β-Endorphin processing and cellular origins in rat spinal cord

While enkephalin and dynorphin peptides have been well characterized in the spinal cord, the cellular localization of β-endorphin (βE) and the processing of pro-opiomelanocortin (POMC) to βE and other non-opioid peptides in the cord have not been extensively investigated. Other investigators have characterized the various βE forms present in rat spinal cord regions. Previous studies have also suggested that spinal POMC content is entirely derived from supraspinal sources. However, high proportions of βE precursors present in spinal cord sieving profiles led us to suspect the presence of POMC cell bodies intrinsic to the cord. In this study, we performed thoracic spinal cord lesions on a group of animals and demonstrated the persistence of about one-third of control levels of βE immunoreactivity (βE-IR) below the level of the lesions. We also characterized POMC processing in various regions of the spinal cord both before and after lesioning. These data suggested that there may be intrinsic POMC/endorphinergic neuronal systems in the spinal cord.