Sustained ventricular unloading action of the alpha-adrenergic antagonist nicergoline in the dog

Preliminary studies indicate that nicergoline, a new alpha-antagonist, can lower HR at doses which decrease arterial BP. The present animal study was designed to quantitate the systemic and carotid (pulsed Doppler) hemodynamic and renin release consequences of nicergoline ventricular unloading, and to investigate the hemodynamic mechanisms of hypotension. In 11 anesthetized dogs, nicergoline infusion induced progressive, moderate, and prolonged hypotension associated with reduced vascular resistance and capacitance. Hypotension resulted from decreased HR and cardiac output, without an increase in plasma renin activity. The effects on carotid hemodynamics were less marked than those on the systemic circulation. Hypotension was caused primarily by vasoplegia, and was magnified subsequently by inhibition of the reflex rapid pressor control mechanisms. This suggests that repeated iv doses of nicergoline are preferable to prolonged infusion.