Harney Sarah C, Jones Mathew V
Department of Physiology, University of Wisconsin-Madison, SMI 127, 1300 University Avenue, 53706, USA.
Neuropharmacology. 2002 Sep;43(4):584-94. doi: 10.1016/s0028-3908(02)00169-7.
We compared somatic and dendritic inhibition in paired recordings from two classes of anatomically identified interneurons and granule cells of the dentate gyrus. Inhibitory postsynaptic current (IPSC) amplitude and decay were remarkably similar at somatic and dendritic synapses. Slower IPSC rise times and longer latencies at dendritic synapses were consistent with their distal location, without requiring differences in postsynaptic gamma-aminobutyric acid type A (GABA(A)) receptor properties. In contrast, higher transmission failure rate and greater paired-pulse depression at dendritic synapses suggest that somatic and dendritic inhibition differ in presynaptic properties. Cholinergic input has been suggested to modulate hippocampal rhythmicity as well as episodic memory function. We therefore tested the effects of acetylcholine (ACh) on paired IPSCs and on spontaneous synaptic activity in interneurons and granule cells. We found no effect of ACh on paired IPSCs; however, spontaneous IPSCs recorded in granule cells were enhanced in amplitude and frequency. ACh potentiated spontaneous excitatory postsynaptic potentials (sEPSPs) and induced spiking in both types of interneuron, and preferentially increased sEPSP frequency in dendritic interneurons. Our findings suggest that patterns of activity in the two classes of interneurons, coupled with differences in their presynaptic properties, are likely to determine the roles of somatic and dendritic inhibition in network function.
我们比较了齿状回中两类经解剖学鉴定的中间神经元和颗粒细胞配对记录中的体细胞抑制和树突抑制。抑制性突触后电流（IPSC）的幅度和衰减在体细胞突触和树突突触处非常相似。树突突触处较慢的IPSC上升时间和较长的潜伏期与它们的远端位置一致，而无需突触后A型γ-氨基丁酸（GABA(A)）受体特性存在差异。相比之下，树突突触处较高的传递失败率和更大的双脉冲抑制表明体细胞抑制和树突抑制在突触前特性上有所不同。胆碱能输入已被认为可调节海马节律以及情景记忆功能。因此，我们测试了乙酰胆碱（ACh）对中间神经元和颗粒细胞中配对IPSCs以及自发突触活动的影响。我们发现ACh对配对IPSCs没有影响；然而，颗粒细胞中记录到的自发IPSCs在幅度和频率上有所增强。ACh增强了两种类型中间神经元中的自发兴奋性突触后电位（sEPSPs）并诱导了动作电位发放，并且优先增加了树突状中间神经元中sEPSP的频率。我们的研究结果表明，两类中间神经元的活动模式，再加上它们突触前特性的差异，可能决定了体细胞抑制和树突抑制在网络功能中的作用。
