Filled bars represent mean values before injection of the EP4 antagonist. Open bars represent mean values after injection of the antagonist. Cross (†) represents a significant difference (P < 0.05) between the FP baseline value before and after the antagonist. Asterisk (*) represents a significant difference (P < 0.05) between the pressor response to contraction before the EP4 antagonist and the pressor response to contraction afterwards. Double cross (‡) signifies that the EP4 antagonist significantly decreased the pressor response to contraction in the Lig rats but had no effect on the pressor response to contraction in the FP rats (P < 0.001). Number sign (#) represents a significant difference between FP & Lig before injection of EP4 antagonist. EP, endoperoxide; FP, freely perfused; HR, heart rate; Lig, ligated; MAP, mean arterial pressure; TTI, tension-time index.