Mu- and delta-opioid receptor antagonists decrease proliferation and increase neurogenesis in cultures of rat adult hippocampal progenitors

• Published in: The European journal of neuroscience 2003-03, Vol.17 (6), p.1159-1172
• Main Authors: Persson, Anders I., Thorlin, Thorleif, Bull, Cecilia, Zarnegar, Parisa, Ekman, Rolf, Terenius, Lars, Eriksson, Peter S.
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis; Astrocytes - drug effects; beta-Endorphin - metabolism; Blotting, Western; Cell Count; Cell Culture Techniques; Cell Differentiation - drug effects; Gene Expression - drug effects; Hippocampus - drug effects; Hippocampus - metabolism; Immunohistochemistry; L-Lactate Dehydrogenase - metabolism; Mitogen-Activated Protein Kinases - metabolism; Mitosis - drug effects; Narcotic Antagonists - pharmacology; Neurons - drug effects; Neurons - metabolism; Neurosciences; Neurovetenskaper; Oligodendroglia - drug effects; Oligonucleotide Array Sequence Analysis; Radioimmunoassay; Rats; Receptors, Opioid, delta - antagonists & inhibitors; Receptors, Opioid, delta - metabolism; Receptors, Opioid, mu - antagonists & inhibitors; Receptors, Opioid, mu - metabolism; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction - drug effects; Stem Cells - drug effects; Stem Cells - metabolism
• ISSN: 0953-816X; 1460-9568; 1460-9568
• DOI: 10.1046/j.1460-9568.2003.02538.x

Opioids have previously been shown to affect proliferation and differentiation in various neural cell types. In the present study, cultured rat adult hippocampal progenitors (AHPs) were shown to release β‐endorphin. Membrane preparations of AHPs were found to bind [125I]β‐endorphin, and immunoreactivity for mu‐ and delta‐opioid receptors (MORs and DORs), but not for kappa‐opioid receptors (KORs), was found on cells in culture. Both DNA content and [3H]thymidine incorporation were reduced after a 48‐h incubation with 100 µm naloxone, 10 µm naltrindole or 10 µmβ‐funaltrexamine, but not nor‐binaltorphimine, suggesting proliferative actions of endogenous opioids against MORs and DORs on AHPs. Furthermore, analysis of gene and protein expression after incubation with MOR and DOR antagonists for 48 h using RT‐PCR and Western blotting suggested decreased signalling through the mitogen‐activated protein kinase (MAPK) pathway and lowered levels of genes and proteins that are important in cell cycling. Cultures were incubated with naloxone (10 or 100 µm) for 10 days to study the effects on differentiation. This resulted in an approximately threefold increase in neurogenesis, a threefold decrease in astrogliogenesis and a 50% decrease in oligodendrogenesis. In conclusion, this study suggests that reduced signalling through MORs and DORs decreases proliferation in rat AHPs, increases the number of in vitro‐generated neurons and reduces the number of astrocytes and oligodendrocytes in culture.