Noradrenergic dysfunction in the prefrontal cortex in depression: an [15O] H2O PET study of the neuromodulatory effects of clonidine

Effects of physical activity in child and adolescent depression and anxiety: role of inflammatory cytokines and stress-related peptide hormones

Depression and anxiety are the most common mental illnesses affecting children and adolescents, significantly harming their well-being. Research has shown that regular physical activity can promote cognitive, emotional, fundamental movement skills, and motor coordination, as a preventative measure for depression while reducing the suicide rate. However, little is known about the potential role of physical activity in adolescent depression and anxiety. The studies reviewed in this paper suggest that exercise can be an effective adjunctive treatment to improve depressive and anxiety symptoms in adolescents, although research on its neurobiological effects remains limited.

Modeling [11C]yohimbine PET human brain kinetics with test-retest reliability, competition sensitivity studies and search for a suitable reference region

Previous work introduced the [¹¹C]yohimbine as a suitable ligand of central α2-adrenoreceptors (α2-ARs) for PET imaging. However, reproducibility of [¹¹C]yohimbine PET measurements in healthy humans estimated with a simplified modeling method with reference region, as well as sensitivity of [¹¹C]yohimbine to noradrenergic competition were not evaluated. The objectives of the present study were therefore to fill this gap.

METHODS

Thirteen healthy humans underwent two [¹¹C]yohimbine 90-minute dynamic scans performed on a PET-MRI scanner. Seven had arterial blood sampling with metabolite assessment and plasmatic yohimbine free fraction evaluation at the first scan to have arterial input function and test appropriate kinetic modeling. The second scan was a simple retest for 6 subjects to evaluate the test-retest reproducibility. For the remaining 7 subjects the second scan was a challenge study with the administration of a single oral dose of 150 µg of clonidine 90 min before the PET scan. Parametric images of α2-ARs distribution volume ratios (DVR) were generated with two non-invasive models: Logan graphical analysis with Reference (LREF) and Simplified Reference Tissue Method (SRTM). Three reference regions (cerebellum white matter (CERWM), frontal white matter (FLWM), and corpus callosum (CC)) were tested.

RESULTS

We showed high test-retest reproducibility of DVR estimation with LREF and SRTM regardless of reference region (CC, CERWM, FLWM). The best fit was obtained with SRTM_CC (r²=0.94). Test-retest showed that the SRTM_CC is highly reproducible (mean ICC>0.7), with a slight bias (-1.8%), whereas SRTM_CERWM had lower bias (-0.1%), and excellent ICC (mean>0.8). Using SRTM_CC, regional changes have been observed after clonidine administration with a significant increase reported in the amygdala and striatum as well as in several posterior cortical areas as revealed with the voxel-based analysis.

CONCLUSION

The results add experimental support for the suitability of [¹¹C]yohimbine PET in the quantitative assessment of α2-ARs occupancy in vivo in the human brain. Trial registration EudraCT 2018-000380-82.

Widespread Morphometric Abnormalities in Major Depression: Neuroplasticity and Potential for Biomarker Development

Major depression is common and debilitating. Identifying neurobiological subtypes that comprise the disorder and predict clinical outcome are key challenges. Genetic and environmental factors leading to major depression are expressed in neural structure and function. Volumetric decreases in gray matter have been demonstrated in corticolimbic circuits involved in emotion regulation. MR imaging observable abnormalities reflect cytoarchitectonic alterations within a local neuroendocrine milieu with systemic effects. Multivariate pattern analysis offers the potential to identify the neurobiological subtypes and predictors of clinical outcome. It is essential to characterize disease heterogeneity by incorporating data-driven inductive and symptom-based deductive approaches in an iterative process.

Multimodal functional and structural neuroimaging investigation of major depressive disorder following treatment with duloxetine

BACKGROUND

Longitudinal neuroimaging studies of major depressive disorder (MDD) have most commonly assessed the effects of antidepressants from the serotonin reuptake inhibitor class and usually reporting a single measure. Multimodal neuroimaging assessments were acquired from MDD patients during an acute depressive episode with serial measures during a 12-week treatment with the serotonin-norepinephrine reuptake inhibitor (SNRI) duloxetine.

