Molecular analyses of circadian gene variants reveal sex-dependent links between depression and clocks.

An extensive literature links circadian irregularities and/or sleep abnormalities to mood disorders. Despite the strong genetic component underlying many mood disorders, however, previous genetic associations between circadian clock gene variants and major depressive disorder (MDD) have been weak. We applied a combined molecular/functional and genetic association approach to circadian gene polymorphisms in sex-stratified populations of control subjects and case subjects suffering from MDD. This approach identified significant sex-dependent associations of common variants of the circadian clock genes hClock, hPer3 and hNpas2 with major depression and demonstrated functional effects of these polymorphisms on the expression or activity of the hCLOCK and hPER3 proteins, respectively. In addition, hCLOCK expression is affected by glucocorticoids, consistent with the sex-dependency of the genetic associations and the modulation of glucocorticoid-mediated stress response, providing a mechanism by which the circadian clock controls outputs that may affect psychiatric disorders. We conclude that genetic polymorphisms in circadian genes (especially hClock and hPer3, where functional assays could be tested) influence risk of developing depression in a sex- and stress-dependent manner. These studies support a genetic connection between circadian disruption and mood disorders, and confirm a key connection between circadian gene variation and major depression.

Obesity, but not metabolic syndrome, negatively affects outcome in bipolar disorder.

OBJECTIVE: Examine the effects of obesity and metabolic syndrome on outcome in bipolar disorder. METHOD: The Comparative Effectiveness of a Second Generation Antipsychotic Mood Stabilizer and a Classic Mood Stabilizer for Bipolar Disorder (Bipolar CHOICE) study randomized 482 participants with bipolar disorder in a 6-month trial comparing lithium- and quetiapine-based treatment. Baseline variables were compared between groups with and without obesity, with and without abdominal obesity, and with and without metabolic syndrome respectively. The effects of baseline obesity, abdominal obesity, and metabolic syndrome on outcomes were examined using mixed effects linear regression models. RESULTS: At baseline, 44.4% of participants had obesity, 48.0% had abdominal obesity, and 27.3% had metabolic syndrome; neither obesity, nor abdominal obesity, nor metabolic syndrome were associated with increased global severity, mood symptoms, or suicidality, or with poorer functioning or life satisfaction. Treatment groups did not differ on prevalence of obesity, abdominal obesity, or metabolic syndrome. By contrast, among the entire cohort, obesity was associated with less global improvement and less improvement in total mood and depressive symptoms, suicidality, functioning, and life satisfaction after 6 months of treatment. Abdominal obesity was associated with similar findings. Metabolic syndrome had no effect on outcome. CONCLUSION: Obesity and abdominal obesity, but not metabolic syndrome, were associated with less improvement after 6 months of lithium- or quetiapine-based treatment.

Fibroblasts from patients with major depressive disorder show distinct transcriptional response to metabolic stressors.

Major depressive disorder (MDD) is increasingly viewed as interplay of environmental stressors and genetic predisposition, and recent data suggest that the disease affects not only the brain, but the entire body. As a result, we aimed at determining whether patients with major depression have aberrant molecular responses to stress in peripheral tissues. We examined the effects of two metabolic stressors, galactose (GAL) or reduced lipids (RL), on the transcriptome and miRNome of human fibroblasts from 16 pairs of patients with MDD and matched healthy controls (CNTR). Our results demonstrate that both MDD and CNTR fibroblasts had a robust molecular response to GAL and RL challenges. Most importantly, a significant part (messenger RNAs (mRNAs): 26-33%; microRNAs (miRNAs): 81-90%) of the molecular response was only observed in MDD, but not in CNTR fibroblasts. The applied metabolic challenges uncovered mRNA and miRNA signatures, identifying responses to each stressor characteristic for the MDD fibroblasts. The distinct responses of MDD fibroblasts to GAL and RL revealed an aberrant engagement of molecular pathways, such as apoptosis, regulation of cell cycle, cell migration, metabolic control and energy production. In conclusion, the metabolic challenges evoked by GAL or RL in dermal fibroblasts exposed adaptive dysfunctions on mRNA and miRNA levels that are characteristic for MDD. This finding underscores the need to challenge biological systems to bring out disease-specific deficits, which otherwise might remain hidden under resting conditions.

Assessment of a multi-assay, serum-based biological diagnostic test for major depressive disorder: a pilot and replication study.

