A: A 1 hr light pulse (closed circles) stimulates VIP release from the SCN vs. ACSF controls (open circles). B: A 1 hr reverse dialysis pulse of the glutamate receptor agonist, NMDA (closed circles), stimulates VIP release from the SCN vs. ACSF controls (open circles). C: A 1 hr reverse dialysis pulse of the 5-HT1A,7 agonist, 8-OH-DPAT (closed circles), suppresses VIP release from the SCN vs. ACSF controls (open circles). For each treatment, the sampling interval was 30 min and black bars represent the time of drug or light treatment. Values are the mean±S.E.M. * p<0.05 vs. baseline; a p<0.05 vs. control.