脑血流的电复律阈值高于除极，在大鼠中，缺血性低温会降低这一阈值。

Cerebral Blood Flow Threshold Is Higher for Membrane Repolarization Than for Depolarization and Is Lowered by Intraischemic Hypothermia in Rats.

机构信息

1Department of Anesthesiology, Okayama University Medical School, Okayama City, Okayama, Japan. 2Department of Anesthesiology and Intensive Care Medicine, Kawasaki Medical School, Kurashiki, Okayama, Japan.

出版信息

Crit Care Med. 2015 Sep;43(9):e350-5. doi: 10.1097/CCM.0000000000001095.

DOI:10.1097/CCM.0000000000001095

PMID:25978336

Abstract

OBJECTIVES

To evaluate the cerebral blood flow thresholds for membrane depolarization and repolarization and the effect of brain hypothermia on the cerebral blood flow threshold for membrane repolarization.

DESIGN

Prospective animal study.

SETTING

Experimental laboratory in a university hospital.

SUBJECTS

Male Sprague-Dawley rats (n = 40).

INTERVENTIONS

Cerebral blood flow and membrane depolarization and repolarization in the cerebral cortex were simultaneously monitored by laser Doppler and extracellular potential, respectively. Following bilateral occlusion of the common carotid arteries, cerebral blood flow was decreased by draining blood at a rate of 2.5% of the control level/min until membrane depolarization was initiated. At 5 and 10 minutes (Normothermia 5 and Normothermia 10 groups, respectively) after depolarization onset, cerebral blood flow was restored at the same rate until membrane repolarization was observed. In some animals, intraischemic brain hypothermia targeting 31°C was initiated immediately after the onset of depolarization (Hypothermia 5 and Hypothermia 10 groups).

MEASUREMENTS AND MAIN RESULTS

The cerebral blood flow threshold for repolarization (46.5% ± 12%) was significantly higher than that for depolarization (18.9% ± 4.8%; p < 0.01) in the Normothermia 5 group and was further increased to 61.5% ± 14% (p < 0.01) in the Normothermia 10 group. With initiation of hypothermia, the cerebral blood flow threshold for membrane repolarization was suppressed to 33.8% ± 10% in the Hypothermia 5 group (p < 0.01 vs Normothermia 5 group) and was unaltered by prolongation of ischemia (Hypothermia 10 group; 36.6% ± 6%).

CONCLUSIONS

Cerebral blood flow thresholds were significantly higher for repolarization than for depolarization and were further increased by prolonged ischemia. Intraischemic brain hypothermia decreased the repolarization threshold and abrogated the increase in the repolarization threshold caused by prolonged ischemia.

摘要

目的

评估细胞膜去极化和复极化的脑血流阈值，以及脑低温对细胞膜复极化脑血流阈值的影响。

设计

前瞻性动物研究。

地点

大学医院的实验实验室。

对象

雄性 Sprague-Dawley 大鼠（n = 40）。

干预措施

通过激光多普勒和细胞外电位分别同时监测大脑皮层的脑血流和细胞膜去极化和复极化。在双侧颈总动脉闭塞后，以每分钟控制水平的 2.5%的速度排出血液，使脑血流减少，直至引发膜去极化。在去极化开始后 5 分钟（常温 5 分钟组）和 10 分钟（常温 10 分钟组），以相同的速度恢复脑血流，直至观察到膜复极化。在一些动物中，在去极化开始后立即启动缺血性脑低温，目标温度为 31°C（低温 5 分钟组和低温 10 分钟组）。

测量和主要结果

常温 5 分钟组的复极化脑血流阈值（46.5%±12%）明显高于去极化脑血流阈值（18.9%±4.8%；p<0.01），在常温 10 分钟组进一步升高至 61.5%±14%（p<0.01）。低温开始后，低温 5 分钟组的膜复极化脑血流阈值被抑制至 33.8%±10%（p<0.01 与常温 5 分钟组相比），并通过延长缺血时间而未改变（低温 10 分钟组；36.6%±6%）。