Serotonin function in panic disorder: important, but why?

How ambient temperature affects mood: an ecological momentary assessment study in Switzerland

BACKGROUND

Recent research has suggested that an increase in temperature can negatively affect mental health and increase hospitalization for mental illness. It is not clear, however, what factors or mechanisms mediate this association. We aimed to (1) investigate the associations between ambient temperatures and bad daily mood, and (2) identify variables affecting the strength of these associations (modifiers) including the time, the day of the week and the year of the mood rating, socio-demographic characteristics, sleep quality, psychiatric disorders and the personality trait neuroticism in the community.

METHODS

Data stemmed from the second follow-up evaluation of CoLaus|PsyCoLaus, a prospective cohort study conducted in the general population of Lausanne (Switzerland). The 906 participants rated their mood level four times a day during seven days using a cell phone app. Mixed-effects logistic regression was used to determine the association between daily maximum temperature and mood level. Participant ID was inserted as a random effect in the model, whereas the time of the day, the day of the week and the year were inserted as fixed effects. Models were controlled for several confounders (socio-demographic characteristics, sleep quality, weather parameters and air pollutants). Stratified analyses were conducted based on socio-demographic characteristics, sleep quality, presence of psychiatric disorders or a high neuroticism.

RESULTS

Overall, the probability of having a bad mood for the entire day decreased by 7.0% (OR: 0.93: 95% CI 0.88, 0.99) for each 5 °C increase in maximum temperature. A smaller and less precise effect (-3%; OR: 0.97: 95% CI 0.91, 1.03) was found when controlling for sunshine duration. A higher association was found in participants with bipolar disorder (-23%; OR: 0.77: 95% CI 0.51, 1.17) and in participants with a high neuroticism (-13%; OR: 0.87 95% CI 0.80, 0.95), whereas the association was reversed for participants with anxiety (20%; OR: 1.20: 95% CI 0.90, 1.59), depression (18%; OR: 1.18 95% CI 0.94, 1.48) and schizophrenia (193%; OR: 2.93 95% CI 1.17, 7.73).

CONCLUSIONS

According to our findings, rising temperatures may positively affect mood in the general population. However, individuals with certain psychiatric disorders, such as anxiety, depression, and schizophrenia, may exhibit altered responses to heat, which may explain their increased morbidity when exposed to high temperatures. This suggests that tailored public health policies are required to protect this vulnerable population.

The role of the dorsolateral prefrontal cortex in control of skin sympathetic nerve activity in humans

The dorsolateral prefrontal cortex (dlPFC) is primarily involved in higher order executive functions, with there being evidence of lateralization. Brain imaging studies have revealed its link to the generation of skin sympathetic nerve activity (SSNA), which is elevated in states of emotional arousal or anxiety. However, no studies have directly explored dlPFC influences on SSNA. Transcranial alternating current stimulation (-2 to 2 mA, 0.08 Hz, 100 cycles) was applied between the left or right dlPFC and nasion via surface electrodes. Spontaneous bursts of SSNA were recorded from the common peroneal nerve via a tungsten microelectrode in 21 healthy participants. The modulation index was calculated for each stimulation paradigm by constructing cross-correlation histograms between SSNA and the sinusoidal stimulus. Stimulation of the dlPFC caused significant modulation of SSNA, but there was no significant difference in the median modulation index across sides. Stimulation also caused cyclic modulation of skin blood flow and sweat release. We have shown for the first time that stimulation of the dlPFC causes modulation of SSNA, also reflected in the effector-organ responses. This supports a role for the dlPFC in the control of SSNA, which likely contributes to the ability of emotions to bring about cutaneous vasoconstriction and sweat release.

Altered DNA Methylation of the Serotonin Transporter Gene Associated with Early Life Stress and White Matter Microalterations in Korean Patients with Panic Disorder

INTRODUCTION

Changes in the DNA methylation of 5-HTTLPR are associated with the pathophysiology of panic disorder (PD). This study was conducted to investigate the association between stressful life events and the level of 5-HTTLPR methylation in patients with PD. We also examined whether these factors were associated with white matter alterations in psychological trauma-related regions.

METHODS

The participants comprised 232 patients with PD and 93 healthy adults of Korean descent. DNA methylation levels of five cytosine-phosphate-guanine (CpG) sites in the 5-HTTLPR region were analyzed. Voxel-wise statistical analysis of diffusion tensor imaging data was performed within the trauma-related regions.

RESULTS

PD patients showed significantly lower levels of the DNA methylation at 5-HTTLPR 5 CpG sites than healthy controls. In patients with PD, the DNA methylation levels at 5-HTTLPR 5 CpG sites showed significant negative association with the parental separation-related psychological distress, and positive correlations with the fractional anisotropy values of the superior longitudinal fasciculus (SLF) which might be related to trait anxiety.

CONCLUSION

Early life stress was significantly associated with DNA methylation levels at 5-HTTLPR related to the decreased white matter integrity in the SLF region in PD. Decreased white matter connectivity in the SLF might be related to trait anxiety and is vital to the pathophysiology of PD.

A midbrain-reticulotegmental circuit underlies exaggerated startle under fear emotions

Exaggerated startle has been recognized as a core hyperarousal symptom of multiple fear-related anxiety disorders, such as post-traumatic stress disorder (PTSD) and panic disorder. However, the mechanisms driving this symptom are poorly understood. Here we reveal a neural projection from dorsal raphe nucleus (DRN) to a startle-controlling center reticulotegmental nucleus (RtTg) that mediates enhanced startle response under fear condition. Within RtTg, we identify an inhibitory microcircuit comprising GABAergic neurons in pericentral RtTg (RtTgP) and glutamatergic neurons in central RtTg (RtTgC). Inhibition of this RtTgP-RtTgC microcircuit leads to elevated startle amplitudes. Furthermore, we demonstrate that the conditioned fear-activated DRN 5-HTergic neurons send inhibitory projections to RtTgP GABAergic neurons, which in turn upregulate neuronal activities of RtTgC glutamatergic neurons. Chemogenetic activation of the DRN-RtTgP projections mimics the increased startle response under fear emotions. Moreover, conditional deletion of 5-HT_1B receptor from RtTgP GABAergic neurons largely reverses the exaggeration of startle during conditioned fear. Thus, our study establishes the disinhibitory DRN-RtTgP-RtTgC circuit as a critical mechanism underlying exaggerated startle under fear emotions, and provides 5-HT_1B receptor as a potential therapeutic target for treating hyperarousal symptom in fear-associated psychiatric disorders.

Heart-brain interactions in cardiac and brain diseases: why sex matters

Cardiovascular disease and brain disorders, such as depression and cognitive dysfunction, are highly prevalent conditions and are among the leading causes limiting patient's quality of life. A growing body of evidence has shown an intimate crosstalk between the heart and the brain, resulting from a complex network of several physiological and neurohumoral circuits. From a pathophysiological perspective, both organs share common risk factors, such as hypertension, diabetes, smoking or dyslipidaemia, and are similarly affected by systemic inflammation, atherosclerosis, and dysfunction of the neuroendocrine system. In addition, there is an increasing awareness that physiological interactions between the two organs play important roles in potentiating disease and that sex- and gender-related differences modify those interactions between the heart and the brain over the entire lifespan. The present review summarizes contemporary evidence of the effect of sex on heart-brain interactions and how these influence pathogenesis, clinical manifestation, and treatment responses of specific heart and brain diseases.

