movements abolishes light entrainment of circadian mesolimbic catecholamine excitability: a function for REM?

Light entrainment of the circadian rhythm of mesolimbic dopamine excitability, measured by the amphetamine-induced locomotor response, and the circadian feeding rhythm was abolished following section of the extraocular muscles of the rat. Endogenous (free-running) circadian rhythms were preserved. The results are consistent with electrophysiologic evidence that the rapid eye movements during paradoxical sleep transmit light-modulated electrical potentials to regions of the brain that influence circadian rhythms and dopamine release.