Serotonin-transporter-linked promoter region polymorphism and serotonin transporter binding in drug-naïve patients with major depression

The Emerging Role of SPECT Functional Neuroimaging in Schizophrenia and Depression

Over the last three decades, the brain's functional and structural imaging has become more prevalent in psychiatric research and clinical application. A substantial amount of psychiatric research is based on neuroimaging studies that aim to illuminate neural mechanisms underlying psychiatric disorders. Single-photon emission computed tomography (SPECT) is one of those developing brain imaging techniques among various neuroimaging technologies. Compared to PET, SPECT imaging is easy, less expensive, and practical for radioligand use. Current technologies increased the spatial accuracy of SPECT findings by combining the functional SPECT images with CT images. The radioligands bind to receptors such as 5-hydroxytryptamine 2A, and dopamine transporters can help us comprehend neural mechanisms of psychiatric disorders based on neurochemicals. This mini-review focuses on the SPECT-based neuroimaging approach to psychiatric disorders such as schizophrenia and major depressive disorder (MDD). Research-based SPECT findings of psychiatric disorders indicate that there are notable changes in biochemical components in certain disorders. Even though many studies support that SPECT can be used in psychiatric clinical practice, we still only use subjective diagnostic criteria such as the Diagnostic Statistical Manual of Mental Disorders (DSM-5). Glimpsing into the brain's biochemical world via SPECT in psychiatric disorders provides more information about the pathophysiology and future implication of neuroimaging techniques.

Influence of psychosocial stress on activation in human brain regions: moderation by the 5-HTTLPR genetic locus

Variants of the serotonin transporter linked polymorphic region (5-HTTLPR) of the serotonin transporter gene SLC6A4 have been related with the onset of depression, anxiety, and other mental disorders. Homozygotes for the short 5-HTTLPR variant, referred to as the SS genotype, have greater cortisol responses to experimentally induced psychosocial stress. In the current study, we used functional magnetic resonance imaging (fMRI) to compare regional brain activations across 5-HTTLPR genotypes in subjects performing the Montreal Imaging Stress Task (MIST). Subjects with an SS genotype had significant greater increases in cortisol concentrations after the task than subjects with at least one long 5-HTTLPR allele. Additionally, relative to L carriers, the SS group had greater activation in the dorsomedial prefrontal cortex(dmPFC), dorsal anterior cingulate cortex, anterior insula.

Disentangling the Neural Basis of Cognitive Behavioral Therapy in Psychiatric Disorders: A Focus on Depression

Background: Major depressive disorder (MDD) stands among the most frequent psychiatric disorders. Cognitive behavioral therapy (CBT) has been shown to be effective for treating depression, yet its neural mechanisms of action are not well elucidated. The objective of this work is to assess the available neuroimaging studies exploring CBT’s effects in adult patients with MDD. Methods: Computerized databases were consulted till April 2018 and a research was conducted according to PRISMA guidelines in order to identify original research articles published at any time in English and French languages on this topic. Results: Seventeen studies were identified. Only one study was randomized comparing CBT to pharmacological interventions, and none included an effective control. Following CBT, changes occurred in cerebral areas that are part of the fronto-limbic system, namely the cingulate cortex, prefrontal cortex and amygdala-hippocampal complex. However, the pattern of activation and connectivity in these areas varied across the studies. Conclusion: A considerable heterogeneity exists with regard to study design, adapted CBT type and intensity, and employed neuroimaging paradigms, all of which may partly explain the difference in studies’ outcomes. The lack of randomization and effective controls in most of them makes it difficult to draw formal conclusion whether the observed effects are CBT mediated or due to spontaneous recovery. Despite the observed inconsistencies and dearth of data, CBT appears to exert its anti-depressant effects mainly by modulating the function of affective and cognitive networks devoted to emotions generation and control, respectively. This concept remains to be validated in large scale randomized controlled trials.

Baseline symptom severity predicts serotonin transporter change during psychotherapy in patients with major depression

AIMS

The role of the serotonin transporter (SERT) in the pathophysiology of depression is unclear and only a few follow-up studies exist. Our aim was to measure changes in SERT availability during psychodynamic psychotherapy in patients with major depression over a follow-up time of 12 or 18 months.

METHODS

The patients were studied with iodine-123 labelled 2β-carbomethoxy-3β-(4-iodophenyl) serial single-photon emission tomography imaging and clinical rating scales of symptoms.

