A. C. Errington: Neuroscience Division, School of Biosciences, Cardiff University, Museum Avenue, Cardiff CF10 3AX, UK.
J Physiol. 2012 Aug 15;590(16):3691-700. doi: 10.1113/jphysiol.2012.232132. Epub 2012 May 28.
The distribution of T-type Ca2+ channels along the entire somatodendritic axis of sensory thalamocortical (TC) neurons permits regenerative propagation of low threshold spikes (LTS) accompanied by global dendritic Ca2+ influx. Furthermore, T-type Ca2+ channels play an integral role in low frequency oscillatory activity (<1–4 Hz) that is a defining feature of TC neurons. Nonetheless, the dynamics of T-type Ca2+ channel-dependent dendritic Ca2+ signalling during slow sleep-associated oscillations remains unknown. Here we demonstrate using patch clamp recording and two-photon Ca2+ imaging of dendrites from cat TC neurons undergoing spontaneous slow oscillatory activity that somatically recorded δ (1–4 Hz) and slow (<1 Hz) oscillations are associated with rhythmic and sustained global oscillations in dendritic Ca2+. In addition, our data reveal the presence of LTS-dependent Ca2+ transients (Δ[Ca2+]) in dendritic spine-like structures on proximal TC neuron dendrites during slow (<1 Hz) oscillations whose amplitudes are similar to those observed in the dendritic shaft. We find that the amplitude of oscillation associated Δ[Ca2+] do not vary significantly with distance from the soma whereas the decay time constant (τdecay) of Δ[Ca2+] decreases significantly in more distal dendrites. Furthermore, τdecay of dendritic Δ[Ca2+] increases significantly as oscillation frequency decreases from δ to slow frequencies where pronounced depolarised UP states are observed. Such rhythmic dendritic Ca2+ entry in TC neurons during sleep-related firing patterns could be an important factor in maintaining the oscillatory activity and associated biochemical signalling processes, such as synaptic downscaling, that occur in non-REM sleep.
T 型钙通道沿感觉丘脑皮质 (TC) 神经元的整个体树突轴分布，允许伴随全局树突钙内流的低阈值 spikes (LTS) 的再生传播。此外，T 型钙通道在低频振荡活动（<1-4 Hz）中发挥着不可或缺的作用，这是 TC 神经元的一个特征。尽管如此，在慢波睡眠相关振荡期间，T 型钙通道依赖性树突钙信号的动力学仍然未知。在这里，我们使用在经历自发慢振荡活动的猫 TC 神经元的树突进行的膜片钳记录和双光子钙成像来证明，在体记录的 δ（1-4 Hz）和慢（<1 Hz）振荡与全局树突钙的节律性和持续振荡相关。此外，我们的数据还揭示了在慢 (<1 Hz) 振荡期间，在 TC 神经元近端树突的树突棘样结构中存在 LTS 依赖性 Ca2+瞬变（Δ[Ca2+]），其幅度与在树突干中观察到的幅度相似。我们发现，与体距离相比，与振荡相关的 Δ[Ca2+]的幅度没有显著变化，而 Δ[Ca2+]的衰减时间常数（τdecay）在更远的树突中显著降低。此外，随着振荡频率从 δ 降低到慢频率（在慢频率下观察到明显的去极化 UP 状态），树突 Δ[Ca2+]的 τdecay 显著增加。在睡眠相关放电模式下，TC 神经元中这种节律性的树突钙内流可能是维持振荡活动和相关生化信号过程的一个重要因素，例如非快速眼动睡眠中的突触下调。
