Figure 8.

PAR1 activation induces an inward current and a depolarization in hippocampal CA1 pyramidal cells A, representative current trace showing 30 nm thrombin-induced inward current in a CA1 pyramidal cell in a hippocampal slice. The inward current was abolished by switching to thrombin plus 100 μm APV. Recording was performed at −60 mV in the presence of 0.5 μm TTX and 5 μm Mg²⁺. B, summary of amplitude changes of inward current induced by thrombin and TFLLR with and without coapplication of APV: thrombin 8.8 ± 3.1 pA, thrombin + APV 2.4 ± 1.3 pA; TFLLR 15.9 ± 3.1 pA, TFLLR + APV 2.3 ± 1.9 pA. *P < 0.05, 1-factor repeated measures ANOVA with Dunnett's test. C, application of thrombin (30 nm) induces an increase in membrane current variance in the presence of TTX and the presence of low external Mg²⁺, which is blocked by 100 μm APV. mEPSCs were digitally removed as described in the Methods. D, summary of membrane current variance measurements from CA1 pyramidal cells held under voltage clamp (−60 mV) by thrombin (control 7.7 ± 1.0 pA²; thrombin 12.4 ± 1.1 pA²; thrombin + APV 6.8 ± 2.3 pA²) and the PAR1 agonist peptide TFLLR (30 μm; control 6.1 ± 0.7 pA²; TFLLR 10.4 ± 1.4 pA²; TFLLR + APV 4.2 ± 0.6 pA²); *P < 0.05; 1-factor repeated measures ANOVA with Dunnett's test. E, current clamp recording from a CA1 pyramidal cell (left panel) showing depolarization and spike firing during application of 30 nm thrombin (1.5 mm Mg²⁺). Inset shows spike firing during depolarizing current injection. Right panel is the summary of current clamp recordings from 22 neurones showing a significant depolarization of the membrane potential (P < 0.01; paired t test). F, APV (100 μm) significantly reduces thrombin-mediated depolarization of the membrane potential at 23°C (thrombin 5.8 ± 1.7 mV; thrombin + APV 2.5 ± 1.0 mV, n = 6) and at 34°C (thrombin 4.3 ± 1.0 mV; thrombin + APV 1.2 ± 0.6 mV, n = 12), *P < 0.05, 1-factor repeated measures ANOVA with Dunnett's test.