Reduction in Aortic Smooth Muscle Beta-Adrenergic Responsiveness Results in Enhanced Norepinephrine Responsiveness in the Dahl Salt-Sensitive Rat

In an earlier report we observed alterations in aortic smooth muscle α- and β-adrenergic responsiveness in the Dahl rat. The present study was designed to define the time course of these changes and further characterize the alterations in this model of hypertension. Four-week-old male Dahl salt-sensitive (DS) rats were placed on either a normal (DSN) or high salt diet (8% NaCl; DSH). Aortic smooth muscle responsiveness was studied at 3 and 6 weeks of the dietary treatment. No differences were seen between the 2 groups in either the contractile response to KCl or the relaxation responses to sodium nitrite and acetylcholine. Isoproterenol-induced relaxation was significantly attenuated and contractile response to norepinephrine (NE) were enhanced at 3 weeks of treatment in DSH rats, however, no differences were seen between the 2 groups at 6 weeks. Since alterations were seen only at 3 weeks of treatment, aortic smooth muscle responsiveness to the specific α-agonists phenylephrine (α1), guanfacine (α2) and ...