Fig. 4. Antinociception in animals with spinal nerve ligation from intrathecal clonidine to von Frey filament testing in animals treated with intrathecal saline (filled bars ) or the muscarinic receptor antagonist atropine (open bars ). Atropine reduced the effect of clonidine (*P < 0.05 compared with saline treatment). Each symbol represents the mean ± standard error of four animals. t  indicates P < 0.05 compared with preclonidine value.