An HPA-1a-positive platelet-depleting agent for prevention of fetal and neonatal alloimmune thrombocytopenia: a randomized, single-blind, placebo-controlled, single-center, phase 1/2 proof-of-concept study

BACKGROUND

Fetal/neonatal alloimmune thrombocytopenia (FNAIT) is a rare and potentially life-threatening bleeding disorder of the fetus/newborn. Antibodies against human platelet antigen 1a (HPA-1a) are associated with the most frequent FNAIT cases. There are no approved therapies for FNAIT prevention or treatment. RLYB211 is a polyclonal HPA-1a hyperimmune IgG being developed to prevent FNAIT.

OBJECTIVES

To investigate whether a single dose of anti-HPA-1a (1000 IU) could markedly accelerate the elimination of HPA-1ab platelets transfused into healthy, HPA-1a-negative participants as compared with placebo.

METHODS

This randomized, single-blind, placebo-controlled, single-center, phase 1/2 proof-of-concept study (EudraCT: 2019-003459-12) included HPA-1a- and HLA-A2-negative healthy men. Cohort 1 received intravenous RLYB211 or placebo 1 hour after transfusion of HPA-1ab platelets. Cohort 1B received RLYB211 or placebo, followed by platelet transfusion 1 week later. Primary endpoint was the half-life of transfused platelets in circulation after administration of RLYB211 or placebo, determined by flow cytometry. Proof of concept was ≥90% reduction of half-life relative to placebo.

RESULTS

Twelve participants were allocated to cohort 1 or 1B and randomized to receive RLYB211 (n = 9) or placebo (n = 3). RLYB211 markedly accelerated the elimination of HPA-1ab platelets in all participants vs placebo. In cohort 1B, this effect was observed 7 days after RLYB211 administration. Two treatment-emergent adverse events were possibly related to treatment, both in RLYB211-treated participants. No participants developed HPA-1a antibodies at 12 or 24 weeks.

CONCLUSION

These data support the hypothesis that anti-HPA-1a could be used as prophylaxis in women at risk of having an FNAIT-affected pregnancy.

Benefit-risk assessment and reporting in clinical trials of chronic pain treatments: IMMPACT recommendations

ABSTRACT

Chronic pain clinical trials have historically assessed benefit and risk outcomes separately. However, a growing body of research suggests that a composite metric that accounts for benefit and risk in relation to each other can provide valuable insights into the effects of different treatments. Researchers and regulators have developed a variety of benefit-risk composite metrics, although the extent to which these methods apply to randomized clinical trials (RCTs) of chronic pain has not been evaluated in the published literature. This article was motivated by an Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials consensus meeting and is based on the expert opinion of those who attended. In addition, a review of the benefit-risk assessment tools used in published chronic pain RCTs or highlighted by key professional organizations (ie, Cochrane, European Medicines Agency, Outcome Measures in Rheumatology, and U.S. Food and Drug Administration) was completed. Overall, the review found that benefit-risk metrics are not commonly used in RCTs of chronic pain despite the availability of published methods. A primary recommendation is that composite metrics of benefit-risk should be combined at the level of the individual patient, when possible, in addition to the benefit-risk assessment at the treatment group level. Both levels of analysis (individual and group) can provide valuable insights into the relationship between benefits and risks associated with specific treatments across different patient subpopulations. The systematic assessment of benefit-risk in clinical trials has the potential to enhance the clinical meaningfulness of RCT results.

Interpretation of chronic pain clinical trial outcomes: IMMPACT recommended considerations

Interpreting randomized clinical trials (RCTs) is crucial to making decisions regarding the use of analgesic treatments in clinical practice. In this article, we report on an Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT) consensus meeting organized by the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks, the purpose of which was to recommend approaches that facilitate interpretation of analgesic RCTs. We review issues to consider when drawing conclusions from RCTs, as well as common methods for reporting RCT results and the limitations of each method. These issues include the type of trial, study design, statistical analysis methods, magnitude of the estimated beneficial and harmful effects and associated precision, availability of alternative treatments and their benefit-risk profile, clinical importance of the change from baseline both within and between groups, presentation of the outcome data, and the limitations of the approaches used.

Inverse changes in raphe and cortical 5-HT1B receptor availability after acute tryptophan depletion in healthy human subjects

Serotonergic neurotransmission plays a key role in the pathophysiology and treatment of various neuropsychiatric diseases. The purpose of this study was to investigate changes in serotonergic neurotransmission after acute tryptophan depletion (ATD) using positron emission tomography (PET) with [¹¹ C]P943, a 5-HT_1B receptor radioligand previously shown to be sensitive to changes in 5-HT. Five healthy subjects were scanned on a high resolution PET scanner twice on the same day, before and approximately 5 hours after ingesting capsules containing an amino acid mixture that lacks tryptophan. For each scan, emission data were acquired for 120 min after intravenous bolus injection of [¹¹ C]P943. Binding potential (BP_ND ) values were estimated from parametric images using the second version of the multilinear reference tissue model (MRTM2, t* = 20 min) with cerebellar grey matter used as a reference region. The change in [¹¹ C]P943 binding (ΔBP_ND , %) was calculated as (BP_ND,post  - BP_ND,pre )/(BP_ND,pre ) × 100, and correlation analysis was performed to measure linear associations of ΔBP_ND between raphe and other regions of interest (ROIs). ΔBP_ND ranged from -6% to 45% in the raphe, with positive values indicating reduced competition from 5-HT. In cortical regions, ΔBP_ND ranged from -28% to 7%. While these changes did not reach significance, there were significant negative correlations of ΔBP_ND of the raphe with those of cerebral cortical regions and the thalamus (e.g., r = -.96, p = .011 for average cortex). These findings support the hypothesis that raphe serotonin is a critical modulator of cortical serotonin release via projecting neurons in healthy human subjects.

A Systematic Review and Pooled Analysis of Select Safety Parameters Among Normal Healthy Volunteers Taking Placebo in Phase 1 Clinical Trials

A systematic review of the Bristol‐Myers Squibb normal healthy volunteers (NHVs) database identified phase 1 trials that included NHVs administered placebo with the aim of characterizing normal inter‐ and intraindividual safety parameter variability. Twenty‐five single and multiple ascending dose studies, median duration 28 (2 to 63) days, were included in the pooled analysis (355 NHVs). Laboratory evaluations, vital signs, electrocardiograms, and adverse events were assessed. The most commonly occurring adverse event was headache (28 [7.9%] NHVs; 519.5 events/100 person‐years). During the dosing period (on placebo), evaluations showed 5.1 events/100 measures of alanine aminotransferase and 7.3 events/100 measures of creatine kinase 1× above the upper limit of normal. Alanine aminotransferase and creatine kinase elevations occurred in 28 (7.9%) and 39 (11.0%) NHVs, respectively; 105 (30.3%) NHVs had low and 46 (13.3%) had high diastolic blood pressure. This analysis may inform future study designs and provide a context for interpretation of safety signals in early phase clinical trials.

