| Abstract: | We have previously observed that in common snails trained to an associative skill consisting of refusing a defined foodstuff,
impairment of memory reconsolidation by the NMDA receptor antagonist MK-801 evokes amnesia in which the skill can be recovered
by retraining at the early stage (<10 days) while retraining at the late stage does not lead to formation of the skill. In
the experiments reported here, amnesia was induced with MK-801 and a reminder 24 h after training of snails to conditioned
taste aversion, and the antiamnestic effects of D-cycloserine, a partial agonist of the glycine site of the NMDA receptor,
were studied in the early (day 3) and late (day 12) stages. Three days after induction of amnesia, injections of D-cycloserine
and a reminder of the conditioned food stimulus led to recovery of the memory; administration of D-cycloserine without a subsequent
reminder was ineffective. Injection of D-cycloserine and a reminder 12 days after induction of amnesia had no effect on its
development and retraining did not lead to recovery of the memory. Thus, this study is the first to show that the NMDA receptor
agonist D-cycloserine influences memory recovery processes only at the early stage of development of amnesia induced by lesioning
of reconsolidation processes, while the late stage of amnesia was not sensitive to this agonist. |
