Background Autoantibody against the second extracellular loop of α1-adrenoceptor (α1-AA) is found in hypertensive patients showing an agonist-like activity as phenylephrine.However, long-term stimulation of α1-adrenoceptor by α1-AA did not modify the mean arterial pressure in spite of occurrence of cardiac and vascular remodeling.Methods Wistar rats were immunized with the synthetic peptides of the second extracellular loop of α1-adrenoceptor to establish an animal model which underwent long-tern stimulation by α1-AA.The agematched male Wistar rats received a mixture of saline and adjuvant was used as a sham group.All the rats were raised for 8 months.