Electron microscopic study of brain tissue and EEG of mouse after acute heat stress / 解放军医学杂志

ABSTRACT

Objective To study the changes in the central nervous system in adult mice after various degrees of acute heat stress. Methods Adult mice placed in insulated cages were exposed to 24℃, 34℃, 37℃, 38.5℃, 40℃ or 42℃ for 60min respectively with a constant humidity of 60%. The behavior response was carefully monitored. Rectal temperature was measured before the exposure and after the exposure. Electroencephagrams were taken. Then the hippocampal neurons of these animals were examined with transmission electron microscope. Results Heat stress at 34℃ for 60 min only raised the rectal temperature, and heat stress above 37℃ for 60 min not only raised rectal temperature, but also induced water loss and irritability and attempt to escape. Abnormal EEG with increased amplitude and retarded rhythm could be observed. However, when mice were exposed to 24℃ and 34℃ such behavior did not appear. After exposure to 42℃, EEG frequency increased and pathological changes in hippocampus neurons were found. The main ultrastructural changes included degeneration of hippocampal neurons, expansion of space around capillary, decrease in number of synaptic vesicle, and decomposition of synapse. Conclusion Mice were very sensitive to heat stress. An increase in core temperature could induce behavioral thermoregulation. EEG and electron microscopic study revealed changes in the central nervous system after heat stress. Following exposure to high environmental temperature under 40℃, acute dysfunction of brain was reversible. At 42℃, damage to the brain tissue occurred, and most mice died of heat stroke.