Endocrine and physiological changes during "spontaneous" panic attacks

Assessment of water safety competencies: Benefits and caveats of testing in open water

Drowning has been the cause of over 2.5 million preventable deaths in the past decade. Despite the fact that the majority of drownings occur in open water, assessment of water safety competency typically occurs in swimming pools. The assessment of water safety competency in open water environments brings with it a few difficulties, but also promises tremendous benefits. The aim of this position paper is to discuss the benefits and caveats of conducting assessments in open water environments as opposed to closed and controlled environments, and to provide recommendations for evidence-based practice. The first theoretical section discusses the effects of the environment and key variables (such as temperature and water movement) on various factors of assessment. These discussions are linked to the two perspectives of representative learning design (based on ecological dynamics) and information processing theory. The second section presents two pilot studies of relevance and provides practical implications for assessment of water safety competency. It seems that a combination of pool-based practice and open water education may be ideal in assessing aquatic skills competency. Assessment in open water presents clear benefits regarding validity, but often poses seemingly unsurmountable barriers, which providers may have reservations about in the absence of clear evidence. Hence this article provides a robust discussion about competency assessment and signals the practical importance of faithfully reproducing the environment in which skilled behavior is most relevant.

A Digital Therapeutic Intervention Delivering Biofeedback for Panic Attacks (PanicMechanic): Feasibility and Usability Study

BACKGROUND

Panic attacks (PAs) are an impairing mental health problem that affects >11% of adults every year. PAs are episodic, and it is difficult to predict when or where they may occur; thus, they are challenging to study and treat.

OBJECTIVE

The aim of this study is to present PanicMechanic, a novel mobile health app that captures heart rate-based data and delivers biofeedback during PAs.

METHODS

In our first analysis, we leveraged this tool to capture profiles of real-world PAs in the largest sample to date (148 attacks from 50 users). In our second analysis, we present the results from a pilot study to assess the usefulness of PanicMechanic as a PA intervention (N=18).

RESULTS

The results demonstrate that heart rate fluctuates by about 15 beats per minute during a PA and takes approximately 30 seconds to return to baseline from peak, cycling approximately 4 times during each attack despite the consistently decreasing anxiety ratings. Thoughts about health were the most common trigger and potential lifestyle contributors include slightly worse stress, sleep, and eating habits and slightly less exercise and drug or alcohol consumption than typical.

CONCLUSIONS

The pilot study revealed that PanicMechanic is largely feasible to use but would be made more so with modifications to the app and the integration of consumer wearables. Similarly, participants found PanicMechanic useful, with 94% (15/16) indicating that they would recommend PanicMechanic to others who have PAs. These results highlight the need for future development and a controlled trial to establish the effectiveness of this digital therapeutic for preventing PAs.

Peripheral Biomarkers in DSM-5 Anxiety Disorders: An Updated Overview

Anxiety disorders are prevalent and highly disabling mental disorders. In recent years, intensive efforts focused on the search for potential neuroimaging, genetic, and peripheral biomarkers in order to better understand the pathophysiology of these disorders, support their diagnosis, and characterize the treatment response. Of note, peripheral blood biomarkers, as surrogates for the central nervous system, represent a promising instrument to characterize psychiatric disorders, although their role has not been extensively applied to clinical practice. In this report, the state of the art on peripheral biomarkers of DSM-5 (Diagnostic and Statistical Manual of Mental Disorders, 5th edition) Anxiety Disorders is presented, in order to examine their role in the pathogenesis of these conditions and their potential application for diagnosis and treatment. Available data on the cerebrospinal fluid and blood-based biomarkers related to neurotransmitters, neuropeptides, the hypothalamic-pituitary-adrenal axis, neurotrophic factors, and the inflammation and immune system are reviewed. Despite the wide scientific literature and the promising results in the field, only a few of the proposed peripheral biomarkers have been defined as a specific diagnostic instrument or have been identified as a guide in the treatment response to DSM-5 Anxiety Disorders. Therefore, further investigations are needed to provide new biological insights into the pathogenesis of anxiety disorders, to help in their diagnosis, and to tailor a treatment.

Assessing Panic: Bridging the Gap Between Fundamental Mechanisms and Daily Life Experience

Panic disorder (PD) is one of the most common psychiatric disorders. Recurrent, unexpected panic attacks (PAs) are the primary symptom and strongly impact patients’ quality of life. Clinical manifestations are very heterogeneous between patients, emphasizing the need for a dimensional classification integrating various aspects of neurobiological and psychological circuits in line with the Research Domain Criteria (RDoC) proposed by the US National Institute of Mental Health. To go beyond data that can be collected in the daily clinical situation, experimental panic provocation is widely used, which has led to important insights into involved brain regions and systems. Genetic variants can determine the sensitivity to experimental models such as carbon dioxide (CO₂) exposure and can increase the risk to develop PD. Recent developments now allow to better assess the dynamic course of PAs outside the laboratory in patients’ natural environment. This can provide novel insights into the underlying mechanisms and the influence of environmental factors that can alter gene regulation by changing DNA methylation. In this mini review, we discuss assessment of PAs in the clinic, in the laboratory using CO₂ exposure, genetic associations, and the benefits of real-life assessment and epigenetic research.

Cortisol stress response in post-traumatic stress disorder, panic disorder, and major depressive disorder patients

BACKGROUND

Previous research has focussed extensively on the distinction of HPA-axis functioning between patient groups and healthy volunteers, with relatively little emphasis on a direct comparison of patient groups. The current study's aim was to analyse differences in the cortisol stress response as a function of primary diagnosis of panic disorder (PD), post-traumatic stress disorder (PTSD), and major depressive disorder (MDD).

METHODS

A total of n=30 PD (mean age±SD: 36.07±12.56), n=23 PTSD (41.22±10.17), n=18 MDD patients (39.00±14.93) and n=47 healthy control (HC) individuals (35.51±13.15) participated in this study. All the study participants were female. The Trier Social Stress Test (TSST) was used for reliable laboratory stress induction. Blood sampling accompanied the TSST for cortisol and ACTH assessment. Panic-related, PTSD-specific questionnaires and the Beck Depression Inventory II were handed out for the characterisation of the study groups. Repeated measure ANCOVAs were conducted to test for main effects of time or group and for interaction effects. Regression analyses were conducted to take comorbid depression into account.

RESULTS

26.7% of the PD patients, 43.5% of the PTSD patients, 72.2% of the MDD patients and 80.6% of the HC participants showed a cortisol stress response upon the TSST. ANCOVA revealed a cortisol hypo-responsiveness both in PD and PTSD patients, while no significant group differences were seen in the ACTH concentrations. Additional analyses showed no impact of comorbid depressiveness on the cortisol stress response. MDD patients did not differ in the hormonal stress response neither compared to the HC participants nor to the PD and PTSD patients.

CONCLUSION

Our main findings provide evidence of a dissociation between the cortisol and ACTH concentrations in response to the TSST in PTSD and in PD patients, independent of comorbid depression. Our results further support overall research findings of a cortisol hypo-responsiveness in PD patients. A hypo-response pattern was also seen in the PTSD patients agreeing with previous finding on the cortisol stress reactivity following TSST stress induction in these patients. Patients with a primary MDD diagnosis showed descriptively higher cortisol concentrations compared to the anxiety patients, and lower cortisol concentrations as the healthy individuals. The limitations of the study and implications for future studies will be discussed.

Biological markers for anxiety disorders, OCD and PTSD: A consensus statement. Part II: Neurochemistry, neurophysiology and neurocognition

OBJECTIVE

Biomarkers are defined as anatomical, biochemical or physiological traits that are specific to certain disorders or syndromes. The objective of this paper is to summarise the current knowledge of biomarkers for anxiety disorders, obsessive-compulsive disorder (OCD) and posttraumatic stress disorder (PTSD).

