Reaction of Rat Hypothalamic, Supraoptic, and Arcuate Nuclei Neurons in Experiment
Studies on 65 male rats were made by comparing the activity of supraoptic- (SON) and arcuate (AN)-nuclei neurons after dehydration, unilateral adrenalectomy, and nonspecific-factor effect, i.e., growth of Jensen’s-sarcoma conditions. The neuronal activity was assessed by the neuronal-nucleolar optical density (OD) after staining with gallocyanin chromalum (EINARSON, 1951). After 2 days of dry feeding, considerable activation of SON neurons was observed (with OD increasing to 112%, P < 0.01). This activation remained until the 5th day, when the level fell. After unilateral adrenalectomy, neuronal activity increased by 109% compared with that of sham-operated rats. In Jensen’s-sarcoma growth conditions, the SON neuronal activation was observed on the 21st day of the experiment, and was somewhat lower on the 35th day. AN neuronal activity after 2 days of dehydration was strikingly increased (118.5%, P < 0.001) with a negligible decrease on the 5th day. After unilateral adrenalectomy the activity was practically unchanged on the 5th day, but it decreased on the 15th day (94% of control, P < 0.05). The AN neurons’ response to Jensen’s-sarcoma growth was the same as that of the SON neurons, but it was less marked. The data enable us to conclude that the system of magno- and parvocellular hypothalamic nuclei is involved in stress-reaction formation and in aqueoussaline- equilibrium regulation. The increase of SON neuronal activity on the 15th day after adrenalectomy, when there is some decrease of AN neuronal activity, suggests that the SON has a predominant role in compensatory hypertrophy of the adrenal gland.