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
