Figure 6.
Effect of TTA-P2 on synaptically evoked LTCPs. A, Lack of effect of 1 μm TTA-P2 on evoked IPCSs (a; averages of 8 IPSCs) and EPSCs (b; averages of 7 EPSCs) recorded from two TC neurons. B, In a TC neuron maintained at −60 mV, rebound LTCPs were evoked by stimulations of the NRT at 20 s intervals in control condition and during successive applications of 20 and 50 nm TTA-P2. Ba, A concentration of 20 nm TTA-P2 had no effect on the high-frequency firing, whereas 50 nm TTA-P2 fully blocked the LTCP. However, as clearly seen on the superimposed traces in Bb, 20 nm TTA-P2 slowed the membrane repolarization and delayed the LTCP occurrence by 110 ms. C, In a TC neuron maintained at −70 mV, LTCPs were evoked by repetitive stimulations of the lemniscal pathway every 20 s under control conditions and while successively applying increasing concentrations of TTA-P2 (20, 50, and 100 nm and 1 μm). Note that a reduction in the LTCP-associated firing is observed with TTA-P2 concentrations ≥50 nm, which block >70% of the IT (see Fig. 1C). The full block of the LTCP evoked by the sensory EPSP required a TTA-P2 concentration that abolishes IT (i.e., 1 μm).