METHODS

Findings in biomarker research were reviewed by a task force of international experts in the field, consisting of members of the World Federation of Societies for Biological Psychiatry Task Force on Biological Markers and of the European College of Neuropsychopharmacology Anxiety Disorders Research Network.

RESULTS

The present article (Part II) summarises findings on potential biomarkers in neurochemistry (neurotransmitters such as serotonin, norepinephrine, dopamine or GABA, neuropeptides such as cholecystokinin, neurokinins, atrial natriuretic peptide, or oxytocin, the HPA axis, neurotrophic factors such as NGF and BDNF, immunology and CO2 hypersensitivity), neurophysiology (EEG, heart rate variability) and neurocognition. The accompanying paper (Part I) focuses on neuroimaging and genetics.

CONCLUSIONS

Although at present, none of the putative biomarkers is sufficient and specific as a diagnostic tool, an abundance of high quality research has accumulated that should improve our understanding of the neurobiological causes of anxiety disorders, OCD and PTSD.

Translational approach to studying panic disorder in rats: hits and misses

Panic disorder (PD) patients are specifically sensitive to 5–7% carbon dioxide. Another startling feature of clinical panic is the counterintuitive lack of increments in ‘stress hormones’. PD is also more frequent in women and highly comorbid with childhood separation anxiety (CSA). On the other hand, increasing evidence suggests that panic is mediated at dorsal periaqueductal grey matter (DPAG). In line with prior studies showing that DPAG-evoked panic-like behaviours are attenuated by clinically-effective treatments with panicolytics, we show here that (i) the DPAG harbors a hypoxia-sensitive alarm system, which is activated by hypoxia and potentiated by hypercapnia, (ii) the DPAG suffocation alarm system is inhibited by clinically-effective treatments with panicolytics, (iii) DPAG stimulations do not increase stress hormones in the absence of physical exertion, (iv) DPAG-evoked panic-like behaviours are facilitated in neonatally-isolated adult rats, a model of CSA, and (v) DPAG-evoked responses are enhanced in the late diestrus of female rats. Data are consistent with the DPAG mediation of both respiratory and non-respiratory types of panic attacks.

In a rat model of panic, corticotropin responses to dorsal periaqueductal gray stimulation depend on physical exertion

Panic disorder patients are exquisitely and specifically sensitive to hypercapnia. The demonstration that carbon dioxide provokes panic in fear-unresponsive amygdala-calcified Urbach-Wiethe patients emphasizes that panic is not fear nor does it require the activation of the amygdala. This is consonant with increasing evidence suggesting that panic is mediated caudally at midbrain's dorsal periaqueductal gray matter (DPAG). Another startling feature of the apparently spontaneous clinical panic is the counterintuitive lack of increments in corticotropin, cortisol and prolactin, generally considered 'stress hormones'. Here we show that the stress hormones are not changed during DPAG-evoked panic when escape is prevented by stimulating the rat in a small compartment. Neither did the corticotropin increase when physical exertion was statistically adjusted to the same degree as non-stimulated controls, as measured by lactate plasma levels. Conversely, neuroendocrine responses to foot-shocks were independent from muscular effort. Data are consonant with DPAG mediation of panic attacks.

Who is stressed? A pilot study of salivary cortisol and alpha-amylase concentrations in agoraphobic patients and their novice therapists undergoing in vivo exposure

In cognitive behavioural therapy of phobic anxiety, in vivo exposure is considered as an effective treatment strategy. Apparently, it involves the experience of stress and anxiety in patients. Given the therapist's role during exposure sessions, it is conceivable that the performance is also accompanied with the experience of stress in therapists, especially when unversed in conducting psychotherapy. Studies confirmed that cognitive behavioural therapists tend to avoid therapist-guided in vivo exposure. The objective of this study was the simultaneous investigation of therapist's and patient's stress response during in vivo exposure. Therefore, 23 agoraphobic patients and their 23 treating therapists in training provided five saliva samples during an in vivo exposure and five samples during an ordinary therapy session. Before and during exposure session, subjective evaluations of stress and anxiety were assessed. Results suggested that therapists reported similar levels of perceived stress as patients before exposure. Both groups displayed significantly elevated salivary cortisol (sC) levels during exposure compared to the control session and a trend for alterations in salivary alpha-amylase (sAA) activity was found. Therapists reached peak concentrations of sC before start of the intervention followed by a decline during exposure, while patients displayed peak levels of cortisol secretion after 60 min of exposure. In vivo exposure seems to be a demanding intervention not only for the patient, but also for therapists in training. However, it was also demonstrated that physiological and subjective stress rather decrease during the intervention and that both groups rated exposure to be substantially successful. Based on the presented results, another potential factor contributing to the under-usage of exposure treatment is conceivable and needs to be addressed in future research.

Pseudopheochromocytoma induced by anxiolytic withdrawal

Background

Symptomatic paroxysmal hypertension without significantly elevated catecholamine concentrations and with no evidence of an underlying adrenal tumor is known as pseudopheochromocytoma.

Methods

We describe the case of a female patient with paroxysmal hypertensive crises accompanied by headache, vertigo, tachycardia, nausea and altered mental status. Previously, she was treated for a longer period with alprazolam due to panic disorder. Causes of secondary hypertension were excluded. Neurological triggers (intracranial tumor, cerebral vascular lesions, hemorrhage, and epilepsy) could not be detected.

Results

Setting of the diagnosis of pseudopheochromocytoma treatment was initiated with alpha- and beta-blockers resulting in reduced frequency of symptoms. Alprazolam was restarted at a daily dose of 1 mg. The patient’s clinical condition improved rapidly and the dosage of alpha- and beta-blockers could be decreased.

Conclusions

We conclude that the withdrawal of an anxiolytic therapeutic regimen may generate sympathetic overdrive resulting in life-threatening paroxysmal malignant hypertension and secondary encephalopathy. We emphasize that pseudopheochromocytoma can be diagnosed only after exclusion of the secondary causes of hypertension. We highlight the importance of a psychopharmacological approach to this clinical entity.

Experimental public speaking: contributions to the understanding of the serotonergic modulation of fear

Public speaking is widely used as a model of experimental fear and anxiety. This review aimed to evaluate the effects of pharmacological challenges on public speaking responses and their implications for the understanding of the neurobiology of normal and pathological anxiety, specifically panic disorder. We also describe methodological features of experimental paradigms using public speaking as an inducer of fear and stress. Public speaking is a potent stressor that can provoke significant subjective and physiological responses. However, variations in the manners in which public speaking is modelled can lead to different responses that need to be considered when interpreting the results. Results from pharmacological studies with healthy volunteers submitted to simulated public speaking tests have similarities with the pharmacological responses of panic patients observed in clinical practice and panic patients differ from controls in the response to the public speaking test. These data are compatible with the Deakin and Graeff hypothesis that serotonin inhibits fear, as accessed by public speaking tasks, and that this inhibition is likely related to the actions of serotonin in the dorsal periaqueductal grey matter.

Changes in neuroactive steroid secretion associated with CO2-induced panic attacks in normal individuals

Neuroactive steroids modulate anxiety in experimental animals and possibly in humans. The secretion of these compounds has been found to be altered in panic disorder (PD), with such alterations having been suggested to be a possible cause or effect of panic symptomatology. Panic-like attacks can be induced in healthy individuals by administration of panicogenic agents or by physical procedures, and we have now measured the plasma concentrations of neuroactive steroids in such individuals before, during, and after panicogenic inhalation of CO2 in order to investigate whether abnormalities of neuroactive steroid secretion might contribute to the pathogenesis of PD. Fifty-nine psychologically and physically healthy subjects, including 42 women (11 in the follicular phase of the menstrual cycle, 14 in the luteal phase, and 17 taking contraceptive pills) and 17 men, who experienced a panic-like attack on previous exposure to 7% CO2 were again administered 7% CO2 for 20min. Thirty-three of these individuals (responders) again experienced a panic-like attack, whereas the remaining 26 subjects did not (nonresponders). All subjects were examined with the VAS-A and PSL-III-R scales for anxiety and panic symptomatology before and after CO2 inhalation. The plasma concentrations of progesterone, 3α,5α-tetrahydroprogesterone (3α,5α-THPROG=allopregnanolone), 3α,5α-tetrahydrodesoxycorticosterone (3α,5α-THDOC), dehydroepiandrosterone (DHEA), and cortisol were measured 15min and immediately before the onset of CO2 administration as well as immediately, 10, 30, and 50min after the end of CO2 inhalation. Neuroactive steroids were measured in the laboratory of Prof. Biggio in Cagliari, Sardinia, Italy. Neurosteroid levels did not change significantly in both responders and nonresponders before, during, or after CO2 inhalation. These data suggest that neuroactive steroid concentrations before, during, or after CO2 inhalation do not seem to correlate with panic symptomatology during panic-like attacks in subjects not affected by PD, and they therefore do not support the notion that abnormalities in neuroactive steroid secretion are either a cause or an effect of such attacks.

Gender effect on the relationship between stress hormones and panic-agoraphobic spectrum dimensions in healthy subjects

INTRODUCTION

Alterations of the hypothalamic-pituitary-adrenal (HPA) axis and of its peripheral indices have been reported in both normal and pathological anxiety with controversial findings. The aim of the present study was to investigate the possible correlations between serum cortisol and dehydroepiandrosterone-sulfate (DHEA-S) levels and DHEA-S/cortisol ratio, and panic-agoraphobic spectrum dimensions in a sample of healthy subjects.

METHODS

Forty-two healthy subjects of both sexes, with no current or lifetime psychiatric disorders, were assessed by means of the Structured Clinical Interview for DSM-IV (SCID-I/P) and the so-called Panic Agoraphobic Spectrum-Self Report lifetime version (PAS-SR).

RESULTS

Significant, negative correlations were found between cortisol levels and the total score of the separation sensitivity, panic-like symptoms, and medication/substance sensitivity PAS-SR domains. The PAS-SR total and the panic-like symptoms domain scores were positively related to the DHEAS/cortisol ratio. When the sample was divided in women and men, these correlations were present in women only.

DISCUSSION

These findings, while indicating the presence of significant relationships between panic-agoraphobic traits and some indices of HPA axis functioning in healthy women, would suggest this as one of the factors explaining the greater vulnerability of women to cross the line between normal and pathological anxiety.

CONCLUSIONS

Further studies are needed to explore gender differences in the relationships between HPA axis alterations and the panic-agoraphobic spectrum dimensions.

Childhood stressful events, HPA axis and anxiety disorders

Anxiety disorders are among the most common of all mental disorders and their pathogenesis is a major topic in psychiatry, both for prevention and treatment. Early stressful life events and alterations of hypothalamic pituitary adrenal (HPA) axis function seem to have a significant role in the onset of anxiety. Existing data appear to support the mediating effect of the HPA axis between childhood traumata and posttraumatic stress disorder. Findings on the HPA axis activity at baseline and after stimuli in panic disordered patients are inconclusive, even if stressful life events may have a triggering function in the development of this disorder. Data on the relationship between stress, HPA axis functioning and obsessive-compulsive disorder (OCD) are scarce and discordant, but an increased activity of the HPA axis is reported in OCD patients. Moreover, normal basal cortisol levels and hyper-responsiveness of the adrenal cortex during a psychosocial stressor are observed in social phobics. Finally, abnormal HPA axis activity has also been observed in generalized anxiety disordered patients. While several hypothesis have attempted to explain these findings over time, currently the most widely accepted theory is that early stressful life events may provoke alterations of the stress response and thus of the HPA axis, that can endure during adulthood, predisposing individuals to develop psychopathology. All theories are reviewed and the authors conclude that childhood life events and HPA abnormalities may be specifically and transnosographically related to all anxiety disorders, as well as, more broadly, to all psychiatric disorders.

Do unexpected panic attacks occur spontaneously?

BACKGROUND

Spontaneous or unexpected panic attacks, per definition, occur "out of the blue," in the absence of cues or triggers. Accordingly, physiological arousal or instability should occur at the onset of, or during, the attack, but not preceding it. To test this hypothesis, we examined if points of significant autonomic changes preceded the onset of spontaneous panic attacks.

METHODS

Forty-three panic disorder patients underwent repeated 24-hour ambulatory monitoring. Thirteen natural panic attacks were recorded during 1960 hours of monitoring. Minute-by-minute epochs beginning 60 minutes before and continuing to 10 minutes after the onset of individual attacks were examined for respiration, heart rate, and skin conductance level. Measures were controlled for physical activity and vocalization and compared with time matched control periods within the same person.

RESULTS

Significant patterns of instability across a number of autonomic and respiratory variables were detected as early as 47 minutes before panic onset. The final minutes before onset were dominated by respiratory changes, with significant decreases in tidal volume followed by abrupt carbon dioxide partial pressure increases. Panic attack onset was characterized by heart rate and tidal volume increases and a drop in carbon dioxide partial pressure. Symptom report was consistent with these changes. Skin conductance levels were generally elevated in the hour before, and during, the attacks. Changes in the matched control periods were largely absent.

CONCLUSIONS

Significant autonomic irregularities preceded the onset of attacks that were reported as abrupt and unexpected. The findings invite reconsideration of the current diagnostic distinction between uncued and cued panic attacks.

Stress hormones during flooding therapy and their relationship to therapy outcome in patients with panic disorder and agoraphobia

In spite of excessive fear during a panic attack, studies have found no or little evidence for an activation of cortisol during natural panic attacks. Whether this phenomenon is related to psychopathology or outcome of psychotherapy is unknown. In this study, 10 patients with panic disorder and agoraphobia were treated with cognitive behavioural therapy including 3 in-vivo exposures (flooding) to individual phobic situations. Before, during and after exposure, the level of subjective fear was assessed and blood was collected simultaneously. Cortisol and ACTH were analysed from plasma. Ten matched healthy control subjects went through the same procedure. Fear and stress hormones during exposure were compared in patients and controls as well as related to therapy outcome at the end of therapy and 2 follow-ups in patients. Results showed that the concentrations of cortisol and ACTH did not significantly increase during exposure. Patients' cortisol concentrations were higher than those of controls at baseline and during exposure, while ACTH concentrations were comparable before and during exposure, and even lower than those of controls at recovery. Cortisol concentrations were moderately but consistently correlated to therapy outcome, i.e. patients with least cortisol release during exposure profited least from therapy. The study showed that a lack of stimulation of the HPA system at repeated confrontation with the phobic situation was related to therapeutic outcome. Mechanisms of action via the influence of cortisol on extinction learning or the inhibition of central excitatory neurotransmission are conceivable.

Increased plasma corticosterone levels after periaqueductal gray stimulation-induced escape reaction or panic attacks in rats

The hypothalamo-pituitary-adrenal (HPA) axis is involved in stress, depression and anxiety. Controversy exists on HPA axis activation during panic attacks (PAs). We examined whether the HPA axis is involved in the escape or panic-like response in an animal model of PAs induced by electrical stimulation of the dorsolateral periaqueductal gray (dlPAG) in rats. Additionally, rats were also treated with chronic administration of buspirone (BUSP) and escitalopram (ESCIT), respectively; and they were stimulated in the open-field arena for panic-like reaction. Levels of stress hormone corticosterone were measured following 30 min after escape or panic condition. Our results demonstrated that the levels of plasma corticosterone were significantly increased after the induction of escape or panic-like response in comparison with the sham animals. The levels of corticosterone were significantly decreased in the dlPAG stimulated groups after rats were treated chronically with the ESCIT but not the BUSP as compared to the saline treated animals. Importantly, the increase of corticosterone level after escape or panic-like response was paralleled by an increase of neuronal activation of c-Fos in both the parvocellular and magnocellular paraventricular nucleus of the hypothalamus. Moreover, the c-Fos data also showed a decrease in the number of positive cells particularly for the ESCIT as well as the BUSP in comparison with the saline stimulated animals. In conclusion, the present study clearly demonstrated that PA or escape response activates the HPA axis and it remains difficult to anticipate the mechanism underlying HPA axis during PAs and its relationship with 5-HT drugs.

Examining face and construct validity of a noninvasive model of panic disorder in Lister-hooded rats

RATIONALE

Increasing evidence suggests that defensive escape behavior in Lister-hooded (LH) rats induced by ultrasound application may be an animal model of panic disorder.

OBJECTIVE

The objectives of this study were to further explore the face and construct validity of ultrasound-induced escape behavior by characterizing the autonomic and neuroendocrine response to ultrasound, and to examine the underlying neuronal structures by comparing the effects of the anxiolytic with panicolytic properties, diazepam, with a preclinical anxiolytic without panicolytic-like activity, the NOP agonist Ro 64-6198.

MATERIALS AND METHODS

LH rats were implanted with telemetry transmitters to monitor heart rate and core body temperature before, during, and after ultrasound application. Blood samples were taken after ultrasound application for corticosterone analysis. Ultrasound-induced c-Fos expression was measured in different periaqueductal gray (PAG) and amygdala subregions after treatment with diazepam or Ro 64-6198.

RESULTS

Ultrasound application increased heart rate and body temperature, but did not alter plasma corticosterone levels. Ultrasound application increased c-Fos expression in the dorsal and dorsolateral PAG (dPAG, dlPAG) and amygdaloid subregions. Diazepam, but not Ro 64-6198, reduced c-Fos expression in the dPAG/dlPAG, while Ro 64-6198, but not diazepam, reduced c-Fos expression in the central amygdala.

CONCLUSIONS

Similar to human panic attacks, ultrasound application to LH rats activated the autonomic, but not the neuroendocrine, stress system. Also, like in humans, the current data confirm and extend that the dPAG/dlPAG plays a key role in ultrasound-induced escape behavior. These observations suggest that ultrasound-induced escape behaviors in LH rats have face and construct validity for panic disorders.

Natriuretic peptides and panic disorder: therapeutic prospects

Natriuretic peptides differentially modulate endocrine and behavioral stress responses in preclinical and human studies. While atrial natriuretic peptide inhibits the hypothalamic-pituitary-adrenocortical axis, C-type natriuretic peptide exerts stimulatory activity. In rodents, atrial natriuretic peptide reduces anxiety, whereas C-type natriuretic peptide has anxiogenic effects (mediated via corticotropin-releasing hormone). Patients with panic disorder show lower basal ANP plasma levels but a more pronounced release during experimentally induced panic attacks compared with controls. This could explain the absent pituitary-adrenocortical activation during panic anxiety and its paroxysmal nature. Furthermore, the effects of the panicogen cholecystokinin-tetrapeptide are attenuated by ANP pretreatment in panic patients, while C-type natriuretic peptide demonstrates anxiogenic action in healthy humans. Atrial natriuretic peptide agonists and C-type natriuretic peptide antagonists may have potential as a new class of antipanic and anxiolytic psychotherapeutic medication.

A striking pattern of cortisol non-responsiveness to psychosocial stress in patients with panic disorder with concurrent normal cortisol awakening responses

BACKGROUND

Subtle and inconsistent differences in hypothalamic-pituitary-adrenal (HPA) axis activity have been reported for patients with panic disorder. While these patients show little or no alterations in basal ACTH and cortisol levels, it has been hypothesized that HPA hyperresponsivity was a trait in panic patients when exposed to novel and uncontrollable stimulation.

METHODS

Thirty-four patients (23 females, mean age 35 yrs) diagnosed with panic disorder were compared to 34 healthy controls matched for age, gender, smoking status, and use of oral contraceptives. Both groups were exposed twice to a potent laboratory stress protocol, the Trier Social Stress Test (TSST) on consecutive days. Free salivary cortisol levels and heart rate responses were repeatedly measured before and following the TSST. In addition, the cortisol awakening response (CAR) was assessed to further investigate HPA reactivity in PD patients.

RESULTS

While the TSST induced similar heart rate stress responses in both groups, cortisol responses were clearly absent in the panic patients with normal responses in the controls (F(1.96, 66)=20.16; p<0.001). No differences in basal cortisol levels were observed in the extended baseline period. The same cortisol stress non-response patterns were observed when patients with/without comorbid depression, or with/without psychotropic medication were compared. In contrast to their non-response to the psychosocial stressor, panic patients showed a significant CAR.

CONCLUSION

These findings provide strong evidence to suggest that PD patients present with a striking lack of cortisol responsivity to acute uncontrollable psychosocial stress under laboratory conditions. This unresponsiveness of the HPA axis appears to be rather specific, since a normal CAR in the morning could be documented in these patients. Thus, the present results do not support the hypothesis that PD patients show a trait HPA hyperresponsiveness to novel and uncontrollable stimulation. In contrast, the data provide support for a hyporesponsive HPA axis under emotional stress in PD patients.

HPA axis activity in patients with panic disorder: review and synthesis of four studies

Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis may play a role in panic disorder. HPA studies in patients with panic disorder, however, have produced inconsistent results. Seeking to understand the inconsistencies, we reexamined endocrine data from four studies of patients with panic disorder, in light of animal data highlighting the salience of novelty, control, and social support to HPA axis activity. Patients with panic disorder were studied (1) at rest over a full circadian cycle, (2) before and after activation by a panicogenic respiratory stimulant (doxapram) that does not directly stimulate the HPA axis, and (3) before and after a cholecystokinin B (CCK-B) agonist that is panicogenic and does directly stimulate the HPA axis. Patients with panic disorder had elevated overnight cortisol levels, which correlated with sleep disruption. ACTH and cortisol levels were higher in a challenge paradigm (doxapram) than in a resting state study, and paradigm-related ACTH secretion was exaggerated in patients with panic disorder. Panic itself could be elicited without HPA axis activation. Patients with panic disorder showed an exaggerated ACTH response to pentagastrin stimulation, but this response was normalized by prior exposure to the experimental context or psychological preparation to reduce novelty and enhance sense of control. Novelty is one of a number of contextual cues known from animal work to activate the HPA axis. The HPA axis abnormalities seen in patients with panic disorder in the four experiments reviewed here might all be due to exaggerated HPA axis reactivity to novelty cues. Most of the published panic/HPA literature is consistent with the hypothesis that HPA axis dysregulation in panic is due to hypersensitivity to contextual cues. This hypothesis requires experimental testing.

Psychophysiological mechanisms in panic disorder: a correlative analysis of noradrenaline spillover, neuronal noradrenaline reuptake, power spectral analysis of heart rate variability, and psychological variables

BACKGROUND

The risk of adverse clinical cardiac events is increased in patients with panic disorder (PD). We evaluated possible mechanistic links between PD and heart disease. We estimated cardiac vagal activity from heart rate variability (HRV) measurements and quantified sympathetic nervous system (SNS) activity using plasma noradrenaline tracer kinetics methodology.

METHODS

Thirty-nine people with PD and 39 age- and gender-matched healthy volunteers were studied. In 19 participants with PD, both HRV and plasma noradrenaline kinetics were tested; in 20 with PD and 20 healthy volunteers, HRV measurements only were made, whereas in 19 healthy volunteers, noradrenaline kinetics only was tested. All panic disorder participants completed psychological measures of anxiety sensitivity and state and trait anxiety; healthy volunteers in whom HRV was measured also provided psychological measures.

RESULTS

Sympathetic nervous tone in the heart, based on rates of cardiac noradrenaline spillover, was normal in PD. Noradrenaline and adrenaline plasma clearance and plasma tritiated noradrenaline and adrenaline extraction in transit through the heart, all dependent on the noradrenaline transporter (NET), were reduced in PD. Psychometric testing linked inhibition of anger to this deficit in NET functioning. Anxiety sensitivity was specifically associated with impaired cardiac NET. High- and low-frequency heart rate spectral power was unrelated to all plasma noradrenaline kinetics measurements.

CONCLUSION

Defective neuronal reuptake of noradrenaline, by augmenting the sympathetic neural signal in the heart, might have a dual effect, sensitizing the heart such as to lead to symptom development (and thus perhaps causing panic disorder) and, second, potentially contributing to adverse cardiac events in established PD.

Does the panic attack activate the hypothalamic-pituitary-adrenal axis?

A bibliographic search has been performed in MEDLINE using cortisol and panic as key-words, occurring in the title and/or in the abstract. Human studies were selected, with no time limit. The following publications were excluded: reviewarticles, case reports, panic attacks in disorders other than panic disorder, and studies on changes that occurred in-between panic attacks. The results showed that real-life panic attacks as well as those induced by selective panicogenic agents such as lactate and carbon dioxide do not activate the hypothalamicpituitary- adrenal (HPA) axis. Agonists of the colecystokinin receptor B, such as the colecystokinin-4 peptide and pentagastrin, increase stress hormones regardless of the occurrence of a panic attack and thus, seem to activate the HPA axis directly. The benzodiazepine antagonist flumazenil does not increase stress hormones, but this agent does not reliably induce panic attacks. Pharmacological agents that increased anxiety in both normal subjects and panic patients raised stress hormone levels; among them are the alpha2-adrenergic antagonist yohimbine, the serotonergic agents 1-(m-chlorophenyl) piperazine (mCPP) and fenfluramine, as well as the psychostimulant agent caffeine. Therefore, the panic attack does not seem to activate the HPAaxis, in contrast to anticipatory anxiety.

CO2 challenge results in hypothalamic-pituitary-adrenal activation in healthy volunteers

The 35% CO(2) challenge is known to induce symptoms of a panic attack both in panic disorder (PD) patients and healthy volunteers. Although the challenge applies more to PD patients, studies in healthy volunteers provide the opportunity to isolate the physical symptoms from the disorder and to focus on the direct effect from the challenge on stress responsive systems. One of the main stress responsive systems is the hypothalamic-pituitary-adrenal (HPA) axis. It remains unclear whether panic symptoms are accompanied by HPA axis activation. Differences in design have hampered any comparison between studies. For example, both serum and salivary cortisol have been used to provide an index of HPA axis activation. Furthermore, indications for central HPA axis disturbance have been suggested. The current study aimed to study the HPA axis response following the induction of panic symptoms in healthy volunteers, both at the pituitary level and at the adrenal level. Furthermore, both serum and salivary cortisol levels were determined. Subjective feelings of anxiety and, correspondingly, cortisol and ACTH levels, were found to be significantly increased following the 35% CO(2) challenge. Cortisol and ACTH responses to CO(2) were also associated. A significant cortisol increase was observed in both serum and saliva samples, although these were more pronounced when considering the free fraction serum values. We conclude that the induction of panic symptoms results in HPA axis activation, both at the pituitary and adrenal level. The question remains as to whether positive responders to the 35% CO(2) inhalation (more specifically PD patients) show a more pronounced HPA axis response.

Anxiety and salivary cortisol in symptomatic and nonsymptomatic panic patients and healthy volunteers performing simulated public speaking

Anxiety and salivary cortisol were measured in subjects performing simulated public speaking (SPS), a procedure that has been neurobiologically related to panic disorder. The subjects were divided into three groups: 18 symptomatic panic patients, 16 nonsymptomatic, drug-treated panic patients, and 17 healthy controls. In the experimental session, subjective anxiety (Visual Analogue Mood Scale) and the total score of the Bodily Symptom Scale (BSS) were higher in symptomatic patients than in controls, with nonsymptomatic patients in between. Measures of cortisol taken at home showed that the level was higher at 9:00 h than at 23:00 h in every group, indicating a normal circadian regulation of the hypothalamic-pituitary-adrenal (HPA) axis in panic patients. Also in every group, the level of cortisol was high at the beginning of the experimental session and decreased after 70 min. This fall parallels the decrease in anxiety and BSS ratings, and appears to reflect habituation of initial, anticipatory anxiety. Preparation and performance of speech raised anxiety and BSS scores to the initial levels, but failed to increase cortisol measured over 60 min, starting at the end of the speech. Therefore, SPS does not seem to activate the HPA axis, as reported in panic attacks.

Anxious and depressive disorders and their comorbidity: effect on central nervous system noradrenergic function

BACKGROUND

Although comorbidity of anxiety with depression is common, investigations of physiologic abnormalities related specifically to comorbidity are rare. This study examined relationships of DSM-IV-defined depression, anxiety, and their comorbidity to noradrenergic function measured by blunting of the growth hormone (GH) response to the alpha2 adrenoreceptor agonist (and imidazoline receptor agent) clonidine and by blood pressure and symptom responses.

METHODS

Fifteen subjects with pure social anxiety or panic disorder, 15 with pure major depression, and 18 with both depression and anxiety were compared with healthy control subjects matched for age and gender. Other factors known to affect GH (weight, menstrual status, prior antidepressant, or other drug exposure) were controlled.

RESULTS

Anxiety produced GH blunting, but depression was associated with normal GH responses. The comorbid state did not affect results beyond the impact of anxiety. Preclonidine stress-related GH elevations were observed, to the greatest degree in anxious subjects. Relevant symptom, but not blood pressure, changes were significantly associated with blunting.

CONCLUSIONS

With use of pure depression and anxiety groups and careful control of other factors known to affect GH, these results demonstrate central nervous system noradrenergic dysfunction in anxiety disorders. In contrast to less rigorously controlled studies, noradrenergic function in depression was normal.

Effect of comorbid anxiety disorders on the hypothalamic-pituitary-adrenal axis response to a social stressor in major depression

BACKGROUND

Major depressive disorder (MDD) is often complicated by anxiety symptoms, and anxiety disorders occur in approximately 30% of mood cases. This study examined the influence of anxiety comorbidity on the hypothalamic-pituitary-adrenal (HPA) axis response to stress in patients with MDD.

METHODS

Untreated subjects with pure MDD (n = 15), MDD with comorbid anxiety disorders (n = 18), and pure anxiety disorders (n = 15) were recruited by advertising. Age- and gender-matched control subjects were recruited for each subject with a psychiatric diagnosis (n = 48). All subjects underwent a social stressor, the Trier Social Stress Test (TSST), and blood was collected for adrenocorticotropic hormone (ACTH) and cortisol assay.

RESULTS

When all depressed patients (n = 33) were compared with their matched control subjects (n = 33), they showed a significantly greater ACTH response to the stressor; however, this exaggerated ACTH response was exclusively due to the depressed group with comorbid anxiety disorders. A similar but nonsignificant effect was observed in the cortisol response. Subjects with pure mood or pure anxiety disorders showed normal ACTH and cortisol responses to the TSST. All patient groups showed similar levels of TSST-induced anxiety.

CONCLUSIONS

Comorbid anxiety disorders might play a role in the increased activation of the HPA axis observed in patients with major depression.

Serotonin, the periaqueductal gray and panic

This article reviews experimental evidence and theoretical constructs that implicate serotonin (5-HT) modulation of defensive behavior within the midbrain periaqueductal gray in panic disorder (PD). Evidence with conflict tests in experimental animals indicates that 5-HT enhances anxiety, whereas results with aversive stimulation of the dorsal periaqueductal gray point to an anxiolytic role of 5-HT. To solve this contradiction, it has been suggested that the emotional states determined by the two types of animal model are different. Conflict tests would generate conditioned anxiety, whereas periaqueductal gray stimulation would produce unconditioned fear, as evoked by proximal threat. Clinically, the former would be related to generalized anxiety while the latter to PD. Thus, 5-HT is supposed to facilitate anxiety, but to inhibit panic. This hypothesis has been tested in the animal model of anxiety and panic named the elevated T-maze, in two procedures of human experimental anxiety applied to healthy volunteers or panic patients, and in CO2-induced panic attacks. Overall, the obtained results have shown that drugs that enhance 5-HT function increase different indexes of anxiety, but decrease indexes of panic. Drugs that impair 5-HT function have the opposite effects. Thus, so far the predictions derived from the above hypothesis have been fulfilled.

[Experimental provocation of panic attacks as a human experimental model for anxiety]

Diagnostic symptom provocation has a long tradition in medicine. In psychiatry, symptom provocation studies are used to study the pathophysiology and treatment of disorders. Sudden and unexpected panic attacks have a characteristic course and a typical pattern of somatic, cognitive, emotional, and behavioral symptoms. Beginning with the study of Pitts and McClure, who described the panicogenic activity of sodium lactate, the experimental induction of panic attacks with different challenges has been used to characterize the neurobiology of anxiety. Furthermore, experimentally induced panic attacks can be used to study possible new treatment approaches. The anxiolytic activity of atrial natriuretic peptide suggests that modulation of natriuretic peptide receptors with nonpeptidergic ligands may be a new treatment approach. Experimentally induced panic attacks are a tool to characterize the neurobiology of anxiety and panic and may be used to develop new treatment approaches.

Salivary cortisol response during exposure treatment in driving phobics

OBJECTIVE

Extensive research on the hypothalamic-pituitary-adrenal (HPA) axis response to stress has not clarified whether that axis is activated by phobic anxiety. We addressed this issue by measuring cortisol in situational phobics during exposure treatment.

METHODS

Salivary cortisol was measured in 11 driving phobics before and during three exposure sessions involving driving on crowded limited-access highways and compared with levels measured in 13 healthy controls before and during two sessions of driving on the same highways. For each subject, data collected in the same time period on a comparison nondriving day served as an individual baseline from which cortisol response scores were calculated.

RESULTS

Cortisol levels of driving phobics and controls did not differ on the comparison day. Phobics also had normal cortisol response scores on awakening on the mornings of the exposures but these were already increased 1 hour before coming to the treatment sessions. Phobics had significantly greater cortisol response scores during driving exposure and during quiet sitting periods before and afterward. These greater responses generally paralleled increases in self-reported anxiety. At the first exposure session, effect sizes for differences in cortisol response scores between the two groups were large. Initial exposure to driving in the first session evoked the largest responses.

CONCLUSION

The data demonstrate that the HPA axis can be strongly activated by exposure to, and anticipation of, a phobic situation.

Neurosteroid secretion in panic disorder

Evidence that neurosteroids have anxiolytic effects in animal models of anxiety has suggested that alterations of neurosteroid secretion might be implicated in the pathogenetic mechanisms of anxiety disorders in humans. In 25 female patients with panic disorder (PD) and 11 healthy female controls, we measured plasma concentrations of progesterone (PROG), pregnenolone (PREG), allopregnanolone (3alpha,5alpha-tetrahydroprogesterone=3alpha,5alpha-THPROG), dehydroepiandrosterone (DHEA) and tetrahydrodeoxycorticosterone (3alpha,5alpha-THDOC) during a drug-free month and during the following month of paroxetine therapy. The neurosteroids were measured during the early follicular phase, the mid-luteal phase and the premenstrual phase of both months (days 7, 22 and 27 from the beginning of the cycle). Significantly higher levels in patients than controls were found in PROG during the mid-luteal phase of both months, PREG in the premenstrual phase in the drug-free month, 3alpha,5alpha-THPROG during the follicular phase of the drug-free month and during the premenstrual phase of the therapy month, and 3alpha,5alpha-THDOC during the premenstrual phases of both months. DHEA levels did not differ in patients and controls. These results suggest that neurosteroids in PD are hypersecreted, possibly as an attempt to counteract the anxiogenic underlying hyperactivity of the hypothalamo-pituitary-adrenal axis and to improve a reduced GABA(A) receptor sensitivity.

Influence of the serotonin antagonist, metergoline, on the anxiogenic effects of carbon dioxide, and on heart rate and neuroendocrine measures, in healthy volunteers

The mechanism of action of carbon dioxide (CO(2)) angiogenesis is unknown; only recently have possible serotonergic (5-HT) influences begun to be studied. In separate double-blind challenges 1 week apart, 14 healthy volunteers received two vital capacity inhalations each of 35% CO(2) and of air, once after a single capsule of placebo and once after a single capsule containing 4 mg of the 5-HT antagonist metergoline in a randomized crossover design. The inhalations were repeated 1 and 2 days after the ingestion of capsules, to investigate possible delayed effects of metergoline, and possible tolerance to repeated CO(2) after placebo. We observed increased anxiety, and a trend for increased plasma noradrenaline (NA), after CO(2). CO(2) anxiogenesis was significantly enhanced by metergoline. Heart rate increased after both gas mixtures following metergoline administration. Plasma prolactin levels were lower after metergoline. Responses to CO(2) did not differ between the day of placebo administration and the two subsequent days; on the days following metergoline administration there were almost no delayed effects. We hypothesize that 5-HT may function as an inhibitor of CO(2) anxiogenesis, and that this is opposed by the 5-HT antagonist, metergoline. Absence of tolerance after repeated CO(2) argues against psychological explanations of tolerance after other panicogens. Copyright 2001 John Wiley & Sons, Ltd.

Autonomic dysregulation in panic disorder and in post-traumatic stress disorder: application of power spectrum analysis of heart rate variability at rest and in response to recollection of trauma or panic attacks

Power spectral analysis (PSA) of heart rate variability (HRV) offers reliable assessment of cardiovascular autonomic responses, providing a 'window' onto the interaction of peripheral sympathetic and parasympathetic tone. Alterations in HRV are associated with various physiological and pathophysiological processes, and may contribute to morbidity and mortality. Previous studies of posttraumatic stress disorder (PTSD) found lower resting HRV in patients compared to controls, suggesting increased sympathetic and decreased parasympathetic tone. This article describes the analysis of HRV at rest and after psychological stress in panic disorder (PD) patients, in an enlarged sample of PTSD patients, and in healthy control subjects. Standardized heart rate (HR) analysis was carried out in 14 PTSD patients, 11 PD patients and 25 matched controls. ECG recordings were made while subjects were resting ('rest 1'), while recalling the trauma implicated in PTSD, or the circumstances of a severe panic attack, as appropriate ('recall'), and again while resting ('rest 2'). Controls were asked to recall a stressful life event during recall. While both patient groups had elevated HR and low frequency (LF) components of HRV at baseline (suggesting increased sympathetic activity), PTSD patients, unlike PD patients and controls, failed to respond to the recall stress with increases in HR and LF. HRV analysis demonstrates significant differences in autonomic regulation of PTSD and PD patients compared to each other and to control subjects. HRV analysis may augment biochemical studies of peripheral measures in these disorders.

Diurnal variation of cortisol in panic disorder

In patients with panic disorder (n=23), daytime salivary cortisol levels were determined in 2-h spans on 3 consecutive days and compared with 23 age- and sex-matched healthy controls. Additionally, nocturnal urinary free cortisol levels were measured. Daytime salivary cortisol levels were numerically higher in the patients, although the difference did not reach statistical significance. In a subgroup of 14 patients with higher illness severity (as expressed by a score >/=22 on the Panic and Agoraphobia Scale), salivary cortisol levels were significantly higher than in the controls. Mean nocturnal urinary cortisol levels were significantly higher in the whole group of patients and also in the more severely ill subgroup when compared with controls. Cortisol elevations seem to be more pronounced during the night and occurred mainly in more severely ill panic patients.

