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Gain of baroreflex control of heart rate decreases during late pregnancy in rats
Author(s) -
Mulvaney J M,
Brooks V L,
Roberts D,
Chapleau M W,
Goldman R K
Publication year - 2007
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.21.5.a512-b
Subject(s) - baroreflex , mean arterial pressure , phenylephrine , gestation , heart rate , blood pressure , medicine , pregnancy , anesthesia , endocrinology , cardiology , biology , genetics
Baroreflex sensitivity (BRS) becomes impaired at the end of gestation in rabbits, and this reduction may be mediated by the concurrent development of insulin resistance. Rats also develop insulin resistance near term, but if and when BRS decreases during pregnancy in the rat is unknown. To test the hypothesis that BRS falls near the end of gestation, we measured arterial pressure telemetrically (1000 Hz) during several 24 hr periods in female rats (n=3) first in the non‐pregnant state (NP), and then during pregnancy. BRS was calculated using the sequence method, which analyzes spontaneous ramps in systolic pressure and associated beat to beat changes in pulse interval. Mean arterial pressure (MAP, mmHg) decreased from 100±6 (mean of 4–5 days NP) to 75±2 (mean of gestational days 20–21; term is 21–22 days), and heart rate (HR, bpm) increased from 400±7 (NP) to 441±19 (days 20–21; each P<0.01). Similarly, BRS decreased from 2.1±0.5 (NP) to 1.6±0.3 ms/mmHg (days 20–21; P<0.05). However, at days 13–14 of gestation, BRS (1.9±0.5 ms/mmHg), MAP (97±4 mmHg) and HR (409±9 bpm) were not different from NP. In order to confirm the BRS telemetry data, separate groups of rats were studied using the pharmacological method. Entire sigmoidal baroreflex curves were generated using slow ramp infusions of nitroprusside and phenylephrine, to determine the HR response from a decrease and increase in MAP, respectively. In confirmation of telemetric BRS measurements, maximal BRS was decreased (P<0.05) from 3.9±0.5 (NP) to 1.9±0.4 bpm/mmHg (days 19–20). We conclude that BRS decreases at the end of gestation in rats, which correlates temporally with established changes in insulin resistance. Supported by NIH HL70962, MRF, and Collins Fdn.