Ca2++ transients can be observed in the distal dendrites of Purkinje cells (PCs) despite their lack of action potential backpropagation. These Ca2++ events in distal dendrites require specific patterns of PC firing, such as complex spikes (CS) or simple spikes (SS) of burst mode. Unlike CS, which can act directly on voltage-gated calcium channels in the dendrites through climbing fiber inputs, the condition that can produce the Ca2++ events in distal dendrites with burst mode SS is poorly understood. Here, we propose the interspike interval threshold (ISIT) for Ca2++ transients in the distal dendrites of PC. We found that to induce the Ca2++ transients in distal dendrites the frequency of spike firing of PC should reach 250 Hz (3 ms ISI). Metabotropic glutamate receptor 1 (mGluR1) activation significantly relieved the ISIT and established cellular conditions in which spike firing with 50 Hz (19 ms ISI) could induce Ca2++ transients in the distal dendrites. In contrast, blocking T-type Ca2++ channels or depleting the endoplasmic reticulum Ca2++ store resulted in a stricter condition in which spike firing with 333 Hz (2 ms ISI) was required. Our findings demonstrate that the PC has strict ISIT for dendritic Ca2++ transients, and this ISIT can be relieved by mGluR1 activation. This strict restriction of ISIT could contribute to the reduction of the signal-to-noise ratio in terms of collecting information by preventing excessive dendritic Ca2++ transients through the spontaneous activity of PC.

中文翻译：

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mGluR1 调节小脑浦肯野细胞中树突状 Ca2+ 瞬变的尖峰间期阈值。

Ca2++ 瞬变可以在浦肯野细胞 (PC) 的远端树突中观察到，尽管它们缺乏动作电位反向传播。远端树突中的这些 Ca2++ 事件需要特定的 PC 发射模式，例如突发模式的复杂尖峰 (CS) 或简单尖峰 (SS)。与 CS 不同，CS 可以通过攀爬纤维输入直接作用于树突中的电压门控钙通道，而对于可以在具有突发模式 SS 的远端树突中产生 Ca2++ 事件的条件知之甚少。在这里，我们提出了 PC 远端树突中 Ca2++ 瞬变的尖峰间期阈值 (ISIT)。我们发现，要在远端树突中诱导 Ca2++ 瞬变，PC 的尖峰发射频率应达到 250 Hz（3 ms ISI）。代谢型谷氨酸受体 1 (mGluR1) 激活显着缓解了 ISIT 并建立了细胞条件，其中 50 Hz（19 ms ISI）的尖峰发射可以在远端树突中诱导 Ca2++ 瞬变。相比之下，阻断 T 型 Ca2++ 通道或耗尽内质网 Ca2++ 存储会导致更严格的条件，其中需要 333 Hz（2 ms ISI）的尖峰发射。我们的研究结果表明，PC 对树突状 Ca2++ 瞬变具有严格的 ISIT，并且可以通过 mGluR1 激活来缓解这种 ISIT。ISIT 的这种严格限制可以通过防止 PC 自发活动引起的过度树突 Ca2++ 瞬变，从而有助于降低收集信息方面的信噪比。