The panic-inducing properties of the cholecystokinin tetrapeptide CCK4 in patients with panic disorder

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.

The Role of Neuropeptide Y in the Nucleus Accumbens

Neuropeptide Y (NPY), an abundant peptide in the central nervous system, is expressed in neurons of various regions throughout the brain. The physiological and behavioral effects of NPY are mainly mediated through Y1, Y2, and Y5 receptor subtypes, which are expressed in regions regulating food intake, fear and anxiety, learning and memory, depression, and posttraumatic stress. In particular, the nucleus accumbens (NAc) has one of the highest NPY concentrations in the brain. In this review, we summarize the role of NPY in the NAc. NPY is expressed principally in medium-sized aspiny neurons, and numerous NPY immunoreactive fibers are observed in the NAc. Alterations in NPY expression under certain conditions through intra-NAc injections of NPY or receptor agonists/antagonists revealed NPY to be involved in the characteristic functions of the NAc, such as alcohol intake and drug addiction. In addition, control of mesolimbic dopaminergic release via NPY receptors may take part in these functions. NPY in the NAc also participates in fat intake and emotional behavior. Accumbal NPY neurons and fibers may exert physiological and pathophysiological actions partly through neuroendocrine mechanisms and the autonomic nervous system.

Targeting the microbiome-gut-brain axis for improving cognition in schizophrenia and major mood disorders: A narrative review

Cognitive impairment has been consistently found to be a core feature of serious mental illnesses such as schizophrenia and major mood disorders (major depression and bipolar disorder). In recent years, a great effort has been made in elucidating the biological causes of cognitive deficits and the search for new biomarkers of cognition. Microbiome and gut-brain axis (MGB) hormones have been postulated to be potential biomarkers of cognition in serious mental illnesses. The main aim of this review was to synthesize current evidence on the association of microbiome and gut-brain hormones on cognitive processes in schizophrenia and major mood disorders and the association of MGB hormones with stress and the immune system. Our review underscores the role of the MGB axis on cognitive aspects of serious mental illnesses with the potential use of agents targeting the gut microbiota as cognitive enhancers. However, the current evidence for clinical trials focused on the MGB axis as cognitive enhancers in these clinical populations is scarce. Future clinical trials using probiotics, prebiotics, antibiotics, or faecal microbiota transplantation need to consider potential mechanistic pathways such as the HPA axis, the immune system, or gut-brain axis hormones involved in appetite control and energy homeostasis.

The role of cholecystokinin in the induction of aggressive behavior: a focus on the available experimental data (review)

Cholecystokinin (CCK) is a neuropeptide that is (among others) reportedly involved in the pathophysiology of psychiatric disorders. The excitatory role of CCK in negative affective emotions as well as in aversive reactions, antisocial behaviors and memories, has been indicated by numerous electrophysiological, neurochemical and behavioral methodologies on both animal models for anxiety and human studies. The current review article summarizes the existing experimental evidence with regards to the role of CCK in the induction of aggressive behavior, and: (a) synopsizes the anatomical circuits through which it could potentially mediate all types of aggressive behavior, as well as (b) highlights the potential use of these experimental evidence in the current research quest for the clinical treatment of mood and anxiety disorders.

Investigation of cortisol levels in patients with anxiety disorders: a structured review

Anxiety disorders are common and distressing medical conditions, which typically arise in adolescence or early adult life. They can persist for many years, reducing quality of life, limiting academic and occupational achievement, and being responsible for considerable economic pressures. Although a range of psychological and pharmacological treatments are available, their success is often limited, and many patients remain troubled by significant symptom-related disability for long periods. The detailed pathophysiology of each anxiety disorder is not established, and novel treatments that are based solely on current understanding of conventional neurotransmitter function are unlikely to be substantially more effective or better tolerated than current treatments. Investigations of hypothalamo-pituitary axis function across panic disorder, generalized anxiety disorder, specific phobias and social anxiety disorder have produced intriguing findings but not revealed a consistent pattern of endocrine disturbance, perhaps reflecting differences in methodology and the nature and size of the clinical samples. There is a persistent need for large, prospective studies using standardized methods for investigation and data analysis (164 words).

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.

