Fig. 5. Systemic administration of prazosin attenuates windup levels without changing A-fiber and C-fiber–mediated responses of wide dynamic range (WDR) neurons to graded electrical stimulation in α-2A knockout (KO) mice. (A and B ) In α-2A KO mice, systemic administration of the α-1 receptor antagonist prazosin (0.1 μg/kg−1intraperitoneal) did not significantly change the (A ) A-fiber and (B ) C-fiber–mediated responses (number of action potentials, AP) of WDR neurons (n = 18) to graded electrical stimulation. (C –E ) Prazosin suppressed windup levels across (C ) 0.2 Hz, (D ) 0.5 Hz, and (E ) 1.0 Hz stimulation in α-2A KO mice. (F ) The averaged C-component responses for the stimulus 7–16 of the trial were also significantly reduced during 0.2, 0.5, and 1.0 Hz stimulation after prazosin treatment, compared with the preprazosin condition. Data are normalized by the response evoked by the first stimulation of each trial. # =P < 0.05; ## =P < 0.01; ### =P < 0.001 versus preprazosin condition. Data are expressed as mean ± SEM.