کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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6019063 | 1186532 | 2012 | 12 صفحه PDF | دانلود رایگان |

In the central nervous system (CNS) ATP and adenosine act as transmitters and neuromodulators on their own receptors but it is still unknown which part of extracellular adenosine derives per se from cells and which part is formed from the hydrolysis of released ATP. In this study extracellular concentrations of adenosine and ATP from the rat striatum were estimated by the microdialysis technique under in vivo physiological conditions and after focal ischemia induced by medial cerebral artery occlusion. Under physiological conditions, adenosine and ATP concentrations were in the range of 130Â nmol/L and 40Â nmol/L, respectively. In the presence of the novel ecto-ATPase inhibitor, PV4 (100Â nmol/L), the extracellular concentration of ATP increased 12-fold to ~Â 360Â nmol/L but the adenosine concentration was not altered. This demonstrates that, under physiological conditions, adenosine is not a product of extracellular ATP. In the first 4Â h after ischemia, adenosine increased to ~Â 690Â nmol/L and ATP to ~Â 50Â nmol/L. In the presence of PV4 the extracellular concentration of ATP was in the range of 450Â nmol/L and a significant decrease in extracellular adenosine (to ~Â 270Â nmol/L) was measured. The contribution of extracellular ATP to extracellular adenosine was maximal in the first 20Â min after ischemia onset.Furthermore we demonstrated, by immunoelectron microscopy, the presence of the concentrative nucleoside transporter CNT2 on plasma and vesicle membranes isolated from the rat striatum. These results are in favor that adenosine is transported in vesicles and is released in an excitation-secretion manner under in vivo physiological conditions. Early after ischemia, extracellular ATP is hydrolyzed by ecto-nucleotidases which significantly contribute to the increase in extracellular adenosine. To establish the contribution of extracellular ATP to adenosine might constitute the basis for devising a correct putative purinergic strategy aimed at protection from ischemic damage.
⺠Adenosine is released per se from cells under physiological conditions. ⺠Adenosine derives mainly from extracellular ATP hydrolysis during ischemia. ⺠Presence of concentrative adenosine transporters on synaptic vesicle membranes.
Journal: Experimental Neurology - Volume 233, Issue 1, January 2012, Pages 193-204