Suprachiasmatic injection of a vasopressin antagonist modifies the circadian rhythm of food intake

To study the effect on the circadian feeding rhythm, injections of AVP and its antagonist were made into the suprachiasmatic nuclei (SCN) of rats after implanting cannulae into the bilateral SCN. Injections of arginine vasopressin (AVP) antagonist at the beginning of the light and dark phases disrupted the circadian rhythm of food intake while injections of AVP during the beginning of the light or dark phase did not disrupt the circadian rhythm. It may be concluded that endogenous vasopressin has a modulatory role in the mediation of the circadian feeding rhythm at SCN.