Different corticostriatal suprathreshold responses in direct and indirect striatal projection neurons (SPNs) of rodents have been reported. Responses consist in prolonged synaptic potentials of polysynaptic and intrinsic origin, in which voltage-gated Ca2 ⁺ currents play a role. Recording simultaneous Ca2 ⁺ imaging and voltage responses at the soma, while activating the corticostriatal pathway, we show that encoding of synaptic responses into trains of action potentials (APs) is different in SPNs: firing of APs in D1-SPNs increase gradually, in parallel with Ca2 ⁺ entry, as a function of stimulus intensity. In contrast, D2-SPNs attain a maximum number of evoked spikes at low stimulus intensities, Ca2 ⁺ entry is limited, and both remain the same in spite of increasing stimulus strength. Stimulus needs to reach certain intensity, to have propagated Ca2 ⁺ potentials to the soma plus a sudden step in Ca2 ⁺ entry, without changing the number of fired APs, phenomena never seen in D1-SPNs. Constant firing in spite of changing stimulus, suggested the involvement of underlying inactivating potentials. We found that Caᵥ3 currents contribute to Ca2+ entry in both classes of SPNs, but have a more notable effect in D2-SPNs, where a low-threshold spike was disclosed. Blockade of CaV 3 channels retarded the steep rise in firing in D2-SPNs. Inhibition block increased the number of spikes fired by D2-SPNs, without changing firing in D1-SPNs. These differences in synaptic integration enable a biophysical dissimilarity: dendritic inhibition appears to be more relevant for D2-SPNs. This may imply distinctions in the set of interneurons affecting each SPN class.

中文翻译：

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直接和间接纹状体投射神经元之间突触整合的差异：CaV 3通道的作用。

啮齿类动物的直接和间接纹状体投射神经元（SPNs）中皮质上皮超阈反应不同。响应包括多突触和固有起源的延长的突触电位，其中电压门控的Ca2 +电流在其中起作用。记录同时的Ca2 +成像和在体细胞的电压响应，同时激活皮层纹状体通路，我们发现在SPN中，将突触响应编码为一系列动作电位（APs）：在D1-SPNs中，AP的发射逐渐增加Ca 2+进入时，与刺激强度有关。相反，D2-SPNs在低刺激强度下会达到最大的诱发尖峰，Ca2 +的进入受到限制，尽管刺激强度增加，但两者保持不变。刺激需要达到一定的强度，在没有改变发射AP的数量的情况下，已经将Ca2 +的势能传播到了躯体，并突然进入了Ca2 +的进入，这是D1-SPN中从未见过的现象。尽管刺激改变，但持续不断的发射表明潜在的失活电位的参与。我们发现，Caᵥ3电流在两种类型的SPN中都有助于Ca2 +的进入，但在D2-SPN中却有更显着的影响，在D2-SPN中公开了低阈值尖峰。CaV 3通道的阻滞阻止了D2-SPN中发射的急剧上升。抑制块增加了D2-SPN发射的尖峰数量，而没有改变D1-SPN的发射。突触整合中的这些差异使生物物理上的差异：树突状抑制似乎与D2-SPN更相关。这可能意味着在影响每个SPN类的中间神经元集合中有所区别。