Morphological and physiological properties of neurons and glial cells in tissue culture.

THE METHOD of tissue culture offers a unique opportunity for investigating electrophysiological properties of single cells by means of microelectrodes under direct visual control. Crain (13) has published microelectrode record? ings of the action potentials from spinal ganglion cells of chicken embryos. Hild et al. (26) have reported electrophysiological findings on glial elements from the mammalian brain maintained in vitro. Recently, Cunning.ham and Rylander (14) investigated electric properties of brain tissue from chicken embryos (10 days incubation) which was kept in vitro for up to 120 hours; these investigators were, however, interested more in the behavior of the tissue as a whole and did not investigate at the cellular level. It seemed of great interest to extend our earlier observations since it is possible at present to maintain neurons in vitro in good condition for extended periods of time. In many instances protoplasmic processes of living neurons can easily be observed under a phase-contrast microscope. It is generally easy to distinguish dendrites from axons in such preparations. It is possible, therefore, to investigate the electrophysiological properties of various parts of a nerve cell under direct visual control. Obviously, the present method differs greatly from that in previous studies in which properties of the neuron soma and dendrites were inferred from the electric responses recorded from the gray matter with macroelectrodes or from the data of single cell recordings without any knowledge as to the position of the microelectrode relative to the cells under study. The first half of the present paper deals with the results of our observations on the neuron soma and the dendrite by this method. In the second half, we are concerned with a comparison of electrophysiological properties of neurons with those of neuroglial cells and of macrophages.