Figure 1.
Assessment of acute nociception in Nf1+/− mice and WT littermates.
In the absence of injury, Nf1+/− mice did not exhibit robust differences in sensitivity to noxious heat or tactile stimuli applied to the plantar surface of the hindpaw. (A) Paw withdrawal latency to low or high heating rates did not differ among genotypes or genders. Response latencies for both hindpaws were averaged to yield a single value for each mouse. Data are mean ± SEM of 6–8 mice. (B) Mechanical sensitivity was slightly greater in female Nf1+/− mice than wild type (WT) littermates (N = 18 in each group). (C) Male Nf1+/− and WT mice did not differ in their mechanical sensitivity (n = 16 and 15, respectively). Panels B and C were constructed using baseline data for the ipsilateral hindpaw of mice in the capsaicin and CGRP treatment groups. Data are expressed as the mean ± SEM.
Figure 2.
Intraplantar injection of 0.01% capsaicin or 5 µg CGRP induced heat hyperalgesia.
(A, B) The magnitude of heat hyperalgesia determined 15 min after injection of capsaicin did not differ between genotypes in either females or males. * P<0.05 compared to baseline. (C, D) Paw withdrawal latency was decreased within 5 min of injection (arrow) of CGRP, but not PBS in females and males of both genotypes. Heat hyperalgesia in female and male Nf1+/− mice was greater than their WT littermates. The data for PBS are the pooled responses of two female and two male mice of each genotype. * P<0.05 compared to WT at the same time point. Data in all panels are expressed as the mean ± SEM of determinations in 6–8 mice of each gender and genotype.
Figure 3.
Mechanical hypersensitivity induced by intraplantar injection of 0.001% capsaicin (CAP) or 5 µg CGRP.
(A, B) Force-response curves for the ipsilateral hindpaw after injection of CAP or vehicle (VEH) in Nf1+/− (circles) or WT (squares) mice. Data are the mean ± SEM of responses by 5–7 mice of each gender and genotype. (C, D) Force-response curves for the ipsilateral hindpaw after injection of CGRP or PBS in Nf1+/− (circles) or WT (squares) mice. Data in panels C-D are the mean ± SEM of responses by 4–8 mice of each gender and genotype, with the exception of CGRP in Nf1+/− mice where 11 mice were tested.
Table 1.
Capsaicin evokes mechanical hypersensitivity in both wildtype and Nf1+/− mice.
Table 2.
Calcitonin gene-related peptide evokes mechanical hypersensitivity in both wildtype and Nf1+/− mice.
Figure 4.
Duration of licking of the ipsilateral hindpaw after intraplantar injection of inflammatory irritants.
Panels A and B illustrate the time course of licking after intraplantar injection of 0.01% capsaicin in the hindpaw of female or male mice, respectively. Panels C and D illustrate the time course of licking after intraplantar injection of 2% formalin in female or male mice, respectively. Panels E and F present the total duration of licking in phases 1 (0–5), 2 (15–55 min) and 3 (55–90 min) of the formalin test in female and male mice, respectively. Data are the mean ± S.E.M. of determinations in 6–8 mice of each gender and genotype. * P<0.05, ** P<0.01 compared to corresponding WT littermates.
Figure 5.
Intraplantar injection of formalin induced spontaneous pain behaviors in both genders and genotypes.
Time course of guarding, flinching or unweighting of the hindpaw after intraplantar injection of formalin in (A) female or (B) male mice. The percentage of female Nf1+/− mice that exhibited these behaviors was higher than WT littermates, but did not differ in male mice of either genotype. Percentage of (C) female or (D) male mice exhibiting guarding, flinching or unweighting of the hindpaw averaged for the first phase (0–5 min), second phase (15–55 min) and third phase (55–90 min) of the formalin test. Six to eight mice of each gender and genotype were tested. * P<0.05, ** P<0.01 compared to corresponding WT littermate.
Figure 6.
Levels of CGRP mRNA and RAMP1 mRNA.
(A) Levels of CGRP mRNA in the dorsal root ganglion (DRG) of Nf1+/− and WT mice did not differ by genotype or gender. (B) Levels of RAMP1 mRNA in the spinal cord of Nf1+/− and WT mice did not differ by gender or genotype. Data are expressed as mean ± SEM copies normalized to 100,000 GAPDH for the DRG and to 100,000 β-actin for spinal cord. Numbers in the columns are the number of mice. * P<0.05 compared to corresponding WT littermates. Nf1+/− mice (open bars); WT mice (solid bars)