Axonal interaction enhences fasciculation

**Figure 1:** H, Axons are assembled in bundles underneath the epithelium[1], I, Glomeruli receives axons in form of smaller fascicles[1]. J, Interacting axons in our model fasciculates in time.
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Neurons must make, from an immense array of options, specific choices of where to project their axons and where to form synapses with other neurons. Historically, wiring of sensory neurons to the brain has been studied rigorously because of their easy accessibility and well characterised, orderly projections. More than 1500 kind of sensory neurons (SN) are known to exist in mammalian olfactory systems as receptors to different odors. Olfactory neurons expressing the same odorant receptor converge with great precision to a small number of glomerule in the olfactory bulb. This suggests that spatial patterns are used to encode olfactory information.

How do the axons emerging from the olfactory epithelium find their path ? Chemical signalling is an viable means of communication: where certain certain guiding axons could sence the chemical gradient generated by the target and move accordingly and others just follow the guiding neuron. This mechanism, to work in olfactory systems, need huge number of chemoattractants to differentiate between different targets. Also in recent experiments in mouse olfactory systems suggest that, axons could make their path with few/no guiding neurons. We ( Martin Zapotoky, Peter Borowski and I ) are looking an alternate mechanism for the formation of glomeruli.

Olfactory SNs die in regular basis and are replaced by the newer ones. We propose that the new born axons interact with the shafts of the older ones during pathfinding. This model, analytical tractable in certain regime, shows that fasciculation is in fact possible without guiding neurons also suggests a time scale for the formation of olfactory network in embryonic days.

Pradeep Kumar Mohanty 2005-05-12