Familial studies of heritability of α1-adrenergic receptor responsiveness in superficial veins*

44 healthy nonsmoking subjects, comprising adults (n=24; age range 40-52 years) and their biological children (n=20; age range 15-26 years), free from medications likely to modify vascular tone.

Norepinephrine administration to assess superficial vein responsiveness (ED50) via linear variable differential transformer technique.

Heritability of the dose of norepinephrine required to constrict superficial vein diameter by 50% from baseline (ED50).surrogate