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Discharge of RVLM Vasomotor Neurons is Increased in Angiotensin II – Salt Hypertensive Rats: Selective Modulation of a Functionally Identified Group of Neurons
Author(s) -
Pedrino Gustavo R,
Calderon Alfredo S,
Andrade Mary Ann,
Cravo Sergio L,
Toney Glenn M
Publication year - 2009
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.23.1_supplement.958.12
Subject(s) - vasomotor , baroreceptor , medicine , endocrinology , bursting , angiotensin ii , rostral ventrolateral medulla , chemistry , electrophysiology , extracellular , renin–angiotensin system , anesthesia , heart rate , blood pressure , biology , neuroscience , biochemistry
In rats consuming a 2% NaCl diet and treated with ANG II (150 ng/kg/min, s.c.; n = 28), MAP increased from 103 ± 1.6 to 133 ± 3.5 mmHg. Extracellular recording was used in anesthetized rats to assess effects of ANG II + Salt on the discharge of RVLM vasomotor neurons. Among cells with baro‐inhibitable and cardiac rhythmic discharge, spontaneous firing rate (SFR) was similar in hypertensive (HT: 8.0 ± 2.1 Hz; n=20) and normotensive (NT: 9.5 ± 1.8 Hz; n = 35) rats. However, a greater (P<0.01) increase of MAP was needed to silence discharge in HT (44 ± 4.9 mmHg) than NT (29 ± 3 mmHg) rats. The maximum firing rate (MFR) achieved when arterial baroreceptors were unloaded was similar across groups (HT: 15.3 ± 4.1 Hz, NT: 17.4 ± 4.1 Hz). In another group of cells discharge was baro‐inhibitable, but was not cardiac rhythmic. Among these cells, SFR was significantly (P<0.0001) higher in HT (19.6 ± 2.6 Hz; n=34) than NT (8.1 ± 1.1 Hz; n=35) rats. The increase in MAP needed to silence discharge, and the MFR during baro‐unloading were also higher (P<0.01) in HT (58 ± 5.6 mmHg; 38.9 ± 6.2 Hz) than NT (39 ± 4.1 mmHg; 12.5 ± 2.2 Hz) rats. This group consisted mostly of non‐C1cells with bursting discharge. Burst discharge was phase‐locked to the frequency of respiratory drive. We conclude that discharge of non‐cardiac rhythmic RVLM vasomotor neurons with respiratory‐driven bursting activity is increased in rats with ANG II + Salt hypertension.