Involvement of P2 purinoceptors and the nitric oxide pathway in [3H]purine outflow evoked by short-term hypoxia and hypoglycemia in rat hippocampal slices

The objective of this study was to study how the outflow of [H-3]purines is altered during a brief period of ischemic-like conditions in superfused hippocampal slices and to show whether it is regulated by P-2 purinoceptors and the nitric oxide (NO) pathway. The outflow of [H-3]purines increased in response to 5 min of combined hypoxia/hypoglycemia. High performance liquid chromatography analysis verified the efflux of [H-3]adenosine-triphosphate, [H-3]adenosine-diphosphate, [H-3]adenosine-monophosphate, [H-3]adenosine, [H-3]inosine, and [H-3]hypoxanthine in response to ischemic-like conditions. The P-2 receptor antagonists suramin and pyridoxal-phosphate-6-azophenyl-2'-4'-disulphonic-acid-tetrasodium (PPADS) reduced significantly the [H-3]purine efflux evoked by ischemic-like conditions, showing that P-2 purinoceptors are involved in the initiation of purine outflow. The NO synthase inhibitor N-nitro-L-arginine-methyl-ester (L-NAME) attenuated significantly the [H-3]purine outflow, evoked by ischemic-like conditions, while 7-nitroindazole (7-NI) caused only a mild decrease in the outflow. The NO donor sodium nitroprusside increased significantly the basal efflux of [H-3]purines. In summary, a brief period of combined hypoxia/hypoglycemia induced the efflux of ATP in addition to the outflow of other purines. Since P-2 receptor antagonists decreased the [H-3]purine outflow evoked by ischemic-like conditions we propose that ATP, acting on P-2 purinoceptors, is responsible for further efflux of purines after ischemic-like period. It seems likely that NO is also involved in the regulation of purine outflow, since inhibition of NO production attenuated the [H-3]purine outflow, evoked by ischemic-like conditions, while exogenous NO facilitated the basal outflow. (C) 1999 Elsevier Science B.V. All rights reserved.