Jacomy H, Bosler O
Laboratoire de Neuroendocrinologie Expérimentale, INSERM, U297, Institut Fédératif Jean-Roche, Faculté de Médecine, Marseille, France.
J Neurocytol. 1996 Nov;25(11):659-73. doi: 10.1007/BF02284832.
Light- and electron-microscopic immunocytochemistry was used to investigate grafts of foetal hypothalamic tissue implanted close to the site of the suprachiasmatic nucleus in adult rats with bilateral surgical ablation of this nucleus. The transplants contained vasoactive intestinal peptide and vasopressin cell clusters, which have previously been shown to characterize functional suprachiasmatic nucleus grafts. Vasoactive intestinal peptide and vasopressin neurons presented synaptic features that have not been described in the native suprachiasmatic nucleus. More specifically, their terminals within the graft were involved in 'double' synapses with separate unlabelled dendrites. Moreover, in dually stained sections, an unexpected synaptic investment of vasoactive intestinal peptide neurons by vasopressin endings was detected, which revealed reversed vasoactive intestinal peptide/vasopressin interactions compared to those described in the native nucleus. These observations could reflect some immature features of the grafted neurons. Ultrastructural relationships of monoaminergic fibres arising from host and/or intragraft neurons were also examined. Within the engrafted suprachiasmatic nucleus, tyrosine hydroxylase-labelled fibres, which probably belonged to cografted dopaminergic neurons, showed normal patterns of distribution and synaptic connections, with no preferential relationships with vasoactive intestinal peptide or vasopressin neurons. Serotoninergic axons arborized within transplants but, in agreement with previous data showing an inhibitory influence of the suprachiasmatic nucleus on ingrowing serotoninergic fibres, they had no predilection for the area corresponding to that nucleus. In spite of their relative scarcity, serotoninergic fibres within the engrafted suprachiasmatic nucleus showed an almost normal synaptic incidence, but synapses were not predominantly shared with the vasoactive intestinal peptide neurons, known to be their major targets in the native nucleus. This may contribute not only to the failure of functional grafts to synchronize with environmental conditions, but also to the inability of transplants to restore hormonal rhythms such as estrous cyclicity.
利用光镜和电镜免疫细胞化学技术，对成年大鼠双侧视交叉上核手术切除后，将胎儿下丘脑组织移植到靠近视交叉上核部位的移植物进行研究。移植组织中含有血管活性肠肽和加压素细胞簇，先前已证明这些细胞簇是功能性视交叉上核移植物的特征。血管活性肠肽和加压素神经元呈现出在天然视交叉上核中未被描述的突触特征。更具体地说，它们在移植物内的终末与单独的未标记树突形成“双”突触。此外，在双重染色切片中，检测到加压素终末对血管活性肠肽神经元的意外突触支配，这揭示了与天然核中描述的血管活性肠肽/加压素相互作用相反的情况。这些观察结果可能反映了移植神经元的一些不成熟特征。还研究了源自宿主和/或移植物内神经元的单胺能纤维的超微结构关系。在移植的视交叉上核内，酪氨酸羟化酶标记的纤维可能属于共移植的多巴胺能神经元，其分布和突触连接模式正常，与血管活性肠肽或加压素神经元没有优先关系。5-羟色胺能轴突在移植物内形成分支，但与先前显示视交叉上核对生长中的5-羟色胺能纤维有抑制作用的数据一致，它们对与该核相对应的区域没有偏好。尽管移植的视交叉上核内的5-羟色胺能纤维相对稀少，但它们的突触发生率几乎正常，但突触并不主要与血管活性肠肽神经元共享，而血管活性肠肽神经元在天然核中是它们的主要靶点。这不仅可能导致功能性移植物无法与环境条件同步，还可能导致移植组织无法恢复诸如发情周期等激素节律。
