Insulin treatment alleviates heat and mechanical hypersensitivity in ob/ob mice. Beginning at 8 weeks of age, ob/ob and wild-type mice were treated with intraperitoneal insulin or saline twice daily. A: Insulin-treated ob/ob mice (■) had reduced blood glucose values by 10 weeks of age compared with saline-treated ob/ob mice (†P < 0.001) and to original 8-week levels (*P < 0.01). Glucose levels in ob/ob saline-treated mice (●) were greater than wild-type saline-treated mice (♦) throughout the testing period, while ob/ob insulin-treated mice were only different than wild-type saline-treated mice during select weeks (#P < 0.05). B: Hypersensitivity in ob/ob insulin-treated mice progressively improved compared with 8-week values (*P < 0.001) and with ob/ob saline-treated mice (†P < 0.001); however, PWLs remained significantly less than wild-type saline-treated mice (#P < 0.05). C: At 12 weeks of age, mechanical thresholds in ob/ob insulin-treated mice were significantly greater than 8-week values (*P < 0.01) and ob/ob saline-treated mice (*P < 0.05). ob/ob saline-treated mice remained hypersensitive as compared with wild-type saline-treated mice (#P < 0.05) (n = 5 ob/ob mice per group; n = 6 wild-type mice). WT, wild type.