Molecular Biology of Learning: Modulation of Transmitter Release

TLDR

Learning has traditionally been inaccessible to cell biology, but recent studies in higher invertebrates now enable experimental analysis of the behavioral, neurophysiological, morphological, biochemical, and genetic components of plastic changes underlying learning. The review focuses on short‑term sensitization of the gill and siphon reflex in *Aplysia californica*. The authors examine how cyclic‑AMP‑dependent protein phosphorylation modulates synaptic action during this short‑term sensitization. These analyses show that cAMP‑dependent protein phosphorylation modulates synaptic action and suggest that the same mechanisms underlie long‑term memory and classical conditioning.

Abstract

Until recently, it has been impossible to approach learning with the techniques of cell biology. During the past several years, elementary forms of learning have been analyzed in higher invertebrates. Their nervous systems allow the experimental study of behavioral, neurophysiological, morphological, biochemical, and genetic components of the functional (plastic) changes underlying learning. In this review, we focus primarily on short-term sensitization of the gill and siphon reflex in the marine mollusk, Aplysia californica . Analyses of this form of learning provide direct evidence that protein phosphorylation dependent on cyclic adenosine monophosphate can modulate synaptic action. These studies also suggest how the molecular mechanisms for this short-term form of synaptic plasticity can be extended to explain both long-term memory and classical conditioning.