A–C, Representative IKs traces from control females are shown at baseline and in presence of 500nM ISO ± 100nM ICI-118,551 (β2-adrenergic receptor blocker). D–E, Summarized step and tail current-voltage (I-V) relationship for IKs in control females. F–H, Representative IKs traces from control males are shown at baseline and in presence of 500nM ISO ± 100nM ICI-118,551. I–J, Summarized step and tail current-voltage (I-V) relationship for IKs are shown at baseline and in presence of 500nM ISO ± 100nM ICI-118,551 for control males (n=7 (7 hearts)).