The capsaicin-induced reduction of LTP recorded in horizontal slices is blocked by TRPV1 antagonists and is absent in TRPV1 deficient mice.

<p>(A) Input-output curves as evoked by single stimuli applied at EC fibers. Drug-free control recordings (n = 15) did not differ from recordings made in capsaicin-treated slices (1 µM cap: n = 15; 10 µM cap: n = 8). (B) EC stimulation caused a stable LA-LTP in horizontal slices derived from adult male mice. Bath-applied capsaicin (cap) induced a dose-dependent reduction in the magnitude of LA-LTP. Data points represent averaged amplitudes (mean ± SEM) normalized with respect to baseline values. Representative traces were recorded 5 min prior to tetanus (dashed lines) and 60 min after tetanus (solid lines). (C) Capsazepine completely blocks the capsaicin-induced reduction of LTP only at a concentration of 50 µM. (D) The capsaicin-induced reduction of LA-LTP could be also blocked by the specific TRPV1 antagonist AMG9810. (E) Bar histogram of data points averaged 57 to 60 min after HFS and normalized with respect to baseline (mean ± SEM). Significant differences are indicated. *<i>p</i><0.05. (F) In TRPV1^−/− mice the inhibitory effect of 1 µM capsaicin was absent. HFS: high-frequency stimulation.