Panic, suffocation false alarms, separation anxiety and endogenous opioids

The impact of smoking in adolescence on early adult anxiety symptoms and the relationship between infant vulnerability factors for anxiety and early adult anxiety symptoms: the TOPP Study

Cigarette smoking is increased in people with trait anxiety and anxiety disorders, however no longitudinal data exist illuminating whether smoking in adolescence can influence the developmental trajectory of anxiety symptoms from early vulnerability in infancy to adult anxiety expression. Using The Tracing Opportunities and Problems in Childhood and Adolescence (TOPP) Study, a community-based cohort of children and adolescents from Norway who were observed from the age of 18 months to age 18-19 years, we explored the relationship between adolescent smoking, early vulnerability for anxiety in infancy (e.g. shyness, internalizing behaviors, emotional temperaments) and reported early adult anxiety. Structural equation modeling demonstrated that adolescent active smoking was positively associated with increased early adulthood anxiety (β = 0.17, p<0.05), after controlling for maternal education (proxy for socioeconomic status). Adolescent anxiety did not predict early adult smoking. Adolescent active smoking was a significant effect modifier in the relationship between some infant vulnerability factors and later anxiety; smoking during adolescence moderated the relationship between infant internalizing behaviors (total sample: active smokers: β = 0.85, p<0.01, non-active smokers: ns) and highly emotional temperament (total sample: active smokers: β = 0.55, p<0.01,non-active smokers: ns), but not shyness, and anxiety in early adulthood. The results support a model where smoking acts as an exogenous risk factor in the development of anxiety, and smoking may alter the developmental trajectory of anxiety from infant vulnerability to early adult anxiety symptom expression. Although alternative non-mutually exclusive models may explain these findings, the results suggest that adolescent smoking may be a risk factor for adult anxiety, potentially by influencing anxiety developmental trajectories. Given the known adverse health effects of cigarette smoking and significant health burden imposed by anxiety disorders, this study supports the importance of smoking prevention and cessation programs targeting children and adolescence.

How cigarette smoking may increase the risk of anxiety symptoms and anxiety disorders: a critical review of biological pathways

Multiple studies have demonstrated an association between cigarette smoking and increased anxiety symptoms or disorders, with early life exposures potentially predisposing to enhanced anxiety responses in later life. Explanatory models support a potential role for neurotransmitter systems, inflammation, oxidative and nitrosative stress, mitochondrial dysfunction, neurotrophins and neurogenesis, and epigenetic effects, in anxiety pathogenesis. All of these pathways are affected by exposure to cigarette smoke components, including nicotine and free radicals. This review critically examines and summarizes the literature exploring the role of these systems in increased anxiety and how exposure to cigarette smoke may contribute to this pathology at a biological level. Further, this review explores the effects of cigarette smoke on normal neurodevelopment and anxiety control, suggesting how exposure in early life (prenatal, infancy, and adolescence) may predispose to higher anxiety in later life. A large heterogenous literature was reviewed that detailed the association between cigarette smoking and anxiety symptoms and disorders with structural brain changes, inflammation, and cell-mediated immune markers, markers of oxidative and nitrosative stress, mitochondrial function, neurotransmitter systems, neurotrophins and neurogenesis. Some preliminary data were found for potential epigenetic effects. The literature provides some support for a potential interaction between cigarette smoking, anxiety symptoms and disorders, and the above pathways; however, limitations exist particularly in delineating causative effects. The literature also provides insight into potential effects of cigarette smoke, in particular nicotine, on neurodevelopment. The potential treatment implications of these findings are discussed in regards to future therapeutic targets for anxiety. The aforementioned pathways may help mediate increased anxiety seen in people who smoke. Further research into the specific actions of nicotine and other cigarette components on these pathways, and how these pathways interact, may provide insights that lead to new treatment for anxiety and a greater understanding of anxiety pathogenesis.

Evidence for distinct genetic effects associated with response to 35% CO₂

BACKGROUND

Carbon dioxide (CO2 ) hypersensitivity represents an individual difference response to breathing CO2 enriched air. People with a history of panic attacks or panic disorder are particularly prone to anxious response, suggesting that CO2 hypersensitivity is a robust risk marker of panic spectrum vulnerability.

METHODS

Twin pairs (n = 346) from the general population-based Norwegian NIPH Mental Health Study completed a measure of anxiety before and after vital capacity inhalation of 35% CO2 air and before and after inhalation of regular air. Three hypotheses regarding genetic factors for CO2 hypersensitivity were examined: (1) a single set of genetic risk factors impacts anxiety before exposure to CO2 and these same genes constitute the only genetic influences on anxiety in response to CO2 , (2) the genetic effects on pre-CO2 anxiety are entirely different from the genetic effects on anxiety in response to exposure to CO2 (i.e., new genetic effects), and (3) pre-CO2 anxiety influences anxiety in response to CO2 as well as unique genetic factors that become activated by respiratory stimulation.

RESULTS

Our results support the latter hypothesis for response to 35% CO2 , with additive genetic and unique environmental factors best fitting the data. Evidence of new genetic effects was observed, accounting for 20% unique variance in post 35% CO2 anxiety response. New genetic effects were not observed for anxiety ratings made post regular air where only preregular air anxiety ratings explained significant variance in this outcome.

CONCLUSIONS

These data suggest that there are distinct genetic factors associated with responsivity to respiratory stimulation via 35% CO2 .

