Effects of Brain Stem Lesions on Aldosterone and Cortisol Secretion

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Abstract
Brain stem lesions were made by high frequency coagulation in cats that had been maintained on regular or low sodium diets. Four hours after placing the lesion, adrenal venous blood was collected for determination of the secretion rates of aldosterone and cortisol. Discrete lesions placed in the dorsal central region of the rostral midbrain, involving primarily the posterior commissure, the periaqueductal gray substance and structures immediately adjacent to it, resulted in significant reductions in aldosterone output both types of animals. Cortisol output was somewhat depressed in cats on the regular diet following discrete lesions of the rostral midbrain, while in the low sodium group the output of this steroid was unaffected. Larger lesions which involved the habenulae, the stria medullaris and/or the pineal gland, in addition to the central rostral midbrain, modified or obscured the effects of the discrete rostral midbrain lesions on steroid secretion. In animals on either diet these larger lesions resulted in aldosterone levels significantly higher than those occurring following discrete lesions of the rostral midbrain. While aldosterone output in the sodium-deprived group following the larger lesions was lower than control rates, in the group on the regular diet the output of this steroid was not different from control levels. The larger lesions also resulted in cortisol output elevated above control levels. The implications of these findings are discussed in terms of central nervous system stimulatory and inhibitory components regulating aldosterone and cortisol secretion.