Brain Region-Specific Effects of Short-Term Treatment with Duloxetine, Venlafaxine, Milnacipran and Sertraline on Monoamine Metabolism in Rats

The role of peripheral serotonin and norepinephrine in the gastroprotective effect against stress of duloxetine

Duloxetine has been shown to produce gastroprotective effect against gastric ulcer induced by water immersion restraint stress (WIRS) via modulation of NADPH oxidases in the gastric mucosa and neurometabolites of central nucleus of amygdala. However, the underlying mechanism based on the basic pharmacological function of duloxetine-regulation on serotonin (5-HT) and norepinephrine (NE) remains unclear. Here, we found that 5-HT level in platelet-poor plasma (PPP) was decreased but NE level in plasma was increased in rats exposed to WIRS, while pretreatment with duloxetine increased 5-HT in PPP dose-dependently and decreased NE in plasma of rats after WIRS. We further showed that depletion of 5-HT by 4-chloro-DL-phenylalanine (PCPA) aggravated gastric mucosa damage and supplement of 5-HT alleviated gastric ulcers induced by WIRS. Blockade of NE receptors also mitigated the stress gastric ulcers. Using adrenalectomy and chemical blocking, we identified that it was NE from adrenal medulla rather than sympathetic nerve that was more critical in the gastroprotection of duloxetine, and intriguingly, glucocorticoid did not make a difference in WIRS-provoked gastric ulcers as a classic stress hormone. Together, our work demonstrated prophylactic protection of duloxetine from the stress gastric ulcer depended on enhancing peripheral 5-HT content and reducing NE from adrenal medulla, which provided insight into treatments of WIRS-induced gastric ulcer.

Milnacipran Ameliorates Executive Function Impairments following Frontal Lobe Traumatic Brain Injury in Male Rats: A Multimodal Behavioral Assessment

Traumatic brain injuries (TBIs) affect more than 10 million patients annually worldwide, causing long-term cognitive and psychosocial impairments. Frontal lobe TBIs commonly impair executive function, but laboratory models typically focus primarily on spatial learning and declarative memory. We implemented a multi-modal approach for clinically relevant cognitive-behavioral assessments of frontal lobe function in rats with TBI and assessed treatment benefits of the serotonin-norepinephrine reuptake inhibitor, milnacipran (MLN). Two attentional set-shifting tasks (AST) evaluated cognitive flexibility via the rats' ability to locate food-based rewards by learning, unlearning, and relearning sequential rule sets with shifting salient cues. Adult male rats reached stable pre-injury operant AST (oAST) performance in 3-4 weeks, then were isoflurane-anesthetized, subjected to a unilateral frontal lobe controlled cortical impact (2.4 mm depth, 4 m/sec velocity) or Sham injury, and randomized to treatment conditions. Milnacipran (30 mg/kg/day) or vehicle (VEH; 10% ethanol in saline) was administered intraperitoneally via implanted osmotic minipumps (continuous infusions post-surgery, 60 μL/h). Rats had a 10-day recovery post-TBI/Sham before performing light/location-based oAST for 10 days and, subsequently, odor/media-based digging AST (dAST) on the last test day (26-27 days post-injury) before sacrifice. Both AST tests revealed significant deficits in TBI+VEH rats, seen as elevated total trials and errors (p < 0.05), which generally normalized in MLN-treated rats (p < 0.05). This first simultaneous dual AST assessment demonstrates oAST and dAST are sufficiently sensitive and robust to detect subtle attentional and cognitive flexibility executive impairments after frontal lobe TBI in rats. Chronic MLN administration shows promise for attenuation of post-TBI executive function deficits, thus meriting further investigation.

Role of central serotonin and noradrenaline interactions in the antidepressants' action: Electrophysiological and neurochemical evidence

The development of antidepressant drugs, in the last 6 decades, has been associated with theories based on a deficiency of serotonin (5-HT) and/or noradrenaline (NA) systems. Although the pathophysiology of major depression (MD) is not fully understood, numerous investigations have suggested that treatments with various classes of antidepressant drugs may lead to an enhanced 5-HT and/or adapted NA neurotransmissions. In this review, particular morpho-physiological aspects of these systems are first considered. Second, principal features of central 5-HT/NA interactions are examined. In this regard, the effects of the acute and sustained antidepressant administrations on these systems are discussed. Finally, future directions including novel therapeutic strategies are proposed.