Spontaneous Ejaculation: A Focused Review for the Clinicians

INTRODUCTION

The process of ejaculation has important meanings not only for its association with orgasm but also for the timing to ejaculate in the context of sexual activity. Spontaneous (involuntary) ejaculation (SE) without any sexual stimulation is a distressing symptom. Our understanding of SE is limited. Unfortunately, many physicians are not aware of these cases.

OBJECTIVES

The objective of this study is to describe the etiopathogenesis, clinical features, diagnosis, and treatment options for SE.

METHODS

We searched the literature for publications on "SE," "spontaneous emission" or "involuntary ejaculation," and factors influencing SE in the PUBMED/MEDLINE, Scopus, Cochrane Library, EMBASE, PsycINFO, ProQuest, Academic Search Complete database, Google Scholar, and CINAHL databases from inception to August 2020.

RESULTS

The literature search yielded 36 relevant publications reporting on 43 patients with SE. Attempts to explain the cause of pathologic SE have included 4 etiological groups (spinal cord lesions, psychological causes, rabies, and drug-induced). The underlying mechanisms responsible for induction of SE may include increased adrenergic activity, overactivity in dopaminergic system, decreased serotonergic activity, damage of descending inhibitory pathway, or penile hyperexcitability. SE may occur in the absence of an identifiable trigger or may be triggered by non-sexual circumstances (micturition, defecation, glans touch, anxiety, panic attack, or school examinations). Treatment options include psychoanalytic treatment, paroxetine, citalopram, sertraline, silodosin, and anxiolytics. In drug-induced SE, dose reduction and drug withdrawal with or without switching to another drug may relief SE.

CONCLUSIONS

SE is one of the least reported ejaculatory dysfunction. The key feature shared in common by these men is SE without any sexual thoughts or fantasies, may be triggered by non-sexual contexts, rarely associated with orgasm or erection. Treatment by psychoanalytic treatment and pharmacotherapy may be helpful. Further research might explore the definite underlying mechanisms. Abdel-Hamid IA, Ali OI. Spontaneous Ejaculation: A Focused Review for the Clinicians. Sex Med Rev 2021;9:406-422.

Emergency department visits for panic attacks and ambient temperature: A time-stratified case-crossover analysis

BACKGROUND

Panic disorder is a common anxiety disorder affecting up to 5% of the population. Although its pathogenesis is unclear, evidence about its association with ambient temperature is limited. We aimed to investigate the association between short-term exposure to increased ambient temperature and exacerbation of panic attacks requiring emergency department visits.

METHODS

From the national emergency database of South Korea, we identified 1,926 patients who presented with panic attacks at the emergency department in Seoul from 2008 to 2014. Using a time-stratified case-crossover design and conditional logistic regression analysis, we compared ambient temperature levels on emergency department visits and correspondingly matched-control days.

RESULTS

Increased ambient temperature levels were significantly associated with panic attacks. The risk of a panic attack increased by 2.2% (95% confidence interval, 0.7-3.8%) per every 1°C increase in temperature. This association was significant after adjusting for air pollutants.

CONCLUSIONS

Our results provide new evidence that short-term exposure to increased ambient temperature may increase the risk of exacerbation of panic attacks. These findings may provide a basis for further research to establish the association between panic attacks and ambient temperature, thus establishing preventive measures for panic attacks.

The serotonin transporter gene polymorphism (SLC6A4) and risk for psychiatric morbidity and comorbidity in the Baltimore ECA follow-up study

BACKGROUND

The human serotonin transporter (SERT) gene polymorphism (5HTTLPR) has been associated with multiple psychiatric disorders, including major depression, anxiety disorders, and substance use disorders. This study investigated the association between 5HTTLPR and psychiatric morbidity and comorbidity in a psychiatrist-examined population sample.

METHODS

628 participants, mean age 48.3 years old, were assessed by psychiatrists using the Schedules for Clinical Assessment in Neuropsychiatry. Associations between 5HTTLPR and the prevalence, comorbidity, and time-to-diagnoses for 16 psychiatric conditions were evaluated, using several analytical approaches.

RESULTS

The SERT S allele was significantly associated with an increased lifetime prevalence of panic disorder. There was a "protective" association between SERT gene S allele carrier status and the risk of obsessive-compulsive disorder (OCD) in time-to-event analysis. Carriers of the S allele had a significant increased risk of two specific comorbid disorder pairs: major depressive disorder (MDD) and social phobia, and MDD and agoraphobia. Overall, there was no increased risk of receiving an initial or an additional diagnosis for a mental disorder in the SERT S allele carriers CONCLUSIONS: The findings suggest that the S allele carrier status is associated with an increased prevalence of panic disorder in a community sample. There was an increased risk for comorbidity in a more homogeneous subgroup of cases with MDD and social phobia, as well as or agoraphobia. Our findings suggest a specific effect of the SERT promoter gene polymorphism on a subgroup of individuals identifiable by their comorbidity.

The association between serotonin-related gene polymorphisms and susceptibility and early sertraline response in patients with panic disorder

BACKGROUND

A number of studies have shown that genetic factor plays an important role in etiology of panic disorder (PD). The aim of the present study was to examine the association of serotonin-related gene polymorphisms with PD risk. Then, we analyzed the correlation between these gene polymorphisms and response to sertraline drug.

METHODS

Two hundred thirty-three patients with PD and 231 healthy controls were enrolled in the study. Panic Disorder Severity Scale (PDSS) were administered to all subjects, and all patients in the study were also assessed after 4 weeks of treatment. The SLC6A4(rs140701, rs3813034, 5-HTTLPR and STin2), 5-HTR1A rs6295, 5-HTR2A rs6313 and COMT rs4680 gene polymorphisms were genotyped and assessed for the potential association.

RESULTS

The allelic model showed that the SLC6A4 rs140701 polymorphism variant was significantly associated with increased risk of PD (OR = 0.624, 95% CI 0.450-0.864, p < 0.05), and a significant result was found in the dominant model (OR = 0.546; 95% CI, 0.371-0.804, p < 0.05). There was a significant difference in allele and genotype frequency between responders and nonresponders in the 5-HTTLPR polymorphism (OR = 0.205, 95% CI 0.128-0.328; OR = 0.249, 95% CI 0.155-0.401, both p < 0.001), indicating the PD patients with S-allele had a poorer response to sertraline than L-allele carriers.

CONCLUSIONS

The present study suggests that the SLC6A4 rs140701 polymorphism variant may be associated with susceptibility to PD, and 5-HTTLPR polymorphism may be a predictor of response to sertraline in the treatment of PD.

Changes in mean platelet volume and hematologic indices in patients with panic disorder due to oxidative stress

OBJECTIVE

Cardiovascular disorders are common in patients with panic disorder (PD), usually mediated by platelets. The present study was conducted to evaluate oxidative stress conditions and complete analysis of blood cells in patients with PD.

SETTING AND SAMPLE POPULATION

Sixty healthy individuals and 60 patients were included in the study. Whole blood and serum samples were obtained from patients and controls.

