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Traumatic brain injury (TBI) is one of the leading cause of psychiatric conditions in patients, amongst which, depression and anxiety are more frequent. Despite the preclinical antidepressant-like effects, clinical development of Phospodiesterase-4 (PDE4) enzyme inhibitors has been hampered due to serious side effect profiles, such as nausea and vomiting. Etazolate (ETZ) is a new generation PDE4 inhibitor with encouraging safety and tolerance profiles. In our previous studies we have addressed that ETZ produces antidepressant-like effects in animal models of depression, however, the underlying mechanism(s) following TBI have not been completely explored. Impact accelerated TBI by weight drop method causes depression-like behavioral deficits in modified open field exploration, hyper-emotionality and sucrose consumption paradigms. TBI not only causes immediate mechanical damage to the brain, but also induces biochemical changes that lead to delayed neural cell loss leading to a secondary injury. The present study examines the antidepressant effects of ETZ on the TBI-induced depression-like behavior deficits and attempts to explore the underlying mechanism. In order to understand the underlying pathology of TBI and mechanism(s) of ETZ in TBI molecular markers namely, brain cAMP, cAMP response element binding protein (pCREB) and brain-derived neurotrophic factor (BDNF) were estimated. Additionally, the level of oxidative (lipid peroxidation) & nitrosative (nitrite) stress markers, along with antioxidant enzymes markers, such as, reduced glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT) were measured. Furthermore, the involvement of hypothalamic-pituitary adrenal (HPA) axis activity in underlying mechanism was also investigated by measuring serum corticosterone (CORT) level. The results revealed that TBI significantly altered cAMP, pCREB and BDNF levels. Moreover, a significant increase in oxidative–nitrosative stress markers levels, while, significant decreases in antioxidant enzymes markers level were observed. However, no significant change was observed in serum CORT level. Chronic ETZ (0.5 and 1 mg/kg) treatment significantly attenuated TBI-induced behavioral deficits and restored the TBI induced derangements in molecular and biochemical markers. This study indicates that ETZ modulates cAMP signaling and oxidative/antioxidant markers in the TBI model suggesting its prospect as a potential candidate for the pharmacotherapy of depression.

Depression associated with obesity remains an interesting area to study the biological mechanisms and novel therapeutic intervention. The present study investigates the effect of a novel 5-HT3 receptor antagonist 3-methoxy-N-p-tolylquinoxalin-2-carboxamide (QCM-4) on several pathogenic markers of depression associated with obesity such as plasma insulin resistance, hippocampal cyclic adenosine monophosphate (cAMP), brain-derived neurotrophic factor (BDNF), serotonin (5-HT) concentrations, hippocampal neuronal damage, and p53 protein expression in high-fat-diet (HFD)-fed mice. Obesity was experimentally induced in mice by feeding with HFD for 14 weeks followed by administration of QCM-4 (1 and 2 mg/kg, p.o.)/standard escitalopram (ESC) (10 mg/kg, p.o.)/vehicle (10 ml/kg, p.o.) for 28 days. Behavioral assays such as sucrose preference test (SPT); forced swim test (FST); elevated plus maze (EPM); biochemical assays including oral glucose tolerance tests (OGTT), insulin, cAMP, BDNF, and 5-HT concentrations; and molecular assays mainly histology and immunohistochemistry (IHC) of p53 protein in the dentate gyrus (DG), CA1, and CA3 regions of hippocampus in HFD fed mice were performed. Chronic treatment with QCM-4 in HFD-fed mice reversed the behavioral alterations in SPT, FST, and EPM. QCM-4 showed poor sensitivity for plasma glucose, improved insulin sensitivity, increased hippocampal cAMP, BDNF, and 5-HT concentrations. In the hippocampal DG, CA1, and CA3 regions, QCM-4 treatment improved the neuronal morphology in the histopathology and inhibited p53 protein expression in IHC assay in HFD-fed mice. QCM-4 attenuated the depressive-like phenotype in HFD-fed mice by improving behavioral, biochemical, and molecular alterations through serotonergic neuromodulation.

Pioglitazone, a peroxisome proliferator activated receptor gamma (PPARγ) agonist belonging to thiazolidinedione class, is mainly used in diabetes mellitus. Obese subjects are twice likely to become depressed than non-obese individuals. The biological mechanisms linking depression with obesity still remain poorly understood and there is immense need for better therapeutic intervention against such co-morbid disorders. The present study investigates the effect of pioglitazone on the chronic unpredictable mild stress (CUMS) induced depression in obese mice by using behavioral tests and biochemical estimations. Mice were fed with high fat diet (HFD) for 14 weeks and were further subjected to different stress procedures for 28 days to induce depressive behavior. Animals were administered orally with pioglitazone (30 mg/kg p.o.)/escitalopram (10 mg/kg p.o.)/vehicle (10 ml/kg p.o.) daily from day 15–28. Various behavioral paradigms such as sucrose preference test, forced swim test (FST), tail suspension test (TST) and elevated plus maze (EPM) were performed. Biochemical estimations including plasma glucose, total cholesterol, triglycerides, and total proteins were performed. The data obtained from behavioral assays and biochemical assessments indicated that obese animals exhibited severe depressive-like behavior compared to non-obese animals. Furthermore, obese animals subjected to CUMS worsen the depressive behavior compared to obese control animals. Repetitive treatment with pioglitazone reversed the CUMS induced behavioral and biochemical alterations in HFD fed obese mice which atleast in part may be mediated through improving altered plasma glucose. The study suggests that pioglitazone needs further attention with respect to molecular mechanisms that could provide a better therapeutic strategy against depression associated with obesity., Graphical abstract, Highlights • Obese animals subjected to chronic stress worsens depressive symptoms. • Altered plasma glucose involved in depression co-morbid with obesity. • Pioglitazone inhibited behavioral alterations in obese mice subjected to stress. • Pioglitazone attenuated the biochemical changes in obese mice subjected to stress. • Antidepressant-like effect of pioglitazone in depression associated with obesity.

Despite of the enormous research, therapeutic treatment for depression has always been a serious issue. Even though depression and obesity are individual abnormal health conditions, each act as a triggering factor for the other. Obese individuals are twice prone to develop depression than that of non-obese persons. The exact mechanism how obesity increases the risk for depression still remains an area of interest for research in neuropsychopharmacology. Depression and obesity share some common pathological pathways such as hyperactivity of hypothalamic-pituitary-adrenal (HPA) axis, dysregulation of oxidant/antioxidant system balance, higher level of inflammatory cytokines, leptin resistance, altered plasma glucose, insulin resistance, reduced neuronal brain derived neurotrophic factor (BDNF) and decreased serotonergic neurotransmission in various regions of brain. The antidepressant-like effect of 5-HT3 receptor antagonists through allosteric modulation of serotonergic pathways is well evident from several research investigations belonging to our and some in other laboratories. Furthermore, serotonin regulates diet intake, leptin, corticosterone, inflammatory mechanisms, altered plasma glucose, insulin resistance and BDNF concentration in brain. The present review deals with various biological mechanisms involved in depression co-morbid with obesity and 5-HT3 receptor antagonists by modulation of serotonergic system as a therapeutic target for such co-morbid disorder.

Depression is a chronic and debilitating mental disorder that often remains undertreated. It could be due to unclear understanding of pathophysiology and/or inconsistent efficacy of current pharmacotherapy. Since the discovery of the first effective medications in the late 1950s, a variety of agents have been developed, which are mainly based on correction of monoamine deficit. However, over time, many different strategies have been determined in an effort to improve the efficacy and reduce the untoward effects of the therapeutic intervention. This chapter compiles the relative efficacy and plausible mechanism of antidepressant activity of most current therapeutic approaches targeting a wide range of molecular and cellular pathways, implicated in the pathogenesis of depression. Emerging knowledge of key pathogenic mechanisms, such as the impairment of non-monoaminergic neurotransmission, in addition to monoaminergic neurotransmission, hypothalamic-pituitary-adrenal axis hyperactivity, alteration in neurogenesis signaling pathways, enhanced brain oxidative stress, and inflammatory activity, has led to a host of new molecular drug targets. Several of these have been validated through the preliminary use of lead compounds and therapeutic agents in animals and humans.

In our earlier study we reported the antidepressant activity of ondansetron in obese mice. The present study investigates the effect of ondansetron on depression and anxiety associated with obesity in experimental mice with biochemical evidences. Male Swiss albino mice were fed with high fat diet (HFD) for 14 weeks to induce obesity. Then the subsequent treatment with ondansetron (0.5 and 1 mg/kg, p.o.), classical antidepressant escitalopram (ESC) (10 mg/kg, p.o.) and vehicle (distilled water 10 ml/kg, p.o.) was given once daily for 28 days. Behavioral assay for depression including sucrose preference test, forced swim test (FST) and anxiety such as light dark test (LDT) and hole board test (HBT) were performed in obese mice. Furthermore, in biochemical estimations oral glucose tolerance test (OGTT), plasma leptin, insulin, corticosterone, brain oxidative stress marker malonaldehyde (MDA), antioxidant reduced glutathione (GSH) and serotonin assays were performed. Results indicated that HFD fed obese mice showed severe depressive and anxiety-like behaviors. Chronic treatment with ondansetron inhibited the co-morbid depression and anxiety in obese mice by increasing sucrose consumption in sucrose preference test and reducing the immobility time in FST, increasing time and transitions of light chamber in LDT, improving head dip and crossing scores in HBT compared to HFD control mice. Ondansetron in obese mice inhibited glucose sensitivity in OGTT, improved plasma leptin and insulin sensitivity, reversed hypothalamic pituitary adrenal (HPA) axis hyperactivity by reducing the corticosterone concentration, restored brain pro-oxidant/anti-oxidant balance by inhibiting MDA and elevating GSH concentrations and facilitated serotonergic neurotransmission. In conclusion, ondansetron reversed the co-morbid depression and anxiety associated with obesity in experimental mice by attenuating the behavioral and biochemical abnormalities.

Background: Malaria, an infectious disease transmitted by mosquitoes, has affected the world since the beginning of recorded human history and it remains an ensconced global health challenge even today. Among the various proteases, expressed in the life cycle of parasite, cysteine protease falcipain-2 plays a pivotal role in parasite food assimilation and inhibition of this protease cause deleterious effects on the growth of parasite. Methods: Employing a ligand-based approach, 1-(4-(substituted)piperazin-1-yl)-2-(phenylamino)ethanone derivatives were designed and synthesized from the starting material piperazine in a sequence of reactions. Structural assignments are based on spectral data ( 1 H NMR, mass) and elemental analyses. The purity of the final compounds was confirmed by HPLC. The compounds were tested for their in vitro falcipain-2 inhibitor activity on recombinant falcipain-2 enzyme. Furthermore, molecular docking studies were performed using Glide 5.9 software to incur a precise picture of the active ligand at the atomic level which will be helpful in the discovery of new antimalarial drugs. Results: Among the screening results of seventeen novel entities, three compounds (6h, 6n and 6o) have showed good inhibitory activity and eleven compounds were showed weak to moderate inhibitor activity. Docking studies for these active analogues revealed that the amino acids Trp 206, Ile 85, Leu 84, Val 152 most commonly involved in hydrophobic interactions and Asn 173, Cys 42, Gln 36, amino acids involved in hydrogen bonding. Conclusion: The preliminary structure-activity relationships indicated that compound 6h, is the most potent compound from this series, and it can be used as a potential lead compound in the designing of new candidates to optimize the inhibitory potencies of this class of compounds, and potentially with potent antimalarial activity. Key words: Antimalarial, Falcipain-2, Ligand-based drug design, Plasmodium falciparum .

Series of piperazine analogs of naphthyridine-3-carboxamides and indole-2-carboxamides were designed using a ligand-based approach with consideration of the pharmacophoric requirements for 5-HT3 receptor antagonists. The title carboxamides were synthesized using appropriate synthetic routes. Initially, the 5-HT3 receptor antagonistic activity of all the compounds was determined on isolated guinea pig ileum tissue against the 5-HT3 agonist, 2-methyl-5-hydroxytryptamine, which was denoted in the form of pA2 values. The structure-activity relationship regarding the influence of the aromatic part and basic moiety as features in the 5-HT3 pharmacophore was derived. Among all the compounds screened, the piperazine derivatives of indole-2-carboxamide 13i and naphthyridine-3-carboxamide 8h exhibited prominent 5-HT3 receptor antagonism with pA2 values of 7.5 and 7.3, respectively. Subsequent investigation of the antidepressant activities of selected compounds in the mouse forced swim test (FST) led to the identification of the piperazine analogs of indole-2-carboxamide 13i and naphthyridine-3-carboxamide 8h as the most promising compounds. Both 13i and 8h demonstrated significant reduction in the duration of immobility as compared to the control. Importantly, none of the tested compounds affected the baseline locomotion of mice at the tested dose levels.

Several preclinical studies have revealed antidepressant and anxiolytic-like effect of 5-HT3 receptor antagonists. In our earlier study, we have reported the antidepressive-like effect of 3-methoxy-N-p-tolylquinoxalin-2-carboxamide (QCM-4) in obese mice subjected to chronic stress. The present study deals with the biochemical mechanisms associated with depression co-morbid with obesity. Mice were fed with high fat diet (HFD) for 14 weeks, further subjected for treatment with QCM-4 (1 and 2 mg/kg p.o.) and standard antidepressant escitalopram (ESC) (10 mg/kg p.o.) for 28 days. Behavioral assays for depression such as sucrose preference test (SPT), forced swim test (FST) and for anxiety such as light and dark test (LDT) and hole board test (HBT) were performed in obese mice. Biochemical assessments including plasma leptin and corticosterone concentration followed by brain oxidative stress parameters malonaldehyde (MDA) and reduced glutathione (GSH) were performed. Results confirmed that QCM-4 exhibits antidepressive effect by increasing the sucrose consumption in SPT, reducing immobility time in FST and anxiolytic effect by increasing transitions and time in light chamber in LDT, increasing head dip and crossing score in HBT. Furthermore, QCM-4 attenuated the hypothalamic–pituitary–adrenal (HPA) axis hyperactivity by reducing the plasma corticosterone, reversing altered plasma leptin, restoring the imbalance of brain MDA and GSH concentration. In conclusion, QCM-4 showed antidepressive and anxiolytic effect by reversing the behavioral alterations that were supported by biochemical estimations in obese mice.

Background Chronic unpredictable stressors can produce a situation similar to human depression and such animal models can be used for the preclinical evaluation of antidepressants. The 5-HT 3 receptor antagonists modulate serotonergic pathways and show antidepressant-like effect in various animal models of depression. Methods In this study, a novel and potential 5-HT 3 receptor antagonist N -n-propyl-3-ethoxyquinoxaline-2-carboxamide ( 6n ) with good Log P (2.52) value and p A 2 (7.6) values, synthesized in our laboratory was explore to study the effects on CUMS-induced behavioural and biochemical alterations in mice. Mice were subjected to different stress paradigms daily for a period of 28 days to induce depressive-like behaviour. Results CUMS caused depression-like behaviour in mice, as indicated by the significant decrease in sucrose consumption and increase in immobility time in the forced swim test (FST) while there was no significant effect on spontaneous locomotor activity (SLA) observed. In addition it was found that lipid peroxide and nitrite levels were significantly increased, whereas glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT) levels were decreased in brain tissue of CUMS-treated mice. Compound 6n (1 and 2 mg/kg, po , 21 days) and fluoxetine treatment (20 mg/kg, po , 21 days) significantly altered the CUMS-induced behavioural (increased immobility period, reduced sucrose preference) and biochemical (increased lipid peroxidation, increased brain nitrite; decreased GSH, SOD and CAT levels) parameters while there was no significant effect of observed on SLA. Conclusion Compound 6n produced antidepressant-like effects in behavioural despair paradigm in chronically stressed mice by restoring antioxidant enzyme activity up to significant level.

The prokaryotic ATP-dependent ClpP protease, localized in the relict plastid of malaria parasite, represents a potential drug target. In the present study, we utilized in silico structure-based screening and medicinal chemistry approaches to identify a novel pyrimidine series of compounds inhibiting P. falciparum ClpP protease activity and evaluated their antiparasitic activities. Structure-activity relationship indicated that morpholine moiety at C2, an aromatic substitution at N3 and a 4-oxo moiety on the pyrimidine are important for potent inhibition of ClpP enzyme along with antiparasiticidal activity. Compound 33 exhibited potent antiparasitic activity (EC₅₀ 9.0±0.2μM), a 9-fold improvement over the antiparasitic activity of the hit molecule 6. Treatment of blood stage P. falciparum cultures with compound 33 caused morphological and developmental abnormalities in the parasites; further, compound 33 treatment hindered apicoplast development indicating the targeting of apicoplast.

Stimulation of high oxidative stress in the brain is considered as an important factor for neurotoxicity towards the pathophysiology of chronic stress-induced depression disorder. In the present research, a potential 5-HT 3 receptor antagonist N -n-butyl-3-methoxy quinoxaline-2-carboxamide ( 6o ) having good Log P (2.60) and p A 2 (7.7) values was examined for its effect on the behavioral and biochemical changes induced by the chronic unpredictable mild stress (CUMS) model. In the current investigation mice were introduced to different stress procedures daily for a period of 28 days to induce a depressive-like behavior. The results show that CUMS caused a depression-like behavior in mice, as indicated by the significant decrease in sucrose consumption and locomotor activity and increase in immobility in the forced swim test (FST). Moreover, it was found that oxidative stress markers such as lipid peroxide and nitrite levels were significantly increased, whereas, antioxidant enzymes such as glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT) levels were decreased in the brain tissue of CUMS-subjected mice. “Compound 6o ” (1 and 2 mg/kg, p.o.) and fluoxetine treatment (20 mg/kg, p.o.) for a period of 21 days altered the CUMS-induced behavioral (increased immobility period, reduced sucrose preference and decreased locomotor activity) and biochemical (increased lipid peroxide, increased brain nitrite; decreased GSH, SOD and CAT levels) alterations. Moreover normal mice treated with “compound 6o ” (2 mg/kg, p.o.) showed a significant decrease in the duration of immobility in FST as compared to normal vehicle treated mice. In conclusion, “compound 6o ” produced antidepressant-like effects in behavioral despair paradigm in chronically stressed mice by restoring antioxidant enzyme activity.

The biological mechanisms that link the development of depression to metabolic disorders such as obesity and diabetes remain ambiguous. In the present study the potential of a selective cyclooxygenase inhibitor celecoxib (15 mg/kg p.o.) was investigated in depression associated with obesity in mice. Behavioral tests used to assess depressive-like behavior were sucrose preference test, forced swim test (FST), tail suspension test (TST) and elevated plus maze (EPM). The basal locomotor score in obese mice was not altered. Furthermore, estimation of biochemical parameters was performed for plasma glucose, total cholesterol, triglycerides and total proteins. Escitalopram (10 mg/kg p.o.) served as reference standard drug. In the results, chronic treatment with celecoxib for 28 days significantly attenuated the behavioral alterations as indicated by increased the sucrose consumption, reduced the immobility time in FST and TST, increased the percent open arm time and entries in EPM in obese mice. In the biochemical parameters celecoxib significantly reversed the increased plasma glucose, total cholesterol, triglycerides and total proteins in obese mice. In conclusion, celecoxib exhibited potential antidepressant-like effect in depression associated with obesity, which to some extent is mediated by reversing the altered plasma glucose in obese mice.

Objective: To investigate the antidepressant-like effect of N -(benzo[ d ] thiazol-2-yl)-3- ethoxyquinoxalin-2-carboxamide 6k, a 5-hydroxytryptamine type 3 (5-HT 3 ) receptor antagonist using rodents behavioral battery tests. Materials and Methods: 6k screening was performed with behavioral assays for depression-like forced swim test (FST) at several single doses (0.25-4 mg/kg, intraperitoneal injection (i.p.)) to test the potency of 6k, in which 2 and 4 mg/kg doses were found to be most effective and hence, in further behavioral assays including mechanistic model like 5-hydroxytryptophan (5-HTP)-induced head twitches was performed in mice at acute doses of 6k (2 and 4 mg/kg, i.p.). Furthermore, olfactory bulbectomy (OBX), a surgical model-induced behavioral alterations was performed in rats, and the effect of 6k administered orally (2 and 4 mg/kg, p.o.) after subchronic treatment for 14 days starting from day 15 of postsurgery was examined by percent sucrose preference test and modified open field test (OFT). Results: 6k (1, 2, and 4 mg/kg, i.p.) reduced the immobility time and increased the swimming behavior in FST without affecting the baseline locomotor score showing antidepressant-like effect. 5-HTP-induced head twitch response was potentiated by 6k (2 and 4 mg/kg, i.p.), which indicated rise in the serotonergic neurotransmission in the brain. 6k (2 and 4 mg/kg, p.o.) showed anti-anhedonia effect by increasing the sucrose consumption and reversed the behavioral alterations when exposed to modified open field in OBX rats after subchronic treatment for 14 days, thus exhibiting antidepressant-like effect. Conclusion: 6k attenuated the behavioral derangement in rodents-based behavioral battery tests for depression, indicating antidepressant-like potential.

Preliminary study in our laboratory showed that etazolate produced antidepressant- and anxiolytic-like effects in rodent models, however, the ability of etazolate to produce antidepressant- and anxiolytic-like effects and underlying mechanism(s) in chronic unpredictable mild stress (CUMS) model have not been adequately addressed. This study was aimed to investigate the beneficial effects of etazolate on CUMS-induced behavioral deficits (depression- and anxiety-like behaviors). In addition, the possible underlying mechanism(s) of etazolate in CUMS model was also investigated by measuring serum corticosterone (CORT) and brain-derived neurotrophic factor (BDNF) levels. Mice were subjected to a battery of stressors for 28 days. Etazolate (0.5 and 1 mg/kg, p.o.) and fluoxetine (20mg/kg, p.o.) were administered during the last 21 days (8-28th) of the CUMS paradigm. The results showed that 4-weeks CUMS produces significant depression-like behavior in tail suspension test (TST) and partial anxiety-like behavior in elevated plus maze (EPM) and open field test (OFT). Stressed mice have also shown a significant high serum CORT and low BDNF level. Chronic treatment with etazolate (0.5 and 1mg/kg., p.o.) and fluoxetine (20mg/kg., p.o.) produced significant antidepressant-like behavior in TST (decreased duration of immobility), whereas, partial anxiolytic-like behavior in EPM (increased percentage of open arm entries) and OFT (increased % central ambulation score, total ambulation score and time spent in center zone). In addition, etazolate and fluoxetine treatment significantly (p

The aim of this study was to investigate the anxiolytic potential of a series of novel carboxylic acid based 1,8 naphthyridines as 5-HT3 receptor antagonists. The pA2 values of all the compounds were determined against agonist 2-methyl-5-hydroxytryptamine in longitudinal muscle myenteric plexus preparations from guinea pig ileum. Compounds with higher pA2 values, particularly those greater than ondansetron, a standard 5-HT3 receptor antagonist, and optimal log P values were screened in mice by using behavioral tests such as a light–dark (L/D) aversion test, elevated plus maze (EPM) test, and an open field test (OFT). In the L/D test, compounds 7a, 7b, 7d, 7e, and 7i (2 mg/kg body mass, intraperitoneal) significantly (P < 0.05) increased the latency time to leave the light compartment, total time spent in the light compartment, and the number of transitions between the light and dark compartments. Compounds 7a, 7d, 7f, 7h, and 7i (2 mg/kg, i.p.) significantly (P < 0.05) increased the time spent in the open arms and the number of entries into the open arms in the EPM test. In addition, compounds 7a, 7d, 7e, 7f, and 7h (2 mg/kg, i.p.) significantly (P < 0.05) increased the ambulation scores and the frequency of rearing in the OFT.

