Acute stress potentiates anxiety in humans

Salivary Alpha-Amylase Reactivity in Breast Cancer Survivors

The two main components of the stress system are the hypothalamic-pituitary-adrenal (HPA) and sympathetic-adrenal-medullary (SAM) axes. While cortisol has been commonly used as a biomarker of HPA functioning, much less attention has been paid to the role of the SAM in this context. Studies have shown that long-term breast cancer survivors display abnormal reactive cortisol patterns, suggesting a dysregulation of their HPA axis. To fully understand the integrity of the stress response in this population, this paper explored the diurnal and acute alpha-amylase profiles of 22 breast cancer survivors and 26 women with no history of cancer. Results revealed that breast cancer survivors displayed identical but elevated patterns of alpha-amylase concentrations in both diurnal and acute profiles relative to that of healthy women, F (1, 39) = 17.95, p < 0.001 and F (1, 37) = 7.29, p = 0.010, respectively. The average area under the curve for the diurnal and reactive profiles was 631.54 ± 66.94 SEM and 1238.78 ± 111.84 SEM, respectively. This is in sharp contrast to their cortisol results, which showed normal diurnal and blunted acute patterns. The complexity of the stress system necessitates further investigation to understand the synergistic relationship of the HPA and SAM axes.

Influence of Music on Anxiety Induced by Fear of Heights in Virtual Reality

Music is a potent mood regulator that can induce relaxation and reduce anxiety in different situations. While several studies demonstrate that certain types of music have a subjective anxiolytic effect, the reported results from physiological responses are less conclusive. Virtual reality allows us to study diverse scenarios of real life under strict experimental control while preserving high ecological validity. We aimed to study the modulating effect of music on the anxiety responses triggered by an immersive virtual reality scenario designed to induce fear of heights. Subjects experienced a virtual scenario depicting an exterior elevator platform ascending and descending the total height of its 350 meters tall supporting structure. Participants were allocated to either a group that experienced the elevator ride with background music or without, in a between-groups design. Furthermore, each group included participants with different degrees of fear of heights, ranging from low to high fear. Recordings of heart rate, galvanic skin response, body balance, and head movements were obtained during the experiments. Subjective anxiety was measured by means of three questionnaires. The scenario produced significant changes in subjective and physiological measures, confirming its efficacy as a stressor. A significant increase in state anxiety was found between pre and post-assessment in the silence group, but not in the music group, indicating that post-stress recovery was faster in the musical group. Results suggest that music can ameliorate the subjective anxiety produced by fear of heights.

Salivary alpha-amylase response following repeated psychosocial stress in patients with panic disorder

BACKGROUND

This study examined autonomic responses (salivary alpha-amylase, sAA; heart rate, HR) to repeated psychosocial stress as a candidate mechanism linking autonomic hyper-arousal and sensitization to the occurrence of panic disorder (PD).

METHODS

Thirty-three patients with PD and 34 healthy controls were exposed to the Trier Social Stress Test (TSST) twice on consecutive days.

RESULTS

sAA changes were comparable between PD and controls on both testing days with overall decreasing sAA responses (delta) on day two. In contrast, HR delta increased on day two in both groups. This sensitization was driven by female controls while male PD showed most pronounced HR changes to the first TSST.

CONCLUSIONS

Overall, a general autonomic hyper-arousal in PD could not be confirmed. In contrast, sAA responses slightly habituated to repeated stress. Whether sAA findings mirror assumed habituation effects of repeated stress exposure on normalizing autonomic reactivity remains to be investigated in longitudinal studies.

Pain in Times of Stress

Stress modulates pain perception, resulting in either stress-induced analgesia or stress-induced hyperalgesia, as reported in both animal and human studies. The responses to stress include neural, endocrine, and behavioural changes, and built-in coping strategies are in place to address stressors. Peculiar to humans are additional factors that modulate pain that are experienced in times of stress, notably psychological factors that potentially influence the directionality of pain perception.

Evaluation of Examination Stress and Its Effect on Cognitive Function among First Year Medical Students

BACKGROUND

Medical students experience stress at every phase of curriculum more so before examination. This stress may affect physiological, psychological and cognitive functions of the students.

