Cerebrospinal fluid corticotropin-releasing factor concentrations in patients with anxiety disorders and normal comparison subjects

Preconception ethanol exposure changes anxiety, depressive and checking-like behavior and alter the expression levels of MAO-B in male offspring

Alcohol use, which alters the epigenome, increases the probability that it could affect subsequent generations, even if they were never directly exposed to ethanol or even in utero. We explored the effects of parental ethanol exposure before conception on behavioral changes in the offspring. Considering the role of Monoamine oxidase-B (MAO-B) in dopamine turnover in the prefrontal cortex (PFC) and its influence on behavior, and taking into account that ethanol exposure could alter MAO-B, we assessed the protein levels in the offspring. Male and female rats were exposed to ethanol for 30 days and then allowed ten days of abstinence. Afterward, they were mated with either control or ethanol-exposed rats. The F1 and F2 male offspring underwent tests to assess behavioral changes. Additionally, the levels of MAO-B in the PFC were evaluated. Results revealed that in the F1, anxiety increased only in the bi-parental ethanol-exposed male offspring in the elevated plus maze test (p < 0.05), while depressive-like behavior rose only in maternal and bi-parental ethanol-exposed offspring (p < 0.01). However, compulsive-like behavior increased in all ethanol-exposed offspring (p < 0.01). No significant phenotypic changes were observed in the F2. The levels of MAO-B in the PFC increased in the maternal (p < 0.05) and bi-parental ethanol-exposed offspring (p < 0.01). Our study demonstrates that parental ethanol exposure, even in the days preceding mating, adversely affects behaviors and induces molecular changes in the brain. Given these findings, it becomes imperative to monitor children exposed to parental (especially maternal) ethanol for the prevention of mental disorders.

Cerebrospinal fluid findings in patients with obsessive-compulsive disorder, Tourette syndrome, and PANDAS: A systematic literature review

BACKGROUND

Obsessive-compulsive disorder (OCD) and Tourette syndrome (TS) are related mental disorders that share genetic, neurobiological, and phenomenological features. Pediatric autoimmune neuropsychiatric disorder associated with streptococcal infections (PANDAS) is a neuropsychiatric autoimmune disorder with symptoms of OCD and/or TS associated with streptococcal infections. Therefore, PANDAS represents a strong link between OCD, TS, and autoimmunity. Notably, cerebrospinal fluid (CSF) analyses can provide insight into the central nervous processes in OCD, TS, and PANDAS.

METHODS

A systematic literature search according to the PRISMA criteria was conducted to collect all CSF studies in patients with OCD, TS, and PANDAS. The total number of cases and the heterogeneity of the low number of studies were not sufficient for a meta-analysis to provide a high level of evidence. Nevertheless, meta-analytical statistics could be performed for glutamate, 5-hydroxyindoleacetic acid (degradation product of serotonin), homovanillic acid (degradation product of dopamine), 3-methoxy-4-hydroxyphenylglycol (major metabolite of noradrenaline), and corticotropin-releasing hormone (CRH) in OCD. A risk-of-bias assessment was implemented using the Cochrane ROBINS-E tool.

RESULTS

Meta-analytical testing identified elevated glutamate levels in the CSF of OCD patients compared with healthy controls, while no significant differences were found in other neurotransmitters or CRH. Single studies detected novel neuronal antibodies in OCD patients and elevated oligoclonal bands in TS patients. For TS and PANDAS groups, there was a dearth of data. Risk of bias assessment indicated a substantial risk of bias in most of the included studies.

CONCLUSIONS

This systematic review of available CSF data shows that too few studies are currently available for conclusions with good evidence. The existing data indicates glutamate alterations in OCD and possible immunological abnormalities in OCD and TS. More CSF studies avoiding sources of bias are needed.

Corticotropin-releasing factor signaling and its potential role in the prefrontal cortex-dependent regulation of anxiety

A large body of literature has highlighted the significance of the corticotropin-releasing factor (CRF) system in the regulation of neuropsychiatric diseases. Anxiety disorders are among the most common neuropsychiatric disorders. An increasing number of studies have demonstrated that the CRF family mediates and regulates the development and maintenance of anxiety. Thus, the CRF family is considered to be a potential target for the treatment of anxiety disorders. The prefrontal cortex (PFC) plays a role in the occurrence and development of anxiety, and both CRF and CRF-R1 are widely expressed in the PFC. This paper begins by reviewing CRF-related signaling pathways and their different roles in anxiety and related processes. Then, the role of the CRF system in other neuropsychiatric diseases is reviewed and the potential role of PFC CRF signaling in the regulation of anxiety disorders is discussed. Although other signaling pathways are potentially involved in the process of anxiety, CRF in the PFC primarily modulates anxiety disorders through the activation of corticotropin-releasing factor type1 receptors (CRF-R1) and the excitation of the cAMP/PKA signaling pathway. Moreover, the main signaling pathways of CRF involved in sex differentiation in the PFC appear to be different. In summary, this review suggests that the CRF system in the PFC plays a critical role in the occurrence of anxiety. Thus, CRF signaling is of great significance as a potential target for the treatment of stress-related disorders in the future.

The hypothalamus in anxiety disorders

Of all mental disorders, anxiety disorders are currently the strongest contributors to the global burden of disease, with 7.3% of the general population affected worldwide. The hypothalamus is crucial hub of a network of neural structures modulating fear conditioning and extinction and, as such, highly relevant to the pathophysiology of these conditions. Three hypothalamic systems have emerged as particularly relevant in this context. First, the oxytocin system is highly likely to be involved anxiety disorders and in particular in the cognitive and behavioral deficits pertaining to social anxiety disorder. Second, peripheral markers of the hypothalamic-pituitary-adrenal axis appear altered in patients with panic disorder and generalized anxiety disorder, which may denote aberrant functioning of their central corticotropin-releasing hormone system. Furthermore, cortisol seems to augment the effects of exposure therapy in patients with specific phobia. Third, the integrity of the hypothalamic-pituitary-thyroid axis is likely compromised in panic disorder. Further, cross-disciplinary research efforts are required to shed more light on how, exactly, these hypothalamic systems interact with the neural structures involved in fear conditioning and extinction, which should ultimately open up new avenues for the prevention and treatment of anxiety disorders.

