Sensitivity to CCK-4 in women with and without premenstrual dysphoric disorder (PMDD) during their follicular and luteal phases

Effect of BI 1358894 on Cholecystokinin-Tetrapeptide (CCK-4)-Induced Anxiety, Panic Symptoms, and Stress Biomarkers: A Phase I Randomized Trial in Healthy Males

INTRODUCTION

Depression, anxiety, and/or panic disorder are often comorbid and have a complex etiology mediated through the same neuronal network. Cholecystokinin-tetrapeptide (CCK-4), a synthetic analog of the endogenous neuropeptide cholecystokinin (CCK), is thought to be implicated in this network. The CCK-4 challenge model is an accepted method of investigating the pathophysiology of panic and has been shown to mediate neuronal activation via the transient receptor potential canonical (TRPC) ion channels.

OBJECTIVES

This study aimed to assess the pharmacodynamic effects of BI 1358894, a small-molecule inhibitor of TRPC ion channel members 4 and 5 (TRPC4/5), on CCK-4-induced anxiety/panic-like symptoms and evaluate circuit engagement.

METHODS

Twenty healthy male CCK-4-sensitive volunteers entered a Phase I, double blind, randomized, two-way cross-over, single dose, placebo-controlled trial. Randomization was to oral BI 1358894 100 mg in the fed state followed by oral placebo in the fed state, or vice versa. Treatments were administered 5 h prior to intravenous CCK-4 50 µg. The primary endpoint was maximum change from baseline of the Panic Symptom Scale (PSS) sum intensity score after CCK-4 injection. Further endpoints included the emotional faces visual analog score (EVAS), the Spielberger State-Trait Anxiety Inventory (STAI), plasma adrenocorticotropic hormone (ACTH), and serum cortisol values. The safety and tolerability of BI 1358894 was assessed based on a number of parameters including occurrence of adverse events (AEs). All pharmacodynamic, pharmacokinetic, and safety endpoints were analyzed using descriptive statistics.

RESULTS

Single oral doses of BI 1358894 were generally well tolerated by the healthy male volunteers included in this study. Adjusted mean maximum change from baseline in PSS sum intensity score was 24.4 % lower in volunteers treated with BI 1358894 versus placebo, while adjusted mean maximum change from baseline of EVAS was reduced by 19.2 % (BI 1358894 vs placebo). The STAI total score before CCK-4 injection was similar in both groups (placebo: 25.1; BI 1358894: 24.3). Relative to placebo, BI 1358894 reduced CCK-4-induced mean maximum plasma ACTH and serum cortisol values by 58.6 % and 27.3 %, respectively. Investigator-assessed drug-related AEs were reported for 13/20 participants (65.0 %). There were no serious or severe AEs, AEs of special interest, AEs leading to discontinuation of trial medication, or deaths.

CONCLUSIONS

Overall, BI 1358894 reduced psychological and physiological responses to CCK-4 compared with placebo, as measured by PSS, subjective EVAS and objectively measured stress biomarkers. BI 1358894 had a positive safety profile, and single oral doses were well tolerated by the healthy volunteers. This trial (NCT03904576/1402-0005) was registered on Clinicaltrials.gov on 05.04.19.

Are the Effects of Malnutrition on the Gut Microbiota–Brain Axis the Core Pathologies of Anorexia Nervosa?

Anorexia nervosa (AN) is a disabling, costly, and potentially deadly illness. Treatment failure and relapse after treatment are common. Several studies have indicated the involvement of the gut microbiota–brain (GMB) axis. This narrative review hypothesizes that AN is driven by malnutrition-induced alterations in the GMB axis in susceptible individuals. According to this hypothesis, initial weight loss can voluntarily occur through dieting or be caused by somatic or psychiatric diseases. Malnutrition-induced alterations in gut microbiota may increase the sensitivity to anxiety-inducing gastrointestinal hormones released during meals, one of which is cholecystokinin (CCK). The experimental injection of a high dose of its CCK-4 fragment in healthy individuals induces panic attacks, probably via the stimulation of CCK receptors in the brain. Such meal-related anxiety attacks may take part in developing the clinical picture of AN. Malnutrition may also cause increased effects from appetite-reducing hormones that also seem to have roles in AN development and maintenance. The scientific background, including clinical, microbiological, and biochemical factors, of AN is discussed. A novel model for AN development and maintenance in accordance with this hypothesis is presented. Suggestions for future research are also provided.

A systematic review and network meta-analysis of carbon dioxide provocation in psychiatric disorders

BACKGROUND

False suffocation alarm hypothesis has been widely used to explain carbon dioxide hypersensitivity in panic disorder (PD). However, hypersensitivity to carbon dioxide has been observed in other psychiatric disorders. We explored the specificity of carbon dioxide inhalation as a panic provocation test among psychiatric disorders via network meta-analysis.

