Abstract
5-Hydroxytryptamine (5-HT) and histamine were released when antigen was added to peritoneal cell suspensions or to the fluid perfusing the small intestine of sensitized rats. In parallel experiments with minced uterine tissue the antigen failed to release significant amounts of histamine into the suspending medium but did release 5-HT. These results, taken in conjunction with the effects of the two amines and of their specific antagonists, suggest that the anaphylactic response of the rat uterus depends on the release of 5-HT, whereas both histamine and 5-HT participate in the anaphylactic response of other rat tissues.