Neurochemical mechanisms of consolidation of associative aversive training to food in the common snail.

The effects of the protein synthesis inhibitor cycloheximide and serotonin and NMDA glutamate receptor antagonists on the processes of consolidation of an associative skill consisting of refusing a particular foodstuff were studied in the common snail. When animals were trained on the background of cycloheximide, the skill was not acquired. Repeat training of "amnestic" snails to refuse the same food without the inhibitor also failed to produce the skill. Training of snails on the background of the nonselective serotonin receptor antagonist methiothepin or the NMDA glutamate receptor antagonist MK-801 (dizocilpine maleate) did not lead to acquisition of the conditioned reflex to food. However, on repeat training, the skill was formed more quickly. The studies included the first observation that using a single type of training, treatments addressing different molecular mechanisms evoke reversible or irreversible impairments to the mechanisms of consolidation of long-term memory. It is suggested that the reversible effect is associated with suppression of the processes of reproduction, while the irreversible effect is linked with impairment to engram storage.