Cardiovascular stress response and coronary artery disease: evidence of an adverse postmenopausal effect in women

Objective Ischemia, Subjective Angina, and Psychological Distress in Angina With No Obstructive Coronary Disease

BACKGROUND

Angina with no obstructive coronary disease (ANOCA) and ischemia with no obstructive coronary disease, prevalent yet underrecognized conditions, mostly affect women. Previous studies rarely distinguished between them. We aimed to compare the prevalence of objective ischemia through various examinations in women with ANOCA and assess the impact of objective and subjective ischemia on their mental health.

METHODS AND RESULTS

A total of 84 eligible women with ANOCA and 42 controls underwent mental stress, pharmacological stress, exercise stress, and Holter testing. Objective evidence of myocardial ischemia was assessed by positron emission tomography-computed tomography and ECG, and subjective symptoms were graded using the Canadian Cardiovascular Society scale (CCS). Psychological assessments were conducted using 6 scales. Among 84 women with ANOCA, 37 (44%) received a diagnosis of ischemia with no obstructive coronary disease following mental stress testing, 20 (28.6%) through pharmacological stress testing, 14 (21.2%) via exercise stress testing, and 24 (32.9%) from Holter. Mental stress-induced myocardial ischemia was more prevalent (P<0.05). Among 54 patients with ANOCA who completed all tests, 30% showed no ischemia, and only 1 (1.9%) showed ischemia in all tests. In addition, patients with ANOCA had higher psychological scores than controls (P<0.01). No significant differences was observed in psychological scores between ANOCA with positive and negative ischemia test results (P>0.05). However, ANOCA with milder angina (CCS I) exhibited higher scores across the Hospital Anxiety and Depression Scale, State-Trait Anxiety Inventory, Perceived Stress Scale, and Posttraumatic Stress Disorder Checklist-Civilian Version and a higher prevalence of Type D personality traits (P<0.05).

CONCLUSIONS

In patients with ANOCA, the positive rate of myocardial ischemia exhibits variability among several noninvasive tests. A worsened psychological state is more closely linked to milder angina symptoms than to ischemia performance, highlighting the importance of focusing on symptom management in their psychological care.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT03982901.

Design, methodology and baseline characteristics of the Women's Ischemia Syndrome Evaluation-Coronary Vascular Dysfunction (WISE-CVD)

A significant number of women with signs and symptoms of ischemia with no obstructive coronary artery disease (INOCA) have coronary vascular dysfunction detected by invasive coronary reactivity testing (CRT). However, the noninvasive assessment of coronary vascular dysfunction has been limited.

METHODS

The Women's Ischemia Syndrome Evaluation-Coronary Vascular Dysfunction (WISE-CVD) was a prospective study of women with suspected INOCA aimed to investigate whether (1) cardiac magnetic resonance imaging (CMRI) abnormalities in left ventricular morphology and function and myocardial perfusion predict CRT measured coronary microvascular dysfunction, (2) these persistent CMRI abnormalities at 1-year follow-up predict persistent symptoms of ischemia, and (3) these CMRI abnormalities predict cardiovascular outcomes. By design, a sample size of 375 women undergoing clinically indicated invasive coronary angiography for suspected INOCA was projected to complete baseline CMRI, a priori subgroup of 200 clinically indicated CRTs, and a priori subgroup of 200 repeat 1-year follow-up CMRIs.

RESULTS

A total of 437 women enrolled between 2008 and 2015, 374 completed baseline CMRI, 279 completed CRT, and 214 completed 1-year follow-up CMRI. Mean age was 55± 11 years, 93% had 20%-50% coronary stenosis, and 7% had <20% stenosis by angiography.

CONCLUSIONS

The WISE-CVD study investigates the utility of noninvasive CMRI to predict coronary vascular dysfunction in comparison to invasive CRT, and the prognostic value of CMRI abnormalities for persistent symptoms of ischemia and cardiovascular outcomes in women with INOCA. WISE-CVD will provide new understanding of a noninvasive imaging modality for future clinical trials.