METHODS

Participants were medication-free MDD patients (n = 32; mean age 40.2 years) in an acute depressive episode and healthy controls matched for age, gender, and IQ (n = 25; mean age 38.8 years). MDD patients received treatment with duloxetine 60 mg daily for 12 weeks with an optional dose increase to 120 mg daily after 8 weeks. All participants had serial imaging at weeks 0, 1, 8, and 12 on a 3 Tesla magnetic resonance imaging (MRI) scanner. Neuroimaging tasks included emotional facial processing, negative attentional bias (emotional Stroop), resting state functional MRI and structural MRI.

RESULTS

A significant group by time interaction was identified in the anterior default mode network in which MDD patients showed increased connectivity with treatment, while there were no significant changes in healthy participants. In the emotional Stroop task, increased posterior cingulate activation in MDD patients normalized following treatment. No significant group by time effects were observed for happy or sad facial processing, including in amygdala responsiveness, or in regional cerebral volumes. Reduced baseline resting state connectivity within the orbitofrontal component of the default mode network was predictive of clinical response. An early increase in hippocampal volume was predictive of clinical response.

CONCLUSIONS

Baseline resting state functional connectivity was predictive of subsequent clinical response. Complementary effects of treatment were observed from the functional neuroimaging correlates of affective facial expressions, negative attentional bias, and resting state. No significant effects were observed in affective facial processing, while the interaction effect in negative attentional bias and individual group effects in resting state connectivity could be related to the SNRI class of antidepressant medication. The specificity of the observed effects to SNRI pharmacological treatments requires further investigation.

TRIAL REGISTRATION

Registered at clinicaltrials.gov ( NCT01051466 ).

Noradrenergic modulation of cognition: therapeutic implications

The noradrenaline (norepinephrine) system exerts profound influences on cognition via ascending projections to the forebrain, mostly originating from the locus coeruleus. This paper provides an overview of available infrahuman and healthy human studies, exploring the effects of specific noradrenergic manipulations on dissociable cognitive functions, including attention, working memory, cognitive flexibility, response inhibition and emotional memory. Remarkable parallels across species have been reported which may account for the mechanisms by which noradrenergic medications exert their beneficial effects in disorders such as depression and attention-deficit hyperactivity disorder (ADHD). The literature is discussed in relation to prevailing models of noradrenergic influences over cognition and novel therapeutic directions, including in relation to investigating the effects of noradrenergic manipulations on other disorders characterized by impulsivity, and dementias. Unanswered questions are also highlighted, along with key avenues for future research, both proof-of-concept and clinical.

Central noradrenergic responsiveness to a clonidine challenge in Generalized Anxiety Disorder: a Single Photon Emission Computed Tomography study

Generalized Anxiety Disorder (GAD) may involve hypo-responsiveness of noradrenaline a2 receptors. To test this hypothesis, we used (99m)Tc-hexa-methyl-propylene-amine-oxime (HMPAO) Single Photon Emission Computed Tomography to measure regional cerebral perfusion in patients with untreated GAD, venlafaxine-treated patients and healthy controls during word generation before and after clonidine. Concurrent psychological and physiological measures supported noradrenergic hypofunction in GAD in some cases. A single-day split-dose technique was used. Images were processed using SPM5 (Institute of Neurology). Factorial analysis revealed no significant results. Exploratory analyses were done. Regional perfusion during verbal fluency differed by group pre-clonidine. Compared with healthy controls, patients with untreated GAD displayed increased perfusion in the left Broca's area and left occipitotemporal region. Treated GAD patients displayed increased cerebellar perfusion bilaterally. Clonidine was associated with different changes in cerebral perfusion in each group. Increases were seen in the right supra-marginal gyrus in healthy subjects, in the left pre-central gyrus in treated GAD patients and in the right cerebellum and middle frontal gyrus in untreated GAD patients. Despite these differences, the findings were not consistent with a noradrenergic hypo-responsiveness hypothesis, as the treated group showed a different pattern of response rather than a normalization of response.

