Effect of desipramine on cerebrospinal fluid concentrations of corticotropin-releasing factor in human subjects

Molecular changes associated with escitalopram response in a stress-based model of depression

Converging evidence points at hypothalamus-pituitary-adrenal (HPA) axis hyperactivity and neuroinflammation as important factors involved in the etiopathogenesis of major depressive disorder (MDD) and in therapeutic efficacy of antidepressants. In this study, we examined the molecular effects associated with a response to a week-long treatment with escitalopram in the chronic escape deficit (CED) model, a validated model of depression based on the induction of an escape deficit after exposure of rats to an unavoidable stress. We confirmed our previous result that a treatment with escitalopram (10mg/kg) was effective after 7days in reverting the stress-induced escape deficit in approximately 50% of the animals, separating responders from non-responders. Expression of markers of HPA axis functionality as well as several inflammatory mediators were evaluated in the hypothalamus, a key structure integrating signals from the neuro, immune, endocrine systems. In the hypothalamus of responder animals we observed a decrease in the expression of CRH and its receptors and an increase in GR protein in total and nuclear extracts; this effect was accompanied by a significant decrease in circulating corticosterone in the same cohort. Hypothalamic IL-1β and TNFα expression were increased in stressed animals, while CXCL2, IL-6, and ADAM17 mRNA levels were decreased in escitalopram treated rats regardless of the treatment response. These data suggest that efficacy of a one week treatment with escitalopram may be partially mediated by a decrease HPA axis activity, while in the hypothalamus the drug-induced effects on the expression of immune modulators did not correlate with the behavioural outcome.

Inhibition of the CRF1 receptor influences the activity of antidepressant drugs in the forced swim test in rats

Hyperactivity of the hypothalamic-pituitary-adrenal axis (HPA) and impairment of the central corticotropin-releasing factor (CRF) system are factors in the pathogenesis of depression. Though several antagonists of the CRF₁ receptor were effective in the recognized behavioral tests for antidepressant activity, there is still little information on the potential interactions between CRF₁ receptor inhibitors and conventional antidepressant therapy. The aim of our study was to assess the influence of SN003, a CRF₁ receptor blocker, on the activity of imipramine and fluoxetine in the forced swim test (FST) in rats which presented some signs of depression. The experiments were carried out on female Wistar rats subjected to 14-day subcutaneous corticosterone (CORT) administration (20 mg/kg/day). The antidepressant-like effect was determined by the FST and the CRF levels in the hypothalamus, amygdala, and peripheral blood were measured by a high-sensitivity immunoenzymatic test. SN003 (0.5 mg/kg) potentiated the antidepressant-like effect of imipramine (15 mg/kg) and fluoxetine (7.5 mg/kg). Moreover, the co-administration of the tested agents abolished CORT-induced increase in CRF levels in the examined biological material more profoundly than monotherapy. Our present findings give further evidence that the blockage of CRF action may be useful in the treatment of mood disorders. The concurrent use of well-known antidepressants with CRF₁ receptor antagonists could be beneficial in terms of safety, since it requires lower doses of the applied agents.

■ REVIEW : Corticotropin-releasing Factor, Stress, and Depression

Corticotropin-releasing factor (CRF), a 41 amino acid-containing neuropeptide, acts both as a hypothalamic releasing factor, controlling ACTH and corticosteroid secretion, and at extrahypothalamic CNS sites to mod ulate mammalian organisms' responses to stress. In this article, the evidence that CRF-containing neurons within the CNS are hyperactive in patients with depression is reviewed. The evidence, taken together, suggests that during depressive episodes, CRF is hypersecreted, resulting in both pituitary-adrenal axis hyperactivity and certain of the signs and symptoms of depression, including decreased appetite, decreased libido and disturbed sleep. There is also evidence that treatments for depression, including antidepressant medications and electroconvulsive therapy, reduce CRF hypersecretion within the CNS. Finally, evidence suggests that alterations in CRF-containing neurons and receptors are responsible for the widely held ob servation that early untoward life events increase an individual's vulnerability for affective disorders. These findings have a number of implications for treatment of the mood disorders, including the suggestion that the pharmacological manipulation of CRF receptors may provide a novel avenue for the treatment of de pression. NEUROSCIENTIST 3:186-194, 1997

Evidence for the role of corticotropin-releasing factor in major depressive disorder

Major depressive disorder (MDD) is a devastating disease affecting over 300 million people worldwide, and costing an estimated 380 billion Euros in lost productivity and health care in the European Union alone. Although a wealth of research has been directed toward understanding and treating MDD, still no therapy has proved to be consistently and reliably effective in interrupting the symptoms of this disease. Recent clinical and preclinical studies, using genetic screening and transgenic rodents, respectively, suggest a major role of the CRF1 gene, and the central expression of CRF1 receptor protein in determining an individual's risk of developing MDD. This gene is widely expressed in brain tissue, and regulates an organism's immediate and long-term responses to social and environmental stressors, which are primary contributors to MDD. This review presents the current state of knowledge on CRF physiology, and how it may influence the occurrence of symptoms associated with MDD. Additionally, this review presents findings from multiple laboratories that were presented as part of a symposium on this topic at the annual 2014 meeting of the International Behavioral Neuroscience Society (IBNS). The ideas and data presented in this review demonstrate the great progress that has been made over the past few decades in our understanding of MDD, and provide a pathway forward toward developing novel treatments and detection methods for this disorder.

