title: Calcium from internal stores triggers GABA release from retinal amacrine cells.
abstract: The Ca(2+) that promotes transmitter release is generally thought to enter presynaptic terminals through voltage-gated Ca(2+)channels. Using electrophysiology and Ca(2+) imaging, we show that, in amacrine cell dendrites, at least some of the Ca(2+) that triggers transmitter release comes from endoplasmic reticulum Ca(2+) stores. We show that both inositol 1,4,5-trisphosphate receptors (IP(3)Rs) and ryanodine receptors (RyRs) are present in these dendrites and both participate in the elevation of cytoplasmic [Ca(2+)] during the brief depolarization of a dendrite. Only the Ca(2+) released through IP(3)Rs, however, seems to promote the release of transmitter. Antagonists for the IP(3)R reduced transmitter release, whereas RyR blockers had no effect. Application of an agonist for metabotropic glutamate receptor, known to liberate Ca(2+) from internal stores, enhanced both spontaneous and evoked transmitter release.
authors.affiliation: Section of Neurobiology, Physiology and Behavior, Division of Biological Sciences, University of California, Davis, 95616, USA.
authors.forename: Ajithkumar
authors.initials: A
authors.lastname: Warrier
authors.forename: Salvador
authors.initials: S
authors.lastname: Borges
authors.forename: David
authors.initials: D
authors.lastname: Dalcino
authors.forename: Cameron
authors.initials: C
authors.lastname: Walters
authors.forename: Martin
authors.initials: M
authors.lastname: Wilson
mesh_terms: D025042:Amacrine Cells / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D001896:Boron Compounds / Q000494:pharmacology; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism; D000697:Central Nervous System Stimulants / Q000494:pharmacology; D002642:Chick Embryo; D003952:Diagnostic Imaging / Q000379:methods; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004558:Electric Stimulation / Q000379:methods; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D006493:Heparin / Q000494:pharmacology; D007150:Immunohistochemistry / Q000379:methods; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D018613:Microscopy, Confocal / Q000379:methods; D009930:Organic Chemicals / Q000378:metabolism; D018408:Patch-Clamp Techniques / Q000379:methods; D010648:Phenylacetates / Q000494:pharmacology; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D012160:Retina / Q000166:cytology*; D012433:Ryanodine / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D013997:Time Factors; D005680:gamma-Aminobutyric Acid / Q000378:metabolism* / Q000494:pharmacology
chemical_list: C107349:2-chloro-5-hydroxyphenylglycine; D001896:Boron Compounds; D015220:Calcium Channels; D002135:Calcium-Binding Proteins; D000697:Central Nervous System Stimulants; D018690:Excitatory Amino Acid Agonists; D053496:Inositol 1,4,5-Trisphosphate Receptors; C403124:Oregon Green BAPTA-dextran; D009930:Organic Chemicals; D010648:Phenylacetates; D018160:Receptors, Cytoplasmic and Nuclear; D019837:Ryanodine Receptor Calcium Release Channel; D012433:Ryanodine; D002110:Caffeine; D005680:gamma-Aminobutyric Acid; D006493:Heparin; C109986:2-aminoethoxydiphenyl borate; D002118:Calcium; D005998:Glycine