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Pregnancy Decreases Myogenic Activity of Brain Parenchymal Arterioles: Role of Estrogen

Godfrey. Neurology, Ob/Gyn and Pharmacology, University of Vermont, Burlington, VT

ABSTRACT

This study investigated the influence of pregnancy and estrogen on myogenic activity of brain parenchymal arterioles (PA). PA were dissected from Sprague Dawley rats that were nonpregnant (NP, n=6), late-pregnant (LP, n=6), ovariectomized and implanted with estriol (5.0 mg) + estradiol (0.5 mg) pellets for 2 weeks (OVX+E, n=8) to obtain levels of pregnancy or OVX implanted with a placebo pellet (OVX, n=6). PA were mounted on glass cannulas within an arteriograph chamber and lumen diameter recorded at intravascular pressures from 25–200 mmHg. Pregnancy significantly increased active diameters of PA, that also underwent forced dilatation at lower pressures vs. all groups. The active diameters of PA from LP vs. NP, OVX+E and OVX animals at 100 mmHg was (µm): 64±6 vs. 49±4, 42±3 and 42±3 (p<0.05). In addition, PA from LP animals had significantly diminished tone vs. all groups whereas the tone in OVX was increased vs. NP. The percent tone at 100 mmHg for LP vs. NP, OVX+E and OVX animals at 100 mmHg was: 34±5 vs. 44±3 (p<0.05 vs. LP), 52±1 (p<0.05 vs. LP) and 54±2 (p<0.05 vs. NP and LP). These results demonstrate that pregnancy diminishes myogenic activity of brain PA, an effect that was not related to elevated estrogen. The larger lumen of PA during pregnancy could decrease small vessel resistance and predispose the brain to hyperperfusion when blood pressure is elevated, as in eclampsia. Supported by RO1 NS045940 and AHA EI 0540081N.

This Article Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Cipolla, M. J. Articles by A, J. PubMed Articles by Cipolla, M. J. Articles by A, J.