The present study was designed to investigate the putative antidepressant-like activity of 7a, a 5-HT3 receptor antagonist, (although indirect evidence of 5-HT3 antagonism) with an optimal log P (3.35) and pA2 value (7.6) greater than ondansetron (pA2 — 6.6) using behavioural tests battery of depression. Acute treatment of 7a (0.5-2 mg/kg, i.p.) in mice produced antidepressant-like effects in forced swim test (FST) and tail suspension test (TST) without affecting the baseline locomotion in actophotometer test in mice. Moreover, the combination of a sub-effective dose of 7a (0.25 mg/kg, i.p.) and fluoxetine (5 mg/kg, i.p.) produced an anti-immobility effect in mouse FST. Pretreatment of mice with p-chlorophenylalanine methyl ester (PCPA; 100 mg/kg, i.p., an inhibitor of serotonin (5-HT) synthesis, for 4 consecutive days) and 1-(m-Chlorophenyl)-biguanide (mCPBG, 10 mg/kg, i.p., a 5-HT3 receptor agonist) prevented the anti-immobility effects of 7a (2 mg/kg, i.p.) in the mouse FST. In addition, 7a (0.5–2 mg/kg, i.p.) treatment also potentiated the 5-hydroxytryptophan (5-HTP) and pargyline induced head twitch response in mice. Furthermore, sub-chronic treatment (14 days) with 7a (0.5–2 mg/kg, i.p.) and paroxetine (10 mg/kg, i.p.) significantly attenuated the behavioural anomalies induced by bilateral olfactory bulbectomy in rats in a modified open field paradigm. These results suggest that the antidepressant-like action of 7a may be mediated by an interaction with the serotonergic system and this molecule should be further investigated as an alternative therapeutic approach for the treatment of depression.

Linezolid, an oxazolidinone class antibiotic is a reversible and nonselective inhibitor of monoamine oxidase (MAO) enzyme, mainly for MAO-A subtype. Its antidepressant-like effect has been previously demonstrated in the rodent models of depression. MAO-A enzyme has been shown to play a role in the pathophysiology of anxiety disorders and inhibition of MAO-A in the brain could be used to treat anxiety disorders. Thus, the objective of this study was to investigate the putative anxiolytic effects of linezolid in rodent models of anxiety. Mice were acutely injected with linezolid (5-40 mg/kg, i.p.), diazepam (2 mg/kg, i.p.) and moclobemide (10 mg/kg., i.p.). Linezolid (20 and 40 mg/kg), diazepam and moclobemide significantly (p

BACKGROUND 5-HT3 receptor antagonists play a key role in the management of psychiatric disorders such as, depression and anxiety. They may act through modulation of serotonergic transmission. In the present study, a novel and potential 5-HT3 receptor antagonist, 6g (4-benzylpiperazin-1-yl)(3-methoxyquinoxalin-2-yl) methanone, which exhibited good log P (3.08) and pA2 (7.5) values was screened for its anxiolytic property in lipopolysaccharide (LPS) induced anxiety models. METHODS LPS, an endotoxin, present in the cell wall of Gram negative bacteria was injected 0.83 mg/kg, i.p. as a single dose to induce anxiety-like symptoms in mice. Compound 6g (1 and 2 mg/kg, p.o.) and standard fluoxetine (FLX) (20 mg/kg, p.o.) were injected to treatment groups for 7 days and evaluated in various behavioral paradigms such as elevated plus maze (EPM), light and dark (L/D) test, and open field test (OFT). Their effects on serotonin levels in mice brain were also examined. RESULTS The results showed that LPS induced anxiety-like symptoms in mice, as indicated by a significantly decreased percentage open arm entries and percentage time spent in open arms in EPM; decreased time spent in light area and number of transition between chambers in L/D test; decreased ambulation and rearing scores in OFT. Compound 6g (1 and 2 mg/kg, p.o., 7 days) and FLX treatment (20 mg/kg, p.o., 7 days) reversed the LPS-induced behavioral changes and significantly affected all the behavioral parameters mentioned above. In addition 6g (1 and 2 mg/kg, p.o., 7 days) and FLX treatment (20 mg/kg, p.o., 7 days) increased the levels of serotonin in mice brain. CONCLUSIONS Compound 6g produced anxiolytic-like effects in various anxiety paradigms in LPS-treated mice as well as restored the decreased serotonin levels in mice brain.

Background Several preclinical studies have shown that serotonergic 5-HT3 receptor antagonists play an important role in the management of neuropsychiatric disorders, such as depression and anxiety. In the present study the compound "6n" (N-n-propyl-3-ethoxyquinoxaline-2-carboxamide), a novel 5-HT3 receptor antagonist with an optimal log P (2.52) and pA2 (7.6) value was screened for its neuro-pharmacological potential in chronic rodent models of depression and anxiety named traumatic brain injury (TBI). Methods In this model, a 1 cm midline scalp incision was made, and the muscles were retracted to expose the skull. A stainless steel disc (10 mm in diameter and 3 mm in depth) was placed centrally between the lambda and bregma regions. The injury was induced using the impact acceleration model of TBI. Specifically, a 400 g metal weight was dropped from a height of 1 m guided by a straight pipe, onto the metal disc placed over the rat's skull. Results The behavioral anomalies of the TBI rats were attenuated by the chronic treatment of compound 6n (1 and 2 mg/kg, p.o.; 14 days) as observed by the modified open field test (ambulation, rearing, and fecal pellet), sucrose consumption test (% sucrose consumption), elevated plus maze [% open arm entries [OAE] and % time spent in open arm (TSOA)], and marble burying test (numbers). In addition, 6n also increased the levels of neurotransmitters (norepinephrine and serotonin) and brain derived neurotrophic factor (BDNF) in TBI rats. Conclusions The result suggests that compound 6n exhibited antidepressant- and anxiolytic-like effects in rodent models of depression and anxiety.

Employing a ligand-based approach, 3-methoxyquinoxalin-2-carboxamides were designed as serotonin type-3 (5-HT(3) ) receptor antagonists and synthesized from the starting material o-phenylenediamine in a sequence of reactions. The structures of the synthesized compounds were confirmed by spectral data. These carboxamides were investigated for their 5-HT(3) receptor antagonisms in longitudinal muscle myenteric plexus preparations from guinea-pig ileum against a standard 5-HT(3) agonist, 2-methy-5-HT, and their antagonism activities are expressed as pA(2) values. Compounds 6a (pA(2) : 7.2), 6e (pA(2) : 7.0), 6f (pA(2) : 7.5), 6g (pA(2) : 7.5), 6n (pA(2) : 7.0), and 6o (pA(2) : 7.2) exhibited antagonism greater than that of the standard 5-HT(3) antagonist, ondansetron (pA(2) : 6.9).

Aim: The present study was designed to investigate the antidepressant potential of (4-phenylpiperazin-1-yl) (quinoxalin-3-yl) methanone (4a), a novel 5-HT 3 receptor antagonist, with an optimal log P (2.84) and pA 2 value (7.3) greater than ondansetron (6.9) using rodent behavioural models of depression. Materials and Methods: Swiss albino mice were used in actophotometer test, forced swim test (FST) and 5-hydroxytryptophan (5-HTP) induced head twitch response. Reserpine induced hypothermia (RIH) and olfactory bulbectomy were performed in male Wistar rats. Statistical analysis was carried out by using one-way analysis of variance followed by Tukey's test. Results: Acute treatment of 4a (1-4 mg/kg, i.p.) in mice produced antidepressant-like effects in FST without affecting the baseline locomotion in actophotometer test. Further, 4a (2-4 mg/kg, i.p.) potentiated the 5-HTP induced head twitches response in mice and also antagonized RIH in rats. Furthermore, sub-chronic (14 days) treatment with 4a (2-4 mg/ kg, p.o.) significantly attenuated the behavioural anomalies induced by bilateral olfactory bulbectomy in rats in modified open field exploration. Conclusions: These preliminary investigations confirm that 4a exhibits antidepressant-like activity in behaviour based rodent models of depression.

