Weak action potential backpropagation is associated with high-frequency axonal firing capability in principal neurons of the gerbil medial superior olive
Weak action potential backpropagation is associated with high-frequency axonal firing capability in principal neurons of the gerbil medial superior olive
复制标题
DOI：
10.1113/jphysiol.2007.136366
复制
发表时间：
2007-09-01
影响因子：
5.5
通讯作者：
Golding, Nace L.
中科院分区：
文献类型：
--
作者：
Scott, Luisa L.;Hage, Travis A.;Golding, Nace L.
内侧上橄榄（MSO）主神经元通过调节动作电位放电速率传递方位声定位信号。先前的体外细胞内研究表明，在MSO神经元的胞体中，动作电位出现高度衰减，可能反映了特殊的动作电位起始和/或物理上遥远的产生部位。为了更直接地检查这一点，我们对沙鼠脑干切片的MSO主神经元进行了双膜片钳记录。利用体细胞和树突全细胞记录，我们发现，体细胞的梯度动作电位对兴奋上升的速率高度敏感，并且在反向传播到树突（长度常数，76 μ m）的过程中经历了强烈的衰减，特别是在强树突兴奋期间。使用成对的体细胞全细胞和轴突松散斑记录，我们发现轴突在距离bb0 ~ 25 μ m处记录的动作电位是全或无，即使动作电位在体细胞出现梯度，振幅也是均匀的。这个近端区域对应于轴突髓鞘形成的开始，通过免疫细胞化学染色对单标记神经元的髓鞘碱性蛋白进行了评估。最后，轴突能够维持非常高的放电速率，在高达1khz的频率下发生完美的携带。总之，我们的研究结果表明，MSO主神经元中的动作电位信号是高度安全的，但对细胞的体突隔室的侵袭受到限制。这种限制对于最小化在MSO中遇到的高频突触输入时突触整合的畸变可能是重要的。
Principal neurons of the medial superior olive (MSO) convey azimuthal sound localization cues through modulation of their rate of action potential firing. Previous intracellular studies in vitro have shown that action potentials appear highly attenuated at the soma of MSO neurons, potentially reflecting specialized action potential initiation and/or a physically distant site of generation. To examine this more directly, we made dual patch-clamp recordings from MSO principal neurons in gerbil brainstem slices. Using somatic and dendritic whole-cell recordings, we show that graded action potentials at the soma are highly sensitive to the rate of rise of excitation and undergo strong attenuation in their backpropagation into the dendrites (length constant, 76 mu m), particularly during strong dendritic excitation. Using paired somatic whole-cell and axonal loose-patch recordings, we show that action potentials recorded in the axon at distances > 25 mu m are all-or-none, and uniform in amplitude even when action potentials appear graded at the soma. This proximal zone corresponded to the start of myelination in the axon, as assessed with immunocytochemical staining for myelin basic protein in single-labelled neurons. Finally, the axon was capable of sustaining remarkably high firing rates, with perfect entrainment occurring at frequencies of up to 1 kHz. Together, our findings show that action potential signalling in MSO principal neurons is highly secure, but shows a restricted invasion of the somatodendritic compartment of the cell. This restriction may be important for minimizing distortions in synaptic integration during the high frequencies of synaptic input encountered in the MSO.