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C. Yu, L. Li; The Effect of Dopamine on the ON Bipolar Cell Outward K+ Current Is Lost in Mutant Zebrafish . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4140.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To test if exogenous dopamine is effective in modulating the ON bipolar cell outward K+ current in mutant zebrafish, night blindness b (nbb). The nbb mutants are characterized by the disruption of olfactoretinal centrifugal innervation and dopaminergic interplexiform cell (DA-IPC) degeneration, associated with visual threshold elevation during dark adaptation. Methods: The ON bipolar cells were dissociated by papain and cultured in L15 media. The outward currents were recorded by whole-cell patch-clamp. Results: Both rectified and A-type outward currents were recorded in the ON bipolar cells when tested in a voltage range from -60 mV to +80 mV. The outward currents could be blocked by internal Cs+ and/or external TEA, suggesting that they are regulated mainly by K+ channels. In wild-type fish, exogenous dopamine (50 µM) decreased the K+ current by 10-30%. This effect of dopamine on K+ current was not found in nbb mutants. Furthermore, with a membrane potential holding at +80 mV the maximum K+ current recorded in nbb was only about 70% of the wild-type control level, similar to that recorded after dopamine application in wild-type animals. Conclusions: Exogenous dopamine produces no effect on the outward K+ current in nbb ON bipolar cells. This may be due to dopamine receptor desensitization caused by DA-IPC degeneration (see also Fan and Yazulla, 2001).
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