Alonso G
INSERM U 336, Université de Montpellier II, France.
J Chem Neuroanat. 1993 Mar-Apr;6(2):55-67. doi: 10.1016/0891-0618(93)90028-3.
The parvicellular compartments of the paraventricular nucleus of the hypothalamus (pPVN) contains particularly high concentrations of neuropeptide (NPY)-containing fibres of two main cellular origins including (i) neurons of the medulla oblongata, most of which co-store phenylethanolamine-N-methyltransferase (PNMT), the enzyme characterizing adrenergic neurons, and (ii) non-catecholaminergic neurons of the mediobasal hypothalamus. The aim of the present study is to compare the fine organization of the two types of axons terminating in the pPVN. Immunocytochemistry at light and electron microscope levels was used to study both the density and the ultrastructural organization of NPY- and PNMT-immunoreactive fibres in the pPVN of animals bearing surgical lesions disrupting axonal pathways from the hindbrain or from the sublying mediobasal hypothalamus. The brainstem knife-cut induced a strong decrease (65%) in the numerical density of PNMT fibres innervating the pPVN, but was without significant effects on the density of NPY fibres. On the other hand, the hypothalamic knife-cut induced an 80% decrease in the density of NPY fibres within the PVN without affecting the number of PNMT fibres. The electron microscope study showed that in the control pPVN contralateral to the lesions, the majority (64%) of PNMT synapses were asymmetric axo-dendritic synapses, whereas the majority (67%) of NPY synapses form symmetric contacts with both dendrites and perikarya of the hypothalamic nucleus. By contrast, after a hypothalamic knife-cut, the majority (66%) of NPY synapses identified in the pPVN exhibited features of asymmetric synapses. These data indicate that the large majority of NPY-immunoreactive fibres detected within the pPVN arise from non-catecholaminergic neurons located in the mediobasal hypothalamus and mainly form symmetric synapses on neurons of the pPVN, whereas only a minority of them arise from hindbrain regions, and like PNMT fibres innervating this nucleus preferentially form asymmetric axo-dendritic synapses.
下丘脑室旁核的小细胞区（pPVN）含有特别高浓度的神经肽Y（NPY）纤维，这些纤维主要来自两种细胞：（i）延髓神经元，其中大多数共同储存苯乙醇胺-N-甲基转移酶（PNMT），该酶是肾上腺素能神经元的特征性酶；（ii）中基底下丘脑的非儿茶酚胺能神经元。本研究的目的是比较终止于pPVN的两种轴突的精细组织结构。利用光镜和电镜水平的免疫细胞化学技术，研究了患有手术损伤破坏了来自后脑或下方中基底下丘脑轴突通路的动物pPVN中NPY和PNMT免疫反应性纤维的密度和超微结构组织。脑干切断术导致支配pPVN的PNMT纤维的数量密度显著降低（65%），但对NPY纤维的密度没有显著影响。另一方面，下丘脑切断术导致PVN内NPY纤维的密度降低80%，而不影响PNMT纤维的数量。电镜研究表明，在与损伤对侧的对照pPVN中，大多数（64%）的PNMT突触是不对称的轴-树突触，而大多数（67%）的NPY突触与下丘脑核的树突和胞体形成对称接触。相比之下，下丘脑切断术后，在pPVN中鉴定出的大多数（66%）NPY突触表现出不对称突触的特征。这些数据表明，在pPVN内检测到的绝大多数NPY免疫反应性纤维来自位于中基底下丘脑的非儿茶酚胺能神经元，并且主要在pPVN的神经元上形成对称突触，而其中只有少数来自后脑区域，并且与支配该核的PNMT纤维一样，优先形成不对称的轴-树突触。