MATERIALS & METHOD

Hematological studies, including blood cells count, hemoglobin, and hematocrit, were carried out on whole blood samples. In addition, oxidative stress indices including total antioxidant capacity, free oxygen species, and malondialdehyde concentration were measured in serum samples.

RESULTS

Results showed that patients with PD had a significant increase in mean platelet volume index (MPV), platelet distribution width (PDW), red blood cell distribution width (RDW), and mean corpuscular hemoglobin concentration (MCHC) compared with healthy subjects (p < .05). Also, oxidative stress indices were significantly elevated in patients with PD compared with control group (p < .05).

CONCLUSION

Elevated MPV is a hematologic indicator for patients with PD. This disorder may be caused by impaired serotonin metabolism, resulting in increased oxidative stress, as well as in platelet serotonin transporters. Regarding elevated oxidative stress, the risk of cardiovascular complications is high in patients with PD.

Panic disorder respiratory subtype: psychopathology and challenge tests - an update

Panic disorder (PD) pathophysiology is very heterogeneous, and the discrimination of distinct subtypes could be very useful. A subtype based on respiratory symptoms is known to constitute a specific subgroup. However, evidence to support the respiratory subtype (RS) as a distinct subgroup of PD with a well-defined phenotype remains controversial. Studies have focused on characterization of the RS based on symptoms and response to CO2. In this line, we described clinical and biological aspects focused on symptomatology and CO2 challenge tests in PD RS. The main symptoms that characterize RS are dyspnea (shortness of breath) and a choking sensation. Moreover, patients with the RS tended to be more responsive to CO2 challenge tests, which triggered more panic attacks in this subgroup. Future studies should focus on discriminating respiratory-related clusters and exploring psychophysiological and neuroimaging outcomes in order to provide robust evidence to confirm RS as a distinct subtype of PD.

Mean Platelet Volume and Platelet Distribution Width Level in Patients with Panic Disorder

Background:

Changes in platelet indices have been reported in patients with panic disorder (PD). However, previous study findings are contradictory and inconclusive. The aim of this study was to evaluate and compare the platelet indices in patients with PD.

Materials and Methods:

Patients with PD (n = 123) and healthy controls (n = 133) were enrolled in this case control study. The platelet indices (mean platelet volume [MPV] and platelet distribution width [PDW]) along with red blood cell (RBC) indices (RBC count and red cell distribution width [RDW]) were compared between the two groups using the unpaired t-test.

Results:

Patients with PD had lower MPV (7.53 ± 0.93 fL vs. 8.91 ± 1.24 fL, P < 0.0001), higher PDW (16.96 ± 0.85 fL vs. 14.71 ± 2.07 fL, P < 0.0001), and higher platelet count (274.2 ± 80.66 × 10⁹ L⁻¹ vs. 243.1 ± 93.89 × 10⁹ L⁻¹, P < 0.005) than the healthy controls. Furthermore, there were significant differences between patients with PD and healthy controls in terms of their RBC count (4.32 ± 0.56 × 10¹² L⁻¹ vs. 4.08 ± 0.80 × 10¹² L⁻¹, P = 0.007) and RDW (16.48 ± 2.26 fL vs. 15.01 ± 2.25 fL, P < 0.0001).

Conclusion:

Patients with PD have increased PDW and RDW. The platelet and RBC indices may prove to be useful etiological and prognostic markers in patients with PD.

Effect of single doses of pindolol and d-fenfluramine on flumazenil-induced anxiety in panic disorder patients

The effects of the 5-HT_1A receptor blocker pindolol and the 5-HT releasing and uptake blocking agent d-fenfluramine, both used as indirect serotonin agonists, on flumazenil-induced acute anxiety reactions were studied in panic disorder patients to test the hypothesis that serotonin (5-HT) inhibits neural systems mediating panic attacks. Thirty never treated or drug free PD patients (16 females) aged 22-49 y (mean ± SD, 32.9 ± 8) received single doses of d-fenfluramine (n = 10; 30 mg, p.o.), pindolol (n = 10; 5 mg, p.o.), or placebo (n = 10) 90 and 45 min before a challenge test with flumazenil (1.5 mg, i.v., in 10 min), under double-blind conditions. Panic attacks occurred in 5 control subjects (placebo-flumazenil group), 5 subjects in the pindolol group and in 7 in the d-fenluramine pre-treated patients. Patients experiencing anxiety attacks following flumazenil reported higher increases in anxiety scores. Respiratory rate increases were not different between patients experiencing or not a panic attack. Despite sample size limitation, this study suggests that flumazenil induced anxiety reaction is not a good pharmacological model of panic attacks, considering the absence of serotonergic modulation of its effects.

Study of Sex Differences in Duloxetine Efficacy for Depression in Transgenic Mouse Models

Clinical evidences show sex differences in risk of developing depressive disorders as well as effect of antidepressants in depression treatment. However, whether such a sex-dependent risk of depression and efficacy of antidepressants is dependent on endogenous estrogen level remain elusive. The aim of this study is to explore the molecular mechanisms of sex differences in antidepressant duloxetine. In the present study, we used genetic knockout or overexpression estrogen-synthesizing enzyme aromatase (Ar) gene as models for endogenous estrogen deficiency and elevation endogenous estrogen, respectively, to examine the anti-depressive efficacy of duloxetine in males and females by force swimming test (FST). We also measured the sex-specific effect of duloxetine on dopamine and serotonin (5-HT) metabolisms in frontal cortex and hippocampus (HPC). Elevation of brain endogenous estrogen in male and female mice showed a reduction of immobility time in FST compared to control mice. Estrogen deficiency in females showed poor response to duloxetine treatment compared to sex-matched wildtype (WT) or aromatase transgenic mice. In contrast, male mice with estrogen deficiency showed same anti-depressive response to duloxetine treatments as aromatase transgenic mice. Our data showed that the sex different effect of endogenous estrogen on duloxetine-induced anti-depressive behavioral change is associated with brain region-specific changes of dopamine (DA) and 5-HT system. Endogenous estrogen exerts antidepressant effects in both males and females. Lacking of endogenous estrogen reduced antidepressive effect of duloxetine in females only. The endogenous estrogen level alters 5-HT system in female mainly, while both DA and 5-HT metabolisms were regulated by endogenous estrogen levels after duloxetine administration.

