The influence of Type A behavior pattern on the response to the panicogenic agent CCK-4

In vivo β-adrenergic receptor responsiveness: ethnic differences in the relationship with symptoms of depression and fatigue

BACKGROUND

Depressive symptoms and fatigue frequently overlap in clinical samples and the general population. The link of depressive symptoms and fatigue with increased risk of cardiovascular disease has been partly explained by shared biological mechanisms including sympathetic overactivity. Prolonged sympathetic overactivity downregulates the responsiveness of the β-adrenergic receptor (β-AR), a receptor that mediates several end-organ sympathetic responses.

PURPOSE

The authors studied whether depression and fatigue are related to reduced β-AR responsiveness within the human body (in vivo) in an ethnically diverse sample of African and Caucasian Americans.

METHODS

The chronotropic25 dose (CD25) was used to determine in vivo β-AR responsiveness in 93 healthy participants. Psychometric measures included the Center of Epidemiological Studies-Depression Scale and the Multidimensional Fatigue Symptom Inventory.

RESULTS

Hierarchical regression analyses (adjusted for age, gender, body mass index, blood pressure, smoking, and ethnicity) revealed that mental fatigue was significantly related to reduced β-AR responsiveness (i.e., higher CD25 values) in the whole sample. Moderation analyses indicated significant ethnicity × depression/fatigue interactions. Depressive symptoms, total fatigue, emotional fatigue, mental fatigue, and physical fatigue were related to reduced β-AR responsiveness in Caucasian American but not in African Americans.

CONCLUSIONS

Our findings suggest that symptoms of depression and fatigue are related to decreased in vivo β-AR responsiveness in Caucasian Americans. The lack of this association in African Americans highlights the importance for considering ethnicity as a potential moderator in research focusing on associations between psychological variables and cardiovascular function.

Benzodiazepines counteract rostral anterior cingulate cortex activation induced by cholecystokinin-tetrapeptide in humans

BACKGROUND

Benzodiazepines modulate γ-aminobutyric acid type A (GABA(A)) receptors throughout the brain. However, it is not fully understood which brain regions within anxiety-related brain circuits are really responsible for their anxiolytic effects and how these regions interact.

METHODS

We investigated whether the benzodiazepine alprazolam affects activity in distinct brain regions within anxiety-related circuits during an experimental anxiety paradigm by means of functional magnetic resonance imaging (fMRI). Panic symptoms were elicited by a bolus injection of the neuropeptide cholecystokinin-tetrapeptide (CCK-4) in 16 healthy male subjects in a double-blind, placebo-controlled design. Functional brain activation patterns were determined before and during the CCK-4-challenge without pretreatment and after treatment with either placebo or 1 mg alprazolam.

RESULTS

The CCK-4 induced anxiety and elicited widely distributed activation patterns in anxiety-related brain circuits, especially in the rostral anterior cingulate cortex (rACC), which was attenuated after alprazolam treatment. In contrast to placebo, alprazolam abolished the activation of the rACC after challenge with CCK-4 (p<.005, corrected for multiple comparisons) and increased functional connectivity between the rACC and other anxiety-related brain regions such as amygdala and prefrontal cortex. Moreover, the reduction in the CCK-4 induced activation of the rACC correlated with the anxiolytic effect of alprazolam (r(p) = .52; p = .04).

CONCLUSIONS

These findings put forward the rACC as a target for benzodiazepines and suggest that the CCK-4/fMRI paradigm might represent a human translational model for the investigation of anxiolytic drugs.

Association of in vivo β-adrenergic receptor sensitivity with inflammatory markers in healthy subjects

OBJECTIVE

Several stress-related states and conditions that are considered to involve sympathetic overactivation are accompanied by increased circulating levels of inflammatory immune markers. Prolonged sympathetic overactivity involves increased stimulation of the β-adrenergic receptor (β-AR). Although prior research suggests that one mechanism by which sympathetic stimulation may facilitate inflammation is via β-AR activation, little work has focused on the relationship between circulating inflammatory immune markers and β-AR function within the human body (in vivo). We examined whether decreased β-AR sensitivity, an indicator of prolonged β-adrenergic overactivation and a physiological component of chronic stress, is related to elevated levels of inflammatory immune markers.

METHODS

Ninety-three healthy participants aged 19 to 51 years underwent the chronotropic 25 dose isoproterenol test to determine in vivo β-AR function. Circulating levels of C-reactive protein, interleukin 6, and soluble tumor necrosis factor receptor 1 were determined.

