Dual-Tracer Assessment of Coupling Between Cardiac Sympathetic Neuronal Function and Downregulation of β-Receptors During Development of Hypertensive Heart Failure of Rats

Background—Heart failure is associated with activation of the sympathetic nervous system and downregulation of β-receptors. However, the coupling between cardiac sympathetic neuronal function and the β-receptor during the development of hypertensive heart failure is not clear. Methods and Results—We determined cardiac neuronal function and β-receptors with a dual-tracer method of [131I]metaiodobenzylguanidine (MIBG) and 125I-cyanopindolol (ICYP) in Dahl salt-sensitive (DS) and salt-resistant (DR) rats. The rats were fed an 8% NaCl diet after the age of 6 weeks. Blood pressure was raised to >200 mm Hg at 12 weeks in DS rats and remained elevated until 18 weeks, but only slightly in DR rats. Left ventricular (LV) function of DS rats was preserved at 12 weeks but deteriorated at 18 weeks. Despite a 56% reduction of cardiac norepinephrine (NE) content at 12 weeks in DS rats, neither MIBG nor ICYP uptake in DS rats was different from that of DR rats. At 18 weeks, both MIBG and ICYP uptakes decreased, by 52% an...