Electrophysiological mapping of GABAA receptor-mediated inhibition in adult rat somatosensory cortex.
Electrophysiological mapping of GABAA receptor-mediated inhibition in adult rat somatosensory cortex.
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成年大鼠体感皮层 GABAA 受体介导的抑制的电生理图。
DOI：
10.1152/jn.1996.75.4.1589
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Prince,DA
中科院分区：
文献类型：
--
作者：
Salin,PA;Prince,DA
1.用全细胞膜片钳技术研究了γ-氨基丁酸-A（GABAA）受体介导的皮层内刺激诱发的离体大鼠体感皮层脑片突触电流。所有解剖学鉴定的锥体神经元的第II-III层（SG神经元），第IV层（IV神经元），和第V层（IG神经元）产生诱发抑制性突触后电流（eIPSC），被荷包牡丹碱阻断。在阈值时，eIPSC具有与在相同细胞中产生的自发IPSC相似的动力学性质（上升时间为0.9 ms，衰减时间常数为9 ms）。2.通过确定诱发反应的刺激阈值以及刺激强度与eIPSC峰值幅度之间的关系（输入/输出曲线）来量化抑制的强度。对于在对照溶液中记录的eIPSC，输入/输出曲线比在离子型谷氨酸受体拮抗剂6-氰基-7-硝基喹喔啉-2，3-二酮（CNQX）和D-2-氨基-5-膦酰基戊酸酯（D-AP 5）存在下记录的eIPSC陡约四倍，表明GABAA抑制依赖于中间神经元的突触兴奋。3.在CNQX和D-AP 5存在的情况下，通过靠近记录贴片吸管的刺激诱发的单突触IPSC在SG和IG神经元中具有相似的输入/输出曲线。这表明在这两个细胞群体中产生的单突触抑制水平是相似的。4.当刺激在垂直或水平方向上移动到距离记录的神经元> 350微米的远处时，唤起IPSC所需的刺激强度更高，并且输入/输出曲线不那么陡峭。这表明投射到记录神经元的GABA能胞体和轴突的密度在这些距离处比在更近的部位处低。5.最大水平距离IPSC可以诱发（“水平场”）是在V层比在其他层更大。水平场（刺激和记录移液管之间的距离）为600微米，在层II-III，580微米，在层IV，和720微米，在层V。解剖鉴定的体感皮质桶表明，GABA能的预测的程度大于桶中空，因此可能形成一个基板，在第四层的interbarrel抑制在交叉wisker刺激。6.最大垂直抑制场大于最大水平抑制场。I层刺激可以在V层神经元中诱发IPSC，这表明存在强大的层间抑制，其可能在使列中的神经元的活动同步中起作用。由I层刺激诱发的IPSC通常具有比由接近索马的部位处的刺激诱发的IPSC更慢的动力学。7.这些发现表明，功能性GABA能投射的特点是很大程度的收敛。GABAA介导的IPSC的定量表明，该区域的抑制性突触收敛到一个给定的锥体神经元被细分为一个强大的局部抑制区和周围的区域的远程，不太有效，抑制性的预测。这些同心抑制区在皮层处理感觉信息的潜在作用进行了讨论。
1. gamma-Aminobutyric acid-A (GABAA) receptor-mediated synaptic currents evoked by intracortical stimulation in rat somatosensory cortical slices maintained in vitro were studied using the whole cell patch-clamp technique. All anatomically identified pyramidal neurons of layer II-III (SG neurons), layer IV (IV neurons), and layer V (IG neurons) generated evoked inhibitory postsynaptic currents (eIPSCs) that were blocked by bicuculline. At threshold, eIPSCs had kinetic properties (rise time of 0.9 ms and decay time constant of 9 ms) similar to those of spontaneous IPSCs generated in the same cells. 2. The strength of inhibition was quantified by determining the stimulus threshold for evoking responses and the relationship between stimulus strength and eIPSC peak amplitudes (input/output curve). For eIPSCs recorded in control solution, the input/output curve was about four times steeper than for eIPSCs recorded in the presence of the ionotropic glutamate receptor antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and D-2-amino-5-phosphonovalerate (D-AP5), suggesting the dependence of GABAA inhibition on synpatic excitation of interneurons. 3. In the presence of CNQX and D-AP5, monosynaptic IPSCs, evoked by stimulation close to the recording patch pipette, had similar input/output curves in SG and IG neurons. This suggests that the level of monosynaptic inhibition generated in these two populations of cells is similar. 4. When the stimulus was moved to a distant site > 350 microns from the recorded neuron, either in vertical or in horizontal direction, the stimulus intensity required for evoking IPSCs was higher, and the input/output curve was less steep. This suggests that the density of GABAergic somata and axons projecting to the recorded neuron is lower at these distances than at more proximal sites. 5. The maximum horizontal distance over which IPSCs could be evoked ("horizontal field") was larger in layer V than in other layers. The horizontal field (distance between stimulating and recording pipettes) was 600 microns in layer II-III, 580 microns in layer IV, and 720 microns in layer V. Anatomic identification of the somatosensory cortical barrels indicated that the extent of GABAergic projections was larger than the barrel hollow and might thus form a substrate for interbarrel inhibition in layer IV during cross-wisker stimulation. 6. The maximum vertical inhibitory field was larger than the maximum horizontal field. IPSCs could be evoked in layer V neurons by layer I stimuli, showing that a powerful interlaminar inhibition is present that may play a role in synchronizing the activity of neurons in a column. IPSCs evoked by layer I stimulation frequently had slower kinetics than those elicited by stimulation at sites close to the soma. 7. These findings suggest that functional GABAergic projections are characterized by a large degree of convergence. Quantification of GABAA-mediated IPSCs indicates that this zone of inhibitory synaptic convergence onto a given pyramidal neuron is subdivided into a powerful local inhibitory zone and a surrounding area of long-range, less effective, inhibitory projections. Potential roles for these concentric inhibitory areas in cortical processing of sensory information are discussed.