The present work is to study neural differentiation in melanocytes in relation to the cell cycle and UV exposure. Whole skin organ cultures of vitiliginous skin were exposed to a pulse of UV with and without prior Adriamycin treatment. It was observed that the highly dendritic marginal melanocytes are destroyed on UV exposure during the depigmentation phase but not during repigmentation. The melanocytes are resistant to UV destruction during the G2 phase as seen on Adriamycin treatment. They show a prominent increase in dendricity as well as biphasic activity to produce increased melanin and noradrenaline. Thus, the melanocytes form a UV-sensitive neural network in the skin. These responses are reminiscent of the repigmentation and depigmentation of coat color in animals exposed to extreme variations in the day/night cycles as seen at the poles.