PC12 is a clonal line of rat pheochromocytoma cells that upon exposure to nerve growth factor extend neurites and acquire the morphology of neurons (7, 25). Both undifferentiated and nerve growth factor treated cells store and secrete dopamine and acetylcholine (9, 14, 16, 20, 23). This property makes PC12 useful for. pharmacological studies in that one can compare the effects of a particular drug on two different transmitter systems in the same cell.