AIM

The present study aimed to evaluate stress status among first year MBBS students by recording pulse rate (PR), systolic blood pressure (SBP), diastolic blood pressure (DBP) and using stress questionnaire; its effect on cognitive function by recording auditory reaction time (ART) and visual reaction time (VRT).

SETTING AND DESIGN

It is a cross-sectional study.

MATERIALS AND METHODS

A total of 100 (49 males and 51 females) first year healthy MBBS students participated. Stress questionnaire was given and assessed. Cardiovascular parameters were also assessed. The ART and VRT were recorded before (pre examination setting) and after 3 month of examination (post-examination setting).

STATISTICAL ANALYSIS

The data were analysed by using SPSS 21.0 version.

RESULTS

All parameters namely PR, SBP, DBP, ART, VRT and stress scores were increased in preexamination setting irrespective of gender. Increased PR was observed in female learners where as stress score and SBP were increased in males in pre-examination setting. ART and VRT were more in females as compared to males in both setting.

CONCLUSION

It is concluded that examination in the form of stressor hampers cognitive function of first year medical students. The cognitive functions of the female learners were more affected as compared to males. Therefore, proper counselling of the students should be initiated at the earliest to decrease their stress level.

Alcohol stress response dampening during imminent versus distal, uncertain threat

Research indicates that fear and anxiety are distinct processes with separable neurobiological substrates. Predictable versus unpredictable shock administration has been used to elicit fear versus anxiety, respectively. Recent research has demonstrated that alcohol may reduce anxiety but not fear. However, previous manipulations of predictability have varied both probability and temporal uncertainty of shock threat, leaving unresolved questions regarding which stimulus characteristics elicit anxiety and are sensitive to alcohol stress-response dampening (SRD). We developed a novel paradigm to closely parallel basic research in animals that systematically varied temporal uncertainty of threat while holding threat probability constant. Intoxicated (0.08% target blood alcohol concentration), placebo, and no-alcohol control participants viewed a series of visual threat cues. Certain cue duration (5 s) blocks were equivalent to predictable shock blocks eliciting fear in earlier research. Uncertain cue duration (5, 20, 50, or 80 s, intermixed) blocks introduced temporal uncertainty regarding impending shock to elicit anxiety. Startle potentiation relative to matched cue periods in no-shock blocks provided the primary measure of affective response. All threat cues produced robust startle potentiation. Alcohol reduced startle potentiation during the first 5 s of threat cue presentation in uncertain but not certain duration blocks. Alcohol also reduced startle potentiation at later times among longer uncertain duration cues, suggesting that alcohol SRD persisted. Trait negative emotionality and binge drinking status moderated alcohol SRD magnitude during uncertain threat. These translational findings corroborate previous reports regarding distinct substrates of fear versus anxiety and have implications for both alcoholism etiology and comorbidity with anxiety disorders.

Effects of seasonal differences in testosterone and cortisol levels on pain responses under resting and anxiety conditions

PURPOSE

This study investigated whether hormones and pain perception are associated with exam anxiety, and also whether exam anxiety is affected by seasonal differences in testosterone and cortisol levels.

MATERIALS AND METHODS

Forty-six healthy males were recruited from a medical college. Anxiety was induced by having participants perform the Objective Structured Clinical Examination. Pressure was applied to the participants to induce pain. Pain thresholds, pain ratings, anxiety ratings, blood pressure, heart rate, salivary testosterone and cortisol levels were measured under resting and anxiety conditions in the spring and summer. Data were collected from 46 participants during the spring (n=25) and summer (n=21).

RESULTS

Pain thresholds and testosterone levels were significantly lower under anxiety than at rest for all participants (n=46), while cortisol levels, pain ratings, and anxiety ratings were significantly higher under anxiety than at rest. In the spring (n=25), testosterone levels were significantly higher at rest than under anxiety, while there was no difference in cortisol levels between resting and anxiety conditions. In the summer (n=21), cortisol levels were significantly higher under anxiety than at rest, while there was no difference in testosterone levels between resting and anxiety conditions. There were no significant seasonal differences in pain and anxiety ratings and pain threshold.

