PRESSOR-RESPONSE ELICITED BY NOSE-UP VESTIBULAR STIMULATION IN CATS

The purpose of the present study was to determine whether selective ac tivation of vestibular receptors produces changes in blood pressure. B lood pressure was recorded during trapezoidal head rotations in cats w ith extensive denervations to eliminate nonlabyrinthine inputs that co uld be produced by the movements. Large (50 degrees) nose-up trapezoid al head tilts produced an increase in blood pressure of approximately 18 mmHg; ear-down tilt produced little change in blood pressure. The c hanges in blood pressure began approximately 1.4 s after the plateau o f the stimulus. The responses to nose-up tilt were abolished following intracranial transections of the VIIIth cranial nerves. These data su ggest that vestibular inputs elicited by nose-up movements of the head act to rapidly increase blood pressure. This mechanism may contribute to counteracting the orthostatic hypotension induced by nose-up body rotation in quadrupeds.