Locomotor rhythm maintenance: electrical coupling among premotor excitatory interneurons in the brainstem and spinal cord of young Xenopus tadpoles.
Locomotor rhythm maintenance: electrical coupling among premotor excitatory interneurons in the brainstem and spinal cord of young Xenopus tadpoles.
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DOI：
10.1113/jphysiol.2008.166942
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发表时间：
2009-04-15
期刊：
影响因子：
--
通讯作者：
Soffe SR
中科院分区：
文献类型：
--
作者：
Li WC;Roberts A;Soffe SR
电耦合在节奏产生系统中是重要的。我们在一个简单的脊椎动物模型中研究了它在控制运动的电路中的作用，年轻的非洲爪哇蝌蚪，其中驱动和维持游泳的后脑和脊髓兴奋性下行中间神经元(DIN)已经被描述。使用同步配对记录，我们发现大多数DIN与其他DIN完全电耦合(DC耦合系数∼8.5%)。耦合表现为典型的低通滤波。我们没有发现其他游泳中枢模式生成器(CPG)中间神经元与DIN或彼此耦合的证据。DIN之间的电耦合电势似乎有助于它们在游泳时异常可靠地发射。为了研究电耦合在游泳中的作用，我们评估了缝隙连接阻滞剂(18-β-GA、甘草酮、氟芬酸和庚醇)在配对记录中的特异性。18-β-GA在40~60μm时产生大量偶联封闭(84%)，但对细胞特性影响不大。18-β-GA组的游泳次数显著缩短(∼为对照组的2%)。与此同时，DIN射击的可靠性从游泳周期的近100%下降到62%，扣球同步性减弱。由于DIN驱动CPG神经元的放电，对维持游泳至关重要，因此DIN活性的减弱可能是18-β-GA影响游泳的原因。我们的结论是，运动前网状脊髓和脊髓DIN之间的电耦合可能有助于维持游泳和活动的同步性。
Electrical coupling is important in rhythm generating systems. We examine its role in circuits controlling locomotion in a simple vertebrate model, the young Xenopus tadpole, where the hindbrain and spinal cord excitatory descending interneurons (dINs) that drive and maintain swimming have been characterised. Using simultaneous paired recordings, we show that most dINs are electrically coupled exclusively to other dINs (DC coupling coefficients ∼8.5%). The coupling shows typical low-pass filtering. We found no evidence that other swimming central pattern generator (CPG) interneurons are coupled to dINs or to each other. Electrical coupling potentials between dINs appear to contribute to their unusually reliable firing during swimming. To investigate the role of electrical coupling in swimming, we evaluated the specificity of gap junction blockers (18-β-GA, carbenoxolone, flufenamic acid and heptanol) in paired recordings. 18-β-GA at 40–60 μm produced substantial (84%) coupling block but few effects on cellular properties. Swimming episodes in 18-β-GA were significantly shortened (to ∼2% of control durations). At the same time, dIN firing reliability fell from nearly 100% to 62% of swimming cycles and spike synchronization weakened. Because dINs drive CPG neuron firing and are critical in maintaining swimming, the weakening of dIN activity could account for the effects of 18-β-GA on swimming. We conclude that electrical coupling among pre motor reticulospinal and spinal dINs, the excitatory interneurons that drive the swimming CPG in the hatchling Xenopus tadpole, may contribute to the maintenance of swimming as well as synchronization of activity.
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