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蛋白酪氨酸激酶参与β- 淀粉样蛋白对大鼠在体海马CA1 区长时程增强的抑制

郭芬, 李新毅, 王晓晖, 祁金顺^*

山西医科大学生理学教研室，细胞生理学教育部重点实验室，太原 030001

摘要

β- 淀粉样蛋白(β-amyloid protein, Aβ)对突触可塑性和认知功能的伤害效应已被广泛报道，但机制尚不明确。本研 究通过观察Aβ25-35 和蛋白酪氨酸激酶(protein tyrosine kinase, PTK)特异性抑制剂genistein 对大鼠在体海马CA1 区长时程增强 (long-term potentiation, LTP)的效应，揭示Aβ 抑制海马LTP 可能的PTK 机制。实验采用电生理学方法，利用自制的刺激/ 记录绑定电极引导和记录大鼠在体海马CA1 区场兴奋性突触后电位(field excitatory postsynaptic potentials, fEPSPs)、双脉冲 易化(paired-pulse facilitation, PPF)以及高频刺激(high-frequency stimuli, HFS)诱导的LTP。结果显示：(1)侧脑室内注射Aβ25-35 (20 nmol)不影响基础性fEPSPs，但能显著抑制HFS 诱导的LTP，fEPSPs 平均幅度较对照组明显降低；(2)类似于Aβ25-35 的 效应，侧脑室内注射genistein (200 nmol)也不影响基础性fEPSPs，但明显抑制HFS 诱导的LTP，具有与Aβ25-35 有相似的 压抑程度；(3)联合给予Aβ25-35 (20 nmol)和genistein (200 nmol)后，两者对LTP 产生的抑制效应并未进一步加强，与单独 给予Aβ25-35 或genistein 的压抑效应相比，没有显著区别；(4)分别或联合给予Aβ25-35 和genistein 均未影响海马CA1 区PPF。 以上结果表明，脑室内注射Aβ25-35 能够明显抑制大鼠在体海马CA1 区HFS 诱发的LTP，提示阿尔茨海默病时脑内产生的 Aβ 有可能通过影响海马突触可塑性而伤害学习和记忆功能；Aβ25-35 和PTK 抑制剂genistein 对海马LTP 表现出的同等程度抑 制以及联合给药后效应维持不变，提示PTK 系统可能参与了Aβ 对在体大鼠海马LTP 的抑制。

关键词： 蛋白酪氨酸激酶; β - 淀粉样蛋白; 场兴奋性突触后电位; 长时程增强; 海马

分类号：R338

[Involvement of protein tyrosine kinases in β-amyloid protein-induced suppression of long-term potentiation in the rat hippocampal CA1 region in vivo.] [Ariticle in Chinese]

GUO Fen, LI Xin-Yi, WANG Xiao-Hui, QI Jin-Shun^*

Department of Physiology, and the Key Laboratory for Cellular Physiology of Ministry of Education, Shanxi Medical University, Taiyuan 030001, China

Abstract

Although the impairing effects of β-amyloid (Aβ) protein on synaptic plasticity and cognitive function have been widely reported, the mechanisms underlying the neurotoxicity of Aβ are still not well known. The present study observed the effects of intracerebroventricular (i.c.v.) injection of both Aβ25-35 and genistein (a specific tyrosine kinase inhibitor at high concentration) on the hippocampal long-term potentiation (LTP) in the CA1 region, and investigated its possible protein tyrosine kinase (PTK) mechanism. Male Wistar rats were surgically prepared for acute LTP recordings in vivo. Two parallel bond electrodes for stimulating and recording were simultaneously inserted into the right hippocampus of rats. The field excitatory postsynaptic potentials (fEPSPs), paired-pulse facilitation (PPF) and high-frequency stimuli (HFS)-induced LTP were recorded by delivering test stimuli, paired pulses and HFS to the Schaffer-collateral/commissural pathway. The results showed that: (1) i.c.v. injection of Aβ25-35 did not affect the baseline synaptic transmission, but significantly suppressed the HFS-induced LTP, with a decreased average amplitude of fEPSPs [(129.2±6.7)% in 10 nmol Aβ25-35 group; (110.6±8.6)% in 20 nmol Aβ25-35 group; P<0.01] at 1 h post-HFS when compared to that in the control group [(163.1±8.1)%]; (2) Similarly, i.c.v. injection of genistein (200 nmol) did not change the basic synaptic transmission, but significantly suppressed HFS-induced LTP, with the similar average amplitude of fEPSPs [(114.0±7.2)%] at 1 h post-HFS to that in 20 nmol Aβ25-35 group; (3) Co-application of Aβ25-35 (20 nmol) and genistein (200 nmol) caused no additive suppression of LTP, and the average amplitude of fEPSPs was (113.0±8.8)% at 1 h post-HFS, showing no significant difference when compared with that in Aβ25-35 or genistein alone groups (P>0.05); (4) There was no significant change in the PPF following genistein and Aβ25-35 alone or co-injection (P> 0.05). These experimental results indicate that i.c.v. injection of Aβ25-35 can significantly suppress the HFS-induced LTP in the CA1 area of rat hippocampus in vivo, implying that the Aβ deposited in the brain of patients with Alzheimer’s disease may impair the function of learning and memory by suppressing the hippocampal LTP. The facts that the extent of inhibition of Aβ25-35 and genistein on LTP was similar and no further potentiation of the suppression was observed when Aβ25-35 and genistein were co-applied suggest that PTK is probably involved in the Aβ-induced suppression of hippocampal LTP.

Key words: protein tyrosine kinases; amyloid beta-protein; field excitatory postsynaptic potential; long-term potentiation; hippocampus

收稿日期：2008-12-19　　录用日期：2009-03-04

通讯作者：祁金顺　　E-mail: jinshunqi2006@yahoo.com

引用本文：

郭芬, 李新毅, 王晓晖, 祁金顺. 蛋白酪氨酸激酶参与β- 淀粉样蛋白对大鼠在体海马CA1 区长时程增强的抑制[J]. 生理学报 2009; 61 (3): 263-271.

GUO Fen, LI Xin-Yi, WANG Xiao-Hui, QI Jin-Shun. [Involvement of protein tyrosine kinases in β-amyloid protein-induced suppression of long-term potentiation in the rat hippocampal CA1 region in vivo.] [Ariticle in Chinese] . Acta Physiol Sin 2009; 61 (3): 263-271 (in Chinese with English abstract).