Pharmacological evidence of α-adrenergic receptors in the hypotensive effect of Chamaemulum nobile L.

This study aims to evaluate the underlying mechanism of action involved in the hypotensive effect of Chamaemulum nobile L. (Cn) aqueous extract and in anesthetized Wistar rats. Lyophilized aqueous extract was administered in the jugular vein, arterial blood pressure and heart rate were measured in the carotide artery over 120 min of injection throughout an invasive direct blood pressure measuring procedure. Intravenous bolus injection of aqueous Cn extract at the doses of 50, 100 and 200 mg/kg produced a dose dependent reduction in arterial blood pressure and heart rate (p<0.001). Specific receptor antagonists (Phentolamine, Terazosin and Atropine) and pharmacological agents (N(omega)-Nitro-L-Arginine Methyl Ester and Captopril) were used for determining the underlying mechanism involved in the hypotensive effect of Cn. Only Phentolamine treatment (2 mg/kg) reduced significantly the hypotensive effect of aqueous Cn extract at a dose of 200 mg/kg. Intravenous perfusion of aqueous Cn extract caused a significant reduction of arterial blood pressure (p<0.01) and reduced the hypertensive effect of intravenous injection of norepinephrine at a dose of 1 µg/kg. We conclude that aqueous Cn extract exhibits a hypotensive effect which may be probably due to an alpha adrenergic receptor blockade mechanism.