去极化刺激强度对小鼠大脑皮层γ氨基丁酸能神经元内在特性和编码能力的影响

Influence of depolarizing stimulus intensity on intrinsic properties and encoding of cerebral GABAergic neurons in mice

目的研究小鼠大脑皮层γ氨基丁酸(GABA)能神经元活动的内在特性和编码能力随去极化刺激强度的增加而发生的动态变化。方法出生后15～22 d的FVB-Tg(Gad GFP)45704 Swn/J小鼠断头取脑,将脑片进行体外培养,运用Axoclamp-2B放大器全细胞记录方法记录内在特性和编码参数。观察随去极化刺激强度的增加(分为阈刺激强度×0.7、×0.85、×1、×1.25组),小鼠大脑皮层GABA能神经元绝对不应期(ARP)、动作电位间距(ISI)和动作电位发放峰时程标准差(SDST)的变化;分析大脑皮层GABA能神经元ARP与ISI和SDST间的关系。结果随着去极化刺激强度的增加,小鼠大脑皮层GABA能神经元群集发放动作电位的发放容量增加,ARP、ISI和SDST均显著缩短(P<0.01)。阈刺激强度×0.7、×0.85、×1、×1.25各组ARP与ISI之间均呈线性关系(r2分别为0.9、0.91、0.82和0.84,均P<0.05),ARP与SDST之间也均呈线性关系(r2分别为0.97、0.98、0.93和0.89,均P<0.05)。结论随着去极化刺激强度的增加,大脑皮层GABA能神经元发放动作电位的ARP缩短,使其发放群集动作电位和编码神经信息的能力增强。加强对大脑皮层GABA能神经元刺激程度更有利于神经系统功能保持稳态。

Objective To investigate the dynamic changes of intrinsic properties and encoding at cortical GABAergic neurons with increase of depolarizing stimulus intensity in mice. Methods FVB-Tg （Gad GFP） 45704 Swn/J mice aged 15 to 22 d were sacrificed, and the cortical slices were obtained and cultured in vitro. The intrinsic properties and encoding parameters were recorded by using Axoclamp-2B amplifier. The changes of inter-spike intervals （ISI） and standard deviation of spike timing （SDST）, as well as absolute refractory period （ARP） at cortical GABAergic neurons with increase of depolarizing stimulus intensity （threshold stimulus intensity × 0.7 group, x 0.85 group, × 1 group and× 1.25 group respectively） in mice were observed, and the association of ARP at cortical GABAergic neurons with ISI and SDST was analysed. Results With the increase of depolarizing stimulus intensity, the spike capacity of cortical GABAergic neurons was significantly increased, and ARP, ISI and SDST were significantly decreased （P 〈 0.01）. There was linear correlation between ARP and ISI in threshold stimulus intensity × 0.7 group, x 0.85 group, x 1 group and × 1.25 group （r^2 = 0.9, 0.91, 0. 82 and 0. 84 respectively, P 〈 0. 05 for all）, and there was also linear correlation between ARP and SDST in these groups （r^2 = 0.97, 0.98, 0.93 and 0.89 respectively, P 〈 0.05 for all）. Conclusion With the increase of depolarizing stimulus intensity, the reduction of ARP at cortical GABAergic neurons improves spike capacity and capability of neural coding, which in turn enhances their ability in stabilizing the excitatory state of cerebral cortex.