Normalization of up-regulated cardiac imidazoline I1-receptors and natriuretic peptides by chronic treatment with moxonidine in spontaneously hypertensive rats

The effect of treatment with moxonidine (120 mug/kg/h sc, 4 weeks) on cardiac I-1-receptors and natriuretic peptide synthesis was evaluated in spontaneously hypertensive rats (SHR). I-1-receptor protein (85 kD) was up-regulated in SHR atria, and normalized in right and left atria by moxonidine. Similarly, moxonidine normalized atrial and ventricular atrial natriuretic peptide messenger RNA (mRNA) and brain natriuretic peptide mRNA. This study shows that cardiac I-1-receptors are functional, being regulated by hypertension and by chronic exposure to agonist, and that cardiac natriuretic peptides may be regulated by I-1-receptor-mediated mechanisms.