Chronic social defeat stress induces sustained synaptic structural changes in the prefrontal cortex and amygdala.

Previous studies show that chronic stress induces synaptic structural alterations in brain regions involved in emotional processing such as the prefrontal cortex (PFC) and the basolateral amygdala (BLA). Yet, these studies are based mainly in animal exposure to unpredictable stressors or to restraint stress. On the other hand, studies using the chronic social defeat stress (CSDS), a relevant model of depression based on social conflict, are lacking. Here we aim to study the acute (24 h after CSDS) and long-term (one month after CSDS) effects of CSDS on dendritic and synaptic structures in the PFC and BLA of C57BL/6 mice. Specifically, BLA and PFC dendritic spine densities as well as BLA arborisation were analysed. Subsequently, we investigate in these regions the synaptic response to a friendly (interaction with a same strain mouse) or a fearful (interaction with a dominant strain mouse) social stimulus. Spine densities of the apical dendrites from the PFC pyramidal neurons were decreased by CSDS in the long-term (one month after CSDS). In addition, CSDS increased BLA stellate neurons spine density in the short-term (24 h after CSDS) and dendritic arborisation in the long-term. Moreover, long-term CSDS mice exposed to a fearful stimulus experienced a marked social avoidance and showed a significant increase in the expression of the immature form of the brain derived neurotrophic factor (proBDNF) in the amygdala. Taken together these results suggest the existence of persistent neuronal adaptations in the PFC and BLA in socially defeated mice. Specifically, spine density retraction in the PFC and increased BLA dendritic arborisation could represent an adaptive structural change allowing rapid expression of synaptic markers in response to fearful experiences.

SIRT2 inhibition reverses anhedonia in the VGLUT1+/- depression model.

Some histone deacetylase (HDACs) enzymes have been proposed as epigenetic targets involved in the pathophysiology of depression and antidepressant-like action. Among them, we have recently identified SIRT2, a class III NAD+-dependent HDAC, as being oppositely regulated by stress and antidepressants. Moreover, SIRT2 inhibition has shown antianhedonic-like action in the chronic mild stress model of depression. Here we have extended the study using an alternative model of depression based in a genetic manipulation of glutamate function. Specifically, mice heterozygous for the vesicular glutamate transporter 1 (VGLUT1+/-) were used. Firstly, mRNA expression of the different members of the HDAC superfamily in the prefrontal cortex (PFC) of VGLUT1+/- mice and WT littermates were studied by RT-PCR. Secondly, the effect of repeated treatment with the selective SIRT2 inhibitor 33i and the antidepressant imipramine on anhedonic behaviour of VGLUT1+/- mice was studied by weekly monitoring of sucrose intake. Further, the interaction of 33i towards specific monoaminergic targets such as serotonin or noradrenaline transporters as well as the monoaminooxidase enzyme was studied. The mRNA occurance of the different members of HDAC superfamily was not altered in the PFC of VGLUT1+/- mice. While repeated imipramine showed an anti-anhedonic action in both VGLUT1+/- and WT, the selective SIRT2 inhibitor 33i fully reversed anhedonia of VGLUT1+/-. Further, 33i showed no interaction with the above mentioned monoaminergic molecular targets. These results confirm that SIRT2 inhibition is able to reverse anhedonia in different animal models and highlight the need to further investigate the role of SIRT2 inhibitors as new antidepressant agents.

Chronic stress and antidepressant induced changes in Hdac5 and Sirt2 affect synaptic plasticity.