Differential modulation of α-1 adrenoceptor subtypes by antidepressants in the rat brain

The aim of the present study was to examine the effect of chronic antidepressants treatment on the density of α₁-adrenoceptor (AR) subtypes in rat brain. Density of total α₁ and α(1A)- and α(1Β)-ARs was measured in cortex and cerebellum of rats treated with amitriptyline (AMI), desipramine (DMI) and fluoxetine (FLX), (10 mg/kg body wt), for 30 days, using [³H]prazosin in presence and absence of WB-4101. The density of cortical total α₁-ARs was significantly decreased with AMI (54%) and DMI (25%) treatment, without altering the affinity of the receptor. Fluoxetine did not alter the density of cortical α₁-ARs. The density of cortical α(1A)-ARs was also significantly decreased with AMI (85%) and DMI (50%) treatment, without affecting the affinity. The density of cerebellar total α₁-ARs was significantly decreased with AMI (37%), DMI (50%) and FLX (70%) treatment, without affecting the affinity for [³H]prazosin. The density of α(1A)-ARs was significantly decreased with AMI (67%), DMI (59%) and FLX (92%) treatment. α(1B)-AR density was decreased only with FLX (47%) and DMI (47%) treatment. Correspondingly the basal IP3 and NE (10 μM) stimulated IP3 levels were significantly decreased in AMI (47%), DMI (22%) and FLX (48%) treated rat cortex. The results suggest that chronic antidepressant (AD) treatment down-regulates the cortical and cerebellar total α₁-ARs in rat brain. However, α(1A) subtype is predominantly down-regulated by AMI and DMI, where as FLX affects cerebellar α(1A)-ARs. The region-specific and subtype specific down-regulation of α₁-ARs density, which occurs after prolonged AD treatment, may underline the therapeutic mechanism of action.

α₂-Adrenoceptor functionality in postmortem frontal cortex of depressed suicide victims

BACKGROUND

Alterations in brain density and signaling associated with monoamine receptors are believed to play a role in depressive disorders. This study evaluates the functional status of α₂(A)-adrenoceptors in postmortem frontal cortex of depressed subjects.

METHODS

G-protein activation and inhibition of adenylyl cyclase (AC) activity induced by the α₂-adrenoceptor agonist UK14304 were measured in triplicate in samples from 15 suicide victims with an antemortem diagnosis of major depression and 15 matched control subjects.

RESULTS

Basal [³⁵S] guanosine γ thio-phosphate (GTPγS) binding and cyclic adenosine monophosphate accumulation did not differ between groups. In depressed victims, an increase in [³⁵S] GTPγS binding potency (EC₅₀ = .58 μmol/L vs. EC₅₀ = 3.31 μmol/L; p < .01; depressed vs. control) and a significant reduction in the maximal inhibition of AC activity (I(max) = 27 ± 4% vs. I(max) = 47 ± 5%; p < .01) were observed after incubation with the α(2)-adrenoceptor agonist UK14304. No differences were found between antidepressant-free and antidepressant-treated subjects. A significant relationship between EC₅₀ values for [³⁵S] GTPγS and I(max) values for AC assay was found (n = 30; r = -.43; p < .05).

CONCLUSIONS

The dual regulation of α(2A)-adrenoceptor signaling pathways raises the possibility that factors affecting the G-protein cycle and/or selective access of Gα(i/o)-protein to AC might be relevant to receptor abnormalities in depression, providing further support for the involvement of α₂(A)-adrenoceptors in the pathogenesis of depression.