Pharmacological Treatment of Anxiety Disorders: The Role of the HPA Axis

Stress in general, and early life stress in particular, has been associated with the development of anxiety and mood disorders. The molecular, biological and psychological links between stress exposure and the pathogenesis of anxiety and mood disorders have been extensively studied, resulting in the search of novel psychopharmacological strategies aimed at targets of the hypothalamic-pituitary-adrenal (HPA) axis. Hyperactivity of the HPA axis has been observed in certain subgroups of patients with anxiety and mood disorders. In addition, the effects of different anti-anxiety agents on various components of the HPA axis has been investigated, including benzodiazepines, tricyclic antidepressants (TCAs), and selective serotonin reuptake inhibitors (SSRIs). For example, benzodiazepines, including clonazepam and alprazolam, have been demonstrated to reduce the activity of corticotrophin releasing factor (CRF) neurons in the hypothalamus. TCAs and SSRIs are also effective anti-anxiety agents and these may act, in part, by modulating the HPA axis. In this regard, the SSRI escitalopram inhibits CRF release in the central nucleus of the amygdala, while increasing glucocorticoid receptor (GRs) density in the hippocampus and hypothalamus. The molecular effects of these anti-anxiety agents in the regulation of the HPA axis, taken together with their clinical efficacy, may provide further understanding about the role of the HPA axis in the pathophysiology of mood and anxiety disorders, paving the way for the development of novel therapeutic strategies.

Sex-specific association between the cortisol awakening response and obsessive-compulsive symptoms in healthy individuals

Background

Previous studies have shown associations between obsessive-compulsive disorder (OCD) and hypothalamic-pituitary-adrenal axis activity (HPA). We aimed to investigate the association between obsessive-compulsive (OC) symptoms and HPA axis functionality in a non-clinical sample and to explore whether there are sex differences in this relationship.

Methods

One hundred eighty-three healthy individuals without any psychiatric diagnosis (80 men, 103 women; mean age 41.3 ± 17.9 years) were recruited from the general population. The Obsessive-Compulsive Inventory Revised (OCI-R) was used to assess OC symptoms. State-trait anxiety, perceived stress, and stressful life events were also assessed. Saliva cortisol levels were determined at 6 time points (awakening, 30 and 60 min post-awakening, 10:00 a.m., 23:00 p.m. and 10:00 a.m. the following day of 0.25 mg dexamethasone intake [that occurred at 23:00 p.m.]). Three HPA axis measures were calculated: cortisol awakening response (CAR), cortisol diurnal slope, and cortisol suppression ratio after dexamethasone (DSTR). Multiple linear regression analyses were used to explore the association between OC symptoms and HPA axis measures while adjusting for covariates. Our main analyses were focused on OCI-R total score, but we also explored associations with specific OC symptom dimensions.

Results

No significant differences were observed between males and females in OC symptoms, anxiety measures, stress, or cortisol measures. In the multiple linear regression analyses between overall OC symptoms and HPA axis measures, a female sex by OC symptoms significant interaction (standardized beta = − 0.322; p = 0.023) for the CAR (but not cortisol diurnal slope nor DSTR) was found. Regarding specific symptom dimensions, two other sex interactions were found: a blunted CAR was associated with obsessing symptoms in women, whereas a more flattened diurnal cortisol slope was associated with ordering symptoms in men.

Conclusions

There are sex differences in the association between OC symptoms and HPA axis measures in healthy individuals.

The CRF Family of Neuropeptides and their Receptors - Mediators of the Central Stress Response

Background:

Dysregulated stress neurocircuits, caused by genetic and/or environmental changes, underlie the development of many neuropsychiatric disorders. Corticotropin-releasing factor (CRF) is the major physiological activator of the hypothalamic-pituitary-adrenal (HPA) axis and conse-quently a primary regulator of the mammalian stress response. Together with its three family members, urocortins (UCNs) 1, 2, and 3, CRF integrates the neuroendocrine, autonomic, metabolic and behavioral responses to stress by activating its cognate receptors CRFR1 and CRFR2.

Objective:

Here we review the past and current state of the CRF/CRFR field, ranging from pharmacologi-cal studies to genetic mouse models and virus-mediated manipulations.

Results:

Although it is well established that CRF/CRFR1 signaling mediates aversive responses, includ-ing anxiety and depression-like behaviors, a number of recent studies have challenged this viewpoint by revealing anxiolytic and appetitive properties of specific CRF/CRFR1 circuits. In contrast, the UCN/CRFR2 system is less well understood and may possibly also exert divergent functions on physiol-ogy and behavior depending on the brain region, underlying circuit, and/or experienced stress conditions.

Conclusion:

A plethora of available genetic tools, including conventional and conditional mouse mutants targeting CRF system components, has greatly advanced our understanding about the endogenous mecha-nisms underlying HPA system regulation and CRF/UCN-related neuronal circuits involved in stress-related behaviors. Yet, the detailed pathways and molecular mechanisms by which the CRF/UCN-system translates negative or positive stimuli into the final, integrated biological response are not completely un-derstood. The utilization of future complementary methodologies, such as cell-type specific Cre-driver lines, viral and optogenetic tools will help to further dissect the function of genetically defined CRF/UCN neurocircuits in the context of adaptive and maladaptive stress responses.

Exercise training with concomitant nitric oxide synthase inhibition improved anxiogenic behavior, spatial cognition, and BDNF/P70S6 kinase activation in 20-month-old rats

This study aimed to investigate the effect of exercise and nitric oxide synthase (NOS) inhibition on memory, anxiety, and protein levels of brain-derived neurotrophic factor (BDNF) and P70S6 kinase (P70S6K). Twenty-month-old rats were divided into 6 groups: a control group, 2 groups treated with l-nitro-arginine methyl ester (L-NAME) (25 or 100 mg/kg) for 63 days, 2 groups treated with L-NAME (25 or 100 mg/kg) for 63 days plus 2 months of exercise, and 1 group treated with exercise. Behavioral tests were conducted to determine the anxiolytic and memory-improving role of exercise and NOS inhibition. BDNF, P70S6K, and cleaved caspase-3 protein levels in the hippocampus and prefrontal cortex were evaluated by Western blotting. Exercise and L-NAME (25 mg/kg) or their combination had an anxiolytic effect and improved spatial memory in old rats compared with the control or exercised group, respectively. Exercise and treatment with a low dose of L-NAME (25 mg/kg) each increased BDNF and P70S6K in the hippocampus and prefrontal cortex compared with levels in control rats. In comparison with exercise alone, co-treatment with exercise and a low dose of L-NAME (25 mg/kg) also increased BDNF and P70S6K in the hippocampus. The neuronal level of cleaved caspase-3 was reduced in the L-NAME (25 mg/kg) + exercise group compared with the exercised group. The L-NAME (100 mg/kg) + exercise treatment had no positive behavioral or molecular effects compared with exercise alone. The protective role of NOS inhibition and aerobic exercise against aging is probably modulated via BDNF and P70S6K in the brain.

