The aim of this program is to understand the principles, and mechanisms that govern cellular communication between astrocytes and between astrocytes and neurons. Although neurons are the central players in cellular communication and information processing in the brain, in recent years it has become clear that the glial cells play an important role in signalling. Neurone-glial interactions have been suggested for a long time, however, recent discoveries of glial cell types, excitability and signalling properties have raised the awareness. During embryonic development the importance of specific humoral signals from glial cells are important for neuronal survival and development. Methods have become available for obtaining relatively pure cultures of different types of astrocytes, as well as mixed neuronal and glial cultures. Methods are also available for light microscopic analysis of cells in slice preparations. Fluorescence microscopy with digital image processing will be used as the technique to monitor intracellular signalling in astrocytes and neurons in order to describe specific communication between cells. The intracellular calcium changes in response to activation of various neurotransmitter receptor systems on astrocytes isolated from different regions of brain will be investigated. These results will be correlated with companion studies on astrocytes in situ, by measurement of cellular responses in the brain slice preparation.