Despite decades of intensive research, the development of a diagnostic test for major depressive disorder (MDD) had proven to be a formidable and elusive task, with all individual marker-based approaches yielding insufficient sensitivity and specificity for clinical use. In the present work, we examined the diagnostic performance of a multi-assay, serum-based test in two independent samples of patients with MDD. Serum levels of nine biomarkers (alpha1 antitrypsin, apolipoprotein CIII, brain-derived neurotrophic factor, cortisol, epidermal growth factor, myeloperoxidase, prolactin, resistin and soluble tumor necrosis factor alpha receptor type II) in peripheral blood were measured in two samples of MDD patients, and one of the non-depressed control subjects. Biomarkers measured were agreed upon a priori, and were selected on the basis of previous exploratory analyses in separate patient/control samples. Individual assay values were combined mathematically to yield an MDDScore. A 'positive' test, (consistent with the presence of MDD) was defined as an MDDScore of 50 or greater. For the Pilot Study, 36 MDD patients were recruited along with 43 non-depressed subjects. In this sample, the test demonstrated a sensitivity and specificity of 91.7% and 81.3%, respectively, in differentiating between the two groups. The Replication Study involved 34 MDD subjects, and yielded nearly identical sensitivity and specificity (91.1% and 81%, respectively). The results of the present study suggest that this test can differentiate MDD subjects from non-depressed controls with adequate sensitivity and specificity. Further research is needed to confirm the performance of the test across various age and ethnic groups, and in different clinical settings.

Altered expression of genes involved in inflammation and apoptosis in frontal cortex in major depression.

The etiology of major depression (MDD), a common and complex disorder, remains obscure. Gene expression profiling was conducted on post-mortem brain tissue samples from Brodmann Area 10 (BA10) in the prefrontal cortex from psychotropic drug-free persons with a history of MDD and age, gender, and post-mortem interval-matched normal controls (n=14 pairs of subjects). Microarray analysis was conducted using the Affymetrix Exon 1.0 ST arrays. A set of differential expression changes was determined by dual-fold change-probability criteria (∣average log ratios∣>0.585 [equivalent to a 1.5-fold difference in either direction], P<0.01), whereas molecular pathways of interest were evaluated using Gene Set Enrichment Analysis software. The results strongly implicate increased apoptotic stress in the samples from the MDD group. Three anti-apoptotic factors, Y-box-binding protein 1, caspase-1 dominant-negative inhibitor pseudo-ICE, and the putative apoptosis inhibitor FKGS2, were over-expressed. Gene set analysis suggested up-regulation of a variety of pro- and anti-inflammatory cytokines, including interleukin 1α (IL-1α), IL-2, IL-3, IL-5, IL-8, IL-9, IL-10, IL-12A, IL-13, IL-15, IL-18, interferon gamma (IFNγ), and lymphotoxin α (TNF superfamily member 1). The genes showing reduced expression included metallothionein 1M (MT1M), a zinc-binding protein with a significant function in the modulation of oxidative stress. The results of this study indicate that post-mortem brain tissue samples from BA10, a region that is involved in reward-related behavior, show evidence of local inflammatory, apoptotic, and oxidative stress in MDD.

Can pharmacotherapists be too supportive? A process study of active medication and placebo in the treatment of depression.

BACKGROUND: This study examined therapist-patient interactions during clinical management with antidepressant medication and pill-placebo. METHOD: The sample consisted of 80 patients on active medication and 40 patients in a pill-placebo condition from a randomized controlled trial for moderate to severe depression. Pharmacotherapist-patient interactions were characterized using observer ratings of the therapeutic alliance, pharmacotherapist-offered facilitative conditions, pharmacotherapist adherence to clinical management treatment guidelines and pharmacotherapist competence. Patients, therapists and raters were blind to treatment condition and outcome. RESULTS: Provision of greater non-specific support (facilitative conditions) in early sessions predicted less subsequent improvement in depressive symptoms for patients receiving pill-placebo but not those receiving active medications, for which none of the process ratings predicted subsequent change. Early symptom change predicted later alliance and adherence in both conditions and therapist competence in the active condition. CONCLUSIONS: Higher levels of support in early sessions predict poorer subsequent response among placebo patients. It remains unclear whether patients who are likely to be refractory elicit greater non-specific support or whether the provision of such support has a deleterious effect in unmedicated patients. Differences in treatment process variables between conditions late in treatment are likely to be largely a consequence of symptom relief produced by active medications.

Elevated 5-HT 2A receptors in postmortem prefrontal cortex in major depression is associated with reduced activity of protein kinase A.