A novel series of quinoxalin-2-carboxamides were designed based on the ligand-based approach, employing a three-point pharmacophore model; it consists of an aromatic residue and a linking carbonyl group and a basic nitrogen. The target new chemical entities were synthesized from the key intermediate, quinoxalin-2-carboxylic acid, by coupling it with various amines in the presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) and 1-hydroxybenzotriazole (HOBt). The obtained compounds' structures were confirmed by spectral data. The target new chemical entities were evaluated for their 5-HT(3) receptor antagonisms in longitudinal muscle myenteric plexus preparation from guinea pig ileum against 5-HT(3) agonist, 2-methyl-5-HT, which was expressed in the form of pA(2) value. All the synthesized compounds showed antagonism towards 5-HT(3) receptor; based on this result, a structure-activity relationship was derived, which reveals that the aromatic residue in 5-HT(3) receptor antagonists may have hydrophobic interaction with 5-HT(3) receptor. Regardless of their antagonistic potentials, all the synthesized molecules were screened for their anti-depressant potentials by using forced swim test in mice model; interestingly none of the tested compounds affect the locomotion of mice in the tested dose levels. Compounds with significant pA(2) values exhibited good anti-depressant-like activity as compared to the vehicle-treated group.

The serotonin type 3 (5-HT(3)) receptor is unique among the seven recognized serotonin receptor "families". The existence serotonin type 3 receptor (5-HT(3)) in neuro-anatomical regions stimulated the research interest for novel therapeutic targets such as anxiety, depression, nociception and cognitive function. In the current study, (4-benzylpiperazin-1-yl) (quinoxalin-2-yl) methanone (QCF-3), a novel 5-HT(3) receptor antagonist, with an optimal log P (the logarithm of the ratio of the concentrations of the un-ionized solute in the solvents is called log P) and significant pA2 value (is a negative logarithm of the molar concentration of antagonist required to reduce the effect of multiple dose agonist to that of single dose) was screened for its anti-depressant potential using rodent behavioral models of depression. Psycho-pharmacological investigations involved acute and chronic treatment (14 days) with QCF-3 and assessment of behavior during the forced swim test (FST) and tail suspension test (TST) in mice and olfactory bulbectomised rats. A dose response study in mice revealed an initial anti-depressant-like effect of QCF-3 (0.5-4 mg/kg, ip) in the FST and TST. Interaction studies showed that QCF-3 (1 and 2 mg/kg) significantly enhanced the antidepressant action of fluoxetine and bupropion in the FST and TST, respectively. QCF-3 (1 and 2 mg/kg) potentiated the 5-hydroxytryptophan (5-HTP) induced head twitches response in mice and reversed reserpine-induced hypothermia in rats. Further, OBX rats exhibited behavioral anomalies in the open field and hyper-emotionality tests that were attenuated by chronic QCF-3 treatment. In conclusion, this behavioral study describes an antidepressant-like effect of QCF-3 in rodent behavioral models of depression.

Depression and anxiety tend to be the most prevalent conditions among the multitude of neurobehavioural disorders which cause distress in the survivors of traumatic brain injury (TBI). The objective of the present investigation was to examine depression-like and anxiety-like behaviour of rats following diffuse TBI. Impact accelerated TBI was induced in anaesthetised rats by a modified weight drop method. TBI and sham-operated rats received either a chronic (14 days) regimen of escitalopram (5-20 mg/kg) or vehicle, following which they were subjected to a behavioural test battery. The results evince the depression-like behaviour of TBI rats in modified open field exploration, hyperemotionality, socio-sexual interaction and elevated plus-maze exploration paradigms. In addition, an anxiety-like behaviour was evident in social interaction and marble-burying tests. Chronic escitalopram (10 and 20 mg/kg) treatment significantly attenuated the TBI associated behavioural deficits. In conclusion, the aforesaid behavioural anomalies observed in TBI rats are analogous to comorbid anxiety and depression in humans. These findings substantiate the TBI rats as a candidate model of comorbid anxiety and depression.

1-( m -Chlorophenyl)piperazine ( m CPP) has a fairly complex neuropsychopharmacological profile owing to its affinity to multiple serotonergic receptors. This investigation was designed to establish the effect of m CPP on rodent depression-like behaviour. m CPP was screened in a rodent behavioural test battery comprising of validated antidepressant assays and interaction studies with conventional antidepressants and ligands were carried out in forced swim and tail suspension test (in mice). m CPP (1 mg/kg, i.p.) exhibited depressant-like effects in forced swim and tail suspension test (in mice), without influencing the locomotor status. Potentiation of 5-hydroxytryptophan/pargyline induced head twitches (in mice) and hyperthermic effects (in rats) were observed at the same dose level. Further, the behavioural anomalies of the olfactory bulbectomised (OBX) rats were augmented by chronic m CPP (1–2 mg/kg) treatment as observed from the modified open field, elevated plus maze and social interaction paradigms. Interaction studies revealed that the m CPP induced depressant-like effects were reversed by ketanserin, escitalopram, amitriptyline, ziprasidone, venlafaxine pretreatments but not by bupropion, harmane, ondansetron, 8-hydroxy-2-(di- n -propylamino) tetralin (8-OH-DPAT) and MK-801. In conclusion, this study provided ample evidence that the stimulation of 5-HT 2A receptors underlies the depressogenic-like effect of m CPP. Finally, the m CPP induced depression-like behaviour in rodents is envisaged as a modified antidepressant assay to identify novel serotonergic antidepressants.

The anti-serotonergic effects of parthenolide (PTL) demonstrated in platelets inspired the present psychopharmacological investigation, which employs a battery of rodent behavioural assays of depression. In mice, PTL (0.5-2 mg kg−1) exhibited dose-dependent depressant-like effects in a forced swim test and a tail suspension test, without affecting the baseline locomotor status. The doses (1 and 2 mg kg−1) that induced depressant-like effects were found to significantly reduce 5-hydroxytrypto-phan-induced head twitch response. Interaction studies revealed that the depressant-like effects of PTL (1 mg kg−1) were reversed more efficiently by serotonergic antidepressants (venlafaxine, escitalopram, citalopram, fluoxetine) than by others (desipramine, bupropion) tested. Chronic treatment of PTL (1 and 2 mg kg−1) augmented the hyper-emotionality of olfactory bulbectomized rats, when compared with sham rats, as observed in modified open field, elevated plus maze and social interaction paradigms. This study depicts the severe depressogenic potential of PTL (in its pure form) plausibly mediated by platelet/neuronal hypo-serotonergic effects.

A series of novel 3-substituted quinoxalin-2-carboxamides were designed as per the pharmacophoric requirement for 5-HT(3) receptor antagonists and prepared by microwave irradiation and also by conventional method. The compounds were characterized by spectral data (IR, (1)H NMR, and MS) and the purity was ascertained by microanalysis. The synthesized compounds were evaluated for 5-HT(3) antagonisms in longitudinal muscle-myenteric plexus preparation from guinea pig ileum against 5-HT(3) agonist, 2-methyl-5-HT. Among the test compounds, N-{3-[(4-methylpiperazin-1-yl)methyl]-4-hydroxyphenyl}-3-methoxyquinoxalin-2-carboxamide 4e showed most favorable 5-HT(3) receptor antagonism.