Brain estrogen alters the effects of the antidepressant sertraline in middle-aged female and male mice

Estrogens are important in regulating mood, especially for females. However, whether tissue-specific estrogen, such as brain estrogen, contributes to the effects of antidepressant treatment has not been determined. The present study used middle-aged aromatase gene knockout (Ar^-/-) mice or overexpression (Thy1-Ar; hGFAP-Ar) mice as brain estrogen models to investigate whether brain estrogen synthesis alters the anti-depressive behaviors of sertraline treatment. Our results showed that depletion of brain estrogen increased depressive-like behavior in females, and elevated brain estrogen reduced depression-like behavior, regardless of sex. These genotype-related behaviors correlated with alterations of monoamine metabolism in the hippocampus (HPC) and the prefrontal cortex (PFC). We also demonstrated that male and female Ar^-/- mice exhibited an attenuation of sertraline-induced anti-depressive behaviors compared to wild-type (WT) mice. The present data suggest that brain estrogen alters depressive-like behaviors and changes the effectiveness of antidepressants in middle-aged mice, regardless of sex.

SNRIs achieve faster antidepressant effects than SSRIs by elevating the concentrations of dopamine in the forebrain

Major depressive disorder (MDD) is a severe mental disorder with a high disability rate worldwide. Selective serotonin reuptake inhibitors (SSRIs) and serotonin and norepinephrine reuptake inhibitors (SNRIs) are the most common agents for antidepressant use. SSRIs and SNRIs are believed to achieve antidepressant effects through the activation of serotonergic or noradrenergic systems. However, whether the dopaminergic system is involved remains unclear. In our study, a genetically encoded dopamine sensor and in vivo fiber photometry recordings were used to measure the dopamine concentrations in the medial prefrontal cortex (mPFC) and nucleus accumbens (NAc) after acute intraperitoneal injection of SSRIs or SNRIs. Combined with the behavioral tests, we found that SNRIs increased dopamine concentrations in both the mPFC and the NAc and showed faster antidepressant effects than SSRIs. To verify the enhanced dopamine levels induce the faster antidepressant effects of SNRIs, we employed dopamine receptor antagonists to specifically block the dopaminergic function. The results showed that the faster antidepressant effects of SNRIs were weakened by the dopamine receptor antagonists. Altogether, our study reveals that SNRIs achieve faster antidepressant effects than SSRIs by elevating the dopamine concentrations in the mPFC and the NAc. Our work proposes further mechanisms for the first-line antidepressants, which provides more basis for clinical treatments. This article is part of the special issue on Stress, Addiction and Plasticity.

Monoaminergic balances predict non-depression-like phenotype in Learned Helplessness Paradigm

Monoamine neuronal system abnormality is hypothesized to be the neurochemical pathology in depression, as it is supported by the efficacy of conventional antidepressants. The learned helplessness paradigm generates depression-like (LH) and non-depression-like (non-LH) behavioral models. Examination of the neurochemical states accompanying such distinct behavioral phenotypes can facilitate investigations of the mechanisms underlying resilience and the search for new strategies for depression prevention and therapy. Here, we measured the levels of monoamines, including noradrenaline (NA), serotonin (5-HT), and dopamine (DA), and their metabolites in the medial prefrontal cortex (mPFC), orbitofrontal cortex (OFC), hippocampus, nucleus accumbens (NAc), amygdala, and striatum in LH, non-LH, and non-manipulated (naïve) rats. Compared with LH rats, non-LH rats showed lower 3-methoxy-4-hydroxyphenylglycol (MHPG) levels and NA turnovers in the amygdala and higher 5-HT levels in the NAc. Compared with naïve rats, non-LH rats showed increased DA and homovanillic acid (HVA) levels in the amygdala and increased 5-hydroxyindoleacetic acid (5-HIAA) levels in the hippocampus and NAc, whereas LH rats exhibited increased HVA levels and DA turnovers in the hippocampus, decreased 5-HIAA levels in the mPFC, increased DA turnovers in the OFC, and decreased DA turnovers in the amygdala. Comparison between LH and non-LH suggest that suppressed amygdaloid NA activity and elevated 5-HT activity in the NAc are related to stress resilience. Changes that occurred in LH or non-LH rats when compared with those in naïve rats suggest that suppressed DA activity in the hippocampus and OFC; elevated DA activity in the amygdala; and facilitated 5-HT activity in the hippocampus, mPFC, and NAc are phenomena related to the expression of a non-depression-like phenotype.