METHODS

A systematic literature search on PubMed, EMBASE, and PsycNET was performed to acquire the studies using the carbon dioxide provocation test in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and checklists. Odds ratios (OR) for a panic attack (PA) induced by the carbon dioxide inhalation tests were extracted from each of the original studies and were pooled using the random-effects model.

RESULTS

Network meta-analysis on a pool of 2181 participants from 41 studies was used to compare the efficacy of carbon dioxide provocation tests among psychiatric disorders. The network meta-analysis showed that the odds for PA in response to carbon dioxide inhalation are higher in patients with PD, premenstrual dysphoric syndrome (PMDD), and social anxiety disorder (SAD) than healthy controls (HC). The odds for PA were not significantly different among patients with generalized anxiety disorder (GAD), obsessive-compulsive disorder (OCD), major depressive disorder (MDD), and healthy controls (HC).

CONCLUSIONS

The vulnerability to the carbon dioxide provocation test is not limited to PD. The specificity of the test for PD is questionable, as individuals suffering from PMDD and SAD are also significantly more responsive to carbon dioxide inhalation compared to HC, OCD, MDD, and GAD. There may be shared underpinning biological mechanisms between PD, PMDD, and SAD.

Cholecystokinin-Mediated Neuromodulation of Anxiety and Schizophrenia: A "Dimmer-Switch" Hypothesis

Cholecystokinin (CCK), the most abundant brain neuropeptide, is involved in relevant behavioral functions like memory, cognition, and reward through its interactions with the opioid and dopaminergic systems in the limbic system. CCK excites neurons by binding two receptors, CCK1 and CCK2, expressed at low and high levels in the brain, respectively. Historically, CCK2 receptors have been related to the induction of panic attacks in humans. Disturbances in brain CCK expression also underlie the physiopathology of schizophrenia, which is attributed to the modulation by CCK1 receptors of the dopamine flux in the basal striatum. Despite this evidence, neither CCK2 receptor antagonists ameliorate human anxiety nor CCK agonists have consistently shown neuroleptic effects in clinical trials. A neglected aspect of the function of brain CCK is its neuromodulatory role in mental disorders. Interestingly, CCK is expressed in pivotal inhibitory interneurons that sculpt cortical dynamics and the flux of nerve impulses across corticolimbic areas and the excitatory projections to mesolimbic pathways. At the basal striatum, CCK modulates the excitability of glutamate, the release of inhibitory GABA, and the discharge of dopamine. Here we focus on how CCK may reduce rather than trigger anxiety by regulating its cognitive component. Adequate levels of CCK release in the basal striatum may control the interplay between cognition and reward circuitry, which is critical in schizophrenia. Hence, it is proposed that disturbances in the excitatory/ inhibitory interplay modulated by CCK may contribute to the imbalanced interaction between corticolimbic and mesolimbic neural activity found in anxiety and schizophrenia.

Copeptin in CCK-4-induced panic in healthy man: Sexual dimorphisms in secretion pattern and panic response, but no correlation of copeptin with panic symptoms

Copeptin, the C-terminal part of the hypothalamic arginine vaspopressin (AVP) precursor, closely mirrors the production of AVP and was proposed as an easily measured novel marker of the individual stress level in man. First data in male volunteers proposed copeptin as a potential endocrine surrogate marker of cholecystokinin-tetrapeptide (CCK-4)-induced panic. We tried to replicate these pilot data and to extend them to the other sex. 46 healthy human subjects (29 men, 17 women) were given an intravenous bolus of 50 μg CCK-4. Basal and stimulated plasma copeptin was measured and panic symptoms were assessed using the Acute Panic Inventory (API). Basal copeptin was significantly lower in women vs. men, while men showed a significantly higher CCK-4-induced increase of copeptin. In contrast, female subjects displayed a signifcantly higher increase of API ratings by CCK-4. No significant correlations of panic symptoms and copeptin release induced by CCK-4 could be found, neither in man, nor in women, nor in the total sample. A sexual dimorphism in copeptin secretion and in panic response was demonstrated. Prior unexpected findings of copeptin release as an objective read-out of panic could not be replicated. The role of the vasopressinergic system in panic anxiety needs further study in panic patients and in healthy man, using also other panic provocation paradigms.

