title: TNP-ATP, a potent P2X3 receptor antagonist, blocks acetic acid-induced abdominal constriction in mice: comparison with reference analgesics.
abstract: Exogenous ATP has been shown to be algogenic in both animal and humans. Research has focused on the P2X3 ligand-gated ion channel, as it is preferentially expressed on nociceptive C-fibers. In addition, P2X3 receptor gene disrupted mice show decreased responses to somatic painful stimuli. However, the potential role of P2X receptor activation in visceral pain has not yet been evaluated. In the present study, the systemic administration of suramin, and pyridoxal-phosphate-6-azophenyl-2',4'-disulfonic acid, PPADS, both non-selective P2X receptor antagonists, dose-dependently reduced acetic acid-induced abdominal constrictions in mice (ED(50)=34.5 micromol/kg and ED50=70 micromol/kg, respectively). Furthermore, 2'-(or-3')-O-(trinitrophenyl)adenosine 5'- tri-phosphate (TNP-ATP) potently (IC50=10 nM) blocked the functional activation of P2X3 receptors in vitro and attenuated acetic acid-induced visceral pain. In the abdominal constriction assay, TNP-ATP (ED(50)=6.35 micromol/kg, i.p.) was 6-10 fold more potent than suramin and PPADS to reduce nociceptive behavior. In addition, TNP-ATP was 10 fold more potent than TNP-AMP (2'-(or-3')-O-(trinitrophenyl)adenosine 5'-mono-phosphate) (ED50=63.5 micromol/kg, i.p.) at reducing acetic acid-induced nociception. At the highest dose, TNP-ATP completely abolished nociceptive behavior, as did morphine (ED50=3 micromol/kg, i.p.). While TNP-ATP is also a potent antagonist of P2X1 receptors, P2X1 receptor mediated responses have not been shown in dorsal root ganglia and diinosine pentaphosphate, IP5I, a potent and selective P2X1 receptor antagonist, was ineffective at reducing abdominal constrictions. Thus, the antinociceptive effects of TNP-ATP appear to be mediated through activation of homomeric P2X3and/or heteromeric P2X2/3 receptors. Together, these results show that activation of P2X3 containing receptors plays a role in the transmission of inflammatory visceral pain.
authors.affiliation: Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, IL 60064, USA. marie.honore@ln.ssw.abbott.com
authors.forename: Prisca
authors.initials: P
authors.lastname: Honore
authors.forename: Joseph
authors.initials: J
authors.lastname: Mikusa
authors.forename: Bruce
authors.initials: B
authors.lastname: Bianchi
authors.forename: Heath
authors.initials: H
authors.lastname: McDonald
authors.forename: Jayne
authors.initials: J
authors.lastname: Cartmell
authors.forename: Connie
authors.initials: C
authors.lastname: Faltynek
authors.forename: Michael F
authors.initials: MF
authors.lastname: Jarvis
mesh_terms: D000005:Abdomen; D019342:Acetic Acid / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D001522:Behavior, Animal / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology; D010146:Pain / Q000139:chemically induced / Q000188:drug therapy*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D058919:Purinergic P2 Receptor Antagonists; D011732:Pyridoxal Phosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D058477:Receptors, Purinergic P2X3; D013498:Suramin / Q000494:pharmacology
chemical_list: D000700:Analgesics; D000970:Antineoplastic Agents; C546407:P2RX3 protein, human; C546409:P2rx3 protein, mouse; D010975:Platelet Aggregation Inhibitors; D058919:Purinergic P2 Receptor Antagonists; D058477:Receptors, Purinergic P2X3; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; D011732:Pyridoxal Phosphate; D013498:Suramin; C045674:2',3'-O-(2,4,6-trinitro-cyclohexadienylidine)adenosine 5'-triphosphate; D000255:Adenosine Triphosphate; D019342:Acetic Acid; D002118:Calcium