Dopamine modulates voltage-activated potassium currents in zebrafish retinal on bipolar cells.
We report a study of the characterization of voltage-activated potassium (K+) currents in retinal ON bipolar cells in zebrafish. At single-channels levels, the open probability of the K+ channels increased when the membrane potential was increased. The maximal open proportion was 0.76+/-0.05 under our testing conditions. In whole-cell recordings, the K+ current displayed two exponential components with the activation time constants of 11-22 msec (tau1) and 0.8-4 msec (tau2). Dopamine modulated the K+ current. Dopamine reduced the time constant tau2 when the membrane potential was depolarized to high voltages. A decrease in K+ current was seen when dopamine D1 receptors were selectively activated by SKF38393 or when the D1 receptor-coupled G-proteins were activated by GTP-gamma-S. The activation of adenylate cyclase by forskolin or the increase of intracellular cAMP concentrations by 8-Br-cAMP or Sp-cAMPS also resulted in a decrease in K+ current. Together, the data suggest that dopamine modulates the K+ current via D1 receptor-coupled G-protein pathways.
Yu
Chuan-Jiang
CJ
Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana 46556, USA.
Li
Lei
L
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism* / Q000494:pharmacology; D018491:Dopamine Agonists / Q000494:pharmacology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D024642:Potassium Channels, Voltage-Gated / Q000187:drug effects / Q000378:metabolism*; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D017447:Receptors, Dopamine D1 / Q000819:agonists / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled / Q000819:agonists / Q000378:metabolism*; D012160:Retina / Q000187:drug effects / Q000378:metabolism*; D051245:Retinal Bipolar Cells / Q000187:drug effects / Q000378:metabolism*; D015027:Zebrafish
D018491:Dopamine Agonists; D024642:Potassium Channels, Voltage-Gated; D017447:Receptors, Dopamine D1; D043562:Receptors, G-Protein-Coupled; D015124:8-Bromo Cyclic Adenosine Monophosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D000242:Cyclic AMP; D004298:Dopamine