The microbiota-gut-brain axis and perceived stress in the perinatal period.

Perinatal perceived stress can contribute to worse health outcomes for the parent-child dyad. Given the emerging relationship between the microbiota-gut-brain axis and stress, this study sought to elucidate connections between bowel symptoms and the gut microbiome in relation to perceived stress at three time points in the perinatal period: two during pregnancy and one postpartum. Ninety-five pregnant individuals participated in a prospective cohort study from April 2017 to November 2019. Researchers assessed Perceived Stress Scale-10 (PSS); bowel symptoms (according to the IBS Questionnaire); psychiatrist assessment of new onset or exacerbated depression and anxiety; and fecal samples analyzed for alpha diversity (measures of gut microbiome diversity utilizing Shannon, Observed OTUs, and Faith's PD) at each timepoint. Covariates included weeks of gestation and weeks postpartum. PSS scores were divided into "Perceived Self-Efficacy" and "Perceived Helplessness." Increased gut microbial diversity was associated with decreased bowel symptoms, decreased overall perceived stress, increased ability to cope with adversity, and decreased distress in the postpartum period. This study found a significant association between a less diverse microbial community, lower self-efficacy early in pregnancy, and greater bowel symptoms and perceived helplessness later in the perinatal period, relationships that may ultimately point to novel diagnostic methods and interventions for perceived stress based on the microbiota-gut-brain axis.

Adolescents' Hormonal Responses to Social Stress and Associations with Adolescent Social Anxiety and Maternal Comfort: A Preliminary Study.

Both social support and social stress can impact adolescent physiology including hormonal responses during the sensitive transition to adolescence. Social support from parents continues to play an important role in socioemotional development during adolescence. Sources of social support and stress may be particularly impactful for adolescents with social anxiety symptoms. The goal of the current study was to examine whether adolescent social anxiety symptoms and maternal comfort moderated adolescents' hormonal response to social stress and support. We evaluated 47 emotionally healthy 11- to 14-year-old adolescents' cortisol and oxytocin reactivity to social stress and support using a modified version of the Trier Social Stress Test for Adolescents that included a maternal comfort paradigm. Findings demonstrated that adolescents showed significant increases in cortisol and significant decreases in oxytocin following the social stress task. Subsequently, we found that adolescents showed significant decreases in cortisol and increases in oxytocin following the maternal comfort paradigm. Adolescents with greater social anxiety symptoms showed higher levels of cortisol at baseline but greater declines in cortisol response following maternal social support. Social anxiety symptoms were unrelated to oxytocin response to social stress or support. Our findings provide further evidence that mothers play a key role in adolescent regulation of physiological response, particularly if the stressor is consistent with adolescents' anxiety. More specifically, our findings suggest that adolescents with higher social anxiety symptoms show greater sensitivity to maternal social support following social stressors. Encouraging parents to continue to serve as a supportive presence during adolescent distress may be helpful for promoting stress recovery during the vulnerable transition to adolescence.

Oxytocin, cortisol, and cognitive control during acute and naturalistic stress.

Although stress is a strong risk factor for poor health, especially for women, it remains unclear how stress affects the key neurohormones cortisol and oxytocin, which influence stress-related risk and resilience. Whereas cortisol mediates energy mobilization during stress, oxytocin has anti-inflammatory, anxiolytic, and analgesic effects that support social connection and survival across the lifespan. However, how these neurohormones interrelate and are associated with cognitive control of emotional information during stress remains unclear. To address these issues, we recruited 37 college-aged women (Mage = 19.19, SD = 1.58) and randomly assigned each to a one-hour experimental session consisting of either an acute stress (emotionally stressful video) or control (non-stressful video) condition in a cross-sectional manner across the semester. Salivary cortisol and oxytocin samples were collected at baseline and after the video, at which point participants also completed measures assessing affect and an emotional Stroop task. As hypothesized, the emotional stressor induced negative emotions that were associated with significant elevations in cortisol and faster Stroop reaction times. Moreover, higher baseline oxytocin predicted greater positive affect after the stressor and also better cognitive accuracy on the Stroop. Analyses examining the naturalistic stress effects revealed that basal oxytocin levels rose steeply three weeks before the semester's end, followed by rising cortisol levels one week later, with both neurohormones remaining elevated through the very stressful final exam period. Considered together, these data suggest that women's collective experiences of stress may be potentially buffered by a synchronous oxytocin surge that enhances cognitive accuracy and reduces stress "when the going gets tough".