Fear and panic in humans with bilateral amygdala damage

Decades of research have highlighted the amygdala’s influential role in fear. Surprisingly, we found that inhalation of 35% CO₂ evoked not only fear, but also panic attacks, in three rare patients with bilateral amygdala damage. These results indicate that the amygdala is not required for fear and panic, and make an important distinction between fear triggered by external threats from the environment versus fear triggered internally by CO₂.

Panic disorder and the respiratory system: clinical subtype and challenge tests

INTRODUCTION

Respiratory changes are associated with anxiety disorders, particularly panic disorder (PD). The stimulation of respiration in PD patients during panic attacks is well documented in the literature, and a number of abnormalities in respiration, such as enhanced CO2 sensitivity, have been detected in PD patients. Investigators hypothesized that there is a fundamental abnormality in the physiological mechanisms that control breathing in PD.

METHODS

The authors searched for articles regarding the connection between the respiratory system and PD, more specifically papers on respiratory challenges, respiratory subtype, and current mechanistic concepts.

CONCLUSIONS

Recent evidences support the presence of subclinical changes in respiration and other functions related to body homeostasis in PD patients. The fear network, comprising the hippocampus, medial prefrontal cortex, amygdala and its brainstem projections, may be abnormally sensitive in PD patients, and respiratory stimulants like CO2 may trigger panic attacks. Studies indicate that PD patients with dominant respiratory symptoms are particularly sensitive to respiratory tests compared to those who do not manifest dominant respiratory symptoms, representing a distinct subtype. The evidence of changes in several neurochemical systems might be the expression of the complex interaction among brain circuits.

Balance disturbances in asthmatic patients

OBJECTIVE

The aim of this study was to investigate balance control in asthmatic patients.

METHODS

Thirty subjects with controlled persistent asthma were compared with 30 non-asthmatic subjects who were matched by age and sex. Individuals who had received psychiatric treatment, demonstrated chronic musculoskeletal pain, had limited joint movements, or showed vestibular or other equilibrium disorders were excluded from both the groups to avoid biomechanical bias in the dynamic posturography. Balance control was evaluated with the subject standing still on a force platform under four different sensory test conditions. These conditions combined the subject's eyes being opened or closed with a fixed or mobile force platform. A mobile platform provides a somatosensory perturbation, and when associated with the eyes closed condition, only vestibular information is available to moderate balance control. Sensory manipulation provides a more sensitive condition to differentiate postural control between populations or pathologies. Data were sampled at 100 Hz in three 20-second trials and four postural conditions were assessed. The center of pressure (CoP) displacement values were used to calculate area and velocity in the medial-lateral and forward-backward directions. A two-factor analysis of variance with repeated measurements was applied to the data.

RESULTS

In comparison to the control group, the asthma group demonstrated a greater area of CoP displacement in conditions using the mobile force platform (with eyes opened or closed) and a higher velocity in forward-backward direction on the mobile platform with the eyes closed.

CONCLUSION

Asthmatic individuals presented a greater area for the CoP displacement under somatosensory perturbations and a higher velocity in the forward-backward direction when vestibular information only was made available. Our data suggest that balance needs to be evaluated in asthmatic patients.

Cigarette smoking, nicotine dependence and anxiety disorders: a systematic review of population-based, epidemiological studies

BACKGROUND

Multiple studies have demonstrated that rates of smoking and nicotine dependence are increased in individuals with anxiety disorders. However, significant variability exists in the epidemiological literature exploring this relationship, including study design (cross-sectional versus prospective), the population assessed (random sample versus clinical population) and diagnostic instrument utilized.

METHODS

We undertook a systematic review of population-based observational studies that utilized recognized structured clinical diagnostic criteria (Diagnostic and Statistical Manual of Mental Disorders (DSM) or International Classification of Diseases (ICD)) for anxiety disorder diagnosis to investigate the relationship between cigarette smoking, nicotine dependence and anxiety disorders.

RESULTS

In total, 47 studies met the predefined inclusion criteria, with 12 studies providing prospective information and 5 studies providing quasiprospective information. The available evidence suggests that some baseline anxiety disorders are a risk factor for initiation of smoking and nicotine dependence, although the evidence is heterogeneous and many studies did not control for the effect of comorbid substance use disorders. The identified evidence however appeared to more consistently support cigarette smoking and nicotine dependence as being a risk factor for development of some anxiety disorders (for example, panic disorder, generalized anxiety disorder), although these findings were not replicated in all studies. A number of inconsistencies in the literature were identified.

CONCLUSIONS

Although many studies have demonstrated increased rates of smoking and nicotine dependence in individuals with anxiety disorders, there is a limited and heterogeneous literature that has prospectively examined this relationship in population studies using validated diagnostic criteria. The most consistent evidence supports smoking and nicotine dependence as increasing the risk of panic disorder and generalized anxiety disorder. The literature assessing anxiety disorders increasing smoking and nicotine dependence is inconsistent. Potential issues with the current literature are discussed and directions for future research are suggested.

