Repeated administration of ketamine can induce hippocampal neurodegeneration and long-term cognitive impairment via the ROS/HIF-1α pathway in developing rats.

BACKGROUND

Recent animal experiments have suggested that ketamine administration during development might induce widespread neurodegeneration and long-term cognitive deficits. The underlying mechanism is not fully understood.

METHODS

Immature rat hippocampal neurons and newborn rats underwent repeated exposure to ketamine, ketamine+inhibitor of hypoxia-inducible factor (HIF)-1α(YC-1), ketamine+inhibitor of reactive oxygen species(ROS) (L-carnitine) or ketamine+Ca(2+) blocker(nimodipine). Apoptosis of the hippocampal neurons was analyzed by TUNEL and flow cytometry. Intracellular ROS were measured using 2',7'-dichlorofluorescein diacetate. The expression of HIF- 1α and apoptosis-related proteins was analyzed by western blot or qPCR. As these rats grew, behavioral tests were performed to evaluate cognitive function.

RESULTS

The apoptotic rate in the ketamine group was significantly higher than that in the other groups, and the intracellular ROS levels in the ketamine and ketamine+YC-1 groups were higher than those in the other groups. The expression of HIF- 1α, p53, BNIP3 and cleaved caspase-3 proteins increased, and the ratio of Bcl-2/Bax decreased in the ketamine group. The transcriptional levels of HIF-1α in the ketamine and ketamine+YC-1 groups were higher than those in the other groups. Cognitive deficits were found only in the ketamine group.

CONCLUSION

We suggest that ketamine-induced neurodegeneration in neonatal rats, followed by long-term cognitive deficits, might be mediated via the ROS/HIF-1α pathway.