Toxicology
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Ketamine and its stereoisomer S(+)-ketamine are widely used for sedation in pediatric anesthesia and intensive care medicine. Numerous experimental studies indicate that ketamine is potentially toxic to the developing brain. Here, we examined the long-term effects of NMDA receptor blockade on NMDA receptor subunit expression, alterations in neuronal Ca(2+)-oscillations and apoptosis. ⋯ This was accompanied by an increase in NR1 mRNA but not the NR2A and B subunit expression at the same time point. 24h following washout of the specific drug, a significant elevation of the pro-apoptotic marker BAX, as well as activated Caspase-3 positive neurons, could be detected in cultures exposed to 100μM MK801 and 25μM S(+)-ketamine. Here, we show that long-term blockade of the NMDA receptor in developing rat hippocampal neurons significantly increased NR1 subunit expression, and that this was associated with an alteration in neuronal activity. Apoptosis was only induced 24h after withdrawal of long-term blockade for high doses of S(+)-ketamine.
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Comparative Study
Sensitivity of neuroprogenitor cells to chemical-induced apoptosis using a multiplexed assay suitable for high-throughput screening.
High-throughput methods are useful for rapidly screening large numbers of chemicals for biological activity, including the perturbation of pathways that may lead to adverse cellular effects. In vitro assays for the key events of neurodevelopment, including apoptosis, may be used in a battery of tests for detecting chemicals that could result in developmental neurotoxicity. Apoptosis contributes to nervous system development by regulating the size of the neuroprogenitor cell pool, and the balance between cellular proliferation and apoptosis during neuroprogenitor cell proliferation helps to determine the size and shape of the nervous system. ⋯ The results show that all three commercially available models generated a robust source of proliferating neuroprogenitor cells, and that the assay was sensitive and reproducible when used in a multi-well plate format. There were differences in the response of rodent and human neuroprogenitor cells to a set of chemicals previously shown to induce apoptosis in vitro. Neuroprogenitor cells were more sensitive to chemical-induced apoptosis than differentiated neurons, suggesting that neuroprogenitor cells are one of the cell models that should be considered for use in a developmental neurotoxicity screening battery.