title: Galvanic vestibular stimulation counteracts hypergravity-induced plastic alteration of vestibulo-cardiovascular reflex in rats.
abstract: Recent data from our laboratory demonstrated that, when rats are raised in a hypergravity environment, the sensitivity of the vestibulo-cardiovascular reflex decreases. In a hypergravity environment, static input to the vestibular system is increased; however, because of decreased daily activity, phasic input to the vestibular system may decrease. This decrease may induce use-dependent plasticity of the vestibulo-cardiovascular reflex. Accordingly, we hypothesized that galvanic vestibular stimulation (GVS) may compensate the decrease in phasic input to the vestibular system, thereby preserving the vestibulo-cardiovascular reflex. To examine this hypothesis, we measured horizontal and vertical movements of rats under 1-G or 3-G environments as an index of the phasic input to the vestibular system. We then raised rats in a 3-G environment with or without GVS for 6 days and measured the pressor response to linear acceleration to examine the sensitivity of the vestibulo-cardiovascular reflex. The horizontal and vertical movement of 3-G rats was significantly less than that of 1-G rats. The pressor response to forward acceleration was also significantly lower in 3-G rats (23 +/- 1 mmHg in 1-G rats vs. 12 +/- 1 mmHg in 3-G rats). The pressor response was preserved in 3-G rats with GVS (20 +/- 1 mmHg). GVS stimulated Fos expression in the medial vestibular nucleus. These results suggest that GVS stimulated vestibular primary neurons and prevent hypergravity-induced decrease in sensitivity of the vestibulo-cardiovascular reflex.
authors.affiliation: Department of Physiology, Gifu Univ. Graduate School of Medicine, 1-1 Yanagido, Gifu 501-1194, Japan.
authors.forename: Chikara
authors.initials: C
authors.lastname: Abe
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Tanaka
authors.forename: Chihiro
authors.initials: C
authors.lastname: Awazu
authors.forename: Hironobu
authors.initials: H
authors.lastname: Morita
mesh_terms: D000054:Acceleration; D000818:Animals; D001794:Blood Pressure; D002319:Cardiovascular System / Q000294:innervation*; D004558:Electric Stimulation; D006339:Heart Rate; D018471:Hypergravity; D008297:Male; D009473:Neuronal Plasticity; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012018:Reflex; D013997:Time Factors; D014725:Vestibular Nerve / Q000502:physiology*; D014726:Vestibular Nuclei / Q000378:metabolism; D014722:Vestibule, Labyrinth / Q000294:innervation*; D018474:Weightlessness Simulation
chemical_list: D016760:Proto-Oncogene Proteins c-fos