A new assay for nerve fiber repulsion.

In inflammatory lesions, sympathetic nerve fibers get lost soon after the start of inflammation. To be able to identify and examine the factors that are responsible for this repulsion of the sympathetic nerve fibers we established an in vitro assay. Sympathetic trunk ganglia of postnatal mice were used for the outgrowth of axons. They were plated on poly-D-lysine-coated culture slides. Axons were encouraged to grow out by the addition of nerve growth factor-7S (NGF) from murine submaxillary gland. Using live imaging it was clearly shown that SEMA3F is a nerve-repellent factor. Two different types of nerve fiber repulsion were observed. The assay turned out to be an excellent model for the investigation of axon guidance factors of sympathetic neurons (nerve fiber repulsion/nerve fiber attraction).