Urocortin (Ucn) has been shown to produce vasodilatation in several arteries but the precise mechanism of its action is still poorly understood. Here we studied the role of store operated Ca²⁺ (SOC) entry and Ca²⁺-independent phospholipase A₂ (iPLA₂) in agonist-induced vasoconstriction of rat coronary artery and their possible modulation by Ucn. Ca²⁺ measurement and vessel contraction were studied in SMC and rat coronary arteries as described previously (1,2). We show that Ucn vasodilate phenylephrine hydrochloride (PE)-induced rat coronary artery contractions independently of the L-type Ca²⁺ channel pathway. Moreover, we demonstrate that SOC entry regulated by iPLA₂ is involved in the vasoconstriction. We found that SOC channels inhibition by 2-aminoethoxydiphenyl borate (2APB), diethylstilbestrol (DES) and iPLA₂ inhibition by bromoenol lactone (BEL) produces relaxation of PE, but not high K⁺, -induced contraction. In addition, we found that Ucn inhibits SOC influx evoked by the emptying of the stores with thapsigargin in rat coronary smooth muscle cells. Ucn inhibits Ca²⁺ influx induced by thapsigargin in primary cultured and freshly dispersed SMC. Furthermore, Ucn inhibits iPLA₂ activity and decreases the expression of iPLA₂ mRNA and proteins. The present study provides evidences to demonstrate a new mechanism of relaxation induced by Ucn that involves iPLA₂ and SOC entry modulation in rat coronary artery.