Sex, hormones, and stress: how they impact development and function of the carotid bodies and related reflexes

Progesterone and corticosterone are key modulators of the respiratory control system. While progesterone is widely recognized as an important respiratory stimulant in adult and newborn animals, much remains to be described regarding the underlying mechanisms. We review the potential implication of nuclear and membrane progesterone receptors in adults and in newborns. This raises intriguing questions regarding the contribution of progesterone as a protective factor against some respiratory control disorders during early life. We then discuss our current understanding of the central integration of stressful stimuli and the responses they elicit. The fact that this system interacts with the respiratory control system, either because both share some common neural pathways in the brainstem and hypothalamus, or because corticosterone directly modulates the function of the respiratory control network, is a fascinating field of research that has emerged over the past few years. Finally, we review the short- and long-term consequences of disruption of stress circuitry during postnatal development on these systems.

Association of CRHR1 and CRHR2 with major depressive disorder and panic disorder in a Japanese population

Major depressive disorder (MDD) and panic disorder (PD) are common and disabling medical disorders with stress and genetic components. Dysregulation of the stress response of the hypothalamic-pituitary-adrenal axis, including the corticotrophin-releasing hormone (CRH) signaling via primary receptors (CRHR1 and CRHR2), is considered to play a major role for onset and recurrence in MDD and PD. To confirm the association of CRHR1 and CRHR2 with MDD and PD, we investigated 12 single nucleotide polymorphisms (SNPs) (rs4076452, rs7209436, rs110402, rs242924, rs242940, and rs173365 for CRHR1 and rs4722999, rs3779250, rs2267710, rs1076292, rs2284217, and rs226771 for CRHR2) in MDD patients (n = 173), PD patients (n = 180), and healthy controls (n = 285). The SNP rs110402 and rs242924 in the CRHR1 gene and the rs3779250 in the CRHR2 gene were associated with MDD. The SNP rs242924 in the CRHR1 gene was also associated with PD. The T-A-T-G-G haplotype consisting of rs7209436 and rs173365 in CRHR1 was positively associated with MDD. The T-A haplotype consisting of rs7209436 and rs110402 in CRHR1 was positively associated with MDD. The C-C haplotype consisting of rs4722999 and rs37790 in CRHR1 was associated with PD. These results provide support for an association of CRHR1 and CRHR2 with MDD and PD.

Hypersensitivity to hypercapnia: definition/(s)

Empirical evidence indicates that panic disorder (PD) patients experience hypersensitivity to hypercapnia, a condition in which the blood level of carbon dioxide exceeds the normal value. The importance of this research line is substantial and indeed, hypercapnic hypersensitivity has been advanced as a possible endophenotype of panic. Definitions of "hypersensitivity," however, have varied. The purpose of this brief review is to delineate and critique different definitions of hypercapnic hypersensitivity. Several definitions - panic attack rate, panic symptoms including dyspnea, subjective anxiety, and respiratory disturbance - are explored. The review concludes that although no ideal definition has emerged, marked anxiety post-hypercapnia has substantial support as a putative trait marker of PD. The term "subjective hypersensitivity" (Coryell et al., 2001) is re-introduced to denote pronounced anxiety post-hypercapnia and recommended for use along with its previous definition: increased self-reported anxiety measured on a continuous visual analog scale, already widely in use. Due to the well-established link between panic and respiration, definitional candidates focusing on aberrant respiratory response - less investigated as trait markers of PD in high risk studies - warrant scrutiny as well. Several reasons why definitional clarity might be beneficial are presented, along with ideas for future research.

The panicolytic-like effect of fluoxetine in the elevated T-maze is mediated by serotonin-induced activation of endogenous opioids in the dorsal periaqueductal grey

Serotonin (5-HT), opioids and the dorsal periaqueductal grey (DPAG) have been implicated in the pathophysiology of panic disorder. In order to study 5-HT-opioid interaction, the opioid antagonist naloxone was injected either systemically (1 mg/kg, i.p.) or intra-DPAG (0.2 μg/0.5 μL) to assess its interference with the effect of chronic fluoxetine (10 mg/kg, i.p., daily for 21 days) or of intra-DPAG 5-HT (8 μg/0.5 μL). Drug effects were measured in the one-escape task of the rat elevated T-maze, an animal model of panic. Pretreatment with systemic naloxone antagonized the lengthening of escape latency caused by chronic fluoxetine, considered a panicolytic-like effect that parallels the drug's therapeutic response in the clinics. Pretreatment with naloxone injected intra-DPAG antagonized both the panicolytic effect of chronic fluoxetine as well as that of 5-HT injected intra-DPAG. Neither the performance of the inhibitory avoidance task in the elevated T-maze, a model of generalized anxiety nor locomotion measured in a circular arena was affected by the above drug treatments. These results indicate that the panicolytic effect of fluoxetine is mediated by endogenous opioids that are activated by 5-HT in the DPAG. They also allow reconciliation between the serotonergic and opioidergic hypotheses of panic disorder pathophysiology.

