Suppression of arterial pressure, heart rate and cardiac contractility following microinjection of kainic acid into the nucleus ambiguus of the rat

In pentobarbital anesthetized rats, unilateral microinjection (500 ng) of the selective perikaryal excitotoxin, kainic acid, into the nucleus ambiguus promoted a significant suppression of arterial pressure, heart rate and cardiac contractility. The degree of such cardiovascular depression followed the order of heart contractility reduction (50.7%) greater than hypotension (28.9%) greater than bradycardia (20.8%) at the end of a 60-min postinjection period. We concluded that the nucleus ambiguus may exert its control on cardiac activities by both negative chronotropic and inotropic effects on the heart.