Target influences on the morphology of trigeminal axons

摘要: Axons grow in two stages: First, they exhibit rapid, target-directed extension; then begin to collateralize and elaborate terminal arbors their targets. To investigate possible regulatory influences on these phases of axon growth, we have used an vitro paradigm which cocultured embryonic or postnatal rat trigeminal ganglion explants with isochronic, heterochronic, and/or heterotypic Cultures were fixed after 5 days cell processes labeled DiI. Trigeminal able regenerate into several peripheral targets as well CNS from nontrigeminal regions the brain. In tissues, showed target-specific growth patterns. tissue, type (unbranched extension versus collateralization/arbor formation) varied markedly explant age: If ganglia harvested at a time (E15) when axons would be elongating embryo isochronic had simple morphology, loosely bundled, reconstituted distinct fiber tract, mimicking vivo pattern. If, challenged by more mature E15 cells formed discrete arbors. Finally, if age (E20, PND 5) already brain induced innervate younger targets, reverted back elongation stage. These results demonstrate that target environment sets specific, developmentally regulated constraints patterns manifested primary sensory axons.