Chadaram S R, Laskowski M B
WWAMI Medical Education Program and Department of Biological Sciences, University of Idaho, P.O. Box 444207, Moscow, Idaho 83844-4207, USA.
J Neurobiol. 2003 Sep 15;56(4):347-59. doi: 10.1002/neu.10240.
The rostrocaudal position of neurons within the spinal motor pool maps systematically onto the surface of several muscles in mammals. In an effort to understand the mechanisms that generate such maps, we have been studying choices made by embryonic spinal cord neurons on muscle membrane substrates in the in vitro stripe assay. In this report we explore the effects of postnatal age of the muscle on neurite choice, and how prior denervation modifies this choice. Our results further differentiate rostral from caudal motor neurons in preferring one substrate to another. First, caudal neurites prefer to grow on P6 neonatal caudal over rostral membranes, but lose this ability to distinguish axial position of origin in older muscles. Rostral neurites prefer growth on rostral membranes, but this preference also diminishes with age. Second, when adult muscles have been denervated, both rostral and caudal neurites regain their positional growth selectivity. Third, caudal neurites are particularly sensitive to substrate choice. When growing on a preferred substrate (gluteus) caudal neurites prefer neonatal over adult membranes. These results support the concept of fundamental differences in the growth preferences of rostral and caudal spinal neurites. These differences will assist in the identification of molecular guidance cues that determine the formation of neuromuscular positional maps.
在哺乳动物中，脊髓运动神经元池内神经元的头尾位置系统地映射到几块肌肉的表面。为了理解产生这种映射的机制，我们一直在体外条纹试验中研究胚胎脊髓神经元在肌膜底物上的选择。在本报告中，我们探讨了肌肉出生后的年龄对神经突选择的影响，以及先前的去神经支配如何改变这种选择。我们的结果进一步区分了头侧和尾侧运动神经元在偏好一种底物而非另一种底物方面的差异。首先，尾侧神经突在P6新生尾侧肌膜上比头侧肌膜上更倾向于生长，但在较老的肌肉中失去了区分起源轴向位置的能力。头侧神经突在头侧肌膜上更倾向于生长，但这种偏好也随着年龄的增长而减弱。其次，当成年肌肉去神经支配后，头侧和尾侧神经突都恢复了它们的位置生长选择性。第三，尾侧神经突对底物选择特别敏感。当在首选底物（臀肌）上生长时，尾侧神经突更喜欢新生肌膜而非成年肌膜。这些结果支持了头侧和尾侧脊髓神经突生长偏好存在根本差异的概念。这些差异将有助于识别决定神经肌肉位置图谱形成的分子引导线索。
