Fig. 2. Changes in mean arterial blood pressure and heart rate. (A ) Time course of mean arterial blood pressure after 3.0 μg intrathecal clonidine (open squares ) and 5.0 μg tizanidine (solid squares ). (B ) Time course of heart rate after 3.0 μg intrathecal clonidine (open squares ) and 5.0 μg tizanidine (solid squares ). * indicates a significant difference from the value before intrathecal drug administration (the value at time 0) (P < 0.05) (n = 6 for each drug).