Effects of citalopram on worry and brain activation in patients with generalized anxiety disorder

An insular view of anxiety

We propose a general hypothesis that integrates affective and cognitive processing with neuroanatomy to explain anxiety pronenes. The premise is that individuals who are prone to anxiety show an altered interoceptive prediction signal, i.e., manifest augmented detection of the difference between the observed and expected body state. As a consequence, the increased prediction signal of a prospective aversive body state triggers an increase in anxious affect, worrisome thoughts and other avoidance behaviors. The anterior insula is proposed to play a key role in this process. Further testing of this model--which should include investigation of genetic and environmental influences--may lead to the development of novel treatments that attenuate this altered interoceptive prediction signal in patients with anxiety disorders.

Is obsessive-compulsive disorder an anxiety disorder?

Obsessive-compulsive disorder (OCD) is classified as an anxiety disorder in the DSM-IV-TR [American Psychiatric Association, 2000. Diagnostic and statistical manual of mental disorders, Fourth ed., rev. Washington, DC: Author]; however, the notion of a spectrum of obsessive-compulsive (OC) related disorders that is comprised of such disparate disorders as OCD, body dysmorphic disorder, certain eating disorders, pathological gambling, and autism, is gaining acceptance. The fact that these disorders share obsessive-compulsive features and evidence similarities in patient characteristics, course, comorbidity, neurobiology, and treatment response raises the question of whether OCD is best conceptualized as an anxiety or an OC spectrum disorder. This article reviews evidence from comorbidity and family studies, as well as biological evidence related to neurocircuitry, neurotransmitter function, and pharmacologic treatment response that bear on this question. The implications of removing OCD from the anxiety disorders category and moving it to an OC spectrum disorders category, as is being proposed for the DSM-V, is discussed.

Direct evidence that acutely enhancing serotonin with the selective serotonin reuptake inhibitor citalopram modulates the loudness dependence of the auditory evoked potential (LDAEP) marker of central serotonin function

The loudness dependence of the auditory evoked potential (LDAEP) has been suggested as a reliable measure of central serotonin function in humans. The most convincing evidence for a direct relationship between serotonergic function and LDAEP to date has come from animal studies, while evidence in humans has been circumstantial and inconsistent. In the current study, we examine the direct effect of serotonergic modulation with the selective serotonin reuptake inhibitor (SSRI) citalopram on the LDAEP. The study was a double-blind placebo controlled design in which healthy participants were tested under two acute treatment conditions: placebo and citalopram (20 mg). Enhancement of serotonin function with citalopram in comparison to placebo decreased the slope of the LDAEP (i.e. weaker LDAEP). The findings provide direct evidence in humans, of a relationship between central serotonin function and the LDAEP, supporting findings previously observed in animals and clinical populations. Together the results provide further support for the validity of the LDAEP as a non-invasive in vivo measure of central serotonin function in humans.

Effect of worry on regional cerebral blood flow in nonanxious subjects

Several studies suggest that cognitive tasks attenuate activation of the limbic system by emotional stimuli. We investigated the possibility that worry would similarly inhibit the limbic system by examining its effects on regional cerebral blood flow (rCBF). Ten nonanxious volunteers underwent four scans within one session, using positron emission tomography (PET) with H(2)(15)O as tracer. The first two scans recorded emotionally neutral thinking induced after listening to tapes describing neutral statements. Preceding the third and fourth scans, subjects listened to the self-recorded tape describing their individual worries, were instructed to continue to worry, and were scanned 5 min later. Subjects rated themselves as more anxious during the worry scans but showed no significant heart interbeat or skin conductance changes. During worry, rCBF increases were found bilaterally in the medial fronto-orbital gyri and the right thalamus; rCBF decreases were found bilaterally in the hippocampi and amygdalae, in the right insula, the left and right inferior, middle and superior temporal gyri and the occipito-temporal gyri, the right inferior occipital gyrus and the left supramarginal gyrus. Activity of the left orbito-frontal gyrus was negatively correlated with activity of the amygdalae. The results support the hypothesis that worry-induced prefrontal activity suppresses affect-related subcortical regions.

Generalized anxiety disorder: rethinking diagnosis and rating

Faye is a 44-year-old woman who presented complaining of tension. She felt tense in her muscles, her whole body felt “on edge,” and she was unable to relax or to fall asleep easily. The tension was not only physical but also mental, she experienced anxiety on and off throughout the day, had multiple worries, and often felt irritable. Ever since she could remember, she had been somewhat highly strung, but in her thirties she took a more stressful job, and there were often times when the physical symptoms became more intense and even interfered with her work function. During these periods of increased anxiety, she resorted to using benzodiazepine tablets prescribed by her primary care physician for poor sleep.

Chronic treatment with duloxetine is necessary for an anxiolytic-like response in the mouse zero maze: the role of the serotonin transporter

RATIONALE

Monoamine transporter inhibitor antidepressants have anxiolytic efficacy in man. However, preclinical data poorly reflect this, either because (1) few studies assess chronic antidepressant treatment in animal models, (2) antidepressants are anxiogenic after acute treatment; and (3) animal models of anxiety are insensitive to antidepressants.

OBJECTIVE

We address issues (1) and (2) and ascertain potential mechanisms mediating anxiolytic effects demonstrated.

METHODS

The effect of acute treatment with seven antidepressants covering the classes selective serotonin reuptake inhibitors, serotonin-noradrenaline reuptake inhibitors, noradrenaline reuptake inhibitors and tricyclic antidepressants were compared with the benzodiazepine, chlordiazepoxide, on the mouse zero maze, an unconditioned model of anxiety. Furthermore, citalopram, duloxetine, reboxetine and amitriptyline were assessed after chronic administration (10 mg/kg p.o., 21 days, twice daily) in this model. In mice treated chronically, (a) the hypothermic response to serotonin (5-HT)1A and 5-HT1B receptor ligands, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OHDPAT) and m-chlorophenyl piperazine (mCPP), respectively, was assessed and (b) serotonin transporter (SERT) and noradrenaline transporter (NET) densities in the cortex and hippocampus, respectively, were determined.

RESULTS

None of the antidepressants were anxiolytic after acute treatment, although reboxetine, duloxetine and amitriptyline were anxiogenic. Only chronic treatment with duloxetine induced an anxiolytic effect, which was dissociable from nonspecific motor effects. Duloxetine reduced SERT density in the cortex by approximately 75% compared to control, with no effect on NET density in the hippocampus. Citalopram and amitriptyline significantly reduced SERT density by approximately 20%, whereas reboxetine selectively reduced NET density. All drugs reduced the hypothermic response to 8-OHDPAT and mCPP.

CONCLUSION

Duloxetine was anxiolytic after chronic but not acute treatment, reflecting clinical experience with antidepressants in general. Duloxetine's anxiolytic-like profile may be ascribed to the considerable reduction in the density of the SERT in the cortex.