Aortic nerve stimulation in the rat: cardiovascular and respiratory responses.

Cardiovascular response and changes in the phrenic and recurrent laryngeal nerve activities to the electrical stimulation of the aortic nerves were studied in the decerebrate male Wistar rats. Stimulus parameters were varied over a wide range (intensities 0.1-10 volts, frequencies 2-150 pulses per sec, durations 0.01-10 msec) and stimulation was continued for 1 min to ensure that steady state was reached. Stimulation of the aortic nerves consistently produced decreases in blood pressure and heart rate (baroceptor responses) while increase in blood pressure and heart rate (chemoreceptor responses) were never obtained. Inhibition of phrenic and recurrent laryngeal nerve activities (baroceptor responses) always followed stimulation of aortic nerves while facilitation of these nerve activities (chemoreceptor responses) was never observed. These results indicate that the aortic nerves of the rat contain mainly baroceptor afferent fibers and there are few, if any, functional chemoreceptor fibers in these nerves.