Circadian rhythms of vasopressin release from individual rat suprachiasmatic explants in vitro.

A culture system was developed to study intrinsic oscillations within rat suprachiasmatic nuclei for long periods of time. After isolation in static organ cultures, individual rat suprachiasmatic explants released vasopressin in a circadian fashion for at least 4 cycles. This finding suggests that the suprachiasmatic nucleus contains one or more self-sustained circadian oscillators, and that this method of measuring circadian rhythms from individual suprachiasmatic organ cultures may prove to be a valuable model for elucidating the physiology and biochemistry of mammalian circadian pacemakers.