Department of Neuroscience, Karolinska Institute, Stockholm, Sweden.
J Neurosci. 2010 Mar 3;30(9):3499-507. doi: 10.1523/JNEUROSCI.5139-09.2010.
The intrastriatal microcircuit is a predominantly inhibitory GABAergic network comprised of a majority of projection neurons [medium spiny neurons (MSNs)] and a minority of interneurons. The connectivity within this microcircuit is divided into two main categories: lateral connectivity between MSNs, and inhibition mediated by interneurons, in particular fast spiking (FS) cells. To understand the operation of striatum, it is essential to have a good description of the dynamic properties of these respective pathways and how they affect different types of striatal projection neurons. We recorded from neuronal pairs, triplets, and quadruplets in slices of rat and mouse striatum and analyzed the dynamics of synaptic transmission between MSNs and FS cells. Retrograde fluorescent labeling and transgenic EGFP (enhanced green fluorescent protein) mice were used to distinguish between MSNs of the direct (striatonigral) and indirect (striatopallidal) pathways. Presynaptic neurons were stimulated with trains of action potentials, and activity-dependent depression and facilitation of synaptic efficacy was recorded from postsynaptic neurons. We found that FS cells provide a strong and homogeneously depressing inhibition of both striatonigral and striatopallidal MSN types. Moreover, individual FS cells are connected to MSNs of both types. In contrast, both MSN types receive sparse and variable, depressing and facilitating synaptic transmission from nearby MSNs. The connection probability was higher for pairs with presynaptic striatopallidal MSNs; however, the variability in synaptic dynamics did not depend on the types of interconnected MSNs. The differences between the two inhibitory pathways were clear in both species and at different developmental stages. Our findings show that the two intrastriatal inhibitory pathways have fundamentally different dynamic properties that are, however, similarly applied to both direct and indirect striatal projections.
纹状体的内微电路主要是由大多数投射神经元[中等棘突神经元 (MSNs)]和少数中间神经元组成的 GABA 能抑制性网络。该微电路中的连接分为两类：MSN 之间的侧连接，以及中间神经元介导的抑制，特别是快速放电 (FS) 细胞。要了解纹状体的运作，必须对这些不同通路的动态特性及其对不同类型的纹状投射神经元的影响有很好的描述。我们在大鼠和小鼠纹状体切片中记录了神经元对、三神经元组和四神经元组，并分析了 MSN 和 FS 细胞之间突触传递的动力学。逆行荧光标记和转 EGFP（增强型绿色荧光蛋白）小鼠用于区分直接（纹状体黑质）和间接（纹状体苍白球）通路的 MSN。用动作电位串刺激前神经元，并从前神经元记录突触效能的活动依赖性抑制和易化。我们发现 FS 细胞对两种 MSN 类型（纹状体黑质和纹状体苍白球）都提供了强大且均匀的抑制作用。此外，单个 FS 细胞与两种类型的 MSN 都有连接。相比之下，两种 MSN 类型都从附近的 MSN 接收稀疏且可变的抑制性和易化性突触传递。具有前纹状体苍白球 MSN 的神经元对的连接概率更高；然而，突触动力学的可变性不取决于相互连接的 MSN 类型。两种抑制性通路之间的差异在两种物种和不同发育阶段都很明显。我们的研究结果表明，两种纹状体内抑制性通路具有根本不同的动态特性，但同样适用于直接和间接的纹状投射。
