Vascular responses to fear-induced stress in humans

Role of virtual reality in examining the effect of fear of falling (FOF) on postural stability in individuals without and with Parkinson's disease in Egypt: a mixed-methods feasibility study protocol

BACKGROUND

Falls are common in older people and individuals with neurological conditions. Parkinson's disease (PD) is known for postural instability causing mobility disabilities, falls and reduced quality of life. The fear of falling (FOF), a natural response to unstable balance, can worsen postural control problems. Evaluating FOF relies largely on affected persons' subjective accounts due to limited objective assessment methods available. The aim of this mixed-methods feasibility study is to develop an assessment method for FOF while in motion and walking within virtual environments. This study will assess a range of FOF-related responses, including cognitive factors, neuromuscular response and postural stability.

METHODS AND ANALYSIS

This feasibility study will consist of four phases: the first two phases will include people without PD, while the other two will include people diagnosed with PD. Participants will be assessed for direct and indirect responses to real life, as well as virtual environment walking scenarios that may induce FOF. Data from questionnaires, different neurophysiological assessments, movement and gait parameters, alongside evaluations of usability and acceptability, will be collected. Semistructured interviews involving both participants and research assistants shall take place to elicit their experiences throughout different phases of the assessments undertaken. Demographic data, the scores of assessment scales, as well as feasibility, usability and acceptability of the measurement methods, will be illustrated via descriptive statistics. Movement and gait outcomes, together with neurophysiological data, will be extracted and calculated. Exploring relationships between different factors in the study will be achieved using a regression model. Thematic analysis will be the approach used to manage qualitative data.

ETHICS AND DISSEMINATION

This feasibility study was approved by the Ethics Committee of the Faculty of Physical Therapy, Kafr El Sheikh University, Egypt (number: P.T/NEUR/3/2023/46). The results of this study will be published in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Registry (NCT05931692).

Assessing systemic vascular resistance using arteriolar pulse transit time based on multi-wavelength photoplethysmography

OBJECTIVE

Sympathetic nerve activity affects blood pressure by contracting the arteriole, which can increase systemic vascular resistance (SVR). Consequently, SVR is a key factor affecting blood pressure. However, a method for measuring SVR continuously is lacking. This paper formulated and experimentally validated a method that uses the arteriolar pulse transmit time (aPTT) to track changes in SVR.

APPROACH

multi-wavelength photoplethysmogram (PPG), electrocardiogram (ECG), and galvanic skin response (GSR) data were simultaneously gathered using a measurement system designed by this study. Blood perfusion was monitored by Laser Doppler. Least mean square (LMS) is an adaptive filtering algorithm. Our LMS-based algorithm formulated in this study was used to calculate the aPTT from the multi-wavelength PPGs. A cold stimulation experiment was conducted to verify the relationship between aPTT determined by algorithm and arteriole vasodilation. An emotinal stimulation experiment conducted, in which GSR was employed to further verify the relationship between aPTT and SVR. Twenty healthy young participants were asked to watch movie clips, which excited their sympathetic nerves. The dynamic time warping (DTW) distance is applied to evaluate between correlation of GSR and aPTT.

MAIN RESULTS

The changes in aPTT was extracted using our LMS-based method. During the recovery period after cold stimulation, aPTT decreased with the average slope of -0.19, while blood perfusion increased with the average slope of 0.72. Meanwhile, 70% participants' DTW distance's median between aPTT and GSR were significantly smaller than that between PTT and GSR during emotion stimulation.

SIGNIFICANCE

Our method uses aPTT, a continuous measurable parameter, to closely reflect SVR, as verified through experiments.

