Specificity of early motoneuron growth cone outgrowth in the chick embryo.

摘要: During development, chick lumbosacral motoneurons have been reported to form precise topographic projections within the limb from time of initial outgrowth. This observation implies, first, that select appropriate muscle nerve pathway and, second, they restrict their ramification primary uncleaved masses regions. Several reports based on electrophysiology and orthograde horseradish peroxidase (HRP) labeling shown selection be fairly precise. However, studies retrograde with HRP produced conflicting extent which vertebrate make projection errors. Since it is difficult distinguish between true errors leakage when using labeling, we decided assess distribution labeled growth cones in 25-micron serial plastic sections, following identifiable subpopulations during period axon Examination a large number nerves revealed no segmentally inappropriate axons, confirming earlier very accurate. In addition, observed take widely divergent trajectories into same nerve, suggesting are responding independently some specific environmental cue rather than being passively channeled at this point. The provided direct evidence did not any project obviously regions.(ABSTRACT TRUNCATED AT 250 WORDS)