Biol. Pharm. Bull. 28(12) 2220—2224 (2005)

ment and spice, has been used therapeutically in traditional folk medicine for a wide range of ailments, including wound healing, urinary tract infection, and liver ailments. Although evidence suggests that a C. longa extract also has considerable gastroprotective and antiulcerogenic effects, its mechanism of action remains unclear. The genes encoding four histamine receptor subtypes (H1, H2, H3 and H4) have been cloned, and the receptors have been pharmacologically characterized, along with their signaling pathways. The H2 histamine receptor (H2R) is a seven transmembrane G protein-coupled receptor (GPCR) coupled to the enzyme adenylyl cyclase, which produces the intracellular second messenger, cyclic AMP. H2R, which is expressed by various tissues, including the brain, stomach, heart, and lung, is involved in histamine-induced gastric acid secretion. In gastric parietal cells especially, H2R triggers the secretion of acid (HCl) into the stomach lumen through cAMP/protein kinase A/proton pump pathway. Hence, H2R blockers may be useful for treating diseases that involve gastric acid hyper-secretion, such as stomach ulcers and reflux esophagitis. We hypothesized that the gastroprotective and antiulcerogenic effects of C. longa extract may be related with the H2R signaling pathway. We found that this extract selectively inhibited the activation of H2R and protected the stomach from gastric acid induced ulcers.