Photoperiodic responses are modulated by voluntary exercise in Djungarian hamsters (Phodopus sungorus)

Introduction: In response to short day (SD) lengths, Phodopus sungorus reduces body mass, size and activity of the gonads and changes into a whitish winter pelage. In previous studies we reported a reversal of the seasonal reduction in body mass and an impairment of seasonal gonadal regression in Phodopus with access to a running wheel (RW) in SDs. However, the seasonal change to a whitish winter fur was not affected by RW activity, suggesting that the SD signal can be read, but is overridden by a physiological response to RW activity. To understand how RW activity influences the occurrence of SD physiology, we…