Understanding vibration-induced injury of peripheral nerves and arteries

Hand-arm vibration syndrome, a vasospastic and peripheral neuropathic condition occurring primarily in colder regions of the world, is caused by years of exposure to hand-transmitted vibration from powered tools. In order to develop preventive measures, it is important to understand the early, pre-syndrome effects of vibration on peripheral arteries and nerves. The Curry 'rat-tail vibration model' simulates hand-transmitted vibration. Previous work demonstrated that a 4-hr bout of vibration at room temperature damaged vascular smooth muscle and endothelial cells of the tail artery. Vibration induced vasoconstriction. Pre-administration of nifedipine, a calcium channel blocker, prevented vasoconstriction and ameliorated vascular damage. My studies utilized the rat-tail vibration model to investigate the interaction of cold with vibration, the effects of altering the pattern of vibration from continuous to intermittent, and the process of smooth muscle vacuolization damage.; Adult male, Sprague Dawley rats were vibrated at 60 Hz, 49 m/s 2 for 4 hrs, with or without tail cooling with ice to test if vibration at cold temperature was more injurious to arteries and nerves than room temperature. Animals that were sham vibrated at room temperature or with tail cooling served as controls. While vibration with tail cooling resulted in smaller vascular lumen sizes, there were significantly fewer smooth muscle cell vacuoles compared to vibration without cooling. Vibration at both temperatures and cold exposure alone caused myelin disruption in nerves and increased tyrosine nitration presumably from free radicals in arteries. The tail nerves from the cold and cold-plus-vibration groups compared to sham and vibration at room temperature exhibited greater edema and showed dilatation of arterioles and venules containing dismorphic erythrocytes in the lumen, indicating blood stasis. Cold-induced prolongation of the tail flick response time recovered earlier in cold plus vibration by an unknown mechanism. These findings emphasize the importance of considering the contribution of temperature in the pathophysiology of hand-arm vibration injury. (Abstract shortened by UMI.)...