Dopamine and social anxiety disorder

Genetics of social anxiety disorder: a systematic review

Social anxiety disorder (SAD) is a common psychiatric disorder, often associated with avoidant temperament. Research studies have implicated a strong genetic architecture of SAD. We have conducted a systematic review on the genetics of SAD and yielded 66 articles. In general, prior research studies have focused on the serotonin transporter, oxytocin receptor, brain-derived neurotrophic factor and catechol-O-methyltransferase genes. Mixed and inconsistent results have been reported. Additional approaches and phenotypes have also been investigated, including pharmacogenetics of treatment response, imaging genetics and gene-environment interactions. Future directions warrant further international collaborative efforts, deep-phenotyping of clinical characteristics including consistent and reliable measurement-based symptom severity, and larger sample sizes to ensure sufficient power for stratification due to the heterogeneity of this chronic and often debilitating condition.

Genetic Deletion of Soluble Epoxide Hydroxylase Causes Anxiety-Like Behaviors in Mice

Soluble epoxide hydrolase (sEH), an enzyme with COOH-terminal hydrolase and NH₂-terminal lipid phosphatase activities, is expressed in regions of the brain such as the cortex, white matter, hippocampus, substantia nigra, and striatum. sEH is involved in the regulation of cerebrovascular and neuronal function upon pathological insults. However, the physiological significance of sEH and its underlying mechanism in modulating brain function are not fully understood. In this study, we investigated the role of sEH in anxiety and potential underlying mechanisms in mice. Western blot for protein phosphorylation and expression was performed. Immunohistochemical analyses and Nissl and Golgi staining were performed for histological examination. Mouse behaviors were evaluated by open field activity, elevated plus maze, classical fear conditioning, social preference test, and Morris water maze. Our results demonstrated that the expression of sEH was upregulated during postnatal development in wild-type (WT) mice. Genetic deletion of sEH (sEH^-/-) in mice resulted in anxiety-like behavior and disrupted social preference. Increased olfactory bulb (OB) size and altered integrity of neurites were observed in sEH^-/- mice. In addition, ablation of sEH in mice decreased protein expression of tyrosine hydroxylase and reduced dopamine production in the brain. Moreover, the level of phosphorylated calmodulin kinase II (CaMKII) and glycogen synthase kinase 3 α/β (GSK3α/β) was higher in sEH^-/- mice than in WT mice. Collectively, these findings suggest that sEH is a key player in neurite outgrowth of neurons, OB development in the brain, and the development of anxiety-like behavior, by regulating the CaMKII-GSK3α/β signaling pathway.

Increased dopamine transporter density in Parkinson's disease patients with Social Anxiety Disorder

Social Anxiety Disorder (SAD) is more common among PD patients than in the general population. This association may be explained by psychosocial mechanisms but it is also possible that neurobiological mechanism underlying PD can predispose to SAD. The aim of this study was to investigate a possible dopaminergic mechanism involved in PD patients with SAD, by correlating striatal dopamine transporter binding potential (DAT-BP) with intensity of social anxiety symptoms in PD patients using SPECT with TRODAT-1 as the radiopharmaceutical. Eleven PD patients with generalized SAD and 21 PD patients without SAD were included in this study; groups were matched for age, gender, disease duration and disease severity. SAD diagnosis was determined according to DSM IV criteria assessed with SCID-I and social anxiety symptom severity with the Brief Social Phobia Scale (BSPS). Demographic and clinical data were also collected. DAT-BP was significantly correlated to scores on BSPS for right putamen (r=0.37, p=0.04), left putamen (r=0.43, p=0.02) and left caudate (r=0.39, p=0.03). No significant correlation was found for the right caudate (r=0.23, p=0.21). This finding may reinforce the hypothesis that dopaminergic dysfunction might be implicated in the pathogenesis of social anxiety in PD.

The effects of single dose anxiolytic medication on the CO2 models of anxiety: differentiation of subjective and objective measures

This was a double blind, placebo-controlled, 4-way cross-over study in 12 healthy volunteer subjects of the acute effects of three drugs each of which are used in the clinic to treat some forms of anxiety: propranolol 40 mg, hydroxyzine 25 mg, flupentixol 0.5 mg and placebo. Each test session consisted of inhalation of air for 20 min, 10-min rest, inhalation of CO2 7.5% for 20 min, 10-min rest, followed by a single vital capacity inhalation of 35% CO2. The CO2 7.5% was administered at peak drug effect. Subjective effects were measured using Visual Analogue Scales (VAS), the Panic Symptom Inventory and the Generalised Anxiety Disorder Assessment inventory. Twelve subjects participated (eight men), with a mean age of 25.9 years. The expected subjective effects of CO2 were seen and these were significantly different from effects of peak air. However, there were no statistically significant differences between the drugs or between drugs and placebo, indeed there was a trend for some VAS anxiety scores to be higher than placebo in the drug groups. There were some significant differences in cardiovascular responses to CO2, with propranolol significantly decreasing heart rate and flupentixol increasing blood pressure when compared with placebo. The lack of subjective anxiolytic actions of the three drugs contrasts with our previous findings with acute benzodiazepines and chronic selective serotonin reuptake inhibitor administration. It may be that prolonged treatment with these agents would be required to show anxiolytic effects, although it may also be that their efficacy is insufficient to be demonstrated in this model. The lack of anxiolytic actions of propranolol, despite a significant reduction in heart rate, is a further support for a central action of CO2 to produce anxiety.

Resistência ao tratamento nos transtornos de ansiedade: fobia social, transtorno de ansiedade generalizada e transtorno do pânico

OBJETIVOS: Os transtornos de ansiedade são condições psiquiátricas prevalentes que determinam importante prejuízo funcional, piora na qualidade de vida do indivíduo e um enorme custo social. Embora diversas medicações eficazes para os transtornos de ansiedade encontrem-se disponíveis, um número significativo de pacientes não responde adequadamente ao tratamento e muitos permanecem com sintomas residuais clinicamente significativos. O objetivo deste estudo é rever aspectos relacionados à resistência ao tratamento e estratégias farmacológicas no manejo dos transtornos de ansiedade resistentes ao tratamento. MÉTODO: Revisão narrativa. RESULTADOS: São discutidos os diversos aspectos conceituais relacionados à resistência ao tratamento, os possíveis preditores de resistência e, finalmente, algumas estratégias a serem utilizadas no manejo dos transtornos de ansiedade (incluindo transtorno de ansiedade social, transtorno de ansiedade generalizada e transtorno do pânico) que não respondem às abordagens terapêuticas convencionais. CONCLUSÃO: A resistência ao tratamento ainda é um desafio para a prática clínica que começa em conceitos não operacionalizados de resposta e resistência e termina na escassez de estudos controlados sobre estratégias de tratamento nesse último cenário clínico.