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Role of subfornical organ AT 1 receptors in control of blood pressure and sympathetic outflow in pregnant rats
Author(s) -
Kvochina Lyudmyla,
Heesch Cheryl M.
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.a774-b
Subject(s) - subfornical organ , medicine , endocrinology , blood pressure , angiotensin ii , microinjection , angiotensin ii receptor type 1 , heart rate , receptor , sympathetic nervous system , mean arterial pressure , renin–angiotensin system , chemistry
Baseline blood pressure is decreased, but sympathetic tone to the heart and vasculature is well maintained or slightly elevated in term pregnant animals. CNS mechanisms for maintaining baseline sympathetic tone during pregnancy are not known. However, circulating angiotensin II (AII) is elevated in pregnancy and blood borne AII is known to activate AT1 receptors in the subfornical organ (SFO) and produce sympathoexcitation. We hypothesized that if elevated circulating AII contributed to maintenance of arterial blood pressure and sympathetic nerve activity in pregnancy, the sympatho‐inhibition to blocking AT1 receptors in the SFO would be greater in term pregnant (P) compared to virgin (V) rats. In V (n=7) and P (n=6) inactin anesthetized rats responses to microinjection of A II (20 ìM; 50 nl) into the SFO were determined before and after SFO AT1 receptor blockade (AT1X) (L‐158,809, 20 mM; 100 nl). Baseline mean arterial pressure (MAP) was lower (P= 81.3±5.0; V= 96.4±2.2 mm Hg) and heart rate was higher (P=367±9.4; V=329±12.4 bpm) in P compared to V rats. The pressor response to SFO A II tended to be greater in P (+ 10.7±1.8 mm Hg) compared to V (+8.2±0.7 mm Hg) rats and was blocked by AT1X in both groups. Depressor responses to AT1X in the SFO were significant and not different between groups (P: −7.2±1.0 mm Hg; V: −6.3±0.8 mm Hg). The modest decrease in renal sympathetic nerve activity following AT1X was significant in P (−11.4±2.9%) but not V (−6.2±4.4%) rats. Although responses were small, these results suggest that tonic sympathoexcitatory actions of AII at the SFO may contribute to maintenance of sympathetic nerve activity in P animals. (NIH HL36245)