Impaired expression of long-term potentiation in hippocampal slices 4 and 48 h following mild fluid-percussion brain injury in vivo.

The effect of fluid percussion brain injury on hippocampal long-term potentiation (LTP) was investigated in hippocampal slices in vitro. Mild to moderate (1.7-2.1 atm) lateral fluid percussion head injury or sham operation was produced in rats 4 or 48 h prior to harvesting brain slices from the ipsilateral hippocampus. Field excitatory post-synaptic potentials (fEPSPs) were recorded in stratum radiatum of hippocampal subfield CA1 in response to electrical stimulation of the Schaffer collaterals. The initial slope of fEPSPs was used to investigate changes in synaptic strength prior to and following 100 or 200 Hz (1 s) tetanic stimulation. TBI significantly inhibited expression of LTP in hippocampal slices in vitro. Post-tetanus fEPSP slopes increased more than 100% in hippocampal slices from sham-operated animals but less than 50% in slices from rats following TBI. The data suggest that changes in functional synaptic plasticity in the hippocampus may contribute to cognitive disorders associated with TBI (traumatic brain injury). The data also indicate that TBI-induced effects on hippocampal LTP are robust and may be investigated in the hippocampal slice preparation in vitro.