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Carotid Chemoreceptor Control of Muscle Sympathetic Nerve Activity in Hypobaric Hypoxia
Author(s) -
Fisher James P,
Flück Daniela,
Hilty Matthias P,
Lundby Carsten
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.841.14
Subject(s) - microneurography , anesthesia , saline , medicine , chemoreceptor , mean arterial pressure , carotid body , blood pressure , hypoxia (environmental) , effects of high altitude on humans , heart rate , chemistry , anatomy , stimulation , baroreflex , oxygen , receptor , organic chemistry
High altitude hypoxia causes sympathoexcitation in humans, but the underlying mechanisms remain unclear. In this study we tested the hypothesis that muscle sympathetic nerve activity (MSNA) would be lowered at high altitude when carotid chemoreceptor activity is reduced by intravenous dopamine infusion. Nine healthy individuals (mean [SD]; 26 [4] yr, 179 [9] cm, 75 [10] kg, 1 women) were studied at sea level (Zurich) and at the Jungfraujoch research station (3454 m), 15–17 days after arrival. Intravenous infusions of a placebo (saline) and dopamine (3 μg/(kg*min)) were administered on both study days, according to a single blind design. Minute ventilation (V E ) and the partial pressure of end‐tidal oxygen (P ET O 2 ) and carbon dioxide (P ET CO 2 ) were measured breath‐by‐breath (Cosmed). Mean arterial pressure (MAP), cardiac output (CO) and total peripheral resistance (TPR) were recorded on a beat‐to‐beat basis via finger photoplethysmography (Nexfin) and multi‐unit recordings of MSNA were obtained using peroneal microneurography (ADInstruments). Sojourn to high altitude decreased P ET O 2 (mean±SE; saline, 93±1 to 60±1; dopamine, 91±1 to 57±1 mmHg), P ET CO 2 (saline, 40±1 to 31±0.4; dopamine, 41±1 to 32±1 mmHg) and increased V E (saline, 8.6±0.5 to 11.3±0.6; dopamine, 8.2±0.5 to 10.6±0.8 L· min −1 ) (P<0.05). MAP (saline, 82±4 to 91±3; dopamine, 82±4 to 91±3 mmHg) and MSNA burst frequency (saline, 16±3 to 28±4; dopamine, 16±4 to 31±4 bursts· min −1 ) were also increased at altitude, while CO (saline, 7.4±0.5 to 7.7±0.4; dopamine, 8.3±0.5 to 8.3±0.3 L· min −1 ) was unchanged, and TPR was decreased (saline, 15.1±1 to 14.7±1; dopamine, 14.7±1 to 12.7±1 L· min −1 ) (P<0.05). Dopamine infusion increased CO, decreased TPR, but had no effect on either MAP or MSNA burst frequency (P<0.05). These data suggest that high altitude‐mediated increases in MSNA are not attributable to a dopaminergic mechanism.