Changes in histone acetylation could contribute to the pathogenesis of depression and antidepressant therapy. Using the chronic social defeat stress (CSDS) model of depression and different antidepressant treatments we studied the regulation of histone deacetylases (Hdac׳s) and synaptic plasticity markers in the prefrontal cortex (PFC). Further, functional implication of identified Hdac׳s in brain plasticity was explored. Mice were exposed to CSDS (10 days) followed by saline or imipramine (4 weeks). PFC Hdac׳s mRNA abundance was studied and compared to human׳s. Further, protein expression of acetylated histones (AcH3 and AcH4), neuroplasticity markers (CREB and pro-BDNF) and selected Hdac׳s were analyzed. Moreover, other antidepressants (fluoxetine and reboxetine) and selective HDAC inhibitors were studied. CSDS increased Hdac5 and Sirt2 mRNA whereas repeated imipramine did the opposite. Accordingly, stress and imipramine induced opposite changes on AcH3, AcH4 and CREB expression. At protein level, CSDS upregulated nuclear fraction of Hdac5 and repeated imipramine and reboxetine increased its phosphorylated form (p-Hdac5), mainly located in the cytoplasm. Moreover, Sirt2 was downregulated by all monoaminergic antidepressants. Further, repeated treatment with the class IIa Hdac inhibitor MC1568 and the Sirt2 inhibitor 33i for three weeks increased synaptic plasticity in the prefrontal cortex. Our results suggest that Hdac5 and Sirt2 upregulation could constitute stable stress-induced neuronal adaptations. Noteworthy, the SIRT2 upregulation in depressed patients supports the interest of this target for therapeutic intervention. On the other hand, cytoplasmic Hdac5 export and Sirt2 downregulation induced by monoaminergic antidepressants could contribute to the well-known beneficial effects of antidepressants on brain plasticity.

Chronic mild stress and imipramine treatment elicit opposite changes in behavior and in gene expression in the mouse prefrontal cortex.

Many studies suggest that the prefrontal cortex (PFC) is a target limbic region for stress response because a dysfunction here is linked to anhedonia, a decrease in reactivity to rewards, and to anxiety. It is suggested that stress-induced persistent molecular changes in this brain region could bring some light on the mechanisms perpetuating depressive episodes. In order to address this issue, here we have studied the long-term PFC gene expression pattern and behavioral effects induced by a chronic mild stress (CMS) model and antidepressant treatment in mice. CMS was applied to mice for six weeks and imipramine (10mg/kg, i.p.) or saline treatment was administered for five weeks starting from the third week of CMS. Mice were sacrificed one month after CMS and following two weeks after the discontinuation of drug treatment and the PFC was dissected and prepared for gene (mRNA) and protein expression studies. Using the same experimental design, a separate group of mice was tested for anhedonia, recognition memory, social interaction and anxiety. CMS induced a long-term altered gene expression profile in the PFC that was partially reverted by imipramine. Specifically, the circadian rhythm signaling pathway and functions such as gene expression, cell proliferation, survival and apoptosis as well as neurological and psychiatric disorders were affected. Of these, some changes of the circadian rhythm pathway (Hdac5, Per1, and Per2) were validated by RT-PCR and western-blot. Moreover, CMS induced long-lasting anhedonia that was reverted by imipramine treatment. Impaired memory, decreased social interaction and anxiety behavior were also induced by chronic stress. We have identified in the PFC molecular targets oppositely regulated by CMS and imipramine that could be relevant for chronic depression and antidepressant action. Among these, a possible candidate for further investigation could be the circadian rhythm pathway.

Social vs. environmental stress models of depression from a behavioural and neurochemical approach.

Major depression is a mental disorder often preceded by exposure to chronic stress or stressful life events. Recently, animal models based on social conflict such as chronic social defeat stress (CSDS) are proposed to be more relevant to stress-induced human psychopathology compared to environmental models like the chronic mild stress (CMS). However, while CMS reproduces specifically core depressive symptoms such as anhedonia and helplessness, CSDS studies rely on the analysis of stress-induced social avoidance, addressing different neuropsychiatric disorders. Here, we study comparatively the two models from a behavioural and neurochemical approach and their possible relevance to human depression. Mice (C57BL/6) were exposed to CMS or CSDS for six weeks and ten days. Anhedonia was periodically evaluated. A battery of test applied during the fourth week after the stress procedure included motor activity, memory, anxiety, social interaction and helplessness. Subsequently, we examined glutamate, GABA, 5-HT and dopamine levels in the prefrontal cortex, hippocampus and brainstem. CMS induced a clear depressive-like profile including anhedonia, helplessness and memory impairment. CSDS induced anhedonia, hyperactivity, anxiety and social avoidance, signs also common to anxiety and posttraumatic stress disorders. While both models disrupted the excitatory inhibitory balance in the prefrontal cortex, CMS altered importantly this balance in the brainstem. Moreover, CSDS decreased dopamine in the prefrontal cortex and brainstem. We suggests that while depressive-like behaviours might be associated to altered aminoacid neurotransmission in cortical and brain stem areas, CSDS induced anxiety behaviours might be linked to specific alteration of dopaminergic pathways involved in rewarding processes.

