Characterization of the light-induced currents in Hermissenda

Classical conditioning of the seaslug, Hermissenda crassicornis, with light and turbulence produces changes in the membrane properties of type B photo receptors. The light response consists of a generator potential, which pers ists for the duration of the light flash, followed by a smaller, long lasti ng depolarization (LLD). Voltage clamp data suggests that two currents gene rate the light response: a transient sodium current, previously modeled as an IP3-gated sodium current, and a smaller, prolonged current that is sensi tive to calcium. A model of the calcium-sensitive light-induced current is developed and included in a model with previously characterized light-induc ed and voltage-dependent currents. Voltage clamp simulations using this fiv e channel model show that the calcium sensitive component consists of both a sodium current and a potassium current, and that both of them are require d for the LLD. (C) 2000 Elsevier Science B.V. All rights reserved.