Neuronal network of panic disorder: the role of the neuropeptide cholecystokinin

Expression of guanylate cyclase C in human prefrontal cortex depends on sex and feeding status

Introduction

Guanylate cyclase C (GC-C) has been detected in the rodent brain in neurons of the cerebral cortex, amygdala, midbrain, hypothalamus, and cerebellum.

Methods

In this study we determined GC-C protein expression in Brodmann areas (BA) 9, BA10, BA11, and BA32 of the human prefrontal cortex involved in regulation of feeding behavior, as well as in the cerebellar cortex, arcuate nucleus of hypothalamus and substantia nigra in brain samples of human 21 male and 13 female brains by ELISA with postmortem delay < 24 h.

Results

GC-C was found in all tested brain areas and it was expressed in neurons of the third cortical layer of BA9. The regulation of GC-C expression by feeding was found in male BA11 and BA10-M, where GC-C expression was in negative correlation to the volume of stomach content during autopsy. In female BA11 there was no correlation detected, while in BA10-M there was even positive correlation. This suggests sex differences in GC-C expression regulation in BA11 and BA10-M. The amount of GC-C was higher in female BA9 only when the death occurred shortly after a meal, while expression of GC-C was higher in BA10-O only when the stomach was empty. The expression of GC-C in female hypothalamus was lower when compared to male hypothalamus only when the stomach was full, suggesting possibly lower satiety effects of GC-C agonists in women.

Discussion

These results point toward the possible role of GC-C in regulation of feeding behavior. Since, this is first study of GC-C regulation and its possible function in prefrontal cortex, to determine exact role of GC-C in different region of prefrontal cortex, especially in humans, need further studies.

Cholecystokinin (CCK): a neuromodulator with therapeutic potential in Alzheimer's and Parkinson's disease

Cholecystokinin (CCK) is a neuropeptide modulating digestion, glucose levels, neurotransmitters and memory. Recent studies suggest that CCK exhibits neuroprotective effects in Alzheimer's disease (AD) and Parkinson's disease (PD). Thus, we review the physiological function and therapeutic potential of CCK. The neuropeptide facilitates hippocampal glutamate release and gates GABAergic basket cell activity, which improves declarative memory acquisition, but inhibits consolidation. Cortical CCK alters recognition memory and enhances audio-visual processing. By stimulating CCK-1 receptors (CCK-1Rs), sulphated CCK-8 elicits dopamine release in the substantia nigra and striatum. In the mesolimbic pathway, CCK release is triggered by dopamine and terminates reward responses via CCK-2Rs. Importantly, activation of hippocampal and nigral CCK-2Rs is neuroprotective by evoking AMPK activation, expression of mitochondrial fusion modulators and autophagy. Other benefits include vagus nerve/CCK-1R-mediated expression of brain-derived neurotrophic factor, intestinal protection and suppression of inflammation. We also discuss caveats and the therapeutic combination of CCK with other peptide hormones.

Lessons from lonely flies: Molecular and neuronal mechanisms underlying social isolation

Animals respond to changes in the environment which affect their internal state by adapting their behaviors. Social isolation is a form of passive environmental stressor that alters behaviors across animal kingdom, including humans, rodents, and fruit flies. Social isolation is known to increase violence, disrupt sleep and increase depression leading to poor mental and physical health. Recent evidences from several model organisms suggest that social isolation leads to remodeling of the transcriptional and epigenetic landscape which alters behavioral outcomes. In this review, we explore how manipulating social experience of fruit fly Drosophila melanogaster can shed light on molecular and neuronal mechanisms underlying isolation driven behaviors. We discuss the recent advances made using the powerful genetic toolkit and behavioral assays in Drosophila to uncover role of neuromodulators, sensory modalities, pheromones, neuronal circuits and molecular mechanisms in mediating social isolation. The insights gained from these studies could be crucial for developing effective therapeutic interventions in future.

Substance P, NPY, CCK and their receptors in five brain regions in major depressive disorder with transcriptomic analysis of locus coeruleus neurons

Major depressive disorder (MDD) is a serious disease and a burden to patients, families and society. Rodent experiments and human studies suggest that several neuropeptide systems are involved in mood regulation. The aim of this study is two-fold: (i) to monitor, with qPCR, transcript levels of the substance P/tachykinin (TAC), NPY and CCK systems in bulk samples from control and suicide subjects, targeting five postmortem brain regions including locus coeruleus (LC); and (ii) to analyse expression of neuropeptide family transcripts in LC neurons of 'normal' postmortem brains by using laser capture microdissection with Smart-Seq2 RNA sequencing. qPCR revealed distinct regional expression patterns in male and female controls with higher levels for the TAC system in the dorsal raphe nucleus and LC, versus higher transcripts levels of the NPY and CCK systems in prefrontal cortex. In suicide patients, TAC, TAC receptors and a few NPY family transcript levels were increased mainly in prefrontal cortex and LC. The second study on 'normal' noradrenergic LC neurons revealed expression of transcripts for GAL, NPY, TAC1, CCK, and TACR1 and many other peptides (e.g. Cerebellin4 and CARTPT) and receptors (e.g. Adcyap1R1 and GPR173). These data and our previous results on suicide brains indicates that the tachykinin and galanin systems may be valid targets for developing antidepressant medicines. Moreover, the perturbation of neuropeptide systems in MDD patients, and the detection of further neuropeptide and receptor transcripts in LC, shed new light on signalling in noradrenergic LC neurons and on mechanisms possibly associated with mood disorders.

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.

Cholecystokinin (CCK) and its receptors (CCK1R and CCK2R) in chickens: functional analysis and tissue expression

Cholecystokinin (CCK) is widely distributed in the gastrointestinal tract and central nervous system, regulating a range of physiological functions by activating its receptors (CCK1R and CCK2R). Compared to those in mammals, the CCK gene and its receptors have already been cloned in various birds, such as chickens. However, knowledge regarding their functionality and tissue expression is limited. In this study, we examined the expression of CCK and its 2 receptors in chicken tissues. In addition, the functionality of the 2 receptors was investigated. Using 3 cell-based luciferase reporter systems and western blots, we demonstrated that chicken (c-) CCK1R could be potently activated by cCCK-8S but not cCCK-4, whereas cCCK2R could be activated by cCCK-8S and cCCK-4 with similar efficiency. Using RNA-sequencing, we revealed that cCCK is abundantly expressed in the testis, ileum, and several brain regions (cerebrum, midbrain, cerebellum, hindbrain, and hypothalamus). The abundant expression of CCK in the hypothalamus was further supported by immunofluorescence. In addition, cCCK1R is highly expressed in the pancreas and moderately expressed in various intestinal regions (ileum, cecum, and rectum) and the pituitary gland, whereas cCCK2R expression is primarily restricted to the brain. Our data reveal the differential specificities of CCK receptors for various CCK peptides. In combination with the differential tissue distribution of CCK and its receptors, the present study helps to understanding the physiological functions of CCK/CCKRs in birds.

