Effects of environmental temperature on physiological function of the brain of the rats suffered hypoxic-ischemic brain insult during neonatal period.

为了探讨脑冷却对新生儿缺氧缺血性脑损伤的影响，我们采用动物模型进行了脑冷却实验。在启发麻醉下，结扎7日龄大鼠新生儿左颈总动脉，暴露于缺氧空气（含氧8%）中。缺氧暴露后，我们将新生大鼠分为三组。第一组（低温组）置于低环境温度室内24小时，使大鼠达到低温（30度）。第二组（常温组）置于常温室内24小时，使大鼠体温保持在常温状态。第三组是对照组，他们做了一个假手术。饲养3个月后，对3组进行听觉脑干反应（ABR）。所有大鼠在轻度麻醉下均成功记录ABR。常温组III、V峰峰间潜伏期较低温组和对照组明显延长。正常体温组的V峰振幅与I峰振幅之比也明显小于其他各组。光镜及成像数据处理软件显示，正常体温组的下丘明显萎缩。上述结果提示，缺氧缺血性损伤后，高环境温度对大鼠中脑功能的损害大于低环境温度对中脑功能的损害。我们还利用光学记录对神经元回路的功能进行了初步的研究，发现低灌注温度下的光学记录可能是研究受损新生儿动物模型脑功能损伤的一种有用的研究工具。

In order to investigate the effect of brain cooling of the neonate suffered hypoxic-ischemic brain-damage, we performed experiments using animal model. Under the inspired anesthesia, we ligated left common carotid artery of the 7-day-old rat neonate, and exposed them to the hypoxic air (oxygen 8%). After the hypoxic exposure, we divided the rat neonates to three groups. The first group (hypothermia group) was kept in a room of low environmental temperature for 24 hr, which led the rats to the hypothermia (30 degree). The second group (normothermia group) was kept in a room of normal temperature for 24 hr, which kept the rat body temperature in normothermia. The third group was a control, which had a sham operation. After rearing for three months, we performed auditory brainstem response (ABR) for three groups. ABR was successfully recorded in all the rats under light anesthesia. The interpeak latency of III and V peaks of the normothermia group was significantly elongated than those of the hypothermia and control group. The ratio of the amplitude of V peak versus I peak of the normothermia group was also significantly small than those of the other groups. The inferior colliculus of the normothermia group was significantly atrophic than those of the other groups by using light microscope and imaging-data processing software. These findings indicate that high environmental temperature for the neonate rats after the hypoxic-ischemic insult caused more damages in rat midbrain function than low environmental temperature does. We also performed preliminary investigation on the function of neuronal circuit using optic recording, and found that optic recording using low perfusion temperature might be a useful investigation tools for the study of damaged brain function of suffered neonate animal models.