Vol. 31 (6) 2010 Neuro endocrinology letters

Phase shift of the circannual reproductive rhythm in European hamsters by 2 days of long photoperiod.

OBJECTIVES AND DESIGN: In European hamsters a circannual clock drives the seasonal changes in the reproductive state. Its resetting by photoperiod is clearly phase dependent. In mid subjective winter a 1-month pulse of long photoperiod (LP) advances the onset of the reproductive phase of animals maintained in constant short photoperiod .....