Ethanol differentially affects ATP-gated P2X(3) and P2X(4) receptor subtypes expressed in Xenopus oocytes.
P2X receptors are cation-selective, ligand-gated ion channels activated by synaptically released, extracellular adenosine 5'-triphosphate (ATP). ATP-gated currents are inhibited by ethanol when tested in dorsal root ganglion and CA1 neurons. Recently, we reported differences in sensitivity to ethanol inhibition between homomeric P2X(2) and P2X(4) receptors expressed in Xenopus oocytes, which suggested that subunit composition of native P2X receptors determines their ethanol sensitivity. The present study extended the investigation to P2X(3) receptors. The effects of ethanol and zinc ions (Zn(2+)) were tested on homomeric P2X(3) and P2X(4) receptors expressed in Xenopus oocytes using two-electrode voltage clamp. Ethanol potentiated ATP-gated P2X(3) receptor currents in a concentration dependent manner. In contrast, ethanol inhibited P2X(4) receptor function. Ethanol did not directly alter receptor function, nor did it alter the Hill coefficient or maximal ATP response (E(max)) in either P2X(3) or P2X(4) receptors. Ethanol increased the maximal response to Zn(2+) ATP-gated currents in P2X3 receptors which suggests that ethanol and Zn(2+) act on different sites. The differences in ethanol response of P2X(3) and P2X(4) receptors set the stage for future investigations that will use chimeric P2X receptors or other molecular manipulations of P2X structure to investigate the molecular sites and mechanisms of action of ethanol.
Department of Molecular Pharmacology/Toxicology, School of Pharmacy, University of Southern California, 1985 Zonal Avenue, Los Angeles, CA 90033, USA. ddavies@usc.edu
Daryl L
DL
Davies
Andrei A
AA
Kochegarov
Sacha T
ST
Kuo
Ashutosh A
AA
Kulkarni
John J
JJ
Woodward
Brian F
BF
King
Ronald L
RL
Alkana
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology*; D000818:Animals; D002492:Central Nervous System Depressants / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004558:Electric Stimulation / Q000379:methods; D000431:Ethanol / Q000494:pharmacology*; D015640:Ion Channel Gating / Q000187:drug effects*; D008564:Membrane Potentials / Q000187:drug effects / Q000528:radiation effects; D008845:Microinjections / Q000379:methods; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D018408:Patch-Clamp Techniques / Q000379:methods; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058477:Receptors, Purinergic P2X3; D058848:Receptors, Purinergic P2X4; D011994:Recombinant Proteins / Q000378:metabolism; D015533:Transcriptional Activation / Q000502:physiology; D014981:Xenopus; D015032:Zinc / Q000494:pharmacology
D002492:Central Nervous System Depressants; D018048:Receptors, Purinergic P2; D058477:Receptors, Purinergic P2X3; D058848:Receptors, Purinergic P2X4; D011994:Recombinant Proteins; D000431:Ethanol; D000255:Adenosine Triphosphate; D015032:Zinc; C002630:alpha,beta-methyleneadenosine 5'-triphosphate