Mental stress peripheral vascular reactivity is elevated in women with coronary vascular dysfunction: Results from the NHLBI-sponsored Cardiac Autonomic Nervous System (CANS) study

BACKGROUND

Women with chest pain, ischemia, and no obstructive coronary artery disease often have coronary vascular dysfunction (CVaD). Peripheral vascular reactivity to mental stress may contribute mechanistic understanding of stress-induced ischemia in women with CVaD.

METHODS

62 women (41 CVaD and 21 controls) underwent mental stress testing (MST) with anger recall, mental arithmetic, and forehead cold pressor (COP) challenge. Emotional arousal was measured (Likert scale). Reactive hyperemia index (RHI) was calculated before and after MST by peripheral arterial tonometry (PAT). Stress PAT ratio (SPR) of pulse amplitude during stress to rest was obtained to measure vasoconstriction. Wilcoxson rank sum test was used for analysis.

RESULTS

Mean age of CVaD and control groups was 58±9 and 55±10years (p=0.73). Baseline RHI correlated with coronary endothelial function (r=0.36, p=0.03) and inversely with RHI change post-MST (r=-0.51, p<0.001). During MST, 10% of controls reported chest pain vs. 41% of CVaD subjects (p=0.01). RHI did not change significantly after MST in either group. CVaD subjects had lower SPR vs. controls during mental arithmetic (0.54 [0.15, 1.46] vs. 0.67 [0.36, 1.8], p=0.039), not evident in the other tasks. Vasoconstriction inversely correlated with anxiety (r=-3.4, p=0.03), frustration (r=-0.37, p=0.02), and feeling challenged (r=-0.37, p=0.02) in CVaD but not controls.

CONCLUSIONS

Mental stress peripheral vascular reactivity is elevated in women with CVaD compared to controls. Elevated vascular reactivity may be one contributor to stress-induced chest pain in CVaD. Interventions that modulate vasoconstrictive responses may be of benefit and should be tested in clinical trials in women with CVaD.

Dehydroepiandrosterone-sulfate is associated with cardiovascular reactivity to stress in women

Cardiovascular stress reactivity is a predictor of atherosclerosis and cardiac events. Dehydroepiandrosterone (DHEA) protects against cardiovascular diseases, but results among previous studies have been inconsistent. We investigated the association between dehydroepiandrosterone-sulfate (DHEA-s) and cardiovascular stress reactivity in Japanese women and men. Among 979 healthy Japanese subjects (641 women and 338 men), serum levels of DHEA-s, systolic blood pressure (SBP) and diastolic blood pressure (DBP), heart rate, heart rate variability, and peripheral blood flow were measured under rest and two types of task. Mean differences in measured variables during tasks and a post-task period were calculated as changes in stress reactivity. Variables of stress reactivity were adjusted for multiple potential confounding factors. In women, DHEA-s levels showed positive associations with changes in SBP and DBP (standardized beta=0.12, p=0.020; 0.17, 0.002, respectively). Stratification by menopausal status and other lifestyle factors (e.g., smoking status, alcohol consumption) were conducted. Significant positive associations remained in pre-menopausal (standardized beta=0.13, p=0.037; 0.18, 0.005), non-smoking (0.12, 0.010; 0.18, <0.001), and non-drinking women (0.14, 0.021; 0.21, 0.001), and women without a medical history (0.15, 0.020; 0.20, 0.001). In men, there was no significant association between DHEA-s levels and changes in stress reactivity. DHEA-s levels were positively associated with high blood-pressure reactivity to stress in women, and being menopausal, smoking, and alcohol consumption modified this association.

Menopausal status in relation to cardiovascular stress reactivity in healthy Japanese participants

OBJECTIVE

To investigate the hypothesis that postmenopausal women demonstrate greater cardiovascular stress reactivity during mental stress tasks than do both premenopausal women and men.

METHODS

The study included 979 Japanese participants (338 men and 641 women [238 postmenopausal]) aged 16 to 82 years. Blood pressure, heart rate, heart rate variability, and peripheral blood flow were measured at rest and during a mirror drawing stress task and a maze task. Differences between measured variables during tasks and at rest were calculated and considered to represent reactivity to stress. Analyses were adjusted for age and other potential confounding factors.