Previous human postmortem brain tissue research has implicated abnormalities of 5-HT receptor availability in depression and suicide. Although altered abundance of 5-HT 1A, 5-HT 2A, and 5-HT 2C receptors (5-HT(1A), 5-HT(2A), and 5-HT(2C)) has been reported, the causes remain obscure. This study evaluated the availability of these three receptor subtypes in postmortem brain tissue specimens from persons with a history of major depression (MDD) and normal controls and tested the relationships to protein kinases A and C (PKA, PKC). Samples were obtained from postmortem brain tissue (Brodmann area 10) from 20 persons with a history of MDD and 20 matched controls as determined by a retrospective diagnostic evaluation obtained from family members. Levels of 5-HT(1A), 5-HT(2A), and 5-HT(2C) receptor were quantitated via Western blot analyses. Basal and stimulated PKA and PKC activity were also determined. The depressed samples showed significantly increased 5-HT(2A) receptor abundance relative to controls, but no differences in 5-HT(1A) or 5-HT(2C) receptors. Basal and cyclic AMP-stimulated PKA activity was also reduced in the depressed sample; PKC activity was not different between groups. 5-HT(2A) receptor availability was significantly inversely correlated with PKC activity in controls, but with PKA activity in the depressed sample. Increased 5-HT(2A) receptor abundance and decreased PKA activity in the depressed sample are consistent with prior reports. The correlation of 5-HT(2A) receptor levels with PKA activity in the depressed group suggests that abnormalities of 5-HT(2A) receptor abundance may depend on receptor uncoupling and heterologous regulation by PKA.

Psychiatric profile and attention deficits in postural tachycardia syndrome.

OBJECTIVES: Patients with postural tachycardia syndrome (POTS) often appear anxious and report inattention. Patients with POTS were formally assessed for psychiatric disorders and inattention and compared with patients with attention deficit hyperactivity disorder (ADHD) and control subjects. METHODS: Patients with POTS (n = 21), ADHD (n = 18) and normal control subjects (n = 20) were assessed for DSM-IV psychiatric disorders and completed a battery of questionnaires that assessed depression, anxiety and ADHD characteristics. RESULTS: Patients with POTS did not have an increased prevalence of major depression or anxiety disorders, including panic disorder, compared with the general population. Patients with POTS had mild depression. They scored as moderately anxious on the Beck Anxiety Inventory but did not exhibit a high level of anxiety sensitivity. Patients with POTS scored significantly higher on inattention and ADHD subscales than control subjects. These symptoms were not present during childhood. CONCLUSIONS: Patients with POTS do not have an increased lifetime prevalence of psychiatric disorders. Although they may seem anxious, they do not have excess cognitive anxiety. They do experience significant inattention which may be an important source of disability.

Patterns of depressive symptom response in duloxetine-treated outpatients with mild, moderate or more severe depression.

AIMS: This was a post hoc analysis to determine whether baseline severity of depression influenced the efficacy of duloxetine in treating major depressive disorder (MDD) and to better characterise the symptom response profile for duloxetine in patients with mild, moderate or more severe depression. METHODS: Data were pooled from four double-blind, placebo-controlled studies in which outpatients with MDD were randomised to duloxetine (60 mg/day) or placebo for 8-9 weeks. Patients were retrospectively stratified according to baseline 17-item Hamilton Depression Rating scale (HAMD17) total scores: mild=total score

Norepinephrine transporter-deficient mice respond to anxiety producing and fearful environments with bradycardia and hypotension.

The study of anxiety and fear involves complex interrelationships between psychiatry and the autonomic nervous system. Altered noradrenergic signaling is linked to certain types of depression and anxiety disorders, and treatment often includes specific transporter blockade. The norepinephrine transporter is crucial in limiting catecholaminergic signaling. Norepinephrine transporter-deficient mice have increased circulating catecholamines and elevated heart rate and blood pressure. We hypothesized, therefore, that reduced norepinephrine clearance would heighten the autonomic cardiovascular response to anxiety and fear. In separate experiments, norepinephrine transporter-deficient (norepinephrine transporter-/-) mice underwent tactile startle and trace fear conditioning to measure hemodynamic responses. A dramatic tachycardia was observed in norepinephrine transporter-/- mice compared with controls following both airpuff or footshock stimuli, and pressure changes were also greater. Interestingly, in contrast to normally elevated home cage levels in norepinephrine transporter-deficient mice, prestimulus heart rate and blood pressure were actually higher in norepinephrine transporter+/+ animals throughout behavioral testing. Upon placement in the behavioral chamber, norepinephrine transporter-deficient mice demonstrated a notable bradycardia and depressor effect that was more pronounced in females. Power spectral analysis indicated an increase in low frequency oscillations of heart rate variability; in mice, suggesting increased parasympathetic tone. Finally, norepinephrine transporter-/- mice exhibited sexual dimorphism in freeze behavior, which was greatest in females. Therefore, while reduced catecholamine clearance amplifies immediate cardiovascular responses to anxiety- or fear-inducing stimuli in norepinephrine transporter-/- mice, norepinephrine transporter deficiency apparently prevents protracted hemodynamic escalation in a fearful environment. Conceivably, chronic norepinephrine transporter blockade with transporter-specific drugs might attenuate recognition of autonomic and somatic distress signals in individuals with anxiety disorders, possibly lessening their behavioral reactivity, and reducing the cardiovascular risk factors associated with persistent emotional arousal.

