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Activation of paraventricular nucleus by water deprivation: roles of angiotensin II and glutamate
Author(s) -
Brooks Virginia L.,
Freeman Korrina L.
Publication year - 2006
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.20.4.a361
Subject(s) - endocrinology , medicine , angiotensin ii , chemistry , candesartan , muscimol , valsartan , glutamate receptor , agonist , plasma osmolality , microinjection , receptor , vasopressin , blood pressure
Water deprivation activates sympathoexcitatory neurons in the paraventricular nucleus (PVN); however, the neurotransmitters that mediate this activation are unknown. To test the hypothesis that PVN neurons are excited by angiotensin II (AngII), the AngII type 1 receptor (AT1R) antagonists, candesartan (100 pmol) and valsartan (100 pmol), were microinjected bilaterally in water deprived (WD) and water replete (WR) urethane‐anesthetized rats. To investigate the role of glutamate (GLU), the GLU receptor antagonist, kynurenic acid (7.2 nmol), was microinjected. Water deprivation increased (P<0.001) plasma levels of sodium (in meq/L: 143.5±0.5, WD; 138.2±0.4, WR), chloride (in meq/L: 110.1±0.3, WD; 104.8±0.5, WR), osmolality (in mosmol/L: 311±1, WD; 303±1, WR), protein (in g/dL: 6.0±0.1, WD; 5.0±0.1, WR) and hematocrit (in %: 49.2±0.5, WD; 42.8±0.5, WR). Nonspecific inhibition of the PVN with bilateral microinjection of the GABAA agonist, muscimol (100 pmol), decreased BP more (P<0.05) in WD (−26±6 mmHg, n=5) than in WR (−7±2 mmHg, n=4) rats, confirming that PVN supports BP during water deprivation. In WD rats (n=8), PVN candesartan slowly decreased BP (P<0.05) by 8±1 mmHg, reaching a nadir after 13±1 min; however, in WR rats (n=6), BP was not altered (0±2 mmHg). Similarly, valsartan decreased BP by 5±1 mmHg after 14±1 min in WD rats (n=7; P<0.05), but was ineffective in WR rats (−1±1 mmHg, n=4). In WD rats, kynurenic acid produced a marked hypotensive response (−23±8 mmHg, n=6) that was significantly greater (P<0.05) than in WR rats (−4±1 mmHg, n=5). In conclusion, increased activity of AT1R and GLU receptors in PVN support BP during water deprivation. Supported by HL35872 and HL70962.