Kamondi A, Acsády L, Buzsáki G
Center for Molecular and Behavioral Neuroscience, Rutgers, The State University of New Jersey, Newark, New Jersey 07102, USA.
J Neurosci. 1998 May 15;18(10):3919-28. doi: 10.1523/JNEUROSCI.18-10-03919.1998.
In vitro experiments suggest that dendritic fast action potentials may influence the efficacy of concurrently active synapses by enhancing Ca2+ influx into the dendrites. However, the exact circumstances leading to these effects in the intact brain are not known. We have addressed these issues by performing intracellular sharp electrode recordings from morphologically identified sites in the apical dendrites of CA1 pyramidal neurons in vivo while simultaneously monitoring extracellular population activity. The amplitude of spontaneous fast action potentials in dendrites decreased as a function of distance from the soma, suggesting that dendritic propagation of fast action potentials is strongly attenuated in vivo. Whereas the amplitude variability of somatic action potentials was very small, the amplitude of fast spikes varied substantially in distal dendrites. Large-amplitude fast spikes in dendrites occurred during population discharges of CA3-CA1 neurons concurrent with field sharp waves. The large-amplitude fast spikes were associated with bursts of smaller-amplitude action potentials and putative Ca2+ spikes. Both current pulse-evoked and spontaneously occurring Ca2+ spikes were always preceded by large-amplitude fast spikes. More spikes were observed in the dendrites during sharp waves than in the soma, suggesting that local dendritic spikes may be generated during this behaviorally relevant population pattern. Because not all dendritic spikes produce somatic action potentials, they may be functionally distinct from action potentials that signal via the axon.
体外实验表明，树突快速动作电位可能通过增强Ca2+流入树突来影响同时活跃的突触的效能。然而，在完整大脑中导致这些效应的确切情况尚不清楚。我们通过在活体中对CA1锥体神经元顶树突形态学确定部位进行细胞内尖锐电极记录，同时监测细胞外群体活动，来解决这些问题。树突中自发快速动作电位的幅度随距胞体距离的增加而降低，这表明快速动作电位在树突中的传播在活体中强烈衰减。虽然体细胞动作电位的幅度变异性非常小，但快速尖峰的幅度在远端树突中变化很大。树突中的大幅度快速尖峰出现在CA3-CA1神经元群体放电与场尖波同时发生时。大幅度快速尖峰与小幅度动作电位和假定的Ca2+尖峰的爆发有关。电流脉冲诱发的和自发出现的Ca2+尖峰总是先于大幅度快速尖峰出现。在尖波期间，树突中观察到的尖峰比胞体中更多，这表明在这种与行为相关的群体模式期间可能会产生局部树突尖峰。由于并非所有树突尖峰都会产生体细胞动作电位，它们在功能上可能与通过轴突发出信号的动作电位不同。