CONCLUSION

These results indicate that seasonal differences in testosterone and cortisol levels under anxiety and at rest may affect pain responses. These results also suggest that acute clinical pain may be relieved by managing anxiety that is related to a decrease of testosterone in spring and a large increase of cortisol in summer.

Cardiovascular effects of Boophone disticha aqueous ethanolic extract on early maternally separated BALB/C mice

ETHNOPHARMACOLOGICAL RELEVANCE

There are a number of reports from traditional medical practice in Zimbabwe and neighboring countries and few in vitro studies suggesting an effect with extracts of Boophone disticha in some forms of anxiety disorder.

AIM OF THE STUDY

In order to validate the use of Boophone disticha in treatment of anxiety, this study was set to determine the effects of the plant extracts on blood pressure (BP) and heart rate (HR) in adult BALB/c mice subjected to repeated early maternal separation (MS) stress.

MATERIALS AND METHODS

To test whether early life stress increases anxiety in mice, non-invasive tail cuff method was used to examine the autonomic nervous system activity by assessing cardiovascular reactivity and response to acute mixing stress (AMS) and restraint stress (RS) in adult mice subjected to early postnatal stress as compared to control. AMS-induced cardiovascular response was then evaluated in adult MS mice treated with Boophone disticha as compared to vehicle and diazepam.

RESULTS

Comparisons of the BP and HR measurements indicated that MS significantly reduced AMS-induced HR responses in BALB/c mice when compared with control. Boophone disticha treatment significantly reduced AMS-induced BP response in BALB/c MS mice as compared to vehicle and diazepam treatments.

CONCLUSIONS

Our findings demonstrate for the first time that postnatal stress can induce short-term changes in the sensitivity of the cardiovascular system to subsequent stress which can be reduced by treatment with a freeze dried aqueous ethanolic extract of Boophone disticha.

Is salivary alpha-amylase an indicator of autonomic nervous system dysregulations in mental disorders?--a review of preliminary findings and the interactions with cortisol

During recent years, a growing interest emerged in using salivary alpha-amylase (sAA) as a non-invasive, surrogate marker for sympathetic activity. Numerous studies applying stress protocols have demonstrated that sAA is highly sensitive to stress-related changes (in healthy subjects). Additionally, it was suggested that sAA might moreover serve as an index for pathological dysregulation of the autonomic nervous system (ANS) in patients showing psychopathology. Since then, a small but growing literature investigated sAA in patients with mental disorders. This review aims to give an overview of preliminary findings in this field of research. The results of n=15 studies are described in detail and implications for further research are discussed. Although the number of studies and the samples examined were rather small, changes in sAA, reflecting adrenergic dysregulation, could be demonstrated in psychopathology, especially in anxiety-related disorders. This field of research is still in its early stages. However, the studies included in this review revealed first evidence that the employment of sAA, as an indicator of ANS dysregulation in mental disorders, is promising.

Alcohol stress response dampening: selective reduction of anxiety in the face of uncertain threat

Problematic alcohol use and stress response dampening (SRD) are intimately interconnected. Recent evidence suggests that alcohol produces selective SRD during uncertain but not certain threat. We systematically varied shock probability in a novel task assessing alcohol SRD during low probable/uncertain threat, while holding temporal precision of threat constant. Intoxicated (0.08% target blood alcohol concentration) and placebo participants completed a cued shock threat task in which probability of shock administration at the offset of brief visual cues varied parametrically. High probability (100%) shock cues represented certain threat as used in earlier research, while lower probability (20% and 60%) shock cues provided novel uncertain threat conditions. Startle potentiation during cues and inter-trial intervals (ITIs) served as the measure of affective response. General linear model analysis indicated that alcohol SRD magnitude increased monotonically as threat uncertainty increased. Alcohol SRD was significantly greater during 20% and 60% shock threat relative to 100% shock threat. Alcohol also significantly reduced startle potentiation during distal threat in shock-free ITIs. Alcohol SRD magnitude during distal/uncertain threat was meaningfully moderated by individual differences in negative affectivity and weekly alcohol consumption. This work advances understanding of which properties of uncertainty are relevant to anxiety and anxiolytic effects of alcohol.