Reduced platelet G protein-coupled receptor kinase 2 in major depressive disorder: antidepressant treatment-induced upregulation of GRK2 protein discriminates between responder and non-responder patients

The homologous regulation of neurotransmitter receptors by G protein-coupled receptor kinases (GRKs) is important in the pathogenesis and treatment of major depressive disorder (MDD). Previous studies have reported that the basal status of GRK2 is different in brains (upregulation) and platelets (downregulation) of subjects with MDD. The principal aim of this study was to re-examine the status of platelet membrane GRK2 protein in patients with MDD, along with GRK3 (a close kinase homolog) and GRK5 (a kinase with different properties), before and after treatment with serotonin-selective reuptake inhibitor (SSRI) or serotonin noradrenaline reuptake inhibitor (SNRI) antidepressants. The main findings indicated that platelet GRK2 and p-Ser670 GRK2 were reduced (36-41%) in unmedicated MDD subjects, and that GRK2 content correlated inversely with the severity of depression (r=-0.51). Effective antidepressant treatments normalized platelet GRK2, and, notably, GRK2 upregulation discriminated between responder and non-responder patients. Other findings revealed a modest reduction of platelet GRK3 (23%) and no alteration of platelet GRK5 content. In untreated subjects with MDD, lymphocyte GRK2 and GRK5 mRNAs were unaltered but antidepressant treatment-induced upregulation of GRK2 mRNA expression. The reduced content of platelet GRK2 protein is a relevant target in MDD. Although this peripheral GRK2 defect does not mirror the canonical regulation of brain GRK2 in depressed suicides, it could well represent a disease state marker as well as a surrogate of response to effective antidepressant treatment.

Noradrenergic function in pathological gambling: blunted growth hormone response to clonidine

The noradrenergic system has been linked to impulsive behaviour in animals and humans, yet little data on noradrenergic system exist in specific impulse control disorders. To explore the role of the noradrenergic system in pathological gamblers (PG), we assessed neuroendocrine growth hormone (GH) response to the alpha2-adrenergic receptor agonist clonidine and placebo in PG and controls. The net effects of clonidine are a decrease in neurotransmission by depressing locus coeruleus activity and stimulation of GH secretion through activation of post-synaptic alpha2-adrenergic receptors in the hypothalamus. Twenty-nine PG subjects, free of other comorbid conditions, and 27 healthy controls received a double-blinded, placebo-controlled, single dose of oral clonidine (0.15 mg/kg). Data observed included GH, clonidine levels and levels of the main noradrenergic metabolite, 3-methoxy-4-hydroxy-phenylglycol (MHPG). The area under the curve for GH response to clonidine was significantly lower (separate variance t with 44.3 df = 2.626, P = 0.012, d = 0.58) in the PG group (199.6) than in the control group (426.3). PG had significantly blunted GH responses compared with controls at 120 and 150 min post-clonidine. These results are consistent with the idea that the subsensitivity of post-synaptic alpha-2 receptors is possibly attributable to higher-than-normal noradrenergic secretion in PG. This peripheral noradrenergic dysfunction could be consistent with attenuated cortico-frontal noradrenergic function as shown in positron emission tomography (PET) studies of PG.

The importance of functional impairment to mental health outcomes: a case for reassessing our goals in depression treatment research

Outcomes in depression treatment research include both changes in symptom severity and functional impairment. Symptom measures tend to be the standard outcome but we argue that there are benefits to considering functional outcomes. An exhaustive literature review shows that the relationship between symptoms and functioning remains unexpectedly weak and often bidirectional. Changes in functioning often lag symptom changes. As a result, functional outcomes might offer depression researchers more critical feedback and better guidance when studying depression treatment outcomes. The paper presents a case for the necessity of both functional and symptom outcomes in depression treatment research by addressing three aims-1) review the research relating symptoms and functioning, 2) provide a rationale for measuring both outcomes, and 3) discuss potential artifacts in measuring functional outcomes. The three aims are supported by an empirical review of the treatment outcome and epidemiological literatures.

