Cohen M J, Hall G F
Neurochem Pathol. 1986 Dec;5(3):331-43. doi: 10.1007/BF02842942.
We have examined the ability of Mueller reticulospinal neurons in the CNS of the larval sea lamprey to sprout following axonal and dendritic injury. Axotomy induces regenerative sprouting exclusively from the axon stump if it occurs at a site distant from the soma in the spinal cord. However, axotomy within the hindbrain at a site close to the soma results in profuse neuritic sprouting from the dendrites. The gross morphology and trajectories of these "dendritic" sprouts resemble those of regenerating axons. Amputation of Mueller cell dendrites (dendrotomy) without axotomy does not result in neuritic sprouting from either the axon or dendrites, indicating that axotomy is specifically required for sprouting to occur. However, dendrotomy is capable of altering the distribution of sprouting in a previously axotomized Mueller cell by inducing sprouting at the site of the dendrotomy lesion. Sprouts of both dendritic and axonal origin tend to follow linear, rostrocaudally oriented paths along or near the ventral surface of the hindbrain. Some sprouts form very large, palmate growth cones on the marginal surface, which in turn give rise to many branches that continue to grow either rostrally or caudally along the surface of the brain. We discuss the possibility that both dendritic and axonal sprouts evoked by axotomy of Mueller neurons are recapitulating initial axonal development during embryogenesis, and that their trajectories are determined by developmental guidance cues persisting in the ventral hindbrain.
我们研究了海七鳃鳗幼体中枢神经系统中米勒网状脊髓神经元在轴突和树突损伤后发芽的能力。如果轴突切断发生在脊髓中远离胞体的部位，那么轴突切断仅会诱导轴突残端发生再生性发芽。然而，在后脑内靠近胞体的部位进行轴突切断，则会导致树突大量长出神经突。这些“树突状”新芽的总体形态和轨迹与再生轴突相似。在未进行轴突切断的情况下切断米勒细胞树突（树突切断术），并不会导致轴突或树突长出神经突，这表明发芽的发生特别需要轴突切断。然而，树突切断术能够通过在树突切断损伤部位诱导发芽，来改变先前已进行轴突切断的米勒细胞中发芽的分布。树突和轴突来源的新芽都倾向于沿着后脑腹面或其附近，呈线性、头尾方向排列的路径生长。一些新芽在边缘表面形成非常大的掌状生长锥，这些生长锥又会产生许多分支，这些分支会沿着脑表面继续向前或向后生长。我们讨论了米勒神经元轴突切断引发的树突和轴突新芽可能重现胚胎发育过程中初始轴突发育的可能性，以及它们的轨迹是由后脑海腹侧持续存在的发育引导线索所决定的。