Investigation into the cross-correlation of salivary cortisol and alpha-amylase responses to psychological stress

Stress is a multidimensional construct. To accurately represent stress physiology, multiple stress measures across multiple stress-related systems should be assessed. However, associations may be masked given that different systems underlie different time courses. Salivary cortisol and alpha-amylase (sAA) are reliable biological stress markers of the sympathetic nervous system (SNS) and the hypothalamus pituitary adrenal (HPA) axis, respectively. Studies examining the link between sAA and cortisol levels in response to stress have produced inconsistent results. Here, we investigated whether the covariance of stress-induced sAA and cortisol release is dependent on the distinct temporal dynamics of the two stress markers. A total of 50 male participants were exposed to a psychological laboratory stressor with high frequency (2-min interval) saliva sampling in two independent studies. Synchronized time series of sAA and cortisol measures before, during and after stress induction were obtained. Cross-correlation analysis was applied to test for the association of sAA and cortisol levels at various stages relative to the onset of the stressor. Positive and negative cross-correlations between lagged pairs of sAA and cortisol measures were found in both studies. The strongest correlation was found for sAA preceding cortisol release by 13.5 min (r = .27, p < .001). With a smaller effect size cortisol also significantly preceded sAA by 13.5 min (r = -.16, p < .001). We suggest that sAA and cortisol stress responses are reliably associated at various time lags throughout a stressful situation. As a possible connection site between HPA axis and SNS that may underlie sAA-cortisol associations, we discuss CRF neurons of the hypothalamus involved in sympathetic regulation.

Heart rate as a marker of stress in ambulance personnel: a pilot study of the body's response to the ambulance alarm

INTRODUCTION

Studies have demonstrated the presence of stress and post-traumatic stress among ambulance personnel, but no previous research has focused on the body's reaction in the form of the change in heart rate of ambulance staff in association with specific occupational stress.

HYPOTHESIS

The purpose of this study is to investigate whether work as an ambulance professional generates prolonged physiological arousal that can be measured by heart rate in different situations.

METHODS

Twenty participants carried a pulse-meter in the form of a wristwatch, which continuously measured and stored their heart rate 24 hours per day for a period of seven days. All ambulance alarms that occurred during the test period were recorded in journals, and the participants completed diaries and a questionnaire describing their experiences. The alarms were divided into different phases. Correlations between heart rate in the different phases were computed.

RESULTS

Analysis of study data indicated a significant rise of heart rate unrelated to physical effort during an emergency alarm and response. This increased heart rate was noticed throughout the mission and it was not related to the length of experience the staff had in the ambulance profession. In addition, a non-significant trend suggested that alarms involving acutely ill children lead to an even higher increase in heart rate. In addition, this research showed that constant tension existed during sleep, while available for an emergency, indicated by a noticeable increase in heart rate during sleep at work compared to sleeping at home.

CONCLUSIONS

A rise in heart rate was experienced during all acute emergency missions, regardless of a subject's experience, education, and gender. Missions by themselves generated a rate increase that did not seem to correlate with physical effort required during an emergency response. This study shows that working on an ambulance that responds to medical emergencies is associated with a prolonged physiological arousal.

Affective reactivity in heroin-dependent patients with antisocial personality disorder

The Antisocial personality disorder (ASPD), one of the most common co-morbid psychiatric disorders in heroin-dependent patients, is associated with a lack of affective modulation. The present study aimed to compare the affect-modulated startle responses of opioid-maintained heroin-dependent patients with and without ASPD relative to those of healthy controls. Sixty participants (20 heroin-dependent patients with ASPD, 20 heroin-dependent patients without ASPD, 20 healthy controls) were investigated in an affect-modulated startle experiment. Participants viewed neutral, pleasant, unpleasant, and drug-related stimuli while eye-blink responses to randomly delivered startling noises were recorded continuously. Both groups of heroin-dependent patients exhibited significantly smaller startle responses (raw values) than healthy controls. However, they showed a normal affective modulation: higher startle responses to unpleasant, lower startle responses to pleasant stimuli and no difference to drug-related stimuli compared to neutral stimuli. These findings indicate a normally modulated affective reactivity in heroin-dependent patients with ASPD.