Temperament trait Harm Avoidance associates with μ-opioid receptor availability in frontal cortex: a PET study using [(11)C]carfentanil

Harm Avoidance is a temperament trait that associates with sensitivity to aversive and non-rewarding stimuli, higher anticipated threat and negative emotions during stress as well as a higher risk for affective disorders. The neurobiological correlates of interindividual differences in Harm Avoidance are largely unknown. We hypothesized that variability in Harm Avoidance trait would be explained by differences in the activity of μ-opioid system as the opioid system is known to regulate affective states and stress sensitivity. Brain μ-opioid receptor availability was measured in 22 healthy subjects using positron emission tomography and [(11)C]carfentanil, a selective μ-opioid receptor agonist. The subjects were selected from a large Finish population-based cohort (N=2075) on the basis of their pre-existing Temperament and Character Scores. Subjects scoring consistently in the upper (10) and lower (12) quartiles for the Harm Avoidance trait were studied. High Harm Avoidance score associated with high μ-opioid receptor availability (i.e. lower endogenous μ-opioid drive) in anterior cingulate cortex, ventromedial and dorsolateral prefrontal cortices and anterior insular cortex. These associations were driven by two subscales of Harm Avoidance; Shyness with Strangers and Fatigability and Asthenia. In conclusion, higher Harm Avoidance score in healthy subjects is associated with higher μ-opioid availability in regions involved in the regulation of anxiety as well as in the control of emotions, affective component of pain and interoceptive awareness. The results have relevance in the research of vulnerability factors for affective disorders.

New perspective on the pathophysiology of panic: merging serotonin and opioids in the periaqueductal gray

Panic disorder patients are vulnerable to recurrent panic attacks. Two neurochemical hypotheses have been proposed to explain this susceptibility. The first assumes that panic patients have deficient serotonergic inhibition of neurons localized in the dorsal periaqueductal gray matter of the midbrain that organize defensive reactions to cope with proximal threats and of sympathomotor control areas of the rostral ventrolateral medulla that generate most of the neurovegetative symptoms of the panic attack. The second suggests that endogenous opioids buffer normal subjects from the behavioral and physiological manifestations of the panic attack, and their deficit brings about heightened suffocation sensitivity and separation anxiety in panic patients, making them more vulnerable to panic attacks. Experimental results obtained in rats performing one-way escape in the elevated T-maze, an animal model of panic, indicate that the inhibitory action of serotonin on defense is connected with activation of endogenous opioids in the periaqueductal gray. This allows reconciliation of the serotonergic and opioidergic hypotheses of panic pathophysiology, the periaqueductal gray being the fulcrum of serotonin-opioid interaction.

Serotonin-2A receptor and catechol-O-methyltransferase polymorphisms in panic disorder

Catechol-O-methyltransferase (COMT) and serotonin receptor 2A (5HTR2A) polymorphisms have been investigated for their possible role in panic disorder (PD). The aim of this study was to investigate the genotype distribution of the COMT val158met and 5HTR2A 102T/C polymorphisms in PD. COMT val158met is a polymorphism at codon 158 that results in variations in COMT enzymatic activity with high- (H) and low-activity (L) alleles. The 5HTR2A 102T/C polymorphism comprises a T-to-C mutation at position 102. The effects of symptom severity, gender, and age of onset were also investigated. The participants were 105 outpatients with PD and 130 controls. The severity of the symptoms of PD was assessed by the Panic and Agoraphobia Scale (PAS). Polymorphisms of the 5HTR2A and COMT genes were identified using polymerase chain reaction and restriction fragment length polymorphism analysis. A significant relationship was found between the COMT Val158Met polymorphism and PD. No significant differences were found in genotype distributions or allele frequencies of the 5HTR2A polymorphisms between the PD and control groups. There were no significant relationships between the COMT and 5HTR2A polymorphisms and age of onset, gender, presence of agoraphobia, or PAS scores in the PD group (p>0.05).

Asthma severity, child security, and child internalizing: using story stem techniques to assess the meaning children give to family and disease-specific events

Children with persistent asthma are at increased risk for mental health problems. Although mechanisms of effect are not yet known, it may be that children are less trusting of the family as a source of support and security when they have more severe asthma. This study tested whether asthma severity is related to children's perceptions of insecurity in the family, and whether insecurity is in turn associated with child adjustment. Children (N = 168; mean age = 8 years) completed story stems pertaining to routine family events (e.g., mealtimes) and ambiguous but potentially threatening asthma events such as tightness in the chest. Responses were evaluated for the extent to which appraisals portrayed the family as responding in cohesive, security-provoking ways. Asthma severity was assessed by both objective lung function testing and primary caregiver report. Caregivers reported child symptomatology. Beyond medication adherence, caregiver education, and child age and gender, greater asthma severity predicted more internalizing and externalizing symptoms. Greater asthma severity, assessed using spirometry (but not parent report), was related to less secure child narratives of the family, which in turn related to more child internalizing symptoms. Results suggest that asthma can take a considerable toll on children's feelings of security and mental health. Furthermore, given the difficulty in assessing young children's perceptions, this study helps demonstrate the potential of story stem techniques in assessing children's appraisals of illness threat and management in the family.

Opioids and anxiety

The opioid system plays a crucial role in the neural modulation of anxiety. The involvement of opioid ligands and receptors in physiological and dysfunctional forms of anxiety is supported by findings from a wide range of preclinical and clinical studies, including clinical trials, experimental research, and neuroimaging, genetic, and epidemiological data. In this review we provide a summary of studies from a variety of research disciplines to elucidate the role of the opioid system in the neurobiology of anxiety. First, we report data from preclinical studies using animal models to examine the modulatory role of central opioid system on defensive responses conducive to fear and anxiety. Second, we summarize the human literature providing evidence that clinical and experimental human studies are consistent with preclinical models. The implication of these data is that activation of the opioid system leads to anxiolytic responses both in healthy subjects and in patients suffering from anxiety disorders. The role of opioids in suppressing anxiety may serve as an adaptive mechanism, collocated in the general framework of opioid neurotransmission blunting acute negative and distressing affective responses.

