同一学习中海马不同区的习得性长时程突触增强的形成

THE FORMATION OF LEARNING-DEPENDENT LONG-TERM POTENTIATION IN DIFFERENT HIPPOCAMPAL AREAS DURING LEARNING

本研究探查大鼠分辨学习中海马齿状回(DG)和CA_3区突触效应的变化及其相互关系,以探讨同一学习中海马不同区突触可塑性变化的特点及其相互关系,进一步论证习得性长时程增强(LTP)是学习和记忆的神经基础。发现:(1)穿通纤维的单个刺激可在DG和CA_3同时记录到潜伏期、峰值和波形各异的群体峰电位(PS);在一定范围内PS随刺激强度的增加而增大,但DG的PS增大程度比CA_3的小;据此,检测刺激的强度应选在该范围内。(2)随着行为训练,DG和CA_3区的突触传递同时产生LTP,两者LTP的发展是显著正相关关系(P<0.01),PS峰值同时达到最高水平,且先于分辨反应达学会标准,首次表明在同一学习中大鼠海马的DG和CA_3的习得性LTP是同时产生的。本研究还表明,在慢性实验下同时记录和分析行为学习中海马两个区突触效应的变化及其相互关系是可能的,这给从神经环路角度研究学习和记忆的突触机制提供了有用的模型。

The changes and their interrelations of synaptic transmission inboth CA_3 and dentate gyrus(DG) of rat hippocampus during discri-mination learning were observed in order to investigate the charac-teristics and mutual relations of the changes of synaptic plasticityin different hippocampal areas with the processing of learning. (1)Population spike(PS) in the CA_3 and DG were simultaneously elici-ted by stimulating the perforant path (PP). The amplitude of PSincreased in response to a series of increases of the stimulation in-tensity, but the increase of amplitude of PS in the DG was lessthan in the CA_3 area. (2)The learning-dependent long-term potentia-tions(LDLTP) in the CA_3 and DG were induced simultaneously withthe acquisition of the behavioral response. There was a significantpositive relation during the developing of LDLTP in the two areas(R=0.9806, p<0.01). Both maximal level of amplitude of PS in CA_3and DG preceded those of the correct behavior response. Resultsshowed that LDLTP of the synaptic transmission of PP-CA_3 andPP-DG were simultaneously produced during the discrimination learn-ing, and provided a new way to record and analyse at the same time thechanges and their correlation of synaptic transmission between thetwo hippocampal areas under the situation of chronic recording.