Terman J R, Wang X M, Martin G F
Department of Cell Biology, Neurobiology, and Anatomy, College of Medicine, The Ohio State University, Columbus 43210, USA.
Anat Rec. 1998 Aug;251(4):528-47. doi: 10.1002/(SICI)1097-0185(199808)251:4<528::AID-AR9>3.0.CO;2-N.
Spinocerebellar axons have been studied extensively in placental mammals, but there have been no full reports on their origin, laterality, or spinal course in any marsupial. We have used the North American opossum (Didelphis virginiana) to obtain such information and to ask whether any spinocerebellar neurons innervate both the anterior and posterior lobes of the cerebellum through axonal collaterals. To identify spinal neurons that project to the cerebellum, we employed the retrograde transport of Fluoro-Gold (FG) from the anterior lobe, the main target of spinocerebellar axons. In some cases, cerebellar injections of FG were combined with hemisections of the rostral cervical or midthoracic spinal cord, so that laterality of spinocerebellar connections could be established. To determine whether single neurons project to both the anterior lobe and the posterior lobe, injections of Fast Blue (FB) into the anterior lobe were combined with injections of Diamidino yellow (DY) or rhodamine B dextran (RBD) into the posterior lobe, or vice versa. Following injections of FG into the anterior lobe, neurons were labeled throughout the length of the spinal cord, which differed in laminar distribution and laterality of their projections. Among other areas, neurons were labeled in the central cervical nucleus, the nucleus centrobasalis, Clarke's nucleus, the dorsal horn dorsal spinocerebellar tract area, the spinal border region, and Stilling's nucleus. When anterior lobe injections of FB were combined with injections of RBD or DY into the posterior lobe, or vice versa, some double-labeled neurons were present in all major spinocerebellar groups. Cerebellar injections of FG also retrogradely labeled spinocerebellar axons, allowing us to document their locations in the gray matter as well as within the periphery of the lateral and ventral funiculi at all spinal levels. A few spinocerebellar axons also were found in the dorsal funiculus (a dorsal column-spinocerebellar tract), which appeared to originate from neurons in the dorsal part of Clarke's nucleus from the ninth thoracic segment to the first lumbar segment. Our results indicate that spinocerebellar axons in the marsupial opossum are generally comparable in origin, course, and laterality to the same axons in the placental mammals studied to date.
在胎盘哺乳动物中，脊髓小脑轴突已得到广泛研究，但在任何有袋动物中，关于它们的起源、侧别或脊髓走行都没有完整的报告。我们利用北美负鼠（弗吉尼亚负鼠）来获取此类信息，并探究是否有脊髓小脑神经元通过轴突侧支支配小脑的前叶和后叶。为了识别投射到小脑的脊髓神经元，我们采用了从脊髓小脑轴突的主要靶标前叶逆行运输荧光金（FG）的方法。在某些情况下，将FG注入小脑与颈髓上段或胸髓中段半横切相结合，以便确定脊髓小脑连接的侧别。为了确定单个神经元是否投射到前叶和后叶，将快蓝（FB）注入前叶与将双脒基黄（DY）或罗丹明B葡聚糖（RBD）注入后叶相结合，反之亦然。将FG注入前叶后，在整个脊髓长度上都标记到了神经元，它们在层状分布和投射侧别上存在差异。在其他区域中，在颈中央核、中央基底核、克拉克核、背角背侧脊髓小脑束区、脊髓边界区和施蒂林核中标记到了神经元。当将前叶注射FB与向后叶注射RBD或DY相结合时，反之亦然，在所有主要的脊髓小脑组中都发现了一些双标记神经元。向小脑注射FG也逆行标记了脊髓小脑轴突，使我们能够记录它们在灰质以及所有脊髓节段外侧索和腹侧索周边的位置。在背侧索（背柱 - 脊髓小脑束）中也发现了一些脊髓小脑轴突，它们似乎起源于第九胸段至第一腰段克拉克核背侧部分的神经元。我们的结果表明，有袋动物负鼠的脊髓小脑轴突在起源、走行和侧别上通常与迄今为止研究的胎盘哺乳动物中的相同轴突相当。