Fear Detection in Multimodal Affective Computing: Physiological Signals versus Catecholamine Concentration

Affective computing through physiological signals monitoring is currently a hot topic in the scientific literature, but also in the industry. Many wearable devices are being developed for health or wellness tracking during daily life or sports activity. Likewise, other applications are being proposed for the early detection of risk situations involving sexual or violent aggressions, with the identification of panic or fear emotions. The use of other sources of information, such as video or audio signals will make multimodal affective computing a more powerful tool for emotion classification, improving the detection capability. There are other biological elements that have not been explored yet and that could provide additional information to better disentangle negative emotions, such as fear or panic. Catecholamines are hormones produced by the adrenal glands, two small glands located above the kidneys. These hormones are released in the body in response to physical or emotional stress. The main catecholamines, namely adrenaline, noradrenaline and dopamine have been analysed, as well as four physiological variables: skin temperature, electrodermal activity, blood volume pulse (to calculate heart rate activity. i.e., beats per minute) and respiration rate. This work presents a comparison of the results provided by the analysis of physiological signals in reference to catecholamine, from an experimental task with 21 female volunteers receiving audiovisual stimuli through an immersive environment in virtual reality. Artificial intelligence algorithms for fear classification with physiological variables and plasma catecholamine concentration levels have been proposed and tested. The best results have been obtained with the features extracted from the physiological variables. Adding catecholamine’s maximum variation during the five minutes after the video clip visualization, as well as adding the five measurements (1-min interval) of these levels, are not providing better performance in the classifiers.

Spousal emotional support and relationship quality buffers pupillary response to horror movies

Being satisfied in marriage provides protective stress buffering benefits to various health complications but the causal mechanisms and speed at which this is accomplished is less well understood. Much of the research on health and marriage has conceptualized marital quality in a unidimensional way, with high levels of either positivity or negativity. This conceptualization may not fully capture the nuanced benefits of marital relationships. Pupillometry is an innovative method which captures the effects of marital stress buffering on the body’s autonomic nervous system in real time; pupil dilation occurs within 200ms to stress exposure. Additionally, this method records hundreds of readings per second, providing precision and sensitivity. This preregistered experiment aimed to conceptually replicate previous pupillometry stress buffering results and extend the previous findings by including a generalizable, real-life stressor—viewing a horror movie—and multidimensional relationship quality effects. Eighty-three couples (166 participants) were quasi-grouped, based on a self-reported multidimensional relationship quality scale, to either supportive or ambivalent marital relationship conditions. They were then randomly assigned to either a spousal support (i.e., handholding) or non-support (spousal absence) condition and watched clips from both horror and nature movies while pupil dilation was measured. Tonic pupillary response results revealed that the horror video clips elicited a stress response and there were significant differences between the support and non-support conditions, as well as marital relationship quality conditions. These results frame the precision, speed, and sensitivity of pupillometry as a potentially fruitful method to investigate the causal mechanisms linking stress buffering and supportive marital relationships.

Horror Films and Grief

Many of the most popular and critically acclaimed horror films feature grief as a central theme. This article argues that horror films are especially suited to portraying and communicating the phenomenology of grief. We explore two overlapping claims. First, horror is well suited to represent the experience of grief, in particular because the disruptive effects of horror “monsters” on protagonists mirror the core experience of disruption that accompanies bereavement. Second, horror offers ways in which the experience of grief can be contained and regulated and, in doing so, may offer psychological benefits for the bereaved. While our focus will be squarely on film, much of what we say applies to other media.

Silicon supplementation improves the nutritional and sensory characteristics of lentil seeds obtained from drought-stressed plants

BACKGROUND

Lentil is an important nutritionally rich pulse crop in the world. Despite having a prominent role in human health and nutrition, it is very unfortunate that global lentil production is adversely limited by drought stress, causing a huge decline in yield and productivity. Drought stress can also affect the nutritional profile of seeds. Silicon (Si) is an essential element for plants and a general component of the human diet found mainly in plant-based foods. This study investigated the effects of Si on nutritional and sensory properties of seeds obtained from lentil plants grown in an Si-supplied drought-stressed environment.

RESULTS

Significant enhancements in the concentration of nutrients (protein, carbohydrate, dietary fibre, Si) and antioxidants (ascorbate, phenol, flavonoids, total antioxidants) were found in seeds. Significant reductions in antinutrients (trypsin inhibitor, phytic acid, tannin) were also recorded. A novel sensory analysis was implemented in this study to evaluate the unconscious and conscious responses of consumers. Biometrics were integrated with a traditional sensory questionnaire to gather consumers responses. Significant positive correlations (R = 0.6-1) were observed between sensory responses and nutritional properties of seeds. Seeds from Si-treated drought-stressed plants showed higher acceptability scores among consumers.