Challenging anxiety: a focus on the specificity of respiratory symptoms

Physiological symptoms are characteristic features of anxiety states. Presumably, specific psychophysiological profiles differentiate between anxiety disorders, which would offer potential for diagnostic purposes. Abundant evidence points to a causal relationship between panic disorder and instability of respiratory regulation. However, the specificity of most measures that indicate aberrant functioning of the respiratory system in PD can be questioned. Possibly, the traditional measures of respiratory functioning are too restricted. The underlying respiratory vulnerability in PD seems to constitute a subtle, unstable trait, which calls for more sensitive and sophisticated measures of respiratory variability and chaos. To increase the probability of finding parameters with diagnostic specificity, the application of disorder specific challenge paradigms is recommended.

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.

CO2 challenge induced HPA axis activation in panic

The hypothalamic-pituitary-adrenal axis (HPA axis) plays a critical role in stress management. Involvement of this physiological axis in the underlying mechanisms of panic disorder (PD) has been suggested. Studies using 35% CO(2) inhalation to provoke panic found no evidence for robust increases in cortisol levels in PD. However, cortisol levels alone may not be conclusive, as this hormone is merely the end product of a complex physiological axis. Sixteen PD patients and 16 healthy control subjects underwent a 35% CO(2) inhalation and a placebo inhalation on separate days according to a fixed order, double-blind design. Both serum and salivary cortisol, as well as adrenocorticotropic hormone (ACTH) were measured at regular time intervals. Cortisol and ACTH levels increased in the patient and control groups following 35% CO(2) inhalation. The magnitude of the increase was similar in patients and controls despite marked differences in anxiety. This study is the first to document a clear HPA response following 35% CO(2) inhalation in both PD patients and controls. This effect occurs independently of the specific panicogenic properties of the CO(2) challenge. It remains to be clarified whether panic is initially accompanied by major HPA axis activation or whether other stress-responsive systems underlie panic.

Panic disorder

Panic disorder is a common mental disorder that affects up to 5% of the population at some point in life. It is often disabling, especially when complicated by agoraphobia, and is associated with substantial functional morbidity and reduced quality of life. The disorder is also costly for individuals and society, as shown by increased use of health care, absenteeism, and reduced workplace productivity. Some physical illnesses (eg, asthma) commonly occur with panic disorder, and certain lifestyle factors (eg, smoking) increase the risk for the disorder, but causal pathways are still unclear. Genetic and early experiential susceptibility factors also exist, but their exact nature and pathophysiological mechanisms remain unknown. Despite an imprecise, although increased, understanding of cause, strong evidence supports the use of several effective treatments (eg, pharmacological, cognitive-behavioural). The adaptation and dissemination of these treatments to the frontlines of medical-care delivery should be urgent goals for the public-health community.

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.