RESULTS

After adjusting for multiple factors, significant group effects were found for systolic blood pressure (SBP), diastolic blood pressure, heart rate, low-frequency (LF), LF/high-frequency, and peripheral blood flow (effect size: partial η = 0.015, 0.011, 0.013, 0.013, 0.008, and 0.009, respectively). Postmenopausal women were more reactive than men to stress for SBP (15.4 ± 0.8 versus 11.7 ± 0.6 mm Hg), diastolic blood pressure (10.4 ± 0.6 versus 8.0 ± 0.5 mm Hg), heart rate (2.7 ± 0.5 versus 0.7 ± 0.4 beats/min), LF (23.0 ± 5.2 versus 3.2 ± 3.8 ms/Hz), and peripheral blood flow (-39.0 ± 3.8 versus -25.9 ± 2.8 Laser Doppler Perfusion Units) and more reactive than premenopausal women (p < .050) for SBP (15.4 ± 0.8 versus. 12.4 ± 0.5 mm Hg) and LF/high-frequency (1.7 ± 0.1 versus 1.3 ± 0.1).

CONCLUSIONS

Postmenopausal Japanese women evidenced greater cardiovascular stress reactivity during mental stress tasks than did Japanese men or premenopausal women. Cardiovascular hyperreactivity could play a role in the higher risks of cardiovascular diseases in postmenopausal women.

Sex differences in mental stress-induced myocardial ischemia in young survivors of an acute myocardial infarction

OBJECTIVES

Emotional stress may disproportionally affect young women with ischemic heart disease. We sought to examine whether mental stress-induced myocardial ischemia (MSIMI), but not exercise-induced ischemia, is more common in young women with previous myocardial infarction (MI) than in men.

METHODS

We studied 98 post-MI patients (49 women and 49 men) aged 38 to 60 years. Women and men were matched for age, MI type, and months since MI. Patients underwent technetium-99m sestamibi perfusion imaging at rest, after mental stress, and after exercise/pharmacological stress. Perfusion defect scores were obtained with observer-independent software. A summed difference score (SDS), the difference between stress and rest scores, was used to quantify ischemia under both stress conditions.

RESULTS

Women 50 years or younger, but not older women, showed a more adverse psychosocial profile than did age-matched men but did not differ for conventional risk factors and tended to have less angiographic coronary artery disease. Compared with age-matched men, women 50 years or younger exhibited a higher SDS with mental stress (3.1 versus 1.5, p = .029) and had twice the rate of MSIMI (SDS ≥ 3; 52% versus 25%), whereas ischemia with physical stress did not differ (36% versus 25%). In older patients, there were no sex differences in MSIMI. The higher prevalence of MSIMI in young women persisted when adjusting for sociodemographic and life-style factors, coronary artery disease severity, and depression.

CONCLUSIONS

MSIMI post-MI is more common in women 50 years or younger compared with age-matched men. These sex differences are not observed in post-MI patients who are older than 50 years.

Stress reactivity in patients with workplace hypertension

Aim. To investigate the specific features of stress reactivity and diagnostic potential of psycho-emotional tests for identification of the patients with workplace arterial hypertension (WPAH). Material ad methods. The study included 197 patients with WPAH and 132 subjects with essential AH (EAH). All participants underwent blood pressure monitoring (BPM) during work and leisure hours and stress reactivity assessment (count test). Results. In WPAH and EAH patients, the count test resulted in increased systolic (SBP), diastolic (DBP) BP, and heart rate (HR) (р<0,001), which was an evidence of stress-related functional cardiovascular reaction. In subjects with new-onset WPAH, compared to EAH patients, the SBP and HR increases were greater by 7,9 mm Hg (р<0,005) and 4,3 bpm (р<0,001), respectively. In patients with long-term EAH, SBP increase was greater by 3,4 mm Hg (p=0,03), with a halved HR increase (p<0,001). In healthy controls and AH patients, the differences between baseline levels of SBP and DBP, peak levels during the count test, and BMP levels for work hours were comparable. Conclusion. The patients at early WPAH stages were characterized by increased cardiovascular reaction to acute induced psycho-emotional stress. At the later WPAH stages, BP reactivity was reduced. The cont test could be used as a screening tool in patients with undiagnosed WPAH.

