Exogenous dopamine application induced the collapse of the nontarget cell growth cone. A, Exogenous dopamine (10−5m) was applied via a pressure pipette placed in close proximity to the nontarget growth cone. B, Immediately after application, the growth cone collapsed and retracted over a short distance. C, After removal of dopamine, the morphology of the growth cone recovered fully. Scale bar, 30 μm. Frames are 15 min apart.