Synaptic inhibition by volatile ansethetics

挥发性麻醉剂的突触抑制

• 批准号: 6464774
• 负责人: LING-GANG WU
• 金额: $ 22.53万
• 依托单位: WASHINGTON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-04-01 至 2006-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6464774
• 关键词: action potentials; anesthetics; auditory pathways; biophysics; brain stem; calcium channel; calcium flux; calcium indicator; evoked potentials; general anesthesia; glutamates; halothane; inhalation anesthesia; isoflurane; laboratory rat; neural transmission; neurotransmitter transport; photolysis; potassium channel; preoptic areas; sectioning; sodium channel; synapses; tissue /cell preparation; voltage /patch clamp

Volatile anesthetics achieve their anesthetic effects partly by depressing excitatory glutamatergic synaptic transmission. Evidence suggests that depression of glutamatergic synaptic transmission is caused by inhibition of transmitter release. However, the cellular and molecular mechanisms underlying inhibition of transmitter release remain unclear. Based on our preliminary results, I hypothesize that volatile anesthetics depress glutamatergic synaptic transmission by reducing the presynaptic Ca2+ influx by two mechanisms: 1) inhibition of presynaptic Na+ channels, which decreases the action potential amplitude and thus the action potential-evoked Ca2+ influx, and 2) inhibition of presynaptic Ca2+ channels. We will test this hypothesis at a glutamatergic synapse in the medial nucleus of the trapezoid body in rat brainstem slices. This synapse offers a significant advantage over other synapses, because it has a large nerve terminal that allows for direct recordings of presynaptic action potentials, Na+, K+ and Ca2+ currents and fluorescence recordings of Ca2+ influx. These presynaptic recordings can be performed simultaneously with recordings of the postsynaptic excitatory current (EPSC) at the same synapse, which allows us to quantitatively evaluate the involvement of each presynaptic ion channel type in controlling action potential-evoked transmitter release. With these techniques, we will study the action of three commonly used volatile anesthetics, isoflurane, halothane and sevoflurane at clinically relevant concentrations. We will characterize the effects of these anesthetics on presynaptic Na+, K+ and Ca2+ channels and the contribution of each of these effects to depression of the EPSC. In addition, we will investigate whether these anesthetics also inhibit the EPSC by a mechanism independent of modulation of ion channels, i.e., direct inhibition of the release machinery. By revealing mechanisms underlying volatile anesthetic-induced depression of glutamate release, the proposed work will significantly contribute to our understanding of the cellular and molecular mechanisms of general anesthesia, and may ultimately help to design better general anesthetics.

挥发性麻醉药部分通过抑制兴奋性谷氨酸能突触传播来部分地实现其麻醉作用。 有证据表明，谷氨酸能突触传播的抑郁是由释放发射器释放引起的。 然而，释放发射机抑制的基础机制和分子机制尚不清楚。根据我们的初步结果，我假设通过通过两种机制减少突触前Ca2+涌入来抑制谷氨酸氨基疗法的传播：1）抑制前Na+通道的抑制作用，从而降低了动作势势，从而降低了动作潜在的ca2+ CAC2+ CAC2+ ca2+ ca2+ ins 2）。 我们将在大鼠脑干切片中梯形体的内侧核中的谷氨酸能突触中检验该假设。该突触比其他突触具有显着的优势，因为它具有较大的神经末端，可直接记录突触前动作电位，Na+，K+和Ca2+电流以及Ca2+膨胀的荧光记录。 这些突触前的记录可以同时与同一突触下突触后兴奋剂（EPSC）的记录同时进行，这使我们能够定量评估每种突触前离子通道类型的参与，以控制动作电位诱发的发射器释放。 通过这些技术，我们将研究临床相关浓度下三种常用的挥发性麻醉药，异氟烷，氟烷和七氟烷的作用。 我们将表征这些麻醉剂对突触前Na+，K+和Ca2+通道的影响，以及这些影响对EPSC抑郁症的贡献。 此外，我们将研究这些麻醉剂是否还通过独立于离子通道的调节（即直接抑制释放机制）的机制抑制EPSC。 通过揭示挥发性麻醉引起的谷氨酸释放抑制的基础机制，提出的工作将显着有助于我们对全身麻醉的细胞和分子机制的理解，并最终有助于设计更好的全身麻醉药。