Effects of the α₁- and α₂-adrenoreceptor antagonists prazosin (Praz) and atipamezole (Ati), respectively, on mechanical hypersensitivity assessed by the pinprick test (A) and on cold hypersensitivity assessed by the acetone test (B). Prazosin attenuates mechanical and cold hypersensitivity as shown by the significant decrease of withdrawal in response to pinprick and acetone stimulation, respectively. Atipamezole increased mechanical hypersensitivity as shown by the significant increase of withdrawal in response to pinprick stimulation. The drugs were administered 3 weeks after spared nerve injury induction, and their effects were tested before and 30 min after injection. Data are expressed as percentage of change from baseline (i.e., before drug injection) and are presented as mean ± 95% CIs (atipamezole and saline: n = 6/group; prazosin and DMSO: n = 5/group). ^$P < 0.05 versus DMSO; ^∞∞P < 0.01 versus saline. DMSO = dimethyl sulfoxide.