Abstract
The relationship between ATP-induced membrane potential and contraction was inestigated in the smooth muscle of chicken anterior mesenteric artery using micro-electrode and tension recording techniques respectively. Application of ATP to en-dothelium-denuded arterial preparations developed concentration-dependent, slow depolarization which started only at concentrations not less than 10 μM. On the other hand the tension recording experiment revealed that ATP produced concentration dependent contractions, which were evident at concentrations lower than those evoked depolarizing response to ATP (as lower 100 nM). Both depolarizing & contracting responses were abolished by the P2X receptor blocker, PPADS (50 μM) but not by P2Y receptor blocker CBF3GA (100 μM), indicating that the excitatory responses of ATP were mediated via activation of P2X receptor. These findings suggest that ATP-mediated contraction is not dependent on membrane depolarization only, at least at low concentrations in the first order branches of chicken anterior mesenteric artery. arabic 21 English 153