Placebo Effects in the Neuroendocrine System: Conditioning of the Oxytocin Responses.

OBJECTIVE: There is evidence that placebo effects may influence hormone secretion. However, few studies have examined placebo effects in the endocrine system, including oxytocin placebo effects. We studied whether it is possible to trigger oxytocin placebo effects using a classical conditioning paradigm. METHODS: Ninety-nine women were assigned to a conditioned, control, or drug control group. In the two-phase conditioning paradigm, participants in the conditioned and drug control groups received an oxytocin nasal spray combined with a distinctive smell (conditioned stimulus [CS]) for three acquisition days, whereas the control group received placebo spray. Subsequently, the conditioned and control groups received placebo spray with the CS and the drug control group received oxytocin spray for three evocation days. Salivary oxytocin was measured several times during each day. Pain sensitivity and facial evaluation tests previously used in oxytocin research were also administered. RESULTS: On evocation day 1, in the conditioned group, oxytocin significantly increased from baseline to 5 minutes after CS (B[slope] = 19.55, SE = 5.88, p < .001) and remained increased from 5 to 20 (B = -10.42, SE = 5.81, p = .071) and 50 minutes (B = -0.70, SE = 3.37, p = .84). On evocation day 2, a trend for increase in oxytocin was found at 5 minutes (B = 15.22, SE = 8.14, p = .062). No placebo effect was found on evocation day 3 (B = 3.57, SE = 3.26, p = .28). Neither exogenous nor conditioned oxytocin affected pain or facial tasks. CONCLUSIONS: Results indicate that oxytocin release can be conditioned and that this response extinguishes over time. Triggering hormonal release by placebo manipulation offers various clinical possibilities, such as enhancing effects of pharmacological treatments or reducing dosages of medications. TRIAL REGISTRATION: The study was registered as a clinical trial on www.trialregister.nl (number NTR5596).

Prenatal drug exposure affects neonatal brain functional connectivity.

Prenatal drug exposure, particularly prenatal cocaine exposure (PCE), incurs great public and scientific interest because of its associated neurodevelopmental consequences. However, the neural underpinnings of PCE remain essentially uncharted, and existing studies in school-aged children and adolescents are confounded greatly by postnatal environmental factors. In this study, leveraging a large neonate sample (N = 152) and non-invasive resting-state functional magnetic resonance imaging, we compared human infants with PCE comorbid with other drugs (such as nicotine, alcohol, marijuana, and antidepressant) with infants with similar non-cocaine poly drug exposure and drug-free controls. We aimed to characterize the neural correlates of PCE based on functional connectivity measurements of the amygdala and insula at the earliest stage of development. Our results revealed common drug exposure-related connectivity disruptions within the amygdala-frontal, insula-frontal, and insula-sensorimotor circuits. Moreover, a cocaine-specific effect was detected within a subregion of the amygdala-frontal network. This pathway is thought to play an important role in arousal regulation, which has been shown to be irregular in PCE infants and adolescents. These novel results provide the earliest human-based functional delineations of the neural-developmental consequences of prenatal drug exposure and thus open a new window for the advancement of effective strategies aimed at early risk identification and intervention.

A functional genomic perspective on human well-being.