RESULTS

β-AR sensitivity was lower in people with higher C-reactive protein concentrations (r = 0.326, p = .003). That relationship remained significant after controlling for sociodemographic and health variables such as age, sex, ethnicity, body mass index, mean arterial blood pressure, heart rate, leisure-time exercise, and smoking status. No significant relationship was found between chronotropic 25 dose and interleukin 6 or soluble tumor necrosis factor receptor 1.

CONCLUSIONS

This study demonstrates a link between in vivo β-adrenergic receptor function and selected circulating inflammatory markers (CRP) in humans. Future studies in specific disease states may be promising.

Functional neuroanatomy of CCK-4-induced panic attacks in healthy volunteers

Experimental panic induction with cholecystokinin tetrapeptide (CCK-4) is considered as a suitable model to investigate the pathophysiology of panic attacks. While only a few studies investigated the brain activation patterns following CCK-4, no data are available on the putative involvement of the amygdala in the CCK-4 elicited anxiety response. We studied the functional correlates of CCK-4-induced anxiety in healthy volunteers by means of functional magnetic resonance imaging (fMRI) and region of interest (ROI) analysis of the amygdala. Sixteen healthy volunteers underwent challenge with CCK-4 compared with placebo in a single-blind design. Functional brain activation patterns were determined for the CCK-4-challenge, the placebo response and anticipatory anxiety (AA). CCK-4-induced anxiety was accompanied by a strong and robust activation (random effects analysis, P < 0.00001, uncorrected for multiple testing) in the ventral anterior cingulate cortex (ACC), middle and superior frontal gyrus, precuneus, middle and superior temporal gyrus, occipital lobe, sublobar areas, cerebellum, and brainstem. In contrast, random effects group analysis for placebo and AA using the same level of significance generated no significant results. Using a more liberal level of significance, activations could be observed in some brain regions such as the dorsal part of the ACC during AA (random effects analysis, P < 0.005). Overall functional responses did not differ between panickers and nonpanickers. Only 5 of 11 subjects showed strong amygdala activation. However, ROI analysis pointed towards higher scores in fear items in these subjects. In conclusion, while overall brain activation patterns are not related to the subjective anxiety response to CCK-4, amygdala activation may be involved in the subjective perception of CCK-4-induced fear.

Impact of loudness dependency of auditory evoked potentials on the panic response to CCK-4

RATIONALE

Experimental panic induction with cholecystokinin-tetrapeptide (CCK-4) has been established as a model to study the pathophysiology of panic disorder. In line with the serotonin (5-HT)-hypothesis of panic disorder it has been suggested that the panicogenic effects of CCK-4 are mediated in part through the 5-HT system. The analysis of the loudness dependency of the auditory evoked potentials (LDAEP) is a valid non-invasive indicator of central serotonergic activity.

METHODS

We investigated the correlation between LDAEP and behavioral, cardiovascular and neuroendocrine panic responses to CCK-4in 77 healthy volunteers and explored whether differences in LDAEP paralleled subjective panic severity. Behavioral panic responses were measured with the panic symptom scale (PSS). Heart rate and ACTH/cortisol plasma concentrations were assessed concomitantly.

RESULTS

LDAEP did not differ between panickers and nonpanickers. Furthermore, LDAEP did not correlate with the behavioral panic response. However, a significant positive correlation between LDAEP and CCK-4 induced HPA-axis activation, which was uniform in panickers and nonpanickers, could be detected.

CONCLUSIONS

The psychological effects of CCK-4 rather are mediated by neurotransmitters others than the endogenous 5-HT system. However, the extent of the neuroendocrine activation related to the CCK-4 panic provocation was correlated with the LDAEP, thereby suggesting that central 5-HT mechanisms are involved in the HPA-axis activation during this challenge paradigm.

Does neuregulin-1 play a role in Type A behavior? The cardiovascular risk in young Finns study

Background

Neuregulin-1 proteins are related to physiological correlates of Type A in terms of cardiac reactivity. Furthermore, neuregulin-1 gene (NRG1) may play a role in cardiovascular disease such as atherosclerosis and coronary heart disease i.e. the suggested "outcomes" of Type A behavior. Therefore, NRG1 is hypothesized to be associated with Type A behavior.

