Sperlágh B, Zsilla G, Baranyi M, Illes P, Vizi E S
Department of Pharmacology, Institute of Experimental Medicine, Hungarian Academy of Sciences, H-1450 Budapest, Szigony u. 43., Hungary.
Neuroscience. 2007 Oct 12;149(1):99-111. doi: 10.1016/j.neuroscience.2007.07.035. Epub 2007 Aug 1.
The aim of the present study was to explore whether endogenous activation of different purine receptors by ATP and adenosine contributes to or inhibits excess glutamate release evoked by ischemic-like conditions in rat hippocampal slices. Combined oxygen-glucose deprivation (OGD) elicited a substantial, Ca(2+)-independent release of [(3)H]glutamate, which was tetrodotoxin (1 microM)-sensitive and temperature-dependent. The P2 receptor antagonist pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS, 0.1-10 microM), and the selective P2X(7) receptor antagonist Brilliant Blue G (1-100 nM), decreased OGD-evoked [(3)H]glutamate efflux indicating that endogenous ATP facilitates ischemia-evoked glutamate release. The selective A(1)-receptor antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX, 0.1-250 nM) and the selective A(2A) receptor antagonists 4-(2-[7-amino-2-)2-furyl(triazolo-[1,3,5]triazin-5-ylamino]ethyl)phenol (ZM241385, 0.1-20 nM) and 7-(2-phenylethyl)-5-amino-2-(2-furyl)-pyrazolo-[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine (SCH58261, 2-100 nM) decreased OGD-evoked [(3)H]glutamate efflux, indicating that endogenous adenosine also facilitates glutamate release under these conditions. The effect of DPCPX and ZM241385 was reversed, whereas the action of P2 receptor antagonists was potentiated by the selective ecto-ATPase inhibitor 6-N,N-diethyl-D-beta,gamma-dibromomethyleneATP (ARL67156, 50 microM). The binding characteristic of the A(2A) ligand [(3)H]CGS21680 to hippocampal membranes did not change significantly in response to OGD. Taken together these data suggest that while A(1) receptors might became desensitized, A(2A) and P2X receptor-mediated facilitation of glutamate release by endogenous ATP and its breakdown product adenosine remains operational under long-term OGD. Therefore the inhibition of P2X/A(2A) receptors rather than the stimulation of A(1) adenosine receptors could be an effective approach to attenuate glutamatergic excitotoxicity and thereby counteract ischemia-induced neurodegeneration.
本研究的目的是探讨ATP和腺苷对不同嘌呤受体的内源性激活是否会促进或抑制大鼠海马切片中类似缺血条件诱发的过量谷氨酸释放。联合氧糖剥夺（OGD）引发了大量的、不依赖细胞外钙离子浓度（Ca(2+)）的[3H]谷氨酸释放，这种释放对河豚毒素（1微摩尔）敏感且依赖温度。P2受体拮抗剂磷酸吡哆醛-6-偶氮苯基-2',4'-二磺酸（PPADS，0.1 - 10微摩尔）和选择性P2X(7)受体拮抗剂亮蓝G（1 - 100纳摩尔）可减少OGD诱发的[3H]谷氨酸外流，表明内源性ATP促进了缺血诱发的谷氨酸释放。选择性A(1)受体拮抗剂1,3 - 二丙基-8 - 环戊基黄嘌呤（DPCPX，0.1 - 250纳摩尔）、选择性A(2A)受体拮抗剂4 - (2 - [7 - 氨基 - 2 - (2 - 呋喃基)(三唑并[1,3,5]三嗪 - 5 - 基氨基]乙基)苯酚（ZM241385，0.1 - 20纳摩尔）和7 - (2 - 苯乙基)-5 - 氨基 - 2 - (2 - 呋喃基)-吡唑并[4,3 - e]-1,2,4 - 三唑并[1,5 - c]嘧啶（SCH58261，2 - 100纳摩尔）均可减少OGD诱发的[3H]谷氨酸外流，表明在这些条件下内源性腺苷也促进谷氨酸释放。DPCPX和ZM241385的作用被逆转，而P2受体拮抗剂的作用则被选择性胞外ATP酶抑制剂6 - N,N - 二乙基 - D - β,γ - 二溴亚甲基ATP（ARL67156，50微摩尔）增强。A(2A)配体[3H]CGS21680与海马膜的结合特性在OGD刺激下没有显著变化。综上所述，这些数据表明，虽然A(1)受体可能会脱敏，但在长期OGD条件下，A(2A)和P2X受体介导的内源性ATP及其分解产物腺苷对谷氨酸释放的促进作用仍然存在。因此，抑制P2X/A(2A)受体而非刺激A(1)腺苷受体可能是减轻谷氨酸能兴奋性毒性从而对抗缺血性神经变性的有效方法。