The alpha 2A-adrenergic receptor gene polymorphism modifies antidepressant responses to milnacipran

OBJECTIVE

The alpha 2A-adrenergic receptor (ADRA2A) plays a central role in the regulation of systemic sympathetic activity. Recently, the functional defect of ADRA2A has been implicated as a cause of depression, attention deficit hyperactivity disorder, and Tourette syndrome. In this study, the effect of genetic variants of the ADRA2A gene on the response to selective serotonin reuptake inhibitors (SSRIs)/serotonin norepinephrine reuptake inhibitors (SNRIs) was examined in depressed patients.

METHOD

Ninety-three Japanese depressed patients were recruited in the present study, assigned randomly to paroxetine or milnacipran, and assessed by the Hamilton Rating Scale for Depression (HAM-D) scoring every 2 weeks before and after drug administration. The ADRA2A C-1297G polymorphism was considered in the association analysis with the efficacy of antidepressants.

RESULTS

There were significant differences in the HAM-D percent score change over time (P = 0.019) among C/C, C/G, and G/G of the ADRA2A C-1297G polymorphism in the total subjects. The C allele carriers of the ADRA2A C-1297G polymorphism showed a significantly better improvement than G/G subjects at weeks 2, 4, and over time (P = 0.037) in the milnacipran group.

DISCUSSION

Our findings suggest that ADRA2A plays an important role in depression therapy. The level of ADRA2A expression could be associated with the efficacy of SSRIs/SNRIs, especially milnacipran, although the functional change brought about by C-1297G polymorphism has not yet been fully identified in vivo and in vitro.

CONCLUSIONS

The ADRA2A polymorphism could be a reasonable candidate to predict the response to milnacipran. Our results are still preliminary, and a large sample size will be required to confirm our findings. However, to the best of our knowledge, this study is the first to suggest a possible association of ADRA2A variants with the SNRI response.

Platelet imidazoline receptors as state marker of depressive symptomatology

OBJECTIVE

Previous studies have shown that imidazoline receptors (IR-1) are increased in platelets and frontal cortex of depressed patients, and this up-regulation is normalized (down-regulated) after antidepressant drug treatments. It has been hypothesized that IR-1 up-regulation during the depressive episode may be a state marker for depressive symptomatology. The goal of the present study was to address the state versus trait question.

METHOD

Twelve healthy subjects (six males and six females) met stringent inclusion and exclusion criteria for physical and mental health. They received desipramine for 6 weeks in order to simulate the length of time and dosing used previously to obtain an IR-1 down-regulation and a therapeutic response in depressed patients. Outcome and safety measures included clinical, psychological, and cardiovascular assessments obtained throughout the study. Plasma concentrations of desipramine were measured throughout the 6 weeks of treatment and again after 2 weeks following tapered discontinuation of desipramine. Platelet receptors were assessed by Western blotting and radioligand binding assays.

RESULTS

Healthy subjects taking desipramine experienced mild dysphoric effects but there were no adverse events. The binding of 8 nM p-[(125)I]clonidine to IR-1 and alpha(2)-adrenoceptors in healthy subjects did not change during desipramine treatment. The immunodensity of the 33 kDa band associated with IR-1 gradually increased to a maximum, by week-6, of 26% higher than baseline (p < 0.01 compared to baseline). Two weeks after desipramine discontinuation, there was a decline in alpha(2)-adrenoceptor binding and 33 kDa band's immunodensity (p = 0.04).

CONCLUSIONS

The findings support the hypothesis that platelet IR-1 binding sites are a marker of mood state rather than of antidepressant-induced pharmacological regulation. By comparison, platelet alpha(2)-adrenoceptors appear to be regulated by desipramine as a pharmacological effect independent of mood state.

Prefrontal cortical functional abnormality in major depressive disorder: a stereotactic meta-analysis

OBJECTIVE

First, the objective was to test the hypothesis that prefrontal cortical regions most often reported to be maximally abnormal in studies of major depressive disorder, correspond to those regions reported maximally active when healthy subjects engage in diverse emotional tasks. Second, the objective was to determine whether such regions are reported typically to be either over or under-active.

