The responsiveness of human eccrine sweat glands to choline and carbachol. Application to the study of peripheral cholinergic functioning in Alzheimer-type dementia.

The responsiveness of human eccrine sweat glands to intradermally injected choline and carbachol was studied in vivo using a plastic paint impression method. Both drugs exerted consistent dose-related effects, choline being significantly less potent than carbachol. The responses to both drugs attained a maximum level approximately 3 min after the injection, but the responses to choline had a less pronounced peak and declined more slowly than the response to carbachol. The response to choline, but not the response to carbachol, was antagonised by hemicholinium-3. Young males showed greater responsiveness to both drugs than young females, this being reflected in higher maxima of the dose-response curves obtained for the males. Smaller responses to both drugs were observed in old females than in young females, this being reflected in lower maxima of the dose-response curves obtained for the elderly group. A group of elderly female patients with clinical diagnoses of Alzheimer-type dementia showed smaller responses to both drugs than the group of non-demented elderly females. The results show that choline can stimulate eccrine sweat glands, possibly by an indirect mechanism involving active uptake and metabolic conversion to acetylcholine. The reduced responsiveness seen in the patients suffering from Alzheimer-type dementia could reflect either a loss of function of cholinergic sympathetic neurones or impaired functioning of the sweat glands themselves.