Noradrenergic antidepressants: does chronic treatment increase or decrease nuclear CREB-P?

Chronic administration of noradrenergic antidepressants causes a desensitization of the beta adrenoceptor coupled adenylate cyclase system. In the present studies, we attempted to answer the question of whether or not this deamplification is reflected beyond the second messenger system. Nuclear CREB-P was determined in frontal cortex of rats following acute and chronic administration of desipramine (DMI) or reboxetine and in human fibroblasts following incubation for 48 hours with DMI, reboxetine or venlafaxine. Nuclear CREB-P in the frontal cortex was significantly decreased following chronic administration of DMI or reboxetine. Moreover, incubation of human fibroblasts with DMI or reboxetine, but not with venlafaxine, caused a highly significant reduction in nuclear CREB-P suggesting that the noradrenergic antidepressants exert direct effects beyond beta adrenoceptors. The results are consistent with the view that chronic treatment with antidepressants causes a net deamplification of the norepinephrine mediated signal transduction cascade which might "normalize" the increased noradrenergic activity evident in major depression.

Detection of an mRNA polymorphism by differential display.

Differential Display (DD) technology was utilized to compare programs of gene expression in primary cultures of human skin fibroblasts from normal volunteers and patients diagnosed with melancholic depression. Polymorphic transcripts of a single gene differing by one tandem repeat sequence of four nucleotides (TGAT) in the 3' noncoding region were detected.

Can recovery from depression be achieved?

Even though a variety of treatments are available for depression, many patients experience an incomplete response, resulting in chronic functional impairment. The authors present a therapeutic heuristic that derives, in part, from a body of research that suggests that symptoms of mood disorders can be separated into three distinct components: somatic anxiety, which is most prominent in anxiety disorders, such as panic; anhedonia or low positive affect, which is most specific to depression; and general distress, which is present with both anxiety and depressive disorders. General distress and somatic anxiety appear to be significantly modulated by serotonin, and serotonergic drugs may exert their effects most significantly on these symptoms. On the other hand, positive affect, the dimension of reward-oriented motivation and enjoyment, appears to be most dependent on dopamine and, indirectly, norepinephrine. Thus a theoretical heuristic can be derived on the basis of the predominance of residual symptoms. Serotonergic agents would be chosen for monotherapy or augmentation for symptoms of distress. Alternatively, catecholaminergic drugs would be the first choice for anhedonia and decreased motivation.

Cross-talk between PKA and PKC in human fibroblasts: what are the pharmacotherapeutic implications?

BACKGROUND: The present study was designed to confirm or refute in human fibroblasts the hypothesized cross-talk elicited via neurotransmitter transduction cascades at the level of protein kinase mediated phosphorylation of the nuclear transcription factor CREB. METHODS: Human fibroblasts from normal control subjects were subcultured and incubated at confluency after five growth passages with isoproterenol (stimulation of PKA mediated phosphorylation) and/or phorbol 12-myristate 13-acetate (PMA) (stimulation of PKC mediated phosphorylation) followed by the determination of nuclear CREB-P by immunoblotting, enhanced chemiluminescence and quantitation of the autoradiograms by laser densitometry. RESULTS: Using the nuclear transcription factor CREB as a target, both the activation of the cyclic AMP-PKA pathway by isoproterenol and the activation of the PKC pathway by PMA caused phosphorylation of nuclear CREB. This phosphorylation is additive in nature and appears to occur at the same molecular site, serine133 of CREB. CONCLUSIONS: The present results in human fibroblasts demonstrate that the hypothesized cross-talk at the level of protein kinase mediated phosphorylation of transcription factors is no longer hypothetical. Since it is the phosphorylation of nuclear CREB that determines its dimerization and transcriptional activation of programs of CRE containing genes, the results suggest that this convergence of the neurotransmitter signals may be the critical mechanism in gene expression following the administration of antidepressant drugs that affect noradrenergic, serotonergic or both transduction cascades. The results may also provide a rationale for the apparent superior clinical efficacy of dual uptake inhibitors.

