Glycine receptors expression in rat spinal cord and dorsal root ganglion in prostaglandin E2 intrathecal injection models

BackgroundGlycine receptors (GlyRs) are involved in the development of spinal pain sensitization. The GlyR3 subunit has recently emerged as a key factor in inflammatory pain pathways in the spinal cord dorsal horn (DH). Our study is to identify the extent of location and cell types expressing different GlyR subunits in spinal cord and dorsal root ganglion (DRGs). To tease out the possible actions of GlyRs on pain transmission, we investigate the effects produced by GlyRs on acute inflammatory pain by behavioral testing using prostaglandin E2 (PGE2) intrathecal injection models. Furthermore, we investigate the changes of GlyR expression in DRGs and spinal cord in rats after the induction of acute inflammatory pain.ResultsCompared to the vehicle administration, the PGE2 intrathecal injection model produced significantly higher hyperalgesia, which started 3h after PGE2 injection and lasted more than 5h. PGE2 intrathecal injection significantly decreased GlyR1 and GlyR3 protein expressions in the L5 DH at 1h and lasted to 5h, and similar results were observed in the L5 DRG at 5h. Confocal microscopic images showed the co-existence of punctate gephyrin and GlyR3 immunoreactivity (IR) throughout the gray matter of the spinal cord, mainly in DH laminae I-III neurons and in ventral horn neurons. It also showed the co-existence of punctate gephyrin and GlyR3 IR in DRG neurons.ConclusionsIn this study, PGE2 intrathecal injection significantly decreased protein expression of gephyrin, GlyR1 and GlyR3 in spinal cord DH and DRG. The gephyrin and GlyR3 were localized on neuron cells both in the DH and DRG.