title: The vasovagal response of the rat: its relation to the vestibulosympathetic reflex and to Mayer waves.
abstract: Vasovagal responses (VVRs) are characterized by transient drops in blood pressure (BP) and heart rate (HR) and increased amplitude of low-frequency oscillations in the Mayer wave frequency range. Typical VVRs were induced in anesthetized, male, Long-Evans rats by sinusoidal galvanic vestibular stimulation (sGVS). VVRs were also produced by single sinusoids that transiently increased BP and HR, by 70-90° nose-up tilts, and by 60° tilts of the gravitoinertial acceleration vector using translation while rotating (TWR). The average power of the BP signal in the Mayer wave range increased substantially when tilts were >70° (0.91 g), i.e., when linear accelerations in the x-z plane were ≥0.9-1.0 g. The standard deviations of the wavelet-filtered BP signals during tilt and TWR overlaid when they were normalized to 1 g. Thus, the amplitudes of the Mayer waves coded the magnitude of the linear acceleration ≥1 g acting on the head and body, and the average power in this frequency range was associated with the generation of VVRs. These data show that VVRs are a natural outcome of stimulation of the vestibulosympathetic reflex and are not a disease. The results also demonstrate the usefulness of the rat as a small animal model for studying human VVRs.
authors.affiliation: Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, Brooklyn 10029-6574, USA. bernard.cohen@mssm.edu
authors.forename: Bernard
authors.initials: B
authors.lastname: Cohen
authors.forename: Giorgio P
authors.initials: GP
authors.lastname: Martinelli
authors.forename: Theodore
authors.initials: T
authors.lastname: Raphan
authors.forename: Adam
authors.initials: A
authors.lastname: Schaffner
authors.forename: Yongqing
authors.initials: Y
authors.lastname: Xiang
authors.forename: Gay R
authors.initials: GR
authors.lastname: Holstein
authors.forename: Sergei B
authors.initials: SB
authors.lastname: Yakushin
mesh_terms: D000054:Acceleration; D000818:Animals; D001696:Biomechanical Phenomena; D001794:Blood Pressure / Q000502:physiology*; D002320:Cardiovascular Physiological Phenomena; D004558:Electric Stimulation; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D023421:Models, Animal; D017156:Photoplethysmography; D011187:Posture / Q000502:physiology; D051381:Rats; D020318:Rats, Long-Evans; D012018:Reflex / Q000502:physiology; D012399:Rotation; D013564:Sympathetic Nervous System / Q000502:physiology; D014722:Vestibule, Labyrinth / Q000502:physiology
keywords: blood pressure; faints; heart rate; linear acceleration; otolith system; sinusoidal galvanic vestibular stimulation