Mechanisms of action in the treatment of anxiety.

Anxiety and depressive disorders share many features, suggesting a common set of physiologic substrates. Recent research has indicated that mood can be categorized into 3 components by factor analysis: (1) somatic anxiety (a factor relatively specific to panic disorder), (2) anhedonic depression (which includes symptoms related to motivation and enjoyment and found to be specific to depression), and (3) general distress (a factor that cuts across all depressive and anxiety disorders studied). Antidepressant drugs, particularly serotonin reuptake inhibitors and serotonin receptor modulators, are effective for a wide variety of anxiety and depressive disorders. The impact on both anxiety and depression may be a result of an effect on a common set of physiologic targets relevant to the general distress dimension. At a cellular level, the antidepressants target components of the stress-adaptation system in brain, which may explain these common effects. On the other hand, there appear to be differences in the relative impact of serotonergic and noradrenergic drugs on the spectrum of distress and motivational symptoms. Basic research and clinical research suggest that serotonergic agents may be preferentially effective for symptoms of general distress, whereas catecholaminergic agents may target anhedonic depression symptoms.

Effectiveness of St John's wort in major depression: a randomized controlled trial.

CONTEXT: Extracts of St John's wort are widely used to treat depression. Although more than 2 dozen clinical trials have been conducted with St John's wort, most have significant flaws in design and do not enable meaningful interpretation. OBJECTIVE: To compare the efficacy and safety of a standardized extract of St John's wort with placebo in outpatients with major depression. DESIGN AND SETTING: Randomized, double-blind, placebo-controlled clinical trial conducted between November 1998 and January 2000 in 11 academic medical centers in the United States. PARTICIPANTS: Two hundred adult outpatients (mean age, 42.4 years; 67.0% female; 85.9% white) diagnosed as having major depression and having a baseline Hamilton Rating Scale for Depression (HAM-D) score of at least 20. INTERVENTION: Participants completed a 1-week, single-blind run-in of placebo, then were randomly assigned to receive either St John's wort extract (n = 98; 900 mg/d for 4 weeks, increased to 1200 mg/d in the absence of an adequate response thereafter) or placebo (n = 102) for 8 weeks. MAIN OUTCOME MEASURES: The primary outcome measure was rate of change on the HAM-D over the treatment period. Secondary measures included the Beck Depression Inventory (BDI), Hamilton Rating Scale for Anxiety (HAM-A), the Global Assessment of Function (GAF) scale, and the Clinical Global Impression-Severity and -Improvement scales (CGI-S and CGI-I). RESULTS: The random coefficient analyses for the HAM-D, HAM-A, CGI-S, and CGI-I all showed significant effects for time but not for treatment or time-by-treatment interaction (for HAM-D scores, P<.001, P =.16, and P =.58, respectively). Analysis of covariance showed nonsignificant effects for BDI and GAF scores. The proportion of participants achieving an a priori definition of response did not differ between groups. The number reaching remission of illness was significantly higher with St John's wort than with placebo (P =.02), but the rates were very low in the full intention-to-treat analysis (14/98 [14.3%] vs 5/102 [4.9%], respectively). St John's wort was safe and well tolerated. Headache was the only adverse event that occurred with greater frequency with St John's wort than placebo (39/95 [41%] vs 25/100 [25%], respectively). CONCLUSION: In this study, St John's wort was not effective for treatment of major depression.

Serum thyrotropin concentrations and bioactivity during sleep deprivation in depression.