Hormones, heart disease, and health: individualized medicine versus throwing the baby out with the bathwater

It is increasingly axiomatic that depression has widespread adverse physiological effects and, conversely, that a variety of physiological systems impact the risk for developing depression. This convergence of depression and altered physiology is particularly dramatic during midlife--a time during which reproductive failure presages dramatic increases in prevalence of both heart disease and depression. The potentially meaningful and illuminating links between estrogen deficiency, cardiovascular disease (CVD), and depression have largely been obscured, first by assertions, subsequently repudiated, that the perimenopause was not a time of increased risk of depression, and more recently by the denegration of hormone replacement therapy by initial reports of the Women's Health Initiative. Increasingly, however, research has led to unavoidable conclusions that CVD and depression share common, mediating pathogenic processes and that these same processes are dramatically altered by the presence or absence of estrogen (E2). This review summarizes data supporting these contentions with the intent of placing depression and estrogen therapy in their proper physiologic context.

Hormones, heart disease, and health: individualized medicine versus throwing the baby out with the bathwater

It is increasingly axiomatic that depression has widespread adverse physiological effects, and conversely that a variety of physiological systems impact the risk for developing depression. This convergence of depression and altered physiology is particularly dramatic during midlife-a time during which reproductive failure presages dramatic increases in prevalence of both heart disease and depression. The potentially meaningful and illuminating links between estrogen (E2) deficiency, cardiovascular disease (CVD), and depression have largely been obscured, first by assertions, subsequently repudiated that the perimenopause was not a time of increased risk of depression, and more recently by the denegration of hormone replacement therapy by initial reports of the Women's Health Initiative. Increasingly, however, research has led to unavoidable conclusions that CVD and depression share common and mediating pathogenic processes and that these same processes are dramatically altered by the presence or absence of E2. This review summarizes data supporting this contention with the intent of placing depression and E2 therapy in their proper physiologic context.

Effects of estrogen plus progesterone on hemodynamic and vascular reactivity in hypertensive postmenopausal women

AIMS

To investigate the medium-term effects of estrogen plus progesterone therapy (EPT) on vascular reactivity, endothelial function and hemodynamic responses in 20 hypertensive postmenopausal women.

METHODS

This randomized, double-blind, cross-over, placebo-controlled study investigates the effect of 6 months of EPT (conjugated equine estrogen plus medroxyprogesterone). Blood pressure (office and ambulatory), heart rate and heart rate variability (HRV) were measured at baseline and following EPT/placebo treatment. In eight women, we used a wire-myograph to assess endothelial function and contractile response of subcutaneous arteries to transmural nerve stimulation (TNS) and exogenous noradrenaline.

RESULTS

EPT decreased vascular reactivity to cumulative TNS compared with baseline (p<0.01) and placebo (p<0.05). Moreover, EPT diminished sensitivity to exogenous noradrenaline (p<0.05). Although EPT reinforced response to acetylcholine, we observed no difference in maximal relaxation induced by substance P or acetylcholine. EPT did not affect ambulatory blood pressure, heart rate or HRV.

CONCLUSIONS

Oral combined medium-term EPT reduces adrenergic reactivity in subcutaneous arteries from treated hypertensive postmenopausal women. EPT might act postjunctionally at the adrenergic vascular receptor level. In the present study, EPT neither reduces sympathetic activity nor increases vagal tone, and thus does not support an effect on the central hemodynamic system.

Naloxone does not influence cardiovascular responses to mild mental stress in postmenopausal women

The interaction between central opioid activity, sex hormones, and the cardiovascular reactivity to stress is unknown. Twenty-eight healthy postmenopausal women, 16 without, and 12 with hormone replacement therapy (HRT) participated in this randomized, double-blind, cross-over study. The opioid receptor antagonist naloxone or placebo was administered intravenously on 2 different days and mild mental stress was induced by the Stroop Color-Word Test. Cardiovascular responses were assessed noninvasively by impedance cardiography. Stress significantly increased stroke volume, cardiac output, blood pressure, and heart rate, which was not influenced by opioid receptor blockade. Whereas naloxone increased cortisol plasma concentrations irrespective of HRT status, luteinizing hormone concentrations, which were higher in non-HRT compared with HRT women, were increased by naloxone in women with HRT only. These data suggest that the opioidergic tone of the hypothalamus-pituitary-adrenal axis persists in postmenopausal women, irrespective of HRT use, while the opioidergic tone on the hypothalamus-pituitary-gonadal axis seems to depend on an estrogenic milieu. Naloxone does not alter cardiovascular mental stress reactions in postmenopausal women independent of their hormone substitution status.

A greater reduction in high-frequency heart rate variability to a psychological stressor is associated with subclinical coronary and aortic calcification in postmenopausal women

OBJECTIVE

Reduced cardiac parasympathetic activity, as indicated by a reduced level of clinic or ambulatory high-frequency heart rate variability (HF-HRV), is associated with an increased risk for atherosclerosis and coronary artery disease. We tested whether the reduction in HF-HRV to a psychological stressor relative to a baseline level is also associated with subclinical coronary or aortic atherosclerosis, as assessed by calcification in these vascular regions.

METHOD

Spectral estimates of 0.15 to 0.40 Hz HF-HRV were obtained from 94 postmenopausal women (61-69 years) who engaged in a 3-minute speech-preparation stressor after a 6-minute resting baseline. A median of 282 days later, electron beam tomography (EBT) was used to measure the extent of coronary and aortic calcification.

RESULTS

In univariate analyses, a greater reduction in HF-HRV from baseline to speech preparation was associated with having more extensive calcification in the coronary arteries (rho = -0.29, p = .03) and in the aorta (rho = -0.22, p = .06). In multivariate analyses that controlled for age, education level, smoking status, hormone therapy use, fasting glucose, high-density lipoproteins, baseline HF-HRV, and the stressor-induced change in respiration rate, a greater stressor-induced reduction in HF-HRV was associated with more calcification in the coronary arteries (B = -1.21, p < .05), and it was marginally associated with more calcification in the aorta (B = -0.92, p = .09).

CONCLUSION

In postmenopausal women, a greater reduction in cardiac parasympathetic activity to a psychological stressor from baseline may be an independent correlate of subclinical atherosclerosis, particularly in the coronary arteries.

Lowering cortisol and CVD risk in postmenopausal women: a pilot study using the Transcendental Meditation program

Unlike younger women, the risk of cardiovascular disease in older women matches or exceeds that of men. Excessive cortisol may play a role in this increased risk. Here we explore the possibility that the Transcendental Meditation (TM) program may reduce the cortisol response to a metabolic stressor as a way of reducing disease risk in older women. Data from 16 women who were long-term practitioners of transcendental meditation (mean = 23 y) were compared with data from 14 control women matched for age (mean = 75 y, range = 65-92 y). Data on demographics, disease symptoms, and psychological variables were collected, and cortisol response to a metabolic stressor (75 g of glucose, orally) was examined in saliva and urine. Pre-glucose levels of salivary cortisol were identical for the two groups. Post-glucose cortisol rose faster in the controls and was significantly higher than that in the TM women (P < 1 3 10(-4)). Urinary excretion of cortisol during this period was 3 times higher in controls than in the TM women (2.4 +/- 0.17 and 0.83 +/- 0.10 microg/h, respectively; P = 2 x 10(-4)). In addition, the number of months practicing transcendental meditation was inversely correlated with CVD risk factors. Lower cortisol response to metabolic challenge may reflect improved endocrine regulation relevant to the disease-preventing effects of transcendental meditation in older women.

Exaggerated platelet and hemodynamic reactivity to mental stress in men with coronary artery disease

OBJECTIVE

This study compared the effects of acute mental stress on cardiovascular and subjective responses and platelet activation in male patients with established coronary artery disease (CAD) and age-matched controls.

