Local vestibular blood flow and systemic vascular responses to natural vestibular stimulation in the Mongolian gerbil

Hypothesis: Natural stimulation of the vestibular end organs will produce a lterations in the local vestibular microvascular blood now. Background: The vestibular and cardiovascular systems require a coordinated interaction to maintain organ perfusion during rapid positional and postur al changes. However, the detailed relationship of these systems is not well understood. There have been no previous descriptions of local vestibular b lood flow (VBF) during natural stimulation (NS) conditions. Methods: In vivo VBF and systemic blood pressure (BP) in the Mongolian gerb il during natural stimulation. Using laser Doppler flowmetry, the authors o btained continuous measures of local VBF in both anesthetized and alert ger bils during sinusoidal rotational stimuli. Simultaneous recordings of syste mic BP were collected from the contralateral common carotid artery. Results: The anesthetized gerbils showed stable VBF and BP during all vesti bular stimuli. By contrast, alert subjects demonstrated a significant respo nse to natural stimulation. The VBF increased 28% over baseline, and system ic BP increased 8% during a 45-second, 0.133-Hz sinusoid. Decreases in BP o f 8% and 5%, respectively, were seen with a 0.10 and 0.20 Hz, 360-second st imulus. A corresponding determination of VBF during the extended stimulus c onditions was not technically possible. Conclusions: To the authors' knowledge these are the first in vivo descript ions of vestibular blood flow during natural stimulation. In the alert anim als, VBF increased in response to NS. This increase in flow does not appear to be directly dependent on systemic blood pressure changes and indicates that the vestibular microvasculature is closely regulated.