DIMAPRIT - [S-[3-(N,N-DIMETHYLAMINO)PROPYL]ISOTHIOUREA] - A HIGHLY SPECIFIC HISTAMINE H-2-RECEPTOR AGONIST .1. PHARMACOLOGY

S-[3-(N,N-Dimethylamino)propyl]isothiourea (dimaprit), has been shown to be a highly specific histamine H-2-receptor agonist. Parallel line assays showed that in vitro at H-2-receptors it had approximately 17.5 % the activity of histamine on the rat uterus and 71% on the guinea-pi g right atrium, with similar maximal responses; it had less than 0.000 1% the activity of histamine on H-1-receptors. Dimaprit stimulated gas tric acid secretion in the rat, dog and cat in which it had, respectiv ely, approximately 19, SS and 400-500% the activity of histamine. In t he dog and cat the maximum secretory response to dimaprit was signific antly greater than that obtained to histamine. The H-2-receptor specif icity of dimaprit in causing depressor and vasodilator effects was als o demonstrated in the cat, in which it had 18-20% of the H-2-receptor activity of histamine. Dimaprit should prove to be a very useful tool in studies examining the role of histamine in physiology and pathology . The absence of marked cardiovascular effects at doses maximal for th e stimulation of gastric acid secretion, as seen in the cat studies, c ould lead to this compound being of value as a diagnostic agent in the measurement of maximal acid secretory capacity.