Electrophysiological characterization of the spectral sensitivities of horizontal cells in cyprinid fish retina.

The spectral characteristics of horizontal cells of roach retina have been studied by a multi-disciplinary approach. Intracellular recording was combined with localized irradiation of the retina with spectrally selective laser beams to facilitate quantitative analyses. L1HC's were driven mainly by red (R)--sensitive cones. CbHC's were depolarized by R- and hyperpolarized by green (G)--and blue (B)--sensitive cones. The hyperpolarizing responses of L2HC's were also driven by B-, and G-sensitive cones, and, in addition, some depolarized to a 675 nm test stimulus. L2 units were relatively more abundant in dark-adapted retinae; during light adaptation, they became progressively less abundant. It is suggested that the spectral characteristics of some HC's are influenced by the adaptational state of the retina.