Three time windows for amnestic effect of antibodies to cell adhesion molecule L1 in chicks.

The L1/NgCAM cell adhesion molecule is involved in neurite outgrowth, axonal fasciculation and cell migration in the nervous system. We studied the effects of antibodies against L1 injected intracranially at various times before and after training 2-day-old chicks in a visual categorization task. Memory retention was tested 24 h post-training. Anti-L1 antibodies impaired task retention only when administered in three restricted time windows: immediately before training, at about 5.5 h after training and from 15 to 18 h after training. No amnesia was produced by injections before, between or after these sensitive periods (from -1 to +21 h relative to training). These results indicate that there are multiple post-training periods during which L1 is involved in the formation of long-term memory.