Smith Y, Paré J F, Paré D
Yerkes Regional Primate Research Center, Atlanta, Georgia 30329, USA.
J Comp Neurol. 2000 Jan 24;416(4):496-508.
In the basolateral (BL) amygdaloid complex, the excitability of projection cells is regulated by intrinsic inhibitory interneurons using gamma-aminobutyric acid (GABA) as a transmitter. A subset of these cells are labeled in a Golgi-like manner by Parvalbumin (PV) immunohistochemistry. Recently, we have shown that the overwhelming majority of axon terminals contacting these PV-immunoreactive neurons form asymmetric synapses. The present study was undertaken to identify the source(s) of these inputs. Since previous work had revealed that thalamic axons form very few synapses on BL interneurons (< 1%), we focused on cortical and intra-amygdaloid inputs. Iontophoretic injections of the anterograde tracers Phaseolus vulgaris-leucoagglutinin or biotinylated dextran amine were performed in various cortical fields in cats (perirhinal, entorhinal, pre/infralimbic cortices) and monkeys (orbitofrontal region) or in the BL amygdaloid nucleus in cats. These injections resulted in a large number of anterogradely labeled terminals forming asymmetric synapses in the BL complex. Following cortical injections, numerous anterogradely labeled terminals were found in the vicinity of PV-immunoreactive interneurons in the BL amygdala. However, only approximately 1% of these terminals formed synaptic contacts with PV-immunoreactive profiles. In contrast, as many as 11% of the terminals contributed by the intranuclear axon collaterals of BL projection cells established synapses with PV-immunoreactive elements. Since the axon terminals of PV-immunoreactive interneurons are enriched in GABA and they exclusively form symmetric synapses, these results suggest that PV-immunoreactive interneurons are predominantly involved in feedback inhibition in the BL amygdaloid complex.
在基底外侧杏仁核复合体中，投射细胞的兴奋性由使用γ-氨基丁酸（GABA）作为神经递质的内在抑制性中间神经元调节。这些细胞的一个亚群通过小白蛋白（PV）免疫组织化学以类似高尔基染色的方式被标记。最近，我们已经表明，与这些PV免疫反应性神经元接触的绝大多数轴突终末形成不对称突触。本研究旨在确定这些输入的来源。由于先前的工作已经表明丘脑轴突在基底外侧中间神经元上形成的突触非常少（<1%），我们将重点放在皮质和杏仁核内的输入上。在猫的各个皮质区域（梨状周皮质、内嗅皮质、前/内嗅下皮质）和猴子的（眶额区域）或猫的基底外侧杏仁核中进行离子电渗法注射顺行示踪剂菜豆白细胞凝集素或生物素化葡聚糖胺。这些注射导致大量顺行标记的终末在基底外侧复合体中形成不对称突触。皮质注射后，在基底外侧杏仁核中PV免疫反应性中间神经元附近发现了大量顺行标记的终末。然而，这些终末中只有约1%与PV免疫反应性轮廓形成突触联系。相比之下，基底外侧投射细胞的核内轴突侧支贡献的终末中有多达11%与PV免疫反应性元件建立了突触。由于PV免疫反应性中间神经元的轴突终末富含GABA且它们仅形成对称突触，这些结果表明PV免疫反应性中间神经元主要参与基底外侧杏仁核复合体中的反馈抑制。