METHOD

Medline and Embase were used to search for neuroimaging studies of major depressive disorder from 1990 to 2005. Forty-two original studies using voxel based techniques were included, and compared with data from our previous meta-analysis on healthy subjects which included one hundred and eighty-one original studies [Steele, J.D., Lawrie, S.M., 2004b. Segregation of cognitive and emotional function in the prefrontal cortex: a stereotactic meta-analysis. Neuroimage 21, 868-875].

RESULTS

The medial prefrontal cortex is the region reported maximally abnormal most often when healthy subjects experience emotion. The region is centred on Broadmans Area (BA) 32 but extends into BA 25. Two further clusters of reported loci were identified in the lateral prefrontal cortex: one in the lateral orbitofrontal region reported active when healthy subjects experience emotion (BA 47); the other centred on a dorsolateral region (BA 46 and 9) associated with cognitive tasks. No reporting bias for overactivity or underactivity was identified.

LIMITATIONS

This study pooled data from diverse studies deliberately. There were insufficient numbers of original studies to support sub-group analyses.

CONCLUSIONS

Despite the variability of reports in the literature, activity reported to be abnormal in depressive disorder is particularly localised to those brain regions that represent the substrate for normal emotional experience in healthy subjects.

An analysis of functional neuroimaging studies of dorsolateral prefrontal cortical activity in depression

Repetitive transcranial magnetic stimulation (rTMS) is currently undergoing active investigation for use in the treatment of major depression. Recent research has indicated that current methods used to localize the site of stimulation in dorsolateral prefrontal cortex (DLPFC) are significantly inaccurate. However, little information is available on which to base a choice of stimulation site. The aim of the current study was to systematically examine imaging studies in depression to attempt to identify whether there is a pattern of imaging results that suggests an optimal site of stimulation localization. We analysed all imaging studies published prior to 2005 that examined patients with major depression. Studies reporting activation in DLPFC were identified. The DLPFC regions identified in these studies were analysed using the Talairach and Rajkowska-Goldman-Rakic coordinate systems. In addition, we conducted a quantitative meta-analysis of resting studies and studies of serotonin reuptake inhibitor antidepressant treatment. There was considerable heterogeneity in the results between studies. Changes in Brodmann area 9 were relatively consistently identified in resting, cognitive activation and treatment studies included in the meta-analysis. However, there was little consistency in the direction of these changes or the hemisphere in which they were identified. At this stage, the results of imaging studies published to date have limited capacity to inform the choice of optimal prefrontal cortical region for the use in rTMS treatment studies.

Anxious and depressive disorders and their comorbidity: effect on central nervous system noradrenergic function

BACKGROUND

Although comorbidity of anxiety with depression is common, investigations of physiologic abnormalities related specifically to comorbidity are rare. This study examined relationships of DSM-IV-defined depression, anxiety, and their comorbidity to noradrenergic function measured by blunting of the growth hormone (GH) response to the alpha2 adrenoreceptor agonist (and imidazoline receptor agent) clonidine and by blood pressure and symptom responses.

METHODS

Fifteen subjects with pure social anxiety or panic disorder, 15 with pure major depression, and 18 with both depression and anxiety were compared with healthy control subjects matched for age and gender. Other factors known to affect GH (weight, menstrual status, prior antidepressant, or other drug exposure) were controlled.

RESULTS

Anxiety produced GH blunting, but depression was associated with normal GH responses. The comorbid state did not affect results beyond the impact of anxiety. Preclonidine stress-related GH elevations were observed, to the greatest degree in anxious subjects. Relevant symptom, but not blood pressure, changes were significantly associated with blunting.

CONCLUSIONS

With use of pure depression and anxiety groups and careful control of other factors known to affect GH, these results demonstrate central nervous system noradrenergic dysfunction in anxiety disorders. In contrast to less rigorously controlled studies, noradrenergic function in depression was normal.

