Endogenous opioids and oligodendroglial function: Possible autocrine/paracrine effects on cell survival and development

✍ Scribed by Pamela E. Knapp; Olga S. Itkis; Lixin Zhang; Barbara A. Spruce; Georgy Bakalkin; Kurt F. Hauser

• Book ID: 102224121
• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 242 KB
• Volume: 35
• Category: Article
• ISSN: 0894-1491
• DOI: 10.1002/glia.1080

✦ Synopsis

Abstract

Previous work has shown that oligodendrocytes (OLs) express both μ‐ and κ‐opioid receptors. In developing OLs, μ receptor activation increases OL proliferation, while the κ‐antagonist nor‐binaltorphimine (NorBNI) affects OL differentiation. Because exogenous opioids were not present in our defined culture medium, we hypothesized that NorBNI blocked endogenous opioids produced by the OLs themselves. To test this, intact and partially processed proenkephalin and prodynorphin‐derived peptides were assessed in OLs using immunocytochemistry or Western blot analysis, or both. Immature OLs possessed large amounts of intact and partially processed proenkephalin precursors, as well as posttranslational products of prodynorphin including dynorphin A (1–17). With maturation, however, intact or partially processed proenkephalin was expressed by only about 50% of OLs, while dynorphin A (1–17) was undetectable. To assess the function of OL‐derived opioids, the effect of κ‐agonists/antagonists on OL differentiation and death was explored. κ‐Agonists alone had no effect. In contrast, NorBNI significantly increased OL death. Additive OL losses were evident when NorBNI was paired with toxic levels of glutamate, suggesting that κ‐receptor blockade alone is sufficient to induce OL death. Thus, the results indicate that OLs express proenkephalin and prodynorphin peptides in a developmentally regulated manner, and further suggest that opioids produced by OLs modulate OL maturation and survival through local (i.e., autocrine and/or paracrine) mechanisms. GLIA 35:156–165, 2001. © 2001 Wiley‐Liss, Inc.