IDENTIFICATION OF 5‐HYDROXYTRYPTAMINE IN THE STING OF THE NETTLE <i>(URTICA DIOICA)</i>

Abstract

showed that there were three smooth-muscle stimulating substances in the sting of the nettle: acetylcholine (ACh), histamine, and a third they did not identify. They described six properties of this unidentified third substance: constriction of the blood vessels of rabbit's ear; stimulation of in vitro preparations of rabbit's and guinea-pig's small intestine; lowering of rabbit's blood pressure; solubility in ether; and instability to boiling in alkaline solution. Since these properties coincided with those of 5-hydroxytryptamine (5-HT) subsequently described, we explored the possibility that the third substance of Emmelin and Feldberg might be 5-HT. Demonstration that this was so has already been briefly reported (Chesher and Collier, 1955) and the present paper sets out the detailed evidence on which identification rests and describes further investigations of nettle sting.