Neuroprotective effects of dexmedetomidine on the ketamine-induced disruption of the proliferation and differentiation of developing neural stem cells in the subventricular zone

Abstract

Background: Recently, the number of neonatal patients receiving surgery under general anesthesia has increased. Ketamine disrupts the proliferation and differentiation of developing neural stem cells (NSCs). Therefore, the safe use of ketamine in pediatric anesthesia has been an issue of increasing concern among anesthesiologists and the children’s parents. Dexmedetomidine (DEX) is widely used in sedation, as an antianxiety agent and for analgesia. DEX has recently been shown to provide neuroprotection against anesthetic-induced neurotoxicity in the developing brain. The aim of this in vivo study was to investigate whether DEX exerted neuroprotective effects on the proliferation and differentiation of NSCs in the subventricular zone (SVZ) following neonatal ketamine exposure. Methods: Postnatal day 7 (PND-7) male Sprague-Dawley rats were equally divided into the following 5 groups: Control group (n=8), Ketamine group (n=8), 1 μg/kg DEX+Ketamine group (n=8), 5 μg/kg DEX+Ketamine group (n=8) and 10 μg/kg DEX+Ketamine group (n=8). The proliferation and differentiation of NSCs in the SVZ were assessed using immunostaining with BrdU incorporation. The levels of Nestin and β-tubulin III in the SVZ were measured using Western blot analyses. Apoptosis was assessed by detecting the levels of the cleaved caspase-3 protein using Western blotting. Results: Neonatal ketamine exposure significantly inhibited NSC proliferation and astrocytic differentiation in the SVZ, and neuronal differentiation was markedly increased. Furthermore, pretreatment with moderate (5 μg/kg) or high doses (10 μg/kg) of DEX reversed the ketamine-induced disturbances in the proliferation and differentiation of NSCs. Meanwhile, neonatal ketamine exposure significantly decreased the expression of Nestin and increased the expression of β-tubulin III in the SVZ compared with the Control group. Treatment with 10 μg/kg DEX notably reversed the ketamine-induced changes in the levels of Nestin and β-tubulin III. In addition, a pretreatment with 10 μg/kg DEX before ketamine anesthesia prevented apoptosis in the SVZ induced by neonatal ketamine exposure. Conclusions: Based on our findings, DEX may exert neuroprotective effects on the proliferation and differentiation of NSCs in the SVZ of neonatal rats in a repeated ketamine anesthesia model.