Candidate genes in panic disorder: meta-analyses of 23 common variants in major anxiogenic pathways

The utilization of molecular genetics approaches in examination of panic disorder (PD) has implicated several variants as potential susceptibility factors for panicogenesis. However, the identification of robust PD susceptibility genes has been complicated by phenotypic diversity, underpowered association studies and ancestry-specific effects. In the present study, we performed a succinct review of case-control association studies published prior to April 2015. Meta-analyses were performed for candidate gene variants examined in at least three studies using the Cochrane Mantel-Haenszel fixed-effect model. Secondary analyses were also performed to assess the influences of sex, agoraphobia co-morbidity and ancestry-specific effects on panicogenesis. Meta-analyses were performed on 23 variants in 20 PD candidate genes. Significant associations after correction for multiple testing were observed for three variants, TMEM132D rs7370927 (T allele: odds ratio (OR)=1.27, 95% confidence interval (CI): 1.15-1.40, P=2.49 × 10(-6)), rs11060369 (CC genotype: OR=0.65, 95% CI: 0.53-0.79, P=1.81 × 10(-5)) and COMT rs4680 (Val (G) allele: OR=1.27, 95% CI: 1.14-1.42, P=2.49 × 10(-5)) in studies with samples of European ancestry. Nominal associations that did not survive correction for multiple testing were observed for NPSR1 rs324891 (T allele: OR=1.22, 95% CI: 1.07-1.38, P=0.002), TPH1 rs1800532 (AA genotype: OR=1.46, 95% CI: 1.14-1.89, P=0.003) and HTR2A rs6313 (T allele: OR=1.19, 95% CI: 1.07-1.33, P=0.002) in studies with samples of European ancestry and for MAOA-uVNTR in female PD (low-active alleles: OR=1.21, 95% CI: 1.07-1.38, P=0.004). No significant associations were observed in the secondary analyses considering sex, agoraphobia co-morbidity and studies with samples of Asian ancestry. Although these findings highlight a few associations, PD likely involves genetic variation in a multitude of biological pathways that is diverse among populations. Future studies must incorporate larger sample sizes and genome-wide approaches to further quantify the observed genetic variation among populations and subphenotypes of PD.

5-Hydroxytryptamine 1A receptors in the dorsomedial hypothalamus connected to dorsal raphe nucleus inputs modulate defensive behaviours and mediate innate fear-induced antinociception

The dorsal raphe nucleus (DRN) is an important brainstem source of 5-hydroxytryptamine (5-HT), and 5-HT plays a key role in the regulation of panic attacks. The aim of the present study was to determine whether 5-HT1A receptor-containing neurons in the medial hypothalamus (MH) receive neural projections from DRN and to then determine the role of this neural substrate in defensive responses. The neurotracer biotinylated dextran amine (BDA) was iontophoretically microinjected into the DRN, and immunohistochemical approaches were then used to identify 5HT1A receptor-labelled neurons in the MH. Moreover, the effects of pre-treatment of the dorsomedial hypothalamus (DMH) with 8-OH-DPAT and WAY-100635, a 5-HT1A receptor agonist and antagonist, respectively, followed by local microinjections of bicuculline, a GABAA receptor antagonist, were investigated. We found that there are many projections from the DRN to the perifornical lateral hypothalamus (PeFLH) but also to DMH and ventromedial (VMH) nuclei, reaching 5HT1A receptor-labelled perikarya. DMH GABAA receptor blockade elicited defensive responses that were followed by antinociception. DMH treatment with 8-OH-DPAT decreased escape responses, which strongly suggests that the 5-HT1A receptor modulates the defensive responses. However, DMH treatment with WAY-100635 failed to alter bicuculline-induced defensive responses, suggesting that 5-HT exerts a phasic influence on 5-HT1A DMH neurons. The activation of the inhibitory 5-HT1A receptor had no effect on antinociception. However, blockade of the 5-HT1A receptor decreased fear-induced antinociception. The present data suggest that the ascending pathways from the DRN to the DMH modulate panic-like defensive behaviours and mediate antinociceptive phenomenon by recruiting 5-HT1A receptor in the MH.

Reactivity to 35% carbon dioxide in bulimia nervosa and panic disorder

The inhalation of 35% carbon dioxide (CO₂) induces panic and anxiety in people with panic disorder (PD) and in people with various other psychiatric disorders. The anxiogenic effect of CO₂ in people with eating disorders has received sparse attention despite the fact that PD and bulimia nervosa (BN) have several common psychological and neurobiological features. This study compared CO₂-reactivity across three groups of participants: females with BN, females with PD, and female controls without known risk factors for enhanced CO₂-reactivity (e.g., social anxiety disorder, first degree relatives with PD). Reactivity was measured by self-reported ratings of panic symptomatology and subjective anxiety, analyzed as both continuous variables (change from room-air to CO₂) and dichotomous variables (positive versus negative responses to CO₂). Analyses of each outcome measure demonstrated that CO₂-reactivity was similar across the BN and PD groups, and reactivity within each of these two groups was significantly stronger than that in the control group. This is the first study to demonstrate CO₂-hyperreactivity in individuals with BN, supporting the hypothesis that reactivity to this biological paradigm is not specific to PD. Further research would benefit from examining transdiagnostic mechanisms in CO₂-hyperreactivity, such as anxiety sensitivity, which may account for this study's results.

Lifestyle Behaviours Add to the Armoury of Treatment Options for Panic Disorder: An Evidence-Based Reasoning

This article presents an evidence-based reasoning, focusing on evidence of an Occupational Therapy input to lifestyle behaviour influences on panic disorder that also provides potentially broader application across other mental health problems (MHP). The article begins from the premise that we are all different. It then follows through a sequence of questions, examining incrementally how MHPs are experienced and classified. It analyses the impact of individual sensitivity at different levels of analysis, from genetic and epigenetic individuality, through neurotransmitter and body system sensitivity. Examples are given demonstrating the evidence base behind the logical sequence of investigation. The paper considers the evidence of how everyday routine lifestyle behaviour impacts on occupational function at all levels, and how these behaviours link to individual sensitivity to influence the level of exposure required to elicit symptomatic responses. Occupational Therapists can help patients by adequately assessing individual sensitivity, and through promoting understanding and a sense of control over their own symptoms. It concludes that present clinical guidelines should be expanded to incorporate knowledge of individual sensitivities to environmental exposures and lifestyle behaviours at an early stage.

Studying the neurobiology of human social interaction: Making the case for ecological validity

With this commentary we make the case for an increased focus on the ecological validity of the measures used to assess aspects of human social functioning. Impairments in social functioning are seen in many types of psychopathology, negatively affecting the lives of psychiatric patients and those around them. Yet the neurobiology underlying abnormal social interaction remains unclear. As an example of human social neuroscience research with relevance to biological psychiatry and clinical psychopharmacology, this commentary discusses published experimental studies involving manipulation of the human brain serotonin system that included assessments of social behavior. To date, these studies have mostly been laboratory-based and included computer tasks, observations by others, or single-administration self-report measures. Most laboratory measures used so far inform about the role of serotonin in aspects of social interaction, but the relevance for real-life interaction is often unclear. Few studies have used naturalistic assessments in real life. We suggest several laboratory methods with high ecological validity as well as ecological momentary assessment, which involves intensive repeated measures in naturalistic settings. In sum, this commentary intends to stimulate experimental research on the neurobiology of human social interaction as it occurs in real life.

Arousal and the attentional network in panic disorder

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

The potential role of atypical antipsychotics in the treatment of panic disorder

OBJECTIVE

Many studies have investigated the efficacy and tolerability of alternative pharmacotherapy for panic disorder. This study aims to provide a comprehensive review of the existing literature regarding the efficacy and tolerability of atypical antipsychotics for panic disorder.

METHODS

We searched for relevant published articles using Medline, the Cochrane database, and EMBASE on 19 June 2013. Prospective studies that examined the efficacy and tolerability of atypical antipsychotics in the treatment of primary panic disorder or comorbid panic disorder (or symptoms) in other psychiatric disorders were included in this review.

