Effects of hypothalamic deafferentation on light-stimulated ovarian function in turkeys

Previous studies in the turkey have shown that lesions placed in the preoptic brain (POR) block ovulation, while lesions placed in the tuberal hypothalamus (TH) induce regression of rapidly growing ovarian follicles. In the present experiments, the nature of the neural pathways to and between these regions is explored by the method of neural transection performed with a small, stereotaxically positioned knife. Superior deafferentation of the POR allowed light-stimulated rapid growth of ovarian follicles but appeared to block or suppress ovulation. Complete deafferentation of the TH prevented development of the ovary as indicated by the failure of ovarian follicles to enter the phase of rapid growth. Partial cuts that severed anterior inputs to the TH blocked follicular growth, whereas cuts that severed lateral and posterodorsal connections or posterior connections to this region had no effect on development of a functional ovary. Deafferentation of the posterior two-thirds of the TH, which created an island including the posterodorsal region of the infundibular nuclear complex, did not block ovulation.