Exam anxiety induces significant blood pressure and heart rate increase in college students

To investigate the relationship between the anxiety and blood pressure (BP) and heart rate (HR) increase in peri-exam period. Sixty-four college students(20.0 ± 0.1 year old) were included in this study. The BP and HR were measured in the morning and in the evening for 3 days during the prereview (ba), review, and exam periods. The BP and HR increase amplitudes (HRIA) of review and exam periods were from the difference of corresponding values and basic values, and the BPIA/baBP and HRIA/baHR were calculated. All of the students completed the Self-Rating Anxiety score (SAS) questionnaire the first day of the exam period. Scores over 50 points were used as the standard for anxiety. From the prereview to exam periods, the BP and HR increased gradually. The exam SBPIA (4.3 ± 1.3 vs. 0.3 ± 0.5 mmHg, P < 0.05) and DBPIA (4.4 ± 1.5 vs. 1.0 ± 0.5 mmHg, P < 0.05) were significantly higher in the anxiety group than in the no-anxiety group. The SBPIA/DBPIA and HRIA showed a similar profile also(9.7 ± 2.1 vs. 1.9 ± 0.9 bpm, P < 0.05). Strong positive correlations were found between the SAS score and BPIA and HRIA both in the review and exam period. The smoking group and family hypertension group had higher anxiety score; meanwhile, their exam BPIAs and HRIAs were significantly higher than their corresponding group. The BP and HR increase in the review and exam period, anxiety is an important factor of BP and HR increase.

Avoidance perseveration during extinction training in Wistar-Kyoto rats: an interaction of innate vulnerability and stressor intensity

Given that avoidance is a core feature of anxiety disorders, Wistar-Kyoto (WKY) rats may be a good model of anxiety vulnerability for their hypersensitivity to stress and trait behavioral inhibition. Here, we examined the influence of strain and shock intensity on avoidance acquisition and extinction. Accordingly, we trained WKY and Sprague-Dawley (SD) rats in lever-press avoidance using either 1.0-mA or 2.0-mA foot-shock. After extinction, neuronal activation was visualized by c-Fos for overall activity and parvalbumin immunoreactivity for gamma-aminobutyric acid (GABA) neuron in brain areas linked to anxiety (medial prefrontal cortex and amygdala). Consistent with earlier work, WKY rats acquired lever-press avoidance faster and to a greater extent than SD rats. However, the intensity of foot shock did not differentially affect acquisition. Although there were no differences during extinction in SD rats, avoidance responses of WKY rats trained with the higher foot shock perseverated during extinction compared to those WKY rats trained with lower foot shock intensity or SD rats. WKY rats trained with 2.0-mA shock exhibited less GABAergic activation in the basolateral amygdala after extinction. These findings suggest that inhibitory modulation in amygdala is important to ensure successful extinction learning. Deficits in avoidance extinction secondary to lower GABAergic activation in baslolateral amygdala may contribute to anxiety vulnerability in this animal model of inhibited temperament.

Heroin reduces startle and cortisol response in opioid-maintained heroin-dependent patients

Heroin dependence (HD) is a chronic relapsing brain disorder characterized by a compulsion to seek and use heroin. Stress is seen as a key factor for heroin use. Methadone maintenance and the prescription of pharmaceutical heroin [diacetylmorphine (DAM)] are established treatments for HD in several countries. The present study examined whether DAM-maintained patients and methadone-maintained patients differ from healthy controls in startle reflex and cortisol levels. Fifty-seven participants, 19 of each group matched for age, sex and smoking status, completed a startle session which included the presentation of 24 bursts of white noise while eye-blink responses to startling noises were recorded. Salivary cortisol was collected three times after awakening, before, during and after the startle session. DAM was administered before the experiment, while methadone was administered afterwards. Both heroin-dependent patient groups exhibited significantly smaller startle responses than healthy controls (P < 0.05). Whereas the cortisol levels after awakening did not differ across the three groups, the experimental cortisol levels were significantly lower in DAM-maintained patients, who received their opioid before the experiment, than in methadone-maintained patients and healthy controls (P < 0.0001). Opioid maintenance treatment for HD is associated with reduced startle responses. Acute DAM administration may suppress cortisol levels, and DAM maintenance treatment may represent an effective alternative to methadone in stress-sensitive, heroin-dependent patients.