Methods

The study examined whether Type A behavior pattern is associated with the single nucleotide polymorphism (SNP) SNP8NRG221533 of the NRG1. The subjects were 631 men and women participating in the population-based Cardiovascular Risk in Young Finns study in 1992 and 2001. Type A was self-assessed with the Framingham Type A Scale and reassessed nine years later.

Results

Type A was associated with NRG1 genotype. Carriers of genotype CC scored lower on Type A compared to the others.

Conclusion

Our study has pinpointed a SNP in NRG1 that predicts Type A behavior. As previous evidence suggests an association for NRG1 with beta-adrenergic stimulation, its role underlying Type A is discussed.

Evaluation of the CCK-4 model as a challenge paradigm in a population of healthy volunteers within a proof-of-concept study

RATIONALE

Experimental panic induction with cholecystokinin-tetrapeptide (CCK-4) has been established as a model to study the pathophysiology of panic disorder and might serve as a tool to asses the antipanic potential of novel anxiolytic compounds. However, assessment of CCK-4-induced panic does not follow consistent rules.

OBJECTIVES

To provide a basis for the use of the CCK-4 model in proof-of-concept studies, we investigated CCK-4-induced panic according to different criteria in 85 healthy volunteers who underwent a CCK-4 bolus injection.

METHODS

We assessed panicker/non-panicker ratios according to different panic criteria and explored whether differences in cardiovascular and neuroendocrine responses to CCK-4 paralleled subjective panic responses. Subjective panic responses were measured with the Acute Panic Inventory (API) and the Panic Symptom Scale (PSS). Heart rate, blood pressure, adrenocorticotropic hormone (ACTH) and cortisol were assessed concomitantly.

RESULTS

The API-derived panic rate was 10.6% higher than that derived from the PSS. CCK-4 induced an increase in heart rate, systolic blood pressure and ACTH/cortisol plasma levels, which did not differ between panickers and non-panickers.

CONCLUSIONS

The panic criterion applied appears to be of major importance for the panic rate achieved, whereas CCK-4-induced cardiovascular and hormonal alterations are not valuable as an objective "read out". The CCK-4 challenge might serve as a useful model to study putative anxiolytic effects of novel compounds during the early phase of drug development if the challenge procedure is carried out according to strictly comparable conditions.

Gender differences in anxiety-related traits in patients with panic disorder

This study examined gender differences in anxiety-related personality traits in patients with panic disorder with or without agoraphobia (PD+/-AG). Outpatients (101 total) with SCID confirmed PD+/-AG completed the Anxiety Sensitivity Index (ASI), the Trait form of the State-Trait Anxiety Inventory (STAI-T), the NEO Personality Inventory Revised (NEO PI-R), and the Retrospective Self-Report of Inhibition (RSRI) as part of their assessment. Significant gender differences were not detected for the total ASI scores. Females scored significantly higher than males on the Physical Concerns subscale of the ASI, whereas males scored significantly higher than women on the Social Concerns subscale. Women scored higher than men on the Extraversion scale of the NEO PI-R as well as on certain subscales of this domain. Although a significant gender difference was not detected on the Neuroticism subscale, men scored higher on the angry hostility and depression facets of this trait. Significant gender differences were not found for the STAI-T or the RSRI. These findings suggest that gender differences exist among patients with PD+/-AG in the feared consequences of anxiety symptoms as well as in the personality characteristics of extraversion.

Panic disorder in menopause: a case control study

OBJECTIVE

The course of panic disorder (PD) is often influenced by the different phases of the female reproductive cycle. The aim of this study is to assess PD in the climacteric stage and single out possible correlations between symptoms of PD and clinical and demographic variables in order to identify possible risk factors.

METHOD

Forty-five women between 40 and 60 years of age was assessed through the SCL-90, the SCID, a "Climacteric Symptoms Questionnaire" (CSQ) devised to evaluate psychological symptoms typically associated with menopause, the Kupperman Index for the analysis of climacteric symptoms, and plasma level of allopregnanolone (ALLO).

RESULTS

PD results in eight patients (18%). This group does not differ from the controls as far as socio-demographic data is concerned, but exhibits significantly higher values in the Kupperman Index, the SCL-90 total, and the CSQ. The plasma levels of ALLO correlate significantly inversely with the total of CSQ and, in any case, negatively with the other variables analysed.

CONCLUSIONS

PD may arise and worsen with menopause, in correlation with greater severity of the climacteric syndrome in its physical and psychological symptoms.