大鼠臂旁核内接受孤束核内脏传入之神经元同时接受中央杏仁核的反馈调节──溃变、HRP法结合包埋后免疫电镜研究

为研究来自孤束核的内脏传导信息在臂旁核水平是否接受中央杏仁核的反馈调节及其递质性质，以及孤束核—臂旁核—中央杏仁核传导通路中，在臂旁核水平是否接受ＧＡＢＡ的调节，本文将ＨＲＰ注入中央杏仁核进行顺、逆行标记，同时将兴奋性氨基酸毒素海人酸注入孤束核进行损毁，观实其顺行溃变终末，取外侧臂旁核超薄切片后结合抗ＧＡＢＡ的免疫电镜染色，观察发现有下列几种标记；（１）顺行溃变终末，所有的都与臂旁核神经元形成非对称性突触；（２）ＨＲＰ标记终末有两类：第一类和臂旁核神经元形成对称性突触，占ＨＲＰ标记终末总数的８０％以上，第二类与臂旁核神经元形成非对称性突触，另外有大量的ＨＲＰ标记的胞体和树突；（３）胶体金标记的ＧＡＢＡ阳性终末，皆与突触后结构形成对称性突触；（４）ＧＡＢＡ／ＨＲＰ双标记终末，具有ＧＡＢＡ免疫阳性终末和第一类ＨＲＰ标记终末的共同特征。上述几种标记在臂旁核内有以下几种关系：（１）溃变终末和ＧＡＢＡ阳性终末与同一个ＨＲＰ标记或非标记的突形成轴－树突触；（２）溃变终末和第一类ＨＲＰ标记终末共同终止于同一非标记讨突；（３）溃变终末与ＨＲＰ标记树突或胞位形成非对称性突触；（４）ＧＡＢＡ／ＨＲＰ双标记终末与非标记树突或胞体?

NEURONS IN THE PARABRACHIAL NUCLEUS RECEIVE TERMINALS FROM BOTH SOLITARY NUCLEUS AND CENTRAL AMYGDALOID NUCLEUS

To study whether the central amygdaloid nucleus (Ce) detscending axons innervate the parabrachial neurons receiving the afferents from the caudal nucleus of solitary tract (NTS), we combined anterograde axonal transport of HRP and anterograde degeneration with postembedding immunogold staining for GABA. The animals received ingrtion of HRP in the Ce,and an injection of kainic acid in the NTS as a lesioning agent on the same side. Under the level of electron microscopy, it was found that the HRP-labeled axonal terminals formed two types of synaptic contacts, asymmetric and symmetric ones, with the unlabeled neuronal bodies or dendrites in the lateral parabrachial nucleus, in which the symmetric synapse was preponderant. Dendrites and cell bodies labeled with HRP were also observed. The degenerating axonal terminals (DA) from the NTS always formed the asymmetric synapses with parabrachial neurons. The HRP labeled terminals and DA were found to converge on the same neuronal dendrites of the PBN. After being immnuostained with GABA antiserum, most of the HRP-labeled axonal terminals were also. labeled with colloidal gold-HRP/GABA double labellings. Those terminals formed symmetric synaptic contacts with dendrites and cell bodies of the neurons in the PBN. Some unlabeled dendrites received both afferents of degenerating axonal terminals from the NTS and the GABA immunoreactive terminals. Furthermore, we have found that the HRP/GABA double labeled terminals and the DA make the synaptic contacts with same unlabeled dendrites in the PBV.In addition, the HRP labeled neurons projecting to Ce received both DA afferents from the NTS and the GABA-IR terminals. The present research shows, first, GABA terminals regulate the visceral transmission in the pathway of NTS-PBN-Ce at the level of PBV; second, the Ce-originated GABAergic terminals may also influence the PBN and regulate the viseceral afferents from the NTS through a feedback mechanism.