OVER the past few years, considerable evidence has accumulated to challenge the accepted view of the regulation of adrenocortical function. Conventionally, the cortex and medulla have been viewed as distinct functional units, with cortical function regulated primarily by the circulating hormones, ACTH and angiotensin II, acting mainly on the inner adrenocortical zones and the glomerulosa, respectively. However, it has become clear that certain aspects of adrenocortical function cannot be explained in this simplistic manner. Certainly there are discrepancies between the concentrations of these regulatory hormones and the secretion of the corticosteroids, suggesting that other factors may also be involved.

As a result of intensive study in recent years, we now know that the regulatory mechanisms that account for such discrepancies are mainly located within the adrenal itself, and that several different components of the gland contribute to these functions. The adrenal produces a wide variety of hormones, neuropeptides, neurotransmitters, and cytokines, and it is evident that the colocalization of these different systems has a profound functional significance. The cells