Injured effects of electromagnetic pulse on hippocampal neurons and [Ca2+]i

Qian XU; Shaochen LIU; Yuhong LI; Lixin MEI; Yingchun ZHANG

ABSTRACT

BACKGROUND:

Electromagnetic pulse (EMP) radiation can affect the learning and memory function of experimental rats and induce injury of hippocampal issues and change of ultrastructure of rats.

OBJECTIVE:

To observe the effects of EMP on injury of hippocampal neurons cultured in vitro and [Ca2+]i, and analyze deeply possible mechanism of cerebral injury induced by EMP.

DESIGN:

Randomized controlled animal experiment.

SETTING:

Department of Pathology, Chengde Medical College.MATERIALS Several Wistar neonate rats, of either sex (half and half),were selected. Source of EMP radiation was high intensity EMP dummy source.

METHODS:

The experiment was performed from March to December 2004 at the Academy of Military Medical Science and Chengde Medical College, respectively. Several Wistar neonate rats were decapitated to take out the brains under narcotization. Hippocampal tissues were isolated. The cell suspension was adjusted to 5×108 L-1 for inoculation. Grouping ①Cultured cells were assigned into control group and radiation group. Cells were collected immediately after radiation to perform observation of morphology and determination of free calcium ion concentration. ②Other cultured cells were divided into control group, 0-hour radiation group and 12-hour radiation group. Cell apoptosis rate and necrosis rate were determined. (Dosage of cultured cells one culture flask of each group was checked in each item for 3 times). EMP radiation was in 6×104 V/m, with pulse rise time of 20 ns,pulse width of 30 μs, frequency of 2.5 pulses/min, totally for 2 minutes.EMP radiation was performed in primary cultured hippocampal neurons,and then morphological change of neurons was observed under inverted phase contrast microscope before and after radiation. Cell apoptosis and necrosis were measured with FACS method; Free [Ca2+]i concentration in neurons was measured with Fluo-3-AM fluorescent probe loading and laser confocal microscopy scanning.MAIN OUTCOME

MEASURES:

Morphological change of neuron, cell apoptosis rate and necrosis rate and free [Ca2+]i concentration.

RESULTS:

①Immediately after EMP radiation, the onset of colliquation appeared in nerval cells gradually, and neurite was recovery and degeneration. ②Apoptosis rate after 12-hour EMP radiation recovered as compared with that at hour 0 after radiation, but significantly increased as compared with the control group [(59.27±1.27)%, (72.17±6.21)%, (17.45±5.63)%,P＜0.05]. ③Necrosis rate at hour 0 and hour 12 after radiation increased as compared with the control group, but there was no statistical significant difference [(13.71±2.31)%, ( 11.96±1.04)%, (8.45±0.67)% ,P ＞ 0.05].④[Ca2+]i fluorescence intensity at hour 0 after EMP radiation was higher obviously than that in the control group (107.34±26.14,54.93±16.08,P ＜ 0.05).

CONCLUSION:

EMP induces morphological injury, necrosis and increase of apoptosis rate in hippocampal neurons, and Ca2+ fluorescence intensity increases markedly in neurons.