Changes in the alpha2-Adrenergic Receptor Subtypes Gene Expression in Rat Dorsal Root Ganglion and Spinal Cord in an Experimental Model of Neuropathic Pain / 대한해부학회지

ABSTRACT

While the pathophysiological mechanism by which sympathetic nervous system generates neuropathic pain is not clear, it is thought to involve an alpha-adrenergic receptor (AR). In the present experiment, we have elucidated the distribution of alpha2-AR subtypes mRNA in the DRG and spinal cord of normal rat with in situ hybridization (ISH) and analyzed changes in their expression in an experimental model of neuropathic pain with reverse transcriptase-polymerase chain reaction (RT-PCR). The results obtained were as follows; 1. The majority of small, medium and large DRG neurons of non-operated rats expressed alpha2C-AR mRNA. alpha2A-AR-expressing neurons were primarily medium-sized and large, comprising about 16% of the total neurons present. alpha2B-AR-expressing neurons were not identified. In the spinal cord, alpha2A-AR mRNA were localized in neurons of lamina II and III, and large motor neurons in the ventral horn. alpha2C-AR mRNA was found in large motor neurons. 2. In the ligated animals, RT-PCR results showed that alpha2A-AR mRNA levels in L5, 6 DRGs on the ipsilateral side significantly increased compared to those of the contralateral sides and also to those of sham-operated rats. alpha2C-AR mRNA levels showed a marked decrease in ipsilateral L5, 6 DRGs. In the spinal cord, there was no detectable changes in alpha2A- and alpha2C-AR mRNAs levels. The present results indicate that alpha2A- and alpha2C-ARs in the DRG may play an important role in generating sympathetically maintained neuropathic pain and that alpha2-AR in the spinal cord seems not to be involved.