Sensitization by extracellular Ca (2+) of rat P2X 5 receptor and its pharmacological properties compared with rat P2X 1

摘要: The recombinant rat P2X(5) (rP2X(5)) receptor, a poorly understood ATP-gated ion channel, was studied under voltage-clamp conditions and compared with the better homomeric rP2X(1) receptor which it may coexist in vivo. Expressed defolliculated Xenopus laevis oocytes, rP2X(5) responded to ATP slowly desensitizing inward currents that, for successive responses, ran down presence of extracellular Ca(2+) (1.8 mM). Replacement either Ba(2+) or Mg(2+) prevented rundown, although agonist responses were very small, whereas reintroduction short periods time ( 2',3'-O-(2,4,6-trinitrophenyl)ATP (TNP-ATP) > suramin reactive blue 2 (RB-2) diinosine pentaphosphate (Ip(5)I). In contrast, potency order at TNP-ATP = Ip(5)I PPADS RB-2. Thus, Ca(2+)-sensitized is similar profile rP2X(1)-although can be distinguished from latter by GTP agonism, antagonist profile, modulatory effects H(+) Zn(2+) ions.