title: Activation of muscarinic acetylcholine receptors elevates intracellular Ca(2+) concentrations in accessory lobe neurons of the chick.
abstract: Accessory lobes are protrusions located at the lateral sides of the spinal cord of chicks and it has been proposed that they play a role as a sensory organ for equilibrium during walking. We have reported that functional neurons exist in the accessory lobe. As there is histological evidence that synaptic terminals of cholinergic nerves exist near the somata of accessory lobe neurons, we examined the effects of acetylcholine on changes in intracellular Ca2+ concentrations ([Ca2+]i), as an index of cellular activities. Acetylcholine (0.1-100 µM) caused a transient rise in the [Ca2+]i. Acetylcholine-evoked [Ca2+]i rises were observed in the absence of extracellular Ca2+, and they were abolished in the presence of cyclopiazonic acid, an inhibitor of Ca2+-ATPase of intracellular Ca2+ stores or atropine, a muscarinic receptor antagonist. mRNAs coding M3 and M5 isoforms of the muscarinic receptors were detected in accessory lobes by the RT-PCR. These results indicate that chick accessory lobe neurons express functional muscarinic acetylcholine receptors, and that acetylcholine stimulates Ca2+ mobilization from intracellular Ca2+ stores, which elevates the [Ca2+]i in the somata of accessory lobe neurons, through activation of these receptors. Cholinergic synaptic transmission to the accessory lobe neurons may regulate some cellular functions through muscarinic receptors.
authors.affiliation: Laboratory of Veterinary Physiology, Joint Department of Veterinary Medicine, Faculty of Agriculture, Tottori University, 4-101, Koyama-cho Minami, Tottori, 680-8553, Japan.
authors.forename: Keita
authors.initials: K
authors.lastname: Takahashi
authors.forename: Naoki
authors.initials: N
authors.lastname: Kitamura
authors.forename: Yuki
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Yuko
authors.initials: Y
authors.lastname: Yamanaka
authors.forename: Hikaru
authors.initials: H
authors.lastname: Shinohara
authors.forename: Izumi
authors.initials: I
authors.lastname: Shibuya
mesh_terms: D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D030161:Avian Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D002478:Cells, Cultured; D002642:Chick Embryo; D002645:Chickens; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism*; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D059368:RNA Isoforms / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000378:metabolism*; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism*
chemical_list: D030161:Avian Proteins; D004791:Enzyme Inhibitors; D007211:Indoles; D018727:Muscarinic Antagonists; D059368:RNA Isoforms; D012333:RNA, Messenger; D011976:Receptors, Muscarinic; D001285:Atropine; D000252:Calcium-Transporting ATPases; D000109:Acetylcholine; D002118:Calcium; C000543:cyclopiazonic acid