Cold exposure induces vaso-occlusion and mechanical hyperalgesia in HbSS mice. (A) Townes HbSS and HbAA mice (n = 4 per group) were implanted with DSFC windows. At baseline, flowing subcutaneous venules (20-23 venules per mouse) were selected and mapped. HbSS and HbAA mice were exposed to cold at 10°C (50°F) for 1 hour and then returned to RT. A control group of HbSS mice remained at RT without cold exposure. Microvascular stasis (vaso-occlusion) was measured at the indicated times after cold exposure. Values are means ± standard error of the mean (SEM). ∗P < .05, ∗∗P < .01, and ∗∗∗P < .001, HbSS + cold vs HbAA + cold and HbSS at RT and ⁺P < .05 HbAA + cold vs HbSS at RT (2-way analysis of variance [ANOVA] with the Tukey multiple comparison test). (B) Mechanical PWT was measured in the hind paws of HbAA and HbSS mice using von Frey filaments at baseline at RT. Nonhyperalgesic (PWT > 0.7 g) HbAA (n = 11) and HbSS (n = 14 mice) mice were selected for cold exposure. After baseline measurements, nonhyperalgesic mice were exposed to cold (10°C/50°F) for 1 hour and returned to RT. PWT was measured at the indicated times after cold exposure. Values are means ± SEM. ∗P < .05 HbSS vs HbAA (2-way ANOVA with the Sidak multiple comparison test). ^#P < .05, ^##P < .01, and ^####P < .0001, baseline vs after cold (2-way ANOVA with the Dunnett multiple comparison test).