The influence of the menstrual cycle on reactivity to a CO2 challenge among women with and without premenstrual symptoms

Clinically significant premenstrual symptoms (PMS) is conceptualized as a depressive disorder in DSM-5, however, it may share pathophysiological processes with anxiety- and fear-related disorders. Specifically, women with PMS panic at higher rates during biological challenge procedures. It is unclear if this increased interoceptive sensitivity is a general vulnerability or specific to the premenstrual phase. The current study examined the role of menstrual cycle phase on reactivity to a CO₂ challenge among women with (n = 11) and without (n = 26) clinically significant PMS (N = 37). During the late follicular phase (days 6-12), women with and without PMS responded similarly to the CO₂ challenge, whereas during the premenstrual phase (within 5 days before menses), women with PMS reported significantly more intense panic symptoms in response to the challenge than women without PMS. Vulnerability to panic in women with PMS may be specific to the premenstrual phase. Potential psychological and neurobiological mechanisms underlying this phenomenon are discussed.

Panic Disorder-A Malfunction of Multiple Transmitter Control Systems within the Midbrain Periaqueductal Gray Matter?

The clinical and psychopharmacological profile of panic disorder in human patients shows a remarkable similarity to the defensive behavioral response evoked in experimental animals by activation of neurons in the dorsal part of the midbrain periaqueductal gray matter (PAG). Studies of the neural circuitry within the PAG indicate that a subpopulation of GABAergic neurons in the dorsolateral sector may act as an amplifying stage that potentiates inhibitory serotonergic input to the "defense area" within the PAG. These neurons may function as a gain-control system that sets the level of excitability of efferent output neurons, which mediate the autonomic and somatomotor components of panic behavior. Dysfunctional activity within the dorsolateral PAG leading to a destabilization of this control system may be a factor underlying panic behavior and predisposes to the development of panic disorder in susceptible persons. NEUROSCIENTIST 6:48-59, 2000

Blunted autonomic reactivity to pharmacological panic challenge under long-term escitalopram treatment in healthy men

BACKGROUND

Central serotonergic pathways influence brain areas involved in vagal cardiovascular regulation and, thereby, influence sympathetic efferent activity. Selective serotonin reuptake inhibitors (SSRIs) affect multiple serotonergic pathways, including central autonomic pathways. However, only a few studies have assessed SSRI-mediated effects on autonomic reactivity in healthy individuals using heart rate variability (HRV).

METHODS

The present study assessed the influence of long-term treatment with escitalopram (ESC) on autonomic reactivity to an intravenous application of 50 µg cholecystokinin tetrapeptide (CCK-4) in 30 healthy young men using a double-blind, placebo (PLA)-controlled, randomized, within-subject cross-over design. Main outcome measures were time- and frequency-domain HRV parameters, assessed at both baseline and immediately after CCK-4 application.

RESULTS

Results showed substantial effects for the treatment × CCK-4 challenge interaction with respect to heart rate (p < 0.001; pη(2) = 0.499), SDNN (p < 0.001; pη(2) = 576), RMSSD (p = 0.015; pη(2) = 194), NN50% (p = 0.008; pη(2) = 0.224), and LF% (p = 0.014; pη(2) = 0.196), and moderate effects with respect HF% (p = 0.099; pη(2) = 0.094), with PLA subjects showing a higher increase in HR and SDNN and a higher decrease in RMSSD, NN50, LF and HF than subjects in the ESC condition. Thus, ESC treatment significantly blunted the autonomic reactivity to CCK-4. Secondary analysis indicated no effect of the 5-HTTLPR polymorphism on CCK-4-induced autonomic response.

CONCLUSIONS

Our results support findings suggesting an effect of SSRI treatment on autonomic regulation and provide evidence that ESC treatment is associated with blunted autonomic reactivity in healthy men.

The 5-HTTLPR genotype modulates heart rate variability and its adjustment by pharmacological panic challenge in healthy men

Abnormal serotonin transporter (5-HTT) function and autonomic nervous system (ANS) dysregulation has been proposed in panic disorder. However, in contrast to hypothalamo-pituitary-adrenocortical (HPA) functioning, ANS reactivity during panic response has yet not been investigated in humans with respect to the 5-HTT genotype. The present study assessed the influence of challenging by cholecystokinin tetrapeptide (CCK-4) on heart rate variability (HRV) measures, to monitor autonomic reactivity and its relationship to 5-HTT-linked polymorphic region (5-HTTLPR) genotypes. We hypothesized substantial effects of the 5-HTTLPR genotype on autonomic reactivity. We studied 30 healthy young men, 15 of each with the long/long (l/l) or short/short (s/s) genotype for the 5-HTTLPR. All participants received an intravenous application of 50 μg CCK-4. HRV measures were assessed in both groups at baseline and immediately after CCK-4 application. Our results indicated lower parasympathetic activity in s/s carriers during baseline, time and frequency domain measures. CCK-4 application significantly enhanced the sympathetic tone in both groups, leading to diminished group differences. A significant treatment by genotype effect indicated reduced autonomic reactivity to CCK-4 challenge in the s/s compared to l/l carriers. Our findings show enhanced sympathetic and/or diminished cardiac vagal activity under basal conditions and blunted autonomic reactivity in s/s vs. l/l carriers. Our study provides novel data supporting claims that the s/s genotype represents a genetic vulnerability factor associated with inadequate hyporeactivity to stress and extends current knowledge on the impact of the central serotonergic activity on the sympathoadrenal pathway.