Chronic social defeat stress model: behavioral features, antidepressant action, and interaction with biological risk factors.

RATIONALE: Chronic social defeat stress (CSDS) has been proposed as a model of depression. However, most CSDS studies rely only on the analysis of stress-induced social avoidance. Moreover, the predictive validity of the model has been poorly analyzed, let alone its interaction with biological risk factors. OBJECTIVES: Here, we explore the validity of CSDS as a depression model. Further, the effect of decreased vesicular glutamate transporter 1 (VGLUT1), as a potential factor enhancing a depressive-like phenotype, was studied. METHODS: Mice were exposed to CSDS (10 days) followed by saline, venlafaxine, fluoxetine, or tianeptine treatment (30 days). The battery of behaviors included motor activity, memory, anxiety, social interaction, helplessness, and anhedonic-like behavior. Moreover, the behavioral effect of CSDS in VGLUT1 heterozygous (VGLUT1+/-) mice was studied, as well as the regulation of VGLUT1 mRNA. RESULTS: CSDS induced anhedonia, helplessness, hyperactivity, anxiety, social avoidance, and freezing, as well as downregulation of VGLUT1 mRNA in the amygdala. Repeated venlafaxine showed antidepressant-like activity and both venlafaxine and tianeptine behaved as effective anxiolytics. CSDS-induced social avoidance was reverted by tianeptine. Fluoxetine failed to revert most of the behavioral alterations. VGLUT1+/- mice showed an enhanced vulnerability to stress-induced social avoidance. CONCLUSION: We suggest that CSDS is not a pure model of depression. Indeed, it addresses relevant aspects of anxiety-related disorders. Firstly, CSDS-induced anhedonia and social avoidance are not associated in this model. Moreover, CSDS might be affecting brain areas mainly involved in the processing of social behavior, such as the amygdala, where the glutamatergic mechanism could play a key role.

Stress-induced anhedonia is associated with an increase in Alzheimer's disease-related markers.

BACKGROUND AND PURPOSE: Stress is believed to be associated with the development of neuropsychiatric disorders, including Alzheimer's disease (AD). We have studied mechanisms implicated in vulnerability to stress and the relationship with changes in AD-related markers. EXPERIMENTAL APPROACH: Anhedonia induced by a chronic mild stress (CMS) procedure, applied for 6 weeks, was used to select rats vulnerable or resistant to stress. Sucrose intake, the Porsolt forced swimming test and cognitive deficits in the novel object recognition test (NORT) were used to characterize vulnerable and resilient rats. The antidepressant venlafaxine (20 mg·kg(-1) p.o.) or saline was administered daily during the last 2 weeks of CMS. Biochemical markers affected by stress, PKB, ERK and synaptophysin, and those associated with AD, amyloid ß-protein (Aß), ß-secretase (BACE1) and τ phosphorylation, were measured in the hippocampus. KEY RESULTS: After CMS, 40% of rats were resistant to the development of anhedonia (CMS-resistant to stress), whereas the remaining were responsive [CMS-anhedonic (CMSA)]. Only CMSA rats displayed significant increases in immobility time in the forced swimming test and cognitive deficits in the NORT, and significant decreases in synaptophysin, phosphorylated PKB and phosphorylated ERK1/2 expression in the hippocampus. Increased levels of Aß40, BACE1 and τ phosphorylation were also found only in CMSA rats. All these effects in CMSA rats were reverted by treatment with venlafaxine. CONCLUSIONS AND IMPLICATIONS: Vulnerability to stress might constitute a risk factor for the development of AD, and pharmacological treatment with venlafaxine may represent a therapeutic strategy for the treatment of stress-related disorders, including AD.