RESULTS

Seven prospective studies were included in this review. Among these, four were open-label studies for refractory panic disorder. Two of the seven included studies were randomized controlled trials among patients with panic symptoms comorbid with bipolar disorder. The remaining study was a randomized controlled trial for panic disorder or panic attack comorbid with major depression. Except one negative risperidone study, the reviewed studies showed the favorable efficacy results of atypical antipsychotics.

CONCLUSIONS

Although the majority of the evidence regarding the efficacy of atypical antipsychotics in the treatment of panic disorder comes from small, open-label studies, this review suggests the potential role of atypical antipsychotics in treating panic disorder.

Decreased mean platelet volume in panic disorder

AIM

The relationship between psychological stress and platelet activation has been widely studied. It is well known that platelets may reflect certain biochemical changes that occur in the brain when different mental conditions occur. Platelet 5-hydroxytryptamine (5-HT) is also extensively studied in psychiatry. The mean platelet volume (MPV), the accurate measure of platelet size, has been considered a marker and determinant of platelet function. The aim of the present study was to search for any probable difference in the MPV of subjects with panic disorder (PD).

METHODS

A total of 37 drug-free subjects, aged 18 to 65 years, diagnosed with PD, with or without agoraphobia, according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth edition (DSM-IV) criteria and 45 healthy control subjects were included in the study. Platelet count and MPV were measured and recorded for each subject.

RESULTS

There were no statistically significant differences between groups in terms of female/male ratio, age, or body mass index between the PD group and control group (P=0.91, P=0.82, and P=0.93, respectively). The MPV was found to be significantly lower in the PD group compared with the control group (8.8±0.9 fL vs 9.2±0.8 fL; P=0.02). All the participants had MPV values in the standard range of 6.9-10.8 fL.

CONCLUSION

We concluded that abnormalities of the 5-HT1A receptor function in the central nervous system of subjects with a diagnosis of PD are also mirrored in as an alteration in platelet activity. Measurements of platelet activity may be used as a tool for neuropsychiatric and psychopharmacological research and for studying how certain mental diseases and medications affect the central nervous system.

The effect of 6-week treatment with escitalopram on CCK-4 challenge: a placebo-controlled study in CCK-4-sensitive healthy volunteers

Cholecystokinin-tetrapeptide (CCK-4)-induced panic attacks are reportedly attenuated by effective treatment with antipanic antidepressants in patients with panic disorder, but in healthy volunteers such effects are not well studied. The aim of this study was to assess the effect of 6-week treatment with an SSRI escitalopram on CCK-4-induced symptoms in healthy volunteers, who previously responded with a panic attack to CCK-4 challenge. A total of 18 healthy subjects (10 males and eight females, mean age 22.5 ± 5.8) received a 6-week treatment with escitalopram (10 mg/day) and placebo followed by CCK-4 challenge (50 μg) in a double-blind crossover design. The panic rate was 67% after treatment with escitalopram and 56% after treatment with placebo (p = 0.7). Thus, the results showed a significant reduction in CCK-4-induced panic rates without significant differences between escitalopram and placebo conditions. There were no significant effects of either treatment on any other variable of anxiety or cardiovascular indices. Secondary analysis showed no effect of gender or 5-HTTLPR polymorphism on response to CCK-4 challenge. This study demonstrated that in contrast to the findings in patients with panic disorder, in CCK-4-sensitive healthy volunteers the treatment with an antipanic SSRI did not cause a reduction of CCK-4-induced panic attacks beyond the effect of placebo. The mechanisms behind this discrepancy and the reasons of the decrease in sensitivity to CCK-4 challenge on repeated administration remain to be clarified in future studies.

Antidepressant drugs

Therapeutic Reviews aim to provide essential independent information for health professionals about drugs used in palliative and hospice care. Additional content is available on www.palliativedrugs.com. Country-specific books (Hospice and Palliative Care Formulary USA, and Palliative Care Formulary, British and Canadian editions) are also available and can be ordered from www.palliativedrugs.com. The series editors welcome feedback on the articles (hq@palliativedrugs.com).

The anxiogenic-like effects of dehydration in a semi-desert rodent Meriones shawi indicating the possible involvement of the serotoninergic system

Dehydration is a powerful stimulus causing disequilibrium in homeostasis of water and electrolytes resulting from depletion in total body water. Most studies have focused on domestic and laboratory animals; however, the study of desert animals allows improved understanding about water balance and resistance to dehydration and associated behavioral changes, including those related to mood disorders. Meriones shawi (Shaw's Jird) is a desert rodent characterized by its resistance to long periods of thirst that can extend for several months. In the present study, M. shawi were subjected to water deprivation for 1 and 3 months. We used 5-HT immunohistochemistry to evaluate the effects of prolonged dehydration on the serotoninergic system in both dorsal and median raphe nuclei (DRN, MRN), which are the main sources of 5-HT input to several brain areas. In addition, a dark/light box was used to evaluate the anxiolytic-like or anxiogenic-like effects of dehydration on M. shawi. The results showed a reduction in the 5-HT immunolabelling in both DRN and MRN following 1 and 3 months of dehydration. This diminution of serotonin immunoreactivity was accompanied by noticeable changes in anxiety behavior of Meriones, with animals spending more time in the light box, suggesting anxiogenic-like effects caused by dehydration. Overall, the results indicate that dehydration is able to reduce serotoninergic neurotransmission, which might be involved in generating anxiety behavior in this desert animal.

Elevated tph2 mRNA expression in a rat model of chronic anxiety

BACKGROUND

Allelic variations in TPH2, the gene encoding tryptophan hydroxylase 2, the rate-limiting enzyme for brain serotonin (5-HT) biosynthesis, may be genetic predictors of panic disorder and panic responses to panicogenic challenges in healthy volunteers. To test the hypothesis that tph2 mRNA is altered in chronic anxiety states, we measured tph2 expression in an established rat model of panic disorder.

METHODS

We implanted 16 adult, male rats with bilateral guide cannulae and then primed them with daily injections of the corticotropin-releasing factor (CRF) receptor agonist, urocortin 1 (UCN1, 6 fmoles/100 nl per side, n = 8) or vehicle (n = 8) into the basolateral amygdaloid complex (BL) for 5 consecutive days. Anxiety-like behavior was assessed, 24 hr prior to and 48 hr following priming, in the social interaction (SI) test. A third group (n = 7) served as undisturbed home cage controls. All rats were killed 3 days after the last intra-BL injection to analyze tph2 and slc6a4 (gene encoding the serotonin transporter, SERT) mRNA expression in the dorsal raphe nucleus (DR), the main source of serotonergic projections to anxiety-related brain regions, using in situ hybridization histochemistry.

RESULTS

UCN1 priming increased anxiety-related behavior in the SI test compared to vehicle-injected controls and elevated tph2, but not slc6a4, mRNA expression in DR subregions, including the ventrolateral DR/ventrolateral periaqueductal gray (DRVL/VLPAG), a subregion previously implicated in control of panic-related physiologic responses. Tph2 mRNA expression in the DRVL/VLPAG was correlated with increased anxiety-related behavior.

CONCLUSION

Our data support the hypothesis that chronic anxiety states are associated with dysregulated tph2 expression.

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).

