Exocytosis in the growth cone of differentiated chromaffin cells induced by electrical stimulation

In order to elucidate the mechanism involved in the specialized function of the nerve terminals, we studied the growth cone of cultured chromaffin cells using a video-enhanced Nomarski microscope. At a very high magnification, we found rapid and discrete morphological changes of small granules induced by electrical stimulation. Since they shared properties similar to those of the exocytotic responses found in granules in the cell body region, we conclude that they also reflect exocytosis of transmitter-containing granules. The frequency of the exocytotic responses was highest in the growth cone, lower in the cell body region, and none in the thin shaft of the neurite, suggesting a functional differentiation in the growth cone. Similar differentiation may be instrumental in physiological functions of the neuronal growth cone in vivo.