Papanek P E, Wood C E, Fregly M J
Department of Physiology, College of Medicine, University of Florida, Gainesville 32610.
J Appl Physiol (1985). 1991 Jul;71(1):300-6. doi: 10.1152/jappl.1991.71.1.300.
Hypertension develops in rats exposed chronically to cold [6 +/- 2 degrees C (SE)] and includes both an elevation of mean arterial pressure and cardiac hypertrophy. Previous studies suggest that cold-exposed animals, at least initially, have a large sustained increase in the activity of their sympathetic nervous system, suggesting a failure of the baroreceptor system to provide sufficient negative feedback to the central nervous system. The present study was designed to investigate whether alterations in the activity of the sympathetic nervous system, including the baroreceptor reflex, occur during exposure to cold and whether they contribute to cold-induced hypertension. Twenty male rats were prepared with indwelling catheters in the femoral artery and vein. Ten of the rats were exposed to cold (6 +/- 2 degrees C) chronically, while the remaining 10 were kept at 26 +/- 2 degrees C. Withdrawal of arterial blood samples (less than 5 ml/kg), measurement of direct arterial pressures, and measurement of baroreflex function were carried out at 0800 h at intervals throughout the experiment. Norepinephrine and epinephrine concentrations in plasma were also determined at intervals throughout the experiment. Systolic, diastolic, and mean blood pressures of cold-exposed rats were increased to levels significantly above those of controls. The sensitivity of the baroreflex (delta heart period/delta mean arterial pressure) was decreased in the cold-treated group. The concentration of norepinephrine in plasma increased after 24 h of exposure to cold and remained elevated throughout the experiment, whereas the concentration of epinephrine in plasma increased initially but returned to control levels after 19 days of exposure to cold.(ABSTRACT TRUNCATED AT 250 WORDS)
长期暴露在寒冷环境（6±2摄氏度，标准误）中的大鼠会出现高血压，表现为平均动脉压升高和心脏肥大。先前的研究表明，至少在最初阶段，暴露在寒冷环境中的动物交感神经系统活动会持续大幅增加，这表明压力感受器系统未能向中枢神经系统提供足够的负反馈。本研究旨在调查在暴露于寒冷环境期间，包括压力感受器反射在内的交感神经系统活动是否发生改变，以及这些改变是否会导致寒冷诱导的高血压。20只雄性大鼠在股动脉和静脉中留置导管。其中10只大鼠长期暴露于寒冷环境（6±2摄氏度），其余10只保持在26±2摄氏度。在整个实验过程中，于08:00每隔一段时间采集动脉血样本（小于5毫升/千克），测量直接动脉压，并测量压力反射功能。在整个实验过程中还会定期测定血浆中的去甲肾上腺素和肾上腺素浓度。暴露于寒冷环境的大鼠的收缩压、舒张压和平均血压升高至显著高于对照组的水平。寒冷处理组的压力反射敏感性（心率变化/平均动脉压变化）降低。暴露于寒冷环境24小时后，血浆中去甲肾上腺素浓度升高，并在整个实验过程中保持升高，而血浆中肾上腺素浓度最初升高，但在暴露于寒冷环境19天后恢复到对照水平。（摘要截断于250字）