Sex Differences in Antidepressant Effect of Sertraline in Transgenic Mouse Models

The main purpose of this study is to explore sex differences in the antidepressant effect of sertraline in genetic knockout or overexpression estrogen-synthesizing enzyme aromatase (Ar) gene mouse models in the forced swim test (FST). Our results demonstrated a significant reduction of depression-like behavior in the mice with overexpression of brain aromatase (Thy1-Ar) compared to sex- and age-matched Ar^+/− mice or wild type control mice. Using HPLC analysis, we also found an association between the brain estrogen-related antidepressive behavior and the regulation of serotonin (5-HT) system. Interestingly, a single dose administration of sertraline (10 mg/kg, i.p.) induced reduction of immobility time was found in all genotypes, except male Ar^+/− mice. While the underlying mechanisms of sex-specific response on antidepressive effect of sertraline remain to be investigated, our data showed that female mice appear to be more sensitive to sertraline-induced changes of 5-HT system than male mice in the prefrontal cortex (PFC) and the hippocampus (HPC). Further investigation of sex-specific effect of brain estrogen on antidepressant is needed.

Study of Sex Differences in Duloxetine Efficacy for Depression in Transgenic Mouse Models

Clinical evidences show sex differences in risk of developing depressive disorders as well as effect of antidepressants in depression treatment. However, whether such a sex-dependent risk of depression and efficacy of antidepressants is dependent on endogenous estrogen level remain elusive. The aim of this study is to explore the molecular mechanisms of sex differences in antidepressant duloxetine. In the present study, we used genetic knockout or overexpression estrogen-synthesizing enzyme aromatase (Ar) gene as models for endogenous estrogen deficiency and elevation endogenous estrogen, respectively, to examine the anti-depressive efficacy of duloxetine in males and females by force swimming test (FST). We also measured the sex-specific effect of duloxetine on dopamine and serotonin (5-HT) metabolisms in frontal cortex and hippocampus (HPC). Elevation of brain endogenous estrogen in male and female mice showed a reduction of immobility time in FST compared to control mice. Estrogen deficiency in females showed poor response to duloxetine treatment compared to sex-matched wildtype (WT) or aromatase transgenic mice. In contrast, male mice with estrogen deficiency showed same anti-depressive response to duloxetine treatments as aromatase transgenic mice. Our data showed that the sex different effect of endogenous estrogen on duloxetine-induced anti-depressive behavioral change is associated with brain region-specific changes of dopamine (DA) and 5-HT system. Endogenous estrogen exerts antidepressant effects in both males and females. Lacking of endogenous estrogen reduced antidepressive effect of duloxetine in females only. The endogenous estrogen level alters 5-HT system in female mainly, while both DA and 5-HT metabolisms were regulated by endogenous estrogen levels after duloxetine administration.

Fluoxetine exposure impacts boldness in female Siamese fighting fish, Betta splendens

The present study examined the effects of the selective serotonin reuptake inhibitor, fluoxetine, on the behavior of female Siamese fighting fish, Betta splendens, in three different boldness assays (Empty Tank, Novel Environment, Social Tendency). When females were unexposed to fluoxetine, boldness was consistent within a context and correlated across assays. Fluoxetine exposure affected behavior within and among individuals on multiple levels. Exposure reduced overall boldness levels, made females behave in a less consistent manner, and significantly reduced correlations over time and across contexts. Fluoxetine exerted its effects on female Betta splendens behavior in a dose-dependent fashion and these effects persisted even after females were housed in clean water. If fluoxetine exposure impacts behaviors such as exploration that are necessary to an individual’s success, this may yield evolutionary consequences. In conclusion, the results show that fluoxetine exposure alters behavior beyond the level of overall response and highlights the importance of studying the behavioral effects of inadvertent pharmaceutical exposure in multiple contexts and with different dosing regimes.

