title: Central correlation of muscle sympathetic nerve activation during baroreflex unloading - a microneurography-positron emission tomography study.
abstract: The baroreceptor reflex controls spontaneous fluctuations in blood pressure. One major control variable of the baroreflex is the sympathetic vasoconstrictor activity to muscles [MSNA; burst frequency (BF) and burst incidence (BI)], which can be quantitatively assessed by microneurography. We aimed to investigate the central regions involved in baroreflex regulation of MSNA. Healthy men (mean age 25 years) participated in three experimental sessions. (i) Microneurography recordings of MSNA from the left peroneal nerve during rest and baroreflex unloading, induced by lower body negative pressure (LBNP; -40 mmHg). If MSNA could be reliably recorded throughout this procedure (n = 15), the subjects entered the positron emission tomography (PET) experiments. The two PET sessions took place in a randomised order. Cerebral glucose metabolism (18-fluorodeoxyglucose) was analysed after: (ii) baroreflex unloading (LBNP); and (iii) control condition (lying in the LBNP chamber without suction). The PET data were analysed employing SPM8. LBNP elicited a significant increase in MSNA in all successfully recorded subjects (BI: P = 0.001; F = 5.54; BF: P < 0.001; F = 36.59). As compared with the control condition, LBNP was associated with increased PET regional glucose metabolism bilaterally in the orbitofrontal cortex (OFC; BA 11, 47). Related to the rise of BF, there was increased activation of the left OFC (BA 11); related to the rise of BI there was increased activation of the brainstem corresponding to the rostral ventrolateral medulla. Our data support a role for the ventrolateral medulla and the OFC in baroreflex-mediated control of MSNA in humans.
authors: Department of Neurology, Justus Liebig University, Klinikstrasse 33, 35392, Giessen, Germany; Department of Neurology, University Medical Center, Johannes Gutenberg-University, 56101, Mainz, Germany.
authors: Heidrun H
authors: HH
authors: Krämer
authors: Stephan-Johann
authors: SJ
authors: Ament
authors: Markus
authors: M
authors: Breimhorst
authors: Andre
authors: A
authors: Klega
authors: Katharina
authors: K
authors: Schmieg
authors: Corina
authors: C
authors: Endres
authors: Hans-Georg
authors: HG
authors: Buchholz
authors: Mikael
authors: M
authors: Elam
authors: Mathias
authors: M
authors: Schreckenberger
authors: Frank
authors: F
authors: Birklein
mesh_terms: D000328:Adult; D017704:Baroreflex; D001921:Brain / Q000000981:diagnostic imaging / Q000378:metabolism / Q000502:physiology*; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D009928:Organ Specificity; D010543:Peroneal Nerve / Q000502:physiology*; D049268:Positron-Emission Tomography
chemical_list: D005947:Glucose
keywords: autonomic control; muscle sympathetic nerve activity; orbitofrontal cortex; rostral ventrolateral medulla