Neuroanatomical circuits modulating fear and anxiety behaviors

Functional magnetic resonance imaging characterization of CCK-4-induced panic attack and subsequent anticipatory anxiety

The main objective of this work was to study the functional markers of the clinical response to cholecystokinin tetrapeptide (CCK-4). Twelve healthy male subjects were challenged with CCK-4 and simultaneously underwent functional magnetic resonance imaging (fMRI) recording. Since anticipatory anxiety (AA) is an intrinsic part of panic disorder, a behavioral paradigm, using the threat of being administered a second injection of CCK-4, has been developed to investigate induced AA. The study was composed of three fMRI scans according to an open design. During first and second scan, subjects were injected with placebo and CCK-4, respectively. The third scan was the AA challenge. CCK-4 administration induced physiological and psychological symptoms of anxiety that met the criteria for a panic attack in 8 subjects, as well as cerebral activation in anxiety-related brain regions. Clinical and physiological response intensity was consistent with cerebral activity extent and robustness. fMRI proved more sensitive than clinical assessment in evidencing the effects of the AA challenge. The latter induced brain activation, different from that obtained on CCK-4 and during placebo injection, that was likely related to anxiety. The method applied in this study is suitable for the study of anxiety using fMRI.

Amygdala input monosynaptically innervates parvalbumin immunoreactive local circuit neurons in rat medial prefrontal cortex

The projection from the basolateral nucleus of the amygdala (BLA) conveys information about the affective significance of sensory stimuli to the medial prefrontal cortex (mPFC). By using an anterograde tract-tracing procedure combined with immunocytochemistry and correlated light/electron microscopical examination, labeled BLA afferents to layers 2-6 of the rat mPFC are shown to establish asymmetrical synaptic contacts, not only with dendritic spines (approximately 95.7% of targets innervated), but also with the aspiny dendritic shafts and somata of multipolar parvalbumin immunopositive (PV+) neurons. A population of PV- dendritic shafts was also innervated. Labeled BLA synaptic input to identified PV+ structures occurred in layers 2-6 of mPFC. The results indicate that labeled BLA afferents predominantly contact the spiny processes of presumed pyramidal cells and also provide a direct and specific innervation to a sub-population of local circuit neurons in mPFC containing PV. Since PV+ cells include two significant classes of fast-spiking GABAergic inhibitory interneuron (basket and axo-axonic cells), these novel observations indicate that the amygdalocortical pathway in the rat has the ability to directly influence functionally strategic 'feed-forward' inhibitory mechanisms at the first stage of processing amygdalocortical information.

The development of psychopathy

The current review focuses on the construct of psychopathy, conceptualized as a clinical entity that is fundamentally distinct from a heterogeneous collection of syndromes encompassed by the term 'conduct disorder'. We will provide an account of the development of psychopathy at multiple levels: ultimate causal (the genetic or social primary cause), molecular, neural, cognitive and behavioral. The following main claims will be made: (1) that there is a stronger genetic as opposed to social ultimate cause to this disorder. The types of social causes proposed (e.g., childhood sexual/physical abuse) should elevate emotional responsiveness, not lead to the specific form of reduced responsiveness seen in psychopathy; (2) The genetic influence leads to the emotional dysfunction that is the core of psychopathy; (3) The genetic influence at the molecular level remains unknown. However, it appears to impact the functional integrity of the amygdala and orbital/ventrolateral frontal cortex (and possibly additional systems); (4) Disruption within these two neural systems leads to impairment in the ability to form stimulus-reinforcement associations and to alter stimulus-response associations as a function of contingency change. These impairments disrupt the impact of standard socialization techniques and increase the risk for frustration-induced reactive aggression respectively.

Enhancement of conditioned fear extinction by infusion of the GABAAagonist muscimol into the rat prefrontal cortex and amygdala

In auditory fear conditioning, repeated presentation of the tone in the absence of the shock leads to extinction of the acquired fear response. Both the infra limbic prefrontal cortex (IL) and the basolateral amygdala (BLA) are involved in extinction. In this study, we examine the involvement of these two regions in extinction by manipulating the gamma-aminobutyric acid (GABA)ergic system, in the Sprague-Dawley rat. We microinfused a low dose of the GABA(A) agonist muscimol into the IL or BLA. Muscimol infused to IL before extinction training, but not after either a short (five-trials) or long (15-trials) extinction training, resulted in long-term facilitation of extinction. Infusion of muscimol to the BLA following a short (five-trial) extinction session facilitated extinction at least 48-h post-drug infusion. The differences in the temporal parameters of the effects of muscimol in the IL or BLA, suggest differential involvement of these structures in long-term extinction of fear memory. We propose a facilitating role for GABA(A) neurotransmission in the IL in triggering the onset of fear extinction and its maintenance, whereas in the BLA, GABA(A) neurotransmission facilitates extinction consolidation. The involvement of GABA(A) receptors in fear extinction in the prefrontal cortex and amygdala is of particular interest, because of the role of these areas in emotional processes, and the role of the GABA(A) receptors in anxiety states.

Role of stress, corticotrophin releasing factor (CRF) and amygdala plasticity in chronic anxiety

Stress initiates a series of neuronal responses that prepare an organism to adapt to new environmental challenges. However, chronic stress may lead to maladaptive responses that can result in psychiatric syndromes such as anxiety and depressive disorders. Corticotropin-releasing factor (CRF) has been identified as a key neuropeptide responsible for initiating many of the endocrine, autonomic and behavioral responses to stress. The amygdala expresses high concentrations of CRF receptors and is itself a major extrahypothalamic source of CRF containing neurons. Within the amygdala, the basolateral nucleus (BLA) has an important role in regulating anxiety and affective responses. During periods of stress, CRF is released into the amygdala and local CRF receptor activation has been postulated as a substrate for stress-induced alterations in affective behavior. Previous studies have suggested that synaptic plasticity in the BLA contributes to mechanisms underlying long-term changes in the regulation of affective behaviors. Several studies have shown that acute glutamate receptor-mediated activation, by either GABA-mediated disinhibition or CRF-mediated excitation, induces long-term synaptic plasticity and increases the excitability of BLA neurons. This review summarizes some of the data supporting the hypotheses that stress induced plasticity within the amygdala may be a critical step in the pathophysiology of the development of chronic anxiety states. It is further proposed that such a change in the limbic neural circuitry is involved in the transition from normal vigilance responses to pathological anxiety, leading to syndromes such as panic and post-traumatic stress disorders.

Cortico-amygdala circuits: role in the conditioned stress response

The amygdala plays a crucial role in the orchestration and modulation of the organism response to aversive, stressful events. This response could be conceived as the result of two interdependent components. The first is represented by sets of visceral and motor responses aimed at helping the organism to cope with the present event. The second is the acquisition and modulation of memories relative to the stressful stimulus and its context. This latter component contributes to the instatement of conditioned stress responses that are essential to the capability of the organism to predict future exposures to similar stimuli in order to avoid them or counteract them effectively. In the amygdala, these two components become fully integrated. Massive networks link the amygdala to the hypothalamus, midbrain and brainstem. These networks convey visceral, humoral and nociceptive information to the amygdala and mediate its effects on the hypothalamic-pituitary-adrenal axis as well on autonomic and motor centers. On the other hand, interactions between the amygdala and interconnected cortical networks play a crucial role in acquisition, consolidation and extinction of learning relative to the stressful stimulus. Within the scope of this review, current evidence relative to the interaction between the amygdala and cortical networks will be considered in relationship to the integration of the conditioned response to stress.

Mouse behavioural analysis in systems biology

Molecular techniques allowing in vivo modulation of gene expression have provided unique opportunities and challenges for behavioural studies aimed at understanding the function of particular genes or biological systems under physiological or pathological conditions. Although various animal models are available, the laboratory mouse (Mus musculus) has unique features and is therefore a preferred animal model. The mouse shares a remarkable genetic resemblance and aspects of behaviour with humans. In this review, first we describe common mouse models for behavioural analyses. As both genetic and environmental factors influence behavioural performance and need to be carefully evaluated in behavioural experiments, considerations for designing and interpretations of these experiments are subsequently discussed. Finally, common behavioural tests used to assess brain function are reviewed, and it is illustrated how behavioural tests are used to increase our understanding of the role of histaminergic neurotransmission in brain function.

Anxiety in patients with epilepsy: systematic review and suggestions for clinical management

Up to 50 or 60% of patients with chronic epilepsy have various mood disorders including depression and anxiety. Whereas the relationship between epilepsy and depression has received much attention, less is known about anxiety disorders. It is now recognized that anxiety can have a profound influence on the quality of life of patients with epilepsy. The relationship between anxiety disorders and epilepsy is complex. It is necessary to distinguish between different manifestations of anxiety disorder: ictal, postictal, and interictal anxiety. Preexisting vulnerability factors, neurobiological factors, iatrogenic influences (antiepileptic drugs, epilepsy surgery), and psychosocial factors are all likely to play a role, but with considerable individual differences. Despite the high prevalence of anxiety disorders in patients with epilepsy, there are no systematic treatment studies or evidence-based guidelines for best treatment practice. Nevertheless, a practical approach based on the temporal relationship between anxiety and epileptic seizures allows clinicians to consider appropriate treatment strategies to reduce the psychiatric comorbidity in patients with epilepsy.