Association analysis for corticotropin releasing hormone polymorphisms with the risk of major depressive disorder and the response to antidepressants

Hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis is one of the most consistent neuroendocrine abnormalities observed in patients with major depressive disorder (MDD). The peptide corticotropin-releasing hormone (CRH) is a key mediator for HPA axis function during stress. This study evaluated the associations of CRH polymorphisms with susceptibility to MDD and response to antidepressant treatment, and the gene-environment interaction with stressful life events (SLEs). After screening 31 polymorphisms in the gene encoding CRH, we evaluated the association of polymorphisms with MDD susceptibility in 149 patients with MDD and 193 control subjects; in patients, we also evaluated the response to treatment with antidepressants. Although genotypes and haplotypes were not significantly associated with the risk of MDD, non-remitters were more likely to carry haplotype 1 (ht1) than were remitters (P = 0.019-0.038), when only patients without SLE were included; however, the association was not significant after correction for multiple comparisons. Additionally, after 4 and 8 weeks of treatment in patients who experienced no SLEs, significantly higher 21-item Hamilton Depression Rating scores were found in MDD subjects who were CRH ht1 homozygotes compared to patients carrying one or no ht1 alleles (P = 0.007 and 0.027 at 4 and 8 weeks, respectively). Although these preliminary observations require further confirmation in future studies, these results on the interaction between CRH haplotypes and SLEs, suggest that CRH ht1 which is moderated by SLEs, may be associated with antidepressant treatment outcomes in patients with MDD.

Hypothalamic-pituitary-adrenocortical axis: neuropsychiatric aspects

Evidence of aberrant hypothalamic-pituitary-adrenocortical (HPA) activity in many psychiatric disorders, although not universal, has sparked long-standing interest in HPA hormones as biomarkers of disease or treatment response. HPA activity may be chronically elevated in melancholic depression, panic disorder, obsessive-compulsive disorder, and schizophrenia. The HPA axis may be more reactive to stress in social anxiety disorder and autism spectrum disorders. In contrast, HPA activity is more likely to be low in PTSD and atypical depression. Antidepressants are widely considered to inhibit HPA activity, although inhibition is not unanimously reported in the literature. There is evidence, also uneven, that the mood stabilizers lithium and carbamazepine have the potential to augment HPA measures, while benzodiazepines, atypical antipsychotics, and to some extent, typical antipsychotics have the potential to inhibit HPA activity. Currently, the most reliable use of HPA measures in most disorders is to predict the likelihood of relapse, although changes in HPA activity have also been proposed to play a role in the clinical benefits of psychiatric treatments. Greater attention to patient heterogeneity and more consistent approaches to assessing treatment effects on HPA function may solidify the value of HPA measures in predicting treatment response or developing novel strategies to manage psychiatric disease.

Interaction of stress, corticotropin-releasing factor, arginine vasopressin and behaviour

Stress mediates the activation of a variety of systems ranging from inflammatory to behavioral responses. In this review we focus on two neuropeptide systems, corticotropin-releasing factor (CRF) and arginine vasopressin (AVP), and their roles in regulating stress responses. Both peptides have been demonstrated to be involved in anxiogenic and depressive effects, actions mediated in part through their regulation of the hypothalamic-pituitary-adrenal axis and the release of adrenocorticotropic hormone. Because of the depressive effects of CRF and AVP, drugs modifying the stress-associated detrimental actions of CRF and AVP are under development, particularly drugs antagonizing CRF and AVP receptors for therapy in depression.

Disruption of fetal hormonal programming (prenatal stress) implicates shared risk for sex differences in depression and cardiovascular disease

Comorbidity of major depressive disorder (MDD) and cardiovascular disease (CVD) represents the fourth leading cause of morbidity and mortality worldwide, and women have a two times greater risk than men. Thus understanding the pathophysiology has widespread implications for attenuation and prevention of disease burden. We suggest that sex-dependent MDD-CVD comorbidity may result from alterations in fetal programming consequent to the prenatal maternal environments that produce excess glucocorticoids, which then drive sex-dependent developmental alterations of the fetal hypothalamic-pituitary-adrenal (HPA) axis circuitry impacting mood, stress regulation, autonomic nervous system (ANS), and the vasculature in adulthood. Evidence is consistent with the hypothesis that disruptions of pathways associated with gamma aminobutyric acid (GABA) in neuronal and vascular development and growth factors have critical roles in key developmental periods and adult responses to injury in heart and brain. Understanding the potential fetal origins of these sex differences will contribute to development of novel sex-dependent therapeutics.

Cerebrospinal fluid levels of glutamate and corticotropin releasing hormone in major depression before and after treatment

BACKGROUND

Glutamate and corticotropin releasing hormone (CRH) are pro-stress neurotransmitters and may be altered in the plasma and cerebrospinal fluid (CSF) of persons with major depressive disorder (MDD). The goal of this study was to compare the CSF levels of glutamate, glutamine and CRH between patients with depression and healthy controls.

METHODS

Eighteen patients with MDD and 25 healthy controls underwent a lumbar puncture (LP); CSF samples were withdrawn and assays were done for glutamine, glutamate, and CRH. Patients with MDD underwent 8 weeks of treatment with the antidepressant venlafaxine and then had a repeat LP post treatment.

RESULTS

Patients had higher baseline scores on depression and suicide rating scales and those scales improved significantly post-treatment. Higher suicidal ratings at baseline were correlated with higher glutamate levels (p=0.016). There were no significant differences between the control and patient group in any baseline CSF measures of glutamate (p=0.761), glutamine (p=0.226) or CRH (p=0.675). Despite no significant change in glutamate (p=0.358) and CRH (p=0.331) in the treatment group, there was a post-treatment decrease in glutamine (p=0.045) in patients.

LIMITATIONS

There was a small sample size, age discordance between patients and controls, lack of a follow-up LP in controls, absence of dexamethasone suppression testing, and fluctuating sample sizes among various measures.

CONCLUSION

Although no significant differences were noted between patients and controls at baseline there was an association of high CSF glutamate and suicidal ideation and lower glutamine post-treatment which may be correlated with attenuation of dysfunction in the glutamatergic system after antidepressant treatment.