METHODS

We assessed 17 male CAD patients aged 44 to 59 years and 22 healthy male controls. Blood pressure, heart rate, and hemodynamics were assessed before, during, and up to 2 hours after administration of color/word and mirror tracing tasks. Blood was sampled at baseline, after tasks, and at 30 and 75 minutes after stress, and platelet activation was assessed by measuring platelet-leukocyte aggregates (PLAs) using flow cytometry.

RESULTS

CAD patients showed significantly greater systolic blood pressure stress responses than controls (mean increases of 43.9 and 28.3 mm Hg, adjusted for income, body mass index, waist/hip ratio, and medication), together with larger increases in heart rate (14.1 and 4.7 bpm) and cardiac index. Total peripheral resistance increased during the poststress recovery period in CAD patients but not in controls. PLAs increased with stress in both groups, but remained elevated at 75 minutes in CAD patients, returning to baseline in controls. Heart rate and cardiac index responses were correlated with increases in subjective stress and with depression ratings, whereas PLA responses were associated with ratings of task difficulty.

CONCLUSION

Acute mental stress stimulated heightened cardiovascular responses in CAD patients, coupled with more prolonged platelet activation. These factors may contribute to plaque rupture and thrombogenesis, and partly mediate stress-induced triggering of acute coronary syndromes.

Blood pressure and pulse responses to three stressors: associations with sociodemographic characteristics and cardiovascular risk factors

Cardiovascular reactivity is hypothesized to increase the risk of hypertension and other CVD-related conditions. However, studies to date are inconclusive. We compared the association of blood pressure and pulse responses to three stressors (postural challenge, handgrip test, mental arithmetic) with sociodemographic characteristics and CVD risk factors. We included 782 participants from the Hypertension Genetic Epidemiology Study. Blood pressure and pulse responses to stressors were defined as the difference between post- and pre-stress measurements. Stepwise regression analyses examined change in SBP and pulse in response to stressors as a function of sociodemographic and CVD risk factors. Age, race, and gender were forced into models and other variables (education, BMI, waist circumference, resting SBP and DBP, cigarette smoking, LDL and HDL cholesterol, glucose, and antihypertensive medications (beta-blockers, calcium channel blockers, diuretics, ace inhibitors)) were retained if P<0.10. Age was a significant predictor of SBP response to all stressors. The SBP response to a change in posture was not related to other variables. The SBP response to mental arithmetic was significantly higher among men, those with larger waists, higher SBP, beta-blocker users, and lower among smokers. SBP response to the handgrip was significantly higher among those with higher SBP and beta-blocker users. Similarly, the association of the pulse response to the risk factors varied considerably across the stressors. Overall, the socio-demographic and CVD risk factors accounted for between 9 and 14% of the variance in the SBP response to the stressors and from between 4 and 12% of the variance in the pulse response to the three stressors. The associations between sociodemographic and CVD risk factors and the SBP and pulse response to stress were modest and inconsistent across stressors. The findings suggest that cardiovascular reactivity is a concept that needs to be defined in reference to specific stressors so that mechanisms leading to responses can be better understood.

Effects of hormone replacement therapy on the sympathetic nervous system and blood pressure

Hypertension is a major health problem that significantly contributes to heart disease and stroke. While most studies of hypertension have focused on men, women also experience significant hypertension-related morbidity and mortality. However, the incidence of hypertension and cardiovascular disease is significantly lower in premenopausal women compared with men until the onset of menopause, at which time cardiovascular disease incidence increases dramatically in women and eventually approaches that in men. These observations indicate that the loss of estrogen contributes to menopause-related increases in blood pressure and cardiovascular disease, and suggest that the use of estrogen hormone replacement therapy could decrease the incidence of cardiovascular disease in postmenopausal women. However, new findings from the Women's Health Initiative study suggest that estrogen therapy has few positive benefits and some significant negative effects on the health of postmenopausal women, and these data have caused many to abandon long-term estrogen replacement therapy. Conversely, numerous clinical and basic research studies indicate that estrogen replacement therapy beneficially reduces blood pressure, thereby decreasing the incidence of hypertension and cardiovascular disease. Further, several of these studies suggest that one means by which estrogen lowers blood pressure is by decreasing sympathetic nervous system activity. This review examines the evidence supporting estrogen's ability to modulate sympathetic nervous system tone and thereby decrease arterial pressure.

