RECEPTORS ON ASTROCYTES - WHAT POSSIBLE FUNCTIONS

Receptors for transmitters, as varied as those expressed by neurons, h ave been described on primary astrocyte cultures prepared from new-bor n rats and mice. A variety of functional effects and considerable cell -to-cell and regional heterogeneity have been observed for such recept ors in vitro. The various systems available for studying the presence and properties of receptors on astrocytes in situ, and the results fro m these studies, are discussed. Much fewer studies using these more di fficult systems have been done. So far, some resemblances and differen ces between in situ and in vitro work have been observed. More of thes e in situ studies, to supplement the ongoing in vitro work, are needed to enable us to determine unequivocally which receptors are present o n astrocytes, and their functions in vivo. If there is cell-to-cell an d CNS regional heterogeneity in vivo comparable to that seen in vitro, these analyses will be very complex. To illustrate the importance and variety of receptor-linked functions, a number of suggestions are mad e in this commentary, based on current proposals for the roles of astr ocytes. However, it is argued that we need to have a more complete und erstanding of astrocyte functions in vivo, before we can really unders tand the functional significance of astrocyte receptors.