TY - JOUR T1 - The Effect of Intensity and Duration on the Light-Induced Sodium and Potassium Currents in the <em>Hermissenda</em> Type B Photoreceptor JF - The Journal of Neuroscience JO - J. Neurosci. SP - 4217 LP - 4228 DO - 10.1523/JNEUROSCI.22-10-04217.2002 VL - 22 IS - 10 AU - Kim T. Blackwell Y1 - 2002/05/15 UR - http://www.jneurosci.org/content/22/10/4217.abstract N2 - Light duration and intensity influence classical conditioning inHermissenda through their effects on the light-induced currents. Furthermore, the contribution of voltage-dependent potassium currents to the long-lasting depolarization in type B photoreceptors depends on light-induced currents active at resting potentials. Thus, the present study measures the effect of holding potential, duration, and intensity on the light-induced currents in discontinuous single-electrode voltage clamp mode. Three distinct current components are distinguished by their temporal and voltage characteristics and sensitivity to pharmacological agents. One current component is a transient sodium current, INalgt; another is a plateau sodium current,Iplateau, which persists for the duration of the light stimulus. Substitution of trimethylammonium chloride for sodium reduces both currents equally, suggesting thatIplateau represents partial inactivation ofINalgt. The third current component is a prolonged reduction in potassium currents,IKlgt; it is accompanied by an increase in input resistance, and it appears at potentials close to rest. An increase in light duration or intensity causes an increase in the peak conductance of both INalgt andIKlgt. Latency ofINalgt is decreased by intensity, whereas rise time is increased by duration. An increase in light duration or intensity causes an increase in the time-to-peak and duration ofIKlgt. Characteristics of these currents suggest that IKlgt is responsible for the long-lasting depolarization seen after light termination, and thus plays a role in classical conditioning. ER -