Chronic cold stress alters prefrontal cortical modulation of amygdala neuronal activity in rats

BACKGROUND

Recent studies suggest that long-term exposure to stress can sensitize animals to subsequent novel or acute stressors. Stressors affect amygdala activity, and the prefrontal cortex has been implicated in the regulation of responses to stress. Little is known, however, about how the physiology of amygdala neurons is altered by chronic stressors or the role of the prefrontal cortex in these changes.

METHODS

We used in vivo extracellular recordings from neurons in the rat central and basolateral amygdala nuclei to examine the effects of chronic stress on the basal firing and responses of amygdala neurons to a novel stressor. Additionally, prefrontal cortical afferents were severed to examine its role in the modulation of the response to stressors.

RESULTS

Chronic exposure to cold enhanced the sensitivity of central amygdala neurons to footshock. A portion of this may be due to enhanced basolateral amygdala output. Furthermore, prefrontal cortical regulation of this response is weakened by chronic stress.

CONCLUSIONS

The physiology of the amygdala is altered by chronic stress. Furthermore, the prefrontal cortical regulation of these responses may be weakened after chronic stress. This is a potential biological substrate for abnormal affect upon chronic stress and its effect on affective disorders.

[Patients with epilepsy and anxiety disorders. Diagnosis and treatment]

Up to 50-60% of patients with epilepsy may develop psychiatric complications, in particular depression, anxiety, and psychotic disorders. Although this comorbidity has received a great deal of attention in recent years, the anxiety spectrum of psychiatric disturbances in epilepsy patients has not been extensively studied, although this comorbidity has a significant effect on the medical management and quality of life. The etiology is multifactorial, including neurobiological and shared pathophysiological mechanisms as well as psychosocial and iatrogenic factors (e.g., influence of antiepileptic drugs, epilepsy surgery). Despite the high prevalence of comorbid anxiety in epilepsy, very little is known about optimal treatment strategies. This article reviews the complex interrelationships between anxiety disorders and epilepsy from a clinical point of view. The evaluation of anxiety relative to ictal, peri-ictal, and postictal states is described, and medical treatment options for anxiety disorders in patients with epilepsy are discussed, illustrating that their treatment extends far beyond seizure control.

TMT-induced autonomic and behavioral changes and the neural basis of its processing

One of the main interests in the field of neuroscience is the investigation of the neural basis of fear. During recent years, an increasing number of studies have used trimethylthiazoline (TMT), a component of red fox feces, as a stimulus to induce fear in predator naive rats, mice, and voles. The aim of the present review is to summarize these studies. We present an overview to the autonomic and behavioral changes that are induced by TMT exposure. Then, we summarize the small number of studies that have examined the neural processing of the TMT stimulus. Finally, we compare these studies with those using a natural predator or predator odor to induce fear and discuss the possible use of TMT exposure in rodents as an animal model of unconditioned fear in humans.

Differentiating anxiety and depression symptoms in patients with partial epilepsy

Anxiety and depression are separate psychiatric conditions that are often interrelated. This study examines whether they exist independently in this population of patients with partial epilepsy and if they affect all quality-of-life domains. Adult epilepsy patients taking two or more antiepileptic drugs completed a health status survey including demographic items, the Hospital Anxiety and Depression Scale, and the Quality of Life in Epilepsy-10 (QOLIE-10). The questionnaire was completed by 201 epilepsy patients. Symptom prevalences of anxiety (52% none, 25% mild, 16% moderate, 7% severe) and depression (62% none, 20% mild, 14% moderate, 4% severe) were high. All health-related quality-of-life (HRQOL) domains worsened significantly with increasing levels of anxiety and depression: Total QOLIE-10 scores decreased from 72+/-18 in patients with no anxiety to 54+/-13 in those with mild, 48+/-18 in those with moderate, and 40+/-23 in those with severe anxiety (P<0.0001). Total QOLIE-10 scores decreased from 70+/-16 in patients with no depression to 50+/-16 in those with mild, 45+/-16 in those with moderate, and 24+/-21 in those with severe depression (P<0.0001). No significant difference in anxiety scores was observed controlling for seizure frequency or epilepsy duration. Regression analyses showed that anxiety and depression account for different proportions of variance as predictors of HRQOL (R2=0.337 (anxiety) and 0.511 (depression)). The data suggest that patients may benefit from increased attention to the role of anxiety separately from depression.