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.

The role of menstrual cycle phase and anxiety sensitivity in catastrophic misinterpretation of physical symptoms during a CO(2) challenge

The current study examined the interactive effects of anxiety sensitivity (AS; fear of anxiety and anxiety-related sensations) and menstrual cycle phase (premenstrual phase vs. follicular phase) on panic-relevant responding (i.e., cognitive and physical panic symptoms, subjective anxiety, and skin conductance level). Women completed a baseline session and underwent a 3-min 10 % CO(2)-enriched air biological challenge paradigm during her premenstrual and follicular menstrual cycle phases. Participants were 55 women with no current or past history of panic disorder recruited from the general community (M (age) = 26.18, SD = 8.9) who completed the biological challenge during both the premenstrual and follicular cycle phases. Results revealed that women higher on AS demonstrated increased cognitive panic symptoms in response to the challenge during the premenstrual phase as compared to the follicular phase, and as compared to women lower on AS assessed in either cycle phase. However, the interaction of AS and menstrual cycle phase did not significantly predict physical panic attack symptoms, subjective ratings of anxiety, or skin conductance level in response to the challenge. Results are discussed in the context of premenstrual exacerbations of cognitive, as opposed to physical, panic attack symptoms for high AS women, and the clinical implications of these findings.

CCK-B receptor gene and response to cholecystokinin-tetrapeptide in healthy volunteers

Recent investigations suggest that genes that confer risk for panic disorder (PD) may moderate response to panicogenic agents in healthy volunteers. Given the potential role of the central cholecystokinin receptor (CCKBR) (CT) polymorphism alleles 26 and 27 in PD, the present study attempted to discern if these alleles moderated panicogenic sensitivity to the CCKBR agonist, CCK-tetrapeptide (CCK-4), in healthy volunteers. The study group consisted of 92 men and women with no personal or family history of psychiatric illness. Participants provided blood samples for genotyping of the CCKBR alleles and they received a 25 μg bolus injection of CCK-4. Behavioral, cardiovascular and hormonal responses to the peptide were assessed and analyzed with adjusted linear regression models. Carriers of the CCKBR alleles tended to have higher levels of pre-challenge anxiety and significantly higher levels of anxiety sensitivity and introversion than those without the alleles. However, they did not exhibit an enhanced panicogenic response to CCK-4. Overall, our findings do not demonstrate a role of these alleles in modulating CCK-4's panicogenicity. The significant association between the risk alleles and anxiety-related personality traits is intriguing and further exploration of this association is merited.

Cholecystokinin in plasma and cerebrospinal fluid--a study in healthy young women

Cholecystokinin (CCK) is widely distributed in the brain and is known to affect behavioral and physiological functions including anxiety and pain. The expression of CCK has been shown to be regulated by estrogen and to vary during the estrous cycle in rat brain. In the present study CCK was determined in plasma from 25 healthy women (age 25.0+/-3.5) during the menstrual cycle, in the late luteal phase and in the follicular phase. In the follicular phase, a lumbar puncture was performed at the same time that a plasma sample was taken in 15 subjects. The participants had fasted and were nicotine-free for at least 8h preceding the sampling. We compared CCK-like immunoreactivity (CCK-LI) in plasma from 25 subjects in the late luteal phase (LLP) and the follicular phase (FP) and found that there was no difference during the menstrual cycle (n=25, R(2)=89.60%, p=n.s.). In the follicular phase no significant difference was found between CCK-LI in plasma and in cerebrospinal fluid (CSF) collected at the same time (n=15, R(2)=55.32%, p=n.s.).

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.