High salivary alpha-amylase levels in patients with schizophrenia: A pilot study

Previous studies have demonstrated the autonomic dysregulation in patients with schizophrenia using electrophysiological methods, such as electrodermal measures and heart rate analysis. Several theories have been proposed to explain the underlying mechanisms of schizophrenia and its autonomic function. Recently, the measurement of salivary alpha-amylase has been considered to be a useful tool for evaluating the sympathetic-adrenal-medullary (SAM) system. Psychosocial stress increases the release of salivary alpha-amylase. Although some studies have evaluated salivary alpha-amylase under psychosocial stress, no studies have demonstrated the change in the salivary alpha-amylase (sAA) activity level in schizophrenic patients. We examined the relationship between sAA level and psychiatric state in patients with schizophrenia (n=54) using a portable and rapid hand-held monitor to investigate sAA. The sAA activity in the patients was significantly higher than that in the control subjects (n=55) (p<0.01). The correlation between amylase level and psychiatric symptoms was highly significant (r=0.37, p<0.01). These findings indicate that higher increases in sAA may indicate severe psychiatric symptoms. These results indicate a predominant role of the sympathetic nervous system in the secretion of sAA, together with parasympathetic withdrawal, under psychosocial stress.

Multicenter, randomized, double-blind, active comparator and placebo-controlled trial of a corticotropin-releasing factor receptor-1 antagonist in generalized anxiety disorder

BACKGROUND

Antagonism of corticotropin-releasing factor (CRF) receptors has been hypothesized as a potential target for the development of novel anxiolytics. This study was designed to determine the safety and efficacy of pexacerfont, a selective CRF-1 receptor antagonist, in the treatment of generalized anxiety disorder (GAD).

METHOD

This was a multicenter, randomized, double-blind, placebo-controlled and active comparator trial. Two hundred and sixty patients were randomly assigned to pexacerfont 100 mg/day (after a 1 week loading dose of 300 mg/day), placebo or escitalopram 20 mg/day in a 2:2:1 ratio. The primary outcome was the mean change from baseline to end point (week 8) in the Hamilton Anxiety Scale total score.

RESULTS

Pexacerfont 100 mg/day did not separate from placebo on the primary outcome measure. The half-powered active comparator arm, escitalopram 20 mg/day, demonstrated efficacy with significant separation from placebo at weeks 1, 2, 3, 6, and 8 (P<.02). Response rates for pexacerfont, placebo, and escitalopram were 42, 42, and 53%, respectively. Genetic and psychometric rating scale data was obtained in 175 randomized subjects. There was a significant association between a single nucleotide polymorphism (SNP) of the gene encoding plexin A2 (PLXNA2-2016) with the HAM-A psychic subscale score for the entire cohort at baseline (FDR-adjusted P=.015).

CONCLUSIONS

Pexacerfont did not demonstrate efficacy compared to placebo for the treatment of GAD. Whether these findings are generalizable to this class of agents remains to be determined. Our preliminary genetic finding of an association between a SNP for the gene encoding plexin A2 and an anxiety phenotype in this study merits further exploration. The trial was registered at clinicaltrials.gov (NCT00481325) before enrollment.

The neurocircuitry of fear, stress, and anxiety disorders

Anxiety disorders are a significant problem in the community, and recent neuroimaging research has focused on determining the brain circuits that underlie them. Research on the neurocircuitry of anxiety disorders has its roots in the study of fear circuits in animal models and the study of brain responses to emotional stimuli in healthy humans. We review this research, as well as neuroimaging studies of anxiety disorders. In general, these studies have reported relatively heightened amygdala activation in response to disorder-relevant stimuli in post-traumatic stress disorder, social phobia, and specific phobia. Activation in the insular cortex appears to be heightened in many of the anxiety disorders. Unlike other anxiety disorders, post-traumatic stress disorder is associated with diminished responsivity in the rostral anterior cingulate cortex and adjacent ventral medial prefrontal cortex. Additional research will be needed to (1) clarify the exact role of each component of the fear circuitry in the anxiety disorders, (2) determine whether functional abnormalities identified in the anxiety disorders represent acquired signs of the disorders or vulnerability factors that increase the risk of developing them, (3) link the findings of functional neuroimaging studies with those of neurochemistry studies, and (4) use functional neuroimaging to predict treatment response and assess treatment-related changes in brain function.