Chronic stress and impaired glutamate function elicit a depressive-like phenotype and common changes in gene expression in the mouse frontal cortex.

Major depression might originate from both environmental and genetic risk factors. The environmental chronic mild stress (CMS) model mimics some environmental factors contributing to human depression and induces anhedonia and helplessness. Mice heterozygous for the synaptic vesicle protein (SVP) vesicular glutamate transporter 1 (VGLUT1) have been proposed as a genetic model of deficient glutamate function linked to depressive-like behaviour. Here, we aimed to identify, in these two experimental models, gene expression changes in the frontal cortex, common to stress and impaired glutamate function. Both VGLUT1(+/-) and CMS mice showed helpless and anhedonic-like behavior. Microarray studies in VGLUT1(+/-) mice revealed regulation of genes involved in apoptosis, neurogenesis, synaptic transmission, protein metabolic process or learning and memory. In addition, RT-PCR studies confirmed gene expression changes in several glutamate, GABA, dopamine and serotonin neurotransmitter receptors. On the other hand, CMS affected the regulation of 147 transcripts, some of them involved in response to stress and oxidoreductase activity. Interestingly, 52 genes were similarly regulated in both models. Specifically, a dowregulation in genes that promote cell proliferation (Anapc7), cell growth (CsnK1g1), cell survival (Hdac3), and inhibition of apoptosis (Dido1) was observed. Genes linked to cytoskeleton (Hspg2, Invs), psychiatric disorders (Grin1, MapK12) or an antioxidant enzyme (Gpx2) were also downregulated. Moreover, genes that inhibit the MAPK pathways (Dusp14), stimulate oxidative metabolism (Eif4a2) and enhance glutamate transmission (Rab8b) were upregulated. We suggest that these genes could form part of the altered "molecular context" underlying depressive-like behaviour in animal models. The clinical relevance of these findings is discussed.

Shared changes in gene expression in frontal cortex of four genetically modified mouse models of depression.

This study aimed to identify whether genetic manipulation of four systems implicated in the pathogenesis of depression converge on shared molecular processes underpinning depression-like behaviour in mice. Altered 5HT function was modelled using the 5-HT transporter knock out mouse, impaired glucocorticoid receptor (GR) function using an antisense-induced knock down mouse, disrupted glutamate function using a heterozygous KO of the vesicular glutamate transporter 1 gene, and impaired cannabinoid signalling using the cannabinoid 1 receptor KO mouse. All 4 four genetically modified mice were previously shown to show exaggerated helpless behaviour compared to wild-type controls and variable degrees of anxiety and anhedonic behaviour. mRNA was extracted from frontal cortex and hybridised to Illumina microarrays. Combined contrast analysis was used to identify genes showing different patterns of up- and down-regulation across the 4 models. 1823 genes were differentially regulated. They were over-represented in gene ontology categories of metabolism, protein handling and synapse. In each model compared to wild-type mice of the same genetic background, a number of genes showed increased expression changes of >10%, other genes showed decreases in each model. Most of the genes showed mixed effects. Several previous array findings were replicated. The results point to cellular stress and changes in post-synaptic remodelling as final common mechanisms of depression and resilience.

Effects of maternal separation on hypothalamic-pituitary-adrenal responses, cognition and vulnerability to stress in adult female rats.

We studied the long term effects of neonatal stress in female rats and subsequent responses to stress when adults. Female rats that experienced maternal separation (MS) showed in adulthood depressive-like behavior in the forced swimming test and cognitive impairments in the novel object recognition test, which were reverted by the glucocorticoid receptor antagonist mifepristone or the beta-adrenoceptor antagonist propranolol. Markers of HPA axis (corticosterone levels, CRF mRNA levels in the paraventricular nucleus and glucocorticoid receptor density in the hippocampus) were altered by MS, suggesting that an altered HPA axis function may be associated to behavioral and cognitive deficits in MS female rats. In addition, MS rats were found to be more vulnerable to chronic stress than controls as shown by decreases in open field activity, increases in immobility time in the forced swim test, and changes in markers of HPA axis (decreases in the density of glucocorticoid receptors). These present findings are discussed in terms of gender differences in adulthood.

