The antinociceptive effects of mPAP can be transiently inhibited with a selective A₁R antagonist.

<p>Wild-type mice were tested for (A) noxious thermal and (B) mechanical sensitivity before (baseline, BL) and following injection of CFA (CFA-arrow) into one hindpaw. The non-inflamed hindpaw served as control. All mice were injected with active mPAP (mPAP-arrow; 2 U, i.t.). Two days later, half the mice were injected with vehicle (CPX/V-arrow, circles; intraperitoneal (i.p.); 1 hr before behavioral measurements) while the other half were injected with 8-cyclopentyl-1, 3-dipropylxanthine (CPX/V-arrow, squares; 1 mg/kg i.p.; 1 hr before behavioral measurements). There were significant differences over time between mice injected with vehicle and mice injected with CPX (Repeated measure two-way ANOVA; <i>P</i><0.01). Post-hoc paired t-tests were used to compare responses at each time point between vehicle (n = 10) and CPX-injected mice (n = 10); same paw comparisons. *** <i>P</i><0.0005. All data are presented as means±s.e.m.