title: Spontaneous and CRH-Induced Excitability and Calcium Signaling in Mice Corticotrophs Involves Sodium, Calcium, and Cation-Conducting Channels.
abstract: Transgenic mice expressing the tdimer2(12) form of Discosoma red fluorescent protein under control of the proopiomelanocortin gene's regulatory elements are a useful model for studying corticotrophs. Using these mice, we studied the ion channels and mechanisms controlling corticotroph excitability. Corticotrophs were either quiescent or electrically active, with a 22-mV difference in the resting membrane potential (RMP) between the 2 groups. In quiescent cells, CRH depolarized the membrane, leading to initial single spiking and sustained bursting; in active cells, CRH further facilitated or inhibited electrical activity and calcium spiking, depending on the initial activity pattern and CRH concentration. The stimulatory but not inhibitory action of CRH on electrical activity was mimicked by cAMP independently of the presence or absence of arachidonic acid. Removal of bath sodium silenced spiking and hyperpolarized the majority of cells; in contrast, the removal of bath calcium did not affect RMP but reduced CRH-induced depolarization, which abolished bursting electrical activity and decreased the spiking frequency but not the amplitude of single spikes. Corticotrophs with inhibited voltage-gated sodium channels fired calcium-dependent action potentials, whereas cells with inhibited L-type calcium channels fired sodium-dependent spikes; blockade of both channels abolished spiking without affecting the RMP. These results indicate that the background voltage-insensitive sodium conductance influences RMP, the CRH-depolarization current is driven by a cationic conductance, and the interplay between voltage-gated sodium and calcium channels plays a critical role in determining the status and pattern of electrical activity and calcium signaling.
authors.affiliation: Department of Cellular and Molecular Neuroendocrinology, Institute of Physiology Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic (H.Z.); and Sections on Cellular Signaling (H.Z., M.T., M.K., S.S.S.) and Endocrine Physiology (G.A.), Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-4510.
authors.forename: Hana
authors.initials: H
authors.lastname: Zemkova
authors.affiliation: Department of Cellular and Molecular Neuroendocrinology, Institute of Physiology Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic (H.Z.); and Sections on Cellular Signaling (H.Z., M.T., M.K., S.S.S.) and Endocrine Physiology (G.A.), Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-4510.
authors.forename: Melanija
authors.initials: M
authors.lastname: Tomić
authors.affiliation: Department of Cellular and Molecular Neuroendocrinology, Institute of Physiology Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic (H.Z.); and Sections on Cellular Signaling (H.Z., M.T., M.K., S.S.S.) and Endocrine Physiology (G.A.), Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-4510.
authors.forename: Marek
authors.initials: M
authors.lastname: Kucka
authors.affiliation: Department of Cellular and Molecular Neuroendocrinology, Institute of Physiology Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic (H.Z.); and Sections on Cellular Signaling (H.Z., M.T., M.K., S.S.S.) and Endocrine Physiology (G.A.), Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-4510.
authors.forename: Greti
authors.initials: G
authors.lastname: Aguilera
authors.affiliation: Department of Cellular and Molecular Neuroendocrinology, Institute of Physiology Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic (H.Z.); and Sections on Cellular Signaling (H.Z., M.T., M.K., S.S.S.) and Endocrine Physiology (G.A.), Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-4510.
authors.forename: Stanko S
authors.initials: SS
authors.lastname: Stojilkovic
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D016718:Arachidonic Acid / Q000494:pharmacology; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects*; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D052680:Corticotrophs / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology*; D000242:Cyclic AMP / Q000378:metabolism; D005260:Female; D007473:Ion Channels / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D018408:Patch-Clamp Techniques; D012964:Sodium / Q000378:metabolism*
chemical_list: D020746:Calcium Channels, L-Type; D007473:Ion Channels; D005576:Colforsin; D016718:Arachidonic Acid; D003994:Bucladesine; D003346:Corticotropin-Releasing Hormone; D012964:Sodium; D000242:Cyclic AMP; D002118:Calcium