Extracellular single-unit recordings of piriform cortex neurons in rats:: Influence of different types of anesthesia and characterization of neurons by pharmacological manipulation of serotonin receptors
Extracellular single-unit recordings of piriform cortex neurons in rats:: Influence of different types of anesthesia and characterization of neurons by pharmacological manipulation of serotonin receptors
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DOI：
10.1002/(sici)1097-4547(19990301)55:5
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发表时间：
1999-03-01
影响因子：
4.2
通讯作者：
Löscher, W
中科院分区：
文献类型：
--
作者：
Bloms-Funke, P;Gernert, M;Löscher, W
在癫痫研究中，梨状皮质（PC）在边缘系统点燃和其他类型的边缘系统癫痫发生（导致复杂的部分性癫痫发作）的发展和维持中的作用越来越受到关注。对点燃大鼠PC或杏仁核-PC切片制备物的神经生理学研究表明，点燃杏仁核诱导同侧PC突触效能的持久变化，包括自发放电和PC神经元对诱发爆发反应的敏感性增强。点燃过程中PC的这些持久的电生理变化似乎是由于，至少部分是由于γ-氨基丁酸（GABA）能中间神经元的功能受损。本研究的目的是开发一种麻醉方案，允许电生理单单位记录从抑制，推测GABA能PC在体内的中间神经元。除了记录自发活动的PC神经元，微离子电渗应用谷氨酸被用来激活沉默的神经元。由于明显的心血管抑制，用氯胺酮/甲苯噻嗪对大鼠进行麻醉不适合在PC中进行单单位记录。水合氯醛麻醉允许记录自发或谷氨酸驱动的单单位活动，所有动物中有40%相似。在所有手术准备均在麻醉下重复给予巴比妥酸盐美索比妥后，使用麻醉性阿片类芬太尼（加加拉明）进行记录时，获得了相似的百分比。为了避免重复应用美索比妥引起脑内蓄积，我们修改了麻醉方案，即在手术麻醉开始时仅注射一次美索比妥，然后注射短效麻醉剂丙泊酚，重复应用后不会蓄积。同样，在手术准备后，在芬太尼（加加拉明）下进行电生理记录。通过该程序，可以在PC的第II层或第III层中的所有大鼠中测量自发或谷氨酸驱动的单单位活动。根据动作电位的形状和频率，记录到两种类型的神经元。主要类型的PC神经元的放电特征与其他脑区的GABA能神经元相似，主要位于第III层，并且可以被5-羟色胺（2A）受体拮抗剂MDL 100，907抑制，表明这种类型的PC神经元代表抑制性的、推定的GABA能中间神经元。这种新的体内制备方法可能有助于点燃大鼠PC神经元的评价。(C)1999 Wiley-Liss，Inc.
In epilepsy research, there is a growing interest in the role of the piriform cortex (PC) in the development and maintenance of limbic kindling and other types of limbic epileptogenesis leading to complex partial seizures. Neurophysiological studies on PC or amygdala-PC slice preparations from kindled rats showed that kindling of the amygdala induces long-lasting changes in synaptic efficacy in the ipsilateral PC, including spontaneous discharges and enhanced susceptibility of PC neurons to evoked burst responses. These long-lasting electrophysiological changes in the PC during kindling appear to be due, at least in part, to impaired function of gamma-aminobutyric acid (GABA)ergic interneurons. The aim of the present study was to develop an anesthetic protocol allowing electrophysiological single-unit recordings from inhibitory, presumably GABAergic PC interneurons in vivo. In addition to recording of spontaneously active PC neurons, microiontophoretic application of glutamate was used to activate silent neurons. Anesthesia of rats with ketamine/xylazine was not suited for single-unit recordings in the PC because of marked cardiovascular depression. Anesthesia with chloral hydrate allowed recording of spontaneous or glutamate-driven single-unit activity in similar to 40% of all animals. A similar percentage was obtained when recordings were done with the narcotic opioid fentanyl (plus gallamine), after all surgical preparations were performed under anesthesia with repeated administration of the barbiturate methohexital. To avoid brain accumulation of methohexital by repeated applications, we modified the anesthetic protocol in that methohexital was only injected once for initiation of surgical anesthesia, followed by the short-acting anesthetic propofol which does not accumulate upon repeated application. Again, after surgical preparation, electrophysiological recordings were done under fentanyl (plus gallamine). By this procedure, spontaneous or glutamate-driven single-unit activity could be measured in all rats in either layer II or III of the PC. Based on shape and frequency of action potentials, two types of neurons mere recorded. The predominant type was similar in its firing characteristics to GABAergic neurons in other brain regions, was mainly located in layer III, and could be suppressed by the serotonin(2A) receptor antagonist MDL 100,907, suggesting that this type of PC neuron represents inhibitory, putative GABAergic interneurons. This new in vivo preparation may be useful for evaluation of PC neurons in kindled rats. (C) 1999 Wiley-Liss, Inc.