Morphological and electrophysiological aspects of dissociated cultures of rat CNS

Rat central nervous system has been cultured up to 6 weeks after complete dissociation. Maturation of different cell types has been followed in the quasi monolayer by phase contrast microscopy. Dorsal root ganglion (DRG) neurones usually differed from central nervous system (CNS) neurones by their spherical shape accompanied by only one or two processes, exact identification of cell types, however, was usually only possible by combining morphology with electrophysiology. Scanning electron-microscopy revealed a more extensive arborization of neurites and a higher number of presumed synaptic structures in cultures after 2 weeks of culturing. Layers of ependymal cells were also found. The different cell types were further identified by determining their membrane properties. Glial cells had higher resting membrane potentials (-56 +/- 9.7 mV) than CNS neurones (-49 +/- 10.2 mV), while the membrane potential of DRG neurones lay in-between the two (-53 +/- 1.7 mV). The sequence for input resistance was: DRG neurones (30 +/- 9.3 M omega) greater than CNS neurones (18 +/- 10.5 M omega) greater than glial cells (9.3 +/- 5.2 M omega). In CNS neurones the input resistance is correlated with the membrane potential, which is not the case for glial cells. Action potentials of DRG neurones exhibited delayed repolarisation increasing the spike duration to three times that of CNS neurones.