Differences in the refractory properties of two distinct inhibitory circuitries in field CA1 of the hippocampus
Differences in the refractory properties of two distinct inhibitory circuitries in field CA1 of the hippocampus
复制标题
DOI：
10.1016/0006-8993(95)01137-4
复制
发表时间：
1995-12-18
期刊：
影响因子：
2.9
通讯作者：
Lynch, G
中科院分区：
文献类型：
--
作者：
Arai, A;Silberg, J;Lynch, G
在海马 CA1 区域的两个不同回路中检查了 IPSP 的细胞外反射。在 AMPA 受体拮抗剂存在的情况下刺激辐射层会在同一层中引发正电位，该电位被印防己毒素（一种 GABA(A) 受体阻断剂）消除。层流分布分析表明，辐射层中远离锥体细胞体层的点处的响应最大，并且在方向层中具有负反射。这些场 IPSP 可能介导通常由 Schaffer 连合投射到 CA1 场激活的前馈抑制。刺激肺泡会产生逆向反应，然后在锥体细胞层收集的记录中产生慢得多的正电位。后一种反应被 AMPA 受体拮抗剂或印防己毒素抑制，正如预期的突触重复性（反馈）抑制一样。反馈场 IPSP 的层流分布在锥体细胞层附近达到最大值，在辐射层中达到负偶极子。如果前馈 IPSP 在 200 毫秒内受到启动脉冲，则前馈 IPSP 会被抑制约 50%，而反馈 IPSP 在可比条件下会减少不到 20%。不应性效应对刺激强度的依赖性最小，但受 GABA(B) 受体拮抗剂的强烈影响。尝试修改 s 中的 IPSP。辐射用长串低频刺激或θ突发刺激并不成功，这表明GABA能突触不具有谷氨酸能突触中发现的可塑性。这些结果表明，海马外源传入接触的中间神经元形成 GABA 能突触，其空间位置和功能特性与锥体细胞循环侧支神经支配的中间神经元产生的突触不同。研究结果还表明，重复的传入活动在减少树突状 IPSP 对兴奋性输入的影响的同时，将使细胞尖峰的反馈抑制基本完好无损。
Extracellular reflections of IPSPs were examined in two distinct circuitries in field CA1 of the hippocampus. Stimulation in the stratum radiatum in the presence of AMPA receptor antagonists elicited positive potentials in the same stratum that were eliminated by picrotoxin, a blocker of GABA(A) receptors. Laminar profile analysis revealed that the response was maximal in the stratum radiatum at a point well distal to the pyramidal cell body layer and had a negative reflection in the stratum oriens. These field IPSPs presumably mediate the feedforward inhibition normally activated by the Schaffer-commissural projections to field CA1. Stimulation of the alveus produced an antidromic response followed by a much slower positive potential in recordings collected in the pyramidal cell layer. The latter response was suppressed by AMPA receptor antagonists or picrotoxin, as expected for disynaptic, recurrent (feedback) inhibition. The laminar profile for the feedback field IPSPs had its maximum near the pyramidal cell layer and its negative dipole in the stratum radiatum. Feedforward IPSPs were inhibited by about 50% if they were preceded within 200 ms by a priming pulse while feedback IPSPs were reduced by less than 20% under comparable conditions. The refractory effect was minimally dependent on stimulation intensity but was strongly affected by an antagonist of GABA(B) receptors. Attempts to modify IPSPs in the s. radiatum with long trains of low frequency stimulation or with theta-burst stimulation were not successful, suggesting that GABAergic synapses do not have the plasticities found in their glutamatergic counterparts. These results indicate that interneurons contacted by the extrinsic afferents of hippocampus form GABAergic synapses that differ in terms of spatial location and functional properties from the synapses generated by interneurons innervated by the recurrent collaterals of the pyramidal cells. The findings also suggest that repetitive afferent activity, while reducing the influence of dendritic IPSPs on excitatory input, will leave feedback suppression of cell spiking largely intact.