Bradykinin-Induced Excitation of Afferent Cardiac Sympathetic Nerve Fiber

The effect of bradykinin on afferent cardiac sympathetic nerve fibers has been examined. Using anesthetized dogs, the action potentials of the fibers were derived from either the 2nd or 3rd thoracic communicating ramus of the left side. Excitation of the afferent fibers was observed following administration of bradykinin acetate dissolved in physiological saline on the left ventricular wall. The minimum concentration required for excitation was 50-100ng/ml. The fibers were excited rhythmically synchro-nous with myocardial contraction and/or relaxation. However, no significant augmentation of myocardial contraction was produced by the agent. Bradykinin-induced excitation of the fibers was significantly reduced by pretreatment with acetylsalicylic acid. The results suggest bradykinininduced sensitization of the receptor sites of the afferent fibers for normal modality of left ventricular motion.