title: Retinal bipolar cell input mechanisms in giant danio. III. ON-OFF bipolar cells and their color-opponent mechanisms.
abstract: Whole cell patch recording was performed from morphologically identified cone-driven on-off bipolar cells (Cabs) in giant danio retinal slices to study their glutamate receptors and light-evoked responses. Specific agonists were puffed in the presence of cobalt, picrotoxin, and strychnine to identify glutamate receptors on these cells. Most Cabs responded to both the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)/kainate receptor agonist kainate and the excitatory amino acid transporter (EAAT) substrate D-aspartate, and both responses were localized to the dendrites. Kainate generated depolarizations whereas D-aspartate had E(rev) close to E(Cl) and generated hyperpolarizations, indicating that the AMPA/kainate receptors are sign-preserving, whereas the EAATs are sign-inverting. In response to white light, some Cabs gave on bipolar cell-like responses whereas others gave off bipolar cell-like ones, but many cells' responses had both on and off bipolar cell components. In response to appropriately colored center-selective stimuli, many Cabs responded to short and long wavelengths with opposite polarities and were thus double color-opponent. The depolarizing components of the responses to white or colored stimuli were suppressed by the EAAT blocker DL-threo-beta-benzyloxyaspartate (TBOA), whereas the hyperpolarizing components were reduced by the AMPA/kainate receptor antagonist 6,7-dinitroquinoxaline-2,3-dione (DNQX). These results are consistent with the hypothesis that both EAATs and AMPA/kainate receptors are involved in the generation of light-evoked responses in Cabs and that they confer these cells with on and off bipolar cell properties, respectively. Cabs can generate double color-opponent center responses by receiving inputs from certain cones through EAATs and from other cones through AMPA/kainate receptors.
authors.affiliation: Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, USA. Kwoon_Wong@brown.edu
authors.forename: Kwoon Y
authors.initials: KY
authors.lastname: Wong
authors.forename: John E
authors.initials: JE
authors.lastname: Dowling
mesh_terms: D000818:Animals; D001224:Aspartic Acid / Q000494:pharmacology; D003116:Color; D026603:D-Aspartic Acid / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D066298:In Vitro Techniques; D007608:Kainic Acid / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D009474:Neurons / Q000145:classification / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D018408:Patch-Clamp Techniques; D010775:Photic Stimulation / Q000379:methods; D011422:Propionates / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D012160:Retina / Q000166:cytology*; D014795:Visual Pathways / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D015027:Zebrafish / Q000502:physiology*
chemical_list: C114785:2-amino-4-phosphono-propinate; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D011422:Propionates; D011810:Quinoxalines; C120673:benzyloxyaspartate; D001224:Aspartic Acid; D026603:D-Aspartic Acid; C056723:FG 9041; D007608:Kainic Acid