OCD is associated with an altered association between sensorimotor gating and cortical and subcortical 5-HT1b receptor binding

Obsessive-compulsive disorder (OCD) is characterized by impaired sensorimotor gating, as measured using prepulse inhibition (PPI). This effect may be related to abnormalities in the serotonin (5-HT) system. 5-HT1B agonists can impair PPI, produce OCD-like behaviors in animals, and exacerbate OCD symptoms in humans. We measured 5-HT1B receptor availability using (11)C-P943 positron emission tomography (PET) in unmedicated, non-depressed OCD patients (n=12) and matched healthy controls (HC; n=12). Usable PPI data were obtained from 20 of these subjects (10 from each group). There were no significant main effects of OCD diagnosis on 5-HT1B receptor availability ((11)C-P943 BPND); however, the relationship between PPI and (11)C-P943 BPND differed dramatically and significantly between groups. 5-HT1B receptor availability in the basal ganglia and thalamus correlated positively with PPI in controls; these correlations were lost or even reversed in the OCD group. In cortical regions there were no significant correlations with PPI in controls, but widespread positive correlations in OCD patients. Positive correlations between 5-HT1B receptor availability and PPI were consistent across diagnostic groups only in two structures, the orbitofrontal cortex and the amygdala. Differential associations of 5-HT1B receptor availability with PPI in patients suggest functionally important alterations in the serotonergic regulation of cortical/subcortical balance in OCD.

Comparison of different QT interval correction methods for heart rate and QT beat-to-beat method in a thorough QT study of triple monoamine reuptake inhibitor BMS-820836

As BMS-820836 causes dose-dependent heart rate increases, QTcI, QTcF, QTcB, and QT beat-to-beat methods were compared in this thorough QT study in healthy subjects. Two parallel groups of subjects (n = 60 per group) received 2 mg (maximum therapeutic) or 4 mg (supratherapeutic) of BMS-820836 once daily for 14 days with uptitration. Another 60 subjects received encapsulated moxifloxacin (400 mg) or matching placebo in a nested-crossover study design. Compared with QTcF and QTcB, baseline QTcI had the smallest and near-zero Pearson correlation coefficient with heart rate (0.0938), which supported the choice of QTcI as the primary electrocardiographic end point. BMS-820836 was not associated with prolongation of the QT interval at the doses tested; however, ΔΔQTbtb showed the smallest deviation from 0 milliseconds compared with ΔΔQTcI and ΔΔQTcF. The ΔΔQTbtb results appeared to be more consistent with the very low likelihood of any effect on the QT interval by BMS-820836 based on the wide margin (>400×) of the in vitro hERG IC50 and free plasma concentration. Further, this is the first published study that used the nested-crossover design and QTbtb analysis in a thorough QT study. Assay sensitivity was confirmed with encapsulated moxifloxacin.

Safety, pharmacokinetic, and positron emission tomography evaluation of serotonin and dopamine transporter occupancy following multiple-dose administration of the triple monoamine reuptake inhibitor BMS-820836

RATIONALE

BMS-820836 is a novel antidepressant that selectively inhibits the reuptake of serotonin, norepinephrine, and dopamine.

OBJECTIVE

This Phase I study assessed safety, tolerability, and pharmacokinetics of multiple daily doses of BMS-820836 in healthy subjects. Central serotonin transporter (SERT) and dopamine transporter (DAT) occupancy were assessed using positron emission tomography and [(11)C]MADAM or [(11)C]PE2I, respectively.

METHODS

Fifty-seven healthy volunteers were enrolled in this double-blind, placebo-controlled, ascending multiple-dose study (ClincalTrials.gov identifier: NCT00892840). Eight participants in seven dose cohorts received oral doses of BMS-820836 (0.1-4 mg) or placebo for 14 days to assess safety, tolerability, and pharmacokinetics. Additionally, SERT and DAT occupancies were evaluated in 4-8 subjects per cohort at 8 h post-dose on Day 10 and 24 h post-dose on Day 15 at anticipated steady-state conditions.

RESULTS

Most adverse events were mild to moderate; there were no serious safety concerns. Median maximum concentrations of BMS-820836 were observed at 4.0-5.5 h post-dose; estimated elimination half-life was 44-74 h. About 80 % striatal SERT occupancy was achieved after multiple doses of 0.5 mg BMS-820836 at both 8 and 24 h post-dose. Striatal DAT occupancy ranged between 14 % and 35 % at 8 h post-dose with a slight decline at 24 h post-dose.

CONCLUSIONS

Multiple daily doses of up to 4 mg BMS-820836 appeared to be generally safe and well tolerated in a healthy population. SERT and DAT occupancies were in a range associated with therapeutic efficacy of antidepressants. Together with the pharmacokinetic profile of BMS-820836, the occupancy data support once-daily administration.

Test-retest reliability of the novel 5-HT1B receptor PET radioligand [11C]P943

PURPOSE

[(11)C]P943 is a novel, highly selective 5-HT1B PET radioligand. The aim of this study was to determine the test-retest reliability of [(11)C]P943 using two different modeling methods and to perform a power analysis with each quantification technique.

METHODS

Seven healthy volunteers underwent two PET scans on the same day. Regions of interest (ROIs) were the amygdala, hippocampus, pallidum, putamen, insula, frontal, anterior cingulate, parietal, temporal and occipital cortices, and cerebellum. Two multilinear radioligand quantification techniques were used to estimate binding potential: MA1, using arterial input function data, and the second version of the multilinear reference tissue model analysis (MRTM2), using the cerebellum as the reference region. Between-scan percent variability and intraclass correlation coefficients (ICC) were used to assess test-retest reliability. We also performed power analyses to determine the method that would allow the least number of subjects using within-subject or between-subject study designs. A voxel-wise ICC analysis for MRTM2 BPND was performed for the whole brain and all the ROIs studied.

RESULTS

Mean percent variability between two scans across regions ranged between 0.4 % and 12.4 % for MA1 BPND, 0.5 % and 11.5 % for MA1 BPP, 16.7 % and 28.3 % for MA1 BPF, and between 0.2 % and 5.4 % for MRTM2 BPND. The power analyses showed a greater number of subjects were required using MA1 BPF compared with other outcome measures for both within-subject and between-subject study designs. ICC values were the highest using MRTM2 BPND and the lowest with MA1 BPF in ten ROIs. Small regions and regions with low binding had lower ICC values than large regions and regions with high binding.

CONCLUSION

Reliable measures of 5-HT1B receptor binding can be obtained using the novel PET radioligand [(11)C]P943. Quantification of 5-HT1B receptor binding with MRTM2 BPND and with MA1 BPP provided the least variability and optimal power for within-subject and between-subject designs.

Reductions in brain 5-HT1B receptor availability in primarily cocaine-dependent humans

BACKGROUND

Preclinical evidence implicates the serotonin receptor 5-hydroxytryptamine 1B (5-HT1B) in the effects of cocaine. This study explores 5-HT1B in humans by examining receptor availability in vivo in subjects whose primary addiction is cocaine dependence (CD) using positron emission tomography.

