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Inhibition Of The Estrogen‐Mediated Cardiac Vagal Control Accounts For The Baroreflex Depressant Effect Of Chronic Nicotine In Female Rats
Author(s) -
El-Mas Mahmoud M,
El-Gowelli Hanan M,
Fouda Mohamed A,
El-gowilly Sahar M
Publication year - 2012
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.26.1_supplement.1124.9
Subject(s) - baroreflex , nicotine , endocrinology , chronotropic , medicine , phenylephrine , ovariectomized rat , estrogen , heart rate , reflex , blood pressure , estrogen receptor , chemistry , breast cancer , cancer
We previously showed that chronic nicotine dose‐dependently attenuated reflex chronotropic responses in female rats. Here the hypothesis was tested that impairment of the estrogen‐dependent cardiomotor vagal control mediates the nicotine‐baroreflex interaction. Baroreflex curves relating changes in heart rate to increases (phenylephrine, PE) or decreases (sodium nitroprusside, SNP) in blood pressure were constructed in sham‐operated, ovariectomized (OVX), and estrogen‐replaced OVX (OVXE 2 ) rats. Slopes of the curves were taken as a measure of baroreflex sensitivity (BRS PE and BRS SNP ). In sham rats, nicotine (2 mg/kg/day for 14 days) produced no changes in basal BP but reduced BRS PE and BRS SNP , suggesting attenuation of reflex bradycardic and tachycardic responses. Compared with sham rats, OVX selectively decreased BRS PE but not BRS SNP and abolished the nicotine‐induced impairment of both responses. The effects of OVX were reversed after treatment with estrogen or with the estrogen receptor modulator raloxifene. Atropine reduced BRS to comparable levels in all rat preparations regardless of the estrogen or nicotine milieu. Thus, nicotine attenuates reflex chronotropic activity via inhibition of the estrogen‐mediated facilitation of vagal cardiomotor activity. This project was supported financially by the Science and Technology Development Fund (STDF), Egypt, Grant No. 502.