Intracisternal (ICM) injection of RTX blocked heat pain in the face for wild-type, but not TRPV1 knock-out mice. Animals treated 1-week previously with either RTX (100 ng, 1 μl) or vehicle (0.25% Tween 80 in PBS) were tested using the capsaicin eye-wipe assay and using the operant orofacial device at 48 and 55°C. TRPV1 k.o. mice and RTX-treated C57BL/6J mice were completely insensitive to capsaicin (0.1%, 20 μl, corneal application), while vehicle-treated C57BL/6J had a response similar to non-treated animals (A). TRPV1 k.o. mice treated with RTX responded similarly to vehicle treated k.o. mice at both 48 and 55°C (B). C57BL/6J mice treated with RTX were not sensitive to the 48°C stimuli (B) and behaved like the TRPV1 k.o. mice. Interestingly, the RTX-treated C57BL/6J mice demonstrated a significant increase in response at 55°C, with licking events increased even above the TRPV1 k.o. mice. * = significantly lower (P < 0.05), compared to baseline; ** = significantly lower compared to RTX-treated animals.
Neubert et al. Molecular Pain 2008 4:43 doi:10.1186/1744-8069-4-43