Inflammation in Fear- and Anxiety-Based Disorders: PTSD, GAD, and Beyond

The study of inflammation in fear- and anxiety-based disorders has gained interest as growing literature indicates that pro-inflammatory markers can directly modulate affective behavior. Indeed, heightened concentrations of inflammatory signals, including cytokines and C-reactive protein, have been described in posttraumatic stress disorder (PTSD), generalized anxiety disorder (GAD), panic disorder (PD), and phobias (agoraphobia, social phobia, etc.). However, not all reports indicate a positive association between inflammation and fear- and anxiety-based symptoms, suggesting that other factors are important in future assessments of inflammation's role in the maintenance of these disorders (ie, sex, co-morbid conditions, types of trauma exposure, and behavioral sources of inflammation). The most parsimonious explanation of increased inflammation in PTSD, GAD, PD, and phobias is via the activation of the stress response and central and peripheral immune cells to release cytokines. Dysregulation of the stress axis in the face of increased sympathetic tone and decreased parasympathetic activity characteristic of anxiety disorders could further augment inflammation and contribute to increased symptoms by having direct effects on brain regions critical for the regulation of fear and anxiety (such as the prefrontal cortex, insula, amygdala, and hippocampus). Taken together, the available data suggest that targeting inflammation may serve as a potential therapeutic target for treating these fear- and anxiety-based disorders in the future. However, the field must continue to characterize the specific role pro-inflammatory signaling in the maintenance of these unique psychiatric conditions.

The CRF System as a Therapeutic Target for Neuropsychiatric Disorders

The major neuropsychiatric disorders are devastating illnesses that are only modestly responsive to treatment. Improving the treatment of these conditions will require innovative new strategies that depart from previously focused-on pharmacological mechanisms. Considerable preclinical and clinical data indicate corticotropin-releasing factor (CRF) signaling as a target for new psychotropic drug development. Here we review alterations in the CRF system reported in several psychiatric conditions. We also examine the preclinical work that has dissected the distinctive roles of CRF receptors in specific circuits relevant to these disorders. We further describe the clinical trials of CRF1 receptor antagonists that have been conducted. Although these clinical trials have thus far met with limited therapeutic success, the unfolding complexity of the CRF system promises many future directions for studying its role in the etiology and treatment of neuropsychiatric conditions.

Effects of intracerebroventricular corticotropin releasing factor on sensory-evoked responses in the rat visual thalamus

Corticotropin releasing factor (CRF) coordinates the brain׳s responses to stress. Recent evidence suggests that CRF-mediated activation of the locus coeruleus-norepinephrine (LC-NE) system contributes to alterations in sensory signal processing during stress. However, it remains unclear whether these actions are dependent upon the degree of CRF release. Using intracerebroventricular (ICV) infusions, we examine the dose-dependent actions of CRF on sensory-evoked discharges of neurons in the dorsal lateral geniculate nucleus of the thalamus (dLGN). The LGN is the primary relay for visual signals from retina to cortex, receiving noradrenergic modulation from the LC. In vivo extracellular recording in anesthetized rats was used to monitor single dLGN neuron responses to light flashes at three different stimulus intensities before and after administration of CRF (0.1, 0.3, 1.0, 3.0 or 10.0 μg). CRF produced three main effects on dLGN stimulus evoked activity: (1) increased magnitude of sensory evoked discharges at moderate doses, (2) decreased response latency, and (3) dose-dependent increases in the number of cells responding to a previously sub-threshold (low intensity) stimulus. These modulatory actions were blocked or attenuated by intra-LC infusion of a CRF antagonist prior to ICV CRF administration. Moreover, intra-LC administration of CRF (10 ng) mimicked the facilitating effects of moderate doses of ICV CRF on dLGN neuron responsiveness to light stimuli. These findings suggest that stressor-induced changes in sensory signal processing cannot be defined in terms of a singular modulatory effect, but rather are multi-dimensional and dictated by variable degrees of activation of the CRF-LC-NE system.

Differential effects of acute morphine, and chronic morphine-withdrawal on obsessive-compulsive behavior: inhibitory influence of CRF receptor antagonists on chronic morphine-withdrawal

Recent studies have provided convincing evidences for co-morbidity between opioid addiction and obsessive-compulsive disorder (OCD), and the involvement of the corticotrophin-releasing factor (CRF) in the effects of morphine-withdrawal. Some scanty evidences also point towards the role of CRF in OCD and related disorders. But, no evidence indicated the role of CRF in morphine withdrawal associated obsessive-compulsive behavior (OCB). Therefore, the present study investigated the role of CRF in morphine-withdrawal induced OCB in mice. Marble-burying behavior in mice was used to assess OCB as this model has good predictive and face validity. The results revealed that acute morphine dose dependently attenuated the marble burying behavior, whereas withdrawal of chronic morphine was associated with significant rise in marble burying behavior. This indicates the differential effect of acute morphine and chronic morphine-withdrawal on OCB. Further, acute treatment with CRF receptor antagonists like antalarmin (2 and 4 μg/mouse, i.c.v.) or astressin-2B (3 and 10 nmol/mouse, i.c.v.) dose dependently attenuated the peak morphine-withdrawal induced increase in marble burying behavior. Moreover, concomitant treatment with antalarmin (4 μg/mouse, i.c.v.) or astressin-2B (10 nmol/mouse, i.c.v.) along with morphine blocked the morphine-withdrawal associated exacerbation of OCB. These results indicate that OCB associated with morphine withdrawal state is partly mediated by the activation of central CRF receptors.

Chronic overexpression of corticotropin-releasing factor from the central amygdala produces HPA axis hyperactivity and behavioral anxiety associated with gene-expression changes in the hippocampus and paraventricular nucleus of the hypothalamus

Environmental stress has been demonstrated to increase susceptibility for mood and anxiety disorders, and hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis, the primary endocrine response to stress, is often observed in these patients. HPA axis activation is initiated by corticotropin-releasing factor (CRF) from the hypothalamus, leading to the hypothesis that hypothalamic CRF overexpression contributes to HPA axis hyperactivity in psychiatric patients. In addition, elevated CRF in cerebrospinal fluid is observed in mood and anxiety disorder patients, suggesting that CRF is also being overproduced from extrahypothalamic sources such as the central amygdala (CeA) and overactivity of the amygdala in neuroimaging studies is a consistent finding in anxiety and depression patients. Due to the importance of CRF and the amygdala in the etiology of stress-sensitive psychiatric disorders, the present study sought to further dissect the impact of CRF overexpression (OE) in the amygdala on downstream behavioral, endocrine, and gene-expression changes typically associated with chronic stress. To test the hypothesis that elevated CRF output from the amygdala would reproduce HPA axis hyperactivity and behavioral symptoms of chronic stress, we developed a lentiviral vector in which 3.0kb of the CRF promoter drives overexpression of CRF (LVCRFp3.0CRF). In adult male rats, Experiment-1 examined behavioral consequences of chronic CRF overexpression from the amygdala; the dexamethasone (Dex)/CRF test was used to measure HPA axis reactivity. Experiment-2 focused on HPA axis disruptions; the dexamethasone-suppression and CRF-stimulation tests as well as the Dex/CRF test were used. In both experiments, expression of HPA-axis related transcripts were assessed.

