碱中毒对小鼠皮质GABA能神经元特性和编码能力的影响

Influence of Alkalosis on Intrinsic Properties and Encoding of Cerebral GABAergic Neurons in Mice

目的:研究碱中毒对小鼠皮质GABA能神经元内在特性和编码能力的影响,探讨碱中毒引起大脑功能障碍的机制。方法:选择17-22天FVB-Tg小鼠行脑片体外培养,实验对象分为碱中毒组和对照组。DIC光学显微镜下选择皮层II-III层GABA神经元,运用Axo Patch 200 B放大器全细胞模式,记录并分析神经元内在特性(包括阈电位、绝对不应期)的改变;记录与去极化脉冲相对应的峰值,分析GABA能神经元的编码能力。结果:1.阈电位峰值在对照组分别是24.58±0.68,25.44±0.82,27.02±0.78,27.55±0.74和28.66±0.79毫伏,碱中毒组分别是28.32±0.78,30.10±0.91,32.22±0.80,32.88±0.76和33.54±0.74毫伏,碱中毒组阈电位升高;绝对不应期在对照组和碱中毒组分别是4.15±0.06和5.09±0.08毫秒,碱中毒绝对不应期延长。2.两组在相同去极化刺激下诱发的连续峰值波形发生明显改变,碱中毒组产生峰值的能力下降。结论:1、碱中毒使皮质GABA能神经元动阈电位升高和绝对不应期延长;2、碱中毒降低皮质GABA能神经元编码峰值能力。

Objective： To discuss the mechanisms underlying alkalosis-induced cerebral deficits, we investigate the in覲uences of alkalosis on GABAergic neurons including their intrinsic properties and neuronal encodings in the cortical slices. Methods： Cortical slices were made from FVB-Tg mice in postnatal day 17-22 and were divided into experimental group and control group. Cortical GABAergic neurons for whole-cell recordings were selected under a DIC-fluorescent microscope. Cortical GABAergic neurons were recorded by an Axo Patch-200 B ampli覲er for analyzing their intrinsic properties. Recording the number of spikes versus the intensities of depolarization pulses was used to evaluate the ability of encoding sequential spikes. Results： 1.Vts values for spikes 1-5 are 24.58±0.68,25.44 ±0.82, 27.02 ±0.78, 27.55 ±0.74 and 28.66 ±0.79 m V under the control, and are 28.32 ±0.78, 30.10 ±0.91, 32.22 ±0.80,32.88±0.76 and 33.54±0.74 m V under high [p H]o. Alkalosis elevates the threshold potentials of producing sequential spikes. Spike ARP appear to be prolonged by high [p H]o, compared with the control group. ARP values are 4.15 ±0.06 and 5.09 ±0.08 ms under the conditions of control and high [p H]o, respectively. Alkalosis prolongs the refractory periods of sequential spikes at cortical GABAergic neurons. 2. The spikes induced by the same intensities of depolarization under the conditions of control and alkalosis are statistically different, indicating that alkalosis impairs the ability of encoding sequential spikes. Conclusions： 1.It is revealed that alkalosis elevates the threshold potential and prolongates the refractory periods of cortical GABAergic neuron.2.Alkalosis appears to reduce the ability of encoding sequential spikes.