Pineal Regulation of Immunoreactive Luteinizing Hormone and Prolactin in Light-Deprived Female Hamsters

Abstract

The influence of light deprivation pinealectomy and pineal denervation on pituitary and plasma levels of luteinizing hormone (LH) and prolactin in 62 adult female hamsters was studied. 46 of the hamsters were blinded by bilateral orbital enucleation. 10 of the blinded animals were pinealectomized and 11 were superior cervical ganglionectomized. After 8 weeks 12 blinded and 8 intact hamsters received 4-mcg LH-releasing hormone (RH)/day for 1 week after which all animals were necropsied. Immunoreactive LH and prolactin levels were determined by double antibody radioimmunoassays. The blinded hamsters had significantly higher levels of LH within the pituitary than the normal controls (p less than .001). Pituitary prolactin levels in the blinded were significantly decreased (p less than .001). LH-RH treatment did not markedly alter LH or prolactin levels in the pituitary. Plasma LH of the blinded hamsters was about twice as high as the controls. LH-RH did significantly raise plasma LH in the intact and blinded (p less than .01 and p less than .02 respectively). Blinded hamsters that were pinealectomized or ganglonectomized had LH and prolactin levels comparable to the controls. Plasma prolactin levels were only slightly altered among the 6 experimental groups.