METHODS

Study participants included 14 medically healthy subjects with CD (mean age = 41 ± 6 years) who were compared with 14 age-matched healthy control subjects (mean age = 41 ± 8 years) with no past or current history of cocaine or other illicit substance abuse. Participants underwent magnetic resonance imaging followed by positron emission tomography with the highly selective 5-HT1B tracer, [(11)C]P943, for purposes of quantifying regional binding potential. Voxel-based morphometry and gray matter masking also were employed to control for potential partial volume effects.

RESULTS

The [(11)C]P943 positron emission tomography imaging data in nine candidate regions (amygdala, anterior cingulate cortex, caudate, frontal cortex, hypothalamus, pallidum, putamen, thalamus, and ventral striatum) showed significant or nearly significant reductions of regional binding potential in subjects with CD in three regions: anterior cingulate (-16%, p < .01), hypothalamus (-16%, p = .03), and frontal cortex (-7%, p = .08). Voxel-based morphometry showed significant gray matter reductions in the frontal cortex of subjects with CD. After gray matter masking, statistically significant reductions in the [(11)C]P943 regional binding potential were either retained (anterior cingulate, -14%, p = .01; hypothalamus, -20%, p < .01) or achieved (frontal cortex, -14%, p < .01). Whole-brain voxel-wise parameter estimation confirmed these results. Secondary analyses were also significant in some regions for years of cocaine and daily tobacco use.

CONCLUSIONS

The reductions found in this study suggest that 5-HT1B receptors may contribute to the etiology or expression of CD and potentially represent a target for medication development.

Evaluation of safety and tolerability, pharmacokinetics, and pharmacodynamics of BMS-820836 in healthy subjects: a placebo-controlled, ascending single-dose study

RATIONALE

BMS-820836, a novel triple monoamine reuptake inhibitor, is an experimental monotherapy for sufferers of major depressive disorder who have had an inadequate response to an existing antidepressant treatment.

OBJECTIVES

This study was conducted to evaluate the safety and tolerability, pharmacokinetics (PK), and serotonin transporter (SERT) and dopamine transporter (DAT) occupancy for single doses of BMS-820836 in healthy subjects.

METHODS

Healthy subjects were assigned to seven BMS-820836 dose panels (0.025, 0.1, 0.5, 1, 2, 3, and 5 mg; n = 8 each), in which subjects were randomly allocated 3:1 to a single BMS-820836 dose or matched placebo. Serial blood samples were collected on Days 1, 2, 3, 4, 7, and 14 to characterize the PK of BMS-820836. Following evaluation of the maximum tolerated dose, SERT occupancy was determined by applying [(11)C]DASB positron emission tomography (PET) after single-dose BMS-820836 (0.5 or 3 mg; n = 3 each) and DAT occupancy by applying [(11)C]PE2I PET after single-dose BMS-820836 (3 mg; n = 6).

RESULTS

Single oral doses of BMS-820836 (0.025-3 mg) were generally safe and well tolerated. BMS-820836 had a median T max of 5.0-7.2 h and a mean apparent terminal T 1/2 of 34-57 h. Mean striatal SERT occupancies were 19 ± 9 % and 82 ± 8 % after single doses of 0.5 and 3 mg BMS-820836, respectively. The mean striatal DAT occupancy was 19 ± 9 % after a single 3 mg BMS-820836 dose.

CONCLUSIONS

Single doses of BMS-820836 have meaningful SERT and DAT occupancy and demonstrate an acceptable safety and tolerability profile in healthy control subjects.

The impact of NMDA receptor blockade on human working memory-related prefrontal function and connectivity

Preclinical research suggests that N-methyl-D-aspartate glutamate receptors (NMDA-Rs) have a crucial role in working memory (WM). In this study, we investigated the role of NMDA-Rs in the brain activation and connectivity that subserve WM. Because of its importance in WM, the lateral prefrontal cortex, particularly the dorsolateral prefrontal cortex and its connections, were the focus of analyses. Healthy participants (n=22) participated in a single functional magnetic resonance imaging session. They received saline and then the NMDA-R antagonist ketamine while performing a spatial WM task. Time-course analysis was used to compare lateral prefrontal activation during saline and ketamine administration. Seed-based functional connectivity analysis was used to compare dorsolateral prefrontal connectivity during the two conditions and global-based connectivity was used to test for laterality in these effects. Ketamine reduced accuracy on the spatial WM task and brain activation during the encoding and early maintenance (EEM) period of task trials. Decrements in task-related activation during EEM were related to performance deficits. Ketamine reduced connectivity in the DPFC network bilaterally, and region-specific reductions in connectivity were related to performance. These results support the hypothesis that NMDA-Rs are critical for WM. The knowledge gained may be helpful in understanding disorders that might involve glutamatergic deficits such as schizophrenia and developing better treatments.

Changes in the cholinergic system between bipolar depression and euthymia as measured with [123I]5IA single photon emission computed tomography

BACKGROUND

The cholinergic system is substantially altered in individuals with major depression and is partially restored when depression remits. We quantified the availability of β2-subunit-containing nicotinic acetylcholine receptors (β2*-nAChR) in subjects with bipolar disorder.

METHODS

Twenty-five subjects with bipolar disorder (15 depressed, 10 euthymic) and 25 sex- and age-matched control subjects had a [(123)I]5IA-85380 single photon emission computed tomography scan to quantify β2*-nAChR VT/fP (total volume of distribution, corrected for individual differences in metabolism and protein binding of the radiotracer). Average VT/fP was compared between groups and correlated with clinical characteristics. Postmortem analysis of β2*-nAChRs was conducted using equilibrium binding with [(125)I]5IA in subjects with bipolar disorder and matched control subjects.

RESULTS

We showed significantly lower β2*-nAChR availability (20%-38%) in subjects with bipolar depression compared with euthymic and control subjects across all brain regions assessed (frontal, parietal, temporal, and anterior cingulate cortex, hippocampus, amygdala, thalamus, striatum). The postmortem binding study in which endogenous acetylcholine was washed out did not show a statistically significant difference in β2*-nAChR number in temporal cortex of the bipolar depressed and control groups (15% difference; p = .2).

CONCLUSIONS

We show that the alteration in the cholinergic system observed during a depressive episode appears to resolve during euthymia. We suggest that lower VT/fP observed in vivo may be due to a combination of higher endogenous acetylcholine levels during depression, which could compete with radiotracer binding to the receptor in vivo, and lower receptor number in bipolar depression. Identification of differences in cholinergic signaling in subjects with bipolar depression may improve our understanding of its etiology and reveal new treatment targets.