The CRF system, stress, depression and anxiety-insights from human genetic studies

A concatenation of findings from preclinical and clinical studies support a preeminent function for the corticotropin-releasing factor (CRF) system in mediating the physiological response to external stressors and in the pathophysiology of anxiety and depression. Recently, human genetic studies have provided considerable support to several long-standing hypotheses of mood and anxiety disorders, including the CRF hypothesis. These data, reviewed in this report, are congruent with the hypothesis that this system is of paramount importance in mediating stress-related psychopathology. More specifically, variants in the gene encoding the CRF(1) receptor interact with adverse environmental factors to predict risk for stress-related psychiatric disorders. In-depth characterization of these variants will likely be important in furthering our understanding of the long-term consequences of adverse experience.

Corticotropin-Releasing Hormone, Glutamate, and γ-Aminobutyric Acid in Depression

Stress response and depression have a significant impact on modern society. Although the symptoms are well characterized, the molecular mechanisms underlying depression are largely unknown. The monoamine hypothesis, which postulates dysfunctional noradrenergic and serotonergic systems as the underlying primary cause of depression, has been valuable for the development of conventional antidepressants, which can reverse these dysfunctional states to some degree. However, recent data from various neuroscience disciplines have questioned the major role of amines in the pathogenesis of depression. A considerable amount of evidence has accumulated that suggests that normalization of the hypothalamo—pituitary—adrenal (HPA) system might be the final step necessary for a remission of depression. In addition, an increasing body of clinical and postmortem evidence is pointing to a role played by γ-aminobutyric acid (GABA) and glutamate in the etiology of depression. This review examines the evidence, mainly obtained from clinical studies or from postmortem brain material, for a major role of the HPA axis, glutamatergic, and GABAergic systems in the pathogenesis of major and bipolar depression. The authors hope that these insights will stimulate further studies with the final aim of developing new types of antidepressants that combine increased efficacy with a shorter delay of the onset of action and reduced side-effect profiles.

The hypothalamic-pituitary-adrenal axis in borderline personality disorder: a review

BACKGROUND

borderline personality disorder (BPD) is a psychiatric diagnosis characterized by high exposure, reactivity, and vulnerability to stress. Given these abnormalities in stress reactivity in BPD, there is a question of whether the hypothalamic-pituitary-adrenal (HPA) axis functions normally in BPD, since the activation of the HPA axis normally occurs to coordinate both behavioral and physiologic responses to stress. Several studies have investigated the functioning of the HPA axis in BPD and have shown varied results. This review seeks to summarize and interpret the findings of this growing literature.

METHODS

Pubmed search for English language articles on borderline personality disorder and hypothalamic-pituitary-adrenal axis.

RESULTS

findings are mixed but suggest that important variables relevant to between-group differences include comorbid depression, comorbid posttraumatic stress disorder, dissociative symptoms, and history of childhood abuse.

DISCUSSION

comorbid diagnoses and clinical features such as trauma history and symptom severity may have variable, interacting influences on the psychoneuroendocrine profile in BPD. Also explored here are the implications of these findings for developing possible models of HPA-axis dysfunction in BPD, for identifying potential targets for treatment, and for improving the methodology of future studies.

Emerging targets for antidepressant therapies

Despite adequate antidepressant monotherapy, the majority of depressed patients do not achieve remission. Even optimal and aggressive therapy leads to a substantial number of patients who show minimal and often only transient improvement. In order to address this substantial problem of treatment-resistant depression, a number of novel targets for antidepressant therapy have emerged as a consequence of major advances in the neurobiology of depression. Three major approaches to uncover novel therapeutic interventions are: first, optimizing the modulation of monoaminergic neurotransmission; second, developing medications that act upon neurotransmitter systems other than monoaminergic circuits; and third, using focal brain stimulation to directly modulate neuronal activity. We review the most recent data on novel therapeutic compounds and their antidepressant potential. These include triple monoamine reuptake inhibitors, atypical antipsychotic augmentation, and dopamine receptor agonists. Compounds affecting extra-monoamine neurotransmitter systems include CRF(1) receptor antagonists, glucocorticoid receptor antagonists, substance P receptor antagonists, NMDA receptor antagonists, nemifitide, omega-3 fatty acids, and melatonin receptor agonists. Focal brain stimulation therapies include vagus nerve stimulation (VNS), transcranial magnetic stimulation (TMS), magnetic seizure therapy (MST), transcranial direct current stimulation (tDCS), and deep brain stimulation (DBS).

Antagonism of CRF receptors prevents the deficit in brain reward function associated with precipitated nicotine withdrawal in rats

Nicotine dependence is a chronic mental illness that is characterized by a negative affective state upon tobacco smoking cessation and relapse after periods of abstinence. It has been hypothesized that cessation of nicotine administration results in the activation of brain corticotropin-releasing factor (CRF) systems that leads to the negative affective state of withdrawal. The aim of our experiments was to investigate the role of brain CRF systems in the deficit in brain reward function associated with the cessation of nicotine administration in rats. The intracranial self-stimulation procedure was used to assess to negative affective aspects of nicotine withdrawal as this procedure can provide a quantitative measure of emotional distress in rats. In the first experiment, mecamylamine induced a dose-dependent elevation in brain reward thresholds in nicotine-treated rats. In the follow-up experiment, it was shown that pretreatment with the corticotropin-receptor antagonist D-Phe CRF((12-41)) prevents the elevations in brain reward thresholds associated with precipitated nicotine withdrawal. In the third experiment, the effect of D-Phe CRF((12-41)) on the elevations in brain reward thresholds associated with spontaneous nicotine withdrawal was investigated. Administration of D-Phe CRF((12-41)) 6 h after the explantation of the nicotine pumps, did not result in a lowering of the brain reward thresholds. These findings indicate that antagonism of CRF receptors prevents, but not reverses, the deficit in brain associated with nicotine withdrawal. These data provide support for the hypothesis that a hyperactivity of brain CRF systems may at least partly mediate the initiation of the negative affective aspects of nicotine withdrawal.

