Ionic current model of the vertebrate rod photoreceptor

AbstractWe describe voltage- and calcium-dependent ionic currents in the photoreceptor inner segments similar to the Hodgkin and Huxley (Journal of Physiology, 117, 500–544, 1952) equations. The model is used to describe both rods and cones by adjusting parameters. To simulate the light response, the inner segment model was connected with the phototransduction model proposed by Torreet al. (Cola Spring Harbor Symposia on Quantitative Biology, 55, 563–573, 1990). The role of individual ionic currents in the inner segment in shaping the light response was analyzed through computer simulations. The results suggest that: (1) the transient hyperpolarization to a bright flash is generated by Ih; (2) the oscillation after prolonged hyperpolarization in rods results from the interaction amongICa,IK(Ca), andICl(Ca). Since the present model describes the biophysical processes from phototransduction to voltage response, the model can be used for analyzing the light response properties of the photoreceptors quantitatively