Ketamine Inhibits Proliferation of Neural Stem Cell from Neonatal Rat Hippocampus in Vitro

Background/Aims: Ketamine is a widely used anesthetic in obstetric and pediatric anesthesia. In the developing brain, the widespread neuron apoptosis triggered by ketamine has been demonstrated. However, little is known about its effect on neural stem cells (NSCs) function. This study aimed to investigate the effect of ketamine on proliferation of NSCs from neonatal rat hippocampus. Methods: Neural stem cells were isolated from the hippocampus of Sprague-Dawley rats on postnatal day 3. In dose-response experiments, cultured neural stem cells (NSCs) were exposed to different concentrations of ketamine (0-1000 µM) for 24 hrs. The proliferative activity of NSCs was evaluated by 5-Bromo-2′-deoxyuridine (BrdU) incorporation assay. Apoptosis of neural stem cells were assessed using caspase-3 by western blot. The intracellular Ca2+ concentration ([Ca2+]i) in NSCs was analyzed by flow cytometry. The activation of protein kinase C-α (PKCα) and the phosphorylation of extracellular signal-regulated kinases 1/2 (ERK1/2) were measured by western blot analysis. Results: Clinical relevant concentration of ketamine (10, 20 and 50 µM) did not markedly alter the proliferation of NSCs from neonatal rat hippocampus in vitro. However, ketamine (200, 500, 800 and 1000μM) significantly inhibited the proliferation of NSCs and did not affect the expression of caspase-3. Meanwhile, ketamine (200, 500, 800 and 1000μM) also markedly decreased [Ca2+]i as well as suppressed PKCα activation and ERK1/2 phosphorylation in NSCs. A combination of subthreshold concentrations of ketamine (100 μM) and Ca2+ channel blocker verapamil (2.5 μM), PKCα inhibitor chelerythrine (2.5 μM) or ERK1/2 kinase inhibitor PD98059 (5 μM) significantly produced suprathreshold effects on PKCα activation, ERK1/2 phosphorylation and NSC proliferation. Conclusion: Ketamine inhibited proliferation of NSCs from neonatal rat hippocampus in vitro. Suppressing Ca2+-PKCα-ERK1/2 signaling pathway may be involved in this inhibitory effect of ketamine on NSCs proliferation