Cardiovascular changes produced by the injection of aconitine at the area of the locus coeruleus in unanesthetized rats.

Blood pressure, heart rate and electrocardiogram were monitored in unanesthetized, unrestrained rats while the area of the locus coeruleus was stimulated by the injection of 0.03 to 10 micrograms of aconitine to pharmacologically evaluate its cardiovascular action. Aconitine elicited a dose-dependent elevation of mean blood pressure to 200 mmHg; at doses of 1-10 micrograms, it increased heart rate by more than 100 beats/min and produced arrhythmias. Phentolamine and the serotonergic antagonist, 2-bromo-lysergic acid diethylamide, prevented aconitine-induced cardiovascular changes. Diminution of aconitine-induced tachycardia by propranolol was attributed to the antagonist's direct peripheral effects. Atropine (5 mg/kg, subcutaneously) did not alter aconitine's cardiovascular actions. It is suggested that stimulation of the area of the locus coeruleus with aconitine elicits specific cardiovascular effects, which may involve adrenergic as well as serotonergic pathways.