大鼠中脑水管周围灰质各分区向下丘脑orexin阳性神经元分布区的投射及其联系

摘要

Objective:To investigate the organization of projections from different subdivisions of the periaqueductal gray (PAG) to orexin-containing neurons in the hypothalamus and to reveal the morphological basis for the modulatory effects of the PAG innervations on orexin-containing neurons in rats.Methods:Cholera toxin B subunit (CTb) injections were made into the orexin-containing neurons field in the hypothalamus of rats and the distributions of CTb-immunoreactive (ir) neurons in the PAG were observed under a light microscope.An combination of biotinylated dextran amine (BDA) injection into different subdivisions of PAG and immunostaining for orexin-containing neurons was implemented,the distribution of BDA-labeled fibers and the orexin-ir neurons was observed in the hypothalamus.Results:After an unilateral CTb injection into suprafornical area or lateral hypothlamus,numerous CTb-ir neurons were observed bilaterally with a ipsilateral predominance in the PAG.The lateral PAG (lPAG) and ventrolateral PAG (vlPAG) contained a large number of CTb-ir neurons,while dorsolateral PAG (dlPAG) and dorsomedial PAG (dmPAG) contained a few labeled neurons.A small number of CTb-ir neurons were seen in the contralateral portions of PAG.After BDA injection into dlPAG,lPAG and vlPAG respectively and immunostaining of orexin-containing neurons,BDA-labeled fibers were observed bilaterally with a clear-cut ipsilateral predominance in the hypothalamus.The prominent overlap of the distribution field of the BDA-labeled fibers and that of the orexin-ir neurons were found in the suprafornical area.In this area,bouton-like varicosities labeled with BDA from lPAG and vlPAG were often closely apposed to cell bodies and dendrites of the orexin-ir neurons.Very sparse apposition of those BDA labeled fibers from dlPAG and orexin-ir neurons were found.Conclusion:Fibers from lPAG and vlPAG and orexin-ir neurons in the suprafornical area of the hypothalamus are overlapping and are closely connected,which may directly affect the functions of orexin-containing neurons.%目的:观察大鼠中脑水管周围灰质(PAG)不同分区神经元发出的投射纤维与下丘脑orexin阳性神经元之间的联系,阐明PAG不同分区神经元支配下丘脑orexin阳性神经元的形态学基础.方法:首先将逆行示踪剂霍乱毒素B(CTb)注射到下丘脑orexin阳性神经元胞体分布区域,免疫组织化学显色观察PAG内CTb逆行标记神经元的分布特点;再将顺行示踪剂生物素化葡聚糖胺(BDA)注射到PAG不同分区,采用免疫组织化学双标记的方法,在下丘脑内观察BDA标记神经纤维及其终末与orexin阳性神经元的重叠分布特点和它们之间的联系.结果:将CTb注射到单侧下丘脑穹窿上区或外侧区后,在注射点同侧PAG的外侧区(lPAG)和腹外侧区(vlPAG)可见大量CTb逆标神经元,背外侧区(dlPAG)及背内侧区(dmPAG)仅见少量标记神经元.注射点对侧PAG区域也可观察到少量CTb标记神经元.将BDA分别注射到单侧dlPAG、lPAG和vlPAG后,在下丘脑双侧均可观察到BDA顺标纤维及其终末,但注射点同侧BDA标记纤维和终末的数量明显多于对侧.源自lPAG和vlPAG的BDA标记纤维及其终末与orexin神经元胞体在穹窿上区形成明确的重叠分布和密切接触,而源自dlPAG的纤维少见与orexin神经元接触.结论:lPAG及vlPAG来源的纤维及其终末与下丘脑内的orexin阳性神经元的分布区域重叠并形成密切接触,可能直接影响orexin神经元的功能.