Effects of the blocker of N-methyl-D-aspartate receptor MK801 on the electrophysiological changes of CA1 neurons during hypoxia in isolated hippocampal slices of rats

Yucai ZHANG; Yinming ZENG; Jun WANG

ABSTRACT

BACKGROUND:

Pyramidal cells in hippocampal CA1 region are neurons most susceptible to ischemia-hypoxia damage. Their membrane potential is shown as hyperpolarization of cell membrane during early hypoxia. With the progress of hypoxia time, cell membrane has slow and rapid hyperpolarization, which causes irreversible damage to neurons.

OBJECTIVE:

To investigate the effects of the blocker of N-methyl-D-aspartate receptor MK801 on the electrophysiological changes of CA1 neurons during hypoxia in isolated hippocampal slices of rats with intracellular recording technique.

DESIGN:

Observational and controlled study.

SETTING:

The 97th Hospital of the Chinese PLA, Provincial Key Anesthesiology Laboratory of Xuzhou Medical College; Center of Health Science, State University of New York.MATERIALS The experiment was conducted from September 2002 to March 2003 in the State University of New York. Five adult male SD rats were anesthetized with 0.02 volume of isoflurane after 3 minutes' pre-oxygenation with oxygen.

METHODS:

The hippocampal slices from the rats were randomly divided into simple anoxia group (n=10) and MK801 group (n=10). The slices in simple anoxia group were only subjected to 10-minute hypoxia with the artificial cerebrospinal fluid (ACSF), and the slices in MK801 group were treated with 100 μmol/L MK801 for 10 minutes before and during 10 minutes of hypoxia. The neuronal membrane potential before hypoxia, the rate of slow depolarization, the amplitude of and time to rapid depolarization were recorded with intracellular recording technique described in the literature. Meanwhile, the neuronal response to the intracellular current injection and Schaffer collateral stimulation were observed respectively at the end of 60 minutes' re-oxygenation.gion of hippocampal slices It was significantly higher in simple anoxia group than in MK801 group [(0.20±0.05) mV/s, (0.08±0.03) mV/s, P ＜ 0.05].hippocampal slices It was significantly higher in MK801 group than in of rapid depolarization of pyramidal cells in CA1 region of hippocampal slices It was significantly lower in MK801 group than in simple anoxia sponse to stimuli was recovered in 9 out of 10 neurons.

CONCLUSION:

MK801 blocker of N-methyl-D-aspartate receptor can decrease the rate of slow depolarization of neurons induced by hypoxia, postpone the onset of rapid depolarization of neurons, and decrease the amplitude of rapid depolarization of neurons. This suggests that the blocker of N-methyl-D-aspartate receptor can relieve the hypoxic damage to neurons and promote the functional recovery of neurons.