title: Respiratory modulation of sympathetic activity is attenuated in adult rats conditioned with chronic hypobaric hypoxia.
abstract: Respiratory modulation of sympathetic nerve activity (SNA) depends on numerous factors including prior experience. In our studies, exposing naïve adult, male Sprague-Dawley rats to acute intermittent hypoxia (AIH) enhanced respiratory-modulation of splanchnic SNA (sSNA); whereas conditioning them to chronic hypobaric hypoxia (CHH) attenuated modulation. Further, AIH can evoke increased SNA in the absence phrenic long-term facilitation. We hypothesized that AIH would restore respiratory modulation of SNA in CHH rats. In anesthetized, CHH-conditioned (0.5 atm, 2 wks) rats (n=16), we recorded phrenic and sSNA before during and after AIH (8% O2 for 45s every 5min for 1h). At baseline, sSNA was not modulated with respiration. The sSNA was not recruited during a single brief exposure of hypoxia nor after 10 repetitive exposures. Further, the sSNA chemoresponse was not restored 1h after completing AIH. Thus, CHH-conditioning blocked the short-term plasticity expressed in sympatho-respiratory efferent activities and this was associated with reduced respiratory modulation of sympathetic activity and with attenuation of the sympatho-respiratory chemoresponse.
authors.affiliation: Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Case Western Reserve University, Cleveland, Ohio, United States. Electronic address: yhsieh13@gmail.com.
authors.forename: Yee-Hsee
authors.initials: YH
authors.lastname: Hsieh
authors.affiliation: Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Case Western Reserve University, Cleveland, Ohio, United States; Division of Pulmonary, Critical Care and Sleep Medicine, Louis Stokes VA Medical Center, Cleveland, Ohio, United States.
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Jacono
authors.affiliation: Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio, United States; Department of Neurosciences, Case Western Reserve University, Cleveland, Ohio, United States.
authors.forename: Ruth E
authors.initials: RE
authors.lastname: Siegel
authors.affiliation: Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Case Western Reserve University, Cleveland, Ohio, United States; Department of Neurosciences, Case Western Reserve University, Cleveland, Ohio, United States.
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Dick
mesh_terms: D000818:Animals; D001794:Blood Pressure; D002908:Chronic Disease; D004195:Disease Models, Animal; D000860:Hypoxia / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D009473:Neuronal Plasticity / Q000502:physiology; D010791:Phrenic Nerve / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012119:Respiration; D013153:Splanchnic Nerves / Q000503:physiopathology; D013564:Sympathetic Nervous System / Q000503:physiopathology*
keywords: Adaptation to hypoxia.; Hypoxia; Neural control of respiration; Neural control of sympathetic activity