Effect of photoperiod on testicular functions in male Sprague-Dawley rats.

Variation in reproductive status in response to photoperiods has been observed in laboratory rats. We investigated the effects of photoperiod on testicular activity in Sprague-Dawley rats (Rattus norvigicus) maintained in experimental photoperiodic condition. Twenty-four adult male rats weighing 170+/-10g were conditioned to different lighting conditions of Light/Dark (LD) Cycle for 6 weeks. Group 1, Control group (LD12:12, light on from 07:00hr to 19:00hr). Group 2, Short Photoperiod group (LD 8:16hr, light on from 09:00hr to 17:00hr). Group 3, Long Photoperiod group (LD 16:8hr, light on from 05:00hr to 21:00hr). A significant influence of different lighting conditions on the testicular parameters was observed. Short photoperiod showed a suppressing effect (P < 0.001) on testicular weight, sperm motility sperm viability and sperm counts, while long photoperiod had an inducing, though insignificant, effect on the measured parameters. The results confirmed that Sprague-Dawley rats are photoresponsive and changes in the photoperiod could influence their reproductive functions.