Compelling evidence has indicated the involvement of Na(+),K(+)-ATPase in the mechanisms of synaptic plasticity. In the present study, we investigated the effect of inhibitory avoidance training on Na(+),K(+)-ATPase activity, at different times after training, in the rat hippocampus. Male adult Wistar rats were trained in a step-down inhibitory avoidance task and compared to those submitted to isolated footshock (0.4 mA) or placed directly onto the platform. Na(+),K(+)-ATPase activity decreased, by 60%, in hippocampus of rats sacrificed immediately after the isolated footshock, as well as immediately (0 min) and 6 h after training; this effect was not present 24 h after training. We also verified that enzyme activity was not altered in rats killed after just being on the platform. These findings suggest that Na(+),K(+)-ATPase activity may be involved in the memory consolidation of step-down inhibitory avoidance in the hippocampus.