Conditioned dendritic oscillators in a lobster mechanoreceptor neurone
Conditioned dendritic oscillators in a lobster mechanoreceptor neurone
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DOI：
10.1113/jphysiol.1997.sp021918
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发表时间：
1997-02-15
影响因子：
5.5
通讯作者：
Moulins, M
中科院分区：
文献类型：
--
作者：
Combes, D;Simmers, J;Moulins, M
1.采用离体龙虾胃神经系统标本进行细胞内和细胞外记录，研究胃前感受器（AGR）的起搏样活动的性质和起源.虽然AGR是已知的自激活，我们在这里报告，在20%的我们的制剂，而不是自生紧张性放电，受体自发地发射离散的爆发，包括3至10个动作电位和重复的周期频率为0.5-2.5 Hz的机械刺激的情况下。体细胞内记录显示，这种节律性爆发是由膜电位的缓慢振荡驱动的，其频率是电压敏感的，并取决于施加到AGR受体末端的拉伸水平。AGR的自动爆发起源于感觉树突本身的内源性振荡机制，因为（i）在稳定的重复放电和爆发期间，躯体和轴突冲动总是先于1：1通过树突动作电位，（ii）超极化AGR细胞体以阻止轴突冲动的触发，显示持续源自两个外周树突的减弱的体细胞尖峰，（iii）爆发放电的时机可以通过短暂的电刺激进行相位重置任一个树突，和（iv）从GM 1肌肉和口胃神经系统物理分离后，AGR树突继续表达自发爆发.虽然一个给定的AGR在体外可以自发地从树突状爆发到紧张性放电，反之亦然，外源性应用微摩尔（或更少）浓度的神经肽F1（TNRNFLRFamide）的树突状细胞膜可以快速和可逆地切换受体放电模式从重复放电到爆发模式。AGR的体细胞和轴突膜暴露于F1没有影响，其他神经活性物质如5-羟色胺、章鱼胺和proctolin的应用也是如此。我们的结论是，作为许多振荡神经元的中枢神经系统，这种外周感觉神经元的内在活动模式可能会动态地赋予外部调制的影响，大概是根据计算的需求。此外，AGR作为内源性爆发的能力赋予了相当大的综合复杂性，因为在这种活动模式中，感觉编码不仅通过正在进行的树突爆发的频率调制发生，而且还通过个体爆发的持续时间及其固有的尖峰频率的变化发生。
1. Intra- and extracellular recordings were made from in vitro preparations of the lobster (Homarus gammarus) stomatogastric nervous system to study the nature and origin of pacemaker-like activity in a primary mechanoreceptor neurone, the anterior gastric receptor (AGR), whose two bilateral stretch sensitive dendrites ramify in the tendon of powerstroke muscle GM1 of the gastric mill system.2. Although the AGR is known to be autoactive, we report here that in 20% of our preparations, rather than autogenic tonic discharge, the receptor fired spontaneously in discrete bursts comprising three to ten action potentials and repeating at cycle frequencies of 0.5-2.5 Hz in the absence of mechanical stimulation. Intrasomatic recordings revealed that such rhythmic bursting was driven by slow oscillations in membrane potential, the frequency of which was voltage sensitive and dependent upon the level of stretch applied to the receptor terminals of the AGR.3. Autoactive bursting of the AGR originated from an endogenous oscillatory mechanism in the sensory dendrites themselves, since (i) during both steady: repetitive firing and bursting, somatic and axonal impulses were always preceded 1:1 by dendritic action potentials, (ii) hyperpolarizing the AGR cell body to block triggering of axonal impulses revealed attenuated somatic spikes that continued to originate from the two peripheral dendrites, (iii) the timing of burst firing could be phase reset by brief electrical stimulation of either dendrite, and (iv) spontaneous bursting continued to be expressed by an AGR dendrite after physical isolation from the GM1 muscle and the stomatogastric nervous system.4. Although a given AGR in, vitro could switch spontaneously from dendritic bursting to tonic firing and vice versa, exogenous application of micromolar (or less) concentrations of the neuropeptide F1 (TNRNFLRFamide) to the dendritic membrane could rapidly and reversibly switch the receptor firing pattern from repetitive firing to the bursting mode. Exposure of the somatic and axonal membrane of the AGR to F1 was without effect, as were applications of other neuroactive substances such as serotonin, octopamine and proctolin.5. We conclude that, as for many oscillatory neurones of the central nervous system, the intrinsic activity pattern of this peripheral sensory neurone may be dynamically conferred by extrinsic modulatory influences, presumably according to computational demands. Moreover, the ability of the AGR to behave as an endogenous burster imparts considerable integrative complexity since, in this activity mode, sensory coding not only occurs through the frequency modulation of on-going dendritic bursts but also via changes in the duration of individual bursts and their inherent spike frequencies.