Long-lasting behavioral effects and recognition memory deficit induced by chronic mild stress in mice: effect of antidepressant treatment.

RATIONALE: Many studies support the validity of the chronic mild stress (CMS) model of depression in rodents. However, most of them focus on analysis of reactivity to rewards during the CMS and/or depressive-like behavior shortly after stress. In this study, we investigate acute and long-term effects of CMS and antidepressant treatment on depressive, anxiety-like behavior and learning. MATERIALS AND METHODS: Mice (C57BL/6) were exposed to CMS for 6 weeks and anhedonia was evaluated by weekly monitoring of sucrose intake. Paroxetine (10 mg kg(-1)day(-1) i.p.) or saline were administered the last 3 weeks of CMS and continued for 2 weeks thereafter. Behavioral tests were performed over the last week of CMS (acute effects) and 1 month later (long-term effects). RESULTS: Mice exposed to CMS displayed both acute and long-term decreased sucrose intake, increased immobility in the forced swimming test (FST) and impaired memory in the novel object recognition test. It is interesting to note that a correlation was found between the cognitive deficits and the helpless behavior in the FST induced by CMS. During the CMS procedure, paroxetine treatment reverted partially recognition memory impairment but failed to prevent the increased immobility in the FST. Moreover, it decreased on its own sucrose intake. Importantly, the long-term effects of CMS were partially prevented by chronic paroxetine. CONCLUSIONS: CMS leads to a long-term altered behavioral profile that could be partially reverted by chronic antidepressant treatment. This study brings novel features regarding the long-term effects of CMS and on the predictive validity of this depression animal model.

Enhanced anxiety, depressive-like behaviour and impaired recognition memory in mice with reduced expression of the vesicular glutamate transporter 1 (VGLUT1).

Three isoforms of a vesicular glutamate transporter (VGLUT1-3) have been identified. Of these, VGLUT1 is the major isoform in the cerebral cortex and hippocampus where it is selectively located on synaptic vesicles of excitatory glutamatergic terminals. Variations in VGLUT1 expression levels have a major impact on the efficacy of glutamate synaptic transmission. Given evidence linking alterations in glutamate neurotransmission to various neuropsychiatric disorders, we investigated the possible influence of a down-regulation of VGLUT1 transporter on anxiety, depressive-like behaviour and learning. The behavioural phenotype of VGLUT1-heterozygous mice (C57BL/6) was compared to wild-type (WT) littermates. Moreover, VGLUT1-3 expression, hippocampal excitatory terminal ultrastructure and neurochemical phenotype were analysed. VGLUT1-heterozygous mice displayed normal spontaneous locomotor activity, increased anxiety in the light-dark exploration test and depressive-like behaviour in the forced swimming test: no differences were shown in the elevated plus-maze model of anxiety. In the novel object recognition test, VGLUT1(+/-) mice showed normal short-term but impaired long-term memory. Spatial memory in the Morris water maze was unaffected. Western blot analysis confirmed that VGLUT1 heterozygotes expressed half the amount of transporter compared to WT. In addition, a reduction in the reserve pool of synaptic vesicles of hippocampal excitatory terminals and a 35-45% reduction in GABA in the frontal cortex and the hippocampus were observed in the mutant mice. These observations suggest that a VGLUT1-mediated presynaptic alteration of the glutamatergic synapses, in specific brain regions, leads to a behavioural phenotype resembling certain aspects of psychiatric and cognitive disorders.

Glutamate receptor activation is involved in 5-HT2 agonist-induced Arc gene expression in the rat cortex.