Biomarkers in development of psychotropic drugs

Biomarkers have been receiving increasing attention, especially in the field of psychiatry. In contrast to the availability of potent therapeutic tools including pharmacotherapy, psychotherapy, and biological therapies, unmet needs remain in terms of onset of action, stability of response, and further improvement of the clinical course. Biomarkers are objectively measured characteristics which serve as indicators of the causes of illnesses, their clinical course, and modification by treatment. There exist a variety of markers: laboratory markers which comprise the determination of genetic and epigenetic markers, neurotransmitters, hormones, cytokines, neuropeptides, enzymes, and others as single measures; electrophysiological markers which usually comprise electroencephalography (EEG) measures, and in particular sleep EEG and evoked potentials, magnetic encephalography, electrocardiogram, facial electromyography, skin conductance, and others; brain imaging techniques such as cranial computed tomography, magnetic resonance imaging, functional MRl, magnetic resonance spectroscopy, positron emission tomography, and single photon emission computed tomography; and behavioral approaches such as cue exposure and challenge tests which can be used to induce especially emotional processes in anxiety and depression. Examples for each of these domains are provided in this review. With a view to developing more individually tailored therapeutic strategies, the characterization of patients and the courses of different types of treatment will become even more important in the future.

Interaction between δ opioid receptors and benzodiazepines in CO₂-induced respiratory responses in mice

The false-suffocation hypothesis of panic disorder (Klein, 1993) suggested δ-opioid receptors as a possible source of the respiratory dysfunction manifested in panic attacks occurring in panic disorder (Preter and Klein, 2008). This study sought to determine if a lack of δ-opioid receptors in a mouse model affects respiratory response to elevated CO₂, and whether the response is modulated by benzodiazepines, which are widely used to treat panic disorder. In a whole-body plethysmograph, respiratory responses to 5% CO₂ were compared between δ-opioid receptor knockout mice and wild-type mice after saline, diazepam (1mg/kg), and alprazolam (0.3mg/kg) injections. The results show that lack of δ-opioid receptors does not affect normal response to elevated CO₂, but does prevent benzodiazepines from modulating that response. Thus, in the presence of benzodiazepine agonists, respiratory responses to elevated CO₂ were enhanced in δ-opioid receptor knockout mice compared to wild-type mice. This suggests an interplay between benzodiazepine receptors and δ-opioid receptors in regulating the respiratory effects of elevated CO₂, which might be related to CO₂ induced panic.

Unstable maternal environment, separation anxiety, and heightened CO2 sensitivity induced by gene-by-environment interplay

BACKGROUND

In man, many different events implying childhood separation from caregivers/unstable parental environment are associated with heightened risk for panic disorder in adulthood. Twin data show that the occurrence of such events in childhood contributes to explaining the covariation between separation anxiety disorder, panic, and the related psychobiological trait of CO(2) hypersensitivity. We hypothesized that early interference with infant-mother interaction could moderate the interspecific trait of response to CO(2) through genetic control of sensitivity to the environment.

METHODOLOGY

Having spent the first 24 hours after birth with their biological mother, outbred NMRI mice were cross-fostered to adoptive mothers for the following 4 post-natal days. They were successively compared to normally-reared individuals for: number of ultrasonic vocalizations during isolation, respiratory physiology responses to normal air (20%O(2)), CO(2)-enriched air (6% CO(2)), hypoxic air (10%O(2)), and avoidance of CO(2)-enriched environments.

RESULTS

Cross-fostered pups showed significantly more ultrasonic vocalizations, more pronounced hyperventilatory responses (larger tidal volume and minute volume increments) to CO(2)-enriched air and heightened aversion towards CO(2)-enriched environments, than normally-reared individuals. Enhanced tidal volume increment response to 6%CO(2) was present at 16-20, and 75-90 postnatal days, implying the trait's stability. Quantitative genetic analyses of unrelated individuals, sibs and half-sibs, showed that the genetic variance for tidal volume increment during 6%CO(2) breathing was significantly higher (Bartlett χ = 8.3, p = 0.004) among the cross-fostered than the normally-reared individuals, yielding heritability of 0.37 and 0.21 respectively. These results support a stress-diathesis model whereby the genetic influences underlying the response to 6%CO(2) increase their contribution in the presence of an environmental adversity. Maternal grooming/licking behaviour, and corticosterone basal levels were similar among cross-fostered and normally-reared individuals.

CONCLUSIONS

A mechanism of gene-by-environment interplay connects this form of early perturbation of infant-mother interaction, heightened CO(2) sensitivity and anxiety. Some non-inferential physiological measurements can enhance animal models of human neurodevelopmental anxiety disorders.

Controlled cross-over study in normal subjects of naloxone-preceding-lactate infusions; respiratory and subjective responses: relationship to endogenous opioid system, suffocation false alarm theory and childhood parental loss

BACKGROUND

The expanded suffocation false alarm theory (SFA) hypothesizes that dysfunction in endogenous opioidergic regulation increases sensitivity to CO2, separation distress and panic attacks. In panic disorder (PD) patients, both spontaneous clinical panics and lactate-induced panics markedly increase tidal volume (TV), whereas normals have a lesser effect, possibly due to their intact endogenous opioid system. We hypothesized that impairing the opioidergic system by naloxone could make normal controls parallel PD patients' response when lactate challenged. Whether actual separations and losses during childhood (childhood parental loss, CPL) affected naloxone-induced respiratory contrasts was explored. Subjective panic-like symptoms were analyzed although pilot work indicated that the subjective aspect of anxious panic was not well modeled by this specific protocol.

