DISTRIBUTION OF ACETYLCHOLINE AND HISTAMINE IN NETTLE PLANTS

Abstract

In a previous paper we have described the occurrence of acetylcholine, histamine and a third unidentified smooth muscle-contracting substance in the hair fluid of Urtica urens, the annual nettle. The vascular reactions produced in the human skin and the sensations elicited by the sting of the nettle hair could be accounted for by the combined effect of acetylcholine and histamine. Both substances were also found in the leaf tissue (Emmelin & Feldberg, '947). In the experiments described in the present paper it could be shown that acetylcholine and histamine occur also in high concentrations in the hair fluid of the perennial nettle, U. dioica. No experiments have been carried out on the occurrence of the third unidentified smooth muscle-contracting substance, but the distribution of histamine and acetylcholine in the annual and perennial plant have been examined in more detail. Since the publication of our previous experiments our attention has been drawn to a paper by Starkenstein & Wasserstrom (I933) who had found that extracts of whole nettle plants caused contractions of smooth muscles, a fall in arterial blood pressure and inhibition of the heart. No indication was given as to the nature of the substance or substances responsible for these effects. In the light of the experiments presented in this paper, histamine and acetylcholine were probably the active principles, or at least the main active principles in their extracts.