Fig. 4

TNF-α increased acid-evoked action potentials in rat DRG neurons. a, c In the same DRG neuron, a pH 6.0 acidic stimulus induced not only a rapid inward current with voltage-clamp recording, but also action potential burst under current-clamp condition. Original action potentials (APs) were recorded before and after application of TNF-α (10 ng/ml, 5 min) alone (A) or co-application of both TNF-α (10 ng/ml, 5 min) and SB202190 (10 μM, 3+5=8 min) (C). AMG9810 (5 μM) was used to block proton-induced TRPV1 activation. B and D. The graphs showed the number of acid-evoked APs increased by pre-application of TNF-α alone, but not by co-application of both TNF-α and SB202190. **P < 0.01, paired t-test, n = 6 cells