Effects of acute hypotension on neuronal activity in the medial vestibular nuclei of rats

The role of peripheral vestibular receptors in acute hypotension was investigated in anesthetized rats. In animals with intact labyrinths, acute hypotension induced by either i.v. infusion of sodium nitroprusside or hemorrhage produced excitation of electrical activity in two-thirds of type I neurons and inhibition in two-thirds of type II neurons recorded in the medial vestibular nuclei. In unilaterally labyrinthectomized animals, two-thirds of type I neurons ipsilateral to the lesion showed an inhibitory response, and two-thirds of contralateral type I neurons showed an excitatory response after the induction of acute hypotension. The response patterns of type II neurons were opposite to those of type I neurons. These results suggest that blood flow changes are detected by peripheral vestibular receptors, and that this might suggest a mechanism for control of blood pressure.