Vasopressin: its possible role in circadian time keeping.

In this review article an insight has been made into the strong possibility of the role of vasopressin (VP) in the control of circadian rhythms which has emerged from the results of the recent experiments in this field. A role for VP, which is identified in the suprachiasmatic nuclei (SCN) of mammals, as a neurotransmitter/neuromodulator in the central nervous system has been postulated for some time now. The presence of certain abnormalities in the circadian rhythms in VP deficient Brattleboro rats has suggested that this neuropeptide is a likely candidate in controlling circadian rhythms. The coexistence of VP and corticotropin releasing factor (CRF), their interrelation with reference to their role in the hypothalamus-pituitary-adrenocortical glucocorticoid axis not only in states of stress but also in day-to-day life has also been discussed. The possible role of dynorphin, which is co-synthesized with VP in the hypothalamic neurons, and other opioids in the control of circadian rhythms has been highlighted. The pineal, SCN relation in the process of development of circadian rhythms has also been reviewed briefly.