Effect of intermedin/adrenomedullin-2 on venous tone in conscious rats

We investigated the effect of intermedin/adrenomedullin-2 (3 and 10 nmol/kg, i.v.), a member of the calcitonin gene-related peptide family, relative to the vehicle (0.9% NaCl) on mean circulatory filling pressure (index of venous tone) in conscious rats: intact (unblocked) or ganglionic blocked through treatment with mecamylamine (10 mg/kg, i.v.) and noradrenaline (4 mu g/kg/min, i.v.). In intact rats, both doses of intermedin/adrenomedullin-2 reduced mean arterial pressure (-14 +/- 3, -30 +/- 3 mmHg), but did not alter mean circulatory filling pressure; the high dose also increased heart rate. In ganglionic-blocked rats, both doses decreased mean arterial pressure (-22 +/- 3, -46 +/- 5 mmHg) and the high dose also decreased mean circulatory filling pressure (-2.81 +/- 0.82 mmHg), but neither dose affected heart rate. The vehicle did not have any effects in any of the groups. In addition, intermedin/adrenomedullin-2 did not have any effect on blood volume in both intact and ganglion-blocked rats. The results show that intermedin/adrenomedullin-2 is a dilator of arterial resistance and capacitance vessels.