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Concept
Pioneer axon
Résumé
Pioneer axon is the classification given to axons that are the first to grow in a particular region. They originate from pioneer neurons, and have the main function of laying down the initial growing path that subsequent growing axons, dubbed follower axons, from other neurons will eventually follow.
Several theories relating to the structure and function of pioneer axons are currently being explored. The first theory is that pioneer axons are specialized structures, and that they play a crucial role in guiding follower axons. The second is that pioneer axons are no different from follower axons, and that they play no role in guiding follower axons.
Anatomically, there are no differences between pioneer and follower axons, although there are morphological differences. The mechanisms of pioneer axons and their role in axon guidance is currently being explored. In addition, many studies are being conducted in model organisms, such grasshoppers, zebrafish, and fruit flies to study the effects of manipulations of pioneer axons on neuronal development.
Santiago Ramon y Cajal, considered the father of modern neuroscience, was one of the first to physically observe growing axons. Moreover, he observed that axons grew in a structured, guided manner. He advocated that axons were guided by chemotactic cues. Indeed, later experiments showed that in both invertebrate and vertebrate models, axons grew along pre-determined routes to create a reproducible scaffold of nerves.
Ramon y Cajal's views faced some competition from those of Paul Alfred Weiss, his contemporary neuroscientist during the 1920s and 1930s. Weiss argued that functional specificity did not depend on specific axon connections, and that nonspecific mechanical cues participated in guiding axons. Subsequent investigations into chemotactics cues that started in the 1970s eventually proved that Ramon y Cajal's initial ideas were intuitive and ahead of his time.
The mechanism of growth of pioneer neurons has been investigated in the central and peripheral nervous systems of invertebrate animals.
Source officielle
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