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INCREASED EXCITABILITY OF RVLM‐PROJECTING HYPOTHALAMIC PVN NEURONS IN ANGIOTENSIN II‐SALT HYPERTENSIVE RATS.
Author(s) -
Chen QingHui,
Dong Ying,
Cardoso Leonardo,
Shi Peng,
Calderon Alfredo S,
Andrade Mary A,
Toney Glenn M
Publication year - 2008
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.22.1_supplement.953.2
Subject(s) - muscimol , endocrinology , medicine , rostral ventrolateral medulla , agonist , chemistry , angiotensin ii , patch clamp , electrophysiology , receptor , central nervous system , medulla oblongata
The contribution of the hypothalamic PVN to maintenance of SNA and high blood pressure (BP) in rats with Ang II‐salt HT was investigated in anesthetized rats by microinjecting the GABA‐A receptor agonist muscimol bilaterally into the PVN. Muscimol significantly (P<0.05) reduced renal SNA (51±5%) and MAP (27±10 mmHg) in rats with Ang II‐salt HT (n=3). In contrast, muscimol had no effect on renal SNA and produced a blunted fall of MAP (−15±5 mmHg, P<0.05) in normotensive rats (n=6). These data indicate an enhanced role for PVN neuronal activity in maintaining renal SNA and BP in rats with Ang II‐salt HT. Consistent with this interpretation, whole‐cell patch‐clamp recordings from brain slices revealed that excitability of RVLM‐projecting pre‐sympathetic PVN neurons from rats with Ang II‐salt HT was enhanced compared to neurons from normotensive controls. Indeed, graded current injections (50, 100, 150, 200 pA; 800 ms) evoked graded increases in action potential discharge frequency among neurons of both groups. Maximum discharge was evoked by 200 pA injections and averaged 47 ± 5 Hz in neurons from rats with Ang II‐salt HT (n=9). This response was significantly higher (P<0.05) than that of neurons from normotensive controls, which averaged 25 ± 3 Hz (n=12). We conclude that increased excitability of PVN‐RVLM neurons may contribute to sympathetic activation and maintenance of Ang II‐salt HT. Support: HL076312 (NCDC)