title: Stimulation of bursting in pre-Bötzinger neurons by Epac through calcium release and modulation of TRPM4 and K-ATP channels.
abstract: The exchange factor directly activated by cAMP (Epac) can couple cAMP production to the activation of particular membrane and cytoplasmic targets. Using patch-clamp recordings and calcium imaging in organotypic brainstem slices, we examined the role of Epac in pre-Bötzinger complex, an essential part of the respiratory network. The selective agonist 8-(4-chlorophenylthio)-2'-O-methyl-cAMP (8-pCPT) sensitized calcium mobilisation from inositol-1,4,5-trisphosphate-sensitive internal stores that stimulated TRPM4 (transient receptor potential cation channel, subfamily M, Melastatin) channels and potentiated the bursts of action potentials. 8-pCPT actions were abolished after inhibition of phospholipase C with U73122 and depletion of calcium stores with thapsigargin. Caffeine-sensitive release channels were not modulated by 8-pCPT. Epac inhibited ATP-sensitive K(+) channels that also led to the enhancement of bursting by 8-pCPT. Bursting activity, spontaneous calcium transients and activity of TRPM4 and ATP-sensitive K(+) channels were potentiated after brief exposures to bradykinin and incubation with wortmannin produced opposite effects that can be explained by changes in phosphatidylinositol 4,5-bisphosphate levels. 8-pCPT stimulated the respiratory motor output in functionally intact preparations and the effects of bradykinin and wortmannin were identical to those observed in organotypic slices. The data thus indicate a novel pathway of controlling bursting activity in pre-Bötzinger complex neurons through Epac that can involved in reinforcement of the respiratory activity by cAMP.
authors.affiliation: DFG-Center of Molecular Physiology of the Brain, Department of Neuro- and Sensory Physiology, Georg-August-University, Göttingen, Germany. smirono@gwdg.de
authors.forename: Sergej L
authors.initials: SL
authors.lastname: Mironov
authors.forename: Ekaterina Y
authors.initials: EY
authors.lastname: Skorova
mesh_terms: D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D055592:Biophysical Phenomena / Q000187:drug effects; D001920:Bradykinin / Q000494:pharmacology; D001933:Brain Stem / Q000166:cytology*; D002118:Calcium / Q000378:metabolism*; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D031541:Fluorescence Resonance Energy Transfer; D066298:In Vitro Techniques; D054086:KATP Channels / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects* / Q000502:physiology; D051379:Mice; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D018408:Patch-Clamp Techniques; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D011760:Pyrrolidinones / Q000494:pharmacology; D050053:TRPM Cation Channels / Q000378:metabolism*; D000077191:Wortmannin
chemical_list: C473217:8-(4-chloro-phenylthio)-2'-O-methyladenosine-3'-5'-cyclic monophosphate; D000730:Androstadienes; D004791:Enzyme Inhibitors; D004963:Estrenes; D018691:Excitatory Amino Acid Antagonists; D054086:KATP Channels; D019269:Phosphatidylinositol 4,5-Diphosphate; D011760:Pyrrolidinones; D050053:TRPM Cation Channels; C476766:TRPM4 protein, mouse; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D000242:Cyclic AMP; D001920:Bradykinin; D002118:Calcium; D000077191:Wortmannin