Distribution of downstream regulatory element antagonist modulator (DREAM) in rat spinal cord and upregulation of its expression during inflammatory pain.

A previous knockout study revealed the critical role of downstream regulatory element antagonist modulator (DREAM) in pain processing in the spinal cord by transcriptional regulation of prodynorphin (PPD) gene. Here, we report that, in contrast to the nuclear localization of other transcription factors, DREAM showed a punctate staining pattern in rat spinal dorsal horn in immunofluorescent analysis, with a membrane localization profile in some neurons and its expression accumulated in the inner zone of lamina II. In an inflammatory pain model induced by complete Freund's adjuvant (CFA) injection, we used Western blot analysis and detected transient upregulation of DREAM in the nuclear fraction of ipsilateral spinal dorsal horn at 2 h and 6 h post-injection, and a slow upregulation in the membrane fraction for 7 days. These studies suggest that DREAM might have other roles in pain modulation in the spinal cord in addition to its well-known role as a transcriptional repressor.