The nuerochemical basis of postoprative nausea and vomiting

麻醉和手术后最常见和最令人痛苦的症状之一是呕吐问题。术后恶心呕吐(PONV)在使用某些麻醉剂(如氧化亚氮)时比使用其他麻醉剂时更常见。几种刺激被称为呕吐的化学感受器触发区(CTZ)的最后区域的细胞检测到，该区域反过来激活呕吐中心。CTZ富含多巴胺、5-羟色胺和乙酰胆碱(ACh)受体。麻醉药对大脑具有普遍的药理作用，PONV可能是这种作用在呕吐反射通路上的表现。为了给PONV的发病提供神经化学基础，我们研究了麻醉药对CTZ内存在受体的神经递质释放的影响。我们研究了大鼠吸入一氧化二氮时脑单胺类物质及其代谢产物的变化。一氧化二氮可增加大脑皮层和延髓中多巴胺的代谢产物3，4-二羟基苯乙酸的含量，但不增加多巴胺的含量，这表明多巴胺能神经元的活动增强。采用微透析法研究了一氧化二氮、异氟醚和七氟烷对大鼠大脑皮层和纹状体ACh释放的影响。一氧化二氮可增加大脑皮层ACh的释放，而异氟醚和七氟醚则使其减少。一氧化二氮的排出特性可能反映了多巴胺和胆碱能系统的激活。

One of the most common and distressing symptoms which follow anesthesia and surgery is emetic problem. Postoperative nausea and vomiting (PONV) following same procedure occurs more frequently with some anesthetic agents, such as anitrous oxide, than with others. Several stimuli are detected by cells of the area postrema, termed the chemoreceptor trigger zone (CTZ) for emesis, which in turn activate the vomiting center. The CTZ is rich in dopamine, serotonin, acetylcholine (ACh) receptors. Anesthetics have general pharmacological effects on the brain and PONV may be an expression of such effects on the emetic reflex pathways. To provide a neurochemical basis of PONV,we investigated the effects of the anesthetics on the release of the neurotransmitters whose receptors exist in the CTZ.We studied the changes of brain monoamines and their metabolites during nitrous oxide inhalation in rats. Nitrous oxide increased the content of 3,4-dihydroxyphenylacetic acid, the metabolite of dopamine, but not dopamine, in the cerebral cortex and the medulla, which indicated the enhancement of dopaminergic neuronal activities. We studied the effects of nitrous oxide, isoflurane, and sevoflurane on the release of ACh at the cerebral cortex and the striatum using the microdialysis method in rats. Nitrous oxide increase the release of ACh in the cerebral cortex, whereas isoflurane and sevoflurane decreased it.The emetic properties of nitrous oxide may be a reflection of the activation of dopaminergic and cholinergic systems.