Studies on the hormonal control of circadian outer segment disc shedding in the rat retina.

Previous work suggested that the circadian burst of outer segment disc shedding that occurs soon after the onset of light in the morning might be mediated by the pineal gland. In the present study the pineal glands of albino rats were either surgically removed or deafferented by bilateral superior cervical ganglionectomy. Neither surgical procedures affected the burst of disc shedding at 2, 3, or 11 weeks postoperatively. In addition, neither hypophysectomy nor parathyroidectomy and thyroidectomy perturbed the burst of disc shedding. Therefore the burst of disc shedding appears to occur independent of pineal, pituitary, and parathyroid-thyroid gland control.