|Year : 2016 | Volume
| Issