Morphine Modulates Adult Neurogenesis and Contextual Memory by Impeding the Maturation of Neural Progenitors

• Published in: PloS one Vol. 11; no. 4; p. e0153628
• Main Authors: Zhang, Yue, Xu, Chi, Zheng, Hui, Loh, Horace H., Law, Ping-Yee
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 14.04.2016; Public Library of Science (PLoS)
• Subjects: Addictions; Analgesics, Opioid - pharmacology; Animals; Animals, Newborn; Apoptosis; Beta2 protein; Biology and Life Sciences; Biomarkers; Cell Differentiation - drug effects; Cocaine; Comparative analysis; Conditioning; Conditioning, Operant - drug effects; Differentiation; Doublecortin protein; Drug abuse; Genetic aspects; Green Fluorescent Proteins - genetics; Green Fluorescent Proteins - metabolism; Heroin; Hippocampus - cytology; Hippocampus - metabolism; Immunohistochemistry; Localization; Male; Medicine and Health Sciences; Memory - drug effects; Methamphetamine; Mice; Mice, Inbred C57BL; Mice, Transgenic; Morphine; Morphine - pharmacology; Narcotics; Nestin; Neural stem cells; Neural Stem Cells - drug effects; Neural Stem Cells - metabolism; Neurogenesis; Neurogenesis - drug effects; Neurons; Neurons - drug effects; Neurons - metabolism; Opiates; Opioids; Pharmacology; Physiological aspects; Place preference conditioning; Proopiomelanocortin; Research and Analysis Methods; Rodents; Spatial Learning - drug effects; Stem cell transplantation; Stem cells; Training; Tubulin; United States; China; United States > US; Minnesota
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0153628

The regulation of adult neurogenesis by opiates has been implicated in modulating different addiction cycles. At which neurogenesis stage opiates exert their action remains unresolved. We attempt to define the temporal window of morphine's inhibition effect on adult neurogenesis by using the POMC-EGFP mouse model, in which newborn granular cells (GCs) can be visualized between days 3-28 post-mitotic. The POMC-EGFP mice were trained under the 3-chambers conditioned place preference (CPP) paradigm with either saline or morphine. We observed after 4 days of CPP training with saline, the number of EGFP-labeled newborn GCs in sub-granular zone (SGZ) hippocampus significantly increased compared to mice injected with saline in their homecage. CPP training with morphine significantly decreased the number of EGFP-labeled GCs, whereas no significant difference in the number of EGFP-labeled GCs was observed with the homecage mice injected with the same dose of morphine. Using cell-type selective markers, we observed that morphine reduced the number of late stage progenitors and immature neurons such as Doublecortin (DCX) and βIII Tubulin (TuJ1) positive cells in the SGZ but did not reduce the number of early progenitors such as Nestin, SOX2, or neurogenic differentiation-1 (NeuroD1) positive cells. Analysis of co-localization between different cell markers shows that morphine reduced the number of adult-born GCs by interfering with differentiation of early progenitors, but not by inducing apoptosis. In addition, when NeuroD1 was over-expressed in DG by stereotaxic injection of lentivirus, it rescued the loss of immature neurons and prolonged the extinction of morphine-trained CPP. These results suggest that under the condition of CPP training paradigm, morphine affects the transition of neural progenitor/stem cells to immature neurons via a mechanism involving NeuroD1.