Neuroendocrinological mechanisms of actions of antidepressant drugs

Noradrenaline or serotonin (5-HT) reuptake-inhibiting antidepressants such as reboxetine or citalopram acutely stimulate cortisol and adrenocorticotrophic hormone (ACTH) secretion in healthy volunteers, whereas mirtazapine acutely inhibits the ACTH and cortisol release, probably due to its antagonism at central 5-HT(2) and/or H(1) receptors. These differential effects of antidepressants on cortisol and ACTH secretion in healthy subjects after single administration are also reflected by their different time course in the down-regulation of hypothalamic-pituitary-adrenocortical (HPA) axis hyperactivity in depressed patients as assessed by serial dexamethasone (DEX)/corticotrophin-releasing hormone (CRH) tests: Reuptake-inhibiting antidepressants such as reboxetine gradually normalise HPA axis hyperactivity in depressed patients during several weeks of treatment via up-regulation of mineralocorticoid and glucocorticoid receptor function and by step-by-step restoration of the disturbed feedback control. By contrast, mirtazapine markedly reduces HPA axis activity in depressed patients within 1 week, but there is a partial re-enhancement of HPA hormone secretion after several weeks of therapy. In all studies performed to date, the short-term effects of daily treatment with antidepressants on the DEX/CRH test results are comparable in responders and nonresponders. Moreover, a reduction in HPA axis activity is not necessarily followed by a favourable clinical response and some depressed patients keep on showing nonsuppression in the DEX/CRH test despite clinical improvement. Therefore, the importance of HPA axis dysregulation for the short-term efficacy of antidepressants continues to be a matter of debate. However, there are convincing data suggesting that persisting nonsuppression in the DEX/CRH test despite clinical remission predicts an enhanced risk for relapse of depressive symptomatology with respect to the medium- and long-term outcome.

Emerging treatments for depression

Established treatments for depression are often effective. However, a significant number of patients show limited or no response. With advancements in the explanation of the underlying neurobiology of depression, several novel therapeutic approaches have been developed. Emerging drug targets include novel monoamine oxidase inhibitors, triple monoamine re-uptake inhibitors, omega-3 fatty acids, melatoninergic agonists and receptor antagonists for corticotropin-releasing factor(1), glucocorticoid, substance-P and NMDA. Developments in therapeutic focal brain stimulation include vagus nerve stimulation, transcranial magnetic stimulation, magnetic seizure therapy and deep brain stimulation. The role of psychotherapy, both as monotherapy and as adjunctive therapy, is an active avenue of investigation. Although data on these treatments are limited, preliminary results are encouraging. A major goal that remains to be achieved is the identification of predictors of response to the various antidepressant treatments that have diverse mechanisms of action.

Links between depression and substance abuse in adolescents: neurobiological mechanisms

Adolescence is a high-risk period for development of both depressive and substance use disorders. These two disorders frequently co-occur in adolescents and are associated with significant morbidity and mortality. Given the added economic and psychosocial burden associated with the comorbid condition, identification of risk factors associated with their co-occurrence is of great public health importance. Research with adult animals and humans has indicated several common neurobiological systems that link depressive and addictive disorders. Given the ongoing maturation of these systems throughout adolescence and early adult life, it is not clear how these neurobiological processes influence development and progression of both disorders. A better understanding of the pathophysiological mechanisms leading to the onset and course of these disorders during adolescence will be helpful in developing more effective preventive and treatment strategies, and thereby allow these youth to reach their full potential as adults.

Future prospects in depression research

Major depression is a common, disabling, and often difficult-to-treat illness. Decades of research into the neurobiology and treatment of depression have greatly advanced our ability to manage this disorder. However, a number of challenges remain. A substantial number of depressed patients do not achieve full remission despite optimized treatment. For patients who do achieve resolution of symptoms, depression remains a highly recurrent illness, and repeated episodes are common. Finally, little is known about how depression might be prevented, especially in individuals at increased risk. In the face of these challenges, a number of exciting research efforts are currently under way and promise to greatly expand our knowledge of the etiology, pathophysiology, and treatment of depression. This review highlights these future prospects for depression research with a specific focus on lines of investigation likely to generate novel, more effective treatment options.

Advances in the treatment of depression

SUMMARY

Depression is a highly prevalent and disabling condition associated with significant morbidity and mortality. Currently available treatments for depression include tricyclic antidepressants, monoamine oxidase inhibitors, selective serotonin reuptake inhibitors, serotonin norepinephrine reuptake inhibitors, various atypical antidepressants, and electroconvulsive therapy. Although these treatments are effective, a significant number of patients do not respond or achieve sustained remission despite aggressive management. Advances in the neurobiology of depression have suggested a number of novel targets for antidepressant treatment. Based on an improved understanding of the neurobiology of depression, several novel pharmacologic and nonpharmacologic interventions are being developed. Pharmacologic developments include CRF antagonists, glucocorticoid receptor antagonists, substance P receptor antagonists, NMDA glutamate receptor antagonists, transdermal selegiline, so-called "triple" reuptake inhibitors, and augmentation of typical antidepressant medications with atypical antipsychotics. Nonpharmacologic advances have largely involved focal brain stimulation techniques including vagus nerve stimulation, transcranial magnetic stimulation, magnetic seizure therapy, and deep brain stimulation. For the most part, the data on these treatments are preliminary, and more study is needed to clarify their potential clinical benefit. However, it is clear that further study of the neurobiology of depression will continue to provide a rationale for developing innovative targets for antidepressant therapies.

Corticotropin-releasing factor type-1 receptor antagonists: the next class of antidepressants?

Corticotropin-releasing factor (CRF) is a neuropeptide that plays a primary role in the neuroendocrine, autonomic, and behavioral responses to stressors. Numerous reports suggest that alterations in CRF function contribute to the pathogenesis of depression. Recently, selective nonpeptide CRF type 1 (CRF1) receptor antagonists have been discovered and several of these CRF1 receptor antagonists have demonstrated antidepressant-like efficacy in animals. The CRF1 receptor antagonists appear to be unique, as they exhibit antidepressant-like activity principally in animal models that are hyperresponsive to stress or under experimental conditions that alter endogenous stress-hormone activity. A nonpeptide CRF1 receptor antagonist has also been shown to reduce symptoms of major depression in an open-label clinical trial. Accumulating evidence supports a role for nonpeptide CRF1 receptor antagonists among the future pharmacotherapies for the treatment of depression.