Cholecystokinin B receptor gene polymorphism (rs2941026) is associated with anxious personality and suicidal thoughts in a longitudinal study

OBJECTIVES

Cholecystokinin is a neuropeptide with a role in the neurobiology of adaptive behaviour that is implicated in anxiety disorders, while the underlying mechanisms currently remain insufficiently explained. The rs2941026 variation in the cholecystokinin B receptor gene has previously been associated with trait anxiety. Our aim was to investigate associations between the CCK_B receptor gene polymorphism rs2941026 with anxiety, personality, depressiveness and suicidality in a longitudinal study of late adolescence and early adulthood.

METHODS

We used reports on trait and state anxiety, depressiveness and suicidal thoughts, as well as Affective Neuroscience Personality Scales, from the two birth cohorts of the Estonian Children Personality, Behaviour and Health Study. We measured associations between the CCKBR gene rs2941026 and anxiety-related phenotypes both longitudinally and cross-sectionally at ages 15, 18, 25 and 33.

RESULTS

Homozygosity for both alleles of the CCKBR rs2941026 was associated with higher trait and state anxiety in the longitudinal analysis. Cross-sectional comparisons were statistically significant at ages 18 and 25 for trait anxiety and at ages 25 and 33 for state anxiety. Higher depressiveness and suicidal thoughts were associated with the A/A genotype at age 18. Additionally, homozygosity for the A-allele was related to higher FEAR and SADNESS in the Affective Neuroscience Personality Scales. The genotype effects were more apparent in females, who displayed higher levels of negative affect overall.

CONCLUSIONS

CCKBR genotype is persistently associated with negative affect in adolescence and young adulthood. The association of the CCKBR rs2941026 genotype with anxiety-related phenotypes is more pronounced in females.

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.

Cholecystokinin/sulfakinin peptide signaling: conserved roles at the intersection between feeding, mating and aggression

Neuropeptides are the most diverse messenger molecules in metazoans and are involved in regulation of daily physiology and a wide array of behaviors. Some neuropeptides and their cognate receptors are structurally and functionally well conserved over evolution in bilaterian animals. Among these are peptides related to gastrin and cholecystokinin (CCK). In mammals, CCK is produced by intestinal endocrine cells and brain neurons, and regulates gall bladder contractions, pancreatic enzyme secretion, gut functions, satiety and food intake. Additionally, CCK plays important roles in neuromodulation in several brain circuits that regulate reward, anxiety, aggression and sexual behavior. In invertebrates, CCK-type peptides (sulfakinins, SKs) are, with a few exceptions, produced by brain neurons only. Common among invertebrates is that SKs mediate satiety and regulate food ingestion by a variety of mechanisms. Also regulation of secretion of digestive enzymes has been reported. Studies of the genetically tractable fly Drosophila have advanced our understanding of SK signaling mechanisms in regulation of satiety and feeding, but also in gustatory sensitivity, locomotor activity, aggression and reproductive behavior. A set of eight SK-expressing brain neurons plays important roles in regulation of these competing behaviors. In males, they integrate internal state and external stimuli to diminish sex drive and increase aggression. The same neurons also diminish sugar gustation, induce satiety and reduce feeding. Although several functional roles of CCK/SK signaling appear conserved between Drosophila and mammals, available data suggest that the underlying mechanisms differ.

An Apparently Balanced Complex Chromosome Rearrangement Involving Seven Breaks and Four Chromosomes in a Healthy Female and Segregation/Recombination in Her Affected Son

Duplication of the distal 1q and 4p segments are both characterized by the presence of intellectual disability/neurodevelopmental delay and dysmorphisms. Here, we describe a male with a complex chromosome rearrangement (CCR) presenting with overlapping clinical findings between these 2 syndromes. In order to better characterize this CCR, classical karyotyping, FISH, and chromosomal microarray analysis were performed on material from the patient and his parents, which revealed an unbalanced karyotype with duplications at 1q41q43 and 4p15.2p14 in the proband. The rearrangements, which were derived from a maternal balanced karyotype, included an insertion of a segment from the long to the short arm of chromosome 1, a balanced translocation involving chromosomes 14 and 18, and an insertion of a segment from the short arm of chromosome 4 into the derived chromosome 14. This study aimed to better define the clinical history and prognosis of a patient with this rare category of chromosomal aberration. Our results suggest that the frequency of CCR in the general population may be underestimated; when balanced, they may not have a phenotypic effect. Moreover, they emphasize the need for cytogenetic techniques complementary to chromosomal microarray for proper genetic counseling.

Cholecystokinin and Panic Disorder: Reflections on the History and Some Unsolved Questions

The classic gut hormone cholecystokinin (CCK) and its CCK2-receptor are expressed in almost all regions of the brain. This widespread expression makes CCK by far the most abundant peptidergic transmitter system in the brain. This CNS-ubiquity has, however, complicated the delineation of the roles of CCK peptides in normal brain functions and neuropsychiatric diseases. Nevertheless, the common panic disorder disease is apparently associated with CCK in the brain. Thus, the C-terminal tetrapeptide fragment of CCK (CCK-4) induces, by intravenous administration in a dose-related manner, panic attacks that are similar to the endogenous attacks in panic disorder patients. This review describes the history behind the discovery of the panicogenic effect of CCK-4. Subsequently, the review discusses three unsettled questions about the involvement of cerebral CCK in the pathogenesis of anxiety and panic disorder, including therapeutic attempts with CCK2-receptor antagonists.

Sex Differences in the Blood Oxygen Level-Dependent Signal to Placebo Analgesia and Nocebo Hyperalgesia in Experimental Pain: A Functional MRI Study

Objective

Placebo as well as nocebo responses are widely found in scientific research and clinical practice. Growing evidence suggests sex differences in placebo as well as nocebo responses. However, data concerning this question are still insufficient. This study examined whether the BOLD signals of two responses, as measured with functional MRI (fMRI), differ by sex under conditions of equivalent experimental pain perception.

Method

Thirty-one healthy volunteers (14 female) underwent two fMRI scans, once during a placebo intervention and once during a nocebo intervention, pseudorandomly ordered, in an acute lower back pain (ALBP) model. We collected visual analog scale (VAS) data after each scanning. fMRI data from different sex groups were subjected to functional connectivity (FC) analysis and behavioral correlation analysis (BCA).

Results

The results showed statistical differences in VAS scores between male and female participants, in both placebo and nocebo responses. Both groups also showed reduced FC in the pain-associated network of the placebo response and elevated FC in the pain-related network of the nocebo response. However, in the placebo condition, male participants displayed increased FC in the ventromedial prefrontal cortex, parahippocampal gyrus (PHP), and posterior cingulate cortex (PCC), while female participants showed increased FC in the dorsolateral prefrontal cortex, hippocampal gyrus (HP), and insular cortex (IC). In the nocebo condition, male participants showed decreased FC in the PCC and HP, while female participants displayed decreased FC in the mid-cingulate cortex, thalamus (THS), and HP. The BCA results of the two groups were also different.

