Vibration-Induced Disruption of Axoplasmic Transport in Peripheral Nerve

Prolonged exposure to hand-transmitted vibration by power tools has been known to cause debilitating vascular, neurologic, and musculoskeletal problems. Although hand-arm vibration syndrome (HAVS) is currently the most diagnosed disease entity in the United Kingdom today, the essential etiology of the injury remains unclear. This reported study was undertaken to evaluate the effect of vibration exposure on axoplasmic transport of the peripheral nerve.

Thirty male Sprague-Dawley rats were divided into three groups of 10 rats each, designated as Group A—control, no vibration; Group B—vibration 5 hr/day × 2 days; and Group C—vibration 5 hr/day × 10 days. Prior to vibration, the soleus muscle of each rat was dissected and a solution containing 2% wheat germ agglutinin (WGA), conjugated with horseradish peroxidase (HRP) was injected into the muscle of all rats. After injection, the hindlimbs of the rats were secured to a vibrating platform for the allotted vibration period. After the completion of vibration, the rats had a 24-hr survival period, followed by harvesting of the soleus musclce, its nerve branch, the tibial nerve, sciatic nerve, and the spinal cord.

In the peripheral nerves of the control group, there was homogenous retrograde tracer staining of the axons, with the remainder of the nerve devoid of staining. In contrast to the control, the 2-day vibration staining showed intense punctate deposits running the length of the nerve. There was also obvious stasis in the vein of the sciatic nerve, manifested as a dense, rough, black line. The 10-day vibration group had no staining evident within the sciatic nerve proximally, while intense staining indicating severe axonal damage was evident at the distal sections. In the anterior horn of the spinal column, the control group showed intensely labeled motor neurons, indicating retrograde axoplasmic flow, while no labeled neurons were seen in the 2-day vibration group. Minimal staining of the motor neurons was seen in the 10-day vibration group.

The authors demonstrated that short-term vibration impeded axoplasmic transport in the peripheral nerves of the rat hindlimb. These effects of vibration appear to be cumulative, as axonal staining was markedly decreased by 2 days of vibration and absent by 10 days of vibration.