title: Components of pacemaker potentials recorded from the guinea pig stomach antrum.
abstract: Pacemaker potentials recorded intracellularly from the guinea pig stomach consisted of initial primary and following plateau components. Inhibition of the internal Ca2+ store pump with cyclopiazonic acid depolarized the membrane and inhibited the plateau component of pacemaker potentials. 2-aminoethoxydiphenyl borate (an inhibitor of IP3-induced Ca2+ release) and carbonyl cyanide m-chlorophenyl-hydrazone (a mitochondrial protonophore) depolarized the membrane and abolished pacemaker potentials. Low [Ca2+]o solution reduced the frequency and rate of rise of pacemaker potentials, and the effects were mimicked by BAPTA-AM (an intracellular Ca2+ chelator). 4,4-diisothiocyanatostilbene-2,2-disulphonic acid and low [Cl-]o solution inhibited the plateau component of pacemaker potentials. Depolarization of the membrane with high [K+]o solutions increased the frequency and reduced the dV/dt(max) of pacemaker potentials. During high-[K+]o-induced depolarization, cyclopiazonic acid abolished pacemaker potentials. Caffeine, forskolin, papaverine, 8-bromo-cGMP and (+/-)S-nitroso-N-acetylpenicillamine (SNAP) inhibited the plateau component, with no alteration of the primary component. It is concluded that the primary and plateau components of pacemaker potentials are related to voltage-gated Ca2+ influx and Ca2+-activated Cl- channels, respectively, and cyclic nucleotides inhibit mainly the latter. Pacemaker potentials may be generated by the release of Ca2+ from internal stores through excitation of inositol 1,4,5-trisphosphate receptors, coupled with Ca2+ uptake into mitochondria.
authors.affiliation: Department of Physiology, Nagoya City University Medical School, Mizuho-ku, Nagoya 467-8601, Japan.
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Kito
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Fukuta
authors.forename: Hikaru
authors.initials: H
authors.lastname: Suzuki
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000818:Animals; D001683:Biological Clocks / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002712:Chlorides / Q000008:administration & dosage; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D005110:Extracellular Space / Q000378:metabolism; D005260:Female; D006168:Guinea Pigs; D008297:Male; D009130:Muscle, Smooth / Q000502:physiology; D009994:Osmolar Concentration; D011188:Potassium / Q000378:metabolism; D011706:Pyloric Antrum / Q000502:physiology*; D012996:Solutions / Q000494:pharmacology
chemical_list: D002712:Chlorides; D012996:Solutions; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D000242:Cyclic AMP; D006152:Cyclic GMP; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D011188:Potassium; D002118:Calcium