Collapse of growth cone structure on contact with specific neurites in culture.

We have studied the morphology of embryonic chick retinal and sympathetic growth cones as they meet retinal and sympathetic neurites grown in culture. Growth cones preserve their normal morphology and ability to locomote when retinal growth cones contact retinal neurites or when sympathetic growth cones contact sympathetic neurites. Growth cones collapse and their motility ceases when retinal growth cones contact sympathetic neurites or when sympathetic growth cones contact retinal neurites. Collapse was never observed before a growth cone touched a neurite. As a growth cone collapses, the neurite it leads retracts. After a brief pause, a new growth cone is organized and extension recommences. These results suggest that contact-mediated inhibition of locomotion could play a role in growth cone guidance.