Efffect of TMP on the responses mediated by P2X receptors in rat dorsal root ganglion neurons / 中国药理学通报

ABSTRACT

Aim To explore the modulaory effect of tetramethylpyrazine(TMP) on the responses mediated by P2X receptors.Methods Whole-cell patch-clamp technique was used to study the effects of TMP on P2X receptor agonists-activated currents in freshly isolated rat dorsal root ganglion(DRG) neurons.Results Extracellular application of ATP of 1 to 1000 ?mol?L~(-1) activated currents in DRG neurons(n=102).The ATP-activated currents showed rapid desensitization or slow desensitization.Preapplication of TMP(0.1～10 mmol?L~(-1))markedly inhibited ATP(100 ?mol?L~(1))-activated currents in the majority of the neurons examined(89.2%,91/102).TMP(1 mmol?L~(-1)) reduced ?,?-meATP(10 ?mol?L~(-1))-activated currents.TMP(1 mmol? L~(-1)) shifted the concentration-response curve of I_(ATP) downward markedly.TMP(1 mmol?L~(-1)) did not alter the reversal potential(0 mV) of ATP-activated currents.TMP(1 mmol?L~(-1)) significantly inhibited ATP(100 ?mol?L~(-1))-activated currents potentiated by PGE_2(100 ?mol?L~(-1))or SP(0.1 ?mol?L~(-1)).Intracellular application of 10 ?mol?L~(-1) H89(which is an inhibitor of PKA) reduced the inhibitory effect of TMP on ATP(100 ?mol?L~(-1))-activated currents.Conclusion The mechanism of TMP action may be the allosteric regulation via acting on PKA system and the large extracellular region of ATP receptor-ion channel complex(P2X receptors) to affect P2X receptor agonists-activated currents in rat DRG neurons.