Histamine

HISTAMINE

Histamine was synthesized in 1907 and later isolated from mam-malian tissues. Early hypotheses concerning the possible physio-logic roles of tissue histamine were based on similarities between the effects of intravenously administered histamine and the symp-toms of anaphylactic shock and tissue injury. Marked species variation is observed, but in humans histamine is an important mediator of immediate allergic (such as urticaria) and inflamma-tory reactions, although it plays only a modest role in anaphylaxis. Histamine plays an important role in gastric acid secretion  and functions as a neurotransmitter and neuromodu-lator. Newer evidence indicates that his-tamine also plays a role in immune functions and chemotaxis of white blood cells.