Taurine blocks spontaneous cone contraction but not horizontal cell dark suppression in isolated goldfish retina

The objective of this study was to investigate the effects of taurine on co ne retinomotor movements and the responses of cone-driven horizontal cells in dark-adapted teleost retina. In isolated goldfish retina preparations ma intained in the dark, cones spontaneously contracted, and the responses of horizontal cells were suppressed. Addition of 5 mM taurine to the physiolog ical solution blocked the spontaneous contraction of cones in the dark but did not block the dark-suppression of horizontal cell responses. These resu lts indicate that the mechanism that leads to horizontal cell dark suppress ion is not sensitive to taurine. Although both cone retinomotor position an d horizontal cell responsiveness are known to be modulated by dopamine, the present results do not support the hypothesis that taurine inhibits dopami ne release in the dark because only spontaneous cone contraction was affect ed by taurine. These results also indicate that spontaneous cone contractio n in the dark is not the cause of horizontal cell dark suppression because, in the presence of taurine, canes were elongated yet horizontal cell respo nses were still suppressed. Consequently, these results make it clear that horizontal cell dark suppression is not an artifact produced by incubating isolated teleost retina preparations in taurine-free physiological solution .