CONCLUSION

The results demonstrated that Si supplementation can improve the nutritional and sensory properties of seeds. This study offers an innovative approach in sensory analysis coupled with biometrics to accurately assess a consumer's preference towards tested samples. In the future, the results of this study will help in making a predictive model for sensory traits and nutritional components in seeds using machine-learning modelling techniques. © 2020 Society of Chemical Industry.

Car drivers coping with hazardous events in real versus simulated situations: Declarative, behavioral and physiological data used to assess drivers' feeling of presence

More than 1.3 million people lose their lives every year in traffic accidents. Improving road safety requires designing better vehicles and investigating drivers’ abilities more closely. Driving simulators are constantly being used for this purpose, but the question which often arises as to their validity tends to be a barrier to developments in this field. Here we studied the validity of a simulator, defined as how closely users’ behavior under simulated conditions resembles their behavior on the road, based on the concept of drivers’ feeling of presence. For this purpose, the driving behavior, physiological state and declarative data of 41 drivers were tested in the Sherpa2 simulator and in a real vehicle on a track while driving at a constant speed. During each trial, drivers had to cope with an unexpected hazardous event (a one-meter diameter gym ball crossing the road right in front of the vehicle), which occurred twice. During the speed-maintenance task, the simulator showed absolute validity, in terms of the driving and physiological parameters recorded. During the first hazardous event, the physiological parameters showed that the level of arousal (Low Heart Rate/High Heart Rate ratio x10) increased up to the end of the drive. On the other hand, the drivers’ behavioral (braking) responses were 20% more frequent in the simulator than in the real vehicle, and the physiological state parameters showed that stress reactions occurred only in the real vehicle (+5 beats per minute, +2 breaths per minute and the phasic skin conductance increased by 2). In the subjects’ declarative data, several feeling of presence sub-scales were lower under simulated conditions. These results suggest that the validity of motion based simulators for testing drivers coping with hazards needs to be questioned.

The Psychobiological Etiology of Gastrointestinal Distress in Sport: A Review

Gastrointestinal (GI) disturbances are common during training and competition, especially among endurance athletes. Historically, little attention has been paid to the psychobiological etiology of GI problems in sport. The aim of this review is to: (1) provide a physiological overview of how psychological stress and anxiety impact GI system function; (2) review the literature that has examined the role of stress and anxiety in GI distress in athletes; and (3) provide suggestions for future research. Animal and human studies have documented that psychological stressors reduce gastric motility and delay stomach emptying while simultaneously increasing large intestine motility. These functional changes are likely mediated through the secretion of corticotropin-releasing factor and subsequent alterations in autonomic nervous system activity, which act to reduce splanchnic blood flow and increase GI permeability. In addition, chronic stress and anxiety may worsen GI discomfort by increasing visceral hypersensitization. Still, only a couple of studies have found modest associations between stress, anxiety, and the occurrence/severity of GI distress in active populations. As such, future work should attempt to confirm that experimentally inducing psychological stress results in the aforementioned GI problems during exercise. Furthermore, studies are needed to determine how psychological stress impacts the tolerance to nutritional fueling and whether it worsens the GI permeability that normally occurs with exercise.

Towards Wearable and Flexible Sensors and Circuits Integration for Stress Monitoring

Excessive stress is one of the main causes of mental illness. Long-term exposure of stress could affect one's physiological wellbeing (such as hypertension) and psychological condition (such as depression). Multisensory information such as heart rate variability (HRV) and pH can provide suitable information about mental and physical stress. This paper proposes a novel approach for stress condition monitoring using disposable flexible sensors. By integrating flexible amplifiers with a commercially available flexible polyvinylidene difluoride (PVDF) mechanical deformation sensor and a pH-type chemical sensor, the proposed system can detect arterial pulses from the neck and pH levels from sweat located in the back of the body. The system uses organic thin film transistor (OTFT)-based signal amplification front-end circuits with modifications to accommodate the dynamic signal ranges obtained from the sensors. The OTFTs were manufactured on a low-cost flexible polyethylene naphthalate (PEN) substrate using a coater capable of Roll-to-Roll (R2R) deposition. The proposed system can capture physiological indicators with data interrogated by Near Field Communication (NFC). The device has been successfully tested with healthy subjects, demonstrating its feasibility for real-time stress monitoring.