The selective serotonin re-uptake inhibitor escitalopram modulates the panic response to cholecystokinin tetrapeptide in healthy men depending on 5-HTTLPR genotype

Selective serotonin re-uptake inhibitors, such as escitalopram, are currently the treatment of choice for patients with panic disorder. The panic response to intravenous cholecystokinin tetrapeptide, a potentially useful paradigm for volunteer translational studies, has so far not been investigated in healthy man after respective pre-treatment. In a double-blind, placebo-controlled, randomized, within subject cross-over design 30 healthy young men, 15 each with the long/long or short/short genotype for the serotonin transporter linked polymorphic region, were pre-treated with 10mg/d of escitalopram orally for six weeks and then challenged with 50 microg of cholecystokinin tetrapeptide. The primary outcome measure was the increase of Acute Panic Inventory ratings by cholecystokinin tetrapeptide. The increase of anxiety, tension and stress hormone secretion were secondary outcome measures. A significant treatment by genotype effect on the increases of Acute Panic Inventory ratings emerged. Panic induced by cholecystokinin tetrapeptide was significantly more pronounced in the short/short genotype subjects under escitalopram vs. placebo pre-treatment. With the exception of significantly elevated serum prolactin after escitalopram, no effects in the secondary outcome measures were detected. Contrary to our expectation, no inhibitory effect of escitalopram upon panic symptoms elicited by choleystokinin tetrapeptide could be demonstrated in healthy men. These findings do not support the potential usefulness of this panic model for proof-of-concept studies. The biological underpinnings of the increased panic symptoms after escitalopram in our volunteers with short/short genotype need further research.

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.

Biological clocks and the practice of psychiatry

Endogenous biological clocks enable living species to acquire some independence in relation to time. They improve the efficiency of biological systems, by allowing them to anticipate future constraints on major physyological systems and cell energy metabolism. The temporal organization of a giwen biological function can be impaired in its coordination with astronomical time or with other biological function. There are also external conditions that influence biological clocks. This temporal organization is complex, and it is possible that a series of psychiatric disorders and syndromes involve primary or secondary changes in biological clocks: seasonal and other mood disorders, premenstrual syndromes, social jet lag, free-running rhythms, and several sleep disorders are among them. In this review, we describe the main concepts relevant to chronobiology and explore the relevance of knowledge about biological clocks to the clinical practice of psychiatry

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.

Cholecystokinin levels in the rat brain during the estrous cycle

Cholecystokinin (CCK) is widely distributed in the brain, and its expression has been shown to be regulated by estrogen. In the present study we used radioimmunoassay to monitor CCK levels in rat brain during a normal estrous cycle. Compared to di-estrous and estrous, CCK-like immunoreactivity was significantly reduced in cingulate and frontal cortex, hippocampus, striatum and hypothalamus during pro-estrous, that is the phase with the highest plasma estradiol levels. These results provide further evidence that circulating steroid hormones in the female rat can influence expression of a brain peptide, in this case CCK, and primarily in the limbic system, which is interesting in the context that CCK has been associated with anxiety and depression in both animals and humans.

Megestrol attenuates the hormonal response to CCK-4-induced panic attacks

Progestational hormones may have anxiolytic properties. CCK-4 (cholecystokinin tetrapeptide) can be used pharmacologically to induce panic attacks both in normal controls and patients suffering from panic disorder. In this study we compared the effects of pretreatment with the progestational hormone megestrol and placebo on CCK-4-induced panic attacks and stress hormone release in healthy male controls. Using a double-blind balanced design, we pretreated 10 medically and psychiatrically healthy male controls with placebo or megestrol 160 mg at 11 p.m. and 8 a.m. (sigma=320 mg) prior to the experiment. Following 1 h of rest, 12 blood samples were drawn between 1,000 h and 1,300 h and analyzed for ACTH and cortisol levels. At 1,100 h, subjects received an intravenous injection of 50 microg CCK-4. Clinical ratings were performed at 1,045 h and 1,110 h, and included the Acute Panic Inventory (API), International Diagnostic Checklist (IDCL), as well as a visual analog scale (VAS) for anxiety and tension. CCK-4 significantly increased anxiety and tension. Pretreatment with megestrol showed no significant effect on clinical ratings. Baseline ACTH and cortisol levels, as well as ACTH and cortisol levels after administration of CCK-4, were significantly reduced after pretreatment with megestrol. In a sample of healthy male controls, pretreatment with megestrol had a profound effect on the hypothalamic-pituitary-adrenal (HPA) axis, whereas the clinical effects on panic attacks were weak. Further studies in a larger sample of subjects, including both females and patients suffering from panic disorder, seem warranted.

Neuropsychopharmacological properties of neuroactive steroids in depression and anxiety disorders

