SEROTONERGIC POTENTIATION OF PHOTIC PHASE-SHIFTS OF THE CIRCADIAN ACTIVITY RHYTHM

RECENT evidence suggests that serotonin may function to regulate the s ensitivity of the circadian clock to the resetting effect of environme ntal light. Here we report that systemic administration of NAN-190, a drug that acts at both postsynaptic and somatodendritic serotonin rece ptors, potentiates light-induced phase shifts by as much as 250%. The effects of the drug are dose-related and are significant at light inte nsities between 0.2 and 200 lux. It is proposed that drugs with pharma cological properties similar to NAN-190 may prove useful as chronobiol ogics to adjust the sensitivity of the circadian system to natural 'ze itgebers'.