Assessment of skin temperature during regional anaesthesia-What the anaesthesiologist should know

Body temperature homeostasis is accurately regulated by complex feedback-driven neuronal mechanisms, which involve a multitude of thermoregulatory pathways. Thus, core temperature is constantly maintained within a narrow range. As one of the most effective regulatory systems skin temperature is dependent on skin blood flow. Skin blood flow in turn is highly dependent on sympathetic activity. Regional anaesthesia leads to blockade not only of somatosensory and motor nerve fibres but also of sympathetic fibres. As a consequence, vasoconstrictor tonic activity is abrogated and a vasodilation leads to an increase in skin blood flow and temperature. The aim of this review was to summarize the general physiology of thermoregulation and skin temperature as well as the alterations during regional anaesthesia. The main focus was the usefulness of measuring skin temperature as an indicator of regional anaesthesia success. According to the available literature, assessment of skin temperature can indeed serve to predict success of regional anaesthesia. Hence, it is important to realize that relevant and reliable temperature increase is only seen in the most distal body parts, ie fingers and toes. More proximally, temperature changes are frequently small and inconsistent, which means that assessment of block levels is not possible by temperature measurement. Furthermore, relevant skin temperature increases will only be observed in patients, which are initially vasoconstricted. In conclusion, measurement of skin temperature represents a reliable and feasible diagnostic tool to assess and predict the success or failure of regional anaesthesia procedures, especially in patients in which sensory testing is impossible.

Deactivation of the prefrontal cortex during exposure to pleasantly-charged emotional challenge

Our laboratory reported that facial skin blood flow may serve as a sensitive tool to assess an emotional status and that both prefrontal oxygenation (as index of regional cerebral blood flow) and facial skin blood flow decrease during positively-charged emotional stimulation, without changing hand skin blood flow and arterial pressure. However, the focal location of the prefrontal responses in concentration of oxygenated haemoglobin (Oxy-Hb) that correlate with peripheral autonomic reaction remained unknown. This study was undertaken using 22-channel near-infrared spectroscopy to reveal spatial distribution of the responses in Oxy-Hb within the prefrontal cortex (PFC) during emotionally-charged audiovisual stimulation. Pleasantly-charged (comedy) stimulation caused a substantial decrease of Oxy-Hb in all regions of the PFC in 18 subjects, especially in the rostroventral frontopolar PFC, whereas negatively-charged (horror) or neutral stimulation (landscape) exhibited a weaker decrease or insignificant change in the prefrontal Oxy-Hb. In the rostral parts of the dorsolateral and ventral frontopolar PFC, the oxygenation response during comedy stimulation exhibited the most significant positive correlation with the decrease in facial skin blood flow. Thus the rostral regions of the PFC play a role in recognition and regulation of positive emotion and may be linked with neurally-mediated vasoconstriction of facial skin blood vessels.

Prefrontal oxygenation correlates to the responses in facial skin blood flows during exposure to pleasantly charged movie

Our laboratory reported that facial skin blood flow may serve as a sensitive tool to assess an emotional status. Cerebral neural correlates during emotional interventions should be sought in relation to the changes in facial skin blood flow. To test the hypothesis that prefrontal activity has positive relation to the changes in facial skin blood flow during emotionally charged stimulation, we examined the dynamic changes in prefrontal oxygenation (with near‐infrared spectroscopy) and facial skin blood flows (with two‐dimensional laser speckle and Doppler flowmetry) during emotionally charged audiovisual challenges for 2 min (by viewing comedy, landscape, and horror movie) in 14 subjects. Hand skin blood flow and systemic hemodynamics were simultaneously measured. The extents of pleasantness and consciousness for each emotional stimulus were estimated by subjective rating from −5 (the most unpleasant; the most unconscious) to +5 (the most pleasant; the most conscious). Positively charged emotional stimulation (comedy) simultaneously decreased (P < 0.05) prefrontal oxygenation and facial skin blood flow, whereas negatively charged (horror) or neutral (landscape) emotional stimulation did not alter or slightly decreased them. Any of hand skin blood flow and systemic cardiovascular variables did not change significantly during positively charged emotional stimulation. The changes in prefrontal oxygenation had a highly positive correlation with the changes in facial skin blood flow without altering perfusion pressure, and they were inversely correlated with the subjective rating of pleasantness. The reduction in prefrontal oxygenation during positively charged emotional stimulation suggests a decrease in prefrontal neural activity, which may in turn elicit neurally mediated vasoconstriction of facial skin blood vessels.

Facial skin blood flow responses during exposures to emotionally charged movies

The changes in regional facial skin blood flow and vascular conductance have been assessed for the first time with noninvasive two-dimensional laser speckle flowmetry during audiovisually elicited emotional challenges for 2 min (comedy, landscape, and horror movie) in 12 subjects. Limb skin blood flow and vascular conductance and systemic cardiovascular variables were simultaneously measured. The extents of pleasantness and consciousness for each emotional stimulus were estimated by the subjective rating from -5 (the most unpleasant; the most unconscious) to +5 (the most pleasant; the most conscious). Facial skin blood flow and vascular conductance, especially in the lips, decreased during viewing of comedy and horror movies, whereas they did not change during viewing of a landscape movie. The decreases in facial skin blood flow and vascular conductance were the greatest with the comedy movie. The changes in lip, cheek, and chin skin blood flow negatively correlated (P < 0.05) with the subjective ratings of pleasantness and consciousness. The changes in lip skin vascular conductance negatively correlated (P < 0.05) with the subjective rating of pleasantness, while the changes in infraorbital, subnasal, and chin skin vascular conductance negatively correlated (P < 0.05) with the subjective rating of consciousness. However, none of the changes in limb skin blood flow and vascular conductance and systemic hemodynamics correlated with the subjective ratings. The mental arithmetic task did not alter facial and limb skin blood flows, although the task influenced systemic cardiovascular variables. These findings suggest that the more emotional status becomes pleasant or conscious, the more neurally mediated vasoconstriction may occur in facial skin blood vessels.

Relation between blood flow and tissue blood oxygenation in human fingertip skin

BACKGROUND

Tissue blood flow (BF) is thought to be involved in the regulation of tissue blood oxygenation (StO2). The purpose of the present study was to show the relation between BF and StO2 by measuring them simultaneously under different conditions.

METHODS

Twenty-one healthy subjects (age 21-30years) participated in this study. We measured BF and StO2 in a small area of skin (fingertip, palm, forearm) simultaneously using a laser Doppler flowmeter and a tissue oxygenation monitor. Three measurements were made at rest while performing mental arithmetic and during constriction of the ipsilateral upper arm.

RESULTS

At rest, BF and StO2 were higher in the fingertip than in the palm or forearm (p<0.01). Performing mental arithmetic produced significant decreases in BF, oxygenated hemoglobin, and StO2 in the fingertip (p<0.05). Constriction of the ipsilateral upper arm produced significant decreases in BF and StO2 (p<0.05) and an increase in oxygenated hemoglobin (p<0.05). Both procedures produced significant increases in deoxygenated hemoglobin (p<0.05), which was in antiphase to the decrease in StO2.

CONCLUSIONS

BF decrease produced a significantly decreased StO2 in fingertip skin. The results show that simultaneous measurement of BF and StO2 is beneficial for showing the close relation between them.

Comparison of operant escape and reflex tests of nociceptive sensitivity

Testing of reflexes such as flexion/withdrawal or licking/guarding is well established as the standard for evaluating nociceptive sensitivity and its modulation in preclinical investigations of laboratory animals. Concerns about this approach have been dismissed for practical reasons - reflex testing requires no training of the animals; it is simple to instrument; and responses are characterized by observers as latencies or thresholds for evocation. In order to evaluate this method, the present review summarizes a series of experiments in which reflex and operant escape responding are compared in normal animals and following surgical models of neuropathic pain or pharmacological intervention for pain. Particular attention is paid to relationships between reflex and escape responding and information on the pain sensitivity of normal human subjects or patients with pain. Numerous disparities between results for reflex and operant escape measures are described, but the results of operant testing are consistent with evidence from humans. Objective reasons are given for experimenters to choose between these and other methods of evaluating the nociceptive sensitivity of laboratory animals.

The effects of negative emotions on sensory perception: fear but not anger decreases tactile sensitivity

Emotions and sensory perceptions are closely intertwined. Of the five senses, sight has been by far the most extensively studied sense in emotion research. Relatively less is known about how emotions influence the other four senses. Touch is essential for nonverbal communication in both humans and other animals. The current investigation tested competing hypotheses about the effect of fear on tactile perception. One hypothesis based on evolutionary considerations predicts that fear enhances sensory perception, including tactile sensitivity. A competing hypothesis based on research on peripheral psychophysiology predicts that fear should decrease tactile sensitivity. Two experiments that induced negative emotional states and measured two-point discrimination ability at the fingertip found that fear reduces tactile sensitivity relative to anger or a neutral control condition (Studies 1 and 2). These findings did not appear to be driven by participants’ naïve beliefs about the influence of emotions on touch (Study 3). The results represent the first evidence of the causal impact of emotional states on tactile sensitivity, are consistent with prior evidence for the peripheral physiological effects of fear, and offer novel empirical grounds for developing and advancing theories of emotional influences on sensory perception.

Palatability of tastes is associated with facial circulatory responses

To examine whether various types of taste stimuli in the oral cavity elicit unique changes in facial skin blood flow (SkBF) according to the palatability perceived by an individual, the facial SkBF was observed by laser speckle flowgraphy in 15 healthy subjects (11 males and 4 females) before and during the ingestion of bitter tea, chilli sauce, coffee, orange juice, soup, and a water control. The heart rate, mean arterial pressure (MAP), and SkBF in the index finger were recorded continuously. Subjects reported their subjective palatability and taste intensity scores after each stimulus. The vascular conductance indexes (CIs) in the face and finger were calculated as ratios of SkBF to MAP. CI in the eyelid increased significantly in response to chilli sauce, orange juice, and soup, whereas CIs in the forehead, nose, and cheek decreased in response to bitter tea. There was a significant correlation between the palatability scores and CI values in the eyelid when changes induced by chilli sauce were excluded. These results suggest that the facial circulatory response reflects the degree of palatability of a foodstuff.

Cardiovascular response to psychosocial repeated stress in caregivers of offspring with schizophrenia

Taking care of offspring suffering a long-term illness such as schizophrenia is one of the more stressful life experiences. Care conditions may act as a protective factor in the health of the caregiver. The present study assesses heart rate (HR), blood pressure (BP), and mood responses to psychosocial stress in 16 mothers receiving specialised support for the care of their offspring (CARE+) and in 11 mothers caring for their offspring without support (CARE-). The CARE- group take care of less functional and more symptomatic offspring; and display higher basal, but lower HR, responses after stress than the CARE+ group. No significant group effects were found for BP. For mood states, there were significant decreases in the anger subscale in the CARE- group that were not found in the CARE+ group. HR was related to active and passive coping styles, trait anxiety, and years spent providing care. In the total sample, other significant relationships between cardiovascular responses and life events and personality traits have been found. In sum, the data suggests that specialised support for patients may modulate cardiovascular responses to repeated stress in caregivers.

Influence of rubber dam on objective and subjective parameters of stress during dental treatment of children and adolescents - a randomized controlled clinical pilot study

BACKGROUND

Rubber dam is recommended for isolating the working field during adhesive dentistry procedures; however, dentists often omit rubber dam, particularly in paediatric dentistry, supposing that it would stress the patient.

AIM

The aim of this study was to evaluate stress parameters during a standardized dental treatment procedure performed with or without rubber dam. The treatment time was measured as a secondary outcome variable.

DESIGN

This study was designed as a randomized, controlled, clinical study with 72 patients (6-16 years; mean age, 11.1). During standardized fissure sealing procedures, objective parameters of stress (e.g., skin resistance, breath rate) were recorded. The operator's stress level was measured by pulse rate. Subjective pain (patients) and stress perception (operator) were evaluated by an interview.

