ABSTRACT
Histamine is an important cell-to-cell messenger in the body, with activity at four types of G protein-coupled receptors (H 1-, H r , Hr , and H 4-receptors). In this chapter, we focus on the role of histamine at Hr and H 2-receptors in urticaria. Information about the HI-receptor and the Hrreceptor, including expression, signal transd uction, and function is summarized in Table I (I). The role of histamine at H 3-and H 4-receptors in urticaria has yet to be determined.