The stress system in the human brain in depression and neurodegeneration

Corticotropin-releasing hormone (CRH) plays a central role in the regulation of the hypothalamic-pituitary-adrenal (HPA)-axis, i.e., the final common pathway in the stress response. The action of CRH on ACTH release is strongly potentiated by vasopressin, that is co-produced in increasing amounts when the hypothalamic paraventricular neurons are chronically activated. Whereas vasopressin stimulates ACTH release in humans, oxytocin inhibits it. ACTH release results in the release of corticosteroids from the adrenal that, subsequently, through mineralocorticoid and glucocorticoid receptors, exert negative feedback on, among other things, the hippocampus, the pituitary and the hypothalamus. The most important glucocorticoid in humans is cortisol, present in higher levels in women than in men. During aging, the activation of the CRH neurons is modest compared to the extra activation observed in Alzheimer's disease (AD) and the even stronger increase in major depression. The HPA-axis is hyperactive in depression, due to genetic factors or due to aversive stimuli that may occur during early development or adult life. At least five interacting hypothalamic peptidergic systems are involved in the symptoms of major depression. Increased production of vasopressin in depression does not only occur in neurons that colocalize CRH, but also in neurons of the supraoptic nucleus (SON), which may lead to increased plasma levels of vasopressin, that have been related to an enhanced suicide risk. The increased activity of oxytocin neurons in the paraventricular nucleus (PVN) may be related to the eating disorders in depression. The suprachiasmatic nucleus (SCN), i.e., the biological clock of the brain, shows lower vasopressin production and a smaller circadian amplitude in depression, which may explain the sleeping problems in this disorder and may contribute to the strong CRH activation. The hypothalamo-pituitary thyroid (HPT)-axis is inhibited in depression. These hypothalamic peptidergic systems, i.e., the HPA-axis, the SCN, the SON and the HPT-axis, have many interactions with aminergic systems that are also implicated in depression. CRH neurons are strongly activated in depressed patients, and so is their HPA-axis, at all levels, but the individual variability is large. It is hypothesized that particularly a subgroup of CRH neurons that projects into the brain is activated in depression and induces the symptoms of this disorder. On the other hand, there is also a lot of evidence for a direct involvement of glucocorticoids in the etiology and symptoms of depression. Although there is a close association between cerebrospinal fluid (CSF) levels of CRH and alterations in the HPA-axis in depression, much of the CRH in CSF is likely to be derived from sources other than the PVN. Furthermore, a close interaction between the HPA-axis and the hypothalamic-pituitary-gonadal (HPG)-axis exists. Organizing effects during fetal life as well as activating effects of sex hormones on the HPA-axis have been reported. Such mechanisms may be a basis for the higher prevalence of mood disorders in women as compared to men. In addition, the stress system is affected by changing levels of sex hormones, as found, e.g., in the premenstrual period, ante- and postpartum, during the transition phase to the menopause and during the use of oral contraceptives. In depressed women, plasma levels of estrogen are usually lower and plasma levels of androgens are increased, while testosterone levels are decreased in depressed men. This is explained by the fact that both in depressed males and females the HPA-axis is increased in activity, parallel to a diminished HPG-axis, while the major source of androgens in women is the adrenal, whereas in men it is the testes. It is speculated, however, that in the etiology of depression the relative levels of sex hormones play a more important role than their absolute levels. Sex hormone replacement therapy indeed seems to improve mood in elderly people and AD patients. Studies of rats have shown that high levels of cumulative corticosteroid exposure and rather extreme chronic stress induce neuronal damage that selectively affects hippocampal structure. Studies performed under less extreme circumstances have so far provided conflicting data. The corticosteroid neurotoxicity hypothesis that evolved as a result of these initial observations is, however, not supported by clinical and experimental observations. In a few recent postmortem studies in patients treated with corticosteroids and patients who had been seriously and chronically depressed no indications for AD neuropathology, massive cell loss, or loss of plasticity could be found, while the incidence of apoptosis was extremely rare and only seen outside regions expected to be at risk for steroid overexposure. In addition, various recent experimental studies using good stereological methods failed to find massive cell loss in the hippocampus following exposure to stress or steroids, but rather showed adaptive and reversible changes in structural parameters after stress. Thus, the HPA-axis in AD is only moderately activated, possibly due to the initial (primary) hippocampal degeneration in this condition. There are no convincing arguments to presume a causal, primary role for cortisol in the pathogenesis of AD. Although cortisol and CRH may well be causally involved in the signs and symptoms of depression, there is so far no evidence for any major irreversible damage in the human hippocampus in this disorder.

Effect of bupropion on nocturnal urinary free cortisol and its association with antidepressant response

The study examined the relationship between pre-treatment nocturnal hypothalamic-pituitary-adrenal (HPA) activity, as reflected by nocturnal urinary free cortisol (NUFC) response to a single-dose of sustained-release bupropion, and the antidepressant effect of the drug. NUFC changes in response to treatment with bupropion also were assessed. NUFC was measured in 20 patients with unipolar major depressive disorder before and after initiating treatment with sustained-release bupropion. Prior to treatment, subjects were studied on two separate sessions, one week apart. On the morning of each session, the participants received bupropion (150 mg, PO) or placebo using a randomized, double-blind procedure. Following the second session, subjects then received open-label treatment with bupropion for 8 weeks. NUFC sampling was repeated at the end of treatment. There was a significant interaction between NUFC concentration in response to single-dose bupropion and its antidepressant effect. Treatment non-responders showed a significant increase in NUFC in response to a single-dose of bupropion, whereas responders showed no such change. In addition, the NUFC response to bupropion challenge correlated significantly with the change in depression ratings as a result of treatment. In contrast to many other antidepressants, treatment with bupropion for 8 weeks did not reduce HPA activity in either responders or non-responders. These findings suggest that the NUFC response to a test-dose of bupropion might be helpful in predicting its antidepressant effect. One possible mechanism for the association between the NUFC response to acute bupropion challenge and antidepressant efficacy might be linked through dopaminergic and/or noradrenergic mechanisms.

