在体大鼠海马CA1区侧枝/联合纤维通路和TA通路的不同EPSP空间整合特性

在麻醉Wistar大鼠上，结合脑室给药，应用双电极刺激技术刺激海马独立的两条侧枝／联合纤维通路、TA通路，并在CA1区放射层记录兴奋性突触后电位（EPSP），对海马CA1区锥体细胞近、远端树突EPSP的空间整合进行了初步探讨。结果表明，海马CA1区锥体细胞近、远端树突的空间整合都是亚线性的；近端树突的空间整合不受期望值大小的影响，但远端树突的空间整合随期望值增加而减小（更趋于亚线性）。此外，荷包牡丹碱没有影响EPSP的空间整合；但瞬时A型钾通道（IAK^＋）的拮抗剂氨基吡啶-4却使得近端树突的空间整合趋于线性发展。本研究表明，海马CA1锥体细胞近、远端树突不同的被动、主动特征使它们具有了不同的空间整合特性。由于近端树突接受海马内部侧枝／联合纤维投射的信息，远端树突通过TA通路接受内嗅皮层投射的信息，由此提示，CA1区锥体细胞对来自海马内部和直接来自皮层的信息输入采用了不同的整合方式。

Different Spatial Summation of EPSPs from Schaffer Collateral/Associational Commissural Pathways and Temporoammonic Pathways in Hippocampal CA1 Area in Vivo

We studied the spatial summation of excitatory post synaptic potentials (EPSPs) at proximal and distal dendrites of the hippocampal CAl area by using two stimulating electrodes in anaesthetized Wistar rats. Our results showed that the summation of EPSP was sublinear both at the proximal and the distal dendrites of hippocampal CA1 area. As expected , EPSP amplitudes increased and the summation of distal dendritic EPSPs decreased (though tended to be more sub-linear) but the proximal summation was not affected. Furthermore, bicuculline (GABA receptor antagonist) didn't affect the spatial summation of EPSPs, but AP-4 (antagonist of transient A type K+ channel) made spatial summation of the proximal dendrites linear. Our experiments demonstrate that hippocampal CA1 pyramidal neurons may use different patterns of spatial summation at proximal and distal dendrites. Proximal dendrites of hippocampal CAl pyramidal neurons receive mainly the inputs from schaffer collateral/associational commissural pathways, whereas the distal dendrites receive mainly the inputs from entorhinal cortex through TA (temporoammonic) pathways. These results indicate that that two different summation mechanisms in hippocampal CAl pyramidal neurons are used to process information (1) within the hippocampus and (2) from the entorhnnal cortex.