Figure 6. TRPA1 mediates the capsaicin-induced mechanical desensitization of splanchnic colonic afferents.
A. TRPA1+/+ splanchnic serosal afferent responding to capsaicin (3μM; 2mins). Note decreased mechanosensory response to 2000mg vfh after chemosensory response to capsaicin.
B. TRPA1−/− splanchnic serosal afferent responding to capsaicin (3μM; 2mins). Note mechanosensory response is unchanged after capsaicin.
C i) TRPA1+/+ serosal fibers responding to capsaicin subsequently displayed mechanical desensitization (*P<0.05; paired t-test). This effect was not observed in TRPA1−/− serosal afferents that responded to capsaicin (NS, P>0.05; paired t-test). ii) Mechanical desensitization after capsaicin application only occurred in TRPA1+/+ afferents that responded to capsaicin and was not observed in unresponsive fibers.
D. Magnitude of chemosensory response to capsaicin was similar in TRPA1+/+ and −/− fibers (NS, P>0.05, paired t-test).
E. The proportion of serosal afferents responding to capsaicin in either TRPA1+/+ or −/− mice was unchanged (NS, P>0.05, Fisher’s exact test).