An in vivo investigation of the negative chronotropic effect of cholic acid in the rat.

1. Experimental obstructive jaundice in the Wistar rat causes a significant decrease in heart rate. 2. Intravenous administration of cholic acid in vivo elicits a dose-dependent negative chronotropic effect. 3. Atropine or vagotomy significantly reduces, but does not abolish, the negative chronotropic effect of cholic acid. 4. Ganglion blockade and decerebration diminishes the negative chronotropic effect of cholic acid, but to a lesser extent than atropine or vagotomy. 5. Sympathetic depletion by reserpine slightly potentiates the response to cholic acid. 6. The effect of cholic acid injected cranially into the common carotid artery is less than when administered into the jugular vein. 7. The haemolysis caused by cholic acid does not appear to be involved in the negative chronotropic effect. 8. It is concluded that cholic acid causes both a direct as well as a vagally mediated negative chronotropic effect in the Wistar rat.