IMPAIRED EXPRESSION OF LONG-TERM POTENTIATION IN HIPPOCAMPAL SLICES 4AND 48 H FOLLOWING MILD FLUID-PERCUSSION BRAIN INJURY IN-VIVO

The effect of fluid percussion brain injury on hippocampal long-term p otentiation (LTP) was investigated in hippocampal slices in vitro. Mil d to moderate (1.7-2.1 atm) lateral fluid percussion head injury or sh am operation was produced in rats 4 or 48 h prior to harvesting brain slices from the ipsilateral hippocampus. Field excitatory post-synapti c potentials (fEPSPs) were recorded in stratum radiatum of hippocampal subfield CAI in response to electrical stimulation of the Schaffer co llaterals. The initial slope of fEPSPs was used to investigate changes in synaptic strength prior to and following 100 or 200 Hz (1 s) tetan ic stimulation. TBI significantly inhibited expression of LTP in hippo campal 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 co gnitive disorders associated with TBI (traumatic brain injury). The da ta also indicate that TBI-induced effects on hippocampal LTP are robus t and may be investigated in the hippocampal slice preparation in vitr o. (C) 1998 Elsevier Science B.V.