Brain 5-HT regulates the expression of gene transcription factor as well as novel effector immediate early genes (IEGs). The 5-HT regulation of the gene transcription factor IEG, c-fos, involves activation of 5-HT2A and ionotropic glutamate receptors. Here, we investigate whether these receptors are also involved in the regulation of the effector IEG, Arc. In rats, the 5-HT2 agonist DOI induced a marked increase in expression of Arc mRNA in a variety of cortical regions. This effect was blocked by the selective 5-HT2A receptor antagonist, MDL 100,907, but not the 5-HT(2B/2C) receptor antagonist, SB206553. The AMPA receptor antagonist GYKI 52466 also attenuated DOI-induced Arc mRNA expression, as did the NMDA receptor antagonist MK801 in some regions. Immunofluorescence studies showed that DOI increased Arc-immunoreactivity in cortical cells that expressed AMPA and NMDA receptor subunits but not the 5-HT2A receptor. Finally, DOI-induced Arc-immunoreactivity in cortical cells was extensively co-localised with c-fos-immunoreactivity. These results suggest that, as with c-fos expression, ionotropic glutamate receptors (AMPA and NMDA) are involved in 5-HT2A receptor-induced Arc expression. This finding, together with evidence of extensive Arc and c-fos co-localisation, suggests that 5-HT2A receptor activation may induce the expression of both effector and transcription factor IEGs via common molecular and cellular substrates.

Antidepressant drug treatment induces Arc gene expression in the rat brain.

The mechanism underlying the therapeutic effect of antidepressants is not known but neuroadaptive processes akin to long-term potentiation have been postulated. Arc (Activity-regulated, cytoskeletal-associated protein) is an effector immediate early gene implicated in LTP and other forms of neuroplasticity. Recent data show that Arc expression is regulated by brain 5-hydroxytryptamine neurones, a target of many antidepressants. Here in situ hybridisation and immunohistochemistry were used to examine whether Arc expression in rat brain is altered by antidepressant drug treatment. Repeated administration of the monoamine reuptake inhibitors paroxetine, venlafaxine or desipramine induced region-specific increases in Arc mRNA. These increases were greatest in regions of the cortex (frontal and parietal cortex) and hippocampus (CA1 layer) and absent in the caudate putamen. Repeated treatment with the monoamine oxidase inhibitor, tranylcypromine, increased Arc mRNA in a similar fashion to the monoamine reuptake inhibitors. The antidepressant drugs also increased the number of Arc-immunoreactive cells in the parietal cortex. Acute antidepressant injection, and repeated administration of the antipsychotic drug chlorpromazine, produced either limited or no changes in Arc mRNA. The data suggest that chronic treatment with antidepressant drugs induces Arc gene expression in specific regions across the rat forebrain. Up-regulation of Arc expression may be part of the process by which antidepressant drugs achieve long-term changes in synaptic function in the brain.

Effect of different 5-HT1A receptor antagonists in combination with paroxetine on expression of the immediate-early gene Arc in rat brain.

Selective 5-HT(1A) receptor antagonists enhance the effect of selective serotonin reuptake inhibitors (SSRIs) on presynaptic 5-HT function, and have potential as antidepressant augmentation therapies. The present study tested the effect of different selective 5-HT(1A) receptor antagonists (WAY 100635, NAD-299, p-MPPI and LY 426965) in combination with a SSRI (paroxetine), on postsynaptic 5-HT function measured by increased expression of the immediate early gene, Arc. Paroxetine (5 mg/kg s.c.) combined with WAY 100635 (0.3 mg/kg s.c.) increased Arc mRNA in frontal, parietal and piriform cortices, and caudate putamen. Paroxetine (5 mg/kg s.c.) plus NAD-299 (1 or 5 mg/kg s.c.) had a similar effect. None of these drugs increased Arc mRNA when administered alone. Paroxetine (5 mg/kg s.c.) plus p-MPPI (8.5 mg/kg s.c.) also increased Arc mRNA but p-MPPI itself elevated Arc mRNA in many regions. Whilst LY 426965 (3 or 10 mg/kg s.c.) had no effect alone, when combined with paroxetine (5 mg/kg s.c.), the drug increased Arc mRNA in caudate putamen but not cortical regions.In conclusion, this study demonstrates that four 5-HT(1A) receptor antagonists augment the effect of an SSRI on Arc mRNA expression, which is suggestive of increased postsynaptic 5-HT function. However, the data reveal certain differences in the 5-HT(1A) receptor antagonists not recognised in models of presynaptic 5-HT function.

New 1-aryl-3-(4-arylpiperazin-1-yl)propane derivatives, with dual action at 5-HT1A serotonin receptors and serotonin transporter, as a new class of antidepressants.