Distinct effects of the serotonin-noradrenaline reuptake inhibitors milnacipran and venlafaxine on rat pineal monoamines

Monoamine systems are involved in the pathology and therapeutic mechanism of depression. The pineal gland contains large amounts of serotonin as a precursor for melatonin, and its activity is controlled by noradrenergic sympathetic nerves. Pineal diurnal activity and its release of melatonin are relevant to aberrant states observed in depression. We investigated the effects on pineal monoamines of serotonin-noradrenaline reuptake inhibitors, which are widely used antidepressants. Four days of milnacipran treatment led to an increase in noradrenaline and serotonin levels, whereas 4 days of venlafaxine treatment reduced 5-hydroxyindoleacetic acid levels; both agents induced an increase in dopamine levels. Our data suggest that milnacipran increases levels of the precursor for melatonin synthesis by facilitating the noradrenergic regulation of pineal activity and that venlafaxine inhibits serotonin reuptake into noradrenergic terminals on the pineal gland.

Sertraline Induced Galactorrhea

There is limited literature reporting galactorrhea with antidepressants, including selective serotonin reuptake inhibitors. In this case report, a patient with adjustment disorder who developed galactorrhea with sertraline was presented.

The antidepressant venlafaxine disrupts brain monoamine levels and neuroendocrine responses to stress in rainbow trout

Venlafaxine, a serotonin-norepinephrine reuptake inhibitor, is a widely prescribed antidepressant drug routinely detected in the aquatic environment. However, little is known about its impact on the physiology of nontarget organisms. We tested the hypothesis that venlafaxine perturbs brain monoamine levels and disrupts molecular responses essential for stress coping and feeding activity in fish. Rainbow trout (Oncorhynchus mykiss) were exposed to waterborne venlafaxine (0.2 and 1.0 μg/L) for 7 days. This treatment elevated norepinephrine, serotonin, and dopamine levels in the brain in a region-specific manner. Venlafaxine also increased the transcript levels of genes involved in stress and appetite regulation, including corticotropin releasing factor, pro-opiomelanocortin B, and glucose transporter type 2 in distinct brain regions of trout. The drug treatment reduced the total feed consumed per day, but did not affect the feeding behavior of the dominant and subordinate fish. However, the subordinate fish from the venlafaxine-exposed group had significantly higher plasma cortisol levels compared to the subordinate fish in the control group. Collectively, our results demonstrate that venlafaxine, at environmentally realistic levels, is a neuroendocrine disruptor, impacting the stress and feeding responses in rainbow trout. We propose the midbrain region as a key target for venlafaxine impact and the mode of action involves abnormal monoamine content in trout.

Effect of Ginkgo biloba extract on lipopolysaccharide-induced anhedonic depressive-like behavior in male rats

The peripheral administration of lipopolysaccharide (LPS) induces depressive-like behavior. Anhedonia is a core symptom of depression, defined as a loss of the capacity to experience pleasure. The present study used the sucrose preference test to investigate the influence of Ginkgo biloba extract (EGb 761) on LPS-induced anhedonia in male rats. The animals were randomly divided into four groups: (I) vehicle + saline, (II) vehicle + LPS, (III) EGb 761 + saline, and (IV) EGb 761 + LPS. Saline or LPS (100 µg/kg) was administered intraperitoneally 2 h before the sucrose preference test. Sucrose consumption was recorded 2, 4, 6, 13, and 24 h after 100 µg/kg of LPS or saline injection in the dark phase of the light/dark cycle. Dopamine and serotonin levels in the nucleus accumbens were measured. Our results indicated that the vehicle + LPS group exhibited a significant decrease in sucrose intake compared with the vehicle + saline group. The EGb 761 + LPS group showed more sucrose and food consumption than the vehicle + LPS group. Additionally, compared with the EGb 761 + LPS group, the vehicle + LPS group had less dopamine levels in the nucleus accumbens. Treatment with EGb 761 had no effect on water intake. Our results suggest that EGb 761 may be useful for reducing anhedonic depressive-like behavior.