The role of corticotropin-releasing factor-like peptides in cannabis, nicotine, and alcohol dependence

The corticotropin-releasing factor (CRF)-like peptides, which include the mammalian peptides CRF, urocortin 1, urocortin 2, and urocortin 3, play an important role in orchestrating behavioral and physiological responses that may increase an organism's chance of survival when confronted with internal or external stressors. There is, however, evidence that a chronic overactivity of brain CRF systems under basal conditions may play a role in the etiology and maintenance of psychiatric disorders such as depression and anxiety disorders. In addition, there is evidence of a role for CRF-like peptides in acute and protracted drug abstinence syndromes and relapse to drug-taking behavior. This review focuses on the role of CRF-like peptides in the negative affective state associated with acute and protracted withdrawal from three widely abused drugs, cannabis, nicotine, and alcohol. In addition, we discuss the high comorbidity between stress-associated psychiatric disorders and drug dependence. A better understanding of the brain stress systems that may underlie psychiatric disorders, acute and protracted drug withdrawal, and relapse to drug-taking behavior may help in the development of new and improved pharmacotherapies for these widespread psychiatric disorders.

Neurobiological mechanisms in addictive and psychiatric disorders

The studies reviewed indicate that brain stress system play an important role in the acquisition and maintenance of drugs of abuse that target the brain's reward centers. In doing so, they may destabilize these areas, making the perception of pleasure more elusive and difficult to attain. Withdrawal from drugs of abuse leads to the activation of brain CRF systems that may produce the anxiogenic response associated with drug withdrawal. More research, however, is needed to investigate the role of brain stress systems and neuropeptides in other drug withdrawal symptoms such as anhedonia. A better understanding of the brain systems underlying drug withdrawal may help in the development of improved pharmacotherapies that can alleviate drug withdrawal symptoms. The second part of the article indicated that there is a very high comorbidity between depression and drug dependence. The reviewed studies suggest that depressed patients initiate drug-taking behavior to self-medicate the symptoms associated with their psychiatric disorder. Chronic use of drugs of abuse, however, may exacerbate the symptoms of pre-existing mental disorders and subsequently increase drug-taking behavior. Conversely, professional treatment of pre-existing psychiatric disorders may decrease the use of illicit substances.

Four days of citalopram increase suppression of cortisol secretion by prednisolone in healthy volunteers

RATIONALE

Chronic antidepressant treatment increases glucocorticoid-mediated negative feedback on the hypothalamic-pituitary-adrenal (HPA) axis, and thus reduces HPA axis activity, in depressed patients and healthy controls. In contrast, acute antidepressant treatment induces an activation of basal HPA axis activity.

OBJECTIVES

We examined the effects of 4 days of treatment with the selective serotonin reuptake inhibitor, citalopram, on basal salivary cortisol and on suppression of salivary cortisol by prednisolone.

METHODS

We used a single-blind, placebo-controlled, repeated-measure design. Salivary cortisol was measured from 0900 to 1700 hours. In the first phase of the study, basal salivary cortisol secretion was measured on 2 study days, before and after 4 days of treatment with citalopram (orally, 20 mg/day). In the second phase, salivary cortisol secretion after suppression by prednisolone (5 mg, given at 2200 hours the night before) was measured on 2 study days, again before and after 4 days of treatment with citalopram (orally, 20 mg/day). Eight volunteers participated to the study.

RESULTS

Citalopram increased basal salivary cortisol in the morning (0900-1100 hours) by approximately 47% (P=0.003). Moreover, citalopram increased suppression by prednisolone in the morning (0900-1100 hours): suppression was approximately 22% before citalopram and 45% after citalopram (P=0.05).

CONCLUSIONS

Citalopram increases glucocorticoid-mediated negative feedback on the HPA axis after as little as 4 days of treatment. This effect could be due to an increased function of the corticosteroid receptors. Our findings further support the notion that one of the mechanisms by which antidepressants exert their therapeutic effects is by normalizing HPA axis hyperactivity in depressed patients.

The effects of chronic treatment with the mood stabilizers valproic acid and lithium on corticotropin-releasing factor neuronal systems

Corticotropin-releasing factor (CRF) plays a preeminent role in coordinating the endocrine, autonomic, and behavioral responses to stress. Dysregulation of both hypothalamic and extrahypothalamic CRF systems have been reported in patients with major depression and post-traumatic stress disorder. Moreover, effective treatment of these conditions leads to normalization of these CRF systems. Although there is virtually no data concerning alterations of CRF systems in bipolar disorder (manic depressive illness), previous work indicates that valproic acid, an anticonvulsant also effective in the treatment of acute mania, alters central CRF neuronal systems. In the current studies, we chronically administered valproic acid and lithium, two clinically effective mood stabilizers, in nonstressed rats to extend our previous findings. Chronic valproic acid administration decreased CRF mRNA expression in the paraventricular nucleus of the hypothalamus; lithium administration increased CRF mRNA expression in the central nucleus of the amygdala. Although valproic acid increased CRF(1) receptor mRNA expression in the cortex, CRF(1) receptor binding was decreased in both the basolateral amygdala and cortex, suggesting that chronic valproate treatment may in fact dampen the overall tone in this central stress pathway. Valproate treatment decreased CRF(2A) mRNA expression in both the lateral septum and hypothalamus, although CRF(2A) receptor binding was unchanged. Lithium administration decreased CRF(1) mRNA expression in both the amygdala and frontal cortex, but CRF(1) receptor binding also remained unchanged. These results suggest that the therapeutic actions of these mood stabilizers may, in part, result from their actions on central CRF neuronal systems. The distinct actions of each drug on CRF systems may underlie their synergistic clinical effects.

