ENHANCED PHOTIC PHASE-SHIFTING AFTER TREATMENT WITH ANTISERUM TO NEUROPEPTIDE-Y

Previous work has shown that antiserum to neuropeptide Y blocks phase shifts to certain non-photic stimuli at circadian time 4. To examine t he role of NPY in photic phase shifts, antiserum to neuropeptide Y was administered just prior to a light pulse at circadian time 18. Hamste rs were implanted with guide cannulae aimed at the suprachiasmatic nuc leus, and housed in constant darkness. Animals were injected at circad ian time 18 under a dim red safe light with 200 nl of either antiserum to neuropeptide Y or normal serum. They were then either exposed to l ight (approximately 100 lux) for 15 min or returned to constant darkne ss. Hamsters shifted more to the light pulse when pretreated with anti serum to neuropeptide Y (mean normal serum + light = 1.18 h; mean anti serum to neuropeptide Y + light = 1.92 h; P < 0.01 on a two-tailed pai red t-test). Therefore, antiserum to neuropeptide Y enhanced photic ad vances at circadian time 18.