Regulation of platelet alpha 2A-adrenoceptors, Gi proteins and receptor kinases in major depression: effects of mirtazapine treatment

Major depression is associated with the upregulation of alpha(2A)-adrenoceptors in brain tissue and blood platelets. The homologous regulation of these receptors by G-protein-coupled receptor kinases (GRKs) might play a relevant role in the pathogenesis and treatment of depression. This study was designed to assess the status of the complex alpha(2A)-adrenoceptor/Galphai/GRK 2 in the platelets of depressed patients (n=22) before and after treatment with the antidepressant mirtazapine, an antagonist at alpha(2A)-adrenoceptors (30-45 mg/day for up to 6 months). A second series of depressed suicide attempters (n=32) were also investigated to further assess the status of platelet GRK 2 and GRK 6. Platelet alpha(2A)-adrenoceptors and Galphai protein immunoreactivities were increased in depressed patients (49 and 35%) compared with matched controls. In contrast, GRK 2 content was decreased in the two series of depressed patients (27 and 28%). GRK 6 (a GRK with different properties) was found unchanged. In drug-free depressed patients, the severity of depression (behavioral ratings with two different instruments) correlated inversely with the content of platelet GRK 2 (r=-0.46, n=22, p=0.032, and r=-0.55, n=22, p=0.009). After 4-24 weeks of treatment, mirtazapine induced downregulation of platelet alpha(2A)-adrenoceptors (up to 34%) and Galphai proteins (up to 28%), and the upregulation of GRK 2 (up to 30%). The results indicate that major depression is associated with reduced platelet GRK 2, suggesting that a defect of this kinase may contribute to the observed upregulation of alpha(2A)-adrenoceptors. Moreover, treatment with mirtazapine reversed this abnormality and induced downregulation of alpha(2A)-adrenoceptor/Galphai complex. The results support a role of supersensitive alpha(2A)-adrenoceptors in the pathogenesis and treatment of major depression.

Anatomic evaluation of the orbitofrontal cortex in major depressive disorder

BACKGROUND

The orbitofrontal cortex (OFC) plays a major role in neuropsychologic functioning including exteroceptive and interoceptive information coding, reward-guided behavior, impulse control, and mood regulation. This study examined the OFC and its subdivisions in patients with MDD and matched healthy control subjects.

METHODS

Magnetic resonance imaging (MRI) was performed on 31 unmedicated MDD and 34 control subjects matched for age, gender, and race. Gray matter volumes of the OFC and its lateral and medial subdivisions were measured blindly.

RESULTS

The MDD patients had smaller gray matter volumes in right medial [two-way analysis of covariance F(1,60) = 4.285; p =.043] and left lateral OFC [F(1,60) = 4.252; p =.044]. Left lateral OFC volume correlated negatively with age in patients but not in control subjects. Male, but not female patients exhibited smaller left and right medial OFC volumes compared with healthy control subjects of the same gender.

CONCLUSIONS

These findings suggest that patients with MDD have reduced OFC gray matter volumes. Although this reduction might be important in understanding the pathophysiology of MDD, its functional and psychopathologic consequences are as yet unclear. Future studies examining the relationship between specific symptomatic dimensions of MDD and OFC volumes could be especially informative.

Cortical alpha-adrenoceptor downregulation by tricyclic antidepressants in the rat brain

The aim of the present study was to examine the effect of chronic tricyclic antidepressants (TCAs) treatment on the density of alpha-adrenoceptors in the rat brain. Density of alpha1- and alpha2-adrenoceptors was measured in cortex and hippocampus of rats treated with imipramine (IMI, 5mg/kg body weight), desipramine (DMI, 10mg/kg body weight), clomipramine (CMI, 10mg/kg body weight) and amitriptyline (AMI, 10mg/kg body weight), for 40 days, using [3H]prazosin and [3H]clonidine, respectively. The density of cortical alpha1-adrenoceptors was significantly decreased with IMI (46%), DMI (21%), CMI (50%) and AMI (67%) treatment, without altering the affinity of the receptor. The density of cortical alpha2-adrenoceptors was also significantly decreased with DMI (69%), CMI (81%) and AMI (80%) treatment, without affecting the affinity for [3H]clonidine. The density of hippocampal alpha1-adrenoceptors was significantly decreased only with AMI treatment (47%), without affecting the affinity for [3H]prazosin. However, no change in hippocampal alpha2-adrenoceptor density was observed with any of these TCAs. The results suggest that chronic antidepressant (AD) treatment downregulates the cortical, but not hippocampal, alpha1- and alpha2-adrenoceptors in rat brain. The region-specific downregulation of alpha1- and alpha2-adrenoceptors density, which occur after prolonged AD treatment, may underline the therapeutic mechanism of action.

