Treadmill workouts alleviate neuropathic allodynia and scratching behavior in rats following thoracotomy

The aim of the experiment was to investigate the effects of treadmill exercise on postthoracotomy pain and the expression of spinal pro-inflammatory and anti-inflammatory cytokines.

Animals were randomly distributed into four groups: (a) sham surgery, (b) rats following 60 min thoracotomy and rib retraction (thoracotomy), (c) thoracotomy rats received treadmill training (thoracotomy+treadmill), and (d) sham surgery rats received treadmill training (sham surgery+treadmill). Treadmill workouts were started on postoperative day 10 (POD10) and lasted for 6 weeks (5 days per week). Rats were examined for cold allodynia using acetone and mechanical allodynia using von Frey hairs (in grams) at the surgical site. Spinal pro-inflammatory and anti-inflammatory cytokines were analyzed on PODs 28 and 49.

Both thoracotomy and thoracotomy+treadmill groups exhibited a decrease in mechanical force thresholds (g) and an increase in scratches per min on POD10. Mechanical hypersensitivity and incremental scratches lasted from POD14 and POD49 in the thoracotomy group. Although force thresholds and scratches remained not return to baseline, incremental force thresholds (p < 0.001) and diminutive scratches (p < 0.001) occurred after 6-week treadmill workouts. The rise in spinal interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) concentrations or the decline in spinal IL-10 concentration in thoracotomy+treadmill rats was less (p < 0.05) than thoracotomy rats without exercise.

Mechanical allodynia using von Frey filament testing and cold allodynia by acetone testing were improved in thoracotomy rats after treadmill workouts.. Treadmill exercise restrained excess pro-inflammatory cytokine expression but increased anti-inflammatory cytokine level in a rib retraction model.