ELECTROPHYSIOLOGICAL CHARACTERISTICS OF IMMUNOCHEMICALLY IDENTIFIED RAT OXYTOCIN AND VASOPRESSIN NEURONS IN-VITRO
ELECTROPHYSIOLOGICAL CHARACTERISTICS OF IMMUNOCHEMICALLY IDENTIFIED RAT OXYTOCIN AND VASOPRESSIN NEURONS IN-VITRO
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DOI：
10.1113/jphysiol.1994.sp020053
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发表时间：
1994-02-15
影响因子：
5.5
通讯作者：
TIAN, M
中科院分区：
文献类型：
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作者：
ARMSTRONG, WE;SMITH, BN;TIAN, M
1.从成年雄性大鼠下丘脑外植体制备的体外视上神经元进行细胞内记录。神经元注射生物素标记物，在39个标记的神经元中，免疫细胞化学鉴定19个含有催产素-神经垂体后叶素，20个含有加压素-神经垂体后叶素。加压素和催产素神经元在静息膜电位、输入电阻、膜时间常数、动作电位阈值高度、动作电位半幅宽度和尖峰超极化后电位振幅方面没有差异。这两种细胞类型表现出短暂的，诱发的尖峰列车（6-8尖峰），但增宽的程度稍大的加压素神经元。当超极化电位低于-75 mV时，除一个神经元外，其余神经元对去极化脉冲均表现出短暂的外向整流，延迟了第一个峰电位的出现.这两种细胞类型表现出一个长的后超极化电位（AHP）的简短的尖峰列车引起的方波脉冲或使用5毫秒脉冲的列车。有没有显着差异的大小的层次分析法诱发的9个尖峰，或在其衰减的时间常数的细胞类型。由180 ms脉冲引起的最大AHP平均由12到13个尖峰引起，并且对于两种细胞类型，该最大AHP的大小及其衰减时间常数都没有不同。在大多数催产素和加压素神经元的层次分析法，并伴随着尖峰频率适应，显着减少蜂毒蜂毒和d-筒箭毒碱，已知的钙离子介导的K+传导阻滞剂。然而，两种细胞类型的少数神经元对两种药物都具有相对抗性。在未经处理的神经元，55%的加压素神经元和32%的催产素神经元表现出去极化后电位（DAP）后，个人的尖峰，或更常见的是，短暂的列车后，与电流脉冲诱发的尖峰。对于具有DAP的每个神经元，如果膜电位充分去极化使得DAP达到尖峰阈值，则可以诱发尖峰的爆发。在五个加压素神经元中的四个中，DAP仅在药物阻断AHP后才变得明显，而在六个催产素神经元中，没有发现这种掩蔽。神经元的放电模式进行了检查，在休息和改变后的膜电位与连续电流注入。没有识别模式与任何一种细胞类型严格相关，大量的神经元在休息时是沉默的。虽然更多的加压素比催产素神经元表现出相位爆发，两个6催产素神经元与DAP通过相位爆发后，操纵膜电位。许多后叶加压素和催产素神经元可以长时间持续放电，在少数情况下，通过在其他静止神经元中唤起DAP来引起持续的活动。在较慢的放电过程中，两种细胞类型中的棘波聚集都很明显，即使是在没有DAP的神经元中也是如此。7。雄性大鼠的催产素和加压素神经元在体外实验中具有许多相似的电生理特征。虽然最大的差异是具有DAP的神经元的百分比，但这种电位是不稳定的，并且不是细胞类型的标志。这两种细胞类型在体外的相似性表明，在体内突触输入在确定激素释放增加期间显示的独特放电模式中发挥更大的作用。
1. Intracellular recordings were made from supraoptic neurones in vitro from hypothalamic explants prepared from adult male rats. Neurones were injected with biotinylated markers, and of thirty-nine labelled neurones, nineteen were identified immunocytochemically as containing oxytocin-neurophysin and twenty as containing vasopressin-neurophysin.2. Vasopressin and oxytocin neurones did not differ in their resting membrane potential, input resistance, membrane time constant, action potential height from threshold, action potential width at half-amplitude, and spike hyperpolarizing after-potential amplitude. Both cell types exhibited spike broadening during brief, evoked spike trains (6-8 spikes), but the degree of broadening was slightly greater for vasopressin neurones. When hyperpolarized below -75 mV, all but one neurone exhibited a transient out-ward rectification to depolarizing pulses, which delayed the occurrence of the first spike.3. Both cell types exhibited a long after-hyperpolarizing potential (AHP) following brief spike trains evoked either with a square wave pulse or using 5 ms pulses in a train. There were no significant differences between cell types in the size of the AHP evoked with nine spikes, or in the time constant of its decay. The maximal AHP evoked by a 180 ms pulse was elicited by an average of twelve to thirteen spikes, and neither the size of this maximal AHP nor its time constant of decay were different for the two cell types.4. In most oxytocin and vasopressin neurones the AHP, and concomitantly spike frequency adaptation, were markedly reduced by the bee venom apamin and by d-tubocurarine, known blockers of a Ca2+-mediated K+ conductance. However, a minority of neurones, of both cell types, were relatively resistant to both agents.5. In untreated neurones, 55% of vasopressin neurones and 32% of oxytocin neurones exhibited a depolarizing after-potential (DAP) after individual spikes or, more commonly, after brief trains of spikes evoked with current pulses. For each neurone with a DAP, bursts of spikes could be evoked if the membrane potential was sufficiently depolarized such that the DAP reached spike threshold. In four out of five vasopressin neurones a DAP became evident only after pharmacological blockade of the AHP, whereas in six oxytocin neurones tested no such masking was found.6. The firing patterns of neurones were examined at rest and after varying the membrane potential with continuous current injection. No identifying pattern was strictly associated with either cell type, and a substantial number of neurones were silent at rest. Although more vasopressin than oxytocin neurones exhibited phasic bursting, two of six oxytocin neurones with a DAP adopted phasic bursting after manipulating the membrane potential. Many vasopressin and oxytocin neurones could fire continuously for long periods, and in a few cases continuous activity was elicited by evoking a DAP in an otherwise quiescent neurone. During slower firing, spike clustering was evident in both cell types, even in neurones without a DAP.7. Oxytocin and vasopressin neurones in male rats share many electrophysiological features which are quantitatively and qualitatively similar in vitro. Although the largest difference noted was in the percentage of neurones with a DAP, this potential is labile and is not a signature for a cell type. The similarity of these two cell types in vitro suggests a greater role for synaptic inputs in vivo in determining the distinctive firing patterns displayed during increased hormone release.