Contextual conditioning in rats as an animal model for generalized anxiety disorder

Animal models of psychiatric disorders are important translational tools for exploring new treatment options and gaining more insight into the disease. Thus far, there is no systematically validated animal model for generalized anxiety disorder (GAD), a severely impairing and difficult-to-treat disease. In this review, we propose contextual conditioning (CC) as an animal model for GAD. We argue that this model has sufficient face validity (there are several symptom similarities), predictive validity (it responds to clinically effective treatments), and construct validity (the underlying mechanisms are comparable). Although the refinement and validation of an animal model is a never-ending process, we want to give a concise overview of the currently available evidence. We suggest that the CC model might be a valuable preclinical tool to enhance the development of new treatment strategies and our understanding of GAD.

The neurobiology of anxiety disorders: brain imaging, genetics, and psychoneuroendocrinology

Anxiety disorders are highly comorbid with each other and with major depressive disorder. As syndromes, anxiety and mood disorders share many symptoms, and several treatments are effective for both. Despite this overlap, there exist many distinguishing features that support the continued classification of individual anxiety disorders that are distinct from each other and from major depression. The goal of this article is to describe the key biological similarities and differences between anxiety disorders.

Overexpression of CB2 cannabinoid receptors decreased vulnerability to anxiety and impaired anxiolytic action of alprazolam in mice

Mice overexpressing CB2r (CB2xP) were exposed to open field (OF), light-dark box (LDB) and elevated plus maze (EPM) tests. Corticotropin-releasing factor (CRF) and pro-opiomelanocortin (POMC) mRNA were measured in paraventricular (PVN) and arcuate (ARC) nuclei of the hypothalamus after 30 minutes of restraint stress (RS). Anxiolytic effects of alprazolam (45 or 70 µg/kg, ip) were evaluated. GABA(A)α(2) and GABA(A)γ(2) mRNA were measured in the hippocampus (HIPP) and amygdala (AMY) of CB2xP and wild type (WT) mice. No differences were observed in the total distance travelled by CB2xP and WT mice in OF. Central and peripheral distances travelled significantly increased and decreased in CB2xP mice. Overexpression of CB2r reduced anxiety-like behaviours in LDB and EPM. In WT mice, RS increased CRF (82%) and POMC (42%) mRNA in the PVN and ARC nuclei, respectively. In CB2xP mice, RS also increased POMC (22%) mRNA in the ARC nucleus, but had no effect on CRF mRNA in the PVN nucleus. Administration of alprazolam was without effect in CB2xP mice. An increase of GABA(A)α(2) and GABA(A)γ(2) mRNA in the hippocampus and amygdala of CB2xP mice was observed. Our findings revealed that increased expression of CB2r significantly reduced anxiogenic-related behaviours, modified the response to stress and impaired the action of anxiolytic drugs.

Therapeutic utility of non-peptidic CRF1 receptor antagonists in anxiety, depression, and stress-related disorders: evidence from animal models

Adaptive responding to threatening stressors is of fundamental importance for survival. Dysfunctional hyperactivation of corticotropin releasing factor type-1 (CRF(1)) receptors in stress response system pathways is linked to stress-related psychopathology and CRF(1) receptor antagonists (CRAs) have been proposed as novel therapeutic agents. CRA effects in diverse animal models of stress that detect anxiolytics and/or antidepressants are reviewed, with the goal of evaluating their potential therapeutic utility in depression, anxiety, and other stress-related disorders. CRAs have a distinct phenotype in animals that has similarities to, and differences from, those of classic antidepressants and anxiolytics. CRAs are generally behaviorally silent, indicating that CRF(1) receptors are normally in a state of low basal activation. CRAs reduce stressor-induced HPA axis activation by blocking pituitary and possibly brain CRF(1) receptors which may ameliorate chronic stress-induced pathology. In animal models sensitive to anxiolytics and/or antidepressants, CRAs are generally more active in those with high stress levels, conditions which may maximize CRF(1) receptor hyperactivation. Clinically, CRAs have demonstrated good tolerability and safety, but have thus far lacked compelling efficacy in major depressive disorder, generalized anxiety disorder, or irritable bowel syndrome. CRAs may be best suited for disorders in which stressors clearly contribute to the underlying pathology (e.g. posttraumatic stress disorder, early life trauma, withdrawal/abstinence from addictive substances), though much work is needed to explore these possibilities. An evolving literature exploring the genetic, developmental and environmental factors linking CRF(1) receptor dysfunction to stress-related psychopathology is discussed in the context of improving the translational value of current animal models.

The CRF system, stress, depression and anxiety-insights from human genetic studies

A concatenation of findings from preclinical and clinical studies support a preeminent function for the corticotropin-releasing factor (CRF) system in mediating the physiological response to external stressors and in the pathophysiology of anxiety and depression. Recently, human genetic studies have provided considerable support to several long-standing hypotheses of mood and anxiety disorders, including the CRF hypothesis. These data, reviewed in this report, are congruent with the hypothesis that this system is of paramount importance in mediating stress-related psychopathology. More specifically, variants in the gene encoding the CRF(1) receptor interact with adverse environmental factors to predict risk for stress-related psychiatric disorders. In-depth characterization of these variants will likely be important in furthering our understanding of the long-term consequences of adverse experience.

Compulsivity in mouse strains homologous with chromosomes 7p and 15q linked to obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is a severe anxiety disorder characterized by obsessions and compulsions. The core symptom of OCD is compulsivity, the inability to stop thinking or acting when you want to, despite being aware of the uselessness of the content or the adverse consequences. To initiate a systematic search for genetic mechanisms underlying the pathophysiology of compulsivity, a panel of chromosome substitution (CS) strains, derived from mice that suppress (C57BL/6J strain) or maintain (A/J strain) high levels of repetitive wheel running during 2 hr of daily limited food access, was screened for this compulsive behavior. Following the genetic screen, we found linkage between compulsive wheel running and mouse chromosomes 2, 6, and 7 that show overlap with recently identified human linkage regions for OCD on chromosomes 7p and 15q. In the overlapping (human/mouse) genomic region, the CRH receptor 2 (CRHR2) gene was tested in a human case-control study. An initial exploration in OCD cases versus controls failed to detect an association between four-candidate CRH2R SNP's within this homologous linkage region and OCD. Genetic fine mapping of compulsivity in mice provides new opportunities to reveal mechanisms underlying this significant psychiatric trait.

