Adenosine receptor mediated stimulation of intracellular calcium in acutely isolated astrocytes.
The characteristics of adenosine receptors found in glial fibrillary acid protein (GFAP)-positive astrocytes acutely isolated from the cerebral cortices of 4- to 12-day old rats were examined by evaluating the effects of adenosine and its analogues on intracellular calcium levels. First, these effects were compared with those seen in primary astrocytic cultures, and it was found that acutely isolated astrocytes showed much greater sensitivity to adenosine than their cultured counterparts. Then, the adenosine evoked calcium responses in acutely isolated cells were evaluated under various conditions. The responses to adenosine were not inhibited by papaverine, an uptake blocker, or by removal of extracellular calcium. U73122, a phospholipase C inhibitor, was able to completely inhibit the adenosine response. The receptor inhibitor 3-isobutyl-1-methylxanthine inhibited the calcium response to adenosine, providing evidence that the response is not coupled to the xanthine-insensitive A3 receptor. The stimulatory action of NECA, a non-selective analogue, was blocked neither by the A2A-selective receptor antagonist 8-(3-chlorostyryl) caffeine nor by the A1-selective receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine. The A2B receptor antagonist alloxazine, however, was able to completely inhibit the increase in intracellular calcium produced by NECA. Taken together, these data suggest that the adenosine-evoked calcium response in acutely isolated astrocytes is coupled to the A2B receptor.
Division of Neurosurgery, A-60, Department of Pharmacology and Neuroscience, Albany Medical College, 47 New Scotland Avenue, Albany, NY 12208, USA.
J G
JG
Pilitsis
H K
HK
Kimelberg
D000241:Adenosine / Q000494:pharmacology; D019830:Adenosine-5'-(N-ethylcarboxamide) / Q000494:pharmacology; D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002469:Cell Separation; D002478:Cells, Cultured; D004963:Estrenes / Q000494:pharmacology; D005415:Flavins / Q000494:pharmacology; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism*; D011760:Pyrrolidinones / Q000494:pharmacology; D051381:Rats; D018047:Receptors, Purinergic P1 / Q000502:physiology*; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors
D004963:Estrenes; D005415:Flavins; D011760:Pyrrolidinones; D018047:Receptors, Purinergic P1; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D019830:Adenosine-5'-(N-ethylcarboxamide); C008173:isoalloxazine; D010738:Type C Phospholipases; D000241:Adenosine; D002118:Calcium