A study on the intrinsic inhibitory circuit in the cat motor cortex.

1.在体外脑片标本上，研究了CNQX和APV对猫运动皮质的抑制作用。2.皮质内微刺激后，II-VI层锥体细胞产生快的和慢的IPSP，分别用荷包牡丹碱和苯氯芬选择性地减少。3.刺激细胞体所在的同一层时，快的IPSP产生最多，并且随着刺激更浅的层而幅度降低。相反，无论记录器锥体细胞的位置如何，刺激Layr II都能最大限度地产生慢IPSP，并随着刺激更深的层而幅度降低。4.当刺激位置垂直向更浅的层移动时，快速IPSP的幅度降低总是与上升时间的增加和反转电位向更超极化的水平移动相关。5.当刺激位置移动时，…快速型IPSP潜伏期延长，波幅逐渐降低，但上升时间无明显变化。6.负责诱发快速IPSP的抑制中间神经元似乎分布在几乎所有的层中，发出水平分布的平行轴突，沿着单个锥体细胞的顶端树突在不同的电张力距离处进行突触接触。7.慢速IPSP的水平扩散明显减少(340-680微米)。第V层锥体细胞产生的慢速IPSP的达峰时间(159.5)SY。-.(6.8ms，n=10)显著长于第II层和第III层锥体细胞(128.5±sY)(p&lt；0.0001)。-.()7.5毫秒，n=7)。8.在Layr V锥体细胞中，慢IPSP的达峰时间随膜超极化的增加而缩短，表明慢IPSP的晚期比早期对膜电位的变化更敏感。这进一步表明，慢IPSP的晚期部分产生于锥体细胞树突更近端的突触上，而不是早期部分，这与Rall的被动树突模型在同步输入条件下的预期相反。9.提示非同步突触轰击可能发生在远端突触的轰击先于近端突触的轰击。这种非同步突触轰击可能是由于抑制性中间神经元的轴突垂直下降，使突触沿着顶树突传递。10.快慢IPSP的不同时空模式提示存在两种不同类型的抑制性中间神经元，它们按层不同地分布，分别具有水平扩张和垂直下降的轴突。较少

1.The spatio-temporal pattern of inhibition in the cat motor cortex was studied in in vitro slice preparations in the presence of CNQX and APV.2.Following intracortical microstimulation, fast and slow IPSPs were produced in layrs II-VI pyramidal cells and selectively reduced with bicuculline methiodide and phaclofen, respectively.3.Fast IPSPs were maximally produced by stimulation of the same layr where their cell bodies were located, and decreased in amplitude as the more superficial layr was stimulated. In contrast, slow IPSPs were maximally produced by stimulation of layr II regardless of the location of the recorder pyramidal cell, and decreased in amplitude as the deeper layr was stimulated.4.The reduction of amplitude of fast IPSPs, in response to a vertical shift of the stimulation site toward more superficial layrs, was always correlated with an increase in rise time and with a shift of the reversal potential to a more hyperpolarized level.5.When the stimulation site was moved … More horizontally to the more lateral site, fast IPSPs increased in latency and decreased in amplitude gradually without appreciable changes in rise time. Fast IPSPs could be evoked from horizontally remote sites of up to 800-1200 mum.6.Inhibitory interneurons, which are responsible for evoking fast IPSPs, appear to be distributed through almost all layrs to send horizontally spreading parallel axons making synaptic contacts at different electrotonic distances along apical dendrites of single pyramidal cells.7.Horizontal spreads were much less in slow IPSPs (<340-680 mum). The time-to-peak of slow IPSPs produced in layr V pyramidal cells (159.5(〕SY.+-.〔)6.8 msec, n=10) was significantly (p<0.0001) longer than that in layrs II and III pyramidal cells (128.5(〕SY.+-.〔)7.5msec, n=7). Asymmetrical reversal properties of slow IPSPs were seen, suggesting the spatial dispersion of synaptic inputs along apical dendrites of pyramidal cells.8.In layr V pyramidal cells, the time-to peak of slow IPSPs decreased with increasing membrane hyperpolarization, indicating that the late portion of slow IPSPs was more sensitive to the membrane potential change than the early portion. This further indicates that the late portion of slow IPSPs is generated at synapses on the more proximal dendrite of pyramidal cells than the early portion, contrary to that expected from the Rall's model of passive dendrite under the condition of synchronous inputs.9.It is suggested that asynchronous synaptic bombardments may occur in such a way that bombardments at distal synapses precede those at proximal synapses. Such asynchronous synaptic bombardments may be caused by inhibitory interneurons with vertically descending axons, making en passant synapses along apical dendrites.10.Differential spatio-temporal patterns of fast and slow IPSPs suggest the presence of two types of inhibitory interneurons, which are distributed differentially by layrs and have horizontally spreading and vertically descending axons, respectively. Less