Circulatory response to systemic infusion of norepinephrine in the pregnant ewe

Effects of Vasoactive Medications and Maternal Positioning During Cesarean Delivery on Maternal Hemodynamics and Neonatal Acid-Base Status

Maternal hemodynamics, positioning, and anesthesia technique for cesarean delivery influence neonatal acid-base balance; direct effects from drugs that cross the placenta also have an influence. Spinal anesthesia limits fetal exposure to depressant drugs and avoids maternal airway instrumentation, but is associated with hypotension. Hypotension may be prevented/treated with vasopressors and intravenous fluids. Current evidence supports phenylephrine as the first-line vasopressor. Fifteen degrees of lateral tilt during cesarean delivery has been advocated to relieve vena caval obstruction, but routine use may be unnecessary in healthy nonobese women having elective cesarean delivery if maternal blood pressure is maintained near baseline.

Maternal uterine vascular remodeling during pregnancy

Remodeling of the maternal uterine vasculature during pregnancy is a unique cardiovascular process that occurs in the adult and results in significant structural and functional changes in large and small arteries and veins, and in the creation of the placenta--a new fetomaternal vascular organ. This expansive, hypertrophic process results in increases in both lumen circumference and length, and is effected through a combination of tissue and cellular hypertrophy, endothelial and vascular smooth muscle hyperplasia, and matrix remodeling. This review summarizes what is currently known about the time course and extent of the remodeling process, and how local vs. systemic factors influence its genesis. The main focus is on upstream maternal vessels rather than spiral artery changes, although the latter are considered from the overall hemodynamic perspective. We also consider some of the underlying mechanisms and provide a hypothetical scenario that integrates our current knowledge. Abrogation of this adaptive vascular process is associated with several human gestational pathologies such as preeclampsia and intrauterine growth restriction (IUGR), which not only raise the risk of infant mortality and morbidity but are also a significant source of maternal mortality and susceptibility to cardiovascular and other diseases for both mother and neonate later in life.

Enhanced contractility in pregnancy is associated with augmented TRPC3, L-type, and T-type voltage-dependent calcium channel function in rat uterine radial artery

In pregnancy, α-adrenoceptor-mediated vasoconstriction is augmented in uterine radial arteries and is accompanied by underlying changes in smooth muscle (SM) Ca2+ activity. This study aims to determine the Ca2+ entry channels associated with altered vasoconstriction in pregnancy, with the hypothesis that augmented vasoconstriction involves transient receptor potential canonical type-3 (TRPC3) and L- and T-type voltage-dependent Ca2+ channels. Immunohistochemistry showed TRPC3, L-type Cav1.2 (as the α1C subunit), T-type Cav3.1 (α1G), and Cav3.2 (α1H) localization to the uterine radial artery SM. Fluorescence intensity of TRPC3, Cav1.2, and Cav3.2 was increased, and Cav3.1 decreased in radial artery SM from pregnant rats. Western blot analysis confirmed increased TRPC3 protein expression in the radial artery from pregnant rats. Pressure myography incorporating pharmacological intervention to examine the role of these channels in uterine radial arteries showed an attenuation of phenylephrine (PE)-induced constriction with Pyr3 {1-[4-[(2,3,3-trichloro-1-oxo-2-propen-1-yl)amino]phenyl]-5-(trifluoromethyl)-1 H-pyrazole-4-carboxylic acid}-mediated TRPC3 inhibition or with nifedipine-mediated L-type channel block alone in vessels from pregnant rats; both effects of which were diminished in radial arteries from nonpregnant rats. Combined TRPC3 and L-type inhibition attenuated PE-induced constriction in radial arteries, and the residual vasoconstriction was reduced and abolished with T-type channel block with NNC 55-0396 in arteries from nonpregnant and pregnant rats, respectively. With SM Ca2+ stores depleted and in the presence of PE, nifedipine, and NNC 55-0396, blockade of TRPC3 reversed PE-induced constriction. These data suggest that TRPC3 channels act synergistically with L- and T-type channels to modulate radial artery vasoconstriction, with the mechanism being augmented in pregnancy.

Large conductance Ca2+-activated K+ channels modulate uterine α1-adrenergic sensitivity in ovine pregnancy

The uteroplacental vasculature is refractory to α-adrenergic stimulation, and large conductance Ca(2+)-activated K(+) channels (BK(Ca)) may contribute. We examined the effects of uterine artery (UA) BK(Ca) inhibition with tetraethylammonium (TEA) on hemodynamic responses to phenylephrine (PE) at 101 to 117 days and 135 to 147 days of ovine gestation, obtaining dose responses for mean arterial pressure (MAP), heart rate (HR), and uteroplacental blood flow (UPBF) and vascular resistance (UPVR) before and during UA TEA infusions. The UA α(1)-adrenergic receptors (α1-ARs) were assessed. The PE increased MAP and UPVR and decreased HR and UPBF dose dependently at both gestations (P < .001, analysis of variance). The %▵MAP was less at 135 to 147 days before and during TEA infusions (P ≤ .008); however, responses during TEA were greater (P ≤ .002). The PE increased %▵UPVR>>%▵MAP, thus %▵UPBF fell. The TEA enhanced PE-mediated increases in %▵UPVR at 135 to 147 days (P ≤ .03). The UA α(1)-AR expression was unchanged in pregnancy. Uterine vascular responses to PE exceed systemic vascular responses throughout pregnancy and are attenuated by BK(Ca) activation, suggesting BK(Ca) protect UPBF.

Differential sensitivity to angiotensin II and norepinephrine in human uterine arteries

BACKGROUND

During pregnancy, uteroplacental responses to norepinephrine (NE) exceed systemic responses. In contrast, uteroplacental responses to angiotensin II (ANG II) are less than systemic. The explanation for these differences in uteroplacental sensitivity remain unclear but may reflect type 2 ANG II receptor (AT(2)R) predominance in uterine artery (UA) vascular smooth muscle (VSM).

OBJECTIVE

The objective of the study was to examine VSM sensitivity to KCl, NE, and ANG II in UA from nonpregnant (NP) and pregnant (P) women and determine VSM ANG II receptor subtype expression.

METHODS

Responses to KCl, NE, and ANG II were examined in endothelium-denuded UA rings from NP (n = 28) and P (n = 13; 34-40 wk gestation) women, and ANG II receptor subtype, α(1)-receptor and contractile proteins were measured.

RESULTS

KCl and NE dose dependently contracted UA (P < 0.001), P exceeding NP 2-fold or greater; but α(1)-receptor expression was unchanged. ANG II did not elicit dose effects in NP or P UA; however, P responses exceeded NP approximately 2-fold (P < 0.001) and were approximately 2.5-fold less than NE (P < 0.001). AT(2)R and AT(1)R expression were similar (P > 0.1) in VSM from NP and term P women. AT(1)R blockade abolished ANG II contractions (P < 0.001); AT(2)R blockade did not enhance ANG II sensitivity in UA with or without endothelium. Actin contents increased approximately 2-fold in term UA.

CONCLUSIONS

Sensitivity to α-stimulation exceeds ANG II in NP and P UA, explaining the differential uteroplacental sensitivity in pregnancy. Because AT(2)R predominate in UA VSM throughout reproduction, this contributes to the inherent refractoriness to ANG II in the uterine vasculature. The increase in UA contractile proteins at term P suggests remodeling, explaining the enhanced contractility seen.

Defining the differential sensitivity to norepinephrine and angiotensin II in the ovine uterine vasculature

The intact ovine uterine vascular bed (UVB) is sensitive to α-agonists and refractory to angiotensin II (ANG II) during pregnancy; the converse occurs in the systemic circulation. The mechanism(s) responsible for these differences in uterine sensitivity are unclear and may reflect predominance of nonconstricting AT(2) receptors (AT(2)R) in uterine vascular smooth muscle (UVSM). The contribution of the placental vasculature also is unclear. Third generation and precaruncular/placental arteries from nonpregnant (n = 16) and term pregnant (n = 23) sheep were used to study contraction responses to KCl, norepinephrine (NE), and ANG II (with/without ATR specific inhibitors) and determine UVSM ATR subtype expression and contractile protein content. KCl and NE increased third generation and precaruncular/placental UVSM contractions in a dose- and pregnancy-dependent manner (P ≤ 0.001). ANG II only elicited modest contractions in third generation pregnant UVSM (P = 0.04) and none in precaruncular/placental UVSM. Moreover, compared with KCl and NE, ANG II contractions were diminished ≥ 5-fold. Whereas KCl and ANG II contracted third generation>>precaruncular/placental UVSM, NE-induced contractions were similar throughout the UVB. However, each agonist increased third generation contractions ≥ 2-fold at term, paralleling increased actin/myosin and cellular protein content (P ≤ 0.01). UVSM AT(1)R and AT(2)R expression was similar throughout the UVB and unchanged during pregnancy (P > 0.1). AT(1)R inhibition blocked ANG II-mediated contractions; AT(2)R blockade, however, did not enhance contractions. AT(2)R predominate throughout the UVB of nonpregnant and pregnant sheep, contributing to an inherent refractoriness to ANG II. In contrast, NE elicits enhanced contractility throughout the ovine UVB that exceeds ANG II and increases further at term pregnancy.

The effects of hydrotherapy on anxiety, pain, neuroendocrine responses, and contraction dynamics during labor

BACKGROUND

Hydrotherapy (immersion or bathing) is used worldwide to promote relaxation and decrease parturient anxiety and pain in labor, but the psychophysiological effects of this intervention remain obscure.

DESIGN

A pretest-posttest design with repeated measures was used to examine the effects of hydrotherapy on maternal anxiety and pain, neuroendocrine responses, plasma volume shift (PVS), and uterine contractions (CXs) during labor. Correlations among variables were examined at three time points (preimmersion and twice during hydrotherapy).

METHODS

Eleven term women (mean age 24.5 years) in spontaneous labor were immersed to the xiphoid in 37 degrees C water for 1 hr. Blood samples and measures of anxiety and pain were obtained under dry baseline conditions and repeated at 15 and 45 min of hydrotherapy. Uterine contractions were monitored telemetrically.

RESULTS

Hydrotherapy was associated with decreases in anxiety, vasopressin (V), and oxytocin (O) levels at 15 and 45 min (all ps < .05). There were no significant differences between preimmersion and immersion pain or cortisol (C) levels. Pain decreased more for women with high baseline pain than for women with low baseline levels at 15 and 45 min. Cortisol levels decreased twice as much at 15 min of hydrotherapy for women with high baseline pain as for those with low baseline pain. beta-endorphin (betaE) levels increased at 15 min but did not differ between baseline and 45 min. During immersion, CX frequency decreased. A positive PVS at 15 min was correlated with contraction duration.

CONCLUSIONS

Hydrotherapy during labor affects neuroendocrine responses that modify psychophysiological processes.

Fetal response to induced maternal emotions

This study investigated the relationship between fetal movements and acute maternal emotional changes during pregnancy. Two empirically validated feature film clips were used for the external generation of two subjectively and facially well-characterized target emotions: happiness and sadness. We simultaneously monitored separate fetal arm, leg, and trunk movements by means of two ultrasound apparatuses while maternal emotions were manipulated by film clip presentation. The number of fetal arm movements, but not the duration, was increased when pregnant women were being shown a happy film. Both the number and the duration of fetal arm movements decreased with the sad film presentation. Neither the presentation of happiness nor the presentation of sadness affected fetal leg or trunk movements. These findings suggest that induced emotions in pregnant women primarily affect arm movements of their fetuses, and that positive and negative emotions have the opposite effects on fetus movement.

Impact of maternal stress, depression and anxiety on fetal neurobehavioral development

Although postnatal psychologic distress has been widely studied for many years, particularly with a focus on postpartum depression, symptoms of maternal depression, stress, and anxiety are not more common or severe after childbirth than during pregnancy. This paper reviews the newer body of research aimed at identifying the effects of women's antenatal psychologic distress on fetal behavior and child development, and the biologic pathways for this influence. These studies are in line with the growing body of literature supporting the "fetal origins hypothesis" that prenatal environmental exposures--including maternal psychologic state-based alterations in in utero physiology--can have sustained effects across the lifespan.

Antenatal maternal anxiety and stress and the neurobehavioural development of the fetus and child: links and possible mechanisms. A review

A direct link between antenatal maternal mood and fetal behaviour, as observed by ultrasound from 27 to 28 weeks of gestation onwards, is well established. Moreover, 14 independent prospective studies have shown a link between antenatal maternal anxiety/stress and cognitive, behavioural, and emotional problems in the child. This link generally persisted after controlling for post-natal maternal mood and other relevant confounders in the pre- and post-natal periods. Although some inconsistencies remain, the results in general support a fetal programming hypothesis. Several gestational ages have been reported to be vulnerable to the long-term effects of antenatal anxiety/stress and different mechanisms are likely to operate at different stages. Possible underlying mechanisms are just starting to be explored. Cortisol appears to cross the placenta and thus may affect the fetus and disturb ongoing developmental processes. The development of the HPA-axis, limbic system, and the prefrontal cortex are likely to be affected by antenatal maternal stress and anxiety. The magnitude of the long-term effects of antenatal maternal anxiety/stress on the child is substantial. Programs to reduce maternal stress in pregnancy are therefore warranted.

Angiotensin II mediates uterine vasoconstriction through alpha-stimulation

Intravenous angiotensin II (ANG II) increases uterine vascular resistance (UVR), whereas uterine intra-arterial infusions do not. Type 2 ANG II (AT(2)) receptors predominate in uterine vascular smooth muscle; this may reflect involvement of systemic type 1 ANG II (AT(1)) receptor-mediated alpha-adrenergic activation. To examine this, we compared systemic pressor and UVR responses to intravenous phenylephrine and ANG II without and with systemic or uterine alpha-receptor blockade and in the absence or presence of AT(1) receptor blockade in pregnant and nonpregnant ewes. Systemic alpha-receptor blockade inhibited phenylephrine-mediated increases in mean arterial pressure (MAP) and UVR, whereas uterine alpha-receptor blockade alone did not alter pressor responses and resulted in proportionate increases in UVR and MAP. Although neither systemic nor uterine alpha-receptor blockade affected ANG II-mediated pressor responses, UVR responses decreased >65% and also were proportionate to increases in MAP. Systemic AT(1) receptor blockade inhibited all responses to intravenous ANG II. In contrast, uterine AT(1) receptor blockade + systemic alpha-receptor blockade resulted in persistent proportionate increases in MAP and UVR. Uterine AT(2) receptor blockade had no effects. We have shown that ANG II-mediated pressor responses reflect activation of systemic vascular AT(1) receptors, whereas increases in UVR reflect AT(1) receptor-mediated release of an alpha-agonist and uterine autoregulatory responses.

Extended somatic support for pregnant women after brain death

OBJECTIVE

To review case reports of pregnant women who have been supported after brain death until successful delivery of their infants. From these reports and other literature about brain death, normal physiologic changes of pregnancy, and specific needs for fetal development, recommendations were made to assist in supporting pregnant women after brain death until delivery of a mature fetus who is likely to survive.

DATA SOURCES

Personal files and experiences, MEDLINE review of case reports and publications about physiologic changes present during normal pregnancy and after brain death, and the critical needs for fetal development were included.

DATA EXTRACTION

Eleven reports of ten patients comprise the accumulated clinical experience. Hypotension, requiring fluid administration and inotropic/vasopressor therapy, occurred in all the mothers, and in six cases, was the reason for urgent delivery. The longest period of support was 107 days, from 15 to 32 wks of gestation. Two mothers also became organ donors. Recurrent infections, thermolability, and other complications common to prolonged ICU care were encountered. All infants survived. One had congenital abnormalities caused by phenytoin use by the mother. When followed, all others developed within normal growth and mental variables. These cases plus literature citations noted above were used to develop recommendations for maternal/fetal care.

CONCLUSION

Preservation of uterine/placental blood flow is the most important priority during somatic support. Imprecise autoregulation of the uterine vasculature during maternal hypoxemia or hypotension makes this goal a significant challenge. Special considerations for nutrition; medication use; cardiovascular, respiratory, or endocrine therapy; fetal monitoring; hormone replacement; and ethical concerns are discussed.

Effect of regular maternal exercise on lipid peroxidation levels and antioxidant enzymatic activities before and after delivery

This study was designed to investigate the influence of maternal aerobic exercise on lipid peroxidation levels and antioxidant enzymatic activities before and after delivery. Predelivery and 1- and 24-hour post partum blood samples were collected from 18 nulliparous healthy pregnant women who exercised regularly throughout the whole period of pregnancy and from 22 matched controls. The plasma concentration of malondialdehyde (MDA) was measured as an indicator of lipid peroxidation. Erythrocyte enzymes, superoxide dismutase (SOD), glutathione peroxidase (GSHPx) and catalase (CAT), were measured as intracellular antioxidant markers. In the control group, MDA increased slightly from predelivery to 1 hour post partum and then increased significantly at 24 hours post partum, with significant increase in SOD and CAT activities. On the other hand, MDA of the exercise group remained unaltered at 1 and 24 hours after delivery. At 1 hour post partum, the SOD and CAT levels of the exercise group increased markedly and then decreased to predelivery levels. The present results indicate that uncontrolled lipid peroxidation occurs during labor and suggest that continuing regular maternal exercise may reduce labor-induced lipid peroxidation by improving the defense capabilities against free radical generation.

Biochemical and functional characterization of alpha-adrenergic receptors in the rabbit vagina

Vascular and non-vascular smooth muscle within the vagina mediate important physiological changes during sexual arousal in women. In this study, we have characterized alpha-adrenergic receptors (AR) in rabbit vagina by assessment of radioligand binding, contractility of isolated tissue strips and genital hemodynamics. [3H]Prazosin and [3H]RX821002 (alpha-1 and alpha-2 AR selective antagonists) bound to rabbit vaginal membrane preparations with high affinity and limited capacity. Competition binding assays using both non-selective and subtype selective ligands for AR (phentolamine, prazosin, delequamine, rauwolscine and UK14304) further confirmed the presence of alpha-1 and alpha-2 AR in vaginal tissue. In organ bath preparations of vaginal tissue strips, norepinephrine-induced contraction was attenuated by alpha-1 and alpha-2 AR antagonists (prazosin, tamsulosin, delequamine and phentolamine). In anesthetized rabbits, intravaginal injection of the alpha-1 AR selective antagonist REC 15/2615 (50 and 100 microg/kg) caused a 2 to 3-fold increase in genital tissue oxyhemoglobin (OHb) concentration. Similar increases in tissue OHb were observed with intravaginal injection of phentolamine (500 microg/kg) or a tri-mixture of vasodilators (PGE1, papaverine, phentolamine). REC 15/2615, phentolamine or the tri-mixture also enhanced the amplitude and/or duration of change in genital tissue OHb after pelvic nerve stimulation. Thus, vaginal tissue expresses functional alpha-1 and alpha-2 AR, which modulate vaginal smooth muscle contractility and genital engorgement.

Mechanisms regulating angiotensin II responsiveness by the uteroplacental circulation

Pregnancy is associated with increases in cardiac output and uterine blood flow (UBF) and a fall in systemic vascular resistance. In ovine pregnancy, UBF rises from approximately 3% of cardiac output to approximately 25% at term gestation, reflecting a >30-fold rise in UBF by term. This increase in UBF supports exponential fetal growth during the last trimester and maintains fetal well-being by providing excess oxygen and nutrient delivery. These hemodynamic changes are associated with numerous hormonal changes, including increases in placental steroid hormones and enhanced activation of the renin-angiotensin and sympathetic nervous systems, all of which are believed to modulate systemic and uterine vascular adaptation and vascular reactivity. Systemic pressor responses to infused ANG II are attenuated in normotensive pregnancies and the uteroplacental vasculature is even less sensitive, suggesting development of mechanisms to maintain basal UBF and permit the rise in UBF necessary for fetal growth and well-being. The effects of ANG II on the uteroplacental vasculature are reviewed, and the mechanisms that may account for attenuated vascular sensitivity are examined, including ANG II metabolism, vascular production of antagonists, ANG II-receptor subtype expression, and the role of indirect mechanisms.

Maternal stress in pregnancy and its effect on the human foetus: an overview of research findings

There is evidence from human studies that anxiety or stress during pregnancy can affect birth outcome, causing babies to be born earlier and possibly smaller for gestational age. There is also some suggestive evidence for longer-term behavioural problems. Animal studies indicate that antenatal stress does have a long-term effect on the behaviour of the offspring, including a hyper-responsive hypothalamo-pituitary -adrenal axis. The human foetus can mount an independent stress response from mid-gestation. Two possible mechanisms have been demonstrated by which maternal stress or anxiety may affect the human foetus, the passage of cortisol across the placenta, and an impairment of blood flow through the maternal uterine arteries.

Hydrotherapy in labor

Maternal anxiety and pain prolong labor and contribute to fetal distress. Hydrotherapy during labor may promote relaxation and decrease pain without the risks caused by other treatments. In this pilot study the psychophysiological effects of hydrotherapy on maternal anxiety and pain during labor were examined. Using a randomized, pretest-posttest control group design with repeated measures, 18 term parturients were assigned to a control or an experimental group. Experimental subjects were placed in a tub of 37 degrees C water for 1 hr during early labor. The Wilcoxon two-sample test revealed statistically significant effects. At 15 min bathers' anxiety and pain scores were decreased compared to nonbathers. At 60 min bathers' pain scores were decreased compared to nonbathers. After 15 min of immersion, bathers had a significantly greater increase in plasma volume than nonbathers. No significant differences were found in urine catecholamines or maternal-fetal complications. The small sample limits conclusions, but the findings offer preliminary support for the therapeutic effects of bathing in labor for acute, short-term anxiety and pain reduction.

Salivary cortisol levels and anxiety are not increased in women destined to develop preeclampsia

OBJECTIVE

To compare salivary cortisol levels and maternal anxiety (general and pregnancy-specific) in the early and late second trimester of pregnancy between women who developed preeclampsia (PE) and women who remained normotensive.

DESIGN

Nested case-referent study. In a prospectively studied cohort of 250 pregnant women, nine women developed PE in late pregnancy. These nine patients were matched and compared with nine controls. Diurnal cortisol levels were obtained by collecting saliva samples at 17-18 and 27-28 weeks gestation. Salivary cortisol levels were determined by radioimmunoassay. Maternal anxiety was determined by Spielberger's State-Trait Anxiety Inventory (STAI) and a pregnancy-specific stress questionnaire.

RESULTS

For both patients and controls, a similar pattern of salivary cortisol excretion was observed. Salivary cortisol levels and anxiety scores (general and pregnancy-specific) did not differ significantly between patients and controls.

CONCLUSIONS

Our findings do not lend support to a role for maternal anxiety or second trimester increases in circulating stress hormones in the pathogenesis of PE.

Changes in maternal lipid peroxidation levels and antioxidant enzymatic activities before and after delivery

OBJECTIVE

Our goal was to characterize the changes in maternal lipid peroxidation levels and antioxidant enzymatic activities before and after delivery.

METHODS

Predelivery and 1, 24, and 48 hours post-partum plasma concentrations of malondialdehyde, erythrocyte enzyme superoxide dismutase, glutathione peroxidase and catalase were measured in uncomplicated pregnancies.

RESULTS

Malondialdehyde levels increased slightly from predelivery to 24 hours post-partum and then decreased significantly at 48 hours post-partum. At one hour post-partum superoxide dismutase and catalase levels increased significantly to about 125% and 170% of predelivery levels, respectively. Thereafter, these values decreased significantly from one hour to 48 hours post-partum. The relative changes in superoxide dismutase and catalase levels at one hour post-partum compared to predelivery values correlated significantly with the duration of labor.

CONCLUSION

The results suggest that the uncontrolled lipid peroxidation caused by reactive oxygen species, which are produced in consequence of tissue reoxygenation, may occur during labor and that prolonged labor, may cause maternal oxidative stress.

Angiotensin II indirectly vasoconstricts the ovine uterine circulation

The uterine vasculature of women and sheep predominantly expresses type 2 ANG II receptors that do not mediate vasoconstriction. Although systemic ANG II infusions increase uterine vascular resistance (UVR), this could reflect indirect mechanisms. Thus we compared systemic and local intra-arterial ANG II infusions in six near-term pregnant and five ovariectomized nonpregnant ewes to determine how ANG II increases UVR. Systemic ANG II dose-dependently (P > 0.001) increased arterial pressure (MAP) and UVR and decreased uterine blood flow (UBF) in pregnant and nonpregnant ewes; however, nonpregnant responses exceeded pregnant (P < 0.001). In contrast, local ANG II infusions at rates designed to achieve concentrations in the uterine circulation comparable to those seen during systemic infusions did not significantly decrease UBF in either group, and changes in MAP and UVR were absent or markedly attenuated. When MAP rose during local ANG II, which only occurred with doses > or =2 ng/ml, increases in MAP were delayed more than twofold compared with responses during systemic ANG II infusions and always preceded decreases in UBF, resembling that observed during systemic ANG II infusions. These observations demonstrate attenuated uterine vascular responses to systemic ANG II during pregnancy and suggest that systemic ANG II may increase UVR through release of another potent vasoconstrictor(s) into the systemic circulation.

Cardiovascular and endocrine alterations after masturbation-induced orgasm in women

OBJECTIVE

The present study investigated the cardiovascular, genital, and endocrine changes in women after masturbation-induced orgasm because the neuroendocrine response to sexual arousal in humans is equivocal.

METHODS

Healthy women (N = 10) completed an experimental session, in which a documentary film was observed for 20 minutes, followed by a pornographic film for 20 minutes, and another documentary for an additional 20 minutes. Subjects also participated in a control session, in which participants watched a documentary film for 60 minutes. After subjects had watched the pornographic film for 10 minutes in the experimental session, they were asked to masturbate until orgasm. Cardiovascular (heart rate and blood pressure) and genital (vaginal pulse amplitude) parameters were monitored continuously throughout testing. Furthermore, blood was drawn continuously for analysis of plasma concentrations of adrenaline, noradrenaline, cortisol, prolactin, luteinizing hormone (LH), beta-endorphin, follicle-stimulating hormone (FSH), testosterone, progesterone, and estradiol.

RESULTS

Orgasm induced elevations in cardiovascular parameters and levels of plasma adrenaline and noradrenaline. Plasma prolactin substantially increased after orgasm, remained elevated over the remainder of the session, and was still raised 60 minutes after sexual arousal. In addition, sexual arousal also produced small increases in plasma LH and testosterone concentrations. In contrast, plasma concentrations of cortisol, FSH, beta-endorphin, progesterone, and estradiol were unaffected by orgasm.

CONCLUSIONS

Sexual arousal and orgasm produce a distinct pattern of neuroendocrine alterations in women, primarily inducing a long-lasting elevation in plasma prolactin concentrations. These results concur with those observed in men, suggesting that prolactin is an endocrine marker of sexual arousal and orgasm.

Association between maternal anxiety in pregnancy and increased uterine artery resistance index: cohort based study

OBJECTIVE

To investigate whether maternal anxiety in the third trimester is associated with an increased uterine artery resistance index.

DESIGN

Cohort based study.

SUBJECTS

100 pregnant women, with a mean gestation of 32 weeks.

OUTCOME MEASURES

Self rating Spielberger questionnaire for state anxiety and trait anxiety, and uterine blood flow waveform patterns as assessed by colour Doppler ultrasound.

RESULTS

A significant association was found between uterine artery resistance index and scores for both Spielberger state anxiety and trait anxiety (rs=0.31, P<0.002 and 0.28 P<0.005 respectively). Women with state anxiety scores >40 (n=15) had a higher mean uterine resistance index than those with scores </= 40 (mean difference with mean resistance index 24%, 95% confidence interval 12% to 38%; P<0.0001). Similarly, women with trait anxiety scores >40 (n=32) had a higher mean resistance index than those with scores </= 40, although to a lesser extent. The presence of notches in the waveform pattern produced by uterine artery blood flow was found in 4/15 (27%) women with high state anxiety scores compared with 4/85 (5%) with low anxiety scores (P<0.02).

CONCLUSIONS

This study shows an association between maternal anxiety in pregnancy and increased uterine artery resistance index. It suggests a mechanism by which the psychological state of the mother may affect fetal development, and may explain epidemiological associations between maternal anxiety and low birth weight. The influence of maternal anxiety may be one mechanism by which the intrauterine environment contributes to later disease in offspring.

Effects of labetalol on uterine blood flow and cardiovascular hemodynamics in the hypertensive gravid baboon

OBJECTIVE

The purpose of this study was to investigate the effects of labetalol on uterine blood flow and cardiovascular parameters in acutely instrumented, hypertensive gravid baboons.

STUDY DESIGN

During the latter half of pregnancy six gravid baboons were acutely instrumented, with ultrasonic flow probes placed on ipsilateral, external iliac, and uterine arteries and a flow-directed pulmonary artery catheter in the pulmonary artery. After a stable arterial pressure baseline was obtained, norepinephrine was infused to increase mean arterial pressure by at least 20%. A 20-minute hypertensive steady state was obtained. Labetalol at 0.5 and 1.0 mg/kg was randomly infused, followed by a 2.0 mg/kg dose, each over 1 minute. A 20-minute recovery period followed every labetalol infusion, allowing the hypertensive steady state to reestablish. External iliac and uterine blood flow measurements were continuously recorded during the baseline and experimental trials. Mean arterial blood pressure, heart rate, pulmonary artery and capillary wedge pressure, central venous pressure, and cardiac output were obtained at 5, 10, and 15 minutes during each steady state and after each labetalol infusion.

RESULTS

Labetalol at all dosages significantly reduced the mean arterial pressure and the systemic vascular resistance at 1.0 and 2.0 mg/kg. External iliac blood flow was not consistently significantly reduced; however, uterine blood flow was significantly reduced after the 1.0 and 2.0 mg/kg labetalol dosages (p < 0.05). Although uterine vascular resistance tended to increase after the 1.0 and 2.0 mg/kg doses, statistical significance was not achieved.

CONCLUSION

Low-dose labetalol (0.5 mg/kg) significantly reduces the pharmacologic hypertensive gravid baboon's mean arterial blood pressure without adversely affecting uterine blood flow.

Responses of placental arteries from normotensive and preeclamptic women to endogenous vasoactive agents

OBJECTIVE

The hypothesis that preeclampsia may be associated with an increase in the response of the placental arteries to vasoconstrictors or a decrease in their response to vasodilators was tested.

STUDY DESIGN

Concentration-response curves to various agents were determined on helical strips of fetal placental arteries from normotensive (n = 33) and preeclamptic (n = 8) women to calculate the potencies and maximal effects of the agents.

RESULTS

Endothelin, prostaglandin F2 alpha, and serotonin caused concentration-dependent contractions; angiotensin II and norepinephrine produced little or no effects. The prostacyclin analog iloprost and atrial natriuretic factor, but not isoproterenol, relaxed placental arteries. Iloprost was more effective on preeclamptic than on normal arteries, but the effects of other agents on the two groups of arteries did not differ. Placental arteries exhibited spontaneous oscillations that were more marked in preeclamptic than in normal arteries and were inhibited by indomethacin.

