Histamine H2 receptor
H receptors are positively coupled to adenylate cyclase via G. It is a potent stimulant of cAMP production, which leads to activation of protein kinase A. PKA functions to phosphorylate certain proteins, affecting their activity. The drug betazole is an example of a histamine H receptor agonist. Function. Histamine is a ubiquitous messenger molecule released from mast cells, enterochromaffin-like cells, and neurons. Its various actions are mediated by histamine receptors H, H, H and H. The histamine receptor H belongs to the rhodopsin-like family of G protein-coupled receptors. It is an integral membrane protein  and stimulates gastric acid secretion. It also regulates gastrointestinal motility and intestinal secretion and is thought to be involved in regulating cell growth and differentiation. Tissue distribution. Histamine H receptors are expressed in the following tissues: Physiological responses. Activation of the H receptor results in the following physiological responses: