The Bezold-Jarisch in the conscious dog.

Publisher Website
Google Scholar
Abstract
The Bezold-Jarisch reflex was studied in 22 conscious, instrumented dogs. Specific left ventricular receptor stimulation was elicited by the circumflex coronary artery injection of veratridine in doses ranging from 0.01-0.40 .mu.g/kg. None of these doses resulted in hemodynamic effects when given i.v. Heart rate, arterial blood pressure, left ventricular pressure, left ventricular dp/dt [change in pressure with time] and cardiac output were monitored and total peripheral resistance calculated. Dose-related decreases in arterial blood pressure and heart rate were observed following intracoronary injection of veratridine. Decreases were noted in dp/dt max, left ventricular pressure and cardiac output. With the heart paced to prevent bradycardia, the decrease in all these parameters was significantly attenuated; a significant decrease in total peripheral resistance was still observed (-30.2 .+-. 3.7%). Cardiac pacing plus the administration of the .alpha.-adrenergic-blocking agent, phentolamie, blocked the decrease in total peripheral resistance when compared to pacing alone. The administration of atropine significantly attenuated the bradycardia, hypotension, decrease in dp/dt max and decrease in total peripheral resistance in response to intracoronary veratridine. Atropine plus phentolamine abolished the decrease in total peripheral resistance that was evoked by intracoronary veratridine. The decrease in dp/dt max which resulted from veratridine administration was induced largely by the associated bradycardia, since both cardiac pacing and atropine significantly attenuated it. The chemical stimulation of left ventricular receptors in the conscious dog mediates a bradycardia, hypotension and decrease in total peripheral resistance which is produced by sympathetic withdrawal as well as cholinergic vasodilation. There is not significant inotropic effect elicited by the stimulation of these receptors.