Fig. 1. Antithermal hyperalgesic effects of intrathecal clonidine and tizanidine. (A ) Time course of the withdrawal latencies to noxious heat stimuli after 3.0 μg intrathecal clonidine (open squares ) and 5.0 μg tizanidine (solid squares ) (n = 7 for each drug). (B ) Dose–response effect of intrathecal clonidine (n = 6–8 for each dose). Pre = withdrawal latency before intrathecal drug administration; before CCI = withdrawal latency before the nerve ligation. Data are presented as mean ± SD. * and # indicate significant difference from withdrawal latency before intrathecal clonidine and tizanidine administration, respectively (P < 0.05). ** indicates significant difference from the withdrawal latency before intrathecal drug administration (the value at pre) (P < 0.05).