title: Effects of the abused solvent toluene on recombinant P2X receptors expressed in HEK293 cells.
abstract: ATP acts as a neurotransmitter in both the peripheral and central nervous systems by activating receptors in the P2Y and P2X families. P2Y receptors are coupled to intracellular signaling pathways, while P2X receptors contain an integral membrane-spanning pore and act as ion channels. Previous studies have established that certain abused drugs such as alcohol inhibit P2X receptors. In this study, we have examined the sensitivity of both homomeric and heteromeric P2X receptors to toluene, a commercial solvent widely used as a drug of abuse. P2X receptors were transiently expressed in HEK293 cells, and agonist-gated currents were measured using whole-cell patch clamp electrophysiology. Toluene potentiated currents in cells expressing homomeric P2X2 or P2X4 subunits when ATP concentrations were near or below the EC50 concentration. This potentiation was rapid in onset, voltage independent and was readily reversed upon washout of the toluene-containing solution. The toluene-induced potentiation of P2X2 currents was not altered by lowering the pH of the recording media to 5.5 or by including the heavy-metal chelator EDTA in the recording solution. At maximal ATP concentrations, toluene did not affect ATP-gated currents in cells expressing P2X2 or P2X4 receptors. ATP-gated currents were also markedly potentiated by toluene in cells transfected with both P2X4 and P2X6 subunits. In contrast, P2X3 receptor currents were inhibited by toluene at both low and high ATP concentrations. HEK293 cells transfected with both P2X2 and P2X3 subunits showed non-desensitizing currents when stimulated with alpha, beta-methylene ATP. In these cells, toluene potentiated currents only at sub-maximal concentrations of alpha, beta-methylene ATP. The results of this study suggest that the abused solvent toluene affects the function of P2X receptors in a subunit-dependent and agonist-dependent fashion.
authors.affiliation: Department of Psychiatry and Neuroscience, Center for Drug and Alcohol Programs, Medical University of South Carolina, Charleston 29425, USA. woodward@musc.edu
authors.forename: John J
authors.initials: JJ
authors.lastname: Woodward
authors.forename: Mark
authors.initials: M
authors.lastname: Nowak
authors.forename: Daryl L
authors.initials: DL
authors.lastname: Davies
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D006801:Humans; D013287:Illicit Drugs / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012997:Solvents / Q000494:pharmacology*; D014050:Toluene / Q000494:pharmacology*
chemical_list: D013287:Illicit Drugs; D020033:Protein Isoforms; D021122:Protein Subunits; D018048:Receptors, Purinergic P2; D011993:Recombinant Fusion Proteins; D012997:Solvents; D014050:Toluene; D000255:Adenosine Triphosphate