Division of Cerebral Circuitry, National Institute for Physiological Sciences, Graduate University for Advanced Studies (SOKENDAI), Okazaki, 444-8787, Japan.
J Neurosci. 2011 Jul 13;31(28):10380-91. doi: 10.1523/JNEUROSCI.0772-11.2011.
Pyramidal cells in the neocortex are differentiated into several subgroups based on their extracortical projection targets. However, little is known regarding the relative intracortical connectivity of pyramidal neurons specialized for these specific output channels. We used paired recordings and quantitative morphological analysis to reveal distinct synaptic transmission properties, connection patterns, and morphological differentiation correlated with heterogeneous thalamic input to two different groups of pyramidal cells residing in layer 5 (L5) of rat frontal cortex. Retrograde tracers were used to label two projection subtypes in L5: crossed-corticostriatal (CCS) cells projecting to both sides of the striatum, and corticopontine (CPn) cells projecting to the ipsilateral pons. Although CPn/CPn and CCS/CCS pairs had similar connection probabilities, CPn/CPn pairs exhibited greater reciprocal connectivity, stronger unitary synaptic transmission, and more facilitation of paired-pulse responses. These synaptic characteristics were strongly correlated to the projection subtype of the presynaptic neuron. CPn and CCS cells were further differentiated according to their somatic position (L5a and L5b, the latter denser thalamic afferent fibers) and their dendritic/axonal arborizations. Together, our data demonstrate that the pyramidal projection system is segregated into different output channels according to subcortical target and thalamic input, and that information flow within and between these channels is selectively organized.
大脑新皮质中的锥体神经元根据其皮质外投射目标可分为几个亚群。然而，对于专门用于这些特定输出通道的锥体神经元的相对皮质内连接，人们知之甚少。我们使用成对记录和定量形态分析来揭示与两种不同的锥体神经元群相关的独特的突触传递特性、连接模式和形态分化，这些神经元群位于大鼠前额皮质的第 5 层（L5）。逆行示踪剂用于标记 L5 中的两种投射亚型：投射到纹状体两侧的交叉皮质纹状体（CCS）细胞，以及投射到同侧脑桥的皮质脑桥（CPn）细胞。尽管 CPn/CPn 和 CCS/CCS 对具有相似的连接概率，但 CPn/CPn 对表现出更强的相互连接、更强的单位突触传递和更强的成对脉冲反应易化。这些突触特征与前突神经元的投射亚型强烈相关。CPn 和 CCS 细胞根据其体细胞位置（L5a 和 L5b，后者有更密集的丘脑传入纤维）和其树突/轴突分支进一步分化。总之，我们的数据表明，锥体投射系统根据皮质下靶标和丘脑输入分为不同的输出通道，并且这些通道内和之间的信息流是选择性组织的。
