EXPERIMENTAL OBSERVATION OF RAT NEUROSECRETION UNDER DERANGED STEROID HORMONE MILIEU

The neurosecretory phenomenon of rat was studied morphologically under some experimental conditions of high and low steroid hormone milieu. 1. Estradiol, progesterone, testosterone and MAD exert direct excitatory action on neurosecretion without any mediation of hypophysis. These four hormones prevent the neurosecretory cell from retrograde degeneration following hypophysectomy. 2. Cortisone affects extensively thalamic and hypothalamic area while DOCA loads neurosecretion heavily until some of cell undergoes degeneration due to exhaustion. 3. Effect of ACTH and synahorin on neurosecretion can be interpreted as that of hormones of corresponding target organs. 4. Castration result in nuclear pyknosis of some supraoptic cells. Slight increase in Gomori substance and in nuclear size were present in most of neurosecretory cells while adrenalectomy results in unclear pyknosis of some supraoptic cells and in loss of neurosecretory material. 5. Nuclear pyknosis in some cells and disappearance of Gomori substance are induced by such stress as formalin and needle pricks on tail. These results obtained suggest that presumed neurohumoral mechanism through which hypothalamus exerts its control over hypophysis may be neurosecretion itself. The results of the experiments may offer morphological foundition in favor of accepted supposition that neurosecretion provokes the potuitary adrenocortcial response to stress.