Neuroactive steroids modulate neurotransmission through modulation of specific neurotransmitter receptors such as gamma-aminobutyric acid type A (GABAA) receptors. Preclinical studies suggested that neuroactive steroids may modulate anxiety- and depression-related behaviour and may contribute to the therapeutical effects of antidepressant drugs. Attenuations of 3alpha-reduced neuroactive steroids have been observed during major depression. This disequilibrium can be corrected by successful treatment with antidepressant drugs. However, non-pharmacological antidepressant treatment strategies did not affect neuroactive steroid composition independently from the clinical response. Further research is needed to clarify whether enhancement of neuroactive steroid levels might represent a new therapeutical approach in the treatment of affective disorders. Nevertheless, the first studies investigating the therapeutical effects of exogenously administered dehydroepiandosterone revealed promising results in the treatment of major depression. In addition, in various anxiety disorders alterations of neuroactive steroid levels have been observed. In panic disorder, in the absence of panic attacks, neuroactive steroid composition is opposite to that seen in depression, which may represent counter-regulatory mechanisms against the occurrence of spontaneous panic attacks. However, during experimentally induced panic attacks, there was a pronounced decline in GABAergic neuroactive steroids, which might contribute to the pathophysiology of panic attacks. In conclusion, neuroactive steroids contribute to the pathophysiology of affective disorders and the mechanisms of action of antidepressants. They are important endogenous modulators of depression and anxiety and may provide a basis for the development of novel therapeutic agents in the treatment of affective disorders.

Plasma concentrations of anxiolytic neuroactive steroids in men with panic disorder

Plasma concentrations of neuroactive steroids in men with panic disorder (PD) were measured to evaluate their relations to psychopathology both before and during treatment. Participants comprised 13 men with PD and 10 normal controls. Patients were evaluated while drug-free as well as after 1 and 2 months of paroxetine therapy. Psychopathology was assessed by the State-Trait Anxiety Inventory (STAI), the Panic-Associated Symptom Scale, and the Fear Questionnaire total score. Plasma concentrations of steroids were measured by radioimmunoassay. The plasma concentrations of progesterone and dehydroepiandrosterone were greater in drug-free patients than in controls, whereas those of allopregnanolone and tetrahydrodeoxycorticosterone did not differ between the two groups. Paroxetine treatment for 2 months significantly increased the plasma concentration of allopregnanolone but did not affect those of the other steroids. At 2 months of therapy, allopregnanolone concentrations in patients were significantly greater than those in controls. The plasma concentrations of progesterone and tetrahydrodeoxycorticosterone correlated with the STAI state score in patients before treatment. Our data suggest that neuroactive steroids may play a role in PD in men.

Is premenstrual dysphoria a variant of panic disorder? A review

Patients with premenstrual dysphoric disorder (PMDD) and patients with panic disorder (PD) both experience high rates of panic attacks in laboratory panic provocation studies. Recently, this shared elevated rate of challenge-induced panic has received increasing attention. Researchers have suggested that PMDD and panic disorder may share a pathophysiological or psychobiological link. The purpose of this paper is to review the findings from PMDD challenge studies and the theories advanced to connect PMDD to panic disorder. Taken together, the results of the PMDD challenge studies confirm that agents that incite panic in PD patients do so as well in PMDD women. This shared elevated challenge-induced panic cannot be accounted for by explanations such as a history of PD in PMDD women. None of the physiological theories as currently expressed--suffocation false alarm, gamma-aminobutyric acid (GABA), noradrenergic, serotonergic, and cholecystokinin--yet provides a compelling candidate to account for shared elevated challenge-induced panic in PD and PMDD patients. Psychological perspectives on panic emphasize that bodily sensations themselves can cause fear. Researchers have yet to apply several influential psychological approaches--conditioning, catastrophic misinterpretation, and anxiety sensitivity--to PMDD patients. Because psychological factors influence anxious responding in challenge studies, the search for the biological abnormality best accounting for PMDD panic might benefit from a reframing of the question to one that considers the psychological perspective as well.

Effects of CCK-tetrapeptide in patients with social phobia and obsessive-compulsive disorder

Panicogenic sensitivity to CCK-tetrapeptide (CCK-4) is enhanced in panic disorder patients relative to normal controls (NC). We sought to determine whether CCK-4 sensitivity is augmented in patients with social phobia (SP) (n = 12) and obsessive-compulsive disorder (OCD) (n = 8) versus NC (n = 12). We also determined whether CCK-4 could elicit syndrome-specific symptoms in SP and OCD patients. The study employed a single-blind, placebo-controlled, within-subject design. Behavioral, cardiovascular and hormonal responses to a submaximal dose (20 microg) of CCK-4 were evaluated. Panic frequency after the placebo and CCK-4 challenge varied as a function of diagnosis. Differences in panic frequency between groups and between challenge agents within each group did not, however, reach statistical significance. Further, the number and intensity of panic symptoms, intensity of subjective anxiety, autonomic reactivity and hormonal release after CCK-4 administration did not distinguish the groups. Core symptoms of SP and OCD were unaffected by CCK-4. These data failed to detect significant differences between groups on behavioral, cardiovascular and hormonal response to CCK-4. The lack of effect of CCK-4 on SP and OCD symptoms suggests that this peptide does not play a salient role in the pathophysiology of these disorders.

