Role of circulating catecholamines in human eccrine sweat gland control.

1. Intra-arterially as well as intradermally administered adrenaline or noradrenaline produces a sweat response. 2. The intensity of the intradermal response is always considerably less than that due to acetylcholine and the threshold of effective concentration is considerably greater than for acetylcholine. The glands also fail to respond to repeated small doses of intradermal catecholamine and to continued arterial catecholamine infusion. 3. Intradermal administration of a mixture of adrenaline and acetylcholine did not indicate that adrenaline potentiates the cholinergic response. 4. Intravenous infusions of 20 pg/min adrenaline neither produce a response by the resting glands nor affect the response of the active glands. Whilst intra-arterial infusions of high doses of adrenaline or noradrenaline produce a response by the resting glands they reduce the response of the active glands. 5. The results show that even though the catecholamine levels in a discharge of a phaeochromocytoma can be high enough to cause a discharge by resting glands, as the glands are likely to be secreting in response to neural stimulation, the effect of the secreted catecholamine would be inhibitory.