[Alterations in local cerebral glucose utilization during various anesthesia--the effect of urethane and a review]

Anesthetic is thought to depress the energy metabolism or oxygen consumption of the brain as a whole. It has been clear, however, that anesthetic agent may either decrease or increase local metabolic rate of the brain since [14C] 2-deoxyglucose 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 measured local cerebral glucose utilization by means of [14C] 2-deoxyglucose method in 87 brain structures of albino rats (about 300 g) under urethane anesthesia, 1 g/kg (n = 5), and conscious state (n = 6). When the whole brain metabolism was computed as a weighted average with the acid of the computerized image-processing system, there was 33% reduction in glucose utilization of the brain as a whole in the rats under urethane anesthesia. Urethane decreased the local rate of glucose metabolism, but the metabolic effect was not homogeneous throughout the brain. The neural structures in which no metabolic depression was observed were entorhinal cortex, many nuclei in hypothalamus, medial habenula-interpeduncular nucleus, nucleus tractus solitarius, and some white matters. The selective metabolic sparing in the habenula-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 utilization. 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.(ABSTRACT TRUNCATED AT 250 WORDS)