ABSTRACT
In this chapter, the author focuses on the distribution and functional role of H3 receptors in peripheral tissues, with particular attention to the gastrointestinal tract, cardiovascular, respiratory, and immune systems. The antiinflammatory and antiallergic effects of H4 receptor antagonists observed in various in vitro and in vivo models have opened a new window for therapeutic approaches in inflammation and allergy. The leading role of histamine in the intricate network-regulating acid production was definitely assessed with the discovery of H2 receptors and the enormous clinical impact of H2 receptor blockers in the treatment of peptic ulcer disease. Histamine has several actions in the airway and may be an important mediator in asthma. The first evidence for the existence of H3 receptor in the cardiovascular system was found in the guinea pig mesenteric artery, where histamine attenuated the amplitude of electrically evoked excitatory junction potentials.