CONCLUSION

Preeclampsia is not associated with an increase in the responses of fetal placental arteries to vasoconstrictors or a decrease in their response to vasodilators. However, placental arteries from preeclamptic subjects exhibit increased oscillations.

Fetal 'fright-bradycardia' brought on by air-raid alarm in Israel

Three cases of severe fetal bradycardia during labor following an air-raid alarm are described. After 2 min of severe bradycardia (less than 60 beats/min) the fetal heart rate (FHR) returned to a normal pattern. In all cases labor progressed uneventfully with an excellent fetal and maternal outcome. The cases are briefly described and possible causative mechanisms are discussed.

Interaction of myogenic and adrenergic mechanisms in isolated, pressurized uterine radial arteries from late-pregnant and nonpregnant rats

OBJECTIVE

The purpose of this study was to examine how myogenic and adrenergic mechanisms interact in controlling the lumen diameter of small uterine arteries from nonpregnant and late-pregnant rats.

STUDY DESIGN

Radial arteries (150 to 250 microns lumen diameter) from nonpregnant (n = 28) and late-pregnant (n = 18) rats were studied in vitro under conditions of varying transmural pressure and agonist concentrations.

RESULTS

(1) Arteries from late-pregnant rats were significantly (p < 0.05) larger in diameter and, unlike nonpregnant vessels, developed a stable intrinsic tone at transmural pressures > 25 mm Hg. (2) Vessels from late-pregnant rats displayed a threefold increase in sensitivity to the constrictor effects of phenylephrine: 50% of maximal constriction, nonpregnant = 691 +/- 148 nmol/L and late-pregnant = 229 +/- 32 nmol/L (p < 0.01). (3) There was no difference in sensitivity to potassium depolarization. (4) Arteries from late-pregnant rats actively constricted to changes in transmural pressure, whereas those from nonpregnant did not unless preactivated beforehand with phenylephrine or K+. (5) After preconstriction the autoregulatory effectiveness of late-pregnant arteries in physiologic saline solution versus phenylephrine or K+, or of nonpregnant in K+ and phenylephrine, appeared to be equal in terms of absolute micrometers but not relative percent change in lumen diameter.

CONCLUSION

Pregnancy is associated with significant changes in the active contractile properties of uterine resistance artery function, specifically heightened alpha-adrenergic sensitivity, intrinsic (pressure-dependent) tone, and myogenic reactivity.

Low-dose infusion of atrial natriuretic peptide in the conscious guinea pig increases blood flow to the placenta of growth-retarded fetuses

OBJECTIVE

Our goal was to investigate the effects of low-dose infusion of atrial natriuretic peptide on maternal placental blood flow of normal-sized and growth-retarded fetuses.

STUDY DESIGN

Seventeen conscious, chronically catheterized guinea pigs were studied at day 50 of gestation after growth retardation was experimentally induced by unilateral uterine artery ligation at day 34.

RESULTS

In 12 experiments atrial natriuretic peptide infusion (15 ng/kg/min) increased blood flow (microsphere technique) to placentas of growth-retarded fetuses by 26% (p less than 0.01) while placental blood flow of normal-sized fetuses remained unchanged. This difference in responsiveness to atrial natriuretic peptide infusion was statistically significant (p less than 0.001). Blood pressure, heart rate, and myoendometrial and renal blood flows were unaffected. Plasma concentrations of immunoreactive atrial natriuretic peptide increased by 64%, indicating that physiologic concentrations were achieved. In five saline solution-treated controls none of the studied parameters changed.

CONCLUSION

Atrial natriuretic peptide in low doses selectively increases blood flow to placentas of growth-retarded fetuses in the conscious guinea pig. Infusion of atrial natriuretic peptide in a dose that results in plasma concentrations within the upper physiologic range may have a therapeutic value in pregnancies complicated by intrauterine growth retardation.

Cocaine in pregnancy: the effect of maternal administration of cocaine on the maternal and fetal pituitary-adrenal axes

The effects of cocaine on the maternal and fetal pituitary-adrenal axis in vivo during pregnancy have not been reported. Six pregnant ewes and their fetuses underwent instrumentation at 113 to 119 days' gestation. Ewes were assigned to receive an intravenous bolus injection of vehicle or cocaine (0.5, 1.0, or 2.0 mg.kg-1) at 124 to 136 days' gestation. Maternal arterial blood gases, fetal pH and fetal PCO2 were unchanged after injection of cocaine or vehicle. After administration of 2.0 mg.kg-1 cocaine, arterial fetal PO2 fell 3.2 +/- 1.72 mm Hg (p less than 0.05) at +5 minutes, returning to baseline by +15 minutes. Maternal and fetal adrenocorticotropin levels rose within 5 minutes after the highest cocaine dose (p less than 0.05). There was a significant (p less than 0.05) increase in maternal cortisol at all doses of cocaine and in fetal cortisol at +15 minutes after the 2.0 mg.kg-1.

Angiotensin II and alpha-agonist. III. In vitro fetal-maternal placental prostaglandins

In fetal sheep, angiotensin II, but not phenylephrine, increases umbilical venous concentrations of prostaglandin E2 (PGE2) and prostacyclin (PGI2); however, their source(s) is unknown. We sought to determine the tissue source(s) of this increase in prostanoids and to compare responses in fetal and maternal tissues. Fetal placental arteries (PA) and veins (PV), mesenteric arteries (MA) and cotyledons, and maternal caruncles and uterine arteries (UA) from eight pregnant ewes [127 +/- 3 (SE) days] were incubated (37 degrees C, 1 h) in Krebs-Henseleit (95% O2-5% CO2) with or without angiotensin II, phenylephrine, or norepinephrine (5 x 10(-10) and 5 x 10(-8) M). Basal PGE2 production exceeded PGI2 in PA, cotyledons, and caruncles (P less than 0.05), whereas PGE2 less than PGI2 only in UA; production of both prostanoids was greatest in MA with 34.8 +/- 5.0 and 27.4 +/- 3.7 pg.micrograms protein-1.h-1, respectively (P less than 0.001). Caruncles produced little of either prostanoid. Angiotensin II increased PA PGE2 production from 6.5 +/- 1.5 to 8.4 +/- 3.0 and 10.8 +/- 4.5 pg.micrograms-1.h-1 (P = 0.001) and PGI2 from 3.3 +/- 0.5 to 5.5 +/- 1.5 (P less than 0.05) and 3.7 +/- 0.9 pg.micrograms-1.h-1; PV PGE2 rose from 4.5 +/- 1.1 to 9.0 +/- 3.5 and 7.9 +/- 2.3 pg.micrograms-1.h-1 (P less than 0.05); PV PGI2 was unchanged. Angiotensin II increased UA PGE2 from 1.5 +/- 0.3 to 3.4 +/- 1.2 (P less than 0.05) and 2.4 +/- 0.8 pg.micrograms-1.h-1 and PGI2 from 8.7 +/- 1.0 to 12.4 +/- 2.2 and 16.2 +/- 5.2 (P less than 0.05) pg.micrograms-1.h-1. Angiotensin II had no effect on MA, cotyledonary, or caruncular prostanoids. alpha-Agonist had no effect on any tissue examined. In fetal sheep, angiotensin II-induced increases in PGI2 and PGE2 are likely of vascular origin.

