鸡脑干下行投射至脊髓的神经元分布

本文采用在鸡脊髓颈段注射HRP或埋HRP胶块,然后用TMB处理的方法,对中枢神经系统中下行纤维至脊髓的神经元分布进行了研究。观察到鸟类动物存在着一些与哺乳类动物卡相似的神经联系。在间脑部分,下丘脑室旁核大细胞(PVM)是标记细胞较密集的区域,其他还有下丘脑的外细胞层(SE)和内细胞展(SI)以及下丘脑外侧区。中枢内的标记细胞主要集中于红核、中介核和丘间核(ICo)。在延、桥脑段,网状脊髓束是主要的下行通路,脑桥吻端网状核(RPO)和脑桥尾侧网状核(RP)向脊髓的投射相当于哺乳类动物的内侧网状下行系统。小细胞网状核(Rpc)、旁巨细胞网状核等都有下行至脊髓的纤维。另外,蓝斑、蓝斑下核、前庭核、孤束核、外楔核也都有下行纤维向脊髓投射。在中缝核群中我们观察到大量的标记细胞,所以在鸟类动物中可能也存在着中缝核—脊髓这一下行抑制系统。

CELLS OF ORIGIN OF DESCENDING SPINAL PROJECTION IN THE CHICKEN

Descending pathways from the brain stem to the spinal cord were studied in chicken, by means of retrograde, transport of horseradish peroxidase(HRP), Following the injection of HRP into the cervical spinal cord (C3 or C12) the distribution of labeled neurons was examined. Some connections comparable to those of mammals were demonstrated in chicken. In the diencephalon most labeled neurons were found in nucleus Periventricularis magnocellularis, a few in stratum cellulare externu, m and stratum cellulare internum, and also in lateral hypothalamic area. A number of descending pathways were originated from the mesencephalon. Labeled neurons were seen in nucleus ruber and nucleus interstitialis (Cajal). Some cells were labeled in nucleus intercollicularis after injecting HRP into upper cervical cord (C3). The major descending pathway from the lower brainstem was the reticulospinal fibers. The descending fibers from the nucleus reticularis pontis oralis and nucleus reticularis pontis caudalis to the spinal cord might correspond to the mammalian medial reticular descending system and those from the nucleus reticularis gigantocellularis could be considered as the lateral reticular descendisg system in mammals. The nucleus reticularis parvocellularis and nucleus paragigantocellularis lateralis gave off only a few fibers to the spinal cord. Other nuclei giving rise to the descending spinal projections were nucleus vestibularis, nucleus solitarius, nucleus cuneatus externus, locus ceruleus and nucleus subceruleus. A moderate number of labeled neurons were located in the nucleus raphe. Therefore there might also exist a raphe-spinal descending inhibitory system in bird.