To identify molecular mechanisms underlying the prospective health advantages associated with psychological well-being, we analyzed leukocyte basal gene expression profiles in 80 healthy adults who were assessed for hedonic and eudaimonic well-being, as well as potentially confounded negative psychological and behavioral factors. Hedonic and eudaimonic well-being showed similar affective correlates but highly divergent transcriptome profiles. Peripheral blood mononuclear cells from people with high levels of hedonic well-being showed up-regulated expression of a stress-related conserved transcriptional response to adversity (CTRA) involving increased expression of proinflammatory genes and decreased expression of genes involved in antibody synthesis and type I IFN response. In contrast, high levels of eudaimonic well-being were associated with CTRA down-regulation. Promoter-based bioinformatics implicated distinct patterns of transcription factor activity in structuring the observed differences in gene expression associated with eudaimonic well-being (reduced NF-κB and AP-1 signaling and increased IRF and STAT signaling). Transcript origin analysis identified monocytes, plasmacytoid dendritic cells, and B lymphocytes as primary cellular mediators of these dynamics. The finding that hedonic and eudaimonic well-being engage distinct gene regulatory programs despite their similar effects on total well-being and depressive symptoms implies that the human genome may be more sensitive to qualitative variations in well-being than are our conscious affective experiences.

The impact of oxytocin administration and maternal love withdrawal on event-related potential (ERP) responses to emotional faces with performance feedback.

This is the first experimental study on the effect of oxytocin administration on the neural processing of facial stimuli conducted with female participants that uses event-related potentials (ERPs). Using a double-blind, placebo-controlled within-subjects design, we studied the effects of 16 IU of intranasal oxytocin on ERPs to pictures combining performance feedback with emotional facial expressions in 48 female undergraduate students. Participants also reported on the amount of love withdrawal they experienced from their mothers. Vertex positive potential (VPP) and late positive potential (LPP) amplitudes were more positive after oxytocin compared to placebo administration. This suggests that oxytocin increased attention to the feedback stimuli (LPP) and enhanced the processing of emotional faces (VPP). Oxytocin heightened processing of the happy and disgusted faces primarily for those reporting less love withdrawal. Significant associations with LPP amplitude suggest that more maternal love withdrawal relates to the allocation of attention toward the motivationally relevant combination of negative feedback with a disgusted face.

Salivary levels of oxytocin remain elevated for more than two hours after intranasal oxytocin administration.

OBJECTIVE: This is the first study investigating whether levels of oxytocin in saliva remained elevated after intranasal oxytocin administration for the duration of an experiment (in which neurobehavioral effects of oxytocin were observed) taking more than two hours. METHODS: Oxytocin levels were measured in saliva samples collected from 57 female participants right before (T0), approximately 1» h (T1), and approximately 2» h (T2) after intranasal administration of 16 IU of oxytocin or a placebo, using a double-blind, within-subjects design. RESULTS: Average levels of oxytocin did not differ between conditions before use of the nasal spray, markedly increased only after oxytocin administration, and were still elevated after 2» h. CONCLUSION: Salivary levels of oxytocin remained persistently elevated over the course of our experiment, i.e. for more than two hours after intranasal oxytocin administration and over a time-period in which neurobehavioral effects of oxytocin are commonly observed. This suggests that salivary concentrations may be a valuable biomarker for oxytocin, and may help to explain its effects on brain activity, information processing, and behavior.

Perinatal Depression, Adverse Life Events, and Hypothalamic-Adrenal-Pituitary Axis Response to Cold Pressor Stress in Latinas: An Exploratory Study.