Relationship of resting brain hyperconnectivity and schizophrenia-like symptoms produced by the NMDA receptor antagonist ketamine in humans

N-methyl-D-aspartate glutamate receptor (NMDA-R) antagonists produce schizophrenia-like positive and negative symptoms in healthy human subjects. Preclinical research suggests that NMDA-R antagonists interfere with the function of gamma-aminobutyric acid (GABA) neurons and alter the brain oscillations. These changes have been hypothesized to contribute to psychosis. In this investigation, we evaluated the hypothesis that the NMDA-R antagonist ketamine produces alterations in cortical functional connectivity during rest that are related to symptoms. We administered ketamine to a primary sample of 22 subjects and to an additional, partially overlapping, sample of 12 subjects. Symptoms before and after the experimental session were rated with the Positive and Negative Syndrome Scale (PANSS). In the primary sample, functional connectivity was measured via functional magnetic resonance imaging almost immediately after infusion began. In the additional sample, this assessment was repeated after 45 min of continuous ketamine infusion. Global, enhanced functional connectivity was observed at both timepoints, and this hyperconnectivity was related to symptoms in a region-specific manner. This study supports the hypothesis that pathological increases in resting brain functional connectivity contribute to the emergence of positive and negative symptoms associated with schizophrenia.

A single-day paradigm of self-regulated human cocaine administration

Prior work by our group has shown the feasibility, safety, and validity of a multi-day, multi-dose paradigm of self-regulated cocaine administration in humans. The current work sought to consolidate these methods in a single-day design focused on reducing logistical complexity, decreasing research burden to human subjects, and increasing suitability for medication development designs.

METHODS

Eleven experienced cocaine users participated in a 6-hour, single-day design, consisting of one safety/eligibility and three experimental cocaine periods (during which subjects were allowed to self-administer 8, 16, and 32 mg/70 kg cocaine doses under a fixed-ratio 1:5 minute timeout schedule). Changes in cocaine-induced cardiovascular response, self-administration behavior, and subjective effects were assessed.

RESULTS

Procedures were well tolerated by participants, and no significant adverse events were noted. Significant (p < 0.05), changes in measures of cocaine self-administration (e.g., responses, infusions, interinfusion intervals, consumption, and plasma levels), cardiovascular response (HR), and subjective effects (“high”) were observed. In contrast, cocaine-induced increases in other vital signs (e.g., SBP, DBP) and subjective effect measures (e.g., paranoia) did not differ between doses.

CONCLUSIONS

These data support the safety, tolerability and validity of our single-day design. Depending on the application, such methods may afford advantages for assessing the self-regulation of cocaine administration behavior in humans (e.g., including medication development designs).

Effects of ketamine in treatment-refractory obsessive-compulsive disorder

BACKGROUND

Treatments for obsessive-compulsive disorder (OCD) usually lead to incomplete symptom relief and take a long-time to reach full effect. Convergent evidence suggests that glutamate abnormalities contribute to the pathogenesis of OCD. Ketamine is a potent noncompetitive antagonist of the N-methyl-D-aspartate glutamate receptor. Trials have reported rapid antidepressant effects after low-dose ketamine infusion.

METHODS

We conducted an open-label trial of ketamine (.5 mg/kg IV over 40 min) in 10 subjects with treatment-refractory OCD. Response was defined as >35% improvement in OCD symptoms and >50% improvement in depression symptoms from baseline at any time between 1 and 3 days after infusion.

RESULTS

None of 10 subjects experienced a response in OCD symptoms in the first 3 days after ketamine. Four of seven patients with comorbid depression experienced an antidepressant response to ketamine in the first 3 days after infusion. Both OCD and depression symptoms demonstrated a statistically significant improvement in the first 3 days after infusion compared with baseline, but the OCD response was <12%. The percentage reduction in depressive symptoms in the first 3 days after ketamine infusion was significantly greater than the reduction in OCD symptoms.

CONCLUSIONS

Ketamine effects on OCD symptoms, in contrast to depressive symptoms, did not seem to persist or progress after the acute effects of ketamine had dissipated.

Increased ratio of anti-apoptotic to pro-apoptotic Bcl2 gene-family members in lithium-responders one month after treatment initiation

Background

Lithium is considered by many as the gold standard medication in the management of bipolar disorder (BD). However, the clinical response to lithium is heterogeneous, and the molecular basis for this difference in response is unknown. In the present study, we sought to determine how the peripheral blood gene expression profiles of patients with bipolar disorder (BD) changed over time following intitiation of treatment with lithium, and whether differences in those profiles over time were related to the clinical response.

Methods

Illumina Sentrix Beadchip (Human-6v2) microarrays containing > 48,000 transcript probes were used to measure levels of expression of gene-expression in peripheral blood from 20 depressed subjects with BD prior to and every two weeks during 8 weeks of open-label treatment with lithium.

Changes in gene-expression were compared between treatment responders (defined as a decrease in the Hamilton Depression Rating Scale of 50% or more) and non-responders. Pathway analysis was conducted using GeneGO Metacore software.

Results

127 genes showed a differential response in responders vs. non-responders. Pathway analysis showed that regulation of apoptosis was the most significantly affected pathway among these genes. Closer examination of the time-course of changes among BCL2 related genes showed that in lithium-responders, one month after starting treatment with lithium, several anti-apoptotic genes including Bcl2 and insulin receptor substrate 2 (IRS2) were up-regulated, while pro-apoptotic genes, including BCL2-antagonist/killer 1 (BAK1) and BCL2-associated agonist of cell death (BAD), were down-regulated. In contrast, in lithium non-responders, BCL2 and IRS2 were down-regulated, while BAK1 and BAD up-regulated at the one-month time-point.

Conclusions

These results suggest that differential changes in the balance of pro- and anti- apoptotic gene-expression following treatment with lithium may explain some of the heterogeneity in clinical response in BD patients.

Persistent β2*-nicotinic acetylcholinergic receptor dysfunction in major depressive disorder

BACKGROUND

Modulation of nicotinic acetylcholine receptors (nAChRs), specifically those containing the β2 subunit, may be effective in treating patients with major depressive disorder. Using [123I]5-I-A-85380 single photon emission computed tomography (SPECT), the authors studied the availability of β2-subunit-containing nAChRs (β2*-nAChRs) in depressed patients. To understand its molecular basis, the authors also studied β2*-nAChR binding in postmortem brain samples from depressed subjects.

METHOD

The participants were 23 medication-free, nonsmoking subjects with familial, early-onset depression (eight acutely ill and 15 recovered) and 23 age- and gender-matched nonsmoking comparison subjects. Each received one [123I]5-I-A-85380 SPECT scan and an MRI scan. The availability of β2*-nAChRs was quantified as VT/fP. Postmortem analysis of β2*-nAChR binding was conducted with [123I]5-I-A-85380 on prefrontal cortex samples from 14 depressed subjects and 14 age-matched comparison subjects.

RESULTS

The β2*-nAChR availability in both the acutely ill and recovered depressed subjects was significantly lower across all brain regions than in the respective comparison subjects, and it was lower in the acutely ill subjects than in those who were recovered. In the depressed patients, β2*-nAChR availability was significantly correlated with lifetime number of depressive episodes, trauma score, and anxiety score. There were no differences in β2*-nAChR number between groups in the postmortem study.

