title: Persistent sodium current is a nonsynaptic substrate for long-term associative memory.
abstract: 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].
authors.affiliation: Department of Biology and Environmental Sciences, School of Life Sciences, University of Sussex, Brighton BN1 9QG, United Kingdom.
authors.forename: Eugeny S
authors.initials: ES
authors.lastname: Nikitin
authors.forename: Dimitris V
authors.initials: DV
authors.lastname: Vavoulis
authors.forename: Ildikó
authors.initials: I
authors.lastname: Kemenes
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Marra
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Pirger
authors.forename: Maximilian
authors.initials: M
authors.lastname: Michel
authors.forename: Jianfeng
authors.initials: J
authors.lastname: Feng
authors.forename: Michael
authors.initials: M
authors.lastname: O'Shea
authors.forename: Paul R
authors.initials: PR
authors.lastname: Benjamin
authors.forename: György
authors.initials: G
authors.lastname: Kemenes
mesh_terms: D000818:Animals; D003214:Conditioning, Classical / Q000502:physiology*; D008195:Lymnaea; D008564:Membrane Potentials; D008568:Memory / Q000502:physiology*; D009474:Neurons / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*
chemical_list: D012964:Sodium