title: Tiotidine and ICIA 5165 inhibit central and peripheral H2 receptors with equal potency.
abstract: Histamine, acting through H2 receptors, increases cAMP formation in homogenates of guinea pig hippocampus. The activities of two H2 antagonists, tiotidine and ICIA 5165, as inhibitors of the histamine-induced increase were investigated. ICIA 5165 and tiotidine were potent antagonists of histamine with a pKi of 8.0 and 7.6, respectively. Similarly, the positive chronotropic response of isolated guinea pig atria to histamine was antagonized by tiotidine and ICIA 5165 with a pKB of 7.8 and 7.9, respectively. These studies suggest that histamine H2 receptors in the CNS and atria are similar.
mesh_terms: D000067956:Adenylyl Cyclase Inhibitors; D000818:Animals; D002927:Cimetidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006146:Guanidines / Q000494:pharmacology*; D006168:Guinea Pigs; D006339:Heart Rate / Q000187:drug effects; D006624:Hippocampus / Q000187:drug effects* / Q000201:enzymology; D006632:Histamine / Q000494:pharmacology; D006635:Histamine H2 Antagonists; D066298:In Vitro Techniques; D008297:Male; D013844:Thiazoles / Q000494:pharmacology*
chemical_list: D000067956:Adenylyl Cyclase Inhibitors; D006146:Guanidines; D006635:Histamine H2 Antagonists; D013844:Thiazoles; C050212:2-guanidino-4-(4-(2-cyano-3-methylguanidino)butyl)thiazole; D002927:Cimetidine; D006632:Histamine; C023990:tiotidine