Ethanol is a Fast Channel Inhibitor of P2X4 Receptors

P2X receptors (P2XRs) are ion channels gated by synaptically released ATP. The P2X4 is the most abundant P2XR subtype expressed in the central nervous system and to date is the most ethanol-sensitive. In addition, genomic findings suggest that P2X4Rs may play a role in alcohol intake/preference. However, little is known regarding how ethanol causes the inhibition of ATP-gated currents in P2X4Rs. We begin to address this issue by investigating the effects of ethanol in wild-type and mutant D331A and M336A P2X4Rs expressed in human embryonic kidney (HEK) 293 cells using whole-cell patch-clamp methods. The results suggest that residues D331 and M336 play a role in P2X4R gating and ethanol inhibits channel functioning via a mechanism different from that in other P2XRs. Key findings from the study include: 1) ethanol inhibits ATP-gated currents in a rapid manner; 2) ethanol inhibition of ATP-gated currents does not depend on voltage and ATP concentration; 3) residues 331 and 336 slow P2X4 current deactivation and regulate the inhibitory effects of ethanol; and 4) ethanol effects are similar in HEK293 cells transfected with P2X4Rs and cultured rat hippocampal neurons transduced with P2X4Rs using a recombinant lentiviral system. Overall, these findings provide key information regarding the mechanism of ethanol action on ATP-gated currents in P2X4Rs and provide new insights into the biophysical properties of P2X4Rs.