Association between estrus cycle-related aggression and tidal volume variability in female Wistar rats

Premenstrual dysphoria is characterized by symptoms such as irritability and depressed mood, present during the luteal phase of the menstrual cycle, and disappearing shortly after the onset of menstruation. Subjects with premenstrual dysphoria have previously been reported to display enhanced respiratory variability, and to experience anxiety when exposed to panicogens, such as CO2. In the present study, the possible influence of the estrus cycle and estrus cycle-related aggression on respiratory variability was investigated in female rats of the Wistar strain. The rats were subdivided into two groups: those displaying estrus cycle-related aggression, as evaluated using the resident intruder paradigm, and those not showing aggression throughout the estrus cycle. This model has been developed to serve as an animal model of premenstrual irritability. The former group was found to display higher tidal volume variability in diestrus, as compared to the non-aggressive rats. There was no effect of estrus cycle phase on respiratory variability. These results are well in line with the clinical observation that women with premenstrual dysphoria display higher respiratory variability than controls, and the notion that respiratory variability is a parameter of interest in this context. In our opinion, they also strengthen the concept of this animal model as a model of premenstrual irritability.

Sensitivity to cholecystokinin-tetrapeptide in major depression

BACKGROUND

Sensitivity to the panicogenic effects of cholecystokinin-tetrapeptide (CCK-4) is enhanced in panic disorder patients relative to normal controls (NC). In the present study, we determined whether sensitivity to CCK-4 is enhanced in patients with major depressive disorder (MDD) with no history of panic attacks. We also determined whether CCK-4 would exacerbate depressive symptoms.

METHODS

The study used a double-blind, randomized, placebo-controlled design. Behavioral and cardiovascular response to a submaximal dose (20 microg) of CCK-4 was studied in seven patients with MDD and 12 NC subjects.

RESULTS

None of the subjects panicked with placebo, whereas 29% of MDD and 17% of NC subjects panicked with CCK-4. There was no significant difference between groups on the frequency of CCK-4-induced panic or the number and intensity of panic symptoms. No significant difference was detected for cardiovascular response to the CCK-4 challenge. CCK-4 did not worsen depressive symptoms in MDD patients.

LIMITATIONS

Small number of study subjects.

CONCLUSIONS

These data indicate that MDD patients show a response to CCK-4 that is comparable to NC. The lack of effect of CCK-4 on depressive symptoms suggest that central CCK receptors may not play an important role in the pathophysiology of MDD.

How does premenstrual dysphoric disorder relate to depression and anxiety disorders?

Premenstrual dysphoric disorder (PMDD) is a severe variant of premenstrual syndrome that afflicts approximately 5% of all women of fertile age. The hallmark of this condition is the surfacing of symptoms during the luteal phase of the menstrual cycle, and the disappearance of symptoms shortly after the onset of menstruation. Whereas many researchers have emphasized the similarities between PMDD and anxiety disorders, and in particular panic disorder, others have suggested that PMDD should be regarded as a variant of depression. Supporting both these notions, the treatment of choice for PMDD, the serotonin reuptake inhibitors (SRIs), is also first line of treatment for depression and for most anxiety disorders. In this review, the relationship between PMDD on the one hand, and anxiety and depression on the other, is being discussed. Our conclusion is that PMDD is neither a variant of depression nor an anxiety disorder, but a distinct diagnostic entity, with irritability and affect lability rather than depressed mood or anxiety as most characteristic features. The clinical profile of SRIs when used for PMDD, including a short onset of action, suggests that this effect is mediated by other serotonergic synapses than the antidepressant and anti-anxiety effects of these drugs. Although we hence suggest that PMDD should be regarded as a distinct entity, it should be emphasized that this disorder does display intriguing similarities with other conditions, and in particular with panic disorder, which should be the subject of further studies. Also, the possibility that there are subtypes of PMDD more closely related to depression, or anxiety disorders, than the most common form of the syndrome, should not be excluded.

Panic-related responses to pentagastrin, flumazenil, and thyrotropin-releasing hormone in healthy volunteers

Thyrotropin-releasing hormone ( TRH) induces some somatic symptoms that resemble those of a panic attack, without being considered to be a laboratory panicogen in panic disorder (PD) patients. This study aimed to identify doses of TRH and the laboratory panicogens, pentagastrin and flumazenil, that would produce a similar intensity of panic-related somatic symptoms in healthy volunteers because comparison of the effects of these doses in PD patients could be used to test the hypothesis that these agents have specific panicogenic effects that are not explained solely by cognitively mediated reactions to somatic symptoms. Nine subjects were administered pentagastrin (0.2 micro g/kg) and TRH (600 or 1,200 micro g) in a double-blind, randomized order, within-subjects design. Fifteen subjects received pentagastrin (0.1 micro g/kg), TRH (600 or 1200 micro g) and flumazenil (2 mg) in a double-blind, randomized order within-subjects design. Although low dose pentagastrin (0.1 micro g/kg) induced comparable cardiorespiratory responses to those of TRH, it induced greater anxiety, suggesting that TRH would not be a credible comparator for pentagastrin in challenge studies in PD. However, TRH produced equal or greater symptom and physiological responses compared with flumazenil, suggesting that flumazenil may act as a panicogen in PD via a GABAergic mechanism rather than via a cognitively mediated response to somatic symptoms. This now requires confirmation in PD patients.

