EFFECTS OF ETHER ANAESTHESIA AND HAEMORRHAGE ON HORMONE STORAGE AND ULTRASTRUCTURE OF THE RAT NEUROHYPOPHYSIS

Abstract

SUMMARY Effects of ether anaesthesia with or without haemorrhage were investigated in the rat neurohypophysis in vivo and in vitro. Simultaneous observations were made on hormone release from, and the ultrastructure of, the same neural lobes. Variable decreases in hormone content were found in the neural lobes of both anaesthetized, and anaesthetized and bled animals. A significant depletion of vasopressin (P < 0·01) occurred in the latter group when related to pressor activity/mg. wet neurohypophysial tissue. Incubation of neural lobes removed after stimulation showed that the proportions of diffusible (free) vasopressin and oxytocin had increased. Haemorrhage under ether anaesthesia caused a significant increase in the amount of free vasopressin (P < 0·01), but not of oxytocin (P > 0·05). Examination of control and stimulated rat posterior pituitaries with the electron microscope showed a loss of the electron-dense material from the elementary granules of the neurohypophysial nerve fibres, their swellings and their terminals after the neurones had been subjected to hormone releasing stimuli. It is suggested that disappearance of the electron-dense content of the hormone-carrying granules is not related to hormone content in the gland. An increased number of small vesicles (250–600 Å) was observed in the nerve fibre swellings of the stimulated posterior pituitary. The distribution, origin and function of these small vesicles is discussed.