The antinociceptive effects of PPDA in rats with compression of the trigeminal nerve root. The effects of PPDA, a selective NR2C/NR2D antagonist, on mechanical allodynia (A, B) and hyperalgesia (C, D) in rats with compression of the trigeminal nerve root (n = 8 in each treatment group). The intracisternal administration of vehicle did not affect air-puff thresholds in either the ipsilateral (A) or contralateral (B) side. However, injections of 5 or 10 μg of PPDA produced significant anti-allodynic effects in a dose-dependent manner in both sides (A, B). The anti-allodynic effects of PPDA were maintained for two hours after injection of 5 μg of PPDA and three hours after administration of the 10 μg dose. The intracisternal administration of 5 or 10 μg of PPDA also produced significant anti-hyperalgesic effects on the ipsilateral (C) and contralateral (D) side. The anti-hyperalgesic effects of PPPA were completely recovered by six hours after injection with 10 μg of PPPA. Vehicle injections did not affect pin-prick scores in the subject rats. *P < 0.05, vehicle-vs. PPDA-treated groups.