The Combination of Antidepressant Duloxetine with Piracetam in Mice does not Produce Enhancement of Nootropic Activity

There is a strong association between depression and memory impairment. The present study aims to assess the nootropic activity of duloxetine and piracetam combination. Male Swiss Albino mice were divided randomly into 4 groups. Treatment of normal saline (10 ml/kg), duloxetine (10 mg/kg), piracetam (100 mg/kg), and duloxetine (5 mg/kg) plus piracetam (50 mg/kg) were given through intra-peritoneal route to group I-IV, respectively. Transfer latency in elevated plus maze (EPM) and time spent in target quadrant in Morris water maze (MWM) were recorded. Estimation of brain monoamines in hippocampus, cerebral cortex, and whole brain were done using HPLC with fluorescence detector. Piracetam treated group showed significant decrease in transfer latency in EPM and increase in time spent in target quadrant recorded in MWM. Combination treated group failed to produce statistically significant nootropic effect in both EPM and MWM. Combination treated group failed to increase brain monoamine levels when compared against duloxetine and piracetam treated groups, separately. But there was exception of significant increase in norepinephrine levels in hippocampi when compared against duloxetine treated group. Results indicate no cognitive benefits with piracetam plus duloxetine combination. These findings can be further probed with the aim of understanding the interaction between duloxetine and piracetam as a future endeavor.

Environmental concentrations of the selective serotonin reuptake inhibitor fluoxetine impact specific behaviors involved in reproduction, feeding and predator avoidance in the fish Pimephales promelas (fathead minnow)

Pharmaceuticals and personal care products (PPCPs) have been found in surface waters worldwide, but little is understood of their effects on the wildlife that inhabit these waters. Fluoxetine (Prozac; Eli Lilly), a highly prescribed selective serotonin reuptake inhibitor (SSRI), is a commonly found PPCP in surface water. The purpose of this project was to determine if environmentally relevant concentrations of fluoxetine impact behavior that is important for population survival in native fish species, including reproduction, feeding and predator avoidance. Chronic 4-week exposures were conducted with doses ranging from 100 ng/L to 100 μg/L to cover a range of environmentally relevant concentrations up to higher concentrations comparable to other published studies with the same drug that have documented various physiological impacts. Pimephales promelas (fathead minnow), a species native to North America, was used as it conducts a range of specific mating behaviors and therefore serves as an excellent model of specific impacts on brain function. Fluoxetine concentrations as low as 1 μg/L, a concentration that has been found in many freshwater environments, were found to significantly impact mating behavior, specifically nest building and defending in male fish. Males were also found to display aggression, isolation, and repetitive behaviors at higher concentrations. Female mating behavior was largely unaffected. In addition, predator avoidance behaviors in males and females were also impacted at 1 μg/L. Feeding was impacted at 10 μg/L and in the highest exposure (100 μg/L), egg production was limited by deaths of females due to significant male aggressive behaviors in the first two weeks of exposure. Specific behavioral changes occurred at each concentration (most noticeably 1 μg/L and 100 μg/L) indicating a dose dependent effect that triggered different responses at lower exposures versus higher exposures or differential impacts of dose depending on brain region. Length of exposure also had an impact on aggressive behavior. Changes in hormone levels, indicating significant neuroendocrine changes, suggested as a mechanism of response in higher dose and acute studies, were not linked to changes in behaviors at the doses used in this study. This research provides detailed data on how exposures to fluoxetine impact specific fish behaviors and reproduction and that the effects are dose dependent.

