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

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

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∼10^−4M), a selective P2X antagonist, inhibited the contraction evoked by EFS. Reactive blue (10^−6∼10^−4M), selective P2Y antagonist, also blocked the contraction in a dose-dependent manner. In addition, P2X agonist Ձ,Ղ-methylene 5 -adenosine triphosphate (ՁՂMeATP, 10^−7∼10^−5M) potentiated EFS-induced contrac</SUP>tion in a dose-dependent manner. P2Y agonist adenosine 5 -[Ղ-thio]diphosphate trilithium salt (ADPՂS, 10^−7∼10^−5M) 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-Ղ,Ճ- dibromomethylene 5 -triphosphate triammonium (ARL 67156, 10^−4M) 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.