CONCLUSIONS

Depressed patients have lower β2*-nAChR availability than do healthy subjects. The difference between β2*-nAChR availability in vivo and in post-mortem samples may be analogous to data with dopaminergic PET ligands and dopamine receptor availability; lower receptor availability for the SPECT ligand could be caused by greater endogenous acetylcholine.

Age effects on serotonin receptor 1B as assessed by PET

Previous imaging studies have suggested that there is an age-related decline in brain serotonin (5-hydroxytryptamine) measures in healthy subjects. This paper addresses whether the availability of 5-hydroxytryptamine receptor 1B (5-HT(1B)) is seen to decrease with aging via PET imaging.

METHODS

Forty-eight healthy control subjects (mean age ± SD, 30 ± 10 y; age range, 18-61 y; 33 men, 15 women) underwent (11)C-P943 scanning on a high-resolution PET tomograph. Regions were examined with and without gray matter masking, the latter in an attempt to control for age-related gray matter atrophy on nondisplaceable binding potential (BP(ND)) as determined by a validated multilinear reference tissue model.

RESULTS

5-HT(1B) BP(ND) decreased in the cortex at an average rate of 8% per decade without and 9% with gray matter masking. A negative association with age was also observed in all individual cortical regions. Differences in the putamen and pallidum (positive association) were significant after adjustment for multiple comparisons. No sex- or race-related effects on 5-HT(1B) BP(ND) were found in any regions.

CONCLUSION

These findings indicate that age is a relevant factor for 5-HT(1B) in the cortex of healthy adults.

Considerations for improving assay sensitivity in chronic pain clinical trials: IMMPACT recommendations

A number of pharmacologic treatments examined in recent randomized clinical trials (RCTs) have failed to show statistically significant superiority to placebo in conditions in which their efficacy had previously been demonstrated. Assuming the validity of previous evidence of efficacy and the comparability of the patients and outcome measures in these studies, such results may be a consequence of limitations in the ability of these RCTs to demonstrate the benefits of efficacious analgesic treatments vs placebo ("assay sensitivity"). Efforts to improve the assay sensitivity of analgesic trials could reduce the rate of falsely negative trials of efficacious medications and improve the efficiency of analgesic drug development. Therefore, an Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials consensus meeting was convened in which the assay sensitivity of chronic pain trials was reviewed and discussed. On the basis of this meeting and subsequent discussions, the authors recommend consideration of a number of patient, study design, study site, and outcome measurement factors that have the potential to affect the assay sensitivity of RCTs of chronic pain treatments. Increased attention to and research on methodological aspects of clinical trials and their relationships with assay sensitivity have the potential to provide the foundation for an evidence-based approach to the design of analgesic clinical trials and expedite the identification of analgesic treatments with improved efficacy and safety.

Quantification of ligand PET studies using a reference region with a displaceable fraction: application to occupancy studies with [(11)C]-DASB as an example

This paper aims to build novel methodology for the use of a reference region with specific binding for the quantification of brain studies with radioligands and positron emission tomography (PET). In particular: (1) we introduce a definition of binding potential BP(D)=DVR-1 where DVR is the volume of distribution relative to a reference tissue that contains ligand in specifically bound form, (2) we validate a numerical methodology, rank-shaping regularization of exponential spectral analysis (RS-ESA), for the calculation of BP(D) that can cope with a reference region with specific bound ligand, (3) we demonstrate the use of RS-ESA for the accurate estimation of drug occupancies with the use of correction factors to account for the specific binding in the reference. [(11)C]-DASB with cerebellum as a reference was chosen as an example to validate the methodology. Two data sets were used; four normal subjects scanned after infusion of citalopram or placebo and further six test-retest data sets. In the drug occupancy study, the use of RS-ESA with cerebellar input plus corrections produced estimates of occupancy very close the ones obtained with plasma input. Test-retest results demonstrated a tight linear relationship between BP(D) calculated either with plasma or with a reference input and high reproducibility.

Abnormal prefrontal activity subserving attentional control of emotion in remitted depressed patients during a working memory task with emotional distracters

BACKGROUND

Patients with major depressive disorder (MDD) show deficits in processing of facial emotions that persist beyond recovery and cessation of treatment. Abnormalities in neural areas supporting attentional control and emotion processing in remitted depressed (rMDD) patients suggests that there may be enduring, trait-like abnormalities in key neural circuits at the interface of cognition and emotion, but this issue has not been studied systematically.

METHOD

Nineteen euthymic, medication-free rMDD patients (mean age 33.6 years; mean duration of illness 34 months) and 20 age- and gender-matched healthy controls (HC; mean age 35.8 years) performed the Emotional Face N-Back (EFNBACK) task, a working memory task with emotional distracter stimuli. We used blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) to measure neural activity in the dorsolateral (DLPFC) and ventrolateral prefrontal cortex (VLPFC), orbitofrontal cortex (OFC), ventral striatum and amygdala, using a region of interest (ROI) approach in SPM2.

RESULTS

rMDD patients exhibited significantly greater activity relative to HC in the left DLPFC [Brodmann area (BA) 9/46] in response to negative emotional distracters during high working memory load. By contrast, rMDD patients exhibited significantly lower activity in the right DLPFC and left VLPFC compared to HC in response to positive emotional distracters during high working memory load. These effects occurred during accurate task performance.

CONCLUSIONS

Remitted depressed patients may continue to exhibit attentional biases toward negative emotional information, reflected by greater recruitment of prefrontal regions implicated in attentional control in the context of negative emotional information.

Levetiracetam in the management of bipolar depression: a randomized, double-blind, placebo-controlled trial

OBJECTIVE

To study the efficacy of adjunctive levetiracetam therapy compared with placebo in the treatment of subjects with depression with bipolar disorder.

METHOD

This double-blind, placebo-controlled clinical trial randomly assigned outpatients with bipolar disorder type I and type II who were experiencing a major depressive episode (Structured Clinical Interview for DSM-IV Axis I Disorders-Clinician Version criteria) to treatment with either placebo or adjunctive levetiracetam (up to 2,500 mg/d flexibly dosed) for 6 weeks. The subjects were recruited from October 2005 to June 2008. The primary efficacy measure was mean change from baseline to week 6 in the Hamilton Depression Rating Scale (21-item). Secondary efficacy assessments included the Montgomery-Åsberg Depression Rating Scale, the Beck Depression Inventory, the Clinical Global Impressions-Bipolar Version scale, the Hamilton Anxiety Rating Scale, and the Young Mania Rating Scale.

RESULTS

Of 42 subjects randomly assigned to placebo or drug, 32 received at least 1 postbaseline assessment and thus were included in the analysis. The mean (SD) levetiracetam daily dose at endpoint evaluation was 1,132 (425) mg/d. There was no significant difference in the mean change from baseline to week 6 in the Hamilton Depression Rating Scale scores for levetiracetam compared with placebo. There were no significant differences in any of the secondary outcome measures.

