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

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Abstract
The modulatory effects of Zn2+ and other divalent cations on the ATP‐induced responses of preganglionic neurons acutely dissociated from the rat dorsal motor nucleus of the vagus (DMV) were examined using a nystatin‐perforated patch technique under voltage‐clamp. DMV neurons were identified by back‐filling of DiI placed on the vagal bundle at the neck. Zn2+ exerts a concentration‐dependent effect on P2X receptor‐mediated current (IATP): a potentiation by low concentrations of Zn2+ (≤ 50 µm) and an inhibition by high concentrations (> 50 µm). Inhibition of the ATP response was associated with a prolongation of the rising phase of IATP. Cu2+ mimicked Zn2+ regarding the biphasic modulation of IATP. On the other hand, Ni2+ potentiated, but failed to inhibit, the ATP response even at a concentration of 3 mm. Quantitative RT‐PCR revealed the similarity of P2X2 mRNA expression between the DMV and superior cervical ganglion (SCG) but not in the dorsal root ganglion (DRG) and hypoglossal nucleus (XII). The results from the electrophysiological and molecular approaches suggest that functional P2X receptors expressed in DMV neurons are characterized mainly by the P2X2 and P2X2/6 subtype. DMV neurons possess similar P2X receptor characteristics to SCG neurons.