Perinatal exposure to bisphenol A enhances contextual fear memory and affects the serotoninergic system in juvenile female mice

Perinatal exposure to bisphenol A (BPA), an endocrine-disrupting chemical, affects the central nervous system, including effects on emotional responses and neurotransmitter release. In this study, we investigated the effects of BPA (250 ng/kg/day, from gestational day 10 to postnatal day 20) on fear memory and serotonin (5-HT) metabolites in the brain using contextual fear conditioning (FC) and high-performance liquid chromatography (HPLC), respectively, in adult and juvenile mice of both sexes. Furthermore, we studied the effects of BPA on the gene expression of 5-HT metabolite-related enzymes and 5-HT receptors using quantitative real-time RT PCR in the brains of juvenile females. BPA enhanced fear memory and increased serotonin metabolite (5-HIAA) levels and 5-HIAA/5-HT in the hippocampus, the striatum, the midbrain, the pons, and the medulla oblongata of juvenile female mice. In contrast, alterations in those areas were much smaller in adult females and in both juvenile and adult males. Furthermore, BPA induced increases in the expression levels of Tph2, Slc6a4, and Maoa mRNA in the hippocampus of juvenile females, indicating that BPA induces hyper 5-HT turnover in the hippocampus. Our results suggest that perinatal exposure to a low dose of BPA enhances fear memory and the 5-HTergic system in juvenile mice.

Sertraline exposure leads to small left heart syndrome in adult mice

BACKGROUND

Sertraline, a selective serotonin reuptake inhibitor (SSRI), is the most commonly prescribed therapy for maternal depression. Epidemiologic studies have linked SSRI exposure with decreased fetal growth, altered autonomic regulation, and cardiac malformations. We hypothesized that SSRI exposure decreases left-ventricular (LV) volumes and increases adult sympathetic nervous system activation, resulting in increased adult heart rates.

METHODS

C57BL/6 mice received saline or sertraline (5 or 15 mg/kg/day i.p.) on postnatal days 1-14. Adult phenotypes were assessed at 5 mo.

RESULTS

Sertraline-exposed mice had smaller LV internal diameters in diastole (control 4.0 ± 0.1 mm, SSRI 3.7 ± 0.1 mm, P < 0.05), decreased stroke volumes (control 46 ± 2.6 µl, SSRI 37 ± 2.3 µl, P < 0.05), higher heart rates (control 530 ± 13 beats per minute (bpm), SSRI 567 ± 6 bpm, P <0.05), and increased urinary excretion of noradrenaline (control 174 ± 29.4 ng/ml, SSRI 276 ± 35.1 ng/ml, P < 0.05). These changes were associated with increased cerebral serotonin transporter (5-HTT) expression.

CONCLUSION

Neonatal sertraline exposure causes long-term changes in cardiac morphology and physiology. We speculate that early-life SSRI exposure impairs cardiomyocyte growth and central serotonin signaling, leading to a small left heart syndrome in adult mice.

Neutralization of endogenous digitalis-like compounds alters catecholamines metabolism in the brain and elicits anti-depressive behavior

Depressive disorders are among the world's greatest public health problems. Na(+), K(+)-ATPase is the established receptor for the steroidal digitalis-like compounds (DLC). Alteration in brain Na(+), K(+)-ATPase and DLC have been detected in depressive disorders raising the hypothesis of their involvement in these pathology. The present study was designed to further elaborate this hypothesis by investigating the behavioral and biochemical consequences of neutralization in brain DLC activity attained by anti-ouabain antibodies administrations, in normal Sprague-Dawley (SD) and in the Flinders Sensitive Line (FSL) of genetically depressed rats. Chronic i.c.v. administration of anti-ouabain antibodies to FSL rats elicited anti-depressive behavior. Administration of anti-ouabain antibodies intracerebroventriculary (i.c.v.) to SD rats significantly changed the levels of catecholamines and their metabolites in the hippocampus, ventral tegmentum and nucleus accumbence. These results are in accordance with the notion that endogenous DLC may be involved in the manifestation of depressive disorders and suggests that alteration in their levels may be of significant therapeutic value.