BACKGROUND: One night of sleep deprivation induces a brief remission in about half of depressed patients. Subclinical hypothyroidism may be associated with depression, and changes in hypothalamic-pituitary-thyroid function may affect the mood response to sleep deprivation. We wished to define precisely the status of the hypothalamic-pituitary-thyroid axis of depressed patients during sleep deprivation and the possible relationship of hypothalamic-pituitary-thyroid function to the mood response. METHODS: We studied 18 patients with major depressive disorder and 10 normal volunteers. We assessed mood before and after sleep. We measured serum thyrotropin every 15 minutes during the night of sleep deprivation, thyrotropin bioactivity, the thyrotropin response to protirelin the next afternoon, and other indexes of hypothalamic-pituitary-thyroid function. To determine if the changes were limited to the hypothalamic-pituitary-thyroid axis, we measured serum cortisol, which also has a circadian secretory pattern. RESULTS: Nocturnal serum thyrotropin concentrations were consistently higher in responders, entirely because of elevated levels in the women reponders. Responders had exaggerated responses to protirelin the next afternoon. The bioactivity of thyrotropin in nonresponders was significantly greater than in responders (F(1,8. 99) = 7.52; P =.02). Other thyroid indexes and serum cortisol concentrations were similar among groups. CONCLUSIONS: Depressed patients have mild compensated thyroid resistance to thyrotropin action, not subclinical autoimmune primary hypothyroidism. Sleep deprivation responders compensate by secreting more thyrotropin with normal bioactivity; nonresponders compensate by secreting thyrotropin with increased bioactivity.

A novel augmentation strategy for treating resistant major depression.

OBJECTIVE: Treatment-resistant depression is a significant public health concern; drug switching or augmentation often produce limited results. The authors hypothesized that fluoxetine could be augmented with olanzapine to successfully treat resistant depression. METHOD: An 8-week double-blind study was conducted with 28 patients who were diagnosed with recurrent, nonbipolar, treatment-resistant depression without psychotic features. Subjects were randomly assigned to one of three groups: olanzapine plus placebo, fluoxetine plus placebo, or olanzapine plus fluoxetine. RESULTS: Fluoxetine monotherapy produced minimal improvement on various scales that rate severity of depression. The benefits of olanzapine monotherapy were modest. Olanzapine plus fluoxetine produced significantly greater improvement than either monotherapy on one measure and significantly greater improvement than olanzapine monotherapy on the other measures after 1 week. There were no significant differences between treatment groups on extrapyramidal measures nor significant adverse drug interactions. CONCLUSIONS: Olanzapine plus fluoxetine demonstrated superior efficacy for treating resistant depression compared to either agent alone.

Human fibroblasts as a relevant model to study signal transduction in affective disorders.

BACKGROUND: Previous studies have demonstrated a blunted beta adrenoceptor-linked protein kinase A (PKA) response in the 900xg supernatant fraction of human fibroblasts cultured from patients with major depression. RESULTS: Results of the present studies demonstrate a significant reduction in the B(max) value of [3H]cyclic AMP binding to the regulatory subunit of PKA in the supernatant fraction of fibroblasts from patients with major depression with no change in the K(d) values. The data are consistent with the previous observation that the maximal stimulation of PKA by cyclic AMP is reduced without a change in the EC(50) value. The blunted beta adrenoceptor-mediated PKA response in fibroblasts from patients with major depression is reflected in a significant reduction in the isoproterenol-stimulated phosphorylation of the nuclear transcription factor CREB. Both, the isoproterenol-mediated phosphorylation of nuclear CREB and the activation of the stably transfected luciferase reporter gene, pAD neo2-C12-BGL, were inhibited by the beta(2) adrenoceptor antagonist ICI 118551, thus indicating that the gene activating action of isoproterenol in human fibroblasts is mediated via the beta(2) adrenoceptor cascade. The low EC(50) value of 1 nM isoproterenol for activation of gene expression in stably transfected human fibroblasts appears to be a reflection of the amplification mechanism occurring via the beta adrenoceptor-cyclic AMP-PKA-CREB transduction cascade. CONCLUSIONS: The results support the notion that human fibroblasts represent a relevant model for studying processes of signal transduction in patients with affective disorders.

Intracellular mechanisms of antidepressant drug action.

The action of antidepressant drugs on monoamines such as norepinephrine and serotonin has been described for three decades. However, more-recent research has looked beyond cell surface receptors to transductional cascades and gene expression. Antidepressant drug therapies seem to share several mechanisms involved in either activating the adenylyl cyclase-protein kinase A cascade or inhibiting the phospholipase C-protein kinase C mechanisms. These effects, ultimately, combine to regulate the expression of target genes. Several specific genes are known to be activated or inhibited by antidepressant therapies. Steady-state levels of mRNA for glucocorticoid and mineralocorticoid receptors, brain-derived neurotrophic factor and its receptor trkB, and preproenkephalin are enhanced, whereas those for corticotropin-releasing hormone, c-fos,N-methyl-D-aspartate receptor subunits, and nerve-growth factor 1A are reduced. New molecular genetic methods for identifying differentially expressed genes will aid in the development of targets for wholly new generations of antidepressant drug therapies.