In a search toward new and efficient antidepressants, 1-aryl-3-(4-arylpiperazin-1-yl)propane derivatives were designed, synthesized, and evaluated for 5-HT reuptake inhibition and 5-HT1A receptor antagonism. This dual pharmacological profile should lead, in principle, to a rapid and pronounced enhancement in serotoninergic neurotransmission and consequently to a more efficacious treatment of depression. The design was based on coupling structural moieties related to inhibition of serotonin reuptake, such as gamma-phenoxypropylamines, to arylpiperazines, typical 5-HT1A ligands. In binding studies, several compounds showed affinity at the 5-HT transporter and 5-HT1A receptors. Antidepressant-like activity was initially assayed in the forced swimming test with those compounds with Ki < 200 nM in both binding studies. Functional characterization was performed by measuring the intrinsic effect on rectal temperature in mice and also the antagonism to 8-OH-DPAT-induced hypothermia. The most efficacious compounds (12f, 23gE, 28a, and 28b) were further explored for their ability to antagonize 8-OH-DPAT-induced inhibition of forskolin-stimulated cAMP formation in a cell line expressing the 5-HT1A receptor. Furthermore, the antidepressant-like properties of 12f, 28a, and 28b, which exhibited 5-HT1A receptor antagonistic property in the latter study, were also evaluated in the learned helplessness test in rats. Among these three compounds, 28b (1-benzo[b]thiophene-3-yl)-3-[4-(2-methoxyphenyl)-1-ylpropan-1-ol) showed the higher affinity at both the 5-HT transporter and 5-HT1A receptors (Ki = 20 nM in both cases) and was also active in the other pharmacological tests. Such a pharmacological profile could lead to a new class of antidepressants with a dual mechanism of action and a faster onset of action.

New 3-[4-(aryl)piperazin-1-yl]-1-(benzo[b]thiophen-3-yl)propane derivatives with dual action at 5-HT1A serotonin receptors and serotonin transporter as a new class of antidepressants.

A series of new 3-[4-(aryl)piperazin-1-yl]-1-(benzo[b]thiophen-3-yl)propane derivatives were synthesized in an attempt to find a new class of antidepressant drugs with dual activity at 5-HT1A serotonin receptors and serotonin transporter. Title compounds were evaluated for in vitro activity on 5-HT1A receptor and 5-HT transporter. They show high nanomolar affinity for both activities, and in particular, compounds 1-(5-chlorobenzo[b]thiophen-3-yl)-3-[4-(2-methoxyphenyl)piperazin-1-yl]propan-1-ol (7) and 1-(5-fluorobenzo[b]thiophen-3-yl)-3-[4-(2-methoxyphenyl)piperazin-1-yl]propan-1-ol (8) show values (nM) of K(i)=30 and 2.3 for 5-HT1A receptors and K(i)=30 and 12 for serotonin transporters, respectively. In GTPgammaS binding assays, compound 8 revealed antagonist properties to 5-HT1A receptors. Such a pharmacological profile could lead to potent antidepressant agents with new dual mechanism of action.

Design, synthesis and biological evaluation of new 3-[(4-aryl)piperazin-1-yl]-1-arylpropane derivatives as potential antidepressants with a dual mode of action: serotonin reuptake inhibition and 5-HT1A receptor antagonism.

It has been suggested that the combination of a selective serotonin reuptake inhibitor (SSRI) and a 5-HT1A receptor antagonist may facilitate the onset of the SSRIs antidepressant action. Accordingly, we describe the synthesis of a series of new 3-[(4-aryl)piperazin-1-yl]-1-arylpropane derivatives with structural modifications performed in Ar1, Ar2 and Z (Z is different functional groups) to obtain the sought dual activity. Compounds were evaluated for in vitro affinity at 5-HT1A receptors and 5-HT transporter. The antidepressant-like activity of derivatives with the higher affinity was assessed initially using the forced swimming test (FST). Compound 1-(2,4-dimethylphenyl)-3-[(2-methoxyphenyl)piperazin-1-il]-1-propa none (III.1.a) showed the best antidepressant-like activity which was further confirmed in the learned helplessness test.