We have reported that the myogenic response of the renal afferent arteriole (Af-art) and middle cerebral artery (MCA), and autoregulation of renal and cerebral blood flow are impaired in Fawn Hood Hypertensive (FHH) rats. Transfer of a region of chromosome 1 containing gamma-adducin (Add3) from Brown Norway rats rescues the vascular dysfunction and the development of renal disease. To examine whether Add3 is a viable candidate gene altering renal and cerebral hemodynamics in FHH rats, we knocked down the expression of Add3 in rat Af-art and MCA cultured for 36-hours using a 27-mer Dicer-substrate short interfering RNA (DsiRNA). Control Af-arts constricted by 10 ± 1% in response to an elevation in pressure from 60 to 120 mm Hg but dilated by 4 ± 3% when treated with Add3 DsiRNA. Add3 DsiRNA had no effect on the vasoconstrictor response of the Af-art to NE (10-7 M). Add3 DsiRNA had a similar effect to attenuate the myogenic response in MCA. Peak potassium currents were 3-fold higher in smooth muscle cells isolated from Af-arts or MCAs transfected with Add3 DsiRNA than in non-transfected cells isolated from the same vessels. This is the first study demonstrating that Add3 plays a role in the regulation of potassium channel function and vascular reactivity. It supports the hypothesis that sequence variants in Add3, we previously identified in FHH rats, may play a causal role in the impaired myogenic response and autoregulation in renal and cerebral circulation.