Secretion of catecholamines from adrenal gland by a single electrical shock: electronic depolarization of medullary cell membrane.

Transmural stimulation of the isolated adrenal gland of the rat and guinea pig results in secretion of catecholamine. The secretion is due to activation of cholinergic receptors of the adrenal medulla by acetylcholine released from splanchnic nerve terminals after transmural stimulation. Our aim was to see whether the same experimental technique could be used to directly excite the adrenal medullary cell membrane by electrical stimulation and whether such stimulation would result in secretion of catecholamines. We demonstrate here that a single electrical shock to the perfused adrenal gland of the rat results in massive secretion of epinephrine and norepinephrine. The secretion is directly related to the strength and duration of the applied stimulus over a wide range. Catecholamine secretion is unaffected by tetrodotoxin or hexamethonium/atropine but is abolished by Ca2+ lack or 3 mM Mn2+. We suggest that the adrenal medullary membrane undergoes nonpropagated electrotonic depolarization on electric stimulation and thereby voltage-dependent Ca2+ channels are opened to initiate secretion.