LOCAL NONSYNAPTIC MODULATION OF ALDOSTERONE PRODUCTION BY CATECHOLAMINES AND ATP IN RAT - IMPLICATIONS FOR A DIRECT NEURONAL FINE-TUNING

In addition to hypophyseal control, steroid synthesis and secretion in the adrenal cortex is also under direct local neural modulation. We o btained morphological and neurochemical evidence that a substantial pr oportion of the noradrenergic nerve endings lie in close proximity to zona glomerulosa cells without making synaptic contact, thus providing evidence for a direct local modulatory role of catecholamines in ster oid secretion. These noradrenergic neurones, like other noradrenergic neurones in the central nervous system, are able to take up dopamine ( DA), convert it partly into noradrenaline (NA) and to release both NA and DA together with the co-transmitter ATP when neuronal activity dri ves them to do so. These catecholamines and ATP may reach zona glomeru losa cells via diffusion in a paracrine way and modulate the synthesis of aldosterone. The presence of ecto-Ca-ATPases, enzymes that may ter minate the effect of ATP, was demonstrated around the nerve profiles i ndicating that not only ATP but its metabolites (ADP, AMP, adenosine) can also influence the production of aldosterone. These data strongly support the possibility of a paracrine, non-synaptic modulatory role o f catecholamines and ATP in the regulation of adrenocortical steroid s ecretion.