Evidence of normal mitosis with complete cytokinesis in central nervous system neurons during sustained depolarization with ouabain

Ouabain-induced depolarization of culture-matured spinal cord neurons from chick embryos causes the activation of DNA synthesis with subsequent mitotic nuclear division in a large fraction of the cells. Many of the activated neurons do not complete cytokinesis, and the binucleate cells thus formed have served as a convenient index for assaying the effectiveness of mitogenesis induction. However, the fact that the frequency of neurons induced to initiate DNA synthesis is consistently much larger than the frequency of binucleate neurons ultimately observed suggested the possibility that the difference may represent activated neurons that do complete cytokinesis, but go undetected in the binucleate assay cultures. This possibility was explored in the present study by determining the respective frequencies of induced neurons entering mitotic metaphase and completing mitotic telophase, and comparing them with the frequency of binucleate neurons ultimately formed. The results provide further evidence that normal mitogenic and mitotic processes are induced in central nervous system neurons by the depolarization treatment, and indicate that between 40 and 60% of the neurons which complete telophase subsequently undergo complete cytokinesis.