BACKGROUND: Latinas are disproportionately affected by perinatal depression (PND) as well as by adverse life events (ALEs), an independent predictor of PND. Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis has been seen both in women with PND and with a history of ALEs in non-Latinas. Although some evidence suggests that HPA axis dysregulation may mediate the link between ALEs and PND, this hypothesis has received little attention and there are no studies that have examined these pathways in Latinas. The primary aim of the present study was to explore, in a Latina sample, associations between ALEs, PND, and HPA axis stress reactivity to a physical stressor, the cold pressor test (CPT). The secondary aim was to explore whether HPA axis reactivity and PND were associated with pain sensitivity to the CPT. METHODS: Thirty-four Latinas were enrolled in their third trimester of pregnancy and interviewed at 4 and 8 weeks postpartum. Depression status was determined using the Edinburgh Postnatal Depression Scale (≥10). At 8 weeks postpartum, 27 women underwent laboratory-induced pain testing using the CPT. Plasma adrenocorticotropic hormone and cortisol were sampled before and after the CPT to generate a stress reactivity score (post-pre). Pain sensitivity and ALEs were also assessed. RESULTS: At enrollment, 26% of women were depressed, and 18% were depressed at 8 weeks postpartum. Fifty-two percent reported at least one childhood ALE. There was a significant and positive association between any childhood ALE and prenatal depression scores (p = .025). Infant-related ALEs were significantly associated with greater adrenocorticotropic hormone reactivity to the CPT (p = .030). Women with a history of any childhood ALE exhibited a blunted cortisol response to the CPT (p = .045). Women with a history of PND at 4 weeks had greater adrenocorticotropic hormone stress reactivity to the CPT (p = .027). No effects of PND were seen for pain sensitivity measures in response to the CPT, although there was a positive and significant correlation between pain tolerance and cortisol response to the CPT in the whole sample. CONCLUSIONS: Given the associations between ALEs and PND and their individual effect on HPA axis stress reactivity, future studies on PND should include a larger sample of Latinas to test the mediating effects of HPA axis reactivity on associations between ALEs and PND.

Influences of oxytocin and respiratory sinus arrhythmia on emotions and social behavior in daily life.

The literature concerning biological influences on positive social behavior shows that, in nonthreatening contexts, tonic oxytocin (OT) and respiratory sinus arrhythmia (RSA) each predict positive, affiliative behaviors toward certain others and are associated with positive health outcomes. The purpose of this investigation was to determine the degree to which the positive affiliative correlates of OT and RSA can be distinguished when observed at the level of everyday life events. A sample of midlife adults (N = 73) provided tonic indices of these biological characteristics, as well as perceptions of a variety of common life events alongside reports of their emotions during those events. OT and RSA each independently moderated the link between perceived event sociality and positive emotions, whereas only RSA predicted the probability of being with other people during an event. These findings suggest that OT and RSA may each be linked to positive social experiences in complementary yet distinct ways. (PsycINFO Database Record

Emotional maltreatment is associated with atypical responding to stimulation of endogenous oxytocin release through mechanically-delivered massage in males.

The neuropeptide oxytocin plays an important role in social behavior, parenting, and affectionate touch and there is some evidence that oxytocin release can be stimulated by massage or affectionate touch. We examined the effects of massage applied by a massage seat cover on salivary oxytocin levels in two exploratory studies using within-subject designs. In Study 1 massage effects on oxytocin levels were examined in a sample of N=20 healthy female participants. Effects of a 15-min massage session were compared to a control condition during which participants sat on a comfortable chair without a massage seat cover. Salivary oxytocin levels were measured at baseline and up to three hours after the session. We found that massage attenuated oxytocin decreases over time, indicating that massage stimulates oxytocin release. In Study 2, we examined whether effects of massage in N=46 healthy male participants depend on experiences of emotional maltreatment. In addition, we examined whether enhanced oxytocin levels after massage affect the use of excessive handgrip force in response to infant crying and laughter as measured with a handgrip dynamometer. Our findings show that massage results in elevated oxytocin levels compared to a control condition, but that the effects of massage are dependent on experiences of emotional maltreatment. Men with experiences of emotional maltreatment showed lower oxytocin levels, which did not increase after massage. Furthermore, we found that high oxytocin levels after massage were related to reduced handgrip force during exposure to infant crying and laughter, indicating that massage stimulates a sensitive response to infant signals by stimulating oxytocin release. Although massage did not affect oxytocin levels in individuals with experiences of maltreatment, it reduced the use of handgrip force in response to infant crying and laughter in these individuals. Our findings indicate that emotional maltreatment is associated with atypical responding to stimulation of endogenous oxytocin release.