Developing small molecule nonpeptidergic drugs for the treatment of anxiety disorders: is the challenge still ahead?

Neuropeptide systems have been considered a major opportunity for the development of novel treatment approaches for anxiety disorders based on preclinical evidence and neurochemical alterations seen in anxiety disorders. This excitement was further facilitated by the fact that drugs acting at these systems, such as CRF1 antagonists, NK1 antagonists, NK3 antagonists or CCK2 antagonists, may have unique properties not seen with drugs affecting more classical mechanisms involved in anxiety. Consequently, there have been major efforts to develop such small-molecule, nonpeptide receptor ligands. A number of these molecules have been tested in the clinic, either in trials where levels of anxiety served as a secondary measure, or in a few studies with patients suffering from anxiety disorders. But unfortunately, and despite all the efforts of the field as a whole, we still lack convincing clinical proof-of-concept for any of the neuropeptidergic approaches in patients. It must, therefore, be concluded that neuropeptide targets remain a promising approach for the development of the next generation drugs to treat anxiety disorders, but that they continue to be high-risk targets for drug development.

The neurobiology of anxiety disorders: brain imaging, genetics, and psychoneuroendocrinology

Anxiety disorders are highly comorbid with each other and with major depressive disorder. As syndromes, anxiety and mood disorders share many symptoms, and several treatments are effective for both. Despite this overlap, there exist many distinguishing features that support the continued classification of individual anxiety disorders that are distinct from each other and from major depression. The goal of this article is to describe the key biological similarities and differences between anxiety disorders.

The NGF saga: from animal models of psychosocial stress to stress-related psychopathology

The role of the neurotrophins Nerve Growth Factor (NGF) and Brain-Derived Neurotrophic Factor (BDNF) has been expanding over the last years from trophic factors involved in brain growth and differentiation, to much more complex messengers, involved in psycho-neuro-endocrine adaptations. Much of this research stems from a series of studies inspired by the life-long work of the Nobel laureate Rita Levi-Montalcini. A new field of research started when NGF was found to be released in the bloodstream as a result of psychosocial stressors in male mice. Subsequent studies have shown that, in humans, highly arousing situations also result in increased blood levels of NGF, underlying the unique role of this neurotrophin, compared to other neuroendocrine effectors, and its sensitivity to environmental variables endowed by a social nature. Data are reviewed to support the hypothesis that this neurotrophic factor, together with BDNF, could be involved in the neurobiological changes underlying physiological and pathological reactions to stress that can result in increased vulnerability to disease in humans, including risk for anxiety disorders, or in the complex pathophysiology associated with mood disorders. Indeed, numerous data indicate that neurotrophins are present in brain hypothalamic areas involved in the regulation of hypothalamic-pituitary-adrenal axis, circadian rhythms and metabolism. In addition, there is now evidence that, in addition to the nervous system, neurotrophins exert their effects in various tissue compartments as they are produced by a variety of non-neuronal cell types such as endocrine and immune cells, adipocytes, endothelial cells, keratinocytes, thus being in a position to coordinate brain and body reactions to external challenges. Aim of this review is to discuss the evidence suggesting a role for neurotrophins as multifunctional signaling molecules activated during allostatic responses to stressful events and their involvement in the complex pathophysiology underlying stress-related psychopathology.

Modulation of stress by imidazoline binding sites: implications for psychiatric disorders

In this review, we present evidence for the involvement of imidazoline binding sites (IBS) in modulating responses to stress, through central control of monoaminergic and hypothalamo-pituitary-adrenal (HPA) axis activity. Pharmacological and physiological evidence is presented for differential effects of different IBS subtypes on serotoninergic and catecholaminergic pathways involved in control of basal and stress-stimulated HPA axis activity. IBS ligands can modulate behavioural and neuroendocrine responses in animal models of stress, depression and anxiety, and a body of evidence exists for alterations in central IBS expression in psychiatric patients, which can be normalised partially or fully by treatment with antidepressants. Dysfunction in monoaminergic systems and the HPA axis under basal and stress-induced activation has been extensively reported in psychiatric illnesses. On the basis of the literature, we suggest a potential therapeutic role for selective IBS ligands in the treatment of depression and anxiety disorders.

Continuous expression of corticotropin-releasing factor in the central nucleus of the amygdala emulates the dysregulation of the stress and reproductive axes

An increase in corticotropin-releasing factor (CRF) is a putative factor in the pathophysiology of stress-related disorders. As CRF expression in the central nucleus of the amygdala (CeA) is important in adaptation to chronic stress, we hypothesized that unrestrained synthesis of CRF in CeA would mimic the consequences of chronic stress exposure and cause dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, increase emotionality and disrupt reproduction. To test this hypothesis, we used a lentiviral vector to increase CRF-expression site specifically in CeA of female rats. Increased synthesis of CRF in CeA amplified CRF and arginine vasopressin peptide concentration in the paraventricular nucleus of the hypothalamus, and decreased glucocorticoid negative feedback, both markers associated with the pathophysiology of depression. In addition, continuous expression of CRF in CeA also increased the acoustic startle response and depressive-like behavior in the forced swim test. Protein levels of gonadotropin-releasing hormone in the medial preoptic area were significantly reduced by continuous expression of CRF in CeA and this was associated with a lengthening of estrous cycles. Finally, sexual motivation but not sexual receptivity was significantly attenuated by continuous CRF synthesis in ovariectomized estradiol-progesterone-primed females. These data indicate that unrestrained CRF synthesis in CeA produces a dysregulation of the HPA axis, as well as many of the behavioral, physiological and reproductive consequences associated with stress-related disorders.Molecular Psychiatry (2009) 14, 37-50; doi:10.1038/mp.2008.91; published online 12 August 2008.