CONCLUSIONS

Levetiracetam adjunctive therapy was not superior to placebo in the short-term treatment of subjects with depression with bipolar disorder in the population studied.

TRIAL REGISTRATION

Clinicaltrials.gov Identifier: NCT00566150.

Assessing the sensitivity of [¹¹C]p943, a novel 5-HT1B radioligand, to endogenous serotonin release

The main objective of the current study was to determine the sensitivity of the positron emission tomography (PET) radioligand [¹¹C]P943 to fenfluramine-induced changes in endogenous 5-HT in nonhuman primate brain. Fenfluramine-induced changes in 5-HT(1B) occupancy were compared to those obtained by self-block with unlabeled P943. Two baboons and 1 rhesus monkey were given preblocking or displacing doses of fenfluramine (1-5 mg/kg) or preblocking doses of unlabeled P943 (0.2 mg/kg) and imaged with [¹¹C]P943 PET. Receptor occupancy by the low dose of fenfluramine (1 mg/kg) in the baboons was 25 and 29% and by the high dose of fenfluramine (5 mg/kg) in the rhesus macaque was 42%. Receptor occupancy by P943 (0.2 mg/kg) was 68 and 86% in the baboons. PET imaging of 5-HT(1B) receptors with [¹¹C]P943 may be a useful approach for measuring changes in endogenous 5-HT in the living human brain.

Time course of regional brain activity accompanying auditory verbal hallucinations in schizophrenia

BACKGROUND

The pathophysiology of auditory verbal hallucinations remains poorly understood.

AIMS

To characterise the time course of regional brain activity leading to auditory verbal hallucinations.

METHOD

During functional magnetic resonance imaging, 11 patients with schizophrenia or schizoaffective disorder signalled auditory verbal hallucination events by pressing a button. To control for effects of motor behaviour, regional activity associated with hallucination events was scaled against corresponding activity arising from random button-presses produced by 10 patients who did not experience hallucinations.

RESULTS

Immediately prior to the hallucinations, motor-adjusted activity in the left inferior frontal gyrus was significantly greater than corresponding activity in the right inferior frontal gyrus. In contrast, motor-adjusted activity in a right posterior temporal region overshadowed corresponding activity in the left homologous temporal region. Robustly elevated motor-adjusted activity in the left temporal region associated with auditory verbal hallucinations was also detected, but only subsequent to hallucination events. At the earliest time shift studied, the correlation between left inferior frontal gyrus and right temporal activity was significantly higher for the hallucination group compared with non-hallucinating patients.

CONCLUSIONS

Findings suggest that heightened functional coupling between the left inferior frontal gyrus and right temporal regions leads to coactivation in these speech processing regions that is hallucinogenic. Delayed left temporal activation may reflect impaired corollary discharge contributing to source misattribution of resulting verbal images.

Association of frontal and posterior cortical gray matter volume with time to alcohol relapse: a prospective study

OBJECTIVE

Alcoholism is associated with gray matter volume deficits in frontal and other brain regions. Whether persistent brain volume deficits in abstinence are predictive of subsequent time to alcohol relapse has not been established. The authors measured gray matter volumes in healthy volunteers and in a sample of treatment-engaged, alcohol-dependent patients after 1 month of abstinence and assessed whether smaller frontal gray matter volume was predictive of subsequent alcohol relapse outcomes.

METHOD

Forty-five abstinent alcohol-dependent patients in treatment and 50 healthy comparison subjects were scanned once using high-resolution (T(1)-weighted) structural MRI, and voxel-based morphometry was used to assess regional brain volume differences between the groups. A prospective study design was used to assess alcohol relapse in the alcohol-dependent group for 90 days after discharge from 6 weeks of inpatient treatment.

RESULTS

Significantly smaller gray matter volume in alcohol-dependent patients relative to comparison subjects was seen in three regions: the medial frontal cortex, the right lateral prefrontal cortex, and a posterior region surrounding the parietal-occipital sulcus. Smaller medial frontal and parietal-occipital gray matter volumes were each predictive of shorter time to any alcohol use and to heavy drinking relapse.

CONCLUSIONS

These findings are the first to demonstrate that gray matter volume deficits in specific medial frontal and posterior parietal-occipital brain regions are predictive of an earlier return to alcohol use and relapse risk, suggesting a significant role for gray matter atrophy in poor clinical outcomes in alcoholism. Extent of gray matter volume deficits in these regions could serve as useful neural markers of relapse risk and alcoholism treatment outcome.

Citalopram reduces endotoxin-induced fatigue

Increased levels of inflammatory cytokines such as tumor necrosis factor (TNF) and interleukin-6 (IL-6) may play a role in depression. Mild depressive-like symptoms can be induced in humans through activation of the innate immune system with endotoxin. Whether preventive treatment with antidepressants can reduce endotoxin-induced symptoms has never been tested. In a double-blind, randomized, placebo-controlled, cross-over study, we administered intravenous low-dose endotoxin (0.8 ng/kg) or placebo to 11 healthy subjects who had received oral pre-treatment with citalopram (10 mg twice a day) or placebo for 5 days. The Montgomery-Åsberg Depression Rating Scale, the State and Trait Anxiety Inventory, and a visual analog scale were used to measure depressive and anxiety symptoms and social anhedonia. Serum levels of TNF and IL-6 were measured with immunoassays. Compared to placebo, endotoxin administration increased serum levels of TNF and IL-6, and caused mild depressive-like symptoms, in particular lassitude and social anhedonia. While citalopram pre-treatment had no effect on the innate immune response to endotoxin, it reduced the endotoxin-induced MADRS total score by 50%, with a moderate effect size (Cohen's d=0.5). Most of the MADRS total score was due to the lassitude item, and citalopram pre-treatment specifically reduced endotoxin-induced lassitude with a large effect size (Cohen's d=0.9). These results suggest that subchronic pre-treatment with the serotonin-reuptake inhibitor citalopram blunts mood symptoms induced by acute immune system activation with endotoxin without inhibiting the peripheral immune response.

Increased peripheral blood expression of electron transport chain genes in bipolar depression

OBJECTIVE

  To identify specific genetic pathways showing altered expression in peripheral blood of depressed subjects with bipolar disorder (BPD).

METHODS

  Illumina Sentrix BeadChip (Human-6v2) microarrays containing >48,000 transcript probes were used to measure levels of gene expression in peripheral blood from 20 depressed subjects with BPD and in 15 healthy control subjects. Quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) was used to confirm a subset of these differences.

RESULTS

  A total of 1,180 genes were differentially expressed between subjects with BPD and healthy controls (fold-change >1.3, false discovery rate-corrected p < 0.05, covaried for age and sex). Of these, 559 genes were up-regulated in BPD subjects and 621 were down-regulated. Surprisingly, there was no difference between medicated (n = 11) and unmedicated (n = 9) subjects with BPD for any of these genes. Pathway analysis using GeneGo MetaCore software showed that the most significantly affected pathway was the mitochondrial electron transport chain (ETC). Of the 85 objects (genes or proteins) in this pathway, 22 were up-regulated and 2 down-regulated in subjects with BPD. qRT-PCR confirmed up-regulation of nuclear encoded ETC genes in complexes I, III, IV, and V and, in addition, demonstrated up-regulation of mitochondrially encoded genes in each of these complexes.

