Intraventricular Infusions of Anti‐Neural Cell Adhesion Molecules in a Discrete Posttraining Period Impair Consolidation of a Passive Avoidance Response in the Rat

: Intraventricular infusions of anti‐neural cell adhesion molecule (anti‐NCAM) are demonstrated to inhibit consolidation of a passive avoidance response when administered in the 6‐8‐h posttraining period. Anti‐NCAM was ineffective when administered during training or at any other time up to 10 h thereafter, and no amnesic effects were observed with absorbed anti‐NCAM or anti‐neurofilament protein. Amnesia was observed only at the 48‐h recall time, and this could not be attributed to poor antibody penetration or a prolonged residence time, as studies with 125I‐labelled anti‐NCAM in trained animals demonstrated a rapid accumulation into all brain regions, and this was marked in the olfactory bulb and hippocampus, areas showing an inherent and paradigm‐specific increase in NCAM sialylation state, respectively. The lack of an amnesic action at the 24‐h recall time is attributed to anti‐NCAM‐impaired synapse structuring becoming apparent following the paradigm‐specific increases in NCAM sialylation state.