Effect of pinealectomy on photoperiodic gonadal response of Indian palm squirrel, Funambulus pennanti

The role of the pineal gland in mediating the effects of photoperiod on the reproductive axis is not well established in tropical mammals. Indian palm squirrels (Funambulus pennanti) were exposed to experimental long (16L:8D) and short (6L:18D) photoperiods. It was observed that the testes regressed in response to short photoperiod, while during the long photoperiod the gonads were active. When squirrels were maintained for a long experimental period (130 days) under the short photoperiodic schedule (6L:18D), gonadal regrowth eventually occurred even though the photoperiod was the same one that initially induced testicular regression. Pinealectomized animals maintained the gonadal activity even in short photoperiod, suggesting that the effect of photoperiod is mediated through the pineal gland.