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Increased Dietary Salt Intake Enhances Sympathoexcitatory and Sympathoinhibitory Responses Evoked from the Rostral Ventrolateral Medulla (RVLM)
Author(s) -
Adams Julye M,
Stocker Sean D
Publication year - 2007
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.21.6.a891-d
Subject(s) - rostral ventrolateral medulla , splanchnic , medicine , endocrinology , blood pressure , stimulation , splanchnic nerves , sympathetic nervous system , mean arterial pressure , heart rate , chemistry , hemodynamics
Increased dietary salt enhances pressor responses evoked by stimulation of the RVLM. The present study sought to determine whether this enhanced pressor effect is directly attributed to an exaggerated response in sympathetic nerve activity (SNA). Male Sprague Dawley rats were fed normal chow (0.4% NaCl) and given access to either 1% NaCl (SALT, n=15) or water (CON, n=14) for 2 wks. Baseline mean arterial blood pressure (MABP) was not different between SALT and CON groups (121±5 vs 110±2 mmHg). As expected, injection of glutamate (100nl) into the RVLM produced a significantly greater increase in MABP of SALT versus CON rats at 0.1nmol (19±1 vs 9±1 mmHg), 1.0nmol (42±3 vs 25±1 mmHg), and 3.0nmol (64±2 vs 37±2 mmHg, p values<0.001). This was associated with a significantly greater increase in renal SNA of SALT versus CON rats at 0.1nmol (85±6 vs 40±10%), 1.0nmol (107±10 vs 86±17%), and 3.0nmol (179±27 vs 91±23%, p values<0.01). Splanchnic SNA was also exaggerated in SALT versus CON rats at 0.1nmol (76±7 vs 49±4%), 1.0nmol (157±18 vs 97±8%), and 3.0nmol (278±35 vs 128±14%, p values<0.02). Conversely, injection of 0.1nmol GABA in SALT (n=3) versus CON (n=4) rats produced a significantly greater decrease in MABP (−14±1 vs −7±1mmHg), renal SNA (−34±1 vs −27±1%), and splanchnic SNA (−44±3 vs −32±2%, p values<0.05). These findings indicate that increased dietary salt enhances both sympathoexcitatory and sympathoinhibitory responses evoked from the RVLM.