Primary Changes of Membrane Currents During Retention of Associative Learning

Abstract

A single identified neuron was repeatedly isolated by axotomy from the central nervous system of the nudibranch mollusk Hermissenda crassicornis. An early voltage-dependent outward K+ current of this neuron was reduced and more rapidly inactivated for animals previously trained with paired but not randomized light and rotation. Since this current change can affect interneuron and motorneuron output via known synaptic pathways, it helps explain a long-lasting behavioral change that shows the defining features of vertebrate associative learning.

Brain Insulin Receptors and Spatial Memory

“…This subpopulation specificity of learning-induced changes of IR are consistent with numerous previously published biophysical and biochemical studies. Voltage-dependent K ϩ currents, for example, were found in single identified neurons of the mollusk Hermissenda after Pavlovian conditioning (39). Related changes of K ϩ currents were found in a subpopulation of CA1 pyramidal cells (40), and a subpopulation of H6 cerebellar cortical Purkinje neurons (41) after Pavlovian conditioning of the rabbit eyelid response.…”

Presynaptic plasticity: The regulation of Ca2+-dependent transmitter release

“…This difficulty can be circumvented by using certain experimental preparations that can serve as models for memory traces. Among these preparations the following are more commonly used, namely associative learning in gastropod molluscs: Aplysia as used by Hawkins et al (1983) and Hermissenda as used by Alkon et al (1982) and long-term potentiation (LTP) in the hippocampus (Bliss and Lorno, 1973).…”

“…One of the mechanisms that was advanced in this respect is the modulation of the action potential duration due to a cAMP mediated decrease in a potassium current induced by the facilitatory transmitter serotonin in Aplysia, that leads to a prolonged increase in transmitter release and thus to synaptic facilitation (Hawkins et al, 1983). In Hermissenda associative learning appears to be mediated by a change in the excitability of certain neurons due to a change in the degree of phosphorylation of several potassium channels (Alkon et al, 1982). A common mechanism is that most of the plastic changes in synaptic efficiency encountered in 540 M. VERItAGE et al these experimental models, involve changes in the amount of transmitter released.…”

Reversible antisense inhibition of Shaker-like Kv1.1 potassium channel expression impairs associative memory in mouse and rat

“…Drosophila memory mutants (primarily the Shaker mutants) (1), Hermissenda associative conditioning (2) and rabbit nictitating membrane conditioning (correlated with enhanced post-synaptic responses due to persistent reduction of voltagedependent K ϩ current in hippocampal cells) (3) have all strongly suggested a role for specific potassium channels in learning and memory. In recent years, studies of Shaker-like genes in the mammalian brain revealed a family of potassium channel related proteins that differ in both their electrophysiological properties and in their neuroanatomical distribution (4,5).…”