Figure 2.

Pigmented and unpigmented mice display differences in cutaneous sensitivities. All bars show mean ± s.e.m. The colour of each plot represents the body colour of the inbred mouse strain. (a) Heat and mechanical sensitivities in the tail and paw of pigmented and unpigmented male mice (6 and 5 strains, respectively). Increased pain sensitivity to stimuli is depicted by positive z-scores. (b) There is no correlation between mechanical sensitivities as measured by tail-clip and von Frey tests (r = −0.38, P < 0.25). (c) The sensitivities across 5 different pain modalities (thermal, chemical, afferent-dependent, thermal hypersensitivity and mechanical hypersensitivity) in pigmented and unpigmented mouse groups (6 and 5 strains, respectively) are displayed. The latter three modalities are pathological pain sensitivities in neuropathic and/or inflammatory models. *P < 0.05 and **P < 0.01, in t-test. (d) Capsaicin and formalin sensitivities between pigment and unpigmented mouse groups (6 and 5 strains, respectively). **P < 0.01, in t-test. (e) There is a positive correlation between capsaicin-induced pain and heat sensitivity. Pearson r = 0.81, P < 0.01. Pigmented mouse strains show higher thermal and capsaicin sensitivities. (f) Withdrawal latency to radiant heat stimulation and threshold to von Frey filaments in the whisker pad (face) and paw of B6 (n = 5 and 10, respectively) and albino-B6 (n = 65 and 30, respectively) female mice. *P < 0.05 and **P < 0.01, in t-test.