Persistent sodium current is a nonsynaptic substrate for long-term associative memory.
Although synaptic plasticity is widely regarded as the primary mechanism of memory [1], forms of nonsynaptic plasticity, such as increased somal or dendritic excitability or membrane potential depolarization, also have been implicated in learning in both vertebrate and invertebrate experimental systems [2-7]. Compared to synaptic plasticity, however, there is much less information available on the mechanisms of specific types of nonsynaptic plasticity involved in well-defined examples of behavioral memory. Recently, we have shown that learning-induced somal depolarization of an identified modulatory cell type (the cerebral giant cells, CGCs) of the snail Lymnaea stagnalis encodes information that enables the expression of long-term associative memory [8]. The Lymnaea CGCs therefore provide a highly suitable experimental system for investigating the ionic mechanisms of nonsynaptic plasticity that can be linked to behavioral learning. Based on a combined behavioral, electrophysiological, immunohistochemical, and computer simulation approach, here we show that an increase of a persistent sodium current of this neuron underlies its delayed and persistent depolarization after behavioral single-trial classical conditioning. Our findings provide new insights into how learning-induced membrane level changes are translated into a form of long-lasting neuronal plasticity already known to contribute to maintained adaptive modifications at the network and behavioral level [8].
Nikitin
Eugeny S
ES
Department of Biology and Environmental Sciences, School of Life Sciences, University of Sussex, Brighton BN1 9QG, United Kingdom.
Vavoulis
Dimitris V
DV
Kemenes
Ildikó
I
Marra
Vincenzo
V
Pirger
Zsolt
Z
Michel
Maximilian
M
Feng
Jianfeng
J
O'Shea
Michael
M
Benjamin
Paul R
PR
Kemenes
György
G
D000818:Animals; D003214:Conditioning, Classical / Q000502:physiology*; D008195:Lymnaea; D008564:Membrane Potentials; D008568:Memory / Q000502:physiology*; D009474:Neurons / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*
D012964:Sodium