Maternal endocrine and fetal metabolic responses to heat stress

Heat-stressed pregnant ewes deliver intrauterine growth-retarded lambs. Selected maternal and fetal changes were investigated during acute heat stress in order to elucidate the mechanism for this growth retardation. Uterine blood flow decreased 20 to 30% in pregnant ewes during 1 degree C increases in core temperature. The decreases were accompanied by 60 and 100% increases in serum oxytocin and antidiuretic hormone, respectively. These effects were mimicked by salt loading or injections of antidiuretic hormone or oxytocin, suggesting a role for either or both hormones in regulating uterine blood flow during pregnancy. Chronically heat-stressed pregnant ewes were delivered by Caesarean section. Their fetuses were approximately 20% smaller than thermoneutral controls. Within each pair of heat-stressed twins, one fetus weighted one-third less than its litter mate. No difference in weights were observed within the control twins. The livers and brains of the heat-stressed fetuses were disproportionate in size. The livers from the small heat-stressed twins contained only one-half the protein of the controls and one-fourth the protein of their litter mates. Muscle protein was decreased in the heat-stressed fetuses, and liver and muscle glycogen were elevated as were liver arginase, glutamate-pyruvate transaminase and muscle creatinine. These results are consistent with the following hypothesis: heat stress stimulates the release of maternal antidiuretic hormone or oxytocin, which reduces uterine blood flow and causes a shift in fetal metabolism from anabolic to catabolic pathways; one fetus of heat-stressed twins is more severely affected than its litter mate.

Prenatal cocaine exposure to the fetus: a sheep model for cardiovascular evaluation

Transplacental passage of cocaine in response to maternal administration of intravenous (IV) cocaine in doses of 1.0 and 2.0 mg/kg was studied in 6 pregnant ewes and fetuses and correlated with maximum changes in maternal and fetal blood pressures (BP), heart rates (HR) and fetal arterial blood gas values. Certain animals were given larger doses (3.0 and 5.0 mg/kg) of cocaine to examine cocaine-related cardiopulmonary and neurologic sequelae. Cocaine was extracted on C-18 sorbent columns and analyzed by gas chromatography. At 1.0 and 2.0 mg/kg, cocaine produced dose-dependent increases in maternal HR and BP which were maximum by 1 minute. The fetal response was characterized by maximum increases in BP and decreases in PO2 by 3 minutes and increases in HR by 15 minutes. Cocaine rapidly appeared in the fetal circulation, was approximately 15% of maternal concentrations by 5 minutes, and was undetectable in both circulations by 60 minutes. At cocaine doses of 3.0 and 5.0 mg/kg significant maternal cardiopulmonary and neurologic complications were encountered including bradyarrhythmias, respiratory distress, seizure and death. These data indicate that cocaine exerts direct drug actions upon maternal cardiovascular and neurologic function. In addition, cocaine affects fetal cardiovascular function directly via transplacental passage and indirectly by fetal hypoxemia from cocaine-induced uterine artery vasoconstriction. (NIDA 04415)

Comparison between measurements of maternal placental blood flow with dynamic placental scintigraphy and radioactive microspheres

Two methods for measurements of maternal placental blood flow were compared, dynamic placental scintigraphy using 113mIndium and the radioactive microsphere distribution technique which was the reference method. These methods were both used before and after the blood flow was altered by a noradrenaline infusion in pregnant monkeys (Macaca fascicularis). The change of the blood flow values obtained by the two methods were compared. A statistically significant correlation between the two methods was found (r = 0.90, p less than 0.01). It is concluded that dynamic placental scintigraphy can be used as a technique for clinical measurements of relative changes of the maternal placental blood flow.

Maternal cigarette smoking: the effects on umbilical and uterine blood flow velocity

Maternal and fetal effects of smoking one cigarette were assessed in 15 healthy women at 36 to 41 weeks' gestation with no obstetric complications. It was found that smoking was associated with increases in maternal heart rate and blood pressure, but there was no significant change in the uterine artery vascular resistance as measured by means of the systolic/diastolic velocity ratio. There also was an increase in the fetal heart rate as well as a highly significant rise in the systolic/diastolic velocity ratio of the umbilical artery. The responses suggest that smoking causes a direct increase in the vascular resistance of the placenta from the fetal side. This resistance may impair oxygen exchange across the placenta and contribute to the increased perinatal morbidity associated with smoking.

Responsiveness to norepinephrine of the vessels supplying the placenta of growth-retarded fetuses

The effects of intravenous norepinephrine infusions on uteroplacental blood flow were studied in seven awake, chronically catheterized guinea pigs at 63 to 64 days' gestation after unilateral uterine artery ligation at days 31 to 37. An initial subpressor dose of norepinephrine (1.54 +/- 0.18 nmol/kg.min) (+/- SEM) was given, followed by a pressor dose (4.57 +/- 0.59 nmol/kg.min) that caused a 14% increase in mean arterial blood pressure. Placental blood flow as measured by the microsphere technique decreased by 24% in 11 placentas with normal-sized fetuses during the subpressor dose and by 46% during the pressor dose. In 11 placentas with growth-retarded fetuses the two norepinephrine doses reduced blood flow by 19% and 43%, respectively. These results indicate that there is no difference in adrenergic responsiveness between the vessels supplying the placenta of a normal-sized fetus and the arteries of the placenta of a growth-retarded guinea pig. It is suggested that an increase in circulating maternal catecholamine levels would affect a growth-retarded fetus more severely than the normal-sized fetus because the growth-retarded fetus even during normal conditions exists at, or even beyond, the border of imminent asphyxia and hypoglycemia.

