Blockade of adrenal compensatory hypertrophy by unilateral hypothalamic lesions

To determine if unilateral hypothalamic lesions block adrenal compensatory hypertrophy (ACH), such lesions were produced unilaterally under stereotaxic guidance using direct cathodal current in rats just after the left adrenal gland was removed. The animals were sacrificed one week later and the degree of the ACH of the remaining adrenal gland was determined. Animals without lesions uniformly showed ACH in terms of an absolute increase in adrenal weight of the remaining gland as compared to the one excised or if calculated as mg adrenal weight/100 g body weight. On the other hand, lesions in the region lateral to the paraventricular nucleus, lateral to the median eminence or in the region between these two loci prevented ACH in roughly 50% of the animals whether the lesion was placed on the same or opposite side of the hypothalamus. Some lesions in the mid-line in the vicinity of the paraventricular nucleus also resulted in blockade of ACH. We speculate that the blockade is due to a partial elimination of CRF and/or vasopressin/oxytocinergic pathways which are activated by the fall in plasma corticosterone after removal of an adrenal gland.