Effects of whole body vibration on dorsal root ganglion neurons. Changes in neuronal nuclei.

Abstract

This blinded, histomorphometric analysis compared neuronal nuclei from lumbar dorsal root ganglia from three groups of rabbits: normal controls, immobilized controls, and an experimental group exposed to daily, whole body vibration. To identify ultrastructural changes in dorsal root ganglion neurons consistent with, and capable of producing, neuropeptide changes previously documented in vibration-exposed animals. Normal adult rabbits were exposed to modulated whole body vibration at a frequency and amplitude previously shown to produce changes in dorsal root ganglion neuropeptides. Lumbar ganglia from control and vibrated rabbits were fixed, stained, and studied under transmission electron microscopy. One-thousand-two-hundred cells were sampled, and 190 appropriately sectioned cells were analyzed. Epidemiologic studies have suggested a strong correlation between vibration and back pain. Previous studies have shown that short-term exposure to whole body vibration alters the normal neuropeptide profile seen in dorsal root ganglion neurons. Nuclear clefting was increased 39% in vibrated nuclei relative to controls, and nuclear pores were increased 46% in areas of clefting compared with adjacent nonclefted segments and controls (P < .001). Mitochondria, rough endoplasmic reticulum, and free ribosomes crowded the cleft spaces of vibrated cells, and the normal perinuclear clear space was lost. Mitochondrial and lysosomal volumes were significantly increased in vibrated cells. These ultrastructural changes, generated by a physiologically valid vibration stimulus, provide an anatomic link between the clinical observation of increased back pain and the biochemical alterations involving pain-related neuropeptides.