Dietary sodium restriction alters postprandial ghrelin: implications for race differences in obesity.

OBJECTIVES: To examine the effect of sodium restriction on the appetite-stimulating hormone, ghrelin, as a function of race, salt sensitivity, and obesity. DESIGN: PARTICIPANTS completed two 4-day outpatient dietary interventions (moderate vs low sodium), and blood samples were drawn two hours after a controlled test meal under both conditions. SETTING: A university research laboratory and affiliated General Clinical Research Center. PARTICIPANTS: 37 women (18 Black, 19 White) and 18 men (9 Black, 9 White), aged 36-63 years. MEASURES: Cardiovascular function (blood pressure, heart rate, impedance-derived indices of cardiac output and peripheral resistance) was measured after a 20-minute rest before each test meal. Blood was drawn by intravenous forearm catheter two hours after each test meal and later assayed for ghrelin, leptin, and norepinephrine. RESULTS: After four days of sodium restriction, postprandial ghrelin increased in White men and women and Black men but decreased in Black women. Salt sensitivity, but not obesity, was also related to ghrelin response during sodium restriction; postprandial ghrelin tended to increase among salt-sensitive subjects during salt restriction but decrease among salt-resistant subjects during salt restriction. CONCLUSIONS: Satiety hormone dysregulation may play a role in: 1) the heightened obesity-related morbidity among Black women, in particular; 2) adherence to sodium-restricted diets; and 3) race differences in behavioral weight-loss interventions that include sodium restriction.

Thalamocortical functional connectivity and behavioral disruptions in neonates with prenatal cocaine exposure.

Prenatal cocaine exposure (PCE) affects neurobehavioral development, however, disentangling direct drug-related mechanisms from contextual effects (e.g., socioeconomic status) has proven challenging in humans. The effects of environmental confounds are minimal immediately after birth thus we aimed to delineate neurobehavioral correlates of PCE in a large cohort of neonates (2-6weeks of age, N=152) with and without drug exposure using resting state functional magnetic resonance imaging (rsfMRI) and developmental assessments at 3months with the Bayley Scales of Infant & Toddler Development, 3rd edition. The cohort included healthy controls and neonates with similar poly-drug exposure±cocaine. We focused on the thalamus given its critical importance in early brain development and its unique positioning in the dopamine system. Our results revealed PCE-related hyper-connectivity between the thalamus and frontal regions and a drug-common hypo-connective signature between the thalamus and motor-related regions. PCE-specific neonatal thalamo-frontal connectivity was inversely related to cognitive and fine motor scores and thalamo-motor connectivity showed a positive relationship with composite (gross plus fine) motor scores. Finally, cocaine by selective-serotonin-reuptake-inhibitor (SSRI) interactions were detected, suggesting the combined use of these drugs during pregnancy could have additional consequences on fetal development. Overall, our findings provide the first delineation of PCE-related disruptions of thalamocortical functional connectivity, neurobehavioral correlations, and drug-drug interactions during infancy.

Correction: Psychological Well-Being and the Human Conserved Transcriptional Response to Adversity.

[This corrects the article DOI: 10.1371/journal.pone.0121839.].

Effects of partner support on resting oxytocin, cortisol, norepinephrine, and blood pressure before and after warm partner contact.

