Shirey Michael J, Smith Jared B, Kudlik D'Anne E, Huo Bing-Xing, Greene Stephanie E, Drew Patrick J
Center for Neural Engineering, Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, Pennsylvania;
Center for Neural Engineering, Bioengineering Graduate Program, Pennsylvania State University, University Park, Pennsylvania; and.
J Neurophysiol. 2015 Jul;114(1):309-22. doi: 10.1152/jn.00046.2015. Epub 2015 May 13.
Changes in brain temperature can alter electrical properties of neurons and cause changes in behavior. However, it is not well understood how behaviors, like locomotion, or experimental manipulations, like anesthesia, alter brain temperature. We implanted thermocouples in sensorimotor cortex of mice to understand how cortical temperature was affected by locomotion, as well as by brief and prolonged anesthesia. Voluntary locomotion induced small (∼ 0.1 °C) but reliable increases in cortical temperature that could be described using a linear convolution model. In contrast, brief (90-s) exposure to isoflurane anesthesia depressed cortical temperature by ∼ 2 °C, which lasted for up to 30 min after the cessation of anesthesia. Cortical temperature decreases were not accompanied by a concomitant decrease in the γ-band local field potential power, multiunit firing rate, or locomotion behavior, which all returned to baseline within a few minutes after the cessation of anesthesia. In anesthetized animals where core body temperature was kept constant, cortical temperature was still > 1 °C lower than in the awake animal. Thermocouples implanted in the subcortex showed similar temperature changes under anesthesia, suggesting these responses occur throughout the brain. Two-photon microscopy of individual blood vessel dynamics following brief isoflurane exposure revealed a large increase in vessel diameter that ceased before the brain temperature significantly decreased, indicating cerebral heat loss was not due to increased cerebral blood vessel dilation. These data should be considered in experimental designs recording in anesthetized preparations, computational models relating temperature and neural activity, and awake-behaving methods that require brief anesthesia before experimental procedures.
脑温变化可改变神经元的电特性并导致行为改变。然而，人们对诸如运动等行为或诸如麻醉等实验操作如何改变脑温尚不清楚。我们将热电偶植入小鼠的感觉运动皮层，以了解皮层温度是如何受到运动以及短暂和长时间麻醉的影响。自主运动引起皮层温度小幅（约0.1℃）但可靠的升高，可用线性卷积模型来描述。相比之下，短暂（90秒）暴露于异氟烷麻醉使皮层温度降低约2℃，在麻醉停止后这种降低持续长达30分钟。皮层温度降低并未伴随γ波段局部场电位功率、多单位放电率或运动行为的相应降低，这些在麻醉停止后几分钟内均恢复到基线水平。在核心体温保持恒定的麻醉动物中，皮层温度仍比清醒动物低>1℃。植入皮层下的热电偶在麻醉下显示出类似的温度变化，表明这些反应在整个大脑中都会发生。对短暂异氟烷暴露后单个血管动力学的双光子显微镜观察显示，血管直径大幅增加，且在脑温显著降低之前就停止了，这表明脑热散失并非由于脑血管扩张增加所致。在记录麻醉制剂的实验设计、将温度与神经活动相关联的计算模型以及在实验程序前需要短暂麻醉的清醒行为方法中，应考虑这些数据。
