General anesthetics and neurotransmitter release

全身麻醉剂对脑电活动的作用可分为两种特征类型。第一种类型的特点是以剂量依赖性方式抑制网状神经元的自发放电。引起这种抑制的药物有巴比妥酸盐、氟烷和异氟烷。另一种类型的特点是在临床剂量下网状神经元放电增强。引起这种增强的麻醉剂是乙醚、氯胺酮和一氧化二氮。在中枢神经系统（CNS）中，神经递质分为两大类：兴奋性递质，如谷氨酸（GLU）、乙酰胆碱（Ach）和多巴胺（DA）；抑制性递质，如γ -氨基丁酸（GABA）和甘氨酸。为了为麻醉药不同的中枢神经系统作用提供神经化学基础，我们研究了不同类型的麻醉药与不同类型的神经递质释放的关系。采用微透析法研究戊巴比妥、异氟醚、氯胺酮和氧化亚氮对大鼠大脑皮层和纹状体多种神经递质释放的影响。戊巴比妥不影响GLU、GABA和甘氨酸的释放，但抑制纹状体乙酰胆碱的释放。异氟醚还能减少大脑皮层和纹状体中乙酰胆碱的释放。氯胺酮和氧化亚氮对纹状体乙酰胆碱释放没有影响。因此，戊巴比妥和异氟醚的抑制作用可能是通过抑制兴奋性递质乙酰胆碱的释放而产生的。我们研究了大鼠吸入氧化亚氮时脑单胺及其代谢物的变化。氧化亚氮增加了多巴胺代谢物3,4-二羟基苯基乙酸在大脑皮层和髓质的含量，但没有增加多巴胺的含量，表明多巴胺能神经元活性增强。氧化亚氮的致喜和催吐特性可能是多巴胺能系统激活的反映。少

Actions of general anesthetics on the brain electrical activities can be differentiated two characteristic types. The first type is characterized by the suppression of the spontaneous firing of the reticular neurons in dose dependent manner. Agents that induce this type of suppression are barbiturate, halothane, and isoflurane. The other type is characterized by the enhancement of the reticular neuronal firing in the clinical doses. The anesthetics that induce this enhancement are ether, ketamine, and nitrous oxide. In the central nervous system(CNS), neurotransmitters are separated into two general classes : excitatory transmitters, such as glutamate(GLU), acetylcholine(Ach), and dopamine(DA), and inhibitory ones, such as gamma-aminobutylic acid(GABA) and glycine. To provide a neurochemical basis for the different CNS actions of anesthetics, we investigated the relation of the different types of anesthetics and the release of the different classes of neurotransmitters.We studied the e … More ffects of pentobarbital, isoflurane, ketamine, and nitrous oxide on the release of various neurotransmitters at the cerebral cortex and the striatum using the microdialysis method in rats. Pentobarbital did not affect the release of GLU, GABA, and glycine, but suppressed the striatal Ach release. Isoflurane also decreased Ach release in the cerebral cortex and the striatum. Ketamine and nitrous oxide did not change the striatal Ach release. Thus, inhibitory action of pentobarbital and isoflurane might be produced by the attenuation of the release of excitatory transmitter, Ach. 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. The euphorigenic and emetic properties of nitrous oxide may be a reflection of the activation of dopaminergic systems. Less