OBJECTIVE: We examined whether the magnitude of plasma oxytocin (OT), norepinephrine (NE), cortisol, and blood pressure (BP) responses before and after a brief episode of warm contact (WC) with the spouse/partner may be related to the strength of perceived partner support. METHODS: Subjects were 38 cohabiting couples (38 men, 38 women) aged 20 to 49 years. All underwent 10 minutes of resting baseline alone, 10 minutes of WC together with their partner, and 10 minutes of postcontact rest alone. RESULTS: Greater partner support (based on self-report) was related to higher plasma oxytocin in men and women across the protocol before and after WC. In women, higher partner support was correlated with lower systolic blood pressure (SBP) during solitary rest after WC but not before. Also, higher OT in women was linked to lower BP at baseline and to lower NE at all 4 measurements. CONCLUSION: Greater partner support is linked to higher OT for both men and women; however, the importance of OT and its potentially cardioprotective effects on sympathetic activity and BP may be greater for women.

More frequent partner hugs and higher oxytocin levels are linked to lower blood pressure and heart rate in premenopausal women.

In animals, ventral stroking for >5 days increases oxytocin (OT) activity and decreases blood pressure (BP), but related human studies are few. Thus, relationships between self-reported frequency of partner hugs, plasma OT and BP levels were examined in 59 premenopausal women before and after warm contact with their husbands/partners ending with hugs. Higher baseline OT before partner contact was associated with lower BP and heart rate, and met criteria to be a partial mediator of the lower resting BP shown by women reporting more frequent hugs (P<0.05). OT levels during post-contact stress were unrelated to hugs or BP. Menstrual cycle phase did not influence any OT measure. Thus, frequent hugs between spouses/partners are associated with lower BP and higher OT levels in premenopausal women; OT-mediated reduction in central adrenergic activity and peripheral effects of OT on the heart and vasculature are pathways to examine in future research.

Psychological well-being and the human conserved transcriptional response to adversity.

Research in human social genomics has identified a conserved transcriptional response to adversity (CTRA) characterized by up-regulated expression of pro-inflammatory genes and down-regulated expression of Type I interferon- and antibody-related genes. This report seeks to identify the specific aspects of positive psychological well-being that oppose such effects and predict reduced CTRA gene expression. In a new confirmation study of 122 healthy adults that replicated the approach of a previously reported discovery study, mixed effect linear model analyses identified a significant inverse association between expression of CTRA indicator genes and a summary measure of eudaimonic well-being from the Mental Health Continuum - Short Form. Analyses of a 2- representation of eudaimonia converged in finding correlated psychological and social subdomains of eudaimonic well-being to be the primary carriers of CTRA associations. Hedonic well-being showed no consistent CTRA association independent of eudaimonic well-being, and summary measures integrating hedonic and eudaimonic well-being showed less stable CTRA associations than did focal measures of eudaimonia (psychological and social well-being). Similar results emerged from analyses of pooled discovery and confirmation samples (n = 198). Similar results also emerged from analyses of a second new generalization study of 107 healthy adults that included the more detailed Ryff Scales of Psychological Well-being and found this more robust measure of eudaimonic well-being to also associate with reduced CTRA gene expression. Five of the 6 major sub-domains of psychological well-being predicted reduced CTRA gene expression when analyzed separately, and 3 remained distinctively prognostic in mutually adjusted analyses. All associations were independent of demographic characteristics, health-related confounders, and RNA indicators of leukocyte subset distribution. These results identify specific sub-dimensions of eudaimonic well-being as promising targets for future interventions to mitigate CTRA gene expression, and provide no support for any independent favorable contribution from hedonic well-being.

Postprandial ghrelin is elevated in black compared with white women.

