Variations of neuronal nitric oxide synthase after hypophysectomy suggest a neuroprotective effect of nitric oxide in response to damage of the neurons of the hypothalamic supraoptic nucleus in the rat

Abstract

[EN]The hypothalamic-neurohypophyseal system offers an ideal model to study the processes of nerve degeneration/regeneration after lesions caused by cutting the hypophyseal stalk, or hypophysectomy. Additionally, the magnocellular neurons comprising it contain nitric oxide, and its enzyme, neural nitric oxide synthase, shows important variations in functional alterations of the hypothalamic-neurohypophyseal system. Currently, there is still some controversy as regards whether nitric oxide exerts neurodegenerative or neuroprotective effects in the nervous system. Here we performed a quantitative and qualitative study of the variations in the neuronal activity of nitric oxide synthase, using immunohistochemistry, and of its mRNA, by in situ hybridization, in the magnocellular neurons of the supraoptic nucleus of the hypothalamus of hypophysectomised rats with survival periods of 10-30 days. Our morphological and morphometric results and those pertaining to neuronal quantification and optical density point to a neuroprotective effect of nitric oxide on magnocellular neurons during the regenerative process of the supraoptic nucleus that occurs after hypophysectomy