INTRODUCTION: Obesity is an important risk factor for depression as more than half of the obese population is susceptible for depression at double rate. Our earlier studies reported the antidepressant potential of 5-HT3receptor antagonist, ondansetron (OND) in depression associated obesity using behavioral tasks. The present research work is aimed to evaluate the effect of OND on depression associated with obesity with special emphasis on biochemical and molecular mechanisms such as hippocampal brain-derived neurotrophic factor (BDNF), cyclic adenosine monophosphate (cAMP), 5-hydroxytryptamine (5-HT), hippocampal histological examination and immunohistochemical expression of p53 proteins. MATERIALS AND METHODS: Mice were fed with high-fat diet (HFD) for 14 weeks, followed by treatment schedule for 28 days with vehicle/OND (0.5 and 1 mg/kg, p.o.)/reference antidepressant escitalopram (10 mg/kg, p.o.). Subsequently, animals were screened in the behavioral tests of depression such as forced swim test (FST) and sucrose preference test (SPT), biochemical estimations including hippocampal cAMP, BDNF and 5-HT, and molecular assays mainly histology and p53 expression of dentate gyrus (DG). RESULTS: HFD-fed mice showed increased immobility time in FST, reduced sucrose consumption in SPT, decreased level of signal transduction factor cAMP, neuronal growth factor BDNF and neurotransmitter 5-HT in the hippocampus, and raised and p53 expression neuronal damage in the DG region of mice fed with HFD in comparison to the mice fed with normal pellet diet. Chronic treatment with OND (0.5 and 1 mg/kg, p.o.) significantly inhibited the behavioral, biochemical and molecular modifications in HFD-fed mice. CONCLUSION: In the preliminary study, OND attenuated depression associated with obesity in mice fed with HFD using various assays procedures, at least in part by the modulation of serotonergic transmission.

Olfactory bulbectomy (OBX) model has been proposed as a well documented model of depression. Accumulated evidences suggest that cAMP selective PDE4 enzyme plays an important role in the pathophysiology of depression disorder. Moreover, PDE4 inhibitors have shown antidepressant-like effect in behavioral despair models. However, the potential of PDE4 inhibitors to produce antidepressant-like effect in OBX model and their underlying mechanism(s) has not been adequately addressed. The present study was designed to investigate the possible antidepressant-like effects and underlying mechanism of rolipram in OBX model. The effects of rolipram were measured in a battery of behavioral paradigms, including hyperactivity in open field test (OFT), anhedonia behavior in sucrose consumption test, open arm activity in elevated plus maze test (EPM) and emotional scores in hyperemotionality test. The underlying signaling mechanisms were also investigated by measuring serum corticosterone (CORT), brain-derived neurotrophic factor (BDNF) and brain oxidant/antioxidant levels. Treatment with rolipram (0.5 and 1 mg/kg, p.o., 14 days) significantly improved the behavioral anomalies (decreased the hyperactivity, open arm activity and hyperemotionality scores, whereas, increased sucrose consumption). Further, rolipram significantly decreased the CORT level and increased cAMP, pCREB and BDNF levels. Additionally, rolipram reduced oxidative–nitrosative stress markers (lipid peroxidation and nitrite levels) and restored the antioxidant enzyme level, including reduced glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT), indicating attenuation of oxidative–nitrosative stress. Our results revealed that antidepressant-like effects of rolipram in OBX model may be mediated by modulating the hypothalamic–pituitary–adrenal (HPA) axis activity, increasing the cAMP signaling aspects and restoring the antioxidant mechanisms.

Olfactory bulbectomy (OBX) is a widely used model for antidepressant screening and known to induce neurodegeneration in several brain areas. Our earlier studies demonstrated that etazolate produced antidepressant-like effects in behavioral despair models of depression; however, the potential role of etazolate on behavior and morphological changes in the hippocampus region along with its underlying mechanism(s) following OBX has not been adequately addressed.We evaluated if etazolate could protect against OBX-induced depression-like behavioral deficits and neurodegeneration. The possible underlying mechanism of etazolate in OBX model was also investigated.The effects of etazolate were measured in a battery of behavioral paradigms, including the forced swim test (FST), sucrose consumption, open arm activity in elevated plus maze (EPM), and hyperemotionality tests. The underlying mechanisms were investigated by measuring serum corticosterone (CORT), cyclic adenosine monophosphate (cAMP), cAMP response element binding protein (CREB), brain-derived neurotrophic factor (BDNF), and oxidative/nitrosative stress (lipid peroxidation and nitrite) levels and antioxidant enzymes, like reduced glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT) levels in the hippocampus.OBX rats showed depression-like behavior anomalies in behavioral paradigms. OBX rats also showed high CORT and decreased cAMP, phosphorylated CREB (pCREB), and BDNF levels. Additionally, we found increased oxidative/nitrosative stress and reduced antioxidant enzyme levels in the hippocampus. Histopathological analysis showed morphological changes and neuronal loss in the hippocampus. Etazolate (0.5 and 1 mg/kg) attenuated the OBX-induced behavioral, biochemical, neurobiological, and histopathological alterations.The aforesaid results suggest that etazolate produces an antidepressant-like effect and neuroprotection in OBX, which is possibly mediated by modulating biochemical and neurobiological markers in the hippocampus.

1, 8-naphthyridine-3-carboxylic acid analogs were synthesized and found to possess potential 5-HT3 receptor antagonism as well as antidepressant-like activity. Initially, 5-HT3 receptor antagonism of all the compounds was determined in the form of pA2 value against agonist 2-methyl 5-HT in longitudinal muscle-myenteric plexus preparation from guinea-pig ileum. Among all the compounds tested, compound 7a demonstrated most promising pA2 value of 7.6. Subsequently, all the compounds were evaluated for antidepressant activity using forced swim test and tail suspension test in mice. Compounds 7a, 7d, 7f, 7h, and 7i exhibited significant (p < 0.05) antidepressant-like activity as compound to vehicle-treated group. Importantly, none of the tested compound affected locomotor activity of mice at tested dose levels.

Background The inconsistent therapeutic outcome necessitates designing and identifying novel therapeutic interventions for depression. Hence, the present study deals with the investigation of antidepressant-like effects of a novel 5-HT3 receptor antagonist (4-phenylpiperazin-1-yl) (quinoxalin-2-yl) methanone (4a) on chronic unpredictable mild stress (CUMS) induced behavioral and biochemical alterations. Methods Animals were subjected to different stressors for a period of 28 days. On day 15 after the subsequent stress procedure, mice were administered with (4a) (2 and 4 mg/kg p.o.), escitalopram (10 mg/kg p.o.), or vehicle (10 mL/kg p.o.) until day 28 along with the CUMS. Thereafter, behavioral battery tests like locomotor score, sucrose preference test, forced swim test (FST), tail suspension test (TST), and elevated plus maze (EPM) were performed. Biochemical assays like lipid peroxidation, nitrite levels, reduced glutathione (GSH), catalase, and superoxide dismutase (SOD) were estimated in the mice brain homogenate. Results (4a) Dose dependently attenuated the behavioral alterations by increasing the sucrose consumption, reducing the immobility time in FST and TST, increasing the open arm number of entries and time in EPM. Furthermore, biochemical alterations were reversed by (4a) as examined by reduced lipid peroxidation and nitrite levels and elevated antioxidant enzyme levels like GSH, catalase and SOD. Conclusions (4a) exhibits antidepressant potential by reversing the CUMS induced behavioral and biochemical changes in mice.

