Department of Oral Anatomy and Neurobiology, Osaka University Graduate School of Dentistry, Suita, Osaka, 565-0871, Japan.
Department of Orthodontics and Dentofacial Orthopedics, Osaka University Graduate School of Dentistry, Suita, Osaka, 565-0871, Japan.
Brain Struct Funct. 2021 May;226(4):1115-1133. doi: 10.1007/s00429-021-02228-5. Epub 2021 Feb 4.
The oval paracentral nucleus (OPC) was initially isolated from the paracentral nucleus (PC) within the intralaminar thalamic nuclei in rats. We have recently shown that the rat OPC receives proprioceptive inputs from jaw-closing muscle spindles (JCMSs). However, it remains unknown which cortical areas receive thalamic inputs from the OPC, and whether the cortical areas receiving the OPC inputs are distinct from those receiving inputs from the other intralaminar nuclei and sensory thalamic nuclei. To address this issue, we injected an anterograde tracer, biotinylated dextranamine (BDA), into the OPC, which was electrophysiologically identified by recording of proprioceptive inputs from the JCMSs. Many BDA-labeled axonal fibers and terminals from the OPC were ipsilaterally observed in the rostral and rostroventral regions of the primary somatosensory cortex (S1), the rostral region of the secondary somatosensory cortex (S2), and the most rostrocaudal levels of the granular insular cortex (GI). In contrast, a BDA injection into the caudal PC, which was located slightly rostral to the OPC, resulted in ipsilateral labeling of axonal fibers and terminals in the rostrolateral region of the medial agranular cortex and the rostromedial region of the lateral agranular cortex. Furthermore, injections of a retrograde tracer, Fluorogold, into these S1, S2, and GI regions, resulted in preferential labeling of neurons in the ipsilateral OPC among the intralaminar and sensory thalamic nuclei. These findings reveal that the rat OPC has widespread, but strong corticopetal projections, indicating that there exist divergent corticopetal pathways from the intralaminar thalamic nucleus, which process JCMS proprioceptive sensation.
卵圆旁中央核（OPC）最初是从大鼠的板内核内的旁中央核（PC）中分离出来的。我们最近表明，大鼠 OPC 接收来自闭口肌梭（JCMS）的本体感受输入。然而，尚不清楚哪些皮质区域从 OPC 接收丘脑输入，以及接收 OPC 输入的皮质区域是否与接收来自其他板内核和感觉丘脑核的输入的皮质区域不同。为了解决这个问题，我们将顺行示踪剂，生物素化葡聚糖胺（BDA）注射到 OPC 中，通过记录来自 JCMS 的本体感受输入来电生理鉴定 OPC。在初级体感皮层（S1）的前侧和前侧区域、次级体感皮层（S2）的前侧区域以及颗粒状岛叶皮层（GI）的最前尾侧水平，观察到许多来自 OPC 的 BDA 标记的轴突纤维和末梢在同侧。相比之下，将 BDA 注射到略位于 OPC 上方的尾侧 PC 中，导致同侧标记的轴突纤维和末梢在外侧颗粒状皮质的外侧区域和外侧颗粒状皮质的前内侧区域。此外，将逆行示踪剂，荧光金，注射到这些 S1、S2 和 GI 区域中，导致同侧 OPC 中的神经元优先标记，其中包括板内核和感觉丘脑核。这些发现表明，大鼠 OPC 具有广泛但强烈的皮质投射，表明存在来自板内核的发散的皮质投射途径，该途径处理 JCMS 本体感受感觉。
