Axonal elongation and directional growth are affected by both stimulatory and inhibitory factors. Previous work has shown that axonal contact with inhibitory factors results in collapse of the growth cone. To further study mechanisms involved in the action of inhibitory factors, an in vitro bioassay consisting of gradients of inhibitory activity contained in agarose gel will be established and characterized. This bioassay will be used with chick dorsal root ganglion neurons to determine whether inhibitory factors that cause growth cone collapse also have effects on directional growth of axons. In addition, the effects of growth cone collapse on specific components of the cytoskeleton labeled with antibodies will be studied using time- lapse video microscopy and transmission electron microscopy. These studies are fundamental to identifying molecules involved in axonal guidance.