A series of novel 1,8-naphthyridine-3-carboxamides as 5-HT3 receptor antagonists were synthesized with an intention to explore the antidepressant activity of these compounds. The title carboxamides were designed using ligand-based approach keeping in consideration the structural requirement of the pharmacophore of 5-HT3 receptor antagonists. The compounds were synthesized using appropriate synthetic route from the starting material nicotinamide. 5-HT3 receptor antagonism of all the compounds, which was denoted in the form of pA2 value, was determined in longitudinal muscle myenteric plexus preparation from guinea-pig ileum against 5-HT3 agonist, 2-methyl-5-HT. Compound 8g (2-methoxy-1, 8-naphthyridin-3-yl) (2-methoxy phenyl piperazine-1-yl) methanone was identified as the most active compound, which expressed a pA2 value of 7.67. The antidepressant activity of all the compounds was examined in mice model of forced swim test (FST); importantly, none of the compounds was found to cause any significant changes in the locomotor activity of mice at the tested dose levels. In FST, the compounds with considerably higher pA2 value exhibited promising antidepressant-like activity, whereas compounds with lower pA2 value did not show antidepressant-like activity as compared to the control group.

The present study was designed to evaluate the antidepressant potential of 5-HT3 receptor antagonist N-n-propyl-3-ethoxyquinoxaline-2-carboxamide (6n). The compound '6n' with optimum log P and pA 2 value identified from a series of compounds synthesized in our laboratory was subjected to forced Swim Test (FST) (1, 2, and 4 mg/kg, i.p) and Tail Suspension Test (TST) (1, 2, and 4 mg/kg, i.p.). The compound '6n' significantly reduced the duration of immobility in mice without affecting the baseline locomotion. Moreover, '6n' (2 mg/kg, i.p.) potentiated the 5-hydroxytryptophan (5-HTP)-induced head twitch responses in mice and '6n' at tested dose (1 and 2 mg/kg, i.p.) reversed the reserpine-induced hypothermia in rats. In interaction studies of '6n' with various standard drugs/ligands using FST, '6n' (1 mg/kg, i.p.) potentiated the antidepressant effect of venlafaxine (4 and 8 mg/kg, i.p.) and fluoxetine (10 and 20 mg/kg, i.p.). Additionally, '6n' (1 and 2 mg/kg, i.p.) influenced the effect of harmane (5 mg/ kg, i.p.) as well as reversed the effect of parthenolide (1 mg/kg, i.p.) by reducing the duration of immobility in FST. Furthermore, '6n' (1 mg/kg, i.p.) potentiated the effect of bupropion (10 and 20 mg/kg, i.p.) in TST. Chronic '6n' (1 and 2 mg/kg, i.p.) treatment attenuated the behavioral abnormalities in olfactory bulbectomized rats. In conclusion, these various findings reiterated the antidepressant-like effects of '6n' in behavioral models of depression.

Objective: The present study was designed to investigate the antidepressant potential of N-n-butyl-3-ethoxyquinoxalin-2-carboxamide ( 6p ), a novel 5-HT 3 receptor antagonist in rodent behavioral models of depression. Materials and Methods: The compound 6p was examined in various behavioral models like forced swim test (FST), tail suspension test (TST), mechanistic models [5-hydroxytryptophan (5-HTP)-induced head twitch and reserpine-induced hypothermia (RIH)], and in chronic surgery model-olfactory bulbectomy in rats. Results: Compound 6p (1, 2, and 4 mg/kg, i.p.) exhibited antidepressant-like effect in FST and TST after acute treatment without having an effect on baseline locomotor activity. Moreover, 6p (2 mg/kg, i.p.), potentiated the 5-HTP-induced head twitch responses in mice and inhibited the RIH in rats. Chronic treatment (14 days) with 6p (1 and 2 mg/kg, p.o.) and paroxetine (10 mg/kg, p.o.) in rats significantly reversed the behavioral anomalies induced by bilateral olfactory bulbectomy using open field exploration. Conclusion: The preliminary studies reveal that compound 6p exhibits antidepressant-like effect in behavioral rodent models of depression.

Employing a ligand-based approach, 3-methoxyquinoxalin-2-carboxamides were designed as serotonin type-3 (5-HT3) receptor antagonists and synthesized from the starting material ophenylenediamine in a sequence of reactions. The structures of the synthesized compounds were confirmed by spectral data. These carboxamides were investigated for their 5-HT3 receptor antagonisms in longitudinal muscle myenteric plexus preparations from guinea-pig ileum against a standard 5-HT3 agonist, 2-methy-5-HT, and their antagonism activities are expressed as pA2 values. Compounds 6a(pA2: 7.2),6e(pA2: 7.0), 6f(pA2: 7.5),6g (pA2: 7.5),6n(pA2: 7.0), and6o(pA2: 7.2) exhibited antagonism greater than that of the standard 5-HT3 antagonist, ondansetron (pA2: 6.9).

A series of 3-chloroquinoxaline-2-carboxamides were designed and prepared by the condensation of 3-chloro-2-quinoxaloylchloride with appropriate Mannich bases of the p-aminophenol in the microwave environment. The synthesized compounds were evaluated for serotonin(3) (5-HT(3)) receptor antagonistic activities in longitudinal muscle-myenteric plexus (LMMP) preparation from guinea pig ileum against the 5-HT(3) agonist, 2-methyl-5-HT. Compound 3g exhibited comparable 5-HT(3) antagonistic activity (pA(2) 6.4) to that of standard antagonist Ondansetron (pA(2) 6.9), while the other compounds exhibited mild to moderate 5-HT(3) antagonistic activities.

Etazolate, a pyrazolopyridine class compound is selective inhibitor of type 4 phosphodiesterase (PDE4). Previous study in our laboratory has demonstrated that etazolate produced antidepressant-like effect in rodent models of behavioral despair. The present study was designed to investigate whether etazolate could affect the chronic unpredictable mild stress (CUMS)-induced depression in mice. The effect of etazolate on CUMS-induced depression was examined by measuring behavioral parameters and oxidant/antioxidant status of brain tissue. Mice were subjected to different stress paradigms daily for a period of 28days to induce depressive-like behavior. The results showed that CUMS caused depression-like behavior in mice, as indicated by significant (p0.05) decrease in sucrose consumption and increase in duration of immobility. Moreover, CUMS also significantly (p0.05) increased the oxidative stress markers and decreased the antioxidant enzymes activity. Chronic administration of etazolate (0.5 and 1mg/kg., p.o.) and fluoxetine (20mg/kg., p.o.) significantly (p0.05) inhibited the CUMS-induced behavioral (decreased sucrose consumption and increased duration of immobility) and biochemical (increased lipid peroxidation and nitrite level; decreased glutathione, superoxide dismutase and catalase activity) changes. No alteration was observed in locomotor activity. Additionally, in the present study, the efficacy of etazolate (1mg/kg., p.o.) on the behavioral and biochemical paradigms was found comparable to that of fluoxetine, used as standard antidepressant. In conclusion, the results of the present study suggested that etazolate alleviated the CUMS-induced depression in mice, which is at least in part mediated by modulating oxidative-nitrosative stress status in mice brain.

Aim: Depression and anxiety are among the most common and prevalent forms of mental disorder. The 5-hydroxytryptamine3 (5-HT 3 ) receptor antagonists modulate serotonergic pathways and show antidepressant- and anxiolytic-like effect in various animal models of depression. The present study was designed to investigate the antidepressant and anxiolytic potential of 2-[4-(3-chlorophenyl) piperazin-1-yl]- 1,8-naphthyridine-3-carboxylic acid (7e), a novel 5-HT 3 receptor antagonist in rodent behavioral models of depression and anxiety. Materials and Methods: The compound 7e was tested using different behavioral models for depression and anxiety such as forced swim test (FST), tail suspension test (TST), mechanistic models such as 5-hydroxytryptophan (5-HTP)-induced head twitch, elevated plus maze (EPM), hole-board (HB) test, open field test (OFT), and light and dark (L and D) aversion test. Results: The compound 7e (1 and 2 mg/kg, intraperitoneally [i.p.]) exhibits antidepressant-like effect in FST. In addition, compound 7e (0.5, 1 and 2 mg/kg, i.p.) exhibits antidepressant-like effect in TST after acute treatment without any significant effect on base line spontaneous locomotor activity. Moreover, compound 7e (2 mg/kg, i.p.) potentiated the 5-HTP-induced head twitch responses in mice. In interaction studies, compound 7e (0.5 mg/kg, i.p.) potentiated the antidepressant effect of bupropion. Furthermore, compound 7e also exhibited anxiolytic-like effect in EPM, HB test, OFT, and L and D aversion test. Conclusion: These preliminary studies reveal that compound 7e exhibits antidepressant- and anxiolytic-like effect in behavioral rodent models of depression and anxiety.

