Abstract
The membrane potential of cultured mouse astrocytes was recorded to assess the effects of extracellular adenosine 5′‐triphospate (ATP) and related ^H^purines on astrocyte electrophysiology. The purines were applied with or without the presence of barium, which blocks the high resting K^+^ conductance in astrocytes. The response to ATP alone was a moderate depolarization; however, the response to ATP in the presence of barium was a large, dose dependent depolarization. The ED~50~ was approximately 10 μM. The effect of adenosine 5′‐diphosphate (ADP) or adenosine 5′‐monophosphate (AMP), in the presence of barium, on membrane potential was less than that of ATP. Adenosine, with or without barium, had no effect on membrane potential; furthermore, adenosine agonists in barium produced no response. The results of applying various ATP analogues indicate that the response is mediated via a P~2~‐purinoceptor. Ion replacement studies reveal a complicated response to ATP that has serveral components and involves Na^+^ and K^+^. These results show that astrocytes respond with ionic changes to very small, physiological concentrations of extracellular ATP. We suggest that ATP plays a role in interactions between neurons/endothelial cells and glial cells. © 1992 Wiley‐Liss, Inc.