SUPRACHIASMATIC CIRCADIAN PACEMAKER OF RAT SHOWS 2 WINDOWS OF SENSITIVITY TO NEUROPEPTIDE-Y IN-VITRO

The geniculohypothalamic tract carries visual information from the int ergeniculate leaflet to the suprachiasmatic circadian pacemaker. NPY, found in this projection, has been shown to affect the phase of behavi oral rhythms and influence photic entrainment. We now demonstrate that NPY, when briefly applied to the geniculate projection sites of rat S CN in vitro, induces permanent phase-shifts in the rhythm of neuronal electrical activity at two separate phases of the circadian cycle.