Abstract
A possible relation between the elongation of the neurite (morphological differentiation) and the electrical maturation of the membrane (functional differentiation) in neuroblastoma clonal NS-20 cells was studied using serum-free medium, and the medium containing dibutyryl cyclic AMP, or aminopterin. The cells displayed round or spindle in shape (undifferentiated cells) in the normal growth medium. However, in the three kinds of experimental media, the neurites elongated rapidly in the early developmental stage, and their lengths increased gradually to a steady level in the late developmental stage. The range of responses to electrical stimulation varied from the passive response and the delayed rectification to the active response. The rapid elongation of the neurites was accompanied with increasing of resting membrane potential and membrane resistance in the early stage, but the cells producing the active response appeared in the late stage. Finally, most of the differentiated cells came to generate the active response. These results suggest that (1) morphological maturation of NS-20 cells was succeeded by electrical maturation of the cell membrane, and acquisition of the membrane excitability was not always coincident with the morphological differentiation, and (2) the developmental sequence of the membrane excitability was in the following order: the passive response, the delayed rectification and the active response.
