Inter- and intralaminar subcircuits of excitatory and inhibitory neurons in layer 6a of the rat barrel cortex
Inter- and intralaminar subcircuits of excitatory and inhibitory neurons in layer 6a of the rat barrel cortex
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DOI：
10.1152/jn.90684.2008
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发表时间：
2008-10-01
影响因子：
2.5
通讯作者：
Ohana, Ora
中科院分区：
文献类型：
--
作者：
Kumar, Pratap;Ohana, Ora
大鼠桶状皮层第 6 层 (L6) 中大约一半的兴奋性神经元投射到丘脑，轴突侧支在颗粒状 L4 中分叉；皮质内的其余项目，其侧枝仅限于颗粒下层。类似地，L6抑制性神经元还包括局部树状神经元和层间投射神经元。我们检查了参与不同层流相互作用的 L6 神经元在形态和电学上是否也不同。通过将逆行运输的荧光示踪剂体内注射到初级丘脑核中来标记皮质丘脑（CT）神经元。对幼年大鼠脑切片中标记和未标记的 L6 神经元进行全细胞电流钳记录；随后细胞的形态被恢复和重建。皮质 (CC) 神经元与 CT 细胞的区别在于，其不存在皮质下投射，且其轴突侧枝主要呈颗粒内树状化。根据顶端树突的结构，可以进一步区分两种形态学 CC 亚型。在电学方面，CT 神经元具有较短的膜时间常数和动作电位 (AP) 持续时间以及较高的流变碱电流。 CC 神经元在持续去极化时发射高频尖峰双联体或三联体；突发频率也区分了两种形态学 CC 亚型。在抑制性 L6 细胞中，L4 投射 (L6i(L4)) 和局部 (L6i(L6)) 抑制性神经元也具有对比的放电特性。 L6i(L4) 神经元具有更宽的 AP 和更低的最大放电率。我们提出，投射到 L4 的 L6 兴奋性和抑制性神经元构成了其连接性和放电模式与粒下网络不同的专门子电路。
Approximately half the excitatory neurons in layer 6 (L6) of the rat barrel cortex project to the thalamus with axon collaterals ramifying in the granular L4; the remaining project within cortex with collaterals restricted to infragranular laminae. In analogy, L6 inhibitory neurons also include locally arborizing and inter-laminar projecting neurons. We examined whether L6 neurons participating in different laminar interactions were also morphologically and electrically distinct. Corticothalamic (CT) neurons were labeled by in vivo injections of a retrogradely transported fluorescent tracer into the primary thalamic nucleus. Whole cell current-clamp recordings were performed from labeled and unlabeled L6 neurons in brain slices of juvenile rats; the morphology of cells was subsequently recovered and reconstructed. Corticocortical (CC) neurons were distinguished from CT cells based on the absence of a subcortical projection and the predominantly infragranular arborization of their axon collaterals. Two morphological CC subtypes could be further distinguished based on the structure of their apical dendrite. Electrically, CT neurons had shorter membrane time-constants and action potential (AP) durations and higher rheobase currents. CC neurons fired high-frequency spike doublets or triplets on sustained depolarization; the burst frequency also distinguished the two morphological CC subtypes. Among inhibitory L6 cells, the L4-projecting (L6i(L4)) and local (L6i(L6)) inhibitory neurons also had contrasting firing properties; L6i(L4) neurons had broader APs and lower maximal firing rates. We propose that L6 excitatory and inhibitory neurons projecting to L4 constitute specialized subcircuits distinct from the infragranular network in their connectivity and firing patterns.