Regional, developmental, and cell cycle-dependent differences in μ, δ, and κ-opioid receptor expression among cultured mouse astrocytes
✍ Scribed by Anne Stiene-Martin; Rong Zhou; Kurt F. Hauser
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 596 KB
- Volume
- 22
- Category
- Article
- ISSN
- 0894-1491
No coin nor oath required. For personal study only.
✦ Synopsis
The diversity of opioid receptor expression was examined in astrocytes in low-density and non-dividing (confluent) cultures from the cerebral cortex, hippocampus, cerebellum, and striatum of 1-day-old mice. µ, ␦, and opioid receptor expression was assessed in individual cells immunocytochemically, by using flow cytometry, and functionally by examining agonist-induced changes in intracellular calcium ([Ca 2ϩ ] i ). Significant spatial and temporal differences were evident in the pattern of expression of µ, ␦, and receptors among astrocytes. In low-density cultures, greater proportions of astrocytes expressed µ-opioid receptor immunoreactivity in the cerebral cortex and hippocampus (26-34%) than in the cerebellum or striatum (7-12%). At confluence, a greater percentage of astrocytes in cerebellar (26%) and striatal (30%) cultures expressed µ-immunoreactivity. Fewer astrocytes possessed ␦-immunoreactivity in low-density striatal cultures (8%) compared to other regions (16-22%). The proportion of ␦ receptor-expressing astrocytes declined in the cerebellum but increased in the hippocampus. -opioid receptors were uniformly expressed by 27-34% of astrocytes from all regions, except in cortical cultures, where the proportion of expressing cells was 38% at low-density and decreased to 22% at confluence. Selective µ (PLO 17; H-Tyr-Pro-Phe (N-Me) -D-Pro-NH 2 , ␦ ([D-Pen 2 , D-Pen 5 ] enkephalin), or (U50,488H; trans-(Ϯ)-3,4-Dichloro-N-methyl-N-[2-(1-pyrrolidinyl) cyclohexyl] benzeneacetamide methanesulfonate) opioid receptor agonists increased [Ca 2ϩ ] i in subpopulations of astrocytes indicating the presence of functional receptors. Lastly, opioid receptor immunofluorescence varied during the cell division cycle. A greater proportion of astrocytes in the G 2 /M phase of the cell cycle were µ or ␦ receptor immunofluorescent than at G 0 /G 1 . When astrocytes were reversibly arrested in G 1 , significantly fewer cells expressed ␦ receptor immunofluorescence; however, upon reentry into the cell cycle immunofluorescent cells reappeared. In conclusion, opioid phenotype varies considerably among individual cultured astrocytes, and this diversity was determined by regional and developmental (age and cell cycle dependent) differences in the brain. These in vitro findings suggest astroglia contribute to regional and developmental idiosyncrasies in opioid function within the brain.