title: Identification and role of muscarinic receptor subtypes expressed in rat adrenal medullary cells.
abstract: The muscarinic receptor is known to be involved in the acetylcholine (ACh)-induced secretion of catecholamines in the adrenal medullary (AM) cells of various mammals. The muscarinic receptor subtype involved and its physiological role, however, have not been elucidated yet. Thus, we investigated these issues in acutely isolated rat AM cells and perfused rat adrenal medulla. The RT-PCR analysis revealed the presence of M(2), M(3), M(4), and M(5) mRNAs. Immunocytochemistry with specific antibodies showed that M(5)-like immunoreactivities (IRs) were detected at half the cell membrane area, which was much larger than that with M(3)- or M(4)-like IRs. Muscarine produced inward currents in a dose-dependent manner. Pilocarpine, McN-A-343, and oxotremorine were less efficient than muscarine; and RS-86, which has no action on the M(5) receptor, produced no current. Electrical stimulation of nerve fibers produced a frequency-dependent increase in the Ca(2+) signal in perfused adrenal medullae. Muscarinic receptors were found to be involved in neuronal transmission in AM cells in the presence of a cholinesterase inhibitor, which suppresses ACh degradation. We concluded that the M(5) receptor is the major muscarinic receptor subtype in rat AM cells and may be involved in neuronal transmission under conditions where ACh spills over the synapse.
authors.affiliation: Department of Cell and Systems Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan.
authors.forename: Keita
authors.initials: K
authors.lastname: Harada
authors.forename: Hidetada
authors.initials: H
authors.lastname: Matsuoka
authors.forename: Takeyoshi
authors.initials: T
authors.lastname: Sata
authors.forename: Akira
authors.initials: A
authors.lastname: Warashina
authors.forename: Masumi
authors.initials: M
authors.lastname: Inoue
mesh_terms: D000313:Adrenal Medulla / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D020013:Calcium Signaling; D002462:Cell Membrane / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D057809:HEK293 Cells; D006801:Humans; D009116:Muscarine / Q000008:administration & dosage / Q000494:pharmacology; D018721:Muscarinic Agonists / Q000494:pharmacology*; D009412:Nerve Fibers / Q000187:drug effects / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D043642:Receptor, Muscarinic M5 / Q000378:metabolism*; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D018721:Muscarinic Agonists; D043642:Receptor, Muscarinic M5; D011976:Receptors, Muscarinic; D009116:Muscarine