The etiology, biology, and evolving pathology of premenstrual syndromes

Menstrually related symptoms and disorders are multidimensional and affect diverse physiologic systems. Elucidation of the pathophysiologic mechanisms of these disorders should allow for a more precise diagnosis, and provide direction for targeted therapeutic interventions. Several biologic mechanisms that underlie menstrually related symptoms have been proposed. They focus mostly on gonadal hormones, their metabolites and interactions with neurotransmitters and neurohormonal systems, such as serotonin, GABA, cholecystokinin, and the renin-angiotensin-aldosterone system. Altered responses of these systems to gonadal hormone's fluctuations during the menstrual cycle, as well as an increased sensitivity to changes in gonadal hormones may contribute to menstrually related symptoms in vulnerable women. Disrupted homeostasis and deficient adaptation may be core underlying mechanisms. Future directions for clinically-relevant progress include identification of specific subgroups of menstrually-related syndromes, assessment of the genetic vulnerability and changes in vulnerability along the life cycle, the diversified mechanisms by which vulnerability is translated into pathophysiology and symptoms, the normalization process as well as syndromes-based and etiology-based clinical trials.

Neuroactive steroids: mechanisms of action and neuropsychopharmacological properties

Steroids influence neuronal function through binding to cognate intracellular receptors which may act as transcription factors in the regulation of gene expression. In addition, certain so-called neuroactive steroids modulate ligand-gated ion channels via non-genomic mechanisms. Especially distinct 3alpha-reduced metabolites of progesterone and deoxycorticosterone are potent positive allosteric modulators of gamma-aminobutyric acid type A (GABA(A)) receptors. However, also classical steroid hormones such as 17beta-estradiol, testosterone and progesterone are neuroactive steroids because they may act as functional antagonists at the 5-hydroxytryptamine type 3 (5-HT(3)) receptor, a ligand-gated ion channel or distinct glutamate receptors. A structure-activity relationship for the actions of a variety of steroids at the 5-HT(3) receptor was elaborated that differed considerably from that known for GABA(A) receptors. Although a bindings site for steroids at GABA(A) receptors is still a matter of debate, meanwhile there is also evidence that steroids interact allosterically with ligand-gated ion channels at the receptor membrane interface. On the other hand, also 3alpha-reduced neuroactive steroids may regulate gene expression via the progesterone receptor after intracellular oxidation into 5alpha-pregnane steroids. Animal studies showed that progesterone is converted rapidly into GABAergic neuroactive steroids in vivo. Progesterone reduces locomotor activity in a dose-dependent fashion in male Wistar rats. Moreover, progesterone and 3alpha-reduced neuroactive steroids produce a benzodiazepine-like sleep EEG profile in rats and humans. During major depression, there is a disequilibrium of such 3alpha-reduced neuroactive steroids which is corrected by successful treatment with antidepressant drugs. Neuroactive steroids may further be involved in the treatment of depression and anxiety with antidepressants in patients during ethanol withdrawal. Studies in patients with panic disorder suggest that neuroactive steroids may also play a role in modulating human anxiety. Both the genomic and non-genomic effects of steroids in the brain may contribute to the pathophysiology of psychiatric disorders and the mechanisms of action of antidepressants. Neuroactive steroids affect a broad spectrum of behavioral functions through their unique molecular properties and may represent a new treatment strategy for neuropsychiatric disorders.

Arginine-vasopressin and oxytocin response to cholecystokinin-tetrapeptide

This study examined the effects of i.v. administration of cholecystokinin-tetrapeptide (CCK-4) on plasma release of arginine vasopressin (AVP) and oxytocin (OT) in women with premenstrual dysphoric disorder (PMDD) and control women, during both the follicular phase and the luteal phase of their menstrual cycle. Plasma AVP and OT concentrations increased following CCK-4 administration. AVP and OT response to CCK-4 was similar for PMDD and control women and unaffected by menstrual cycle phase. AVP and OT may play a role in the hypothalamo-pituitary adrenal (HPA) axis activity associated with the panic response induced by CCK-4.