Stress-induced alterations in hippocampal plasticity, place cells, and spatial memory.

Acute, inescapable, and unpredictable stress can profoundly modify brain and cognition in humans and animals. The present study investigated the ensuing effects of 2-h variable "audiogenic" stress on three related levels of hippocampal functions in rats: long-term potentiation, place cell activity, and spatial memory. In agreement with prior findings, we observed that stress reduced the magnitude of Schaffer collateral/commissural-Cornu Ammonis field 1 long-term potentiation in vitro, and selectively impaired spatial memory on a hidden platform version of the Morris water maze task. We also observed that stress impaired the stability of firing rates (but not firing locations) of place cells recorded from dorsal Cornu Ammonis field 1 in rats foraging freely on a novel open-field platform located in a familiar surrounding room. These findings suggest that stress-induced modifications in synaptic plasticity may prevent the storage of stable "rate maps" by hippocampal place cells, which in turn may contribute to spatial memory impairments associated with stress.