Regulation of anxiety and initiation of sexual behavior by CREB in the nucleus accumbens

Sexual deficits and other behavioral disturbances such as anxiety-like behaviors can be observed in animals that have undergone social isolation, especially in species having important social interactions. Using a model of protracted social isolation in adult rats, we observed increased anxiety-like behavior and deficits in both the latency to initiate sexual behavior and the latency to ejaculate. We show, using transgenic cAMP response element (CRE)-LacZ reporter mice, that protracted social isolation also reduces CRE-dependent transcription within the nucleus accumbens. This decrease in CRE-dependent transcription can be mimicked in nonisolated animals by local viral gene transfer of a dominant negative mutant of CRE-binding protein (CREB). We previously showed that this manipulation increases anxiety-like behavior. We show here that it also impairs initiation of sexual behavior in nonisolated animals, a deficit that can be corrected by anxiolytic drug treatment. This local reduction in CREB activity, however, has no influence on ejaculation parameters. Reciprocally, we used the viral transgenic approach to overexpress CREB in the nucleus accumbens of isolated animals. We show that this local increase in CREB activity completely rescued the anxiety phenotype of the isolated animals, as well as their deficit in initiating sexual behavior, but failed to rescue the deficit in ejaculation. Our data suggest a role for the nucleus accumbens in anxiety responses and in specific aspects of sexual behavior. The results also provide insight into the molecular mechanisms by which social interactions affect brain plasticity and behavior.

Mood and anxiety disorders in women with treated hyperthyroidism and ophthalmopathy caused by Graves' disease

OBJECTIVE

To evaluate the prevalence of mood and anxiety disorders in women with treated hyperthyroidism caused by Graves' disease and to compare them with the prevalence of such findings in women without past or present thyroid disease.

METHODS

Thirty inpatient women with treated hyperthyroidism and ophthalmopathy caused by Graves' disease and 45 women hospitalized for treatment of gynecologic disorders such as abnormal vaginal bleeding, benign tumors or infertility were evaluated for the prevalence of mood and anxiety diagnoses using a standard Mini-International Neuropsychiatric Interview and for mood and anxiety ratings using the Profile of Mood States (POMS). At the time of assessment, it was discovered that 14 of 30 women with treated hyperthyroidism caused by Graves' disease were still hyperthyroid, while 16 women were euthyroid.

RESULTS

Significantly greater prevalence of social anxiety disorder, generalized anxiety disorder, major depression and total mood and anxiety disorders, as well as higher symptom scores on the POMS, was found in hyperthyroid women with Graves' disease in comparison with the control group. A prevalence of total anxiety disorder, as well as history of mania or hypomania and lifetime bipolar disorder, but not lifetime unipolar depression, was more frequent in both the euthyroid and the hyperthyroid subgroups of study women in comparison with the control group.

CONCLUSIONS

These results confirm a high prevalence of mood and anxiety disorders in women with treated hyperthyroidism and ophthalmopathy caused by Graves' disease. Hyperthyroidism plays a major role in psychiatric morbidity in Graves' disease.

Genetics of anxiety disorders

There is considerable evidence that genetic determinants play a major role in the etiology of anxiety. Investigations into susceptibility genes for anxiety are well underway, particularly for panic disorder and obsessive-compulsive disorder and more broadly defined anxiety-related traits, such as neuroticism and harm avoidance. This review will discuss some of the core issues related to diagnosis and molecular genetic methodology, followed by a review of recent molecular genetic findings for anxiety. The authors will attempt to highlight the numerous convergent and exciting findings. Given the rapid acceleration in knowledge of the human genome, a more definitive understanding of the genetic roots of these complex conditions may be anticipated in the relatively near future.

Modulation of autonomic balance by tumors and viruses

Autonomic balance, a function generally under host control, is subject to modulation by other signalers. In some cases, modulation of host autonomic function through behavioral and physical stressors exerted by another individual may have negative consequences for the stress recipient by inducing sympathetic bias. Modulation of autonomic function may sometimes benefit one party at the expense of another. Tumors and HIV are examples of illegitimate signalers who may induce host sympathetic bias to promote their own growth and evade host immune surveillance. Paraneoplastic and paraviral syndromes such as hypertrophic osteoarthopathy, QTc prolongation, insomnia, and cachexia could be viewed as epiphenomena related to the tumoral and viral manipulation of host autonomic balance. In a more general framework, other paraneoplastic and paraviral syndromes may represent epiphenomena related to modulation of endocrine, cytokine, and autonomic functions by tumors and viruses to promote their own survival. Spatial distribution of cancers and viruses within the host may reflect affinity for strategic locations that facilitate manipulation of a variety of host functions including autonomic, endocrine, and cytokine regulation. A more general for understanding spatial distribution of diseases based on gradients of autonomic balance in the body are explored. Darwinian perspectives are discussed.