Heterosynaptic long-term depression is facilitated by blockade of inhibition in area CA1 of the hippocampus.

Non-associative long-term depression (LTD) of the stratum radiatum input to area CA1 was studied in rat hippocampal slices. Tetanization of either the alveus or stratum oriens produced greater than 30 min depression of the radiatum field EPSP and population spike, but generally only in the presence of picrotoxin. The spike depression was accounted for by the EPSP depression, and could be blocked by prior administration of an N-methyl-D-aspartate receptor antagonist. These data suggest that the induction of non-associative LTD is depolarization-dependent and involves the N-methyl-D-aspartate receptor/channel complex.