Milnacipran in panic disorder with agoraphobia and major depressive disorder: a case report

A 51-year-old woman had panic disorder with agoraphobia and major depressive disorder sequentially. The aforementioned symptoms subsided significantly after treatment with milnacipran, 125 mg, administered daily for 2 months. However, panic attacks with agoraphobia were noted frequently when she tapered down milnacipran to 50 mg daily. She consequently experienced depression that gradually increased in degree, with poor energy, poor sleep, thoughts of helplessness, and ideas of death. After administration of a daily dose of 125 mg of milnacipran for 1 month, her panic attacks with agoraphobia and depressed mood were again alleviated. The present report shows significant effects of milnacipran on the comorbidity of panic disorder with agoraphobia and major depressive disorder.

The diagnostic value of clinical EEG in detecting abnormal synchronicity in panic disorder

Electroencephalographic (EEG) findings repeatedly reported abnormal synchronous or even epileptiform discharges in panic disorder. Although less frequently occurring in patients with panic disorder, these deviant EEG features during panic attacks were also observed in intracranial EEG. For this purpose, our article reviews the consideration of abnormal synchronous neuronal activity in different neurocircuits, particularly limbic, as a suggested condition of panic attacks. Therapeutic approaches of anticonvulsants have shown reductions of symptoms and frequency of attacks in numerous patients suffering from panic disorder, supporting the presumption of underlying abnormal synchronous neuronal activity. Thus, scalp EEG recordings are still recommended for discovering indications of abnormal synchronous neuronal activity in panic patients.

Gender differences in brain serotonin transporter availability in panic disorder

The role of the serotonin (5-HT) system in the neurobiology and treatment of panic disorder (PD) remains unproven. Previously we detected lower brain 5-HT transporter (SERT) availability in PD, but the findings were preliminary and mainly limited to female patients. The aim of this study was to assess non-displaceable brain SERT binding potential (BP (ND)) in male and female patients with PD. The SERT BP (ND) was measured in groups of patients with PD (five males and six females) and matched healthy control subjects (12 males and 12 females) using positron emission tomography (PET) and [¹¹C]MADAM tracer. SERT BP (ND) were significantly higher in 13 of 20 studied brain regions, including several cortical and raphe areas, but lower in the hippocampus in males with PD as compared with healthy males. No significant differences in SERT BP (ND) were observed between female patients and controls. The results suggest gender-dependent regional differences in brain SERT availability and converge with previous PET findings of reduced 5-HT(1A) receptor binding in similar brain areas in PD. Distinctive functioning of the 5-HT system in males and females may underlie certain gender-dependent differences in expressions of PD.

Ictal panic and interictal panic attacks: diagnostic and therapeutic principles

Ictal and postictal panic and interictal and primary panic attacks share common symptoms but differ with respect to duration and association with other symptoms. A careful history is often sufficient to distinguish these events. When necessary, electroencephalography and neuroimaging studies, estimation of prolactin levels can be a helpful tool in establishing an accurate diagnosis.

Involvement of dorsal raphe nucleus and dorsal periaqueductal gray 5-HT receptors in the modulation of mouse defensive behaviors

Previous findings point to the involvement of the dorsal raphe nucleus (DRN) and dorsal periaqueductal gray (dPAG) serotonergic receptors in the mediation of defensive responses that are associated with specific subtypes of anxiety disorders. These studies have mostly been conducted with rats tested in the elevated T-maze, an experimental model of anxiety that was developed to allow the measurement, in the same animal, of two behaviors mentioned: inhibitory avoidance and one-way escape. Such behavioral responses have been respectively related to generalized anxiety disorder (GAD) and panic disorder (PD). In order to assess the generality of these findings, in the current study we investigated the effects of the injection of 5-HT-related drugs into the DRN and dPAG of another rodent species, mouse, on the mouse defense test battery (MDTB), a test of a range of defensive behaviors to an unconditioned threat, a predator. Male CD-1 mice were tested in the MDTB after intra-DRN administration of the 5-HT(1A) receptor antagonist WAY-100635 or after intra-dPAG injection of two serotonergic agonists, the 5-HT(1A) receptor agonist 8-OH-DPAT and the 5-HT(2A/2C) receptor agonist DOI. Intra-DRN injection of WAY-100635 did not change behavioral responses of mice confronted with a rat in the MDTB. In the dPAG, both 8-OH-DPAT and DOI consistently impaired mouse escape behavior assessed in the MDTB. Intra-dPAG infusion of 8-OH-DPAT also decreased measures of mouse risk assessment in the rat exposure test. In conclusion, the current findings are in partial agreement with previous results obtained with rats tested in the elevated T-maze. Although there is a high level of similarity between the behavioral effects obtained in rats (elevated T-maze) and mice (MDTB and RET) with the infusion of 5-HT agonists into the dPAG, the same is not true regarding the effects of blockade of DRN 5-HT(1A) receptors in these rodent species. These data suggest that there may be differences between mice and rats regarding the involvement of the DRN in the mediation of defensive behaviors.

Human microRNAs miR-22, miR-138-2, miR-148a, and miR-488 are associated with panic disorder and regulate several anxiety candidate genes and related pathways

BACKGROUND

The involvement of microRNAs (miRNAs) in neuronal differentiation and synaptic plasticity suggests a role for miRNAs in psychiatric disorders; association analyses and functional approaches were used to evaluate the implication of miRNAs in the susceptibility for panic disorder.

METHODS

Case-control studies for 712 single-nucleotide polymorphisms (SNPs) tagging 325 human miRNA regions were performed in 203 Spanish patients with panic disorder and 341 control subjects. A sample of 321 anxiety patients and 642 control subjects from Finland and 102 panic disorder patients and 829 control subjects from Estonia was used as a replica. Reporter-gene assays and miRNA overexpression experiments in neuroblastoma cells were used to functionally evaluate the spectrum of genes regulated by the associated miRNAs.

RESULTS

Two SNPs associated with panic disorder: rs6502892 tagging miR-22 (p < .0002), and rs11763020 tagging miR-339 (p < .00008). Other SNPs tagging miR-138-2, miR-488, miR-491, and miR-148a regions associated with different panic disorder phenotypes. Replication in the north-European sample supported several of these associations, although they did not pass correction for multiple testing. Functional studies revealed that miR-138-2, miR-148a, and miR-488 repress (30%-60%) several candidate genes for panic disorder--GABRA6, CCKBR and POMC, respectively--and that miR-22 regulates four other candidate genes: BDNF, HTR2C, MAOA, and RGS2. Transcriptome analysis of neuroblastoma cells transfected with miR-22 and miR-488 showed altered expression of a subset of predicted target genes for these miRNAs and of genes that might be affecting physiological pathways related to anxiety.

CONCLUSIONS

This work represents the first report of a possible implication of miRNAs in the etiology of panic disorder.

Effects of tryptophan depletion and tryptophan loading on the affective response to high-dose CO2 challenge in healthy volunteers

RATIONALE

It has been reported that in panic disorder (PD), tryptophan depletion enhances the vulnerability to experimentally induced panic, while the administration of serotonin precursors blunts the response to challenges.

OBJECTIVES

Using a high-dose carbon dioxide (CO(2)) challenge, we aimed to investigate the effects of acute tryptophan depletion (ATD) and acute tryptophan loading (ATL) on CO(2)-induced panic response in healthy volunteers.

