The effect of catecholamines on unit activity in afferent nerves from the adrenal glands.

1. Afferent discharges were observed in dissected filaments of nerves to the adrenal gland in the rabbit and cat.2. Systemic intravenous and close intra-arterial injections of (-)-adrenaline and (-)-noradrenaline caused cessation or depression of the spontaneous firing rate.3. Intravenous injection of acetylcholine and electrical stimulation of the splanchnic nerve also depressed the afferent discharge rate.4. Modification of blood pressure levels by chemical and mechanical means did not modify the afferent discharge.5. Alpha blocking agents (ergotamine and phenoxybenzamine) blocked the effect of (-)-adrenaline on the firing rate. Beta blocking agents (dichloroisoprenaline and propranolol) were without effect.6. It is suggested that an afferent system is present in the adrenal gland. Within this system are chemosensitive receptors which may constitute the afferent limb of a local feed-back loop involved in adrenal catecholamine release.