Recent advances in the neurobiology of anxiety disorders: implications for novel therapeutics

Anxiety disorders are a highly prevalent and disabling class of psychiatric disorders. This review focuses on new directions in neurobiological research and implications for the development of novel psychopharmacological treatments. Neuroanatomical and neuroimaging research in anxiety disorders has centered on the role of the amygdala, reciprocal connections between the amygdala and the prefrontal cortex, and, most recently, alterations in interoceptive processing by the anterior insula. Anxiety disorders are characterized by alterations in a diverse range of neurochemical systems, suggesting ample novel targets for drug therapies. Corticotropin-releasing factor (CRF) concentrations are elevated in a subset of anxiety disorders, which suggests the potential utility of CRF receptor antagonists. Pharmacological blockade of the memory-enhancing effects of stress hormones such as glucocorticoids and noradrenaline holds promise as a preventative approach for trauma-related anxiety. The glutamatergic system has been largely overlooked as a potential pharmacological target, although convergent preclinical, neuroimaging, and early clinical findings suggest that glutamate receptor antagonists may have potent anxiolytic effects. Glutamatergic receptor agonists (e.g., D-cycloserine) also have an emerging role in the treatment of anxiety as facilitators of fear extinction during concurrent behavioral interventions. The neuropeptides substance P, neuropeptide Y, oxytocin, orexin, and galanin are each implicated in anxiety pathways, and neuropeptide analogs or antagonists show early promise as anxiolytics in preclinical and/or clinical research. Each of these active areas of research holds promise for expanding and improving evidence-based treatment options for individuals suffering with clinical anxiety.

Regulation of the hypothalamic-pituitary-adrenocortical system in patients with panic disorder

Anxiety and depressive disorders are among the most common psychiatric disorders with a high number of hospital admissions and a lifetime prevalence of up to 25%. So far, the pathophysiological mechanisms for anxiety disorders remain to be found. Preclinical studies suggest that changes in hypothalamic-pituitary-adrenocortical (HPA) system function are causally related to the expression of anxiety-related behavior. The findings on HPA system function in patients with anxiety disorders are, however, heterogeneous. Both hypo- and hyperresponsiveness of HPA response in various anxiety disorders under different experimental conditions were found. In order to characterize putative case/control differences in HPA system function, we performed a Dex-CRH test, a widely used test to pick up changes in HPA system regulation with high sensitivity, in 30 patients with panic disorder, 35 patients with major depressive episode and in 30 controls individually matched for ethnicity, age and gender. The results indicate a similar dysregulation of the HPA system response in the Dex-CRH test in both patient groups. This finding further underlines the hypothesis that both, depression and panic disorder, share impaired HPA system regulation, supporting the notion that the impairment is involved in the pathophysiology of these clinical conditions. However, differences in the suppression effects and psychopathological correlation patterns between depressed and panic patients suggest different biological mechanisms of HPA system dysregulation in both disorders.

Role of corticotropin releasing factor in anxiety disorders: a translational research perspective

Anxiety disorders are a group of mental disorders that include generalized anxiety disorder (GAD), panic disorder, phobic disorders (e.g., specific phobias, agoraphobia, social phobia) and posttraumatic stress disorder (PTSD). Anxiety disorders are among the most common of all mental disorders and, when coupled with an awareness of the disability and reduced quality of life they convey, they must be recognized as a serious public health problem. Over 20 years of preclinical studies point to a role for the CRF system in anxiety and stress responses. Clinical studies have supported a model of CRF dysfunction in depression and more recently a potential contribution to specific anxiety disorders (i.e., panic disorder and PTSD). Much work remains in both the clinical and preclinical fields to inform models of CRF function and its contribution to anxiety. First, we will review the current findings of CRF and HPA axis abnormalities in anxiety disorders. Second, we will discuss startle reflex measures as a tool for translational research to determine the role of the CRF system in development and maintenance of clinical anxiety.

CSF corticotropin-releasing factor in personality disorder: relationship with self-reported parental care

This cross-sectional investigation tests the relationship between the level of self-reported childhood parental care and cerebrospinal fluid (CSF) corticotropin-releasing factor (CRF) concentration in adults with and without personality disorder (PD). Based on preclinical models of the lasting effect of post-natal parental care on central CRF function, the primary hypothesis was that childhood parental care, as reflected by the parental bonding inventory (PBI) care and involvement subscale, is inversely correlated with adult CSF CRF levels. The sample includes cerebrospinal fluid CRF samples from 19 subjects who were included in a previously published report on the relationship between CRF level and Childhood Trauma Questionnaire score. Parental bonding was measured retrospectively with the PBI in 54 medication-free male and female subjects, 37 of whom were diagnosed with a DSM-IV PD, 17 of whom were normal controls free of Axis I and II psychopathology. CSF CRF level as measured by lumbar puncture was entered into a model as the dependent variable, with the independent variables of PBI Parental Care and Involvement, diagnostic category, age, and gender. The model predicting CSF CRF level was significant, with PBI parental care and involvement negatively correlated with CSF CRF level. PD subjects with higher than median PBI parental care and involvement score had significantly lower CSF CRF levels than both normal controls and PD subjects with lower than median PBI parental care and involvement. Higher levels of self-report parental care predict lower CSF CRF levels in PD subjects, consistent with a beneficial effect of parental care on decreased stress reactivity, and consistent with previous reports in humans. The cross-sectional design of the study, however, limits causal inferences.

Corticotropin releasing factor (CRF) receptor signaling in the central nervous system: new molecular targets

Corticotropin-releasing factor (CRF) and the related urocortin peptides mediate behavioral, cognitive, autonomic, neuroendocrine and immunologic responses to aversive stimuli by activating CRF(1) or CRF(2) receptors in the central nervous system and anterior pituitary. Markers of hyperactive central CRF systems, including CRF hypersecretion and abnormal hypothalamic-pituitary-adrenal axis functioning, have been identified in subpopulations of patients with anxiety, stress and depressive disorders. Because CRF receptors are rapidly desensitized in the presence of high agonist concentrations, CRF hypersecretion alone may be insufficient to account for the enhanced CRF neurotransmission observed in these patients. Concomitant dysregulation of mechanisms stringently controlling magnitude and duration of CRF receptor signaling also may contribute to this phenomenon. While it is well established that the CRF(1) receptor mediates many anxiety- and depression-like behaviors as well as HPA axis stress responses, CRF(2) receptor functions are not well understood at present. One hypothesis holds that CRF(1) receptor activation initiates fear and anxiety-like responses, while CRF(2) receptor activation re-establishes homeostasis by counteracting the aversive effects of CRF(1) receptor signaling. An alternative hypothesis posits that CRF(1) and CRF(2) receptors contribute to opposite defensive modes, with CRF(1) receptors mediating active defensive responses triggered by escapable stressors, and CRF(2) receptors mediating anxiety- and depression-like responses induced by inescapable, uncontrollable stressors. CRF(1) receptor antagonists are being developed as novel treatments for affective and stress disorders. If it is confirmed that the CRF(2) receptor contributes importantly to anxiety and depression, the development of small molecule CRF(2) receptor antagonists would be therapeutically useful.

