Reduced cardiovascular sympathetic excitatory responses during iloprost infusion in conscious dogs.
OBJECTIVE
The aim was to determine the effects of the stable prostacyclin analogue iloprost (ZK 36374) on systemic haemodynamics and on cardiovascular neural control.


METHODS
The buffering effect was examined of intravenous and intracoronary iloprost infusion on the excitatory sympathetic reflexes elicited from the heart by (1) intracoronary injections of bradykinin and (2) transient coronary artery occlusion.


METHODS
22 conscious mongrel dogs of either sex, weight 20-25 kg, were used.


RESULTS
ECG, systemic arterial pressure, left atrial pressure, and left ventricular pressure, and contractility (dP/dt) were continuously monitored for the duration of the experiments. Iloprost infusion reduced left ventricular pressure, mean arterial pressure, and dP/dt without causing significant changes in heart rate. Transient non-hypertensive coronary artery occlusion increased heart rate and depressed contractility. During intravenous iloprost infusion, coronary artery occlusion no longer elicited an increase in heart rate, while left ventricular dP/dt was more drastically reduced. This pattern of response was not substantially modified by beta adrenergic blockade, whereas the blockade of muscarinic receptors with atropine was accompanied by hypotension and a greater reduction of dP/dt. The observation of a reduced pressor response to the intracoronary injections of bradykinin during iloprost administration further indicated a restraining effect of iloprost on the sympathetic reflexes elicited from the heart.


CONCLUSIONS
The data suggest the hypothesis that the protective effects on the ischaemic myocardium observed with iloprost infusions may arise not only from its vasodilator and antiplatelet properties, but also from its capacity to blunt excitatory sympathetic reflexes.
Rimoldi
O
O
CNR, Centro per le Ricerche Cardiovascolari, Milan, Italy.
Pierini
S
S
Pagani
M R
MR
Pagani
M
M
D000818:Animals; D001157:Arterial Occlusive Diseases / Q000503:physiopathology; D001794:Blood Pressure / Q000187:drug effects; D001920:Bradykinin / Q000037:antagonists & inhibitors; D003327:Coronary Disease / Q000503:physiopathology; D004285:Dogs; D006321:Heart / Q000294:innervation*; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D016285:Iloprost / Q000494:pharmacology*; D013564:Sympathetic Nervous System / Q000187:drug effects*; D014630:Vagus Nerve / Q000187:drug effects; D016277:Ventricular Function, Left / Q000187:drug effects
D016285:Iloprost; D001920:Bradykinin