不同初级感觉神经元ATP-激活电流的特征及意义

为探讨大鼠不同初级感觉神经元ATP-激活电流的电生理学特征及意义,本实验在新鲜分离的大鼠三种初级感觉神经元标本上,应用全细胞膜片钳技术记录,对外加ATP引起的膜电流的变化进行了研究。结果显示:(1)受检的细胞绝大多数对ATP敏感,外加ATP记录到内向电流,在背根神经节和三叉神经节神经元记录到三种形式的ATP-激活电流:快速激活快速失活型(fasttype,F型)、快速激活缓慢失活型(intermediatetype,I型)和缓慢激活缓慢失活型(slowtype,S型),但在结状神经节神经元主要记录到S型电流,三种形式的电流均具有浓度依赖性;(2)三种形式的ATP-激活电流上升相(risingphase,R)从10%至90%的时间(R10-90)有明显差异(P<0.05),去敏感相(desensitizingphase)从10%至90%的时间(D10-90)也有明显差异(P<0.05);(3)三种形式的电流EC50非常接近,I型的量-效曲线居中间,F型的下移,S型的上移;(4)小细胞的ATP-激活电流多表现为F型特征,大细胞多表现为S型特征,而中等大小的细胞多表现为I型特征,结状神经节神经元电流形式与细胞大小没有相关性。以上结果提示:躯体和内脏初级感觉神经元ATP-激活电流的类型可能与不同的感觉性质有关;不同形式的ATP激活电流可能由ATP受体的不同亚单位组成的各种亚型中介。

THE CHARACTERISTICS AND SIGNIFICANCES OF ATP-ACTIVATED CURRENTS IN DIFFERENT PRIMARY SENSORY NEURONS

To explore the characteristics and significances of ATP-activated currents in rat different primary sensory neurons, the experiments were performed on neurons freshly isolated from rat dorsal root ganglion(DRG), trigeminal ganglion (TG) and nodose ganglion (NG) using whole-cell patch-clamp. The results showed that: (1) The majority of examined neurons responded to ATP applied externally with inward currents. We recorded three types of ATP-activated currents in DRG and TG: fast type, slow type and intermediate type,while there was mainly slow type of ATP-activated currents in NG. All the three types of currents were concentration-dependent. (2) The rising phase time from 10% to 90% varied greatly among the three types of ATP-activated currents (P<0.05) and the same thing occurred when it came to the desensitizing phase from 10% to 90%(P<0.05). (3) The EC 50 of the three dose-response curves of ATP-activated current tended to be identical. The curve for fast ATP-activated current shifted downwards as compared with the intermediate ATP-activated current, and that for the slow ATP-activated current shifted upwards. (4) In general, the fast ATP-activated currents were distributed mainly in small-diameter DRG and TG neurons; the slow ATP-activated currents were distributed mainly in large-diameter DRG and TG neurons; and the intermediate ATP-activated currents were distributed mainly in intermediate-diameter DRG and TG neurons; while the types of ATP-activated current recorded in NG neurons were not related to the diameter of a cell. The results suggest that three types of ATP-activated currents from different primary sensory neurons may be related to the properties of various senses; these types of ATP-activated current might be mediated by various subtypes of ATP receptors.