SPECIAL I SSUE Knocking-down the NMDAR1 subunit in a limited amount of neurons in the rat hippocampus impairs learning

Amplicon vectors derived from herpes simplex virus type 1 were built to modify NMDA receptors by expressing antisense RNA for the essential NR1 subunit. Their ability to modify endogenous levels of NR1 was tested in cultures of rat embryo neocortical neurons. We studied behaviour and tested for expression in adult rats injected with those vectors into the dorsal hippocampus to find out which cells and how many appear involved in memory formation. Rats injected with vectors expressing NR1 antisense performed significantly worse than control rats in an inhibitory avoidance task. Immunohistochemistry was performed in brain slices from the same animals. The transduced cells represented 6‐7% of