HYPOTHALAMO-NEUROHYPOPHYSIAL NEUROSECRETION AFTER THE EXTIRPATION OF VARIOUS ENDOCRINE GLANDS

Abstract

The possible role of the hypothalamo-neurohypophysial system in regulating the release of the anterior pituitary hormones was studied in the rabbit and the rat. Thyroidectomy, gonadectomy and uni- and bilateral adrenalectomy were the experimental conditions used. The neurosecretory material (N. S. M.) was demonstrated by the aldehyde-fuchsin (AF) technique. Distinct differences were not seen in the different groups of rabbits on account of the great variation between individuals. In the rats, the thyroidectomy and gonadectomy groups often had slightly more N. S. M. in the median eminence around the portal vessels than the controls. Slight depletion of N. S. M. in the infundibular process was observed in unilaterally adrenalectomized rats. N. S. M. passing into the portal vascular system showed a tendency to increase. In the bilateral adrenalectomy group, N. S. M. was reduced in the supraoptic and paraventricular nuclei, in the hypothalamo-hypophysial tract and in the infundibular process. However, considerably more numerous neurosecretory nerve fibres passing towards the portal vessels than in the controls were found in the median eminence of this group. The conclusion drawn was that N. S. M. entering the hypophysial portal vessels in the median eminence may be of significance in the regulation of corticotrophin release.