Estrogen depletion induces NaCl-sensitive hypertension in female spontaneously hypertensive rats

In women, arterial pressure generally increases after menopause, but several studies suggest that women who eat large amounts of plant estrogens (phytoestrogens) experience a slower rise in the incidence of postmenopausal hypertension. This suggests that both ovarian hormones (principally estrogen) and phytoestrogens may protect at least some women from hypertension. The present study tests the hypothesis that phytoestrogens blunt hypertension in estrogen-depleted female spontaneously hypertensive rats (SHR). Three-week-old ovariectomized SHR were fed one of four diets that contained basal (0.6%) or high (8%) NaCl with or without dietary phytoestrogens for 9 wk. In SHR on the basal NaCl diet, arterial pressure was unaffected by the removal of dietary phytoestrogens. In contrast, in SHR on the high-NaCl diet, arterial pressure was significantly higher in rats on the phytoestrogen-free (204 +/- 4 mmHg) compared with the phytoestrogen-replete (153 +/- 4 mmHg) diet. Ganglionic blockade resulted in reductions in arterial pressure that were directly related to the dietary NaCl-induced increases in arterial pressure. Together, these data indicate that dietary phytoestrogens protect ovariectomized female SHR from dietary NaCl-sensitive hypertension and that the sympathetic nervous system plays an important role in this effect. Furthermore, these results demonstrate that dietary phytoestrogens can have a major impact on the interpretation of studies into the physiological role of estrogen in females.

The role of the nervous system in hypertension

The central nervous system plays an important role in the minute-to-minute regulation of arterial pressure, but its contribution to chronic regulation of arterial pressure is less clear. A nervous system role in essential hypertension in humans has been postulated for decades, but conclusive data on the relationship has been lacking. However, several lines of evidence in animal models and in humans suggest that the sympathetic nervous system is a primary contributor to the development and maintenance of some forms of essential hypertension. The primary final common pathway for the nervous system's contribution to hypertension is the sympathetic nervous system. Sympathetic nervous system overactivity may result from either inappropriately elevated sympathetic drive from brain centers, an increase in synaptically released neurotransmitters in the periphery, or amplification of the neurotransmitter signal at the target tissue. This review examines recent evidence for the central and peripheral nervous systems' roles in hypertension, and considers recent findings in this area that suggest that sex steroids and circadian rhythms are important considerations in the nervous system's regulation of arterial pressure.

Cardiovascular responses to open-field stress in rats: sex differences and effects of gonadal hormones

We studied sex differences in cardiovascular responses to stress using a new radio-telemetry model in which freely-moving Spontaneously Hypertensive rats (SHR) are exposed to open-field novelty stress. This model allowed simultaneous assessment of cardiovascular and behavioural responses to psychological stress. Female SHR in the diestrous stage of their estrous cycle had markedly greater pressor and tachycardic responses to open-field exposure when compared to either female rats not in diestrous or male SHR. Treatment of ovariectomized SHR with estrogen alone had no significant effect on cardiovascular reactivity, while a combined treatment of estrogen and progesterone slightly, but significantly attenuated their pressor response to open-field stress. In addition, treatment of castrated male rats with testosterone significantly enhanced their pressor responses to stress when compared to values obtained before treatment. None of the hormone treatments had any significant effect on heart rate responses to stress. Neither at different stages of the estrous cycle nor after hormone treatments were there any marked changes in behavioural responses in the open-field, making it unlikely that the differences in cardiovascular stress responses were caused by changes in behavioural activity. These data demonstrate differences in cardiovascular stress responses that seem to be dependent on the stage of the estrous cycle. They suggest that particularly androgens, such as testosterone, may enhance pressor responses to stress. On the other hand, a combination of estrogen and progesterone, rather than estrogen alone, may have a small attenuating effect on cardiovascular reactivity.