Conclusion

We found that the endogenous opioid system and reward circuit play a key role in sex differences of placebo response and that anxiety and its secondary reactions may cause the sex differences of nocebo response.

Cholecystokinin-like peptide mediates satiety by inhibiting sugar attraction

Feeding is essential for animal survival and reproduction and is regulated by both internal states and external stimuli. However, little is known about how internal states influence the perception of external sensory cues that regulate feeding behavior. Here, we investigated the neuronal and molecular mechanisms behind nutritional state-mediated regulation of gustatory perception in control of feeding behavior in the brown planthopper and Drosophila. We found that feeding increases the expression of the cholecystokinin-like peptide, sulfakinin (SK), and the activity of a set of SK-expressing neurons. Starvation elevates the transcription of the sugar receptor Gr64f and SK negatively regulates the expression of Gr64f in both insects. Interestingly, we found that one of the two known SK receptors, CCKLR-17D3, is expressed by some of Gr64f-expressing neurons in the proboscis and proleg tarsi. Thus, we have identified SK as a neuropeptide signal in a neuronal circuitry that responds to food intake, and regulates feeding behavior by diminishing gustatory receptor gene expression and activity of sweet sensing GRNs. Our findings demonstrate one nutritional state-dependent pathway that modulates sweet perception and thereby feeding behavior, but our experiments cannot exclude further parallel pathways. Importantly, we show that the underlying mechanisms are conserved in the two distantly related insect species.

Food intake is critical for animal survival and reproduction and is regulated both by internal states that signal appetite or satiety, and by external sensory stimuli. It is well known that the internal nutritional state influences the strength of the chemosensory perception of food signals. Thus, both gustatory and olfactory signals of preferred food are strengthened in hungry animals. However, the molecular mechanisms behind satiety-mediated modulation of taste are still not known. We show here that cholecystokinin-like (SK) peptide in brown planthopper and Drosophila signals satiety and inhibits sugar attraction by lowering the activity of sweet-sensing gustatory neurons and transcription of a sugar receptor gene, Gr64f. We show that SK peptide signaling reflects the nutritional state and inhibits feeding behavior. Re-feeding after starvation increases SK peptide expression and spontaneous activity of SK producing neurons. Interestingly, we found that SK peptide negatively regulates the expression of the sweet gustatory receptor and that activation of SK producing neurons inhibits the activity of sweet-sensing gustatory neurons (GRNs). Furthermore, we found that one of the two known SK peptide receptors is expressed in some sweet-sensing GRNs in the proboscis and proleg tarsi. In summary, our findings provide a mechanism that is conserved in distantly related insects and which explains how feeding state modulates sweet perception to regulate feeding behavior. Thus, we have identified a neuropeptide signal and its neuronal circuitry that respond to satiety, and that regulate feeding behavior by inhibiting gustatory receptor gene expression and activity of sweet sensing GRNs.

Quantitative Peptidomics of Mouse Brain After Infection With Cyst-Forming Toxoplasma gondii

Toxoplasma gondii is an obligate intracellular parasite capable of establishing persistent infection within the host brain and inducing severe neuropathology. Peptides are important native molecules responsible for a wide range of biological functions within the central nervous system. However, peptidome profiling in host brain during T. gondii infection has never been investigated. Using a label-free peptidomics approach (LC–MS/MS), we identified a total of 2,735 endogenous peptides from acutely infected, chronically infected and control brain samples following T. gondii infection. Quantitative analysis revealed 478 and 344 significantly differentially expressed peptides (DEPs) in the acute and chronic infection stages, respectively. Functional analysis of DEPs by Gene Ontology suggested these DEPs mainly originated from cell part and took part in cellular process. We also identified three novel neuropeptides derived from the precursor protein cholecystokinin. These results demonstrated the usefulness of quantitative peptidomics in determining bioactive peptides and elucidating their functions in the regulation of behavior modification during T. gondii infection.

Pharmacotherapy of Anxiety Disorders: Current and Emerging Treatment Options

(Appeared originally in Frontiers in Psychiatry 2020 Dec 23; 11:595584)

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.

Role of PPARs in Progression of Anxiety: Literature Analysis and Signaling Pathways Reconstruction

Peroxisome proliferator-activated receptor (PPAR) group includes three isoforms encoded by PPARG, PPARA, and PPARD genes. High concentrations of PPARs are found in parts of the brain linked to anxiety development, including hippocampus and amygdala. Among three PPAR isoforms, PPARG demonstrates the highest expression in CNS, where it can be found in neurons, astrocytes, and glial cells. Herein, the highest PPARG expression occurs in amygdala. However, little is known considering possible connections between PPARs and anxiety behavior. We reviewed possible connections between PPARs and anxiety. We used the Pathway Studio software (Elsevier). Signal pathways were created according to previously developed algorithms. SNEA was performed in Pathway Studio. Current study revealed 14 PPAR-regulated proteins linked to anxiety. Possible mechanism of PPAR involvement in neuroinflammation protection is proposed. Signal pathway reconstruction and reviewing aimed to reveal possible connection between PPARG and CCK-ergic system was conducted. Said analysis revealed that PPARG-dependent regulation of MME and ACE peptidase expression may affect levels of nonhydrolysed, i.e., active CCK-4. Impairments in PPARG regulation and following MME and ACE peptidase expression impairments in amygdala may be the possible mechanism leading to pathological anxiety development, with brain CCK-4 accumulation being a key link. Literature data analysis and signal pathway reconstruction and reviewing revealed two possible mechanisms of peroxisome proliferator-activated receptors involvement in pathological anxiety: (1) cytokine expression and neuroinflammation mechanism and (2) regulation of peptidases targeted to anxiety-associated neuropeptides, primarily CCK-4, mechanism.

Long-Term Impact of Social Isolation and Molecular Underpinnings

Prolonged periods of social isolation can have detrimental effects on the physiology and behavior of exposed individuals in humans and animal models. This involves complex molecular mechanisms across tissues in the body which remain partly identified. This review discusses the biology of social isolation and describes the acute and lasting effects of prolonged periods of social isolation with a focus on the molecular events leading to behavioral alterations. We highlight the role of epigenetic mechanisms and non-coding RNA in the control of gene expression as a response to social isolation, and the consequences for behavior. Considering the use of strict quarantine during epidemics, like currently with COVID-19, we provide a cautionary tale on the indiscriminate implementation of such form of social isolation and its potential damaging and lasting effects in mental health.

