title: Linear acceleration-evoked cardiovascular responses in awake rats.
abstract: It has been well documented that vestibular-mediated cardiovascular regulation plays an important role in maintaining stable blood pressure (BP) during postural changes. But the underlying neural mechanisms remain to be elucidated. In particular, because the vestibular stimulation employed in previous animal studies activated both semicircular canals and otolith organs, the contributions of the otolith system has not been studied selectively. The goal of the present study was to characterize cardiovascular responses to natural otolith stimulation in awake rats that were subjected to pure linear motion. In any of the four directions tested, transient linear motion produced a short-latency ( approximately 520 ms) increase in mean BP with a peak of 8.27 +/- 0.66 mmHg and was followed by a decrease in BP. There was an initial small biphasic response in heart rate (HR) that was followed by a longer duration increase. The short-latency increase in BP was absent in rats that were pentobarbital sodium anesthetized or that were labyrinthectomized bilaterally, but it was unaffected by baroreceptor denervation, indicating that it was of otolith origin. The increase in BP was linear acceleration intensity dependent and was not affected by absence of visual cues. Furthermore, the BP response was attenuated by inactivation of the medial and inferior vestibular nuclei by microinjections of muscimol, indicating that the otolith-driven cardiovascular responses are mediated by the neurons in these areas. These results not only demonstrate the otolith specific influences on the cardiovascular system but also they establish the first rodent model for examining the neural mechanisms underlying the otolith-mediated cardiovascular regulation.
authors.affiliation: Dept. of Otolaryngology and Communicative Sciences, University of Mississippi Medical Center, Jackson, MS 39216, USA. hozhu@ent.umsmed.edu
authors.forename: Hong
authors.initials: H
authors.lastname: Zhu
authors.forename: James R
authors.initials: JR
authors.lastname: Jordan
authors.forename: Steven P G
authors.initials: SP
authors.lastname: Hardy
authors.forename: Beverly
authors.initials: B
authors.lastname: Fulcher
authors.forename: Curtis
authors.initials: C
authors.lastname: Childress
authors.forename: Cheryl
authors.initials: C
authors.lastname: Varner
authors.forename: Byron
authors.initials: B
authors.lastname: Windham
authors.forename: Ben
authors.initials: B
authors.lastname: Jeffcoat
authors.forename: Robin W
authors.initials: RW
authors.lastname: Rockhold
authors.forename: Wu
authors.initials: W
authors.lastname: Zhou
mesh_terms: D000054:Acceleration; D000818:Animals; D001794:Blood Pressure / Q000502:physiology*; D002320:Cardiovascular Physiological Phenomena; D003243:Consciousness / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology*; D008297:Male; D023421:Models, Animal; D008954:Models, Biological; D009475:Neurons, Afferent / Q000502:physiology; D010037:Otolithic Membrane / Q000502:physiology*; D011311:Pressoreceptors / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000502:physiology; D014726:Vestibular Nuclei / Q000502:physiology