The role of corticotropin-releasing factor-like peptides in cannabis, nicotine, and alcohol dependence

The corticotropin-releasing factor (CRF)-like peptides, which include the mammalian peptides CRF, urocortin 1, urocortin 2, and urocortin 3, play an important role in orchestrating behavioral and physiological responses that may increase an organism's chance of survival when confronted with internal or external stressors. There is, however, evidence that a chronic overactivity of brain CRF systems under basal conditions may play a role in the etiology and maintenance of psychiatric disorders such as depression and anxiety disorders. In addition, there is evidence of a role for CRF-like peptides in acute and protracted drug abstinence syndromes and relapse to drug-taking behavior. This review focuses on the role of CRF-like peptides in the negative affective state associated with acute and protracted withdrawal from three widely abused drugs, cannabis, nicotine, and alcohol. In addition, we discuss the high comorbidity between stress-associated psychiatric disorders and drug dependence. A better understanding of the brain stress systems that may underlie psychiatric disorders, acute and protracted drug withdrawal, and relapse to drug-taking behavior may help in the development of new and improved pharmacotherapies for these widespread psychiatric disorders.

Increased cerebrospinal fluid corticotropin-releasing factor concentrations during tryptophan depletion in healthy adults

BACKGROUND

Brain serotonin neurotransmission and hypothalamic-pituitary-adrenal axis function are implicated in the pathophysiology of depression, and these systems interact in a reciprocal modulatory fashion. This study examined the effect of tryptophan depletion, which acutely reduces brain serotonin concentrations, on serial cerebrospinal fluid concentrations of corticotropin-releasing factor in healthy humans.

METHODS

Five subjects completed a standard tryptophan depletion protocol, and four subjects participated in a comparison condition. Subjects underwent continuous sampling of cerebrospinal fluid via lumbar peristaltic pump. Concentrations of cerebrospinal fluid corticotropin-releasing factor were measured by radioimmunoassay.

RESULTS

No mood changes were observed in either group. Tryptophan-depleted subjects exhibited significantly greater increases in corticotropin-releasing factor concentrations over time than subjects in the comparison condition.

CONCLUSIONS

These findings highlight the potential importance of corticotropin-releasing factor and serotonin interactions and suggest that activation of corticotropin-releasing-factor-containing neurons could play a role in the emergence of mood symptoms following tryptophan depletion in vulnerable individuals.

Urocortin expression in the Edinger-Westphal nucleus is down-regulated in transgenic mice over-expressing neuronal corticotropin-releasing factor

In recent years a large body of evidence has emerged linking chronic stress with increased vulnerability for depression and anxiety disorders. As corticotropin-releasing factor (CRF) is hypersecreted under these psychological conditions, we used our CRF-overexpressing (CRF-OE) mouse line to study underlying brain mechanisms possibly causing these disorders. Urocortin (Ucn), a recently discovered member of the CRF peptide family may play a role in the pathophysiology of stress-induced disorders. Stressors recruit Ucn-immunoreactive neurons in the Edinger-Westphal nucleus (E-WN), which is the major site of Ucn expression. Furthermore, E-WN Ucn mRNA levels are upregulated in CRF-deficient mice. Based on these findings, we hypothesized the down-regulation of E-WN Ucn in CRF-OE mice and consequently, altered responsiveness to stressful stimuli. Our results support this hypothesis as we found weaker immunohistochemical labeling with anti-Ucn and a six times weaker Ucn mRNA signal in E-WN in CRF-OE mice. Moreover, E-WN Ucn-expressing neurons mounted a response to acute challenge in CRF-OE mice too. From these results it is concluded that the CRF and E-WN Ucn neuronal systems work in concert in response to acute challenges, but are inversely regulated in their activities during chronic hyperactivity of the hypothalamo-pituitary-adrenal axis.

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.

Neurobiology of generalized anxiety disorder

On reviewing the literature on GAD and trying to summarize the various developments in the field of neurobiology of GAD, we see that a range of hypotheses try to explore and integrate the observations found into potentially meaningful theories. Abnormal serotonergic and GABAergic function occur in many patients with GAD. Functional imaging data have shown increased cortical activity and decreased basal ganglia activity in patients with GAD, which reverses with treatment, but it is apparent that no one theory is sufficiently comprehensive to propose a unitary hypothesis for the development of GAD and other anxiety disorders. GAD is a relatively new diagnosable condition, first introduced into the classification system of psychiatric disorders in 1980, and since then has undergone a series of changes in its conceptualization, with some investigators questioning the existence of the condition as a distinct entity. Any inferences that may be drawn from various studies must be guarded, and it is appropriate to compare studies using the same diagnostic criteria. Significant research has been done and may lead to exciting new discoveries in the treatment of anxiety disorders in general and GAD in particular. Gray's model of behavioral inhibition, in which the septohippocampal system acts by assessing stimuli for the presence of danger and, when that is detected, activates the behavioral-inhibition circuit, provides a neuroanatomic conceptualization that has been expanded by preclinical research. Some exciting work has been done on CRF and the concept of development, vulnerability, and kindling and some investigators have contributed to this area of interest. This concept supports the hypothesis that a genetic predisposition, coupled with early stress, in the crucial phases of development may result in a phenotype that is neurobiologically vulnerable to stress and may lower an individual's threshold for developing anxiety or depression on additional stress exposure. The pharmaceutical industry is exploring treatment options using CRF antagonists, and research on other neuropeptides, especially NPY, will be of interest. Research on neurosteroids also may bring the opportunity for pharmacologic treatment approaches. Future research on the startle reflex and on the NMDA and the metabotropic glutamate receptors is important. Future studies of a more homogenous patient population and using more sophisticated techniques, such as molecular genetic strategies and better imaging techniques, may answer some of the outstanding questions.

Corticotropin-releasing hormone and animal models of anxiety: gene-environment interactions

The study of the neural substrates underlying stress and anxiety has in recent years been enriched by a burgeoning pool of genetic information gathered from rodent studies. Two general approaches have been used to characterize the interaction of genetic and environmental factors in stress regulation: the evaluation of stress-related behavioral and endocrine responses in animals with targeted deletion or overexpression of specific genes and the evaluation of changes in central nervous system gene expression in response to environmental perturbations. We review recent studies that have used molecular biology and genetic engineering techniques such as in situ hybridization, transgenic animal, and antisense oligonucleotide gene-targeting methodologies to characterize the function of corticotropin-releasing hormone (CRH) system genes in stress. The effects of genetic manipulations of each element of the CRH system (CRH, its two receptors, and its binding protein) on stress-related responses are summarized. In addition, the effects of stress (acute, repeated, or developmental) on CRH system gene expression are described. The results from these studies indicate that experimentally engineered or stress-induced dysregulation of gene expression within the CRH system is associated with aberrant responses to environmental contingencies. These results are discussed in the context of how CRH system dysfunction might contribute to stress-related psychopathology and are presented in conjunction with clinical findings of CRH system dysregulation in psychiatric illness. Finally, future research strategies (i.e., high-throughput gene screening and novel gene-targeting methodologies) that may be used to gain a fuller understanding of how CRH system gene expression affects stress-related functioning are discussed.