The neuropeptide Drosulfakinin regulates social isolation-induced aggression in Drosophila

Social isolation strongly modulates behavior across the animal kingdom. We utilized the fruit fly Drosophila melanogaster to study social isolation-driven changes in animal behavior and gene expression in the brain. RNA-seq identified several head-expressed genes strongly responding to social isolation or enrichment. Of particular interest, social isolation downregulated expression of the gene encoding the neuropeptide Drosulfakinin (Dsk), the homologue of vertebrate cholecystokinin (CCK), which is critical for many mammalian social behaviors. Dsk knockdown significantly increased social isolation-induced aggression. Genetic activation or silencing of Dsk neurons each similarly increased isolation-driven aggression. Our results suggest a U-shaped dependence of social isolation-induced aggressive behavior on Dsk signaling, similar to the actions of many neuromodulators in other contexts.

Blockade of the cholecystokinin CCK-2 receptor prevents the normalization of anxiety levels in the rat

Cholecystokinin (CCK), through the CCK-2 receptor, exerts complex effects on anxiety. While CCK agonists are panicogenic, CCK-2 antagonists fail to alleviate human anxiety. Preclinical studies with CCK-2 antagonists are also inconsistent because their anxiolytic effects largely depend on the behavioral paradigm and antecedent stress. The controversy might be accounted by the neuromodulatory role for CCK in anxiety which is ill-defined. If this is its actual role, blocking CCK-2 will have carry-over effects on the anxiety baseline over time. To test this hypothesis, the consequences of acute administration of the CCK-2 antagonist Ly225.910 (0.1 mg Kg^-1) was evaluated in the temporal expression of aversion toward exploration-conflicting tasks. Ly225.910 effects were evaluated in rats exposed to the elevated plus-maze (EPM) twice, an approach-avoidance anxiety-like test. While LY225.910-treated rats had less anxiety than vehicle-treated rats, the difference was reversed during the EPM retest 24 h later without drug. Moreover, Ly225.910 effects in stress-induced cognitive impairment was measured giving the novel-object discrimination (NOD) test to rats not habituated to the exploration apparatus to elicit neophobia. After a first encounter with objects ("old"), Ly225.910-treated rats did not recognize the "novel" object introduced 6 h later. Ly225.910-exposed rats did not discriminate the new location of the "novel object" when it was repositioned in the arena 24 h later. Ly225.910-treated rats also failed to explore objects. In line with its neuromodulatory role, aversive carry-over effects of Ly225.910 suggest that CCK-2 activation by endogenous CCK, rather than triggering anxiety, may return the anxiety state to its normal level.

Pharmacotherapy of Anxiety Disorders: Current and Emerging Treatment Options

Anxiety disorders are the most prevalent psychiatric disorders and a leading cause of disability. While there continues to be expansive research in posttraumatic stress disorder (PTSD), depression and schizophrenia, there is a relative dearth of novel medications under investigation for anxiety disorders. This review's first aim is to summarize current pharmacological treatments (both approved and off-label) for panic disorder (PD), generalized anxiety disorder (GAD), social anxiety disorder (SAD), and specific phobias (SP), including selective serotonin reuptake inhibitors (SSRIs), serotonin norepinephrine reuptake inhibitors (SNRIs), azapirones (e.g., buspirone), mixed antidepressants (e.g., mirtazapine), antipsychotics, antihistamines (e.g., hydroxyzine), alpha- and beta-adrenergic medications (e.g., propranolol, clonidine), and GABAergic medications (benzodiazepines, pregabalin, and gabapentin). Posttraumatic stress disorder and obsessive-compulsive disorder are excluded from this review. Second, we will review novel pharmacotherapeutic agents under investigation for the treatment of anxiety disorders in adults. The pathways and neurotransmitters reviewed include serotonergic agents, glutamate modulators, GABAergic medications, neuropeptides, neurosteroids, alpha- and beta-adrenergic agents, cannabinoids, and natural remedies. The outcome of the review reveals a lack of randomized double-blind placebo- controlled trials for anxiety disorders and few studies comparing novel treatments to existing anxiolytic agents. Although there are some recent randomized controlled trials for novel agents including neuropeptides, glutamatergic agents (such as ketamine and d-cycloserine), and cannabinoids (including cannabidiol) primarily in GAD or SAD, these trials have largely been negative, with only some promise for kava and PH94B (an inhaled neurosteroid). Overall, the progression of current and future psychopharmacology research in anxiety disorders suggests that there needs to be further expansion in research of these novel pathways and larger-scale studies of promising agents with positive results from smaller trials.

Cholecystokinin immunoreactive neurons in the basolateral amygdala of the rhesus monkey (Macaca mulatta)

Several distinct subpopulations of interneurons (INs) in the amygdalar basolateral nuclear complex (BNC) of the rat can be recognized on the basis of their expression of calcium-binding proteins and neuropeptides, including parvalbumin (PV), somatostatin (SOM), calretinin (CR), and cholecystokinin (CCK). In the rat BNC CCK is expressed in two separate IN subpopulations, termed large (CCKL ) and small (CCKS ). These subpopulations exhibit distinct connections indicative of discrete functional roles in the circuitry of the BNC. Although there have been several studies of PV+, SOM+, and CR+ INs in the primate BNC, there is almost no information regarding CCK+ INs in these species. Therefore, in the present study the distribution and morphology of CCK+ INs and their axon terminals in the BNC of the monkey was investigated. CCK immunoreactivity in the BNC was observed in somata and proximal dendrites of nonpyramidal neurons, as well as in axon terminals. A moderate density of CCK+ INs was found in all nuclei of the BNC. CCK+ INs in the BNC were morphologically heterogeneous, with both small and large varieties observed. All CCK+ somata gave rise to 2-4 dendrites that branched sparingly and were aspiny. CCK+ axon terminals in the BNC were found both in the neuropil and forming pericellular baskets contacting somata of pyramidal cells. In addition, many CCK+ neurons were contacted by multiple CCK+ terminals, indicative of the existence of a CCK interneuronal network. These data indicate that the morphology of CCK+ INs in the monkey is very similar to that of the rat.

Neuropeptides at the crossroad of fear and hunger: a special focus on neuropeptide Y

Survival in a natural environment forces an individual into constantly adapting purposive behavior. Specified interoceptive neurons monitor metabolic and physiological balance and activate dedicated brain circuits to satisfy essential needs, such as hunger, thirst, thermoregulation, fear, or anxiety. Neuropeptides are multifaceted, central components within such life‐sustaining programs. For instance, nutritional depletion results in a drop in glucose levels, release of hormones, and activation of hypothalamic and brainstem neurons. These neurons, in turn, release several neuropeptides that increase food‐seeking behavior and promote food intake. Similarly, internal and external threats activate neuronal pathways of avoidance and defensive behavior. Interestingly, specific nuclei of the hypothalamus and extended amygdala are activated by both hunger and fear. Here, we introduce the relevant neuropeptides and describe their function in feeding and emotional‐affective behaviors. We further highlight specific pathways and microcircuits, where neuropeptides may interact to identify prevailing homeostatic needs and direct respective compensatory behaviors. A specific focus will be on neuropeptide Y, since it is known for its pivotal role in metabolic and emotional pathways. We hypothesize that the orexigenic and anorexigenic properties of specific neuropeptides are related to their ability to inhibit fear and anxiety.