Duloxetine's modest short-term influences in subcortical structures of first episode drug-naïve patients with major depressive disorder and panic disorder

We developed this study to follow up the hanges in subcortical structures after 6 weeks' treatment with therapy of duloxetine in first episode drug-naïve patients with major depressive disorder and panic disorder. Fifteen patients received duloxetine 60mg/d therapy for 6 weeks and achieved remission. They all underwent structural magnetic resonance imaging (MRI) of the brain at baseline and week 6. Fifteen healthy controls were also scanned twice at baseline and week 6 to exclude possible biases. Structural MRI data were preprocessed with FMRIB's Integrated Registration and Segmentation Tool function (FIRST version 1.2) of FSL (FMRIB Software Library; version 4.1.1) to perform subcortical segmentations of the brain using a shape and appearance model. Nonparametric corrections of these structural volumes in an F-test between pre- and post-treatment were used to identify the changes after duloxetine therapy. A false discovery correction of the F-test by FIRST was also performed. A paired t-test using SPSS was applied to confirm the changes in these structures. The patients had consistent changes of volumes in bilateral nucleus accumbens, left putamen, left hippocampus and brainstem after 6 weeks of treatment with duloxetine. There were no consistent changes in other subcortical structures. There were modest increases of the volumes of the above areas, which were not significant after false discovery correction by FIRST F-test comparisons. The volumetric increases were correlated with responses of clinical symptoms. The results suggested that duloxetine possibly contributed to modest increases in several subcortical areas of these patients with remission.

Milnacipran in panic disorder with agoraphobia and major depressive disorder: a case report

A 51-year-old woman had panic disorder with agoraphobia and major depressive disorder sequentially. The aforementioned symptoms subsided significantly after treatment with milnacipran, 125 mg, administered daily for 2 months. However, panic attacks with agoraphobia were noted frequently when she tapered down milnacipran to 50 mg daily. She consequently experienced depression that gradually increased in degree, with poor energy, poor sleep, thoughts of helplessness, and ideas of death. After administration of a daily dose of 125 mg of milnacipran for 1 month, her panic attacks with agoraphobia and depressed mood were again alleviated. The present report shows significant effects of milnacipran on the comorbidity of panic disorder with agoraphobia and major depressive disorder.

Two-week administration of the combined serotonin-noradrenaline reuptake inhibitor duloxetine augments functioning of mesolimbic incentive processing circuits

BACKGROUND

Anhedonia and lack of motivation are core symptoms of major depressive disorder (MDD). Neuroimaging studies in MDD patients have shown reductions in reward-related activity in terminal regions of the mesolimbic dopamine (DA) system, such as the ventral striatum. Monoamines have been implicated in both mesolimbic incentive processing and the mechanism of action of antidepressant drugs. However, not much is known about antidepressant effects on mesolimbic incentive processing in humans, which might be related to the effects on anhedonia.

METHODS

To investigate the short-term effects of antidepressants on reward-related activity in the ventral striatum, we investigated the effect of the combined serotonin-norepinephrine reuptake inhibitor duloxetine. Healthy volunteers underwent functional magnetic resonance imaging in a randomized, double-blind, placebo-controlled, crossover study. After taking duloxetine (60 mg once a day) or placebo for 14 days, participants completed a monetary incentive delay task that activates the ventral striatum during reward anticipation.

RESULTS

Our results (n = 19) show enhanced ventral striatal responses after duloxetine administration compared with placebo. Moreover, this increase in ventral striatal activity was positively correlated with duloxetine plasma levels.

CONCLUSIONS

This is the first study to demonstrate that antidepressants augment neural activity in mesolimbic DA incentive processing circuits in healthy volunteers. These effects are likely caused by the increase in monoamine neurotransmission in the ventral striatum. Our findings suggest that antidepressants may alleviate anhedonia by stimulating incentive processing.