Salivary alpha-amylase stability, diurnal profile and lack of response to the cold hand test in young women

Salivary cortisol measurement has proved useful for the non-invasive study of the hypothalamic-pituitary-adrenocortical axis, and salivary alpha-amylase has been suggested as a comparable marker for the sympathetic system. Despite some studies showing an increase in salivary alpha-amylase after challenges that stimulate the sympathetic nervous system, questions remain about interpretation. The aims of this study were to explore the stability of salivary alpha-amylase, its diurnal profile, response to the cold hand test, and correlation with cortisol. Salivary alpha-amylase was stable following 5 days at room temperature, and five freeze-thaw cycles. Its diurnal profile was opposite to that of cortisol. There was no salivary alpha-amylase response to the cold hand stress test, in the morning (11am) or afternoon (3pm), unlike cortisol which showed a response in the afternoon in the same samples. There was no correlation between salivary alpha-amylase and cortisol at any time. In conclusion, salivary alpha-amylase is stable to a range of conditions. Its diurnal pattern is compatible with sympathetic stimulation. Lack of response to the cold hand test suggests that secretion of salivary alpha-amylase is controlled by mechanisms more complex than sympathetic regulation alone.

Alcohol selectively reduces anxiety but not fear: startle response during unpredictable versus predictable threat

Recent theory and empirical research have suggested that fear and anxiety are distinct processes with separable neurobiological substrates. Furthermore, a laboratory procedure has been developed to manipulate fear versus anxiety independently via administration of predictable or unpredictable electric shock, respectively. Benzodiazepines appear to selectively reduce anxiety but not fear in this procedure. The primary aim of this experiment was to determine if alcohol produced a similar selective reduction in anxiety. Intoxicated (target blood alcohol concentration of .08%) and nonintoxicated participants viewed a series of colored squares separated by variable intertrial intervals (ITIs) in 3 conditions. In the predictable shock condition, shocks were administered contingently during every square. In the unpredictable shock condition, shocks were administered noncontingently during both squares and ITIs. In the no-shock condition, no shocks were administered at any time. Alcohol significantly reduced startle potentiation during cues signaling unpredictable but not predictable shock, consistent with the thesis that alcohol selectively reduces anxiety but not fear. In addition, alcohol's effect on startle potentiation during unpredictable shock was mediated by vigilance. This anxiolytic effect may clarify the nature of alcohol's reinforcing effects in social and problem drinkers.

Salivary alpha-amylase as a non-invasive biomarker for the sympathetic nervous system: current state of research

Development of new biomarkers is a constantly evolving field of research endeavor in psychoneuroendocrinology. Salivary biomarkers have received special attention since they are readily accessible and easily obtained. Salivary alpha-amylase (sAA) has been proposed as a sensitive biomarker for stress-related changes in the body that reflect the activity of the sympathetic nervous system (SNS), and a growing body of research is accumulating to support the validity and reliability of this parameter. However, questions remain to be answered before sAA can be accepted as an index of SNS activity. This review describes sAA as an emerging biomarker for stress and provides an overview of the current literature on stress-related alterations in sAA. It critically discusses how sAA might reflect changes in the autonomic nervous system. Finally, current and future fields for the application of sAA measurement are outlined.