Neurobiologie et pharmacothérapie de la phobie sociale

Social phobia (also known as social anxiety disorder) is still not clearly understood. It was not established as an authentic psychiatric entity until the diagnostic nomenclature of the American Psychiatric Association DSM III in 1980. In recent years, increasing attention among researchers has contributed to provide important information about the genetic, familial and temperamental bases of social phobia and its neurochemical, neuroendocrinological and neuroanatomical substrates, which remain to be further investigated. Up to date, there have been several findings about the possible influence of variables, including particularly genetic, socio-familial and early temperamental (eg behavioral inhibition) factors that represent risk for the later development of social phobia. Clinical neurobiological studies, based on the use of exogenous compounds such as lactate, CO2, caffeine, epinephrine, flumazenil or cholecystokinin/pentagastrin to reproduce naturally occurring phobic anxiety, have shown that patients with social phobia appear to exhibit an intermediate sensitivity between patients with panic disorder and control subjects. No difference in the rate of panic attacks in response to lactate, low concentrations of CO2 (5%), epinephrine or flumazenil was observed between patients with social phobia and normal healthy subjects, both being less reactive compared to patients with panic disorder. However, patients with social phobia had similar anxiety reactions to high concentrations of CO2 (35%), caffeine or cholecystokinin/pentagastrin than those seen in patients with panic disorder, both being more intensive than in controls. Several lines of evidence suggest specific neurotransmitter system alterations in social phobia, especially with regard to the serotoninergic, noradrenergic and dopaminergic systems. Although no abnormality in platelet serotonin transporter density has been found, patients with social phobia appear to show an enhanced sensitivity of both post-synaptic 5HT1A and 5HT2 serotonin receptor subtypes, as reflected by increased anxiety and hormonal responses to serotoninergic probes. Platelet 5HT2 receptor density has also been reported to be positively correlated to symptom severity in patients with social phobia. During anticipation of public speaking, heart rate was elevated in patients with social phobia compared to controls. Norepinephrine response to the orthostatic challenge test or to the Valsalva maneuver was also greater in patients with social phobia. While normal beta-adrenergic receptor number was observed in lymphocytes, a blunted response of growth hormone to clonidine, an a2-adrenergic agonist, was reported. This suggests reduced post-synaptic a2-adrenergic receptor functioning related to norepinephrine overactivity in social phobia. Decreased cerebrospinal fluid levels of the dopamine metabolite homovanillic acid have also been observed. There are relatively few reports of involvement of the adrenal and thyroid functions in social phobia, and all that has been noted is that patients with social phobia show an exaggerated adrenocortical response to a psychological stressor. Recent advances in neuro-imaging have contributed to find low striatal dopamine D2 receptor binding or low dopamine transporter site density in patients with social phobia. They have also demonstrated the involvement of the cortico-limbic pathways, including the prefrontal cortex, hippocampus and amygdala, which show an increased activity in different experimental conditions. These brain regions have extensively been reported to play an important role in the cognitive appraisal in determining the significance of environmental stimuli, in the emotional and mnemonic integration of information, and in the expression of contextual fear-conditioned behaviors, which might be disrupted in the light of the phenomelogical aspects of social phobia. A substantial body of literature based on case reports, open and placebo-controlled trials, has now clearly examined the efficacy of major classes of psychotropic agents including monoamine oxidase inhibitors, beta-blockers, selective serotonin reuptake inhibitors and benzodiazepines in social phobia. Until recently, irreversible non-selective monoamine oxidase inhibitors, of which phenelzine was the most extensively evaluated, were considered as the most efficacious treatment in reducing the symptomatology associated with social phobia in 50-70% of cases after 4 to 6 weeks. However, side effects and dietary restrictions limit their use. This led to the development of reversible inhibitors of monoamine oxidase A, for which careful dietary monitoring is not required. Moclobemide has been the most widely studied but produced unconvincingly therapeutic effects on social phobic symptoms. To date, selective serotonin reuptake inhibitors may be considered as a reasonable first-line pharmacotherapy for social phobia. There is growing evidence for the efficacy of the selective serotonin reuptake inhibitors fluvoxamine, fluoxetine, citalopram, paroxetine and sertraline. They have beneficial effects with response rates ranging from 50 to 80% in social phobia. It has been recommended that the treatment period should be extended at least 6 months beyond the early improvement achieved within the first 4 to 6 weeks. The overall advantages include tolerability with a low risk of adverse events. The benzodiazepines clonazepam and alprazolam have also been proposed for the treatment of social phobia. Symptomatic relief occurred in 40 to 80% of the cases with a relatively rapid onset of action within the first two weeks. Untoward effects, discontinuation-related withdrawal symptoms and abuse or dependence liability constitute major concerns about the use of benzodiazepines, so they should be reserved for cases unresponsive to the safer medications cited above. Beta-blockers such as atenolol and propanolol have commonly been employed in performance anxiety, decreasing autonomic symptoms (eg, tachycardia, sweating and dry mouth). However, they are not effective in the generalized form of social phobia. Other pharmacologic alternatives seem helpful for the management of social phobia, including venlafaxine, gabapentin, bupropion, nefazodone or augmentation with buspirone. Preliminary studies point to promising effects of these agents. Larger controlled clinical trials are now needed to confirm their potential role in the treatment of social phobia.

Hypothalamic-pituitary-adrenal axis function following a 35% CO2 inhalation in healthy volunteers

RATIONALE

The hypothalamic-pituitary-adrenal axis (HPA axis) is a central component of the brain's neuroendocrine response to stress. The extent of increase in cortisol secretion, provides an index of the HPA axis activity, and in this way, objectively reflects perceived stress. In healthy subjects, the 35% CO(2) inhalation does hardly induce stress, as expressed in anxiety. However, inconsistent results have been found in studies investigating the cortisol response following CO(2) inhalation. Clarity has to be reached about the normal reaction to this challenge, especially because this model is still a very valuable method to study central aspects of panic.

OBJECTIVES

The present study aimed to test the hypothesis that a single breath of 35% CO(2) would not induce cortisol release in healthy volunteers.