CONCLUSION

  These results suggest that increased expression of multiple components of the mitochondrial ETC may be a primary deficit in bipolar depression, rather than an effect of medication.

Antidepressant response and the serotonin transporter gene-linked polymorphic region

BACKGROUND

The serotonin transporter gene-linked polymorphic region (5-HTTLPR) has been proposed as a predictor of antidepressant response. Insertion or deletion of a 44-base pair-long region gives rise to short "S" and long "L" forms of the promoter region, the "S" form being associated with reduced serotonin transporter expression.

METHODS

A systematic review and meta-analysis was performed to clarify the effect of 5-HTTLPR on antidepressant response and remission rates. Data were obtained from 28 studies with 5408 participants. Three genotype comparisons were tested-SS versus (SL or LL), (SS or SL) versus LL, and SS versus LL.

RESULTS

There was no statistically significant effect on antidepressant response. Compared with L carriers, there was an apparent effect of the SS genotype on remission rate (relative risk: .88; 95% confidence interval: .79-.98; p = .02). However, after trim and fill correction for missing data, the effect disappeared (relative risk: .92; 95% confidence interval: .81-1.05; p = .23), indicating that the initial significant effect was likely the result of publication bias. No significant effect on remission rate was seen for SS versus LL and SS/SL versus LL. Substantial unexplained heterogeneity of effect sizes was observed between studies, pointing to additional interacting factors contributing to an association in some cases.

CONCLUSIONS

The 5-HTTLPR biallelic short/long polymorphism by itself does not seem to usefully predict antidepressant response.

5-HT(1A) receptor binding in euthymic bipolar patients using positron emission tomography with [carbonyl-(11)C]WAY-100635

BACKGROUND

This study was undertaken to examine whether brain 5-HT(1A) receptor binding is reduced in euthymic bipolar patients.

METHODS

Eight medicated euthymic bipolar patients and 8 healthy volunteers underwent positron emission tomography scanning using the selective 5-HT(1A) receptor radioligand [carbonyl-(11)C]WAY-100635.

RESULTS

No significant difference in global postsynaptic parametric binding potential (BP(ND)) was found between euthymic bipolar patients (mean + or - SD, 4.24 + or - 0.76) and healthy volunteers (mean + or - SD, 4.34 + or - 0.86). Ninety five percent Confidence Intervals for the difference in group mean global postsynaptic BP(ND) were -0.77 to 0.97. Analysis of regional BP(ND) did not reveal regional differences between patients and healthy controls.

LIMITATIONS

The number of subjects studied was limited and all subjects were on medication.

CONCLUSIONS

In contrast to previous findings of reduced 5-HT(1A) receptor binding in untreated unipolar and bipolar depressed patients [Sargent, P.A., Kjaer, K.H., Bench, C.J., Rabiner, E.A., Messa, C., Meyer, J., Gunn, R.N., Grasby, P.M., Cowen, P.J., 2000. Brain serotonin1A receptor binding measured by positron emission tomography with [(11)C]WAY-100635: effects of depression and antidepressant treatment. Arch. Gen. Psychiatry 57, 174-180]; [Drevets, W.C., Frank, E., Price, J.C., Kupfer, D.J., Holt, D., Greer, P.J., Huang, Y., Gautier, C., Mathis, C., 1999. PET imaging of serotonin1A receptor binding in depression. Biol. Psychiatry 46, 1375-1387] and in recovered unipolar depressed patients [Bhagwagar, Z., Rabiner, E.A., Sargent, P.A., Grasby, P.M., Cowen, P.J., 2004. Persistent reduction in brain serotonin1A receptor binding in recovered depressed men measured by positron emission tomography with [(11)C]WAY-100635. Mol. Psychiatry 9, 386-92], this study found no difference in 5-HT(1A) receptor BP(ND) between medicated euthymic bipolar patients and healthy controls. Normal 5-HT(1A) receptor BP(ND) in these patients may be a result of drug treatment or could indicate that reduced 5-HT(1A) receptor binding is specific to the depressed state in bipolar patients.

Serotonin transporter polymorphisms (SLC6A4 insertion/deletion and rs25531) do not affect the availability of 5-HTT to [11C] DASB binding in the living human brain

Studies in vitro suggest that the expression of the serotonin transporter (5-HTT) is regulated by polymorphic variation in the promoter region of the 5-HTT gene (5-HTTLPR); however, results from human brain imaging studies examining the relation between 5-HTT genotype and 5-HTT radioligand binding in vivo have been inconsistent. This inconsistency could reflect small participant numbers or the use of sub-optimal radiotracer for measuring the 5-HTT. We used positron emission tomography in conjunction with the selective 5-HTT ligand [(11)C] DASB to examine the availability of the 5-HTT in seven brain regions in 63 healthy European caucasian volunteers who were genotyped for short (S) and long (L) variants (SLC6A4 and rs25531) of the 5-HTTLPR. [(11)C] DASB binding potential was not influenced by the allelic status of participants whether classified on a biallelic or triallelic basis in any of the regions studied. Our PET findings, in a relatively large sample with a near optimal radiotracer, suggest that 5-HTTLPR polymorphic variation does not affect the availability of 5-HTT to [(11)C] DASB binding in adult human brain. The reported impact of 5-HTTLPR polymorphic variation on emotional processing and vulnerability to depression are more likely therefore to be expressed through effects exerted during neurodevelopment.

A sequencing-based survey of functional APAF1 alleles in a large sample of individuals with affective illness and population controls

Rare apoptosis-promoting functional variants in the apoptosis protease activating factor 1 (APAF1) gene were recently reported to co-segregate with major depression in male members of families from Utah. In order to estimate the impact of these variants on risk for major depressive disorder (MDD) in the general population, we surveyed the frequency of the APAF1 putative MDD risk alleles using re-sequencing in a large sample of northern European and European-American subjects, including a large number of males with MDD. The E777K and N782T APAF1 variants previously described by Harlan et al. [Harlan et al. (2006) Mol Psychiatry 11(1):76-85] were found at low frequencies in affected individuals and population controls. The C450W and Q465R variants were not detected in any of the 632 subjects sequenced. These results show that the APAF1 variants associated with risk for MDD in the Utah pedigrees are very rare in Northern European and European-American populations. In addition, the E777K and N782T variants were found at low frequencies both in patients and population controls, suggesting that these variants have limited impact on risk for MDD.

Brain serotonin transporter binding in former users of MDMA ('ecstasy')

BACKGROUND

Animal experimental studies have prompted concerns that widespread use of 3,4-methylenedioxymethamphetamine (MDMA; 'ecstasy') by young people may pose a major public health problem in terms of persistent serotonin neurotoxicity.

AIMS

To determine the status of brain serotonin neurons in a group of abstinent MDMA users.

