Cerebral artery reactivity changes during pregnancy and the postpartum period: a role in eclampsia?
Open Access
- 1 June 2004
- journal article
- Published by American Physiological Society in American Journal of Physiology-Heart and Circulatory Physiology
- Vol. 286 (6), H2127-H2132
- https://doi.org/10.1152/ajpheart.01154.2003
Abstract
Eclampsia is thought to be similar to hypertensive encephalopathy, whereby acute elevations in intravascular pressure cause forced dilatation (FD) of intrinsic myogenic tone of cerebral arteries and arterioles, decreased cerebrovascular resistance, and hyperperfusion. In the present study, we tested the hypothesis that pregnancy and/or the postpartum period predispose cerebral arteries to FD by diminishing pressure-induced myogenic activity. We compared the reactivity to pressure (myogenic activity) as well as factors that modulate the level of tone of third-order branches ( 0.05). This level of myogenic activity was maintained in the NP arteries at all pressures; however, both LP and PP arteries dilated at considerably lower pressures compared with NP, which lowered the pressure at which FD occurred from >175 for NP to 146 ± 6.5 mmHg for LP ( P < 0.01 vs. NP) and 162 ± 7.7 mmHg for PP ( P < 0.01 vs. NP). The amount of myogenic tone was also significantly diminished at 175 mmHg compared with NP: percent tone for NP, LP, and PP animals were 35 ± 2, 11 ± 3 ( P < 0.01 vs. NP), and 20 ± 7% ( P < 0.01 vs. NP), respectively. Inhibition of nitric oxide (NO) with 0.1 mM Nω-nitro-l-arginine (l-NNA) caused constriction of all vessel types that was significantly increased in the PP arteries, which demonstrates significant basal NO production. Reactivity to 5-hydroxytryptamine (serotonin) was assessed in the presence of l-NNA and indomethacin. There was a differential response to serotonin: PCAs from NP animals dilated, whereas LP and PP arteries constricted. These results suggest that both pregnancy and the postpartum period predispose the cerebral circulation to FD at lower pressures, a response that may lower cerebrovascular resistance and promote hyperperfusion when blood pressure is elevated, as occurs during eclampsia.Keywords
This publication has 39 references indexed in Scilit:
- Summary of the NHLBI Working Group on Research on Hypertension During PregnancyHypertension, 2003
- Changes in flow velocity, resistance indices, and cerebral perfusion pressure in the maternal middle cerebral artery distribution during normal pregnancyActa Obstetricia et Gynecologica Scandinavica, 2001
- Multiple Microvascular and Astroglial 5-Hydroxytryptamine Receptor Subtypes in Human Brain: Molecular and Pharmacologic CharacterizationJournal of Cerebral Blood Flow & Metabolism, 1999
- Diffusion-weighted images and vasogenic edema in eclampsia1Obstetrics & Gynecology, 1999
- Vascular Smooth Muscle Actin Cytoskeleton in Cerebral Artery Forced DilatationStroke, 1998
- Invited Review: The Brain in EclampsiaHypertension in Pregnancy, 1994
- Regulation of Arterial Tone by Activation of Calcium-Dependent Potassium ChannelsScience, 1992
- Clinicopathological study of neurological complications due to hypertensive disorders of pregnancy.Journal of Neurology, Neurosurgery & Psychiatry, 1988
- Active management of the unconscious eclamptic patientBJOG: An International Journal of Obstetrics and Gynaecology, 1986
- The obligatory role of endothelial cells in the relaxation of arterial smooth muscle by acetylcholineNature, 1980