A new strategy for antidepressant prescription

From our research and literature search we propose an understanding of the mechanism of action of antidepressants treatments (ADTs) that should lead to increase efficacy and tolerance. We understand that ADTs promote synaptic plasticity and neurogenesis. This promotion is linked with stimulation of dopaminergic receptors. Previous evidence shows that all ADTs (chemical, electroconvulsive therapy, repetitive transcranial magnetic stimulation, sleep deprivation) increase at least one monoamine neurotransmitter serotonin (5-HT), noradrenaline (NA) or dopamine (DA); this article focuses on DA release or turn-over in the frontal cortex. DA increased dopaminergic activation promotes synaptic plasticity with an inverted U shape dose–response curve. Specific interaction between DA and glutamate is mediated by D1 receptor subtypes and Glutamate (NMDA) receptors with neurotrophic factors likely to play a modulatory role. With the understanding that all ADTs have a common, final, DA-ergic stimulation that promotes synaptic plasticity we can predict that (1) AD efficiency is related to the compound strength for inducing DA-ergic stimulation. (2) ADT efficiency presents a therapeutic window that coincides with the inverted U shape DA response curve. (3) ADT delay of action is related to a “synaptogenesis and neurogenesis delay of action.” (4) The minimum efficient dose can be found by starting at a low dosage and increasing up to the patient response. (5) An increased tolerance requires a concomitant prescription of a few ADTs, with different or opposite adverse effects, at a very low dose. (6) ADTs could improve all diseases with cognitive impairments and synaptic depression by increasing synaptic plasticity and neurogenesis.

Sertraline increases extracellular levels not only of serotonin, but also of dopamine in the nucleus accumbens and striatum of rats

Selective serotonin reuptake inhibitors (SSRIs) are a first-line treatment for depression. Recent reports in the literature describe differences in antidepressant effects among SSRIs. Although each SSRI apparently has different pharmacological actions aside from serotonin reuptake inhibition, the relations between antidepressant effects and unique pharmacological properties in respective SSRIs remain unclear. This study was designed to compare abilities of three systemically administered SSRIs to increase the extracellular levels of serotonin, dopamine, and noradrenaline acutely in three brain regions of male Sprague-Dawley rats. We examined effects of sertraline, fluvoxamine, and paroxetine on extracellular serotonin, dopamine, and noradrenaline levels in the medial prefrontal cortex, nucleus accumbens and striatum of rats using in vivo microdialysis. Dialysate samples were collected in sample vials every 20 min for 460 min. Extracellular serotonin, dopamine, and noradrenaline levels were determined using high-performance liquid chromatography with electrochemical detection. All SSRI administrations increased extracellular serotonin levels in all regions. Only sertraline administration increased extracellular dopamine concentrations in the nucleus accumbens and striatum. All SSRI administrations increased extracellular noradrenaline levels in the nucleus accumbens, although fluvoxamine was less effective. These results suggest that neurochemical differences account for the differences in clinical antidepressant effects among SSRIs.

Milnacipran: a unique antidepressant?

Tricyclic antidepressants (TCAs) are among the most effective antidepressants available, although their poor tolerance at usual recommended doses and toxicity in overdose make them difficult to use. While selective serotonin reuptake inhibitors (SSRIs) are better tolerated than TCAs, they have their own specific problems, such as the aggravation of sexual dysfunction, interaction with coadministered drugs, and for many, a discontinuation syndrome. In addition, some of them appear to be less effective than TCAs in more severely depressed patients. Increasing evidence of the importance of norepinephrine in the etiology of depression has led to the development of a new generation of antidepressants, the serotonin and norepinephrine reuptake inhibitors (SNRIs). Milnacipran, one of the pioneer SNRIs, was designed from theoretic considerations to be more effective than SSRIs and better tolerated than TCAs, and with a simple pharmacokinetic profile. Milnacipran has the most balanced potency ratio for reuptake inhibition of the two neurotransmitters compared with other SNRIs (1:1.6 for milnacipran, 1:10 for duloxetine, and 1:30 for venlafaxine), and in some studies milnacipran has been shown to inhibit norepinephrine uptake with greater potency than serotonin (2.2:1). Clinical studies have shown that milnacipran has efficacy comparable with the TCAs and is superior to SSRIs in severe depression. In addition, milnacipran is well tolerated, with a low potential for pharmacokinetic drug-drug interactions. Milnacipran is a first-line therapy suitable for most depressed patients. It is frequently successful when other treatments fail for reasons of efficacy or tolerability.