CRF1 and CRF2 receptors are required for potentiated startle to contextual but not discrete cues

Corticotropin-releasing factor (CRF) peptides and their receptors have crucial roles in behavioral and endocrine responses to stress. Dysregulation of CRF signaling has been linked to post-traumatic stress disorder, which is associated with increased startle reactivity in response to threat. Thus, understanding the mechanisms underlying CRF regulation of startle may identify pathways involved in this disorder. Here, we tested the hypothesis that both CRF1 and CRF2 receptors contribute to fear-induced increases in startle. Startle responses of wild type (WT) and mice with null mutations (knockout, KO) for CRF1 or CRF2 receptor genes were measured immediately after footshock (shock sensitization) or in the presence of cues previously associated with footshock (ie fear-potentiated startle, FPS). WT mice exhibited robust increases in startle immediately after footshock, which was dependent upon contextual cues. This effect was completely absent in CRF1 KO mice, and significantly attenuated in CRF2 KO mice. In contrast, CRF1 and CRF2 KO mice exhibited normal potentiation of startle by discrete conditioned cues. Blockade of both receptors via CRF1 receptor antagonist treatment in CRF2 KO mice also had no effect on FPS. These results support an additive model of CRF1 and CRF2 receptor activation effects on potentiated startle. These data also indicate that both CRF receptor subtypes contribute to contextual fear but are not required for discrete cued fear effects on startle reactivity. Thus, we suggest that either CRF1 or CRF2 could contribute to the increased startle observed in anxiety disorders with CRF system abnormalities.

Endogenous cortisol suppression with metyrapone enhances acoustic startle in healthy subjects

Previous human studies have shown that excess cortisol sufficient to fully occupy central nervous system (CNS) corticosteroid receptors may reduce startle eye blink. The present study tested whether cortisol depletion and the resulting reduction in activity of CNS corticosteroid receptors has the opposite effect. In a single-blind, placebo-controlled, randomized study, eye blink EMG responses to 105 dB acoustic startle stimuli were assessed in 25 healthy subjects who received oral metyrapone (1500 mg) to suppress endogenous cortisol production, while 24 controls received oral placebo. As expected, metyrapone significantly reduced salivary cortisol, indicating effective endogenous cortisol suppression. Startle eye blink responses were significantly increased in the metyrapone group. Short-term habituation of the startle reflex was not different between groups. Our results suggest that startle is enhanced during depletion of cortisol. This effect may be mediated by CNS mechanisms controlling cortisol feedback.

Greater sustained anxiety but not phasic fear in women compared to men

Startle reflex studies in rodents indicate that female are more reactive than rats in experimental models of sustained anxiety but not in models of phasic fear (Toufexis, 2007). This study examined evidence for a similar effect in humans. Participants were exposed to three conditions, (1) predictable aversive shocks signaled by a cue, (2) unpredictable shocks, and (3) no shocks. Acoustic startle stimuli were delivered regularly across conditions. Phasic startle potential to the threat cue in the predictable condition was not affected by sex. In contrast, and consistent with basic research, the sustained increase in startle in the predictable and unpredictable conditions was greater in women compared to men. Animal studies suggest that such an effect may be mediated by the effects of sexual dimorphism in limbic structures, including the bed nucleus of the stria terminalis. However, psychosocial factors may also contribute to this effect.

Models and mechanisms of anxiety: evidence from startle studies

RATIONALE

Preclinical data indicates that threat stimuli elicit two classes of defensive behaviors, those that are associated with imminent danger and are characterized by flight or fight (fear), and those that are associated with temporally uncertain danger and are characterized by sustained apprehension and hypervigilance (anxiety).

OBJECTIVE

The objectives of the study are to (1) review evidence for a distinction between fear and anxiety in animal and human experimental models using the startle reflex as an operational measure of aversive states, (2) describe experimental models of anxiety, as opposed to fear, in humans, (3) examine the relevance of these models to clinical anxiety.

RESULTS

The distinction between phasic fear to imminent threat and sustained anxiety to temporally uncertain danger is suggested by psychopharmacological and behavioral evidence from ethological studies and can be traced back to distinct neuroanatomical systems, the amygdala and the bed nucleus of the stria terminalis. Experimental models of anxiety, not fear, are relevant to non-phobic anxiety disorders.

CONCLUSIONS

Progress in our understanding of normal and abnormal anxiety is critically dependent on our ability to model sustained aversive states to temporally uncertain threat.