Morphological and electrophysiological changes in cultured spinal ganglion cells during development

Morphological changes of partially dissociated chick spinal ganglion cells in culture and their intracellular responses were simultaneously observed in an attempt to investigate the correlation between cell structure and function during development in vitro. As the ganglion cells natured, their originally eccentric nuclei assumed more central positions and the surface area of cell body displayed a linear increase accompanied with an increase in cell diameter. Nissl bodies were distributed throughout the cytoplasm after 3 to 4 weeks and myelin was formed at the same period. The bioelectric properties of the ganglion cells changed in parallel with the morphological development. The passive membrane properties such as resting potentials and specific membrane resistance were increased. Action potentials could be elicited from neurons as early as 2 days in vitro, while the complete excitability was accomplished at 8 to 10 days. Moreover, the wave form of the action potenial itself was changed, that is, the amplitude and maximum rate of rise increased and the duration decreased. The alteration rates of these passive and active properties were maximum at 8 to 12 days in culture. Repetitive firing occurred after 3 to 4 weeks, though single responses were displayed by 3 weeks in culture. This changes seemed to correspond with myelin formation in vitro.