Darkness-elicited changes in rat reproduction not mediated by pineal gland

Serum and pituitary LH, prolactin and progesterone changes recorded in parturient rats exposed to continuous darkness throughout pregnancy were not prevented by early ablation of the pineal gland. Similarly, the shorter gestation period observed in rats kept in continuous darkness and the overwhelming tendency of rats in general to deliver during the light period (real or subjective), persisted in the pinealectomized animals. Darkness-induced endocrine changes in rat dams during the perinatal period appear not to be mediated by the pineal gland.