METHOD

We assessed the integrity of brain serotonin neurons by measuring serotonin transporter (SERT) binding using positron emission tomography (PET) and [(11)C]DASB in 12 former MDMA users, 9 polydrug users who had never taken MDMA and 19 controls who reported no history of illicit drug use.

RESULTS

There was no significant difference in the binding potential of [(11)C]DASB between the groups in any of the brain regions examined.

CONCLUSIONS

To the extent that [(11)C]DASB binding provides an index of the integrity of serotonin neurons, our findings suggest that MDMA use may not result in long-term damage to serotonin neurons when used recreationally in humans.

Evidence for modulation of facial emotional processing bias during emotional expression decoding by serotonergic and noradrenergic antidepressants: an event-related potential (ERP) study

RATIONALE

Serotonergic (SSRI) and noradrenergic (NRI) antidepressants modulate biases in emotional processing such that perceptual bias is shifted away from negative and towards positive emotional material. However, the effects of serotonergic and noradrenergic modulation on the temporal course (occurring in milliseconds) of emotional processing, and in particular, the rapid physiological changes associated with the different stages of emotional processing, are unknown.

OBJECTIVE

The current study assessed the effects of acute serotonergic (i.e. with citalopram) and noradrenergic (i.e. with reboxetine) augmentation on event-related potential (ERP) measures associated with 'structural encoding' (N170) and emotion expression decoding (N250 and late positive potential [LPP]) for positive (happy) and negative (sad) facial stimuli relative to neutral facial stimuli.

MATERIALS AND METHODS

This study employed a double-blind, placebo-controlled, cross-over design in which 12 healthy male participants completed a facial expression recognition task tested under three acute conditions: (a) placebo, (b) citalopram (20 mg) and (c) reboxetine (4 mg).

RESULTS

Both citalopram and reboxetine had no effect on the N170 ERP component associated with structural encoding, but potentiated the N250 associated with happy (relative to neutral) emotional facial expression decoding. Both drugs had no valence effects on later ERP measures of emotion expression decoding (LPP).

CONCLUSIONS

Citalopram and reboxetine have selective effects on the temporal course of emotional processing with evidence to suggest specific effects on emotion expression decoding of positive (happy) emotional facial stimuli as evidenced by changes in the attention-modulated N250 but not structural encoding. These findings provide physiological evidence that antidepressants may shift perceptual biases in emotional processing away from negative and towards positive stimuli.

Effects of citalopram infusion on the serotonin transporter binding of [11C]DASB in healthy controls

The positron emission tomography (PET) ligand [(11)C]DASB is currently the most widely used imaging agent for quantitative studies of the serotonin transporter (SERT) in human brain. The aim of this work was to assess the effects of an intravenous infusion of 10 mg citalopram, a selective serotonin reuptake inhibitor (SSRI), before the PET scan on the kinetics of [(11)C]DASB in arterial plasma and in selected brain regions. Four healthy male volunteers underwent two PET scans with a mean of 523 MBq injected activity after either placebo or citalopram infusion in a randomised design. The citalopram infusion led to a substantial increase of the area under the curve of the metabolite-corrected arterial plasma input function. Total volumes of distribution V(T) were estimated applying the Logan plot to regional time-activity curves or by generating parametric maps with spectral analysis. A mean reduction of the cerebellar V(T) of 19% with Logan analysis and of 24% with spectral analysis was observed after citalopram infusion, which confirms previous findings of displaceable SERT ligand binding in cerebellar grey matter. The SERT occupancy for six target regions with moderate to high binding was 60% derived from BP(ND) and 69% derived from BP(P).

Neural correlates of impulse control during stop signal inhibition in cocaine-dependent men

Altered impulse control is associated with substance use disorders, including cocaine dependence. We sought to identify the neural correlates of impulse control in abstinent male patients with cocaine dependence (PCD). Functional magnetic resonance imaging (fMRI) was conducted during a stop signal task that allowed trial-by-trial evaluation of response inhibition. Fifteen male PCD and 15 healthy control (HC) subjects, matched in age and years of education, were compared. Stop signal reaction time (SSRT) was derived on the basis of a horse race model. By comparing PCD and HC co-varied for stop success rate, task-related frustration rating, and post-error slowing, we isolated the neural substrates of response inhibition, independent of attentional monitoring (of the stop signal) and post-response processes including affective responses and error monitoring. Using region of interest analysis, we found no differences between HC and PCD who were matched in stop signal performance in the pre-supplementary motor area (pre-SMA) previously shown to be associated with SSRT. However, compared with HC, PCD demonstrated less activation of the rostral anterior cingulate cortex (rACC), an area thought to be involved in the control of stop signal inhibition. The magnitude of rACC activation also correlated negatively with the total score and the impulse control subscore of the Difficulty in Emotion Regulation Scale in PCD. The current study thus identified the neural correlates of altered impulse control in PCD independent of other cognitive processes that may influence stop signal performance. Relative hypoactivation of the rACC during response inhibition may represent a useful neural marker of difficulties in impulse control in abstinent cocaine-dependent men who are at risk of relapse.

Low GABA concentrations in occipital cortex and anterior cingulate cortex in medication-free, recovered depressed patients

Studies using proton magnetic resonance spectroscopy (1H-MRS) indicate that unmedicated, acutely depressed patients have decreased levels of gamma-aminobutyric acid (GABA) in the occipital cortex. The aim of this study was to use 1H-MRS to determine if changes in occipital and frontal cortical GABA levels were present in patients with a history of depression who had recovered and were no longer taking medication. We used 1H-MRS to measure levels of GABA in both occipital cortex and anterior cingulate cortex/prefrontal cortex in medication-free, fully recovered subjects with a history of recurrent unipolar depression. Levels of GABA in both occipital and anterior cingulate cortex were significantly lower in recovered depressed subjects than healthy controls. Our data provide preliminary evidence that a history of recurrent depression is associated with decreased GABA levels in anterior cingulate cortex and occipital cortex. These changes could represent part of the neurobiological vulnerability to recurrent depressive episodes.

'It's not over when it's over': persistent neurobiological abnormalities in recovered depressed patients

The tendency of major depression to recur is a leading problem in clinical management and is responsible for much of the illness burden. Until recently, biological studies of depression have focused on the mechanisms involved in acute illness but there are now many data to suggest that neurobiological abnormalities persist when depressed patients are clinically recovered and withdrawn from medication. These abnormalities encompass a number of neurochemical and neuropsychological mechanisms that could be relevant to recurrence, including changes in the availability of serotonin (5-hydroxytryptamine, 5-HT) receptor subtypes, decreases in cortical gamma-aminobutyric acid (GABA), increases in cortisol secretion and negative biases in the processing of emotional information. Studies of groups at high risk of depression before illness onset will help to clarify which biological abnormalities precede the development of depression and which are the product of recurrent illness. Ultimately this work should lead to a better understanding of the neurobiology of vulnerability to depression and more innovative approaches to primary and secondary prevention.