title: Adenosine suppresses exocytosis from cone terminals of the salamander retina.
abstract: In the retina, adenosine is released in the dark and has been shown to inhibit Ca2+ influx through voltage-gated Ca2+ channels in cones. Therefore, we tested whether adenosine can inhibit exocytosis from isolated cone photoreceptors. Simultaneous measurements of membrane exocytosis and Ca2+ were made from cones using the activity-dependent dye, Synaptored-C2, and the Ca2+ indicator dye, Fluo-4. Adenosine suppressed exocytosis in cones, indicating that transmitter release is also reduced from cone terminals, and further supports an inhibitory mechanism for modulating transmitter release onto second-order neurons. Furthermore, this raises the possibility that adenosine might be neuroprotective for photoreceptors and second-order neurons by suppressing Ca2+ levels in cones and reducing exocytosis of L-glutamate, respectively.
authors.affiliation: Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, California 90095-1763, USA. sstella@mednet.ucla.edu
authors.forename: Salvatore L
authors.initials: SL
authors.lastname: Stella
authors.forename: Wanda D
authors.initials: WD
authors.lastname: Hu
authors.forename: Nicholas C
authors.initials: NC
authors.lastname: Brecha
mesh_terms: D000241:Adenosine / Q000378:metabolism* / Q000494:pharmacology; D000557:Ambystoma / Q000033:anatomy & histology / Q000378:metabolism*; D000814:Aniline Compounds; D000818:Animals; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D019610:Cytoprotection / Q000187:drug effects / Q000502:physiology; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D018698:Glutamic Acid / Q000378:metabolism; D007202:Indicators and Reagents; D007700:Kinetics; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D018377:Neurotransmitter Agents / Q000378:metabolism; D009924:Organ Culture Techniques; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism*; D011726:Pyridinium Compounds; D017949:Retinal Cone Photoreceptor Cells / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D014785:Vision, Ocular / Q000187:drug effects / Q000502:physiology; D014966:Xanthenes
chemical_list: D000814:Aniline Compounds; D015220:Calcium Channels; C409648:Fluo 4; D007202:Indicators and Reagents; C508379:N-(3-trimethylammoniumpropyl)-4-(6-(4-(diethylamino)phenyl)hexatrienyl)pyridinium; D018377:Neurotransmitter Agents; D011726:Pyridinium Compounds; D014966:Xanthenes; D018698:Glutamic Acid; D000241:Adenosine; D011188:Potassium