METHODS

In the current study, 20 healthy subjects underwent both a 35% CO(2) and a placebo inhalation in a randomised, single blind fashion. Cortisol levels were determined in saliva samples, taken at regular intervals.

RESULTS

No differences were found between the CO(2) and the placebo condition. In both conditions a significant time effect was found, which can be subscribed to normal variation in the circadian rhythm. Furthermore, only modest subjective anxiety scores were found in the CO(2) condition.

CONCLUSIONS

These results provide biological evidence for the hypothesis that healthy subjects are not affected by the 35% CO(2) challenge in a clinically significant way. Characteristic, PD patients react much stronger to the inhalation. Thus, in addition to psychological parameters, healthy subjects also constitute an ideal comparison group with regard to endocrinological parameters.

Neuroendocrine pharmacology of stress

Exposure to hostile conditions initiates responses organized to enhance the probability of survival. These coordinated responses, known as stress responses, are composed of alterations in behavior, autonomic function and the secretion of multiple hormones. The activation of the renin-angiotensin system and the hypothalamic-pituitary-adrenocortical axis plays a pivotal role in the stress response. Neuroendocrine components activated by stressors include the increased secretion of epinephrine and norepinephrine from the sympathetic nervous system and adrenal medulla, the release of corticotropin-releasing factor (CRF) and vasopressin from parvicellular neurons into the portal circulation, and seconds later, the secretion of pituitary adrenocorticotropin (ACTH), leading to secretion of glucocorticoids by the adrenal gland. Corticotropin-releasing factor coordinates the endocrine, autonomic, behavioral and immune responses to stress and also acts as a neurotransmitter or neuromodulator in the amygdala, dorsal raphe nucleus, hippocampus and locus coeruleus, to integrate brain multi-system responses to stress. This review discussed the role of classical mediators of the stress response, such as corticotropin-releasing factor, vasopressin, serotonin (5-hydroxytryptamine or 5-HT) and catecholamines. Also discussed are the roles of other neuropeptides/neuromodulators involved in the stress response that have previously received little attention, such as substance P, vasoactive intestinal polypeptide, neuropeptide Y and cholecystokinin. Anxiolytic drugs of the benzodiazepine class and other drugs that affect catecholamine, GABA(A), histamine and serotonin receptors have been used to attenuate the neuroendocrine response to stressors. The neuroendocrine information for these drugs is still incomplete; however, they are a new class of potential antidepressant and anxiolytic drugs that offer new therapeutic approaches to treating anxiety disorders. The studies described in this review suggest that multiple brain mechanisms are responsible for the regulation of each hormone and that not all hormones are regulated by the same neural circuits. In particular, the renin-angiotensin system seems to be regulated by different brain mechanisms than the hypothalamic-pituitary-adrenal system. This could be an important survival mechanism to ensure that dysfunction of one neurotransmitter system will not endanger the appropriate secretion of hormones during exposure to adverse conditions. The measurement of several hormones to examine the mechanisms underlying the stress response and the effects of drugs and lesions on these responses can provide insight into the nature and location of brain circuits and neurotransmitter receptors involved in anxiety and stress.

10 microg CCK-4 premedication and 35% CO2 challenge in healthy volunteers

1. The purpose of the study was to confirm whether a subthreshold dose of CCK-4 would enhance the vulnerability of healthy subjects to a 35% carbon dioxide challenge. 2. 40 subjects, with no prior or present psychiatric disorder and in good physical health were challenged with a vital capacity breath of a 35% carbon dioxide 65% oxygen mixture, immediately after an intravenous injection of 10 microg CCK-4 or placebo, according to a random order, double blind, separate group design. 3. Subjects reported significantly less anxiety and panic symptoms upon carbon dioxide after premedication with CCK-4 than after placebo. 4. CCK-4 and carbon dioxide seem to inhibit rather than enhance each other's effects, possibly through an effect on different neurobiological systems.