Etazolate, a pyrazolopyridine class derivative is selective inhibitor of type 4 phosphodiesterase (PDE4), an enzyme catalyzes the hydrolysis of cyclic nucleotide viz. cAMP & regulates cAMP signal transduction. Enhancing cAMP signal transduction by inhibition of PDE4 is known to be beneficial in depression disorders. Thus, the present study was designed to investigate thoroughly the antidepressant potential of etazolate using rodent behavioral models of depression. Acute treatment of etazolate (0.25–1 mg/kg, i.p.) exhibited antidepressant-like effects in forced swim test (FST) & tail suspension test (TST) in mice without influencing the baseline locomotion in actophotometer test. Interaction studies of etazolate sub-effective dose (0.12 mg/kg, i.p.), were carried out with sub-effective dose of conventional antidepressants like fluoxetine (5 mg/kg, i.p.), venlafaxine (4 mg/kg, i.p.) & desipramine (5 mg/kg, i.p.) in FST. Etazolate at sub-effective dose produced synergistic antidepressant-like effect with conventional antidepressants in the mouse FST. In addition, combined treatment of etazolate & conventional antidepressants had no significant effect on baseline locomotion. Moreover, etazolate (0.5 and 1 mg/kg, i.p.) increased head twitch scores in mice & antagonized the reserpine-induced hypothermia in rats. Chronic treatment (14 days) with etazolate (0.5 and 1 mg/kg, p.o.) & fluoxetine (10 mg/kg, p.o.) significantly reversed the behavioral anomalies induced by bilateral olfactory bulbectomy in rats in modified open field exploration. In conclusion, taken together, our results suggested that etazolate exhibited antidepressant-like activity in acute & chronic rodent models of depression & deserves as a therapeutic tool that could help the conventional pharmacotherapy of depression.

Linezolid, an oxazolidinone class derivative is a reversible and nonselective inhibitor of monoamine oxidase (MAO), predominantly for MAO-A type. MAO-A is a key enzyme regulating the catabolism of catecholamine neurotransmitters in the brain. It is well known that the catecholaminergic neuronal systems are associated with depression and inhibition of MAO-A level in the brain could be used to treat depression. Hence, the objective of this study was to evaluate the anti-depressant-like effect of linezolid, a MAO-A inhibitor in the animal models of depression. In the present study, linezolid (10 & 20mg/kg, i.p.), exhibited anti-depressant-like effects in forced swim test (FST) and tail suspension test (TST) in mice without influencing the baseline locomotion. Moreover, linezolid (10 & 20mg/kg, i.p.), potentiated the 5-hydroxytryptophan (5-HTP)-induced head twitch responses in mice and antagonized the reserpine-induced hypothermia in rats. In conclusion, the behavioral investigation revealed the anti-depressant-like effect of linezolid in rodent's behavioral model.

A series of quinoxalin-2-carboxamides were designed as per the pharmacophoric requirements of 5-HT(3) receptor antagonists and synthesized by condensing the carboxylic group of quinoxalin-2-carboxylic acid with various amines in the presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole. The structures of the synthesized compounds were confirmed by physical and spectroscopic data. The carboxamides were evaluated for their 5-HT(3) receptor antagonisms in longitudinal muscle-myenteric plexus preparation from guinea pig ileum against 5-HT(3) agonist, 2-methy-5-HT. All the synthesized compounds showed 5-HT(3) receptor antagonism, (4-benzylpiperazin-1-yl)(quinoxalin-2-yl)methanone was the most potent compound among this series.

A novel series of 3-ethoxyquinoxalin-2-carboxamides were designed as per the pharmacophoric requirements of 5-HT(3) receptor antagonist using ligand-based approach. The desired carboxamides were synthesized from the key intermediate, 3-ethoxyquinoxalin-2-carboxylic acid by coupling with appropriate amines in the presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) and 1-hydroxybenzotriazole (HOBt). The 5-HT(3) receptor antagonism was evaluated in longitudinal muscle myenteric plexus preparation from guinea pig ileum against 5-HT(3) agonist, 2-methy-5-HT, which was expressed in the form of pA(2) values. Compound 6h (3-ethoxyquinoxalin-2-yl)(4-methylpiperazin-1-yl)methanone was found to be the most active compound, which expressed a pA(2) value of 7.7. In forced swim test, the compounds with higher pA(2) value exhibited good anti-depressant-like activity and compounds with lower pA(2) value failed to show activity as compared to the vehicle-treated group.

Collective evidence suggests that inhibition of neuronal 5-hydroxytryptamine type 2A (5-HT(2A)) receptors contributes to the assuagement of depression-like behaviour in rodents. The present study evaluated the antidepressant-like effect of the 5-((4-benzo [alpha] isothiazol-3-yl) piperazin-1-yl) methyl)-6-chloroindolin-2-one (BIP-1), a compound having affinity to 5-HT(2A) receptors, using a rodent behavioural test battery. Acute BIP-1 (0.25-4mg/kg) pretreatment reduced the quipazine-induced head twitches in mice and produced antidepressant-like effects in mouse forced swim and tail suspension tests. BIP-1 reversed the depressogenic-like effects of meta-chlorophenyl piperazine and augmented the antidepressant-like effects of amitryptiline and harmane. Chronic (14days) treatment with BIP-1 (1 and 2mg/kg) or amitriptyline (10mg/kg) alleviated the behavioural anomalies of olfactory bulbectomised rats in modified open field exploration, social interaction, hyperemotionality and sucrose preference paradigms. When BIP-1 treatment was combined with amitryptyline, a short duration regimen (7days) was sufficient to reverse the bulbectomy induced anomalies. This investigation revealed that 5-HT(2A) receptor antagonism is the principal mechanism behind the antidepressant-like effects of BIP-1. Finally, we propound the combination of 5-HT(2A) receptor antagonists and tricyclic antidepressants as a likely strategy to achieve an early-onset of antidepressant action.

A series of novel 3-substituted quinoxalin-2-carboxamides were designed as per the pharmacophoric requirement for 5-HT(3) receptor antagonists and prepared by microwave irradiation and also by conventional method. The compounds were characterized by spectral data (IR, (1)H NMR, and MS) and the purity was ascertained by microanalysis. The synthesized compounds were evaluated for 5-HT(3) antagonisms in longitudinal muscle-myenteric plexus preparation from guinea pig ileum against 5-HT(3) agonist, 2-methyl-5-HT. Among the test compounds, N-{3-[(4-methylpiperazin-1-yl)methyl]-4-hydroxyphenyl}-3-methoxyquinoxalin-2-carboxamide 4e showed most favorable 5-HT(3) receptor antagonism.

A series of novel 2-(4-substituted piperazin-1-yl)-1,8-naphthyridine-3-carbonitrile 6 were prepared by microwave irradiation and conventional heating. The intermediate, 2-oxo-1,2-dihydro-1,8-naphthyridine-3-carbonitrile 3, was prepared from 2-aminonicotinaldehyde 1 and ethyl cyanoacetate 2 in the presence of piperidine under solvent free condition. The synthesized compounds were evaluated for 5-HT3 antagonisms in longitudinal muscle-myenteric plexus (LMMP) preparation from Guinea pig ileum against 5-HT3 agonist, 2-methyl-5-HT. Among the compounds tested, 2-(4-allylpiperazin-1-yl)-1,8-naphthyridine-3-carbonitrile 6d showed most favorable 5-HT3 receptor antagonism in the Guinea pig ileum.