A Novel Bio-Psychosocial-Behavioral Treatment Model of Panic Disorder

To conceptualize a novel bio-psychosocial-behavioral treatment model of panic disorder (PD), it is necessary to completely integrate behavioral, psychophysiological, neurobiological, and genetic data. Molecular genetic research on PD is specifically focused on neurotransmitters, including serotonin, neuropeptides, glucocorticoids, and neurotrophins. Although pharmacological interventions for PD are currently available, the need for more effective, faster-acting, and more tolerable pharmacological interventions is unmet. Thus, glutamatergic receptor modulators, orexin receptor antagonists, corticotrophin-releasing factor 1 receptor antagonists, and other novel mechanism-based anti-panic therapeutics have been proposed. Research on the neural correlates of PD is focused on the dysfunctional "cross-talk" between emotional drive (limbic structure) and cognitive inhibition (prefrontal cortex) and the fear circuit, which includes the amygdala-hippocampus-prefrontal axis. The neural perspective regarding PD supports the idea that cognitive-behavioral therapy normalizes alterations in top-down cognitive processing, including increased threat expectancy and attention to threat. Consistent with the concept of "personalized medicine," it is speculated that Research Domain Criteria can enlighten further treatments targeting dysfunctions underlying PD more precisely and provide us with better definitions of moderators used to identify subgroups according to different responses to treatment. Structuring of the "negative valence systems" domain, which includes fear/anxiety, is required to define PD. Therefore, targeting glutamate- and orexin-related molecular mechanisms associated with the fear circuit, which includes the amygdala-hippocampus-prefrontal cortex axis, is required to define a novel bio-psychosocial-behavioral treatment model of PD.

Fear Network Model in Panic Disorder: The Past and the Future

The core concept for pathophysiology in panic disorder (PD) is the fear network model (FNM). The alterations in FNM might be linked with disturbances in the autonomic nervous system (ANS), which is a common phenomenon in PD. The traditional FNM included the frontal and limbic regions, which were dysregulated in the feedback mechanism for cognitive control of frontal lobe over the primitive response of limbic system. The exaggerated responses of limbic system are also associated with dysregulation in the neurotransmitter system. The neuroimaging studies also corresponded to FNM concept. However, more extended areas of FNM have been discovered in recent imaging studies, such as sensory regions of occipital, parietal cortex and temporal cortex and insula. The insula might integrate the filtered sensory information via thalamus from the visuospatial and other sensory modalities related to occipital, parietal and temporal lobes. In this review article, the traditional and advanced FNM would be discussed. I would also focus on the current evidences of insula, temporal, parietal and occipital lobes in the pathophysiology. In addition, the white matter and functional connectome studies would be reviewed to support the concept of advanced FNM. An emerging dysregulation model of fronto-limbic-insula and temporooccipito-parietal areas might be revealed according to the combined results of recent neuroimaging studies. The future delineation of advanced FNM model can be beneficial from more extensive and advanced studies focusing on the additional sensory regions of occipital, parietal and temporal cortex to confirm the role of advanced FNM in the pathophysiology of PD.

Translocator protein 18kDa antagonist ameliorates stress-induced stool abnormality and abdominal pain in rodent stress models

BACKGROUND

Irritable bowel syndrome (IBS) is a functional gastrointestinal (GI) disorder characterized by abdominal pain and abnormal bowel habits, both of which are exacerbated by psychological stress. The translocator protein 18kDa (TSPO) is a marker of reactive gliosis in a number of central nervous system (CNS) diseases and responsible for many cellular functions, including neurosteroidogenesis. Although it has been reported that psychological stress disturbs neurosteroids levels, the pathophysiological relevance of TSPO in IBS is poorly understood.

METHODS

We examined the effects of a TSPO antagonist, ONO-2952, on stress-induced stool abnormality and abdominal pain in rats, and on anxiety-related behavior induced by cholecystokinin.

KEY RESULTS

Oral administration of ONO-2952 attenuated stress-induced defecation and rectal hyperalgesia in rats with an efficacy equivalent to that of a 5-HT₃ receptor antagonist. In addition, ONO-2952 suppressed cholecystokinin-induced anxiety-like behavior with an efficacy equivalent to that of psychotropic drugs. On the other hand, ONO-2952 did not affect spontaneous defecation, gastrointestinal transit, visceral nociceptive threshold, and neurosteroid production in non-stressed rats even at a dose 10 times higher than its effective dose in the stress models.

CONCLUSIONS AND INFERENCES

These results suggest that TSPO antagonism results in antistress action, and that ONO-2952 is a promising candidate for IBS without side effects associated with current treatment.

Cholecystokinin (CCK) level is higher among first time suicide attempters than healthy controls, but is not associated with higher depression scores

Suicide and suicide attempts are dramatic events for both the individuals concerned and for their social environments. Efforts have been made to identify reliable biological predictors of suicide and suicide attempts. In the present study, we focused on one potential marker, cholecystokinin (CCK), among first time suicide attempters. A total of 25 suicide attempters (mean age: 30 years; 80% females) and 23 healthy controls were enrolled in the present cross-sectional study. Experts rated participants' symptoms of depression (Hamilton Depression Rating Scale; HDRS). Blood levels of CCK levels were assessed. Suicide attempters had CCK levels 22.67 times higher and HDRS scores 14.33 higher than healthy controls. CCK levels were only weakly associated with HDRS scores. CCK appears to be a fairly reliable biomarker for suicide attempts. However, CCK levels were not associated with depression scores, making it difficult to match biological markers to depressive behaviour.

Imaging neuropeptide effects on human brain function

The discovery of prosocial effects of oxytocin (OT) opened new directions for studying neuropeptide effects on the human brain. However, despite obvious effects of OT on neural responses as reported in numerous studies, other peptides have received less attention. Therefore, we will only briefly summarize evidence of OT effects on human functional magnetic resonance imaging (fMRI) and primarily focus on OT's sister neuropeptide arginine-vasopressin by presenting our own coordinated-based activation likelihood estimation meta-analysis. In addition, we will recapitulate rather limited data on few other neuropeptides, including pharmacological and genetic fMRI studies. Finally, we will review experiments with external neuropeptide administration to patients afflicted with mental disorders, such as autism or schizophrenia. In conclusion, despite remaining uncertainty regarding the penetrance of exogenous neuropeptides through the blood-brain barrier, it is evident that neuropeptides simultaneously influence the activity of limbic and cortical areas, indicating that these systems have a good potential for therapeutic drug development. Hence, this calls for further systematic studies of a wide spectrum of known and less known neuropeptides to understand their normal function in the brain and, subsequently, to tackle their potential contribution for pathophysiological mechanisms of mental disorders.

Molecular bases of anorexia nervosa, bulimia nervosa and binge eating disorder: shedding light on the darkness

Eating-disorders (EDs) consequences to human health are devastating, involving social, mental, emotional, physical and life-threatening aspects, concluding on impairment and death in cases of extreme anorexia nervosa. It also implies that people suffering an ED need to find psychiatric and psychological help as soon as possible to achieve a fully physical and emotional recovery. Unfortunately, to date, there is a crucial lack of efficient clinical treatment to these disorders. In this review, we present an overview concerning the actual pharmacological and psychological treatments, the knowledge of cells, circuits, neuropeptides, neuromodulators and hormones in the human brain- and other organs- underlying these disorders, the studies in animal models and, finally, the genetic approaches devoted to face this challenge. We will also discuss the need for new perspectives, avenues and strategies to be developed in order to pave the way to novel and more efficient therapeutics.

Control of Food Intake by Gastrointestinal Peptides: Mechanisms of Action and Possible Modulation in the Treatment of Obesity

This review focuses on the control of appetite by food intake-regulatory peptides secreted from the gastrointestinal tract, namely cholecystokinin, glucagon-like peptide 1, peptide YY, ghrelin, and the recently discovered nesfatin-1 via the gut-brain axis. Additionally, we describe the impact of external factors such as intake of different nutrients or stress on the secretion of gastrointestinal peptides. Finally, we highlight possible conservative—physical activity and pharmacotherapy—treatment strategies for obesity as well as surgical techniques such as deep brain stimulation and bariatric surgery also altering these peptidergic pathways.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Neuropeptides as Regulators of Behavior in Insects

Neuropeptides are by far the largest and most diverse group of signaling molecules in multicellular organisms. They are ancient molecules important in regulating a multitude of processes. Their small proteinaceous character allowed them to evolve and radiate quickly into numerous different molecules. On average, hundreds of distinct neuropeptides are present in animals, sometimes with unique classes that do not occur in distantly related species. Acting as neurotransmitters, neuromodulators, hormones, or growth factors, they are extremely diverse and are involved in controlling growth, development, ecdysis, digestion, diuresis, and many more physiological processes. Neuropeptides are also crucial in regulating myriad behavioral actions associated with feeding, courtship, sleep, learning and memory, stress, addiction, and social interactions. In general, behavior ensures that an organism can survive in its environment and is defined as any action that can change an organism's relationship to its surroundings. Even though the mode of action of neuropeptides in insects has been vigorously studied, relatively little is known about most neuropeptides and only a few model insects have been investigated. Here, we provide an overview of the roles neuropeptides play in insect behavior. We conclude that multiple neuropeptides need to work in concert to coordinate certain behaviors. Additionally, most neuropeptides studied to date have more than a single function.

Biological markers for anxiety disorders, OCD and PTSD - a consensus statement. Part I: Neuroimaging and genetics

OBJECTIVES

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

METHODS

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

RESULTS

The present article (Part I) summarises findings on potential biomarkers in neuroimaging studies, including structural brain morphology, functional magnetic resonance imaging and techniques for measuring metabolic changes, including positron emission tomography and others. Furthermore, this review reports on the clinical and molecular genetic findings of family, twin, linkage, association and genome-wide association studies. Part II of the review focuses on neurochemistry, neurophysiology and neurocognition.

CONCLUSIONS

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

Ancient Anxiety Pathways Influence Drosophila Defense Behaviors

Anxiety helps us anticipate and assess potential danger in ambiguous situations [1, 2, 3]; however, the anxiety disorders are the most prevalent class of psychiatric illness [4, 5, 6]. Emotional states are shared between humans and other animals [7], as observed by behavioral manifestations [8], physiological responses [9], and gene conservation [10]. Anxiety research makes wide use of three rodent behavioral assays—elevated plus maze, open field, and light/dark box—that present a choice between sheltered and exposed regions [11]. Exposure avoidance in anxiety-related defense behaviors was confirmed to be a correlate of rodent anxiety by treatment with known anxiety-altering agents [12, 13, 14] and is now used to characterize anxiety systems. Modeling anxiety with a small neurogenetic animal would further aid the elucidation of its neuronal and molecular bases. Drosophila neurogenetics research has elucidated the mechanisms of fundamental behaviors and implicated genes that are often orthologous across species. In an enclosed arena, flies stay close to the walls during spontaneous locomotion [15, 16], a behavior proposed to be related to anxiety [17]. We tested this hypothesis with manipulations of the GABA receptor, serotonin signaling, and stress. The effects of these interventions were strikingly concordant with rodent anxiety, verifying that these behaviors report on an anxiety-like state. Application of this method was able to identify several new fly anxiety genes. The presence of conserved neurogenetic pathways in the insect brain identifies Drosophila as an attractive genetic model for the study of anxiety and anxiety-related disorders, complementing existing rodent systems.

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Drosophila orthologs of anxiety genes affect fly wall following

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Conserved anxiety genes influence fly defense behaviors similarly to mouse anxiety

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New candidate anxiety genes are identified from fly defense behavior screen

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Drosophila identified as a new neurogenetic tool for anxiety research

Neuropeptide S receptor gene variation modulates anterior cingulate cortex Glx levels during CCK-4 induced panic

An excitatory-inhibitory neurotransmitter dysbalance has been suggested in pathogenesis of panic disorder. The neuropeptide S (NPS) system has been implicated in modulating GABA and glutamate neurotransmission in animal models and to genetically drive altered fear circuit function and an increased risk of panic disorder in humans. Probing a multi-level imaging genetic risk model of panic, in the present magnetic resonance spectroscopy (MRS) study brain glutamate+glutamine (Glx) levels in the bilateral anterior cingulate cortex (ACC) during a pharmacological cholecystokinin tetrapeptide (CCK-4) panic challenge were assessed depending on the functional neuropeptide S receptor gene (NPSR1) rs324981 A/T variant in a final sample of 35 healthy male subjects. The subjective panic response (Panic Symptom Scale; PSS) as well as cortisol and ACTH levels were ascertained throughout the experiment. CCK-4 injection was followed by a strong panic response. A significant time×genotype interaction was detected (p=.008), with significantly lower ACC Glx/Cr levels in T allele carriers as compared to AA homozygotes 5min after injection (p=.003). CCK-4 induced significant HPA axis stimulation, but no effect of genotype was discerned. The present pilot data suggests NPSR1 gene variation to modulate Glx levels in the ACC during acute states of stress and anxiety, with blunted, i.e. possibly maladaptive ACC glutamatergic reactivity in T risk allele carriers. Our results underline the notion of a genetically driven rapid and dynamic response mechanism in the neural regulation of human anxiety and further strengthen the emerging role of the NPS system in anxiety.