Effects of CCK-4 infusion on the acoustic eye-blink startle and psychophysiological measures in healthy volunteers

The acoustic startle response (ASR) and a range of psychophysiological parameters were evaluated during a continuous intravenous administration of cholecystokinin-tetrapeptide (CCK-4) in healthy volunteers. Subjects (n=28) were randomly assigned to double-blind infusion of either CCK-4 (0.5 mg/60 min) or placebo. The ASR sessions were performed prior to infusion and at 20 min and 50 min after the onset of infusion by recording eye-blink response to a series of acoustic stimuli (110 dB, 40 ms). An effect of CCK-4 on the eye-blink startle was observed in the first half of infusion. CCK-4 produced an increase of eye-blink startle amplitude from baseline values in contrast to the decrease observed at this time point with placebo. A mild increase in anxiety and heart rate followed by fatigue was reported with CCK-4. Administration of CCK-4 produced increases in plasma concentrations of adrenocorticotropic hormone, cortisol, prolactin and growth hormone. The results of this study show that a prolonged intravenous administration of CCK-4 may be a useful challenge method for further studies on the role of CCK system in the modulation of human anxiety and stress response.

Neurobiology of panic disorder

Various provocative agents, including sodium lactate, carbon dioxide (CO2), caffeine, yohimbine, serotoninergic agents, and cholecystokinin (CCK), have been utilized as panicogenics in studies on healthy volunteers as well as in panic disorder patients. An overview of the utilization of these agents to study the neurobiology of panic disorder is presented. The possible roles of several neurotransmitters and neuromodulators in the etiology of panic disorder and in the actions of drugs used in its treatment are also discussed.

Decrease in short-term memory function induced by CCK-4 in healthy volunteers

The purpose of this study was to assess the effects of continuous intravenous infusion of the central cholecystokinin (CCK) receptor agonist, CCK-4, on short-term memory and psychomotor performance in healthy volunteers in a double-blind, placebo-controlled, parallel group study. Compared to placebo, CCK-4 (0.5 mg/h) significantly impaired performance on free-recall and recognition of words in the middle of the CCK-4 infusion, but did not affect psychomotor acuity. The results of this study indicate that CCK-4 may exert a negative influence on memory consolidation and retrieval.

The cholecystokinin-B receptor antagonist CI-988 failed to affect CCK-4 induced symptoms in panic disorder patients

The effects of the cholecystokinin-B (CCK-B) receptor antagonist CI-988 on symptoms elicited by the cholecystokinin tetrapeptide (CCK4) were studied in DSM-IIIR patients with panic disorder. The study employed a double-blind, two-period incomplete block design. Patients (n = 14) received two different dosages of CI-988 (50 mg or 100 mg) or placebo 2 h prior to an IV bolus injection of CCK4 (20 micrograms) on two separate occasions. The primary efficacy parameter was the total intensity score on the Panic Symptoms Scale (PSS). Secondary parameters were the number of panic symptoms, time to and occurrence of the first panic symptoms, duration of symptoms, intensity of apprehension and the percentage of patients who did not have a panic attack. The PSS failed to show a statistically significant treatment effect on any of these outcome measures. The average panic rate was 50%, 14.3% and 37.5% after placebo, 50 and 100 mg CI-988, respectively. The differences in panic rate were not statistically significant. The results of this study suggest that CI-988 in doses up to 100 mg is not effective in reducing symptoms of panic anxiety induced by CCK4.

The role of the 'central' cholecystokinin-B receptor in panic disorder

Research investigating the neurobiological underpinnings of anxiety disorder have mainly been focused on dysfunction of the GABA, noradrenergic and serotonergic (5-HT) neuronal systems. Just recently, in both animal and human studies, evidence has been found for a possible role of the cholecystokinin (CCK) neuronal system in the pathogenesis of anxiety disorder. Behaviorally, animal studies revealed anxiogenic-like properties for the 'central' CCKB receptor agonists, while CCKB receptor antagonists displayed intrinsic anxiolytic properties. Similarly, in man, CCKB receptor agonists, like pentagastrin and CCK4, were found to be able to elicited panic attacks in both panic disorder (PD) patients and healthy volunteers. These effects appear due to stimulation of the CCKB receptor. In addition, clinically effective panicolytic agents reduce the sensitivity to CCK4 in PD patients. Taken together, these findings may suggest a role for CCK in the neurobiology of PD. On the other hand, there is circumstantial evidence for involvement of several other neuronal systems, such as the serotonergic, noradrenergic and GABA-ergic system, in the regulation of anxiety. Interestingly, evidence has been found for an interaction between CCK and 5-HT and that this interaction plays a role in the mediation of anxiety. This presentation will critically discuss the evidence for the role of the CCKB receptor in anxiety and in addition, will focus on the putative evidence that the role of CCK in anxiety is mediated by its interaction with the serotonergic neuronal system.