CALCIUM SPIKES AND CALCIUM PLATEAUS EVOKED BY DIFFERENTIAL POLARIZATION IN DENDRITES OF TURTLE MONONEURONES IN-VITRO
CALCIUM SPIKES AND CALCIUM PLATEAUS EVOKED BY DIFFERENTIAL POLARIZATION IN DENDRITES OF TURTLE MONONEURONES IN-VITRO
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DOI：
10.1113/jphysiol.1993.sp019769
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发表时间：
1993-08-01
影响因子：
5.5
通讯作者：
KIEHN, O
中科院分区：
文献类型：
--
作者：
HOUNSGAARD, J;KIEHN, O
1.采用微分极化法研究了乌龟运动神经元树突对钙峰和钙平台的支持能力.电场是通过使电流通过两个平板电极之间的海龟脊髓的横向切片来产生的。电场产生的线性细胞外电压梯度表明组织是欧姆性的、非线性的.运动神经元胞体的跨膜电位以细胞内和细胞外微电极之间的电压差来测量.在正常介质中，外加电场可诱导运动神经元的突触活动和内在极化。突触活性被河豚毒素（TTX，1 μ m）抑制。在TTX和四乙基铵（TEA，1-5毫米）的存在下，施加的领域诱发多组分钙峰在两个领域的胞体超极化和胞体去极化方向。Ca ~（2+）峰的不同组分具有离散性和加性。高振幅成分有较高的阈值和更快的时间过程，其次是更大的后超极化，比低振幅成分。场诱发再生反应的频率对躯体偏置电流相对不敏感.在体细胞去极化和体细胞超极化方向上，差极化均能诱发apamin促进的TTX抗性Ca 2+介导的平台电位.结果表明，在龟脊髓运动神经元树突中存在钙通道，钙通道可引起钙峰和钙平台。
1. The ability of dendrites in turtle motoneurones to support calcium spikes and calcium plateaux was investigated using differential polarization by applied electric fields.2. Electric fields were generated by passing current through transverse slices of the turtle spinal cord between two plate electrodes. The linear extracellular voltage gradient generated by the field implied that the tissue was ohmic and homogeneous.3. The transmembrane potential at the cell body of motoneurones was measured as the voltage difference between an intracellular and an extracellular microelectrode.4. In normal medium an applied field induced synaptic activity as well as intrinsic polarization of motoneurones. Synaptic activity was suppressed by tetrodotoxin (TTX, 1 mum).5. In the presence of TTX and tetraethylammonium (TEA, 1-5 mm), applied fields evoked multicomponent Ca2+ spikes in both the soma-hyperpolarizing and soma-depolarizing direction of the field. The different components of Ca2+ spikes were discrete and additive. High amplitude components had higher threshold and faster time course and were followed by larger after-hyperpolarizations, than low amplitude components. The frequency of field-evoked regenerative responses was relatively insensitive to somatic bias current.6. TTX-resistant Ca2+-mediated plateau potentials promoted by apamin were evoked by differential polarization in both the soma-depolarizing and somahyperpolarizing direction.7. It is concluded that Ca2+ channels responsible for Ca2+ spikes and Ca2+ plateaux are present in dendrites of spinal motoneurones of the turtle.