Differential expression of alpha2-adrenoceptor vs. imidazoline binding sites in postmortem orbitofrontal cortex and amygdala of depressed subjects

Clonidine is a well established antihypertensive agent that is also used effectively to treat a variety of psychiatric disorders. Clonidine is a prototypic imidazoline compound that acts as an alpha(2)-adrenergic agonist but possesses nearly equivalent affinity for non-adrenergic imidazoline binding sites (I-sites). Receptor autoradiography of [(3)H]-clonidine binding presented herein compares densities of alpha(2)-adrenoceptors and I-sites (under a noradrenergic-mask) in Brodmann's area 47 of the left orbitofrontal cortex (OFC) and in six amygdaloid nuclei of subjects with major depression (n=12) vs. controls with no psychiatric history (n=11). Postmortem diagnoses were made from psychiatric interviews with next-of-kin. [(3)H]-Clonidine binding to alpha(2)-adrenoceptors in each of six OFC layers was lower, although not reaching statistical significance in any one layer by multivariate analysis, in depressives vs. control subjects. Binding to I-sites was conversely higher in depressives compared to control OFC layers, but did not reach statistical significance alone. However, the ratios of alpha(2)-adrenoceptor : I-sites in all six layers of OFC of depressed subjects were nearly half that of control subjects (P<0.008). In amygdalas from a different group of depressed patients there were no changes in alpha(2)-adrenoceptors or I-sites, or their ratios, compared with controls. The results support previous western blot data indicating a cortex-selective shift away from alpha(2)AR towards I-site preponderance in depressed patients.

Neurotransmitter receptor-mediated activation of G-proteins in brains of suicide victims with mood disorders: selective supersensitivity of alpha(2A)-adrenoceptors

Abnormalities in the density of neuroreceptors that regulate norepinephrine and serotonin release have been repeatedly reported in brains of suicide victims with mood disorders. Recently, the modulation of the [(35)S]GTPgammaS binding to G-proteins has been introduced as a suitable measure of receptor activity in postmortem human brain. The present study sought to evaluate the function of several G-protein coupled receptors in postmortem brain of suicide victims with mood disorders. Concentration-response curves of the [(35)S]GTPgammaS binding stimulation by selective agonists of alpha(2)-adrenoceptors, 5-HT(1A) serotonin, mu-opioid, GABA(B), and cholinergic muscarinic receptors were performed in frontal cortical membranes from 28 suicide victims with major depression or bipolar disorder and 28 subjects who were matched for gender, age and postmortem delay. The receptor-independent [(35)S]GTPgammaS binding stimulation by mastoparan and the G-protein density were also examined. The alpha(2A)-adrenoceptor-mediated stimulation of [(35)S]GTPgammaS binding with the agonist UK14304 displayed a 4.6-fold greater sensitivity in suicide victims than in controls, without changes in the maximal stimulation. No significant differences were found in parameters of 5-HT(1A) serotonin receptor and other receptor-mediated [(35)S]GTPgammaS binding stimulations. The receptor-independent activation of G-proteins was similar in both groups. Immunoreactive densities of G(alphai1/2)-, G(alphai3)-, G(alphao)-, and G(alphas)-proteins did not differ between suicide victims and controls. In conclusion, alpha(2A)-adrenoceptor sensitivity is increased in the frontal cortex of suicide victims with mood disorders. This receptor supersensitivity is not related to an increased amount or enhanced intrinsic activity of G-proteins. The new finding provides functional support to the involvement of alpha(2)-adrenoceptors in the pathogenesis of mood disorders.