Bidirectional modulation of P2X receptor-mediated response by divalent cations in rat dorsal motor nucleus of the vagus neurons

The modulatory effects of Zn2+ and other divalent cations on the ATP-induce d responses of preganglionic neurons acutely dissociated from the rat dorsa l motor nucleus of the vagus (DMV) were examined using a mystatin-perforate d patch technique under voltage-clamp. DMV neurons were identified by back- filling of Dil placed on the vagal bundle at the neck. Zn2+ exerts a concen tration-dependent effect on P2X receptor-mediated current (I-ATP): a potent iation by low concentrations of Zn2+ (less than or equal to 50 muM) and an inhibition by high concentrations (> 50 muM). Inhibition of the ATP respons e was associated with a prolongation of the rising phase of I-ATP. Cu2+ mim icked Zn2+ regarding the biphasic modulation of I-ATP. On the other hand, N i2+ potentiated, but failed to inhibit, the ATP response even at a concentr ation of 3 mm. Quantitative RT-PCR revealed the similarity of P2X(2) mRNA e xpression between the DMV and superior cervical ganglion (SCG) but not in t he dorsal root ganglion (DRG) and hypoglossal nucleus (XII). The results fr om the electrophysiological and molecular approaches suggest that functiona l P2X receptors expressed in DMV neurons are characterized mainly by the P2 X(2) and P2X(2/6) subtype. DMV neurons possess similar P2X receptor charact eristics to SCG neurons.