Like other thalamic nuclei, the primate pulvinar is considered not to have long-range intrinsic connections, either excitatory or inhibitory. Injections of biotinylated dextran amine (BDA) in the medial pulvinar, however, reveal retrogradely filled neurons up to 2.0 mm from the injection edge. Serial section reconstruction (n = 18) confirmed that retrogradely filled neurons projected to the injection site and showed that they had additional long-range collaterals within the posterior pulvinar. Arrays of small, beaded terminations occurred in multiple foci along the collaterals. Terminal arrays were up to 1.0 mm in length; foci were separated by about 0.7 mm. Somata were large (average area = 220 microm2), and dendritic arbors were radiate and also large (about 1.0 mm in diameter), but without either the appendages of classical interneurons or the hairlike spines characteristic of radiate pulvinocortical projection neurons. Double labeling for BDA and parvalbumin (PV) or BDA and gamma-aminobutyric acid (GABA) indicated that these large neurons were positive for both PV and GABA. Double labeling for PV and GABA, or PV and glutamic acid decarboxylase 67 (GAD67) revealed a small number of similarly large neurons in the posterior pulvinar that were positive for both substances. Thus, we propose that these neurons are a novel class of inhibitory interneuron, longer range than the classic thalamic local circuit interneurons. Future questions include how these neurons relate to other inhibitory systems and specific postsynaptic populations and whether they are located preferentially within the posterior pulvinar, possibly related to the multimodal character of this thalamic region.

译文

与其他丘脑核一样,灵长类脉冲被认为不具有兴奋性或抑制性的远距离内在联系。然而,在内侧髓中注射生物素化的葡聚糖胺 (BDA) 显示出从注射边缘到2.0毫米的逆行填充的神经元。连续切片重建 (n = 18) 证实,逆行填充的神经元投射到注射部位,并显示它们在后牙髓内有其他远距离侧支。沿侧支的多个病灶中出现了一系列小的串珠末端。末端阵列的长度可达1.0毫米; 病灶间隔约0.7毫米。躯体很大 (平均面积 = 220 microm2),树突状乔木辐射且也很大 (直径约1.0毫米),但没有经典中间神经元的附属物或辐射的皮质投射神经元的毛状刺特征。BDA和小白蛋白 (PV) 或BDA和 γ-氨基丁酸 (GABA) 的双重标记表明,这些大神经元对PV和GABA均为阳性。对PV和GABA或PV和谷氨酸脱羧酶67 (GAD67) 的双重标记显示,后牙髓中少量类似的大神经元对两种物质均呈阳性。因此,我们建议这些神经元是一类新型的抑制性中间神经元,其范围比经典的丘脑局部电路中间神经元更长。未来的问题包括这些神经元与其他抑制系统和特定的突触后种群之间的关系,以及它们是否优先位于后牙髓内,这可能与该丘脑区域的多模式特征有关。

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