Effects of adrenal demedullation and peripheral noradrenaline-depleting agents on adrenocortical function and spleen in rats.

Adrenocortical functions of adrenal-demedullated rats (ADMx rats) and peripherally chemical-sympathectomized ADMx rats were studied by examining changes in the levels of serum and adrenal corticosteroids (CS). Resting levels of serum and adrenal CS were not influenced by adrenal-demedullation and peripheral chemical-sympathectomy with 6-hydroxydopamine. Diurnal variation in serum CS concentration was also unchanged, suggesting that peripheral adrenergic systems do not influence the basal function of hypothalamo-pituitary-adrenocortical axis. Exposure of ADMx rats to the stressful stimuli, however, resulted in lowered adrenocortical response with a lesser increase in serum CS concentration, while peripheral chemical-sympathectomy of ADMx rats with 6-hydroxydopamine or guanethidine caused a significant enhancement of adrenocortical response to the stress with elevation of the serum CS concentrations. These findings suggest that increased peripheral adrenergic activity may suppress the activation of the hypothalamo-pituitary-adrenocortical system as the animals were exposed to the stressful stimuli. Adrenal-demedullation produced no increase in spleen weight while chemical-sympathectomy by peripheral administration of 6-hydroxydopamine did produce a significant increase in the weight of this organ. Histological features following chemical-sympathectomy are described.