METHODS

Eighteen healthy volunteers participated in a randomized, double-blind placebo-controlled study. Each subject received ATD, ATL, and a balanced condition (BAL) in separate days, and a double-breath 35% CO(2) inhalation 4.5 h after treatment. Tryptophan (Trp) manipulations were obtained adding 0 g (ATD), 1.21 g (BAL), and 5.15 g (ATL) of l-tryptophan to a protein mixture lacking Trp. Assessments consisted of a visual analogue scale for affect (VAAS) and panic symptom list. A separate analysis on a sample of 55 subjects with a separate-group design has also been performed to study the relationship between plasma amino acid levels and subjective response to CO(2).

RESULTS

CO(2)-induced subjective distress and breathlessness were significantly lower after ATD compared to BAL and ATL (p < 0.05). In the separate-group analysis, ΔVAAS scores were positively correlated to the ratio Trp:ΣLNAA after treatment (r = 0.39; p < 0.05).

CONCLUSIONS

The present results are in line with preclinical data indicating a role for the serotonergic system in promoting the aversive respiratory sensations to hypercapnic stimuli (Richerson, Nat Rev Neurosci 5(6):449-461, 2004). The differences observed in our study, compared to previous findings in PD patients, might depend on an altered serotonergic modulatory function in patients compared to healthy subjects.

Genetic moderation of CO2-induced fear by 5-HTTLPR genotype

Inhalation of an increased concentration of carbon dioxide (CO(2)) has been shown to induce a state of negative affect in healthy subjects that is closely related to the clinical phenomenon of panic. It has been suggested that the vulnerability to CO(2) is moderated by differences in serotonin (5-HT) activity, caused by a functional polymorphism in the promoter region of the 5-HT transporter (5-HTTLPR) gene. Our aim was to examine the relationship between bi- and tri-allelic 5-HTTLPR genotype and the affective response to different dosages of inhaled CO(2) in healthy volunteers. Ninety-six subjects performed a double inhalation of four mixtures containing, respectively, 0%, 9%, 17.5% and 35% CO(2), following a double-blind, cross-over, randomized design. Affective responses were measured with a visual analogue scale for fear and the Panic Symptom List. 5-HTTLPR genotype was expressed as LL, SL and SS. Subjects with the SL and SS genotype reported less fear than LL subjects. A significant interaction effect was found between genotype and CO(2) dosage: the SS genotype showed lower fear scores than the LL genotype, particularly in the 17.5% CO(2) dose condition. The present study suggests that the dose-dependent fear reaction to CO(2) is moderated by a polymorphism in the 5-HT transporter gene, particularly at intermediate CO(2) dosages. It also underscores the usefulness of the introduction of an intermediate phenotype related to panic to reveal an underlying genetic vulnerability otherwise staying elusive. These results are in line with current theories on the role of 5-HT in both panic and respiration.

Which patient will feel down, which will be happy? The need to study the genetic disposition of emotional states

PURPOSE

In quality-of-life (QL) research, the genetic susceptibility of negative and positive emotions is frequently ignored, taken for granted, or treated as noise. The objectives are to describe: (1) the major findings of studies addressing the heritable and environmental causes of variation in negative and positive emotional states and (2) the major biological pathways of and genetic variants involved in these emotional states.

METHODS

Literature overview.

RESULTS

The heritability estimates for anxiety and depression are 30-40%. Related traits as neuroticism and loneliness are also highly heritable. The hypothalamo-pituitary-adrenal axis is the 'final common pathway' for most depressive symptoms. The many findings of investigated genes are promising but not definitive. Heritability estimates of positive emotional states range between 40 and 50%. Life satisfaction and mental health share common genetic factors with optimism and self-esteem. The prefrontal cortex is a candidate brain area for positive emotional states. Biological and genetic research into positive emotional states is scarce.

CONCLUSION

Genetically informative studies may provide insights into a wide variety of complex questions that traditional QL studies cannot deliver. This insight in turn will help us to design more effective supportive programs that could moderate the outcomes of genetically based predispositions.

Phylogenetic analysis and evolution of aromatic amino acid hydroxylase

A study was performed to investigate the phylogenetic relationship among AAAH members and to statistically evaluate sequence conservation and functional divergence. In total, 161 genes were identified from 103 species. Phylogenetic analysis showed that well-conserved subfamilies exist. Exon-intron structure analysis showed that the gene structures of AAAH were highly conserved across some different lineage species, while some species-specific introns were also found. The dynamic distribution of ACT domain suggested one gene fusion event has occurred in eukaryota. Significant functional divergence was found between some subgroups. Analysis of the site-specific profiles revealed critical amino acid residues for functional divergence. This study highlights the molecular evolution of this family and may provide a starting point for further experimental verifications.

Early response to selective serotonin reuptake inhibitors in panic disorder is associated with a functional 5-HT1A receptor gene polymorphism

BACKGROUND

Panic disorder is a common and disabling condition which can be treated with selective serotonin reuptake inhibitors (SSRIs). Although many subjects respond well to such treatment, there is substantial inter-individual variation implicating genetic factors.

METHODS

102 patients with a diagnosis of panic disorder receiving sertraline or paroxetine took part in study. Hospital Anxiety and Depression Scale score, CGI and panic attack frequency (per month) were assessed before and after 6 weeks of SSRI treatment with 1 week of titration period. All patients were genotyped for the -1019C/G 5-HT1A receptor and ins/del 5-HT transporter polymorphisms.

RESULTS

The 5-HT1A receptor -1019C/G polymorphism was strongly associated with response to treatment, in which 20 subjects with the GG genotype showed minimal changes in panic attack frequency with a relative risk of no response of 4.73. This association was also found with each drug independently. However, no association of the ins/del 5-HT transporter polymorphism with treatment response was observed.

LIMITATIONS

Larger numbers of subjects and longer period of SSRI treatment would confirm and strengthen these preliminary findings.

CONCLUSION

These results indicate the importance of a 5-HT1A receptor gene polymorphism in the response to SSRI treatment of panic disorder.

Association Study between 5-HT1A Receptor Gene C(-1019)G Polymorphism and Panic Disorder in a Korean Population

OBJECTIVE

Serotonergic dysfunction is quite evident in panic disorder. We investigated whether the C(-1019)G polymorphism of 5-HT1A receptor gene may play a role in the pathogenesis of panic disorder in a Korean population.

METHODS

The 5-HT1A receptor genotype for the single nucleotide polymorphism (SNP) C(-1019)G was analyzed in 94 patients and 111 healthy controls. The severity of the patients' symptoms was examined using the Spielberger State-Trait Anxiety Inventory (STAI), Panic Disorder Severity Scale (PDSS), Anxiety sensitivity index (ASI), Acute Panic Inventory (API) and Hamilton's Rating Scale for Anxiety (HAM-A).

RESULTS

The distribution of the genotypes of the C/G polymorphism did not differ significantly from those predicted by Hardy-Weinberg equilibrium in patients as well as the controls. No association between the C(-1019)G polymorphism and panic disorder was detected in either the allele frequency or genotype distribution. There was no significant association with genotype distribution in the panic disorder with agoraphobia. However, there was a significant difference of symptom severity between C/C, C/G, and G/G genotype or between C and G allele in panic disorder patients without agoraphobia. PDSS scores were significantly higher in subjects with the G/G genotype or with G allele in patients without agoraphobia, not in total patients or patients with agoraphobia.