RESULTS

Changes in SERT availability had no correlation with the change of symptoms, but the change of SERT availability during psychotherapy in the midbrain was predicted by the baseline severity of the clinical symptoms measured by the Symptom Checklist Depression Scale and the Symptom Checklist Global Severity Index. With cut-off values applied, it was found that SERT availabilities increased in patients with high baseline symptoms, and decreased in patients with low baseline symptoms.

CONCLUSIONS

Together with our earlier finding of decreased SERT in patients with depression, these results indicate a state-dependent and possibly a compensatory role of decreased SERT availability in depression.

123I-ADAM SPET imaging of serotonin transporter in patients with epilepsy and comorbid depression

Background

Purpose of the study was to investigate alterations in midbrain serotonin transporter (SERT) binding in patients with epilepsy and symptoms of depression compared to patients with epilepsy with no symptoms of depression.

Methods

We studied 12 patients with epilepsy (7 patients had focal and 5 had generalized epilepsy syndromes). The presence of self-reported symptoms of depression was assessed using Beck Depression Inventory (BDI) and the Emotional State Questionnaire (EST-Q). The binding potential of the SERT was assessed by performing brain single photon emission tomography (SPET) using the SERT radioligand 2-((2-((dimethylamino)methyl)phenyl)thio)-5-(123)iodophenylamine (¹²³I-ADAM).

Results

Seven patients had BDI and EST-Q subscale scores greater than 11 points, which was interpreted as the presence of symptoms of depression. We found that ¹²³I-ADAM binding was not significantly different between patients with epilepsy with and without symptoms of depression. In addition, ¹²³I-ADAM binding did not show a significant correlation to either BDI or EST-Q depression subscale scores and did not differ between patients with focal vs. generalized epilepsy.

Conclusion

The results of our study failed to demonstrate alterations of SERT binding properties in patients with epilepsy with or without symptoms of depression.

Change over time in brain serotonin transporter binding in major depression: effects of therapy measured with [(123) I]-ADAM SPECT

Several studies have reported low brain serotonin transporter (SERT) binding in individuals with major depression. We hypothesized that the SERT standardized uptake ratio (SUR) values using [(123) I]-ADAM single photon emission computed tomography would increase in depressed subjects who responded to cognitive behavior therapy (CBT) compared to CBT nonresponders. [(123) I]-ADAM scans were acquired before and after 12 weeks of CBT from 20 depressed subjects and on two occasions 12 weeks apart from 10 nondepressed, healthy volunteers. The primary outcome measure was change over time in SUR values in the midbrain, medial temporal lobe, and basal ganglia regions. Depressed subjects demonstrated low pretreatment mean SUR values that significantly increased over time in the midbrain (P = .011), right medial temporal lobe (P = .008), and left medial temporal lobe (P = .000) regions. Treatment responders showed a significant increase over time in SUR values in left medial temporal lobe (P = .029) and right medial temporal lobe (P = .007) regions. Partial and nonresponder subjects also showed a significant increase over time in SUR values in the left medial temporal region (P = .040) (vs. healthy volunteers), but to a lesser degree. The findings suggest that low pretreatment SERT binding may increase over time in some depressed individuals who experience symptom improvement.

Low brain serotonin transporter binding in major depressive disorder

We examined midbrain, medial temporal lobe, and basal ganglia serotonin transporter (SERT) distribution volume ratio (DVR) values in subjects with major depressive disorder versus healthy volunteers using a selective SERT radioligand and single photon emission computed tomography (SPECT). We hypothesized that the DVR value for SERT binding would be lower in depressed versus non-depressed subjects. [(123)I]-ADAM SPECT scans were acquired from 20 drug free, depressed subjects and 20 drug-free depressed subjects and 10 drug-free healthy volunteers. The primary outcome measure was the DVR value for [(123)I]-ADAM uptake in the midbrain, medial temporal lobe, and basal ganglia regions. Depressed subjects demonstrated significantly lower DVR values in the midbrain, right and left medial temporal lobe, and right and left basal ganglia. There was significant probability that lower DVR values could distinguish between depressed and non-depressed subjects in the midbrain, medial temporal lobe, and the right and left basal ganglia. These findings confirm prior observations of lower SERT binding in depression, and suggest that low SERT binding may represent a putative biomarker of depression. Future studies are needed to confirm these observations.