Modeling Hermissenda: I. Differential contributions of IA and IC to type-B cell plasticity.
We developed a multicompartmental Hodgkin-Huxley model of the Hermissenda type-B photoreceptor and used it to address the relative contributions of reductions of two K+ currents, IA and IC, to changes in cellular excitability and synaptic strength that occur in these cells after associative learning. We found that reductions of [symbol: see text] C, the peak conductance of IC, substantially increased the firing frequency of the type-B cell during the plateau phase of a simulated light response, whereas reductions of [symbol: see text] A had only a modest contribution to the plateau frequency. This can be understood at least in part by the contributions of these currents to the light-induced (nonspiking) generator potential, the plateau of which was enhanced by [symbol: see text] C reductions, but not by [symbol: see text] A reductions. In contrast, however, reductions of [symbol: see text] A broadened the type-B cell action potential, increased Ca2+ influx, and increased the size of the postsynaptic potential produced in a type-A cell, whereas similar reductions of [symbol: see text] C had only negligible contributions to these measures. These results suggest that reductions of IA and IC play important but different roles in type-B cell plasticity.
Fost
J W
JW
Dept. Psychology, Princeton University, NJ 08544, USA. jwfost@princeton.edu
Clark
G A
GA
D000818:Animals; D008959:Models, Neurological; D016571:Neural Networks, Computer; D009473:Neuronal Plasticity / Q000502:physiology*; D017956:Photoreceptor Cells, Invertebrate / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology; D012908:Snails
D015221:Potassium Channels