Rampil I J, Mason P, Singh H
Department of Anesthesia, University of California, San Francisco 94143-0648.
Anesthesiology. 1993 Apr;78(4):707-12. doi: 10.1097/00000542-199304000-00014.
The ability of general anesthetics to suppress somatomotor responses to surgical incision and other noxious stimuli is of particular clinical relevance. When the blockade is due to inhaled agents, this effect can be quantified as the minimum alveolar concentration (MAC), i.e., that concentration that blocks movement evoked by a noxious stimulus (ED50).
To identify the neural structures that subtend this somatomotor response, we anesthetized 14 rats with isoflurane in oxygen and performed bilateral parietal-temporal craniotomies. In each rat, MAC was repeatedly tested using tail-clamping and Dixon's up-down concentration technique. After determination of baseline MAC, seven rats underwent aspiration decerebration, after which MAC was repeatedly measured.
In the control group (N = 7), MAC (mean +/- SD) remained constant at 1.30 +/- 0.25% for more than 6 h. In the seven rats that underwent aspiration decerebration, baseline MAC was 1.26 +/- 0.14%. These seven rats with histologically validated precollicular decerebration demonstrated no change in MAC relative to control rats, as much as 11 h after decerebration (P = 0.14).
These findings suggest that the anesthetic-induced unresponsiveness to noxious stimuli measured by MAC testing does not depend on cortical or forebrain structures in the rat.
全身麻醉药抑制对手术切口及其他有害刺激的躯体运动反应的能力具有特殊的临床意义。当这种阻滞是由吸入性药物引起时，这种效应可以用最低肺泡浓度（MAC）来量化，即阻断有害刺激诱发运动的浓度（半数有效量）。
为了确定构成这种躯体运动反应的神经结构，我们用异氟烷和氧气麻醉了14只大鼠，并进行双侧顶颞开颅术。在每只大鼠中，使用夹尾法和狄克逊上下浓度技术反复测试MAC。在确定基线MAC后，7只大鼠接受了脑吸除术，之后反复测量MAC。
在对照组（N = 7）中，MAC（平均值±标准差）在6小时以上保持恒定，为1.30±0.25%。在接受脑吸除术的7只大鼠中，基线MAC为1.26±0.14%。这7只经组织学证实为视丘前脑吸除术的大鼠，在脑吸除术后长达11小时，MAC相对于对照大鼠没有变化（P = 0.14）。
这些发现表明，通过MAC测试测量的麻醉诱导的对有害刺激无反应性并不依赖于大鼠的皮质或前脑结构。
