Primary astrocyte cultures—a key to astrocyte function

Morphological studies have established the ubiquitous nature of astrocytes in the CNS. Their processes surround capillaries and synapses, form the subpial and subependymal layers, and seemingly invest every neuronal surface not covered by other neuronal surfaces or oligodendroglial membranes. Although such interrelationships have long suggested that astrocytes may play many critical roles, there still remains relatively little experimental information on the functions and properties of these cells. About a decade ago it became evident that primary cultures from neonatal rodent brains can consist predominantly of normal astrocytes. Based on these findings there is now an increasing number of studies in which such primary cultures are being used to help unravel the continuing enigma of the properties and functions of astrocytes. Aspects of this work are reviewed in this article. Such work has already shown that astrocytes in primary culture exhibit the basic electrophysiological characteristics which had been the only functional property well established for these cells in situ. Further studies of the electrophysiological properties of these cells, which can be correlated with ion transport studies, are beginning to show that astrocytes may have more complex electrophysiological properties than had previously been supposed, as well as a number of important electrically silent ion fluxes. In addition, astrocytes in primary culture show uptake of and receptors for a number of transmitters, properties which have wide-ranging implications. Studies in culture also support work in vivo that astroglia may have an important role in neuronal development.