Regulation of alpha and beta components of noradrenergic cyclic AMP response in cortical slices

The cyclic AMP response to catecholamines in the rat cerebral cortex is mediated by both beta- and alpha-adrenoceptors. The beta-receptors cause a direct activation of adenylate cyclase whereas the alpha alpha-receptors play a modulatory role and act by potentiating the response to beta stimulation. The present study investigated whether the functions of these two types of cyclic AMP-linked receptors are regulated differently by various physiological factors known to affect adrenoceptor function. It was found that treatments that affect central noradrenergic neuronal function including repeated administration of desmethylimipramine or lesion of central noradrenergic pathways produced selective changes in the cAMP response to beta-receptor stimulation whereas treatments that affect adrenocortical function including ACTH of corticosterone administration and hypophysectomy or adrenalectomy produced selective changes in the potentiation response to alpha-receptor stimulation. The change in the alpha potentiation effect caused by corticosterone was found to be abolished in the presence of prazosin indicating that the hormone affects alpha 1-adrenoceptor function. The results support the hypothesis that the beta response in the cortex is under the control of the noradrenergic system while the alpha potentiation response is under the control of the adrenocortical system.