Fig. 2.

Heart rate and the sympathetic support of heart rate in intact and T5X rats. Effects of midthoracic spinal cord injury on heart rate and the sympathetic support of heart rate (demonstrated by the action of beta-adrenergic receptor blockade) in 10 intact male rats. Following the experimental procedures in the intact condition (weeks 1 and 2), 6 of the 10 rats were subjected to T5X, and the remaining 4 rats were subjected to sham T5X (indicated by the arrow) and subsequently studied 1, 3, 7, 14 and 21 days postsurgery. Without beta blockade, heart rate was higher following spinal cord injury (SCI). Beta-adrenergic receptor blockade lowered heart rate more in T5X compared with sham-operated intact rats; however, heart rates remained higher in T5X rats, starting with day 3, compared with intact rats following beta-adrenergic receptor blockade. *P < 0.05, intact vs. T5X; #P < 0.05, no drug vs. β-x.