Vagal influence on the adrenocortical function of the rat.

The vagal influence on the fasciculata's function was studied in 23 Wistar male rats. The corticoadrenal function was evaluated by means of karyometric and histological studies. After vagotomy, the fasciculata of the left adrenal (operated side) showed a significant increase of the nuclear area in comparison with the right (control) side. This side difference was maintained in the stressed rats. In these animals the nuclear area did not increase significantly in either of the two adrenals. These results lead to the following conclusions: the vagus nerve, in normal conditions, has an inhibitory influence on the adrenal cortex; the vagal participation in the corticoadrenal response to a neurogenic stressor is meagre; the inhibitory vagal action on the fasciculata must be direct since the corticoadrenal modifications were unilateral, whereas, if the vagal influence were exerted through the hypophysis, the adrenal reaction should be bilateral; and, finally, the participation of the vagus nerve in the adrenal vascular disorders, which appeared in the stressed rats, seems to be insignificant since both glands, vagotomized and non vagotomized, showed a similar appearance.