Expression of neurotrophin mRNAs in the dorsal root ganglion after spinal nerve injury

Neurotrophins have specificity toward distinct subpopulations of dorsal root ganglion (DRG) neurons with different neurotrophin receptors. It has been suggested that neurotrophins also play important roles in mature DRG neurons after injury. In the present study, we examined the expression of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin 3 (NT-3) mRNAs in the DRG after a peripheral nerve injury. The data showed that following a spinal nerve ligation, the level of NGF mRNA increased 4 times over the normal level and was maintained at a high level for a period of 3 weeks. The induction of BDNF mRNA was brief (lasting less than 3 days) and lesser in quantity (~ 1.7 times increase) compared to NGF expression. The expression of NT-3 mRNA was not detected either in normal or nerve injured rats. Results suggest that different neurotrophins play different functional roles in the DRG after spinal nerve injury.