Fig. 1. Effects of orally, intrathecally, and intracerebroventricularly administered gabapentin after spinal nerve ligation (SNL) in rats. The mechanical withdrawal threshold is presented over time. Oral (10–300 mg/kg, n = 6;  A ), intrathecal (10–100 μg/rat, n = 6;  B ), and intracerebroventricular (3–100 μg/rat, n = 6–8;  C ) gabapentin produced a dose-dependent increase in withdrawal threshold compared with vehicle. *  P < 0.05  versus time 0 by one-way analysis of variance. Groups differ by two-way analysis of variance, with (300 mg/kg, 100 mg) > (30 mg/kg, 10 mg/kg, vehicle), 50 mg/kg > (10 mg/kg, vehicle), 30 mg/kg > vehicle in  A ; with 100 μg > (30 μg, 10 μg, vehicle), (30 μg, 10 μg) > vehicle in  B ; and with 100 μg > (3 μg, vehicle), (30 μg, 10 μg, 3 μg) > vehicle in  C .