Fig. 6.

Thermal nociception following antagonism of TRPV1 and IB₄-positive neurons. A: effects of a selective TRPV1 antagonist on thermal pain sensation. Compared with preinjection levels (Pre), head withdrawal latencies to heat stimulation were significantly prolonged in both C57BL/6 and BALB/c (6 animals in each) after systemic injection of the selective TRPV1 antagonist JNJ-17203212 (JNJ). *P < 0.05 and **P < 0.01, respectively, between Pre and JNJ (Mann-Whitney U-test). B: effects of a selective reduction of IB₄-neurons on thermal pain sensation in C57BL/6 and BALB/c (5 animals per each drug group in each strain). Compared with unconjugated saporin-treated mice (Sap), IB₄-saporin-treated (IB₄-sap) C57BL/6 showed significantly longer head withdrawal latency to heat stimulation. **P < 0.01, between Sap and IB₄-sap (Mann-Whitney U test). C: relative fluorescent intensities of the trigeminal second branch area (V2) and the first branch area (V1) in IB₄-stained TG sections in unconjugated saporin-treated mice (5 animals in each strain) were 98 ± 16 and 101 ± 20% in C57BL/6 and BALB/c, respectively. However, relative fluorescent intensities in IB₄-saporin-treated mice (5 animals in each strain) were low (29 ± 8 and 37 ± 7%, P < 0.01 and 0.05, respectively, Mann-Whitney U-test). Scale bar = 1 mm.