Temporal lobe volume in panic disorder--a quantitative magnetic resonance imaging study

Although previous studies have used magnetic resonance imaging (MRI) to demonstrate qualitative abnormalities of the temporal lobes in patients with panic disorder, no study to date has applied quantitative volumetric methods to evaluate brain changes in panic disorder. The purpose of this study was to measure the volume of the temporal lobe and the hippocampus in patients with panic disorder and healthy control subjects using quantitative MRI measures. The volume of the temporal lobe, hippocampus and whole brain was measured in 13 patients with panic disorder and 14 healthy subjects. The mean volume of the left and right temporal lobes was significantly smaller in panic disorder compared to healthy subjects (16770+/-909 mm(3) vs. 18343+/-1740 mm(3)). This result was significant after controlling for differences in whole brain volume. There was no significant difference in volume of the hippocampus between patients and control subjects. These findings are consistent with smaller temporal lobe volume in panic disorder despite normal hippocampal volume.

Panic induced by carbon dioxide inhalation and lack of hypothalamic-pituitary-adrenal axis activation

It has been hypothesized that spontaneous panic is distinct from anticipatory anxiety, which activates the hypothalamic-pituitary-adrenal (HPA) axis. Panic attacks characterized by prominent respiratory symptoms, such as those induced by sodium lactate, are not associated with increases in cortisol. We examined blood cortisol responses to CO2-induced panic. Cortisol levels did not increase and actually decreased significantly in 10 panicking subjects with panic disorder. No reductions were noted after 20 min of CO2 inhalation in either eight normal comparison subjects or six non-panicking panic disorder patients. These results lend support to the hypothesis that the pathophysiological mechanism underlying CO2-induced panic is different from that underlying general or anticipatory anxiety.

Behavioral, neuroendocrine, and cardiovascular response to flumazenil: no evidence for an altered benzodiazepine receptor sensitivity in panic disorder

BACKGROUND

Flumazenil is a benzodiazepine receptor antagonist thought to be panicogenic in patients with panic disorder but not in control subjects. The present study was undertaken to compare the effects of flumazenil in patients with panic disorder and those in healthy control subjects, and also to determine whether panic disorder is characterized by a hypothesized shift in the benzodiazepine receptor "set-point" and a differential response to flumazenil.

METHODS

Eight patients with panic disorder and 8 matched control subjects were given infusions of saline and flumazenil in randomized order. Psychopathological changes, cardiovascular parameters, together with adrenocorticotropic hormone (ACTH) and cortisol secretion were recorded.

RESULTS

Patient and control subjects responded to flumazenil uniformly; there was no evidence for an anxiogenic activity of flumazenil in control subjects or panic disorder patients. ACTH and cortisol levels were also not differentially influenced by flumazenil or panic disorder diagnosis. Heart rate and systolic blood pressure in both groups were slightly but significantly reduced by flumazenil compared to saline.

CONCLUSIONS

These findings do not support the view that panic disorder patients and control subjects respond differentially to flumazenil or that the suggested shift in the benzodiazepine receptor "set-point," which leads to an inverse agonistic activity of flumazenil, characterizes panic disorder.

Forebrain pathways mediating stress-induced hormone secretion

Exposure to hostile conditions initiates the secretion of several hormones, including corticosterone/cortisol, catecholamines, prolactin, oxytocin, and renin, as part of the survival mechanism. Such conditions are often referred to as "stressors" and can be divided into three categories: external conditions resulting in pain or discomfort, internal homeostatic disturbances, and learned or associative responses to the perception of impending endangerment, pain, or discomfort ("psychological stress"). The hormones released in response to stressors often are referred to as "stress hormones" and their secretion is regulated by neural circuits impinging on hypothalamic neurons that are the final output toward the pituitary gland and the kidneys. This review discusses the forebrain circuits that mediate the neuroendocrine responses to stressors and emphasizes those neuroendocrine systems that have previously received little attention as stress-sensitive hormones: renin, oxytocin, and prolactin. Anxiolytic drugs of the benzodiazepine class and other drugs that affect catecholamine, GABAA, histamine, and serotonin receptors alter the neuroendocrine stress response. The effects of these drugs are discussed in relation to their effects on forebrain neural circuits that regulate stress hormone secretion. For psychological stressors such as conditioned fear, the neural circuits mediating neuroendocrine responses involve cortical activation of the basolateral amygdala, which in turn activates the central nucleus of the amygdala. The central amygdala then activates hypothalamic neurons directly, indirectly through the bed nucleus of the stria terminalis, and/or possibly via circuits involving brainstem serotonergic and catecholaminergic neurons. The renin response to psychological stress, in contrast to those of ACTH and prolactin, is not mediated by the bed nucleus of the stria terminalis and is not suppressed by benzodiazepine anxiolytics. Stressors that challenge cardiovascular homeostasis, such as hemorrhage, trigger a pattern of neuroendocrine responses that is similar to that observed in response to psychological stressors. These neuroendocrine responses are initiated by afferent signals from cardiovascular receptors which synapse in the medulla oblongata and are relayed either directly or indirectly to hypothalamic neurons controlling ACTH, prolactin, and oxytocin release. In contrast, forebrain pathways may not be essential for the renin response to hemorrhage. Thus current evidence indicates that although a diverse group of stressors initiate similar increases in ACTH, renin, prolactin, and oxytocin, the specific neural circuits and neurotransmitter systems involved in these responses differ for each neuroendocrine system and stressor category.

Decreased plasma cortisol level during alprazolam treatment of panic disorder: a case report

1. Changes in the plasma cortisol level were reported in a male patient with panic disorder during the period of low-dose alprazolam treatment (mean 0.62 +/- 0.15 mg/day) compared with during the period of high-dose period (mean 1.08 +/- 0.28 mg/day). 2. The plasma cortisol level was significantly higher in the low-dose period (mean 13.90 +/- 3.35 micrograms/ml) than in the high-dose period (mean 9.06 +/- 2.75 micrograms/ml) although, paradoxically, the panic attack frequency was significantly lower in the low-dose period (mean 1.35 +/- 0.29/day) than in the high-dose period (mean 2.09 +/- 0.66/day). 3. Thus, the decreased plasma cortisol level during alprazolam treatment of panic disorder was suggested to be caused not by symptom alleviation due to alprazolam but by alprazolam administration itself.

The relationship between plasma MHPG and NE: employing regression models in estimating centrally derived MHPG and peripheral NE turnover rate in panic disorder

Studies investigating the role of the noradrenergic system in the pathophysiology of anxiety have focused on measuring plasma 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) levels. Fewer studies have examined norepinephrine levels. Basal plasma norepinephrine and free MHPG levels were simultaneously measured in 33 normal controls and 20 panic disorder (PD) patients. Norepinephrine levels were similar in patients and controls, but MHPG levels were significantly lower in patients (13.34 +/- 3.22 vs 18.37 +/- 4.49 pmol ml-1, p < 0.0001). Norepinephrine correlated significantly with plasma MHPG levels in controls (r = 0.538, p < 0.0001) and patients (r = 0.645, p < 0.002). Patients had a trend toward a lower y-intercept than controls, suggesting a lower contribution by the CNS to MHPG pool plasma levels (9.18 vs 12.51, p < 0.08). Norepinephrine turnover rate was similar in patients and controls. We propose that the dysregulation in the noradrenergic system in PD may be akin to animal studies of acute-on-top-of-chronic stress paradigms, whereby chronic stress results in normal or decreased basal NE turnover and sensitized responses to recurrent stresses.