Orbitofrontal cortex dysfunction in obsessive-compulsive disorder? I. Alternation learning in obsessive-compulsive disorder: male-female comparisons

BACKGROUND

We have previously reported a significant negative correlation between severity of symptoms and performance of an alternation learning task in female obsessive-compulsive disorder (OCD) patients. The present study was aimed at exploring this relationship between alternation learning and OCD symptom severity in male OCD patients.

METHODS AND RESULTS

Eighteen female obsessive-compulsive disorder patients and 14 male non-depressed, drug free, OCD patients participated in the study. Measures of dorsolateral prefrontal function (Wisconsin Card Sorting Test) and orbitofrontal cortex function (object alternation learning) showed no significant differences between the sexes. The relationship between orbitofrontal cortex function and severity of OC symptoms was significantly different between the sexes (z=2.44. P=0.007). While this correlation was negative in the females it was positive in the males.

CONCLUSIONS

These results may indicate sexual dimorphism in OCD.

Possible role of neuropeptides in obsessive compulsive disorder

The most consistent finding in clinical research of obsessive compulsive disorder (OCD) is the significant treatment advantage of potent serotonin uptake inhibitors (SUIs) over other classes of antidepressant and antianxiety drugs. Clinical neurobiological studies of OCD, however, have yielded limited and inconsistent evidence for significant fundamental abnormalities in monoamine systems including serotonin, norepinephrine and dopamine. Furthermore, one-third to one-half of OCD patients do not experience a clinically meaningful improvement with SUI treatment. Investigation beyond the monoamine systems may be necessary in order to more fully understand the pathophysiology of obsessive-compulsive symptoms and develop improved treatments. Evidence from preclinical studies suggests that neuropeptides may have important influences on memory acquisition, maintenance and retrieval; grooming, maternal, sexual and aggressive behavior; fixed action patterns; and stereotyped behavior; these phenomena may relate to some features of OCD. In addition, extensive interactions have been identified in the brain between neuropeptidergic and monoaminergic systems, including co-localization among specific populations of neurons. The purpose of this review is to present the current knowledge of the role of neuropeptides in the clinical neurobiology of children, adolescents and adults with OCD focusing primarily on results from pharmacological challenge and cerebrospinal fluid studies. Where evidence exists, developmentally regulated differences in neuropeptide function between children and adolescents versus adults with OCD will be emphasized; these data are intended to underscore the potential importance of establishing the age of symptom onset (childhood versus adult) in individual patients with OCD participating in clinical neurobiological investigations. Likewise, where information is available, differences in measures of neuropeptides between patients with non-tic-related OCD versus tic-related OCD will be highlighted; these data will demonstrate the critical value of diagnostic precision, as these two particular subtypes of OCD may have different neurochemical underpinnings.

Brain circuits in panic disorder

This paper reviews the pathophysiology of panic disorder (PD), within the context of newly described "fear circuitries," which have been well characterized in preclinical models. Substantial advances in the neurosciences have made it possible for clinical neuroscientists to refine our understanding of the pathophysiology of PD and the mechanisms of currently effective treatment. These advances have in turn helped generate testable hypotheses for future neurobiological and psychopharmacologic research. Perturbation of mutual modulation ("cross talk") between key brain transmitter systems (serotonin, norepinephrine, gamma-aminobutyric acid, corticotropin-releasing factor, and others) may underlie the pathogenesis of panic-anxiety. Restoration of normal homeostasis may be an important therapeutic component of antipanic therapy and may provide information about underlying neurocircuits. Neuroimaging, an important new tool, has already begun to bridge the gap between the preclinical and clinical neurosciences through confirmation of hypothesized dysfunction of the complex human prefrontal cortex and its subcortical components. In higher species, such as humans, dysfunction of cortical inhibition or excessive cortical activation of caudal limbic structures is postulated to lead to activation of the phylogenetically conserved amygdalofugal pathways. Consistent with probable subtypes of PD, overlapping theoretical models of panic neurocircuitries are proposed, including ventilatory dysregulation, which is coupled with neurovascular instability in a critical area of the panic neurocircuitry--the amygdalohippocampus. Neuroimaging appears a critical tool in guiding further elaboration of the interaction of cortical and subcortical components of the panic neurocircuitry, whereas challenge studies appear crucial in gathering further information regarding brain stem dysfunction.

Elevated CSF corticotropin-releasing factor concentrations in posttraumatic stress disorder

OBJECTIVE

Corticotropin-releasing factor (CRF) and somatostatin both play important roles in mediating responses to acute and chronic stress. The purpose of this study was to measure CSF concentrations of CRF and somatostatin in patients with chronic combat-related post-traumatic stress disorder (PTSD) and comparison subjects.

METHOD

Lumbar punctures for collection of CSF were performed in Vietnam combat veterans with PTSD (N = 11) and comparison subjects (N = 17). CSF concentrations of CRF and somatostatin were compared between the two groups.

RESULTS

CSF concentrations of CRF were higher in the PTSD patients than in the comparison subjects (mean = 29.0 pg/ml, SD = 7.8, versus mean = 21.9 pg/ml, SD = 6.0). This group difference remained significant after covariance for age. CSF somatostatin concentrations in PTSD patients were higher than those of the comparison subjects (mean = 19.9 pg/ml, SD = 5.4, versus mean = 13.7 pg/ml, SD = 8.0). However, covarying for age reduced the level of significance.

CONCLUSIONS

Higher CSF CRF concentrations in patients with PTSD may reflect alterations in stress-related neurotransmitter systems. The higher CSF CRF concentrations may play a role in disturbances of arousal in patients with PTSD.

Noradrenergic receptor sensitivity in obsessive compulsive disorder: II. Cortisol response to acute clonidine administration

Sensitivity of pre-synaptic alpha-2- and post-synaptic alpha-1- and beta-adrenoceptors was investigated in 15 patients with obsessive-compulsive disorder (OCD) and in 15 age- and sex-matched healthy controls, by measuring cortisol responses to saline administration and to inhibition by clonidine (clon), a noradrenergic receptor agonist. Basal values of cortisol and responses to administration of saline and of clon were the same in patients and controls.