Intensive motor training accelerates Axonal Regeneration following peripheral nerve Injury in Rats

Abstract

Background: Peripheral nerve injury (PNI) results in a broad range of sensory and motor symptoms that depend on the severity of the injury and types of nerves involved. Many attempts to repair PNI have yielded limited outcome leading to sensory and motor deficits. Recent evidence has shown that physical training promotes the synthesis of nerve growth factors, needed to facilitate axonal regeneration. Aim: To show that intensive motor training improves the sensory and motor functions in rats with sciatic nerve compression. Methods: Adult male Sprague-Dawley rats had their right sciatic nerve crushed using fine forceps and were randomly divided into 4 groups and subjected for a month to different types of motor exercises (5 days-week). Groups 1 and 2 were trained for 1 hour (two 30 min interval separated by 10 min resting period). Rats in Group 1 were placed on a horizontal treadmill daily (8m-min), while those in group 2 were placed on the Rotarod (35 rpm; 8m-min). Group 3 were subjected to both the treadmill (30 min) and Rotarod (30 min) separated by 10 min resting period. Group 4 acted as control and were housed in standard cages for an equivalent period. To assess for nerve regeneration; behavioral, histological and electrophysiological tests were performed. All rats were evaluated for sensory recovery, and hypersensitivity to thermal and mechanical stimuli at 1, 5, 12, 19 and 26 days post injury. Locomotor performance was also assessed using the staircase test. Counting the number of grips and time taken to climb up and down the stairs were done before and at different time points post-surgery. Histologically, a whole mount immuno-florescence staining protocol was adopted to analyze the extent of regenerating axons using antibodies against neurofilament and myelin basic protein. Images of the stained nerves were then visualized using a laser scanning confocal microscope. The compound motor action potential (CMAP) were recorded twenty-six days after physical training to assess functional connections in the