Effects of electrical coupling on the cone-horizontal cell circuit in the catfish retina.
Based on experimental data, a model of the cone-horizontal cell (L-HC) circuit has been developed for the luminosity channel of the catfish retina and impulse responses of cones and L-HC's were replicated for various experimental conditions. Negative feedback from L-HC to the cone pedicle and increases in the feedback gain, convert monophasic impulse responses to those that are biphasic, smaller and faster. Electrical coupling of cones and L-HC's lead to decremental spread of 2 radially outgoing waves with time courses of the coupled cones and L-HC's dependent on the spatial organization of the negative feedback circuit: however, the L-HC's impulse response on spreading outward shows an initial increase before decreasing. Interactions of the cone and L-HC waves were studied using Laplace transforms and the convolution theorem. The presence of a negative feedback circuit leads to deviations of the electrotonic decay from an exponential function. As a result of the dependency of the feedback gain on H0, electrical coupling introduces non-linearities in the cone-L-HC circuit that are dependent on the mean illuminance level.
D000818:Animals; D004553:Electric Conductivity; D005399:Fishes; D008433:Mathematics; D008954:Models, Biological; D010786:Photoreceptor Cells / Q000502:physiology*; D012160:Retina / Q000502:physiology*