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Sensory Nerve Ending Structures After 5 Weeks of Vibration Exposure
Chaowen Wu, MD-PhD1, Jordan Zimmerman, BS2, James Bain, MS2; Danny Riley, PhD12
1Plastic Surgery, Medical College of Wisconsin, Milwaukee, WI, 2Marquette University, Milwaukee, WI
Hand arm vibration syndrome (HAVS) is an occupational disease that causes debilitating numbness and vasospasm of the fingers. The mode of injury remains poorly understood which also inhibits preventative measures. Previous work has shown that one bout of 12 min vibration with a riveting hammer causes decreased sensation in the rat tail. However the effects on mechanosensory receptors of the skin have not been characterized. We aimed to study the effects of vibration on rat tail sensory nerve endings on the skin by examining changes after 5 weeks of vibration exposure.
8-wk-old Sprague-Dawley rats were divided into a tail-vibration group (n=8) and a sham-vibrated control group (n=8). The vibration group received 12 min of riveting hammer vibration exposure per day, 5 days per week for a total of 5 weeks. The Control group received the same treatment in terms of restraint and noise exposure, however they were not subjected to tail vibrations. When treatments were completed, the rats were euthanized and perfusion fixed with buffered formaldehyde. Mid-tail segments were removed, decalcified and frozen for cryostat sections. Lanceolate mechanosensory nerve endings surrounding hairs in the skin were immunostained by PGP9.5 and examined by fluorescence microscopy.
Interestingly, results showed that lanceolate nerve ending complexes appeared largely unchanged in number and organization between the vibrated and control non-vibrated groups. These findings may suggest that altered sensory perception is not a result of damage to sensory nerve endings at the skin level, but rather it may be secondary to changes in signal transduction in the peripheral or central nervous system. Alternatively, since PGP9.5 also stains Schwann cells, the observed complexes may represent preserved Schwann cell processes with or without intact nerve endings. Future experiments will be conducted to differentiate between Schwann cell processes and nerve endings of the lanceolate complex. This will determine whether vibration causes injury at the cutaneous mechanoreceptor level which may help in targeting preventative or treatment therapies for HAVS.
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