齿状回突触后电位和群峰电位的负相关现象

考察大鼠静卧状态下，相同强度刺激信号作用于前穿质通道时，海马齿状回颗粒细胞诱发电场电位的兴奋性突触后电位EPSP和群峰电位PS之间的一种负相关变化关系，即EPSP斜率减小时，PS幅值增加。采用同时记录齿状回诱发电位和大脑皮层ECoG电位的方法，分析诱发电位各成份和ECoG功率谱密度之间的关系，可见ECoG出现低频高幅慢波时，与ECoG出现高频低幅快波时比较，齿状回诱发响应的PS幅值较大，而EPSP斜率较小。这可能是因为：中脑网状结构上行激励系统通过丘脑－皮层回路使ECoG去同步化（出现低幅快波ECoG）时，同时也通过另一途径，即隔－海马连接，激活了作用于齿状回颗粒细胞胞体的抑制性神经通路，使得颗粒细胞兴奋性降低，从而使反应动作电位总和的PS幅值减小。在麻醉剂乌拉坦作用下，EPSP和PS的负相关变化减小或消失。这种负相关现象对于研究海马的生理功能具有重要的意义。

THE NEGATIVE CORRELATION BETWEEN EPSPs AND PSs IN THEEVOKED RESPONSES OF RAT DENTATE GYRUS

A kind of negative correlation between EPSPs and PSs of the evoked field responses in the dentate gyrus of quiet rest rats was studied. That is, while EPSP declined, PS increased. The ECoG potentials were recorded simultaneously with the evoked potentials. And it was found that during the high voltage slow wave ECoG periods, compared with the low voltage fast wave ECoG periods, PSs increased and EPSPs decreased. It indicated that when the midbrain reticular formation induced cortical desynchronization through the thalamocortical loop, it simultaneously excitated an inhibitory path which acted on the bodies of dentate granule cells and declined the excitability of granule cells. After the injection of Urethane, the negative correlation between EPSPs and PSs were weakened. The negative correlation may be an indication of the activity changes in dentate gyrus during the hypnosis or doze states of rats. So it is significant to study the phenomenon.