METHOD

Randomized cross-over sequences of intravenous naloxone (2 mg/kg) followed by lactate (10 mg/kg), or saline followed by lactate, were given to 25 volunteers. Respiratory physiology was objectively recorded by the LifeShirt. Subjective symptomatology was also recorded.

RESULTS

Impairment of the endogenous opioid system by naloxone accentuates TV and symptomatic response to lactate. This interaction is substantially lessened by CPL.

CONCLUSIONS

Opioidergic dysregulation may underlie respiratory pathophysiology and suffocation sensitivity in PD. Comparing specific anti-panic medications with ineffective anti-panic agents (e.g. propranolol) can test the specificity of the naloxone+lactate model. A screen for putative anti-panic agents and a new pharmacotherapeutic approach are suggested. Heuristically, the experimental unveiling of the endogenous opioid system impairing effects of CPL and separation in normal adults opens a new experimental, investigatory area.

Amygdalar hyperactivity, a fear-related link between panic disorder and mesiotemporal epilepsy

The sudden onset, short duration and stereotyped features of panic attacks, and the fear aura of seizures starting at the mesial aspects of the temporal lobe, suggest common mechanisms underlying panic disorder (PD) and mesiotemporal epilepsy (MTLE). However, current consensus emphasizes the importance of differentiating the two entities based on 1) intact consciousness in panic attacks, 2) poor response to antiepileptics, and 3) unsuccessful electrophysiological attempts to demonstrate a relationship. We report two cases with a diagnosis of PD that had been partially responsive to first line treatments. During the EEG session, both patients developed panic symptoms with minimal EEG changes in response to paper bag-hyperventilation (PB-HV), and several minutes later presented a clear ictal EEG pattern associated with very different clinical symptoms, but both with strong fear content. Z-scored LORETA analysis showed increased current source densities (CSD) at the right amygdala in both subjects during the induced panic symptoms. Several areas were involved during the seizure, different in each subject. Yet, a very significant increase at the amygdala was found in both cases. The LORETA Z-scored source correlation (LSC) analysis also showed similar abnormal patterns during the panic symptoms in both patients, and marked differences during the seizure. These findings show a major role of amygdalar hyperactivity in both fear-related conditions for the two patients, and are discussed in relation to existing models of PD in general. Abnormal overactivation at mesiotemporal regions is poorly represented at the surface recordings but can be detected by the appropriate analytical techniques.

CCK-4: Psychophysiological conditioning elicits features of spontaneous panic attacks

INTRODUCTION

Cholecystokinin-tetrapeptide (CCK-4) is an established model to generate subjective panic anxiety. CCK-4 injection also results in consistent and dose-dependent rise of stress hormones. Effects other than upon subjective panic and stress hormone activity have barely been examined. The purpose of the study was to investigate CCK-4 effects on emotional facial expression and especially on fear relevant facial muscles establishing therewith a more objective method to measure subjective panic anxiety.

METHODS

20 healthy male subjects were randomly and double-blindedly assigned in two groups (dose groups), each of which was investigated three times once with placebo and twice with 25 μg or 50 μg CCK-4 respectively. Subjects of each group were randomly assigned in two different balanced orders of investigations: CCK-CCK-Placebo vs. Placebo-CCK-CCK. Facial muscle and hypothalamo-pituitary-adrenocortical (HPA)-axis activity were recorded.

RESULTS

CCK-4 led dose-dependently to an increase of panic anxiety, an activation of fear relevant facial muscles and a rise of stress hormones. Whereas placebo administration before CCK-4 revealed no significant panic and stress response, during placebo following CCK-4 stimulations a psychophysiological conditioning effect could be observed without rise in HPA-axis activity.

DISCUSSION

Our findings indicate the possibility to measure different intensities of panic anxiety and conditioning effects with a facial EMG method. Dissociation of HPA-activity and fear relevant facial muscle activity is in accordance with former results about spontaneous panic attacks.

Acute and chronic treatment with serotonin reuptake inhibitors exert opposite effects on respiration in rats: possible implications for panic disorder

Prompted by the suggested importance of respiration for the pathophysiology of panic disorder, we studied the influence of serotonin reuptake inhibitors (SRIs) as well as other serotonin-modulating compounds on respiration in freely moving rats. The effect on respiration after acute administration of compounds enhancing synaptic levels of serotonin, that is, the serotonin reuptake inhibitors paroxetine and fluoxetine, the serotonin-releasing agents m-chlorophenylpiperazine and d-fenfluramine, and the selective 5-HT1A antagonist WAY-100635, were investigated. All serotonin-releasing substances decreased respiratory rate in unrestrained, awake animals, suggesting the influence of serotonin on respiratory rate under these conditions to be mainly inhibitory. In line with a previous study, rats administered fluoxetine for 23 days or more, on the other hand, displayed an enhanced respiratory rate. The results reinforce the assumption that the effect of subchronic administration of a serotonin reuptake inhibitor on certain serotonin-regulated parameters may be opposite to that obtained after acute administration. We suggest that our observations may be of relevance for the fact that acute administration of SRIs, d-fenfluramine, or m-chlorophenylpiperazine often is anxiogenic in panic disorder patients, and that weeks of administration of an SRI leads to a very effective prevention of panic.

