Ionic dependence of a P2-purinoceptor mediated depolarization of cultured astrocytes.
The membrane potential of cultured mouse astrocytes was recorded to assess the effects of extracellular adenosine 5'-triphosphate (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 ED50 was approximately 10 microM. 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 P2-purinoceptor. Ion replacement studies reveal a complicated response to ATP that has several 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.
Magoski
N S
NS
Department of Physiology, College of Medicine, University of Saskatchewan, Saskatoon, Canada.
Walz
W
W
D000249:Adenosine Monophosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000378:metabolism*; D001464:Barium / Q000494:pharmacology; D002478:Cells, Cultured; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008839:Microelectrodes; D009457:Neuroglia / Q000187:drug effects / Q000378:metabolism; D011687:Purines / Q000494:pharmacology; D011983:Receptors, Purinergic / Q000187:drug effects*
D011687:Purines; D011983:Receptors, Purinergic; D001464:Barium; D000249:Adenosine Monophosphate; D000255:Adenosine Triphosphate