Reproductive Effects of the Mammalian Pineal

The reproductive systems of mammals are anatomically and physiologicallyaltered by the pineal gland. Characteristically, pineal removalaccelerates gonadal growth in immature animals and causes atransient modest enlargement of the reproductive organs if theoperations are done after adulthood is attained. Light deprivationrenders the pineal strongly antigonadotropic. In addition, thereare several conditions, e.g., androgen-sterilization and anosmia,which potentiate, probably indirectly, the gonad-inhibitingcapability of the rat's pineal. The chronic administration ofpineal extracts or pineal substances has effects opposite topinealectomy, i.e., they restrict gonadal development or growth.The pineal is possibly important in adjusting the level of reproductiveactivity to seasonal changes in environmental conditions.