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首页> 外文期刊>Journal of Neurophysiology >Physiological properties of neurons in the optic layer of the rat's superior colliculus.
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Physiological properties of neurons in the optic layer of the rat's superior colliculus.

机译：大鼠上丘视神经层神经元的生理特性。

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摘要

We made intracellular recordings from 74 neurons in the optic layer of the rat superior colliculus (SC). Resting membrane potentials were -62.3 +/- 6.2 (SD) mV, and input resistances were 37.9 +/- 10.1 MOmega. Optic layer neurons had large sodium spikes (74.2 +/- 12.3 mV) with an overshoot of 12 mV and a half-amplitude duration of 0.75 +/- 0.2 ms. Each sodium spike was followed by two afterhyperpolarizations (AHPs), one of short duration and one of longer duration, which were mediated by tetraethylammonium (TEA)-sensitive (IC) or apamin-sensitive (IAHP) calcium-activated potassium currents, respectively. Sodium spikes were also followed by an afterdepolarization (ADP), which was only revealed when the AHPs were blocked by TEA or apamin. In response to hyperpolarizing current pulses, optic layer neurons showed an inward rectification mediated by H channels. At the break of the current pulse, there was a rebound low-threshold spike (LTS) with a short duration of <25 ms. The LTS usually induced two sodium spikes (doublet). Most optic layer neurons (84%) behaved as intrinsically bursting cells. They responded to suprathreshold depolarization with an initial burst (or doublet) followed by a train of regular single spikes. The remaining 16% of cells acted as chattering cells with high-frequency gamma (20-80 Hz) rhythmic burst firing within a narrow range of depolarized potentials. The interburst frequency was voltage dependent and also time dependent, i.e., showed frequency adaptation. Unmasking the ADP with either TEA or apamin converted all of the tested intrinsically bursting cells into chattering cells, indicating that the ADP played a crucial role in the generation of rhythmic burst firing. Optic layer neurons receive direct retinal excitation mediated by both N-methyl--aspartate (NMDA) and non-NMDA receptors. Optic tract (OT) stimulation also led to gamma-aminobutyric acid-A (GABAA) receptor-mediated inhibition, the main effect of which was to curtail the excitatory response to retinal inputs by shunting the excitatory postsynaptic current. Intracellular staining with biocytin showed that the optic layer neurons that we recorded from were mostly either wide-field vertical neurons or other cells with predominately superficially projecting dendrites. These cells were similar to calbindin immunoreactive cells seen in the optic layer. The characteristics of these optic layer neurons, such as prominent AHPs, strong shunting effect of inhibition, and short-lasting LTS, suggest that they respond transiently to retinal inputs. This is consistent with a function for these cells as the first relay station in the extrageniculate visual pathway.
机译：我们从大鼠上丘（SC）视神经层的74个神经元进行了细胞内记录。静息膜电位为-62.3 +/- 6.2（SD）mV，输入电阻为37.9 +/- 10.1 MOmega。视神经层神经元具有较大的钠尖峰（74.2 +/- 12.3 mV），过冲为12 mV，半振幅持续时间为0.75 +/- 0.2 ms。每个钠峰值后都有两个后超极化（AHP），一个持续时间短，一个持续时间较长，分别由四乙铵（TEA）敏感（IC）或氨基甲酸酯敏感（IAHP）钙激活的钾电流介导。钠尖峰之后还带有后去极化（ADP），只有当AHP被TEA或Apapamin阻断时才显示出来。响应于超极化电流脉冲，视层神经元显示出由H通道介导的向内整流。在电流脉冲的中断处，有一个持续时间小于25 ms的回弹低阈值尖峰（LTS）。 LTS通常会引起两个钠尖峰（双峰）。大多数视神经层神经元（84％）表现为内在爆发的细胞。他们对超阈值去极化做出了反应，首先出现突发（或双峰），然后出现一连串规则的单个尖峰。剩余的16％的电池充当颤动电池，在较窄的去极化电势范围内具有高频伽马（20-80 Hz）的节奏性爆发。突发频率是电压依赖性的，也是时间依赖性的，即显示出频率适应性。用TEA或Apapamin掩盖ADP会将所有测试的内在爆发细胞转变为颤动细胞，这表明ADP在有节奏的爆发射击中起着至关重要的作用。视神经层神经元接受由N-甲基天门冬氨酸（NMDA）和非NMDA受体介导的直接视网膜兴奋。视线（OT）刺激还导致γ-氨基丁酸-A（GABAA）受体介导的抑制，其主要作用是通过分流兴奋性突触后电流来减少对视网膜输入的兴奋性反应。用细胞周期蛋白染色进行的细胞内染色显示，我们记录的视神经层神经元大部分是宽视野垂直神经元或其他具有表面突出的树突的细胞。这些细胞类似于在视神经层看到的钙结合蛋白免疫反应性细胞。这些视神经层神经元的特征，例如突出的AHP，强烈的抑制分流作用和短暂的LTS，表明它们对视网膜输入有短暂反应。这与这些细胞作为细胞外视觉通路中的第一个中继站的功能是一致的。

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