RESUMEN
To investigate whether the change of alpha 2A -AR mRNA expression in the DRG is an underlying mechanism of sympathetically maintained neuropathic pain (SMP), in situ hybridization for alpha 2A -adrenergic receptor (AR) mRNA with digoxigenin -labeled RNA probe in the rat DRG was conducted after tight ligation of the 5th lumbar (L5) spinal nerve up to 12 weeks. Majority of the DRG neurons expressed alpha 2A -AR mRNA and a few satellite cells expressed alpha 2A -AR mRNA in the DRG of the contralateral side. The number of the alpha 2A -AR mRNA positive DRG neurons dropped significantly at 7 day post -operation (7D PO). On the other hand, there was great increase in the number of the alpha 2A -AR positive satellite cells at 7D PO. Then, the number of the alpha 2A -AR mRNA positive DRG neurons was increased and the number of the alpha 2A -AR mRNA positive satellite cells was decreased from 7D PO to 12 weeks PO. Surgical sympathectomy reduced neuropathic pain behaviors in animal models of neuropathic pain suggest that downregulation of alpha 2A -AR mRNA expression in the injured DRG neurons following the ligation itself might be not related to SMP, but the role of upregulation of alpha 2A -AR mRNA expression in the satellite cells remain to be explored.