Action potentials reliably invade axonal arbors of rat neocortical neurons
Action potentials reliably invade axonal arbors of rat neocortical neurons
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DOI：
10.1073/pnas.170278697
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发表时间：
2000-08-15
影响因子：
11.1
通讯作者：
Svoboda, K
中科院分区：
文献类型：
--
作者：
Cox, CL;Denk, W;Svoboda, K
新皮质锥体神经元具有广泛的轴突分支，形成数千个突触。动作电位可以侵入这些乔木，引起钙内流，这是神经递质释放和突触后靶点兴奋所必需的。因此，轴突分支对动作电位侵袭的调控可能影响皮层神经网络兴奋的传播。为了测量动作电位侵入轴突的可靠性和程度，我们使用双光子激发激光扫描显微镜直接成像急性脑切片中2/3层锥体神经元单静脉曲张中动作电位介导的钙内流。我们的数据表明，在发育年龄（出生后10-24天）和温度（24℃-30℃）的范围内，单动作电位或动作电位爆发可靠地侵入轴突乔木。在动作电位启动之前的超极化电流步骤，先前观察到在培养制剂中产生动作电位传播失败的方案，在调节急性切片中动作电位的传播方面是无效的。我们的数据表明，动作电位可靠地侵入新皮层锥体神经元的轴突。因此，突触传递的失败一定起源于动作电位入侵的下游。我们还探讨了抑制突触前钙内流的调节剂的功能。与先前的研究一致，我们发现腺苷减少突触前终末动作电位介导的钙内流。在所有测试的末端都观察到这种减少，这表明某些调节系统在同一神经元的大多数末端都是均匀表达的。
Neocortical pyramidal neurons have extensive axonal arborizations that make thousands of synapses. Action potentials can invade these arbors and cause calcium influx that is required for neurotransmitter release and excitation of postsynaptic targets. Thus, the regulation of action potential invasion in axonal branches might shape the spread of excitation in cortical neural networks. To measure the reliability and extent of action potential invasion into axonal arbors, we have used two-photon excitation laser scanning microscopy to directly image action-potential-mediated calcium influx in single varicosities of layer 2/3 pyramidal neurons in acute brain slices. Our data show that single action potentials or bursts of action potentials reliably invade axonal arbors over a range of developmental ages (postnatal 10-24 days) and temperatures (24 degrees C-30 degrees C). Hyperpolarizing current steps preceding action potential initiation, protocols that had previously been observed to produce failures of action potential propagation in cultured preparations, were ineffective in modulating the spread of action potentials in acute slices. Our data shaw that action potentials reliably invade the axonal arbors of neocortical pyramidal neurons. Failures in synaptic transmission must therefore originate downstream of action potential invasion. We also explored the function of modulators that inhibit presynaptic calcium influx. Consistent with previous studies, we find that adenosine reduces action-potential-mediated calcium influx in presynaptic terminals. This reduction was observed in all terminals tested, suggesting that some modulatory systems are expressed homogeneously in most terminals of the same neuron.