Depression and anxiety and outcomes of coronary artery bypass surgery

Psychological and psychiatric disorders independently increase the risk of cardiovascular disease and worsen the prognosis in patients with established cardiovascular lesions. The objective of this literature review is to discuss recent data concerning the relationships between depression and anxiety and the outcomes of coronary artery bypass grafting. Pathophysiological hypotheses are put forward to explain observed links. We suggest recommendations aimed at improving the psychological evaluation and management of heart surgery candidates, as well as postbypass patients, in the hope of improving quality of life and cardiovascular outcomes in these patients.

Intracerebroventricular corticotropin-releasing factor increases limbic glucose metabolism and has social context-dependent behavioral effects in nonhuman primates

Corticotropin-releasing factor (CRF) is a neuropeptide involved in integrating the behavioral, autonomic, and hormonal responses to stress within the central nervous system. Patients suffering from depression have abnormal activity in stress responsive brain regions and elevated cerebrospinal fluid CRF. The DSM-IV criteria for major depressive disorder include behavioral changes such as depressed mood, anhedonia, and psychomotor agitation/retardation. We studied the effects of 434 microgram of CRF given intracerebroventricularly over 40 min in group and individually housed monkeys to examine the role of elevated levels of central CRF on behavior. CRF elicited a wide range of behaviors, which fell into three broad categories: anxiety-like, depressive-like, and externally oriented. Externally oriented behaviors decreased, and anxiety-like behaviors increased regardless of how the animals were housed. Interestingly, increased depressive-like behaviors were only observed when the animals were socially housed. In a separate experiment, we examined the effects of the same dose of CRF on the regional cerebral glucose metabolism of lightly anesthetized monkeys by using positron emission tomography and [(18)F]fluorodeoxyglucose. CRF infusion increased glucose metabolism in the pituitary/infundibulum, the amygdala, and hippocampus. These results indicate that increased central CRF tone affects primate behavior in a context-dependent manner, and that it activates limbic and stress-responsive regions. The fact that intracerebroventricular CRF increases depressive-like behavior in socially housed animals and increases activity in limbic brain regions may help explain the behavioral and metabolic alterations in humans with affective disorders, and this model could therefore have significant value in the development of novel antidepressant treatments.

New directions in the development of antidepressants: the interface of neurobiology and psychiatry

There have been considerable advances in neurobiology in recent years that are providing new directions for the development of novel classes of antidepressants. For example, the finding that corticotropin-releasing factor (CRF) is hypersecreted in depressed patients and mediates certain symptoms of depression has led to the development of specific antagonists of the CRF(1) receptor. These are expected to prove highly effective for the treatment of mood and anxiety disorders. Another related avenue of research is based on evidence that cortisol is integral to the pathophysiology of major depression with psychotic features. One alternative for treating this subtype of affective disorder is, therefore, to block the action of glucocorticoids using a receptor antagonist such as mifepristone. These are just two of the many new directions that will likely lead to the development of antidepressants in the near future.

Aetiopathogenesis and pathophysiology of bulimia nervosa: biological bases and implications for treatment

Bulimia nervosa is an eating disorder characterised by recurrent episodes of binge eating and associated efforts to purge the ingested calories through self-induced vomiting, laxative or diuretic abuse, fasting or intensive exercise. The aetiopathogenesis and pathophysiology of the disorder are currently unclear. Biological bases have been proposed repeatedly, based on several lines of evidence: hunger, satiety and food choice are regulated by neurotransmitters and neuropeptides, and impairment of eating habits may be related to alterations in the secretion of these chemicals; genetic studies suggest that these neurotransmitter systems are dysfunctional in individuals with bulimia nervosa; and the frequent comorbidity of bulimia nervosa with major depressive and obsessive-compulsive disorders, conditions in which multiple alterations of brain biochemical functions have been demonstrated. Data in the literature suggest that levels of noradrenaline (norepinephrine) and serotonin (5-hydroxytryptamine; 5-HT) are lower in individuals with bulimia nervosa than in healthy controls. Levels of dopamine are similar to, or lower than, those in controls. After remission of the disorder, noradrenergic function returns to that seen in controls, whereas dopaminergic and serotonergic function rebound to levels higher than in controls. Among the neuropeptides, alterations in the levels of neuropeptide Y, peptide YY, beta-endorphin, corticotrophin-releasing hormone, somatostatin, cholecystokinin and vasopressin have been found in the symptomatic phase of bulimia nervosa, with a return to levels seen in controls after remission. Pharmacological treatment of bulimia nervosa that is directed at correction of the neurochemical alterations observed is difficult because of the complexity of the impairments. However, such treatment is necessary and should be continued long after symptomatic remission to ensure reinstitution of cerebral biochemical homeostasis.

Neuropharmacology of venlafaxine

Venlafaxine (Effexor) is an effective antidepressant and has also been approved for the treatment of generalized anxiety disorder. Venlafaxine was initially characterized as an inhibitor of both serotonin (5HT) and norepinephrine (NE) uptake and was therefore termed a "dual uptake inhibitor." This chapter reviews data from both in vitro and in vivo studies regarding its effects on 5HT and NE neurotransmission. In addition, the effects of venlafaxine on other systems that may play a role in its therapeutic efficacy effects are described. The data indicate that venlafaxine is a relatively weak inhibitor of NE transport in vitro. In vivo studies indicate that venlafaxine selectively inhibits 5HT uptake at low therapeutic doses and inhibits both 5HT and NE uptake at higher therapeutic doses. This chapter concludes with a discussion of the effects of venlafaxine on various aspects of physiology.