Atrial natriuretic hormone in lactate-induced panic attacks: mode of release and endocrine and pathophysiological consequences

Previous studies have shown unequivocally a lack of pituitary-adrenocortical stress hormone activation during lactate-induced panic attacks despite considerable psychopathological alterations, signs of arousal and several vegetative symptoms regularly occurring during stressful conditions. To study the possible inhibitory action of atrial natriuretic hormone (ANH) on adrenocorticotrophic hormone (ACTH) and cortisol release in humans, 10 patients with panic disorder (DSM-III-R) received sodium lactate and placebo (0.9% saline) infusions and ten healthy comparison subjects additionally received a 2.5% saline infusion and the response of ANH, vasopressin, ACTH, cortisol, and several biochemical and physiological cardiovascular parameters were measured. In comparison to placebo, lactate infusion led to enhanced ANH levels in both non-panicking comparison subjects and panickers. Importantly, panickers showed significantly lower baseline levels of ANH than comparison subjects followed by a faster release. No significant concomitant changes in vasopressin, ACTH, and cortisol were observed. During lactate infusion, heart rate was accelerated considerably in the two groups; in contrast, the reduction of pCO2 indicated an enhanced ventilation only in panickers. The pattern of ANH release cannot be attributed simply to either the volume load administered, the cardiac activation or an osmotic effect since neither 0.9 nor 2.5% saline resulted in comparable effects. Additional central nervous mechanisms must be considered for the increased ANH concentrations in lactate-induced panic attacks. We propose that the release of ANH is an intrinsic mechanism contributing to the apparent unresponsiveness of the pituitary-adrenocortical system in lactate-induced panic attacks. In addition, we surmise that ANH may also play a role in the yet unknown mechanisms for termination of panic attacks, e.g. either by inhibitory actions on the locus coeruleus or by bronchiorelaxation and consecutive decatastrophization.

Hormonal response during a fenfluramine-associated panic attack

Secretion curves for prolactin, cortisol, TSH, and GH from a 37-year old woman with dysthymia and panic disorder with agoraphobia were determined one day prior to (day I), and during a panic attack (day II) associated with an oral dose of 60 mg dl-fenfluramine, a drug known to increase anticipatory anxiety. The increased cortisol secretion observed is discussed in relation to the hormonal correlates of anxiety and the possible role of depression, dl-fenfluramine, and serotonergic receptor sensitivity.

Behavioral, sympathetic and adrenocortical responses to yohimbine in panic disorder patients and normal controls

Yohimbine, an alpha 2 adrenoreceptor antagonist, enhances norepinephrine (NE) release and increases sympathetic activity. We examined the behavioral, peripheral sympathetic and adrenocortical responses to oral yohimbine in seven healthy controls and 11 patients diagnosed with agoraphobia with panic attacks (PD). Patients did not differ in baseline cardiovascular or neuroendocrine measures from controls despite significantly higher baseline anxiety ratings. Placebo caused no changes in baseline-corrected behavioral, cardiovascular or neurochemical responses in either group. Yohimbine induced a panic episode in six PD patients, but no controls. PD patients had significantly higher severity scores of autonomic anxiety symptoms. Yohimbine significantly raised systolic blood pressure (F = 3.07, P < 0.03), plasma NE levels (F = 12.11, P < 0.00) and cortisol levels (F = 4.82, P < 0.02), but had no effect on epinephrine levels. NE responses were similar in both groups, but patients had higher cortisol responses to yohimbine than controls (F = 7.14, P < 0.01). The correlational pattern between behavioral ratings and neuroendocrine responses in patients was opposite to that observed in controls. Despite similar increases in plasma NE levels between PD patients and healthy controls, PD patients had greater anxiogenic, cardiovascular and cortisol responses to yohimbine. Enhanced post-synaptic adrenoreceptor sensitivity may explain the noradrenergic dysregulation found in panic disorder.

Physiological, biochemical and subjective parameters in anxiety patients with panic disorder during stress exposure as compared with healthy controls

Physiological (heart rate, blood pressure, electrodermal activity), biochemical (epinephrine, norepinephrine, cortisol) and subjective parameters (self-rating score) of 33 patients with panic disorder (diagnoses according to DSM-III-R) before, during and after stress exposure were compared with those of healthy controls. As stressors a video containing frightening scenes (FS), mental arithmetic (MA), a video documenting a patient suffering from a panic attack (PA) and an improvised speech (IS) were applied. We found significantly higher baseline levels of electrodermal activity (EDA) and norepinephrine (NE) secretion and a subsequent further increase during stress exposure in panic disorder patients as compared with normal controls. The most potent stressors during the trial proved to be mental arithmetics and improvised speech, which was evident in both groups. The situation panic attack video appeared to be a "panic disorder patient-specific" stressor; here we noticed the most pronounced reactions in the patient group. Panic disorder patients had significantly higher self-rating scores of the parameters panicky feelings, anxiety and nervousness at the beginning and throughout the investigation. We conclude that panic disorder patients have a higher degree of activation compared with normal controls, which is evident regarding levels of electrodermal activity and norepinephrine secretion. Furthermore, the panic attack video appears to be a panic disorder patient-specific stressor.

Platelet alpha 2-adrenoreceptors, catecholamines, hemodynamic variables, and anxiety in panic patients and their asymptomatic relatives

The objectives of this study were to a) replicate our prior finding of a decreased number (Bmax) of platelet alpha 2-adrenoreceptors in panic disorder, b) determine if binding is also decreased in asymptomatic first-degree relatives of panic patients (known to be at increased risk for developing panic), and c) evaluate the effect of treatment on the presumptive decrease in binding (i.e., is the decrease a state or a trait marker for panic?). Panic patients had clonidine and yohimbine platelet-binding assays, symptom ratings, and measurement of lying and standing plasma epinephrine, norepinephrine, systolic and diastolic blood pressure, and heart rate before treatment, after approximately 2 months of medication (fluoxetine, tricyclics, or alprazolam) and/or cognitive behavioral treatment, and after symptom remission while drug free; normal subjects had determinations of the same measures at approximately the same time intervals. Relatives of both groups had one determination only of all measures. Tritiated clonidine binding was decreased and lying heart rate was increased in patients before treatment. Magnitude of binding decrease was correlated with symptom severity and standing norepinephrine. No binding abnormality was seen in first-degree relatives of patients. Treatment increased clonidine binding in patients. Both patients and relatives of patients showed significantly increased standing plasma norepinephrine in comparison to controls. There is a state-related decrease in binding, associated with symptom severity and norepinephrine, in panic disorder. Abnormal reactivity of norepinephrine to standing might be a marker for increased likelihood of panic development in individuals at risk.

Noradrenergic mechanisms in stress and anxiety: II. Clinical studies

Studies in animals have shown a relationship between alterations in noradrenergic brain system function and behaviors of anxiety and fear. These findings have generated the hypothesis that the symptoms seen in patients with anxiety disorders may be related to alterations in noradrenergic function. A number of clinical studies have tested this hypothesis, utilizing measures of catecholaminergic function such as heart rate and blood pressure, measurement of norepinephrine and its metabolites in urine and plasma and adrenergic receptor binding in platelets, as well as pharmacological challenge to the noradrenergic system. Acute stressors, such as public speaking, have been associated with an increase in heart rate, blood pressure, and norepinephrine and its metabolites in urine and plasma. Findings in patients with panic disorder at baseline related to heart rate, blood pressure, baseline norepinephrine and its metabolites, and platelet adrenergic receptors have been mixed, while the most consistent findings have been blunted growth hormone response to clonidine and increased 3-methoxy-4-hydroxy-phenylethylene-glucol (MHPG) and anxiety following stimulation of the noradrenergic system with yohimbine. Baseline measures of noradrenergic function in patients with posttraumatic stress disorder (PTSD) have also been mixed, while an increased heart, blood pressure and norepinephrine response to traumatic reminders, as well as increased behavioral (as well as different brain metabolic) response to yohimbine, have been found in PTSD. There are fewer studies of noradrenergic function in the other anxiety disorders, and the findings there have not been consistent. These studies provide evidence for increased noradrenergic responsiveness in panic disorder and PTSD, although there does not appear to be an alteration in baseline noradrenergic function in these patients.