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Sympathoexcitation due to angiotensin II in the subfornical organ is increased by pregnancy and requires ionotropic glutamate receptors in the rostral ventrolateral medulla
Author(s) -
Kvochina Lyudmyla I.,
Hasser Eileen M.,
Heesch Cheryl 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.1169.5
Subject(s) - rostral ventrolateral medulla , subfornical organ , medicine , endocrinology , ionotropic effect , microinjection , medulla oblongata , angiotensin ii , chemistry , glutamate receptor , receptor , blood pressure , heart rate , central nervous system
Baroreflex sympathoexcitation is blunted, but baseline sympathetic tone is elevated in term pregnancy. Circulating angiotensin II (A II), which is increased in pregnancy, activates AT 1 receptors in the subfornical organ (SFO). A projection from SFO to paraventricular nucleus (PVN) then to rostral ventrolateral medulla (RVLM) mediates sympathoexcitation. A role for A II at all sites has been proposed, but a recent study found mainly glutamatergic PVN to RVLM projections. We tested the role of RVLM inotropic glutamate (Glu) receptors to responses to microinjection of A II into the SFO of 4 nonpregnant (NP) and 3 term pregnant (P) sinoaortic denervated inactin anesthetized rats. Baseline mean arterial pressure (MAP) was lower (P= 71 ±5; NP= 103 ±1 mmHg) and heart rate higher (P = 312 ±10; NP = 278 ±8 bpm) in P rats. The increase in MAP and lumbar sympathetic nerve activity (LSNA) in response to A II (20 μM, 50 nl) in the SFO was greater in P rats (δMAP: P = +23 ±1; NP = +17 ±3 mmHg. δLSNA: P = +27 ±6; NP = +14 ±1%). Bilateral microinjection of the inotropic Glu antagonist, kynurenate (KYN, 40 mM, 100 nl) into the RVLM had no effect alone, but eliminated responses to SFO A II in both groups (δMAP: P = +2 ±2; NP = + 5 ±1 mmHg. LSNA: P = +2 ±1; NP = +3 ±1 %). Responses to A II in the SFO recovered 45 min later. Thus, RVLM inotropic Glu receptors are required for sympathoexcitation mediated by SFO A II. (NIH HL 36245; MU #URC‐06‐049).