CONCLUSION

Although there were no significant differences in the genotype and allele distributions, we found a significant association between panic symptom severity and the serotonin 1A receptor gene. This result suggests that the serotonin 1A receptor and serotonin may play a role in the pathogenesis of panic disorder.

Platelet serotonin transporter function after short-term paroxetine treatment in patients with panic disorder

Dysfunctions in serotonin neurotransmission have been implicated in some psychiatric disorders, and in particular, altered serotonin transporter function has been noted in panic disorder. In this study, the authors compared platelet [(3)H]serotonin uptake parameters, including maximum velocities (V(max)) and affinity constants (K(m)), in patients with panic disorder not undergoing treatment (n=21) and in healthy subjects (n=20). V(max) and K(m) values were re-examined after 12 weeks of paroxetine treatment. Values of V(max) and K(m) were lower in panic disorder patients at baseline than in healthy subjects. After treatment, K(m) normalized in panic patients, whereas V(max) did not change. A significant inverse correlation was found between increased K(m) and changes in anxiety levels. These results support a hypothesis of serotonergic transporter abnormalities in panic disorder, and suggest that increased K(m) values of platelet serotonin transporters parallel clinical improvement after short-term pharmacotherapy in panic disorder.

Platelet serotonin transporter function and heart rate variability in patients with panic disorder

Many studies showed abnormal serotonin transporter (5-HTT) function and heart rate variability (HRV) in panic disorder patients. The present study investigated the relationship between HRV power spectral analysis findings and platelet serotonin uptake in panic disorder patients. Short-term HRV over 5 min and platelet serotonin transporter uptake parameters (V(max) and K(m)) were measured both in 45 patients with panic disorder and in 30 age-matched normal healthy control subjects. Low frequency power (LF) normalized unit (nu) and LF/high frequency power (HF) were significantly higher, whereas HF and HF nu were lower in the patient group than in the control group. V(max) and K(m) were all significantly lower (i.e., reflects decreased 5-HTT function) in patients with panic disorder than in normal controls. In the patient group, K(m) was negatively correlated with LF/HF and LF nu whereas no such correlations between them were found in the control group. By multivariate analysis based on multiple hierarchical linear regression, a low K(m) independently predicted an increased LF nu even after controlling for age, sex, and body mass index in the patient group. These results suggest that impaired 5-HTT function is closely related to dysregulation of autonomic nervous system in panic disorder.

Association of a polyadenylation polymorphism in the serotonin transporter and panic disorder

BACKGROUND

Genetic markers in the serotonin transporter are associated with panic disorder (PD). The associated polymorphisms do not include the serotonin transporter-linked polymorphic region and display no obvious functional attributes. A common polymorphism (rs3813034) occurs in one of the two reported polyadenylation signals for the serotonin transporter and is in linkage disequilibrium with the PD-associated markers. If functional, rs3813034 might be the risk factor that explains the association of the serotonin transporter and PD.

METHODS

Quantitative polymerase chain reaction on human brain samples (n = 65) and lymphoblast cultures (n = 71) was used to test rs3813034 for effects on expression of the polyadenylation forms of the serotonin transporter. rs3813034 was also tested for association in a sample of PD cases (n = 307) and a control sample (n = 542) that has similar population structure.

RESULTS

The balance of the two polyadenylation forms of the serotonin transporter is associated with rs3813034 in brain (p < .001) and lymphoblasts (p < .001). The balance of the polyadenylation forms is also associated with gender in brain only (p < .05). Association testing of rs3813034 in PD identified a significant association (p = .0068) with a relative risk of 1.56 and 1.81 for the heterozygous and homozygous variant genotypes, respectively.

CONCLUSIONS

rs3813034 is a functional polymorphism in the serotonin transporter that alters the balance of the two polyadenylation forms of the serotonin transporter. rs3813034 is a putative risk factor for PD and other behavioral disorders that involve dysregulation of serotonergic neurotransmission.

Panic disorder is associated with the serotonin transporter gene (SLC6A4) but not the promoter region (5-HTTLPR)

Panic disorder (PD) and social anxiety disorder (SAD) are moderately heritable anxiety disorders. We analyzed five genes, derived from pharmacological or translational mouse models, in a new case-control study of PD and SAD in European Americans: (1) the serotonin transporter (SLC6A4), (2) the serotonin receptor 1A, (3) catechol-O-methyltransferase, (4) a regulator of g-protein signaling and (5) the gastrin-releasing peptide receptor. Cases were interviewed using the schedule for affective disorders and schizophrenia and were required to have a probable or definite lifetime diagnosis of PD (N=179), SAD (161) or both (140), with first onset by age 31 and a family history of anxiety. Final diagnoses were determined using the best estimate procedure, blind to genotyping data. Controls were obtained from the National Institute of Mental Health Human Genetics Initiative; only subjects above 25 years of age who screened negative for all psychiatric symptoms were included (N=470). A total of 45 single nucleotide polymorphisms were successfully genotyped over the five selected genes using Applied Biosystems SNPlex protocol. SLC6A4 provided strong and consistent evidence of association with the PD and PD+SAD groups, with the most significant association in both groups being at rs140701 (chi(2)=10.72, P=0.001 with PD and chi(2)=8.59, P=0.003 in the PD+SAD group). This association remained significant after multiple test correction. Those carrying at least one copy of the haplotype A-A-G constructed from rs3794808, rs140701 and rs4583306 have 1.7 times the odds of PD than those without the haplotype (95% confidence interval: 1.2-2.3). The SAD only group did not provide evidence of association, suggesting a PD-driven association. The findings remained after adjustment for age and sex, and there was no evidence that the association was due to population stratification. The promoter region of the gene, 5-HTTLPR, did not provide any evidence of association, regardless of whether analyzed as a triallelic or biallelic locus, nor did any of the other four candidate genes tested. Our findings suggest that the serotonin transporter gene may play a role in PD; however, the findings require replication. Future studies should attend to the entire genetic region rather than the promoter.

Dopamine transporter binding in females with panic disorder may vary with clinical status

BACKGROUND

To date the involvement of dopamine system in neurobiology of panic disorder (PD) has been not investigated by imaging studies in humans. In this study, we evaluated the binding potential of dopamine transporter (DAT) in striatum of patients with PD.

METHODS

Subjects comprised seven female patients with current PD, seven female PD patients in remission and seven female healthy controls, matched by age. Striatal DAT binding was evaluated using single-photon emission computed tomography and [(123)I]nor-beta-CIT tracer.

RESULTS

Significantly higher DAT binding in striatum was detected in remitted PD females as compared with both currently ill PD and control females. The females with current PD demonstrated non-significant lowering in striatal DAT binding as compared with healthy controls. The correlation analysis in total sample of female patients showed significant and inverse relationship between striatal DAT binding characteristics and severity of panic symptoms.

CONCLUSIONS

This is first report showing that DAT binding in striatum may depend on the clinical status in females with PD. Our data suggest that increased level of DAT may contribute to stability of remission; however, the exact involvement of dopamine system in PD pathogenesis requires further investigations. The preliminary results of current study should be confirmed by other independent studies and should also be extended to include male patients.