Figure 9. The responses of mesenteric afferent nerves to capsaicin in WT and TRPV1^−/− mice.

A, upon administration of 1 μm capsaicin in WT mice, there was an excitation on mesenteric afferents. B, following 10 μm capsaicin, there was a brief phase of intense discharge followed by a decrease in spontaneous nerve firing and reduced responsiveness to BK, intraluminal acid (not shown) and distension, which is indicative of afferent nerve desensitization. C, cumulative data showing changes in afferent activity following application of capsaicin in WT preparations. Note that TRPV1 KO preparations failed to respond to capsaicin.