RESULTS

The breath rate was significantly (P<0.05) lower and the skin resistance level was significantly higher during treatment with rubber dam compared to the control group. Subjective pain perception was significantly lower for the test group. The treatment time needed for the fissure sealing procedure was 12.4% less in the test group.

CONCLUSION

Isolation with rubber dam caused less stress in children and adolescents compared to relative isolation with cotton rolls if applied by an experienced dentist.

Regional differences in facial skin blood flow responses to the cold pressor and static handgrip tests

We have previously reported the unique regional responses of facial skin blood flow (SkBF) to oral application of the basic tastes without simultaneous systemic circulatory changes. In the present study, we determined whether a systemic circulatory challenge due to sympathetic activation induces regional differences in facial SkBF by observing the responses in facial SkBF and blood pressure to a 2-min cold pressor test (CPT) and static handgrip exercise (HG) by right hand in 20 healthy subjects. The CPT significantly increased SkBF in the forehead, eyelid, cheek, upper lip and lower lip by 6 ± 2 to 8 ± 2 % (mean ± SEM) as compared to resting baseline, with a significant simultaneous increase (13 ± 2 %) in mean arterial pressure (MAP), whereas it significantly decreased the SkBF in the nose by 5 ± 2 %. The HG significantly increased SkBF in the forehead, cheek and lower lip by 6 ± 3 to 10 ± 3 %, with a significant simultaneous increase in MAP (13 ± 2 %), while it induced no significant change in the other regions. Increases in SkBF were greater in the right than left cheek during CPT. These results demonstrate that a systemic circulatory challenge via sympathetic activation elicits regional differences in the facial SkBF response.

Immersing the foot in painfully-cold water evokes ipsilateral extracranial vasodilatation

Temporal pulse amplitude was recorded bilaterally in 56 participants before, during and after three ice-water immersions of the foot. Half of the participants were told that prolonged exposure to freezing temperatures could cause frostbite. Increases in pulse amplitude were greater in the ipsilateral than contralateral temple during and after the three foot-immersions. Although pulse amplitude decreased after threatening instructions and repeated immersion of the foot, the vasodilator response persisted during all three immersions. These findings suggest that nociceptive stimulation of the foot evokes an ipsilateral supra-spinal extracranial vasodilator response, possibly as part of a broader defense response.

Heart rate contributes to the vascular effects of chronic mental stress: effects on endothelial function and ischemic brain injury in mice

BACKGROUND AND PURPOSE

Vascular effects of mental stress are only partially understood. Therefore, we studied effects of chronic stress and heart rate (HR) on endothelial function and cerebral ischemia.

METHODS

129S6/SvEv mice were randomized to the I(f)-channel inhibitor ivabradine (10 mg/kg per day) or vehicle and underwent a chronic stress protocol for 28 days.

RESULTS

Stress increased HR from 514 ± 10 bpm to 570 ± 14 bpm, this was prevented by ivabradine (485 ± 7 bpm). Endothelium-dependent relaxation of aortic rings was impaired in mice exposed to stress. HR reduction restored endothelial function to the level of naive controls. Vascular lipid hydroperoxides were increased to 333% ± 24% and vascular NADPH oxidase activity was upregulated to 223 ± 38% in stressed mice, which was prevented by ivabradine. Stress reduced aortic endothelial nitric oxide synthase mRNA expression to 84% ± 3% and increased AT1 receptor mRNA to 168% ± 18%. Both effects were attenuated by HR reduction. In brain tissue, stress resulted in an upregulation of lipid hydroperoxides to 140% ± 11%, which was attenuated by HR reduction. Ivabradine increased brain capillary density in naive and in stressed mice. Mice exposed to chronic stress before induction of ischemic stroke by transient middle cerebral artery occlusion exhibited increased lesion size (33.7 ± 2.3 mm3 versus 23.9 ± 2.4 mm3). HR reduction led to a marked reduction of the infarct volume to 12.9 ± 3.3 mm3.

CONCLUSIONS

Chronic stress impairs endothelial function and aggravates ischemic brain injury. HR reduction protects from cerebral ischemia via improvement of endothelial function and reduction of oxidative stress. These results identify heart rate as a mediator of vascular effects induced by chronic stress.