麻酔薬による局所脳グルコース代謝率にみられる影響—ウレタン麻酔および他の麻酔薬について

ALTERATIONS IN LOCAL CEREBRAL GLUCOSE UTILIZATION DURING VARIOUS ANESTHESIA:THE EFFECT OF URETHANE AND A REVIEW

　抄録　麻酔薬は全脳エネルギー代謝あるいは酸素消費率を低下させると一般に考えられている。近年麻酔薬の神経活動に及ぼす影響の多様性が注目されてきているが，各種麻酔薬の神経活動，代謝活動に及ぼす変化を理解することは重要である。神経生理学的実験で広く用いられているurethane （1g／kg,ip）のラット局所脳グルコース代謝率を［¹⁴C］2—deoxyglucose法により脳内87部位で測定した。対照覚醒群（n＝6）に比較し，麻酔群（n＝5）の全脳グルコース代謝率は33％の低下が見られ，脳内各部位においても約20ないし50％の範囲で代謝率を低下させたが，その程度は均一ではなく，視床下部ではurethaneによる影響をほとんど受けず，habenulo-interpeduncular systemにおけるselective metabolic sparingは本剤の局所脳代謝率に及ぼす作用の1つの特徴であるといえる。さらに本稿では，種々の麻酔薬—barbiturate,chloralose,chlo—ral hydrate,enflurane,ketamine，笑気，halothane—の局所脳グルコース代謝率に及ぼす変化について通覧し，各種麻酔薬の使用が局所脳代謝率に関する実験結果に如何なる影響を及ぼすかについても若干の文献的考察を加えた。

Anesthetic is thought to depress the energy metabolism or oxygen consumption of the brain as a whole. It has been clear, however, that anesthe-tic agent may either decrease or increase local metabolic rate of the brain since [¹⁴C] 2-deoxy-glucose method made one possible to measure local cerebral glucose utilization. In this paper, the authors report the effect of urethane anesthesia on the local cerebral glucose utilization. We mea-sured local cerebral glucose utilization by means of [¹⁴C] 2-deoxyglucose method in 87 brain struc-tures of albino rats (about 300g) under urethaneanesthesia, 1g/kg (n=5), and conscious state (n=6). When the whole brain metabolism was computed as a weighted average with the aid of the compu-terized image-processing system, there was 33% redution in glucose utilization of the brain as a whole in the rats under urethane anesthesia. Urethane decreased the local rate of glucose meta-bolism, but the metabolic effect was not homoge-neous throughout the brain. The neural structures in which no metabolic depression was observed were entorhinal cortex, many nuclei in hypotha-lamus, medial habenula-interpeduncular nucleus, nucleus tractus solitarius, and some white matters. The selective metabolic sparing in the habenulo-interpeduncular system was also reported to be observed during chloral hydrate and enflurane anesthesia. However, the mechanism involved in the phenomenon remains unclear. In the discussion, we discussed the differential effects of various anesthetics of the local cerebral glucose utiliza-tion. We reviewed the literatures on the effects of various anesthetics; barbiturate, chloralose, chloral hydrate, enflurane, ketamine, nitrous oxide and halothane on the local rate of metabolism of the brain. We also discuss that the use of anesthe-tics may modify the results of the physiological and pharmacological experiments.

This work was supported by N. I. H. visiting program (M. I. and M. M. ).