P2X and P2Y Receptors Mediate Contraction Induced by Electrical Field Stimulation in Feline Esophageal Smooth Muscle

Abstract

It is well-known that electrical field stimulation (EFS)-induced contraction is mediated by a cholinergic mechanism and other neurotransmitters NO, ATP, calcitonin gene-related peptide (CGRP), and substance P are released by EFS To investigate the purinergic mechanism involved in the EFS-induced contraction, purinegic receptors antagonists were used Suramine, a non-selective P2 receptor antagonist, reduced the contraction induced by EFS NF023 (10(-7) similar to 10(-4) M), a selective P2X antagonist, inhibited the contraction evoked by EFS Reactive blue (10(-6) similar to 10(-4) M), selective P2Y antagonist, also blocked the contraction in a dose-dependent manner In addition, P2X agonist alpha,beta-methylene 5`-adenosine triphosphate (alpha beta MeATP, 10(-7) similar to 10(-5) M) potentiated EFS-induced contraction in a dose-dependent manner P2Y agonist adenosine 5`[beta -thio]diphosphate trilithium salt (ADP beta S, 10(-7) similar to 10(-5) M) also potentiated EFS-induced contractions in a dose-dependent manner Ecto-ATPase activator apyrase (5 and 10 U/ml) reduced EFS-induced contractions Inversely, 6-N,N-diethyl-D-beta,gamma- dibromomethylene 5`-triphosphate triammonium (ARL 67156, 10(-4) M) increased EFS-induced contraction These data suggest that endogenous ATP plays a role in EFS-induced contractions which are mediated through both P2X-receptors and P2Y-receptors stimulation in cat esophageal smooth muscle