Mechanisms of direct actions of perioperative drugs on splachnic resistance vessels

异氟醚和七氟醚是目前在日本普遍使用的挥发性麻醉剂，其临床相关浓度显著影响离体肠系膜抵抗动脉对去甲肾上腺素（一种交感神经递质）的收缩反应。这些麻醉药对NE收缩反应的作用包括内皮依赖性血管收缩和内皮非依赖性血管扩张成分。在内皮存在的情况下，前者优于后者，增强了NE的反应，而在内皮缺失的情况下，只有后者出现，抑制了NE的反应。一氧化氮、内皮衍生的超极化因子、环氧合酶产物、脂氧合酶产物、内皮素-1、血管紧张素II或血清素不参与它们的血管收缩作用。异氟醚可能刺激内皮细胞释放超氧阴离子，从而增强NE反应。七氟醚似乎通过降低细胞内Ca^<2+>浓度（[Ca^<2+>]i）和抑制肌丝Ca^<2+>敏感性来抑制血管平滑肌收缩。[Ca^<2+>]i的还原作用主要是通过抑制电压门控的Ca^<2+>内流引起的，而其对肌丝Ca^<2+>敏感性的抑制作用似乎需要完整的细胞膜。四种挥发性麻醉剂氟烷、异呋喃、安氟醚和七氟醚对肠系膜阻力动脉平滑肌细胞内钙储存的各种功能有不同的影响，如Ca^<2+>的储藏量、Ca^<2+>的摄取或Ca^<2+>-的释放机制。这些麻醉药可能通过对细胞内钙储存的不同影响而显著影响血管张力或肠系膜抵抗动脉的反应性。氯胺酮，一种静脉麻醉药，对孤立的肠系膜抵抗动脉的作用机制也进行了调查和报道。目前正在研究各种卤代挥发性麻醉药对分离的肝和肾动脉的影响。少

Isoflurane and sevoflurane, volatile anesthetics now commonly used in Japan, at clinically relevant concentrations significantly influence contractile response to norepinephrine (NE), a sympathetic neurotransmitter, in isolated mesenteric resistance arteries. The action of these anesthetics on contractile response to NE consists of endothelium-dependent vasoconstricting and endothelium-independent vasodilating components. In the presence of endothelium, the former predominates over the latter, enhancing the NE response, while in the absence of endothelium, only the latter emerges, inhibiting the NE response. Nitric oxide, endothelium-derived hyperpolarizing factor, cyclooxygenase products, lipoxygenase products, endothelin-1, angiotensin II, or serotonin are not involved in their vasoconstricting action. Isoflurane may stimulate release of superoxide anions from endothelial cells, thereby enhancing the NE response.Sevoflurane appears to inhibit vascular smooth muscle contraction by bot … More h reducing the intracellular Ca^<2+> concentration ([Ca^<2+>]i) and inhibiting myofilament Ca^<2+> sensitivity. The [Ca^<2+>]i-reducing effect is mainly caused by inhibition of voltage-gated Ca^<2+> influx, while its inhibitory action on myofilament Ca^<2+> sensitivity seems to require an intact cell membrane. Four volatile anesthetics halothane, isolfurane, enflurane and sevoflurane have differential effects on various functions of intracellular calcium stores of mesenteric resistance arterial smooth muscle cells such as the amount of stored Ca^<2+>, Ca^<2+> uptake, or Ca^<2+>-releasing mechanisms. These anesthetics may significantly influence vascular tone or reactivity of mesenteric resistance arteries through their various effects on the intracellular calcium stores.Mechanisms of the action of ketamine, an intravenous anesthetic, on isolated mesenteric resistance arteries were also investigated and reported. The effects of various halogenated volatile anesthetics on isolated hepatic and renal arteries are currently under investigation. Less