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Decreased sympathoexcitation due to spinal GABA A receptor blockade in pregnant rats
Author(s) -
Heesch Cheryl M,
LlewellynSmith Ida J,
Etelvino Gisele M
Publication year - 2011
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.25.1_supplement.846.1
In pregnancy, arterial baroreflex sympathoexcitation is attenuated; but baseline sympathetic nerve activity (SNA) is slightly elevated. Baroreflex independent GABAergic inhibition of renal (R) SNA and mean arterial pressure (MAP) is greater in the rostral ventrolateral medulla (RVLM), but less in the paraventricular nucleus (PVN), of near‐term pregnant (P) compared to nonpregnant (NP) rats. Spinal sympathetic preganglionic neurons (SPNs) receive local GABAergic inputs. This study evaluated the role of spinal GABA A mechanisms in pregnancy. Anesthetized rats were artificially ventilated, paralyzed, and implanted with intrathecal (i.t., tip at T10), femoral arterial and venous catheters. In 11 NP (estrus) and 10 P (day 21) urethane anesthetized rats dose dependent increases in MAP due to i.t. GABA A receptor blockade (bicuculline, Bic), were significantly attenuated in P rats: 2.5mM (+16 ± 3 vs +5 ± 3 mmHg); 5 mM (+32 ±4 vs +18 ±5 mmHg); 10 mM (+68 ± 3 vs +44 ± 6 mmHg). In 7 NP and 6 P inactin anesthetized rats both pressor and RSNA responses to i.t. Bic were attenuated by pregnancy. MAP: 2.5 mM (+29 ± 6 vs +15 ± 6 mmHg); 5 mM (+57 ± 2.5 vs +36 ± 6 mmHg). RSNA: 2.5 mM (+31 ± 16 vs +7 ± 7 %); 5 mM (+60 ± 16 vs +21 ± 11 %). Thus, decreased GABAergic inhibition of sympathetic preganglionic neurons in P rats may play a role in maintenance of sympathetic outflow in pregnancy. [Support = NIH‐HL091164, CMH; NHMRC of Australia, ILS]