LTP inhibition and reduced NMDA receptor-mediated synaptic transmission in TG rat hippocampal slices in vitro. (a) LTP was strongly impaired in hippocampal slices from 3.5-4 month-old TG rats. The magnitude of potentiation at 5 (STP) and 60 (LTP) min after application of a 100 Hz conditioning stimulation protocol (arrow) was significantly reduced in TG animals compared with their WT littermates. (b,c) Whereas baseline AMPA receptor-mediated synaptic currents were not affected, NMDA receptor-mediated synaptic currents were reduced. (b) The input/output relationship for AMPA receptor-mediated EPSCs was very similar in WT and TG rats. (c) In contrast, NMDA receptor-mediated EPSCs were significantly smaller in TG rats. Insets show representative EPSC traces. Calibration bars: Vertical, 100 pA; horizontal, 10 ms. Values are the mean ± S.E.M. % pre-HFS baseline EPSC amplitude. Summary statistics are shown in the right hand panels. *P < 0.05 compared with WT littermates.