NPA抑制大鼠DRG分离神经元ATP-激活电流

Inhibition by NPA of ATP-activated current in rat DRG neurons

目的 本研究主要探讨多巴胺D2受体的选择性激动剂R(- ) -NPA对ATP -激活电流的调制。方法 在大鼠新鲜分离的DRG神经元标本上应用全细胞膜片钳技术 ,观察了NPA对ATP -激活电流的作用。结果 大部分受检细胞 (87.3% ,48/ 5 5 )对ATP敏感 ,10 -6～ 10 -3 mol/LATP可引起剂量依赖性呈明显去敏感的内向电流。在此45个细胞中 ,预加NPA可引起三类反应 :(1)外向电流 (6 .3% ,3/ 48) ;(2 )内向电流 (2 5 .0 % ,12 / 48)和 (3)无反应 (6 8.8% ,33/ 48)。与ATP -激活电流相比 ,NPA -激活电流幅值小 ,无明显去敏感现象。预加NPA 30～ 6 0s对ATP -激活电流的影响如下 :在 91.7% (4 4/ 48)的细胞产生抑制作用 ,其余的无明显作用 (8.3% ,4/ 48)。此种抑制作用与NPA本身是否引起或引起的是内向或外向电流无关。在浓度 10 -7～ 10 -5mol/L范围NPA对 10 -4 mol/LATP -激活电流的抑制作用依赖于NPA的浓度。胞内透析GDP - β -s上述抑制作用可完全被取消。 结论 NPA对ATP -激活电流的抑制作用可能是由于D2受体激活后经G蛋白偶联及相应胞内转导途径而使ATP受体磷酸化所致。

Objective The purpose of the present study was to explore whether NPA modulates the response mediated by ATP(P2X) receptors.Methods Experiments were performed on neurons freshly isolated from rat DRG using whole-cell patch clamp techniques.Results The majority of the neurons examined were responsive to ATP (87.3%,48/55) in the concentration range from 10 -6 to 10 -3 mol/L with an inward current showing obvious desensitization. In the 48 ATP-sensitive cells, responses induced by selective agonist of dopamine D2 receptor NPA manifested three patterns:(1)outward current(6.3%,3/48); (2)inward current(25.0%,12/48) and no detectable response(68.8%,33/48). Compared with ATP-activated current, the NPA-activated current was of smaller amplitude and showed inapparent desensitization. When the neurons were treated with NPA prior to application of ATP for 30～60 seconds, the ATP-activated current in the majority of the cells (91.7%,44/48) were inhibited, while the remaining cells(8.3%,4/48)was not affected .The effect of NPA was dose dependent. By intracellular dialysis of GDP-β-s the inhibitory effect of NPA could be completely abolished.Conclusions Suggesting this inhibitory action might be an outcome of the phosphorylation of ATP receptor resulting from intracellular signal transduction.