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Salt loading increases the muscle sympathetic nerve activity response to upright tilt: a pilot study (1170.3)
Author(s) -
Best Stuart,
Okada Yoshiyuki,
Parker Rosemary,
Bivens Tiffany,
Fu Qi
Publication year - 2014
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.28.1_supplement.1170.3
Subject(s) - microneurography , supine position , heart rate , baroreflex , medicine , stroke volume , blood pressure , endocrinology , sympathetic nervous system , baroreceptor , anesthesia
Increased sodium intake reduces resting muscle sympathetic nerve activity (MSNA). We hypothesized that the increase in MSNA during upright tilt would be greater following a high sodium (HS) diet compared to a low sodium (LS) diet. Six healthy women (40±6[SD]yrs) were tested following a 7 day HS (5750mgNa + /day) and 7 day LS diet (1150mgNa + /day) in randomized order during the mid‐luteal phase. Blood pressures (BP, SunTech), heart rate (HR, ECG), cardiac output (Qc, C 2 H 2 rebreathing) and MSNA (microneurography) were measured at rest, 30 o and 60 o head‐up tilt. Stroke volume (SV) and total peripheral resistance (TPR) were calculated. BP was similar at supine and 30 o but higher at 60 o following the HS when compared to LS diet. HR, Qc, SV and TPR were similar following each diet. Supine MSNA burst frequency and burst incidence (BI) respectively were lower following the HS (13±8 bursts.min ‐1 , 22±13 bursts.100beats ‐1 ) than the LS diet (22±10 bursts.min ‐1 , 36±18 bursts.100beats ‐1 ). The increase in BI from baseline to 60 o was greater after the HS (28±4 bursts.100beats ‐1 ) than the LS diet (22±11 bursts.100beats ‐1 ). These preliminary results suggest a HS diet may enhance the MSNA response and increase BP during orthostasis in healthy women. This could be due to greater sympathetic vasoconstrictor reserve and/or alteration of the sympathetic baroreflex following the HS diet.