Influence of pinealectomy on the breeding capability of hamsters maintained under natural photoperiodic and temperature conditions

Pinealectomized and sham operated adult male and female hamsters were kept under natural photoperiodic and temperature conditions beginning Sept. 22, 1972. On Dec. 28, 1972, sham operated male and female hamsters had atrophic reproductive organs, whereas those of pinealectomized animals appeared to be reproductively competent. Pinealectomized females, which were caged with pinealectomized males, bore litters during the months of Jan. and Feb. Pinealectomized or sham operated females, caged with sham operated males, did not become pregnant until early March. The results show that pinealectomized hamsters remain reproductively competent during the winter months.