Regulation of vasoactive intestinal polypeptide release in the suprachiasmatic nucleus circadian clock.

Timing of the mammalian circadian clock of the suprachiasmatic nucleus (SCN) is regulated by photic input from the retina. Retinorecipient units entrain rhythmicity of SCN pacemaker cells in part through their release of vasoactive intestinal polypeptide (VIP). The underlying nature of this process is conjectural, however, as in-vivo SCN VIP release has never been measured.

Environmental modulation of alcohol intake in hamsters: effects of wheel running and constant light exposure.

Background: Alcohol abuse leads to marked disruptions of circadian rhythms, and these disturbances in themselves can increase the drive to drink. Circadian clock timing is regulated by light, as well as by nonphotic influences such as food, social interactions, and wheel running. We previously reported that alcohol markedly disrupts photic and nonphotic modes of circadian rhythm regulation in Syrian hamsters.