title: Identified motoneurons and their innervation of axial muscles in the zebrafish.
abstract: The organization of spinal cord motoneurons and their innervation of axial (white) muscles in the zebrafish were studied. Motoneurons can be divided into 2 classes, primary and secondary, on the basis of their cell-body sizes and positions. Each side of each spinal segment contains 3 primary motoneurons that are uniquely identifiable as individuals by their stereotyped cell-body positions and peripheral branching patterns. Moreover, these motoneurons precisely innervate cell-specific subsets of contiguous muscle fibers in mutually exclusive regions of their own body segment. Individual muscle fibers receive inputs from a single primary motoneuron and, in addition, from up to 3 secondary motoneurons. The results demonstrate that the precision of innervation previously described in invertebrates is also present in some vertebrates.
mesh_terms: D000818:Animals; D005071:Evoked Potentials; D005399:Fishes; D006735:Horseradish Peroxidase; D009046:Motor Neurons / Q000033:anatomy & histology*; D009132:Muscles / Q000294:innervation*
chemical_list: D006735:Horseradish Peroxidase