Saccular and utricular influences on sympathetic nerve activities in cats

We studied the effects of stimulation of the utricular and saccular nerves on sympathetic nerve activity in decerebrated cats. Bipolar electrodes were fixed in place on the utricular and/or saccular nerve under visual observation; the other branches of the vestibular nerve were transected. Baroreceptors and vagus nerves were inactivated bilaterally so that inputs from baroreceptors and other visceral receptors did not influence the sympathetic nerve outflow. Postganglionic sympathetic nerve activity was recorded from the renal branch of the sympathetic nerve, which is known to be more sensitive to vestibular stimuli than other types of sympathetic fibers. With stimulation of either the saccular or utricular nerve at low stimulus intensity, a prominent inhibition followed by a rebound excitation was evoked on spontaneous renal nerve discharges. The latency of the inhibition ranged from 65 to 130 ms, and the duration of inhibitory responses was about 90-150 ms. An increase in stimulus intensity in both the saccular and utricular nerves induced inhibitory effects preceded by short-term excitation. The latency of this excitation, which was superimposed on the initial phase of the inhibitory responses, ranged from 55 to 90 ms.