Regulation of the Adrenocortical Response to Insulin-Induced Hypoglycemia*

The effect of insulin-induced hypoglycemia on corticosterone secretion was studied in male rats to determine how the adrenocortical response to this stimulus is regulated. Insulin caused a dose-dependent increase in plasma corticosterone in both fed and fasted rats; however, the magnitude of the corticosterone response was related to the degree of hypoglycemia, not to the dose of insulin. Pretreatment of rats with pentobarbital did not affect the level of hypoglycemia caused by insulin but did alter the corticosteroid response, suggesting that afferent inputs to corticotropin-releasing factor neurons stimulated by hypoglycemia are barbiturate sensitive. Although the direct response to hypoglycemia was abolished by pentobarbital, the magnitude of the corticosteroid response to a surgical stimulus was increased in markedly hypoglycemic rats compared to that in euglycemic controls, suggesting that low glucose levels may act at some point in the final common pathway to augment hormonal responses to other stim...