Systemic and uterine responses to alpha-adrenergic stimulation in pregnant and nonpregnant ewes

Attenuated systemic pressor responses to infused angiotensin II characterize normal human and ovine pregnancy; moreover, uterine vascular refractoriness is greater than that of the systemic vasculature overall. It remains unclear whether this generalized refractoriness also pertains to other vasoconstrictors; therefore we studied simultaneous systemic and uterine responses to alpha-agonists in pregnant (n = 6) and nonpregnant (n = 6) sheep. Mean arterial pressure, heart rate, uterine blood flow, and cardiac output were measured before and during infusions of norepinephrine (0.456 to 45.84 micrograms/min) and phenylephrine (1.29 to 129 micrograms/min). Both alpha-agonists caused dose-dependent increases (p less than 0.01) in mean arterial pressure and systemic vascular resistance and decreases in cardiac output (p less than 0.01) in nonpregnant and pregnant animals; however, nonpregnant pressor responses exceeded pregnant ones. Nonpregnant ewes also had greater decreases in uterine blood flow (p less than 0.05) and increases in uterine vascular resistance (p less than 0.05); furthermore, increases in uterine vascular resistance exceeded those of systemic vascular resistance in both groups (p less than 0.01). Attenuated uterine and systemic responses to alpha-agonists characterize normal ovine pregnancy; however, in contrast to the results with angiotensin II, the uterine vascular bed is substantially more responsive to alpha-agonists than the systemic vasculature overall.

Systemic and uterine responsiveness to angiotensin II and norepinephrine in estrogen-treated nonpregnant sheep

Pregnancy is associated with uterine and systemic vasodilation and reduced vascular reactivity to angiotensin II and perhaps norepinephrine. The uteroplacental vasculature is relatively refractory to angiotensin II but very sensitive to norepinephrine. To investigate the possible role of the high levels of estrogen in pregnancy mediating these hemodynamic changes, we examined systemic and uterine vascular responsiveness to angiotensin II and norepinephrine in eight chronically instrumented nonpregnant sheep treated with 17 beta-estradiol. In these animals, 17 beta-estradiol produced significant systemic and uterine vasodilation without changing arterial pressure; cardiac output increased from 5.3 +/- 0.3 to 6.7 +/- 0.4 L/min, and uterine blood flow increased from 26 +/- 3 to 218 +/- 13 ml/min (mean +/- SE). Treatment with 17 beta-estradiol reduced the increases in systemic vascular resistance produced by angiotensin II and norepinephrine by 25% and 35%, respectively. After 17 beta-estradiol treatment, the uterine vascular responses were compared to the systemic vascular responses; the uterine responses to angiotensin II were only half the systemic responses, whereas the uterine responses to norepinephrine were six times greater than the systemic responses and were associated with decreases in uterine blood flow of 35% to 40%. These hemodynamic features of nonpregnant sheep treated with estrogen are strikingly similar to previous observations in sheep during pregnancy.

Hemodynamic effects of indomethacin in chronically instrumented pregnant sheep

Indomethacin administration has produced decreases in uteroplacental blood flow in several animal studies; therefore, it has been suggested that the maintenance of uterine blood flow is critically dependent on the continued synthesis of vasodilating prostaglandins. However, vasoconstriction following indomethacin administration may be due to mechanisms other than reduced prostaglandin synthesis. We administered indomethacin (2, 5, or 10 mg/kg) intravenously to seven unanesthetized sheep in late pregnancy and determined the time courses of the uteroplacental and systemic hemodynamic responses, comparing these to the concurrent changes in circulating prostaglandins. Indomethacin administration resulted in rapid increases in systemic and uteroplacental vascular resistance (80% to 100%) and mean arterial pressure (approximately 30%) and in decreases in systemic (approximately 30%) and uteroplacental (0% to 30%) blood flows within 5 minutes. Vasoconstriction was transient, however, and after 60 minutes there was no evidence of uterine or systemic vasoconstriction, although systemic and uterine plasma prostaglandin levels remained reduced for 180 minutes. Thus substantial inhibition of prostaglandin synthesis existed without evidence of concurrent systemic or uteroplacental vasoconstriction, suggesting that uterine blood flow is not directly dependent on maintained prostaglandin synthesis in unstressed pregnant sheep. Furthermore, the transient indomethacin-induced vasoconstriction may not be due to inhibition of prostaglandin synthesis.

Interaction of ovarian steroids and periarterial alpha 1-adrenergic receptors in altering uterine blood flow during the estrous cycle of gilts

In vivo exposure to progesterone increases while estrogen decreases in vitro contractility of uterine arteries to nerve stimulation. In addition, uterine blood flow is highly correlated with the estrogen: progesterone ratio in systemic blood throughout the porcine estrous cycle (approximately 21 days). This study was conducted to compare the function of uterine periarterial sympathetic nerves of eight pigs during the follicular phase, the period of highest uterine blood flow and estrogen: progesterone ratio (days 19 to 21), with eight animals during the luteal phase, the period of lowest uterine blood flow and estrogen: progesterone ratio (day 13). The first day of behavioral estrus was designated as day 0. Uterine arteries from each pig were evaluated for (1) in vitro contractility to nerve stimulation, (2) alpha 1-adrenergic receptor binding with use of the specific ligand 3H-WB-4101, and (3) concentrations of norepinephrine with use of a radioenzymatic assay. Uterine arterial contractility to nerve stimulation was greater (p less than 0.01) for pigs in the luteal phase than for those in the follicular phase (216 +/- 36 versus 56 +/- 26 mm Hg). Furthermore, uterine arteries from luteal phase pigs had greater (p less than 0.05) alpha 1-receptor binding (47 +/- 6 versus 35 +/- 5 fmol/mg of protein) than those from follicular phase pigs. Uterine arterial concentrations of norepinephrine were similar for follicular phase and luteal phase pigs. These results suggest that ovarian steroids alter the function of uterine periarterial sympathetic nerves through changes in alpha 1-adrenergic receptor numbers, which may contribute to the marked changes in uterine blood flow observed during the porcine estrous cycle.