Pineal-induced alteration of estrous cycles in blinded hamsters

Estrous cycles, as evaluated by vaginal smears of adult hamsters, were examined under a variety of experimental conditions. Normal females cycled regularly with oval and elongate nucleated epithelial cells usually observed one of every four days. Cycles of blinded hamsters did not vary from those of normal or blinded-pinealectomized hamsters until approximately 7 weeks after eye removal. Thereafter, blinded hamsters became acyclic, exhibiting a vaginal smear which contained cornified cells predominantly and varying numbers of leukocytes. An absence of follicles and corpora lutea also was observed in the ovaries of blinded hamsters. In addition, blinded hamsters possessed smaller than normal uteri. Cycles of blinded-pinealectomized hamsters never varied from those of normal hamsters; in each of these groups approximately 25% of the smears were routinely of the estrous type. Bilateral ovariectomy in animals blinded for 7 weeks had no effect on pattern of vaginal smears. Ovariectomy in normal and blinded-pinealectomized hamsters induced a cessation of cyclic epithelial changes and thereafter the smears appeared similar to those obtained from blinded or blinded-ovariectomized hamsters.