The role of childhood trauma in the neurobiology of mood and anxiety disorders: preclinical and clinical studies

Epidemiologic studies indicate that children exposed to early adverse experiences are at increased risk for the development of depression, anxiety disorders, or both. Persistent sensitization of central nervous system (CNS) circuits as a consequence of early life stress, which are integrally involved in the regulation of stress and emotion, may represent the underlying biological substrate of an increased vulnerability to subsequent stress as well as to the development of depression and anxiety. A number of preclinical studies suggest that early life stress induces long-lived hyper(re)activity of corticotropin-releasing factor (CRF) systems as well as alterations in other neurotransmitter systems, resulting in increased stress responsiveness. Many of the findings from these preclinical studies are comparable to findings in adult patients with mood and anxiety disorders. Emerging evidence from clinical studies suggests that exposure to early life stress is associated with neurobiological changes in children and adults, which may underlie the increased risk of psychopathology. Current research is focused on strategies to prevent or reverse the detrimental effects of early life stress on the CNS. The identification of the neurobiological substrates of early adverse experience is of paramount importance for the development of novel treatments for children, adolescents, and adults.

Elevated plasma thymopoietin associated with therapeutic nonresponsiveness in major depression

BACKGROUND

Stress predisposes to major depression, and hyperactivity of the stress-activated hypothalamic-pituitary-adrenal (HPA) axis occurs in this disease. Thymopentin, an active fragment of thymopoietin (TP), reduces endocrine and behavioral responses to experimental stress, possibly by lowering plasma TP (pTP) levels.

METHODS

Plasma TP and the HPA hormones arginine vasopressin (pAVP), adrenocorticotropic hormone (pACTH), and plasma cortisol (pCORT) were measured in 21 untreated depressed patients and 21 matched control subjects. Clinical responses to antidepressants were evaluated in 17 depressed patients.

RESULTS

Plasma TP was elevated in depression (p < .002), with in 8 out of 21 (38%) depressed patients having significant elevations (p < .03). For 17 patients whose antidepressant responses were evaluated, nonresponsiveness occurred in 6 out of 7 (86%) with elevated pTP (>7.5 pg/mL) versus 3 out of 10 (30%) with normal pTP (p < .05).

CONCLUSIONS

The significant association of elevated pTP with nonresponsiveness to antidepressant drugs may signify a distinct pathogenesis for the depression of patients with elevated pTP.

The impact of early adverse experiences on brain systems involved in the pathophysiology of anxiety and affective disorders

The relative contribution of genetic and environmental factors to the development of the major psychiatric disorders has long been debated. Recently, considerable attention has been given to the observations that adverse experiences early in life predispose individuals to the development of affective and anxiety disorders in adulthood. Corticotropin-releasing factor (CRF) is the central coordinator of the endocrinologic, autonomic, immunologic, and behavioral stress responses. When centrally administered, CRF produces many physiologic and behavioral changes reminiscent of both acute stress and depression. Moreover, CRF has also been implicated in the pathogenesis of a variety of anxiety disorders, mainly through CRF neurocircuits connecting the amygdala and the locus ceruleus. Clinical studies have provided convincing evidence for central CRF hypersecretion in depression, and, to a lesser extent, in some anxiety disorders. Evidence mainly from preclinical studies suggests that stress early in life results in persistent central CRF hyperactivity and increased stress reactivity in adulthood. Thus, genetic disposition coupled with early stress in critical phases of development may result in a phenotype that is neurobiologically vulnerable to stress and may lower an individual's threshold for developing depression and anxiety upon further stress exposure. This pathophysiologic model may provide novel approaches to the prevention and treatment of psychopathology associated with stress early in life.

The human hypothalamo-neurohypophysial system in health and disease

The present paper reviews the changes observed in the human supraoptic (SON) and paraventricular (PVN) nuclei, and their projections to the neurohypophysis, median eminence and to other brain areas in health and disease.

Assessment and treatment of depression in the cancer patient

The prevalence, diagnosis, and treatment of depression in the cancer patient are reviewed. Although frequently encountered in the cancer patient population, depression often remains undiagnosed and untreated. This carries grave consequences in that depressed cancer patients experience a poorer quality of life, are less compliant with medical care, have longer hospital stays, and have higher mortality rates. Diagnostic assessment of depression in the cancer patient raises difficulties both upon phenomenological and etiological grounds. In particular, the presence of neurovegetative symptoms which may be secondary to either cancer or depression may cloud the diagnostic picture. Due to the serious consequences of unrecognized depression, a more sensitive inclusive approach to diagnosis is recommended in the clinical setting. Finally, the limited data regarding treatment of depression in patients with cancer is reviewed. This includes a discussion of both psychosocial and pharmacological interventions which are shown to alleviate depression, improve quality of life measures, improve immune function, and lengthen survival time.

Psychoneuroendocrinology of depression. Hypothalamic-pituitary-adrenal axis

Among the more consistent observations in patients with major depression is dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis presenting as elevation of basal cortisol, dexamethasone-mediated negative feedback resistance, increased cerebrospinal fluid levels of corticotropin-releasing factor (CRF), and a blunted adrenocorticotropic hormone (ACTH) response to challenge with exogenous CRF. These features appear to be state, rather than trait markers, and are normalized upon successful treatment. These pathophysiologic adaptations may arise from defects in central drive to the neuroendocrine hypothalamus, disruption of normal adrenocortical hormone receptor function or a modification of HPA axis function at any level. Functional assessment of the HPA axis is thought to provide a window into central nervous system operation that may be of diagnostic value in this and other affective disorders regardless of whether CRF and glucocorticoids are directly involved in the origin of major depression or merely exacerbate the consequences of other primary defects.

Depression-related cognitive impairment: possibilities for its pharmacological treatment

Depression-related cognitive impairment (DRCI) is a condition which despite its initial treatment response, shows a progressive deterioration. No consistent therapeutic strategies have been proposed to combat this condition. This may be due to a reluctance to treat the cognitively impaired, a failure to recognise the deleterious prognosis or a poor understanding of the likely pathogenesis. Increasing evidence implicates the hypothalamo-pituitary-adrenal (HPA) axis as a key neurobiological determinant of the presentation and course of depression-induced cognitive decline. By utilising agents which control central glucocorticoid hyperactivity over a sustained period, whilst avoiding those agents which may compromise cognitive abilities, there exists a pharmacological strategy which may minimise the morbidity of cognitive impairment related to depressive illness.