Persistent sodium current is a nonsynaptic substrate for long-term associative memory

Curr Biol. 2008 Aug 26;18(16):1221-6. doi: 10.1016/j.cub.2008.07.030. Epub 2008 Aug 14.


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].

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Conditioning, Classical / physiology*
  • Lymnaea
  • Membrane Potentials*
  • Memory / physiology*
  • Neurons / metabolism*
  • Sodium / metabolism*


  • Sodium