Tanycyte morphology and cell adhesion molecule expression are regulated by photoperiod

Introduction: Seasonal breeders use the photoperiod to synchronize their reproductive physiology through the nightly secretion of the pineal hormone melatonin. However, the exact site of action of melatonin for the control of reproduction is still unclear. The Djungarian hamster (Phodopus sungorus) displays photoperiodic variations in body weight, fur color and gonadal size. In short photoperiod (winter) the gonads regress in size as the reproductive function is down regulated. This results in a regression of circulating sex steroids and their feedback on the brain. Thus, the brain is subject to seasonal variati…