Molecular-cellular mechanisms of the formation of long-term memory in the edible snail

This short review, based mainly on our own studies, summarizes data on the molecular-cellular mechanisms of non-associative and associative forms of learning (sensitization and classical conditioning) in the edible snail. A hypothesis is proposed which suggests that learning in defensive behavior command neurons in the edible snail is activated by a complex metabolic response specific for the type of conditioned habit. Excitation arriving at the neuron, in addition to activating second messenger systems, initiates the synthesis of short-lived (1-3 h) protein molecules which are specific (in the case of conditioning) or relatively specific (in the case of sensitization) for particular synaptic inputs. When training is inadequate, its effect can disappear from the point at which these proteins are degraded. When learning is better fixed, its effects last for several days (for sensitization) or significantly longer periods of time (for conditioning). Prolonged retention of habits should correspond to the situation of self-maintaining synthesis of long-lived protein molecules, which control the synthesis of synapse-specific short-lived regulator molecules.