Neuropharmacologic effects of vibration on the dorsal root ganglion: An animal model

The neuropharmacploglc effects of low frequency vibration on the dorsal root ganglion, a reported epidemiological cause of low-back pain, have only recently been described. This investigation was undertaken to validate the hypothesis that substance P and VIP, known to be produced in the dorsal root ganglion cell bodies, will be affected by low frequency vibration. Three New Zealand white rabbits were vibrated at discrete frequencies (2-10 Hz) to determine the resonant frequency of the rabbit spine. The resonating frequency was in the (3.5-5.0 Hz) range. The peak amplitude was at 4.5 Hz. Ten female New Zealand white rabbits were then paired into two groups of five. One group served as a control and had exactly the same procedures performed as the experimental group except for the vibration. The L4-5 and L5-6 dorsal root ganglia were removed bilaterally and prepared for substance P and VIP extraction by radioimmunoassay technique. The control rabbits mean ImmUnoreactive substance P was 14.06 pg/ml tissue, whereas the experimental or vibrated rabbits had a mean of 8.40 pg/ml (P < 0.003). The control rabbits mean immunoreactive vasoactive Intestinal peptide was 9.58 pg/ml whereas the experimental or vibrated rabbits had a mean of 20.9 pg/ml, P < 0.07. Substance P is only one of several dorsal root ganglion neuropeptides that may play a role in nociceptor transmlsssion. VIP is a neuropeptide that plays a role in reorganization of the nervous system following Injury. The effects of low frequency vibration on dorsal root ganglion transmitters are essential to the understanding of vibration as a cause of back pain. The localized decrease in substance P and increased VIP seen following low frequency vibration are compatible with results following peripheral Injury. The Increase in VIP may play a role In the pathophysiology processes in nerve and dorsal spinal cord following peripheral nerve Injury. The changes are compatible with our previous work and offer an opportunity to explore functional abnormalities associated with these findings.