title: Visualizing oxidative stress-induced depression of cardiac vagal baroreflex by MRI/DTI in a mouse neurogenic hypertension model.
abstract: A clinical hallmark of hypertension is impairment of the cardiac vagal baroreflex, which maintains stable blood pressure and heart rate under physiological conditions. There is also evidence that oxidative stress in the brain is associated with neurogenic hypertension. We tested the hypothesis that an augmented superoxide level in the nucleus tractus solitarii (NTS), the terminal site of baroreceptor afferents, contributes to the depression of cardiac vagal baroreflex by disrupting the connectivity between the NTS and the nucleus ambiguus (NA), the origin of the vagus nerve, during neurogenic hypertension. An experimental model of neurogenic hypertension that employed intracerebroventricular infusion of angiotensin II in male adult C57BL/6 mice was used. Based on tractographic evaluations using magnetic resonance imaging/diffusion tensor imaging of the medulla oblongata in the brain stem, we found that the connectivity between the NTS and NA was disrupted in neurogenic hypertension, concurrent with impairment of the cardiac vagal baroreflex as detected by radiotelemetry. We further found that the disrupted NTS-NA connectivity was reversible, and was related to oxidative stress induced by augmented levels of NADPH oxidase-generated superoxide in the NTS. We conclude that depression of the cardiac vagal baroreflex induced by oxidative stress in the NTS in the context of neurogenic hypertension may be manifested in the form of dynamic alterations in the connectivity between the NTS and NA.
authors.affiliation: Center for Translational Research in Biomedical Sciences, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung, Taiwan, ROC.
authors.forename: Ching-Yi
authors.initials: CY
authors.lastname: Tsai
authors.forename: Chia-Hao
authors.initials: CH
authors.lastname: Su
authors.forename: Véronique
authors.initials: V
authors.lastname: Baudrie
authors.forename: Dominique
authors.initials: D
authors.lastname: Laude
authors.forename: Jun-Cheng
authors.initials: JC
authors.lastname: Weng
authors.forename: Alice Y W
authors.initials: AY
authors.lastname: Chang
authors.forename: Julie Y H
authors.initials: JY
authors.lastname: Chan
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Elghozi
authors.forename: Samuel H H
authors.initials: SH
authors.lastname: Chan
mesh_terms: D000818:Animals; D017704:Baroreflex / Q000502:physiology*; D056324:Diffusion Tensor Imaging; D004195:Disease Models, Animal; D006973:Hypertension / Q000503:physiopathology*; D007091:Image Processing, Computer-Assisted; D047468:Immunoprecipitation; D008279:Magnetic Resonance Imaging; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D009434:Neural Pathways / Q000503:physiopathology*; D018384:Oxidative Stress / Q000502:physiology*; D017552:Solitary Nucleus / Q000503:physiopathology*; D014630:Vagus Nerve / Q000503:physiopathology
keywords: Cardiac vagal baroreflex; Diffusion tensor imaging; Magnetic resonance imaging; Neurogenic hypertension; Nucleus ambiguus; Nucleus tractus solitarii; Oxidative stress