ZNF804A Transcriptional Networks in Differentiating Neurons Derived from Induced Pluripotent Stem Cells of Human Origin

ZNF804A (Zinc Finger Protein 804A) has been identified as a candidate gene for schizophrenia (SZ), autism spectrum disorders (ASD), and bipolar disorder (BD) in replicated genome wide association studies (GWAS) and by copy number variation (CNV) analysis. Although its function has not been well-characterized, ZNF804A contains a C2H2-type zinc-finger domain, suggesting that it has DNA binding properties, and consequently, a role in regulating gene expression. To further explore the role of ZNF804A on gene expression and its downstream targets, we used a gene knockdown (KD) approach to reduce its expression in neural progenitor cells (NPCs) derived from induced pluripotent stem cells (iPSCs). KD was accomplished by RNA interference (RNAi) using lentiviral particles containing shRNAs that target ZNF804A mRNA. Stable transduced NPC lines were generated after puromycin selection. A control cell line expressing a random (scrambled) shRNA was also generated. Neuronal differentiation was induced, RNA was harvested after 14 days and transcriptome analysis was carried out using RNA-seq. 1815 genes were found to be differentially expressed at a nominally significant level (p<0.05); 809 decreased in expression in the KD samples, while 1106 increased. Of these, 370 achieved genome wide significance (FDR<0.05); 125 were lower in the KD samples, 245 were higher. Pathway analysis showed that genes involved in interferon-signaling were enriched among those that were down-regulated in the KD samples. Correspondingly, ZNF804A KD was found to affect interferon-alpha 2 (IFNA2)-mediated gene expression. The findings suggest that ZNF804A may affect a differentiating neuron’s response to inflammatory cytokines, which is consistent with models of SZ and ASD that support a role for infectious disease, and/or autoimmunity in a subgroup of patients.

Functional synergy between cholecystokinin receptors CCKAR and CCKBR in mammalian brain development

Cholecystokinin (CCK), a peptide hormone and one of the most abundant neuropeptides in vertebrate brain, mediates its actions via two G-protein coupled receptors, CCKAR and CCKBR, respectively active in peripheral organs and the central nervous system. Here, we demonstrate that the CCK receptors have a dynamic and largely reciprocal expression in embryonic and postnatal brain. Using compound homozygous mutant mice lacking the activity of both CCK receptors, we uncover their additive, functionally synergistic effects in brain development and demonstrate that CCK receptor loss leads to abnormalities of cortical development, including defects in the formation of the midline and corpus callosum, and cortical interneuron migration. Using comparative transcriptome analysis of embryonic neocortex, we define the molecular mechanisms underlying these defects. Thus we demonstrate a developmental, hitherto unappreciated, role of the two CCK receptors in mammalian neocortical development.

Arousal and the attentional network in panic disorder

Although a great deal of information about the neurobiology of panic disorder is now available, there is a need for an updated etiological model integrating recent findings on the neurobiology of the arousal system and its relationship with higher cortical functions in panic disorder. The current mini-review presents psychophysiological, molecular biological/genetic and functional neuroimaging evidence for dysfunction in major arousal systems of the brain. Such dysfunction may influence the development of panic disorder by precipitating autonomic bodily symptoms and at the same time increasing vigilance to these sensations by modulating cortical attentional networks. A multilevel model of arousal, attention and anxiety-including the norepinephrine, orexin, neuropeptide S and caffeine-related adenosine systems-may be useful in integrating a range of data available on the pathogenesis of panic disorder.

Challenges and recent advances in mass spectrometric imaging of neurotransmitters

Mass spectrometric imaging (MSI) is a powerful tool that grants the ability to investigate a broad mass range of molecules, from small molecules to large proteins, by creating detailed distribution maps of selected compounds. To date, MSI has demonstrated its versatility in the study of neurotransmitters and neuropeptides of different classes toward investigation of neurobiological functions and diseases. These studies have provided significant insight in neurobiology over the years and current technical advances are facilitating further improvements in this field. Herein, we briefly review new MSI studies of neurotransmitters, focusing specifically on the challenges and recent advances of MSI of neurotransmitters.

Local corticotropin releasing hormone (CRH) signals to its receptor CRHR1 during postnatal development of the mouse olfactory bulb

Neuropeptides play important physiological functions during distinct behaviors such as arousal, learning, memory, and reproduction. However, the role of local, extrahypothalamic neuropeptide signaling in shaping synapse formation and neuronal plasticity in the brain is not well understood. Here, we characterize the spatiotemporal expression profile of the neuropeptide corticotropin-releasing hormone (CRH) and its receptor CRHR1 in the mouse OB throughout development. We found that CRH-expressing interneurons are present in the external plexiform layer, that its cognate receptor is expressed by granule cells, and show that both CRH and CRHR1 expression enriches in the postnatal period when olfaction becomes important towards olfactory-related behaviors. Further, we provide electrophysiological evidence that CRHR1-expressing granule cells functionally respond to CRH ligand, and that the physiological circuitry of CRHR1 knockout mice is abnormal, leading to impaired olfactory behaviors. Together, these data suggest a physiologically relevant role for local CRH signaling towards shaping the neuronal circuitry within the mouse OB.

Neuroendocrine circuits governing energy balance and stress regulation: functional overlap and therapeutic implications

Significant comorbidities between obesity-related metabolic disease and stress-related psychological disorders suggest important functional interactions between energy balance and brain stress integration. Largely overlapping neural circuits control these systems, and this anatomical arrangement optimizes opportunities for mutual influence. Here we first review the current literature identifying effects of metabolic neuroendocrine signals on stress regulation, and vice versa. Next, the contributions of reward-driven food intake to these metabolic and stress interactions are discussed. Lastly, we consider the interrelationships between metabolism, stress, and reward in light of their important implications in the development of therapies for metabolism- or stress-related disease.

Acute effects on brain cholecystokinin-like concentration and anxiety-like behaviour in the female rat upon a single injection of 17β-estradiol

BACKGROUND

The neuropeptide cholecystokinin (CCK) has been implicated in the neurobiology of anxiety and panic disorders, as well as in dopamine-related behaviours. Anxiety and panic-disorders are twice as common in females compared to males, but studies of females are rare, although increasing in number. Limited studies have found that CCK fluctuates in limbic regions during the estrous cycle, and that CCK and its receptors are sensitive to estrogen.

AIM/PURPOSE

The aim of the present work was to study the acute effects of 17β-estradiol on anxiety-like behaviour and on CCK-like immunoreactivity (LI) in the female rat brain (amygdala, hippocampus, nucleus accumbens, and cingulate cortex).

METHODS

Four groups of female Sprague-Dawley rats were used: ovariectomized, ovariectomized+17β-estradiol-replacement, sham, and sham+17β-estradiol-replacement. The effect of 17β-estradiol-replacement on anxiety-related behaviour was measured in all animals on the elevated plus maze 2-24 h after injection. CCK-LI concentration was measured in punch biopsies by means of radioimmunoassay.