Ghrelin, a gut-brain peptide that signals hunger, is normally suppressed after meals. Subnormal suppression of postprandial ghrelin, previously noted in obese, insulin-resistant individuals, may contribute to increased food intake. Given the ethnic disparities in obesity and obesity-related cardiovascular morbidity in the United States, the present study compared a single postprandial ghrelin measure in 43 women (22 white, 21 black). Each completed a rigorously controlled 4-d dietary intervention designed to maintain weight and constant daily sodium and potassium intake (220 mEq Na, 40 mEq K). Two hours after consuming a test meal of identical content, blood samples were drawn to assess postprandial ghrelin, leptin, and norepinephrine; resting cardiovascular function was measured; and a 24-h urinary cortisol sample was obtained. Independent of body mass index, postprandial ghrelin was significantly higher in black vs. white women, and higher ghrelin was associated with higher cortisol in blacks, who failed to show the expected inverse relation between ghrelin and central obesity seen in whites. Higher ghrelin was correlated with higher blood pressure but lower norepinephrine in obese women. These findings suggest subnormal postprandial ghrelin suppression (or faster ghrelin rebound) in black women, especially the obese, that might play a role in their increased prevalence of obesity and cardiovascular disorders.

Depressive symptoms are related to higher ambulatory blood pressure in people with a family history of hypertension.

OBJECTIVE: We investigated whether parental history of hypertension (FH+) enhances the impact of depressed mood, indexed by Beck Depression Inventory (BDI), on ambulatory blood pressure (ABP). METHODS: Twenty-four-hour ABP, urinary norepinephrine (NE), and cortisol were obtained in 314 unmedicated normotensive and hypertensive men and women (age 18-64 years) who also completed the BDI. RESULTS: Subjects with a positive family history of hypertension (N = 177) exhibited significantly greater mean body mass index (BMI) and ABP compared with subjects without (N = 137). Importantly, when covarying for age, BMI, gender, and race, linear regressions revealed significant FH by BDI interactions. Higher BDI scores were significantly associated with higher 24-hour ABP in FH+ subjects, but not in FH- participants. Relationships were significantly stronger in those with two hypertensive parents vs. those with one vs. those with no hypertensive parents. Increases in BDI scores were significantly related to greater heart rate (HR) and 24-hour urinary NE in both FH+ and FH- groups, although no evidence of a mediational role for NE in the effect of BDI score on blood pressure (BP) or HR was seen. CONCLUSIONS: These findings suggest that depressed mood may be reliably associated with higher BP only among those with an underlying susceptibility to HTN.

Transdermal versus oral estrogen therapy in postmenopausal smokers: hemodynamic and endothelial effects.

OBJECTIVE: To test the hypothesis that, in postmenopausal smokers, transdermal estrogen would be more effective than oral estrogen in reducing blood pressure (BP) and vascular and norepinephrine responses to stress and in increasing endothelial function and vascular beta2-adrenoceptor responsivity. METHODS: By using a randomized, double-blind, placebo-controlled design, 82 healthy postmenopausal smokers were tested before and after 6 months of therapy with transdermal estrogen (0.05 mg/d) plus a progestin (2.5 mg/d; n = 31), oral conjugated equine estrogen (0.625 mg/d) plus a progestin (2.5 mg/d; n = 30), or placebo (n = 21). Dependent measures included resting and stress-induced increases in BP, total peripheral resistance, and plasma norepinephrine, as well as endothelial function and beta-adrenoceptor responsivity. RESULTS: When compared with placebo, the transdermal estrogen group showed more consistent reductions in total peripheral resistance at rest and in response to mental stress than the oral estrogen group. Only the transdermal group showed treatment-related reductions in behavioral stress norepinephrine, baseline rest, and behavioral stress BP levels, and increases in vascular beta2-adrenoceptor responsivity and endothelium-dependent vasodilation. Posttreatment concentrations of serum estradiol and estrone were lower and the serum estradiol/estrone ratio closer to pre-menopausal values in the group receiving transdermal estrogen compared with oral estrogen. CONCLUSION: Six months of transdermal estrogen therapy is associated with greater reductions in measures reflecting vascular sympathetic tone than oral estrogen therapy in healthy postmenopausal smokers. Thus, transdermal estrogen may be associated with a more favorable risk/ benefit ratio in postmenopausal smokers, a group at high risk of osteoporosis and cardiovascular disease.