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

The neuropharmacologic 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 less than 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 less than 0.07. Substance P is only one of several dorsal root ganglion neuropeptides that may play a role in nociceptor transmission. 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.(ABSTRACT TRUNCATED AT 250 WORDS)