RESULTS

17β-estradiol decreased anxiety-like behaviour 2 h after administration in ovariectomized and sham-operated animals, as demonstrated by increased exploration of the open arms compared to respective sesame oil-treated controls. This effect was not present when testing occurred 24 h post-treatment. The rapid behavioural effect of 17β-estradiol was accompanied by changes in CCK-LI concentrations in regions of the limbic system including cingulate cortex, hippocampus, amygdala and nucleus accumbens.

CONCLUSION

Although the interpretation of these data requires caution since the data were collected from two different experiments, our results suggest that estrogen-induced anxiolytic effects may be associated with changes of the CCK-system in brain regions controlling anxiety-like behaviour.

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.

Cholecystokinin-Like Peptide (DSK) in Drosophila, Not Only for Satiety Signaling

Cholecystokinin (CCK) signaling appears well conserved over evolution. In Drosophila, the CCK-like sulfakinins (DSKs) regulate aspects of gut function, satiety and food ingestion, hyperactivity and aggression, as well as escape-related locomotion and synaptic plasticity during neuromuscular junction development. Activity in the DSK-producing neurons is regulated by octopamine. We discuss mechanisms behind CCK function in satiety, aggression, and locomotion in some detail and highlight similarities to mammalian CCK signaling.

Stress and eating: a dual role for bombesin-like peptides

The current obesity “epidemic” in the developed world is a major health concern; over half of adult Canadians are now classified as overweight or obese. Although the reasons for high obesity rates remain unknown, an important factor appears to be the role stressors play in overconsumption of food and weight gain. In this context, increased stressor exposure and/or perceived stress may influence eating behavior and food choices. Stress-induced anorexia is often noted in rats exposed to chronic stress (e.g., repeated restraint) and access to standard Chow diet; associated reduced consumption and weight loss. However, if a similar stressor exposure takes place in the presence of palatable, calorie dense food, rats often consume an increase proportion of palatable food relative to Chow, leading to weight gain and obesity. In humans, a similar desire to eat palatable or “comfort” foods has been noted under stressful situations; it is thought that this response may potentially be attributable to stress-buffering properties and/or through activation of reward pathways. The complex interplay between stress-induced anorexia and stress-induced obesity is discussed in terms of the overlapping circuitry and neurochemicals that mediate feeding, stress and reward pathways. In particular, this paper draws attention to the bombesin family of peptides (BBs) initially shown to regulate food intake and subsequently shown to mediate stress response as well. Evidence is presented to support the hypothesis that BBs may be involved in stress-induced anorexia under certain conditions, but that the same peptides could also be involved in stress-induced obesity. This hypothesis is based on the unique distribution of BBs in key cortico-limbic brain regions involved in food regulation, reward, incentive salience and motivationally driven behavior.

Regulation of aggression by obesity-linked genes TfAP-2 and Twz through octopamine signaling in Drosophila

In Drosophila, the monoamine octopamine, through mechanisms that are not completely understood, regulates both aggression and mating behavior. Interestingly, our study demonstrates that the Drosophila obesity-linked homologs Transcription factor AP-2 (TfAP-2; TFAP2B in humans) and Tiwaz (Twz; KCTD15 in humans) interact to modify male behavior by controlling the expression of Tyramine β-hydroxylase and Vesicular monanime transporter, genes necessary for octopamine production and secretion. Furthermore, we reveal that octopamine in turn regulates aggression through the Drosophila cholecystokinin satiation hormone homolog Drosulfakinin (Dsk). Finally, we establish that TfAP-2 is expressed in octopaminergic neurons known to control aggressive behavior and that TfAP-2 requires functional Twz for its activity. We conclude that genetically manipulating the obesity-linked homologs TfAP-2 and Twz is sufficient to affect octopamine signaling, which in turn modulates Drosophila male behavior through the regulation of the satiation hormone Dsk.

Interaction between cholecystokinin and the fibroblast growth factor system in the ventral tegmental area of selectively bred high- and low-responder rats

Individual differences in the locomotor response to novelty have been linked to basal differences in dopaminergic neurotransmission. Mesolimbic dopaminergic outputs are regulated by cholecystokinin (CCK), a neuropeptide implicated in anxiety. In turn, CCK expression is regulated by fibroblast growth factor-2 (FGF2), which has recently been identified as an endogenous regulator of anxiety. FGF2 binds to the high-affinity fibroblast growth factor receptor-1 (FGF-R1) to regulate the development and maintenance of dopamine neurons in the ventral tegmental area (VTA). However, the relationship between the FGF and CCK systems in the VTA is not well understood. Therefore, we utilized the selectively-bred low-responder (bLR; high-anxiety) and high-responder (bHR; low-anxiety) rats to examine the effects of repeated (21-day) FGF2 treatment on CCK and FGF-R1 mRNA in the rostral VTA (VTAr). In vehicle-treated controls, both CCK and FGF-R1 mRNA levels were increased in the VTAr of bLR rats relative to bHR rats. Following FGF2 treatment, however, bHR-bLR differences in CCK and FGF-R1 mRNA expression were eliminated, due to decreased CCK mRNA levels in the VTAr of bLR rats and increased FGF-R1 expression in bHR rats. Differences after FGF2 treatment may denote distinct interactions between the CCK and FGF systems in the VTAr of bHR vs. bLR rats. Indeed, significant correlations between CCK and FGF-R1 mRNA expression were found in bHR, but not bLR rats. Colocalization studies suggest that CCK and FGF-R1 are coexpressed in some VTAr neurons. Taken together, our findings suggest that the FGF system is poised to modulate both CCK and FGF-R1 expression in the VTAr, which may be associated with individual differences in mesolimbic pathways associated with anxiety-like behavior.

How might circadian rhythms control mood? Let me count the ways

Mood disorders are serious diseases that affect a large portion of the population. There have been many hypotheses put forth over the years to explain the development of major depression, bipolar disorder, and other mood disorders. These hypotheses include disruptions in monoamine transmission, hypothalamus-pituitary-adrenal axis function, immune function, neurogenesis, mitochondrial dysfunction, and neuropeptide signaling (to name a few). Nearly all people suffering from mood disorders have significant disruptions in circadian rhythms and the sleep/wake cycle. In fact, altered sleep patterns are one of the major diagnostic criteria for these disorders. Moreover, environmental disruptions to circadian rhythms, including shift work, travel across time zones, and irregular social schedules, tend to precipitate or exacerbate mood-related episodes. Recent studies have found that molecular clocks are found throughout the brain and body where they participate in the regulation of most physiological processes, including those thought to be involved in mood regulation. This review will summarize recent data that implicate the circadian system as a vital regulator of a variety of systems that are thought to play a role in the development of mood disorders.