Dorsal hippocampal opioidergic system modulates anxiety-like behaviors in adult male Wistar rats

AIMS

In the present study, we investigated the possible influence of the opioidergic system of the dorsal hippocampus on anxiety-like behaviors.

METHODS

Elevated plus-maze, which is one of the methods used for testing anxiety, was used in the present study. Rats were anesthetized with ketamine and xylazine and special cannulas were inserted stereotaxically into the CA1 region of the dorsal hippocampus. After 1 week of recovery, the effects of intra-CA1 administration of morphine (0.25, 0.5, 1 and 2 µg/rat; 1 µl/rat; 0.5 µl/in each side), naloxone (2, 4, 6 and 8 µg/rat), enkephalin (1, 2, 5 and 10 µg/rat) and naltrindole (0.25, 0.5, 1 and 2 µg/rat) on percentage open arm time (%OAT) and percentage open arm entries (%OAE) were determined.

RESULTS

Bilateral administration of morphine into CA1 decreases %OAT and %OAE, indicating an anxiogenic-like effect. Intra-CA1 injection of naloxone, an opioid receptor antagonist, increased both %OAT and %OAE, parameters of anxiolytic-like behavior. Bilateral administration of δ-opioid receptor agonist, [D-Pen(2,5) ]-enkephalin acetate hydrate into the CA1, induced an anxiolytic-like effect. Furthermore, intra-CA1 injection of δ-opioid receptor antagonist, naltrindole hydrochloride, increased anxiety-related behaviors.

CONCLUSIONS

The results of the present study demonstrate that activation of μ-opioid receptors in this area produce an anxiogenic response while activation of δ-opioid receptors produces an anxiolytic response.

Temporal stability and coherence of anxiety, dyspnea, and physiological variables in panic disorder

Twenty-five panic disorder (PD) patients, 19 social phobics (SP), and 20 healthy controls (HC) sat quietly for 15 min, rating their anxiety and dyspnea every 30s while respiratory, cardiovascular, and electrodermal responses were recorded. No panic attacks were reported. For self-reported anxiety and dyspnea, within-subject variability over time was higher in PD than in SP or HC. In PD within-subject correlations across 30-s epochs were significant for (a) self-reported anxiety versus dyspnea, end-tidal pCO2, minute volume, duty cycle, skin conductance level, and interbeat interval, and for (b) dyspnea versus end-tidal pCO2, minute volume, tidal volume, and inspiratory flow rate. Several positive or negative correlations were greater in PD than in other groups. Thus in PD, experienced anxiety and dyspnea are temporally unstable but are correlated with each other and with fluctuations in respiratory and autonomic variables, even in the absence of panic attacks.

The effects of opioid receptor blockade on experimental panic provocation with CO2

Several reports have linked, among other aspects, the role of an opioid system in respiratory physiology with underlying mechanisms of panic attacks. The involvement of the opioid system in experimental panic is to be further probed. This study aimed to determine whether opioid blockade would increase panic-related symptomatology on provocation with 35% CO2 inhaled by healthy volunteers. Participants in a double-blind, randomised crossover design orally received either 50 mg of naltrexone or placebo. Most subjects undertook a double inhalation of 35% CO2 one hour after pre-medication, and a separate group did so after five hours. The reactivity to CO2 and the symptoms elicited by naltrexone alone were measured. Among other findings, naltrexone pre-medication alone elicited significant increments in panic-related symptoms. Responses to CO2 were not significantly different between conditions in either group. These preliminary findings suggest that exposure to opioid blockade alone can potentially elicit symptoms that resemble panic, however, without modifying the response to experimental panic provocation with 35% CO2.

Caffeine challenge and breath-holding duration in patients with panic disorder

OBJECTIVE

Breath-holding (BH) has been used as a simple probe to increase endogenous carbon dioxide (CO2). In patients with Panic Disorder (PD), lower baseline BH duration is associated with caffeine-induced panic attacks. In this paper, we assessed BH duration in PD patients in relation to panic attacks induced by caffeine intake.

METHODS

BH duration and state anxiety were assessed in 40 PD patients (12 males), both at baseline and after a 400-mg caffeine challenge test.

RESULTS

Patients panicking after caffeine administration (14 patients, 4 males) exhibited a significant reduction of their post-challenge BH duration, while no change of the BH duration was observed in non-panicking patients (26 patients, 8 males). Reduction in post-challenge BH duration was not related to higher anxiety levels--as reflected in the State-Trait Anxiety Inventory-State Form scores--independently of the occurrence of a panic attack. Panickers exhibited significantly lower baseline BH duration, compared to non-panickers.

CONCLUSIONS

Our findings indicate that in PD patients, caffeine-induced panic attacks are strongly associated with a significant reduction of BH duration at both pre- and post-challenge. Jointly, these findings suggest that in a subgroup of PD patients, sensitivity to endogenous CO2 accumulation may underlie both the lower BH durations and the caffeine-induced panic attacks. In this subgroup of PD patients, caffeine might exert its panicogenic properties through the exacerbation of patients' already pathological hypersensitivity to CO2 accumulation, as indicated by both the significant decrease of their BH duration at post-challenge and by their significantly lower baseline BH duration respectively.

World Federation of Societies of Biological Psychiatry (WFSBP) guidelines for the pharmacological treatment of anxiety, obsessive-compulsive and post-traumatic stress disorders - first revision

In this report, which is an update of a guideline published in 2002 (Bandelow et al. 2002, World J Biol Psychiatry 3:171), recommendations for the pharmacological treatment of anxiety disorder, obsessive-compulsive disorder (OCD) and post-traumatic stress disorder (PTSD) are presented. Since the publication of the first version of this guideline, a substantial number of new randomized controlled studies of anxiolytics have been published. In particular, more relapse prevention studies are now available that show sustained efficacy of anxiolytic drugs. The recommendations, developed by the World Federation of Societies of Biological Psychiatry (WFSBP) Task Force for the Pharmacological Treatment of Anxiety, Obsessive-Compulsive and Post-traumatic Stress Disorders, a consensus panel of 30 international experts, are now based on 510 published randomized, placebo- or comparator-controlled clinical studies (RCTs) and 130 open studies and case reports. First-line treatments for these disorders are selective serotonin reuptake inhibitors (SSRIs), serotonin-noradrenaline reuptake inhibitors (SNRIs) and the calcium channel modulator pregabalin. Tricyclic antidepressants (TCAs) are equally effective for some disorders, but many are less well tolerated than the SSRIs/SNRIs. In treatment-resistant cases, benzodiazepines may be used when the patient does not have a history of substance abuse disorders. Potential treatment options for patients unresponsive to standard treatments are described in this overview. Although these guidelines focus on medications, non-pharmacological were also considered. Cognitive behavioural therapy (CBT) and other variants of behaviour therapy have been sufficiently investigated in controlled studies in patients with anxiety disorders, OCD, and PTSD to support them being recommended either alone or in combination with the above medicines.

Short-term full kindling of the amygdala dissociates natural and periaqueductal gray-evoked flight behaviors of the rat

Panic attacks present a high comorbidity with agoraphobia, separation anxiety and generalized anxiety disorder. Nevertheless, while panic attacks have been frequently equated to fear, the relationship of panic disorder with specific phobias remains uncertain. The combination of experimental models of panic and phobias could but afford valuable information about both the comorbidity and causation of these disorders. As it regards, while the defensive behaviors produced by stimulation of dorsal periaqueductal gray matter (DPAG) resemble a panic attack, resistance to capture (RC) behaviors that ensue the kindling of the amygdala (AMY) are reminiscent of a phobic reaction. Therefore, this study examined the thresholds of DPAG-evoked panic-like behaviors in rats showing RC behaviors. Rats bearing electrodes in the DPAG and right AMY were subjected to either the full- (Kin-F) or sham- (Kin-S) kindling of AMY. RC behaviors were evaluated throughout both kindling procedures. Thresholds of DPAG-evoked defensive behaviors were recorded before and after the kindling. Moreover, performances of Kin-F and Kin-S rats in the elevated plus-maze were compared to those of intact controls. Data showed that Kin-F and Kin-S rats perform similarly in the elevated plus-maze, thereby making AMY-kindled rats unlikely as a model of generalized anxiety disorder. On the other hand, whereas the RC is characterized by a marked facilitation of natural freezing and flight behaviors, DPAG-evoked freezing (immobility and exophthalmus) and flight (galloping) behaviors were unexpectedly attenuated. Data suggest that RC is mediated by circuits distinct from those of DPAG-evoked defensive behaviors. Consequently, panic and phobic attacks may be mediated by different mechanisms as well.

Carbon dioxide-induced emotion and respiratory symptoms in healthy volunteers

A number of evidences have established that panic and respiration are closely related. Clinical studies indicated that respiratory sensations constitute a discrete cluster of panic symptoms and play a major role in the pathophysiology of panic. The aim of the present study was to explore the phenomenology of an experimental model of panic in healthy volunteers based on the hypothesis that: (1) we can isolate discrete clusters of panic symptoms, (2) respiratory symptoms represent a distinct cluster of panic symptoms, and (3) respiratory symptoms are the best predictor of the subjective feeling of panic, as defined in the DSM IV criteria.Sixty-four healthy volunteers received a double inhalation of four mixtures containing 0, 9, 17.5 and 35% CO(2,) respectively, in a double-blind, cross-over, random design. An electronic visual analog scale and the Panic Symptom List (PSL) were used to assess subjective 'fear/discomfort' and panic symptoms, respectively. Statistical analyses consisted of Spearman's correlations, a principal component factor analysis of the 13 PSL symptoms, and linear regressions analyses.The factor analysis extracted three clusters of panic symptoms: respiratory, cognitive, and neurovegetative (r(2)=0.65). Respiratory symptoms were highly related to subjective feeling of fear/discomfort specifically in the CO(2)-enriched condition. Moreover, the respiratory component was the most important predictor of the subjective feeling of 'fear/discomfort' (beta=0.54).The discrete clusters of symptoms observed in this study were similar to those elicited in panic attacks naturally occurring in patients affected by panic disorder. Consistent with the idea that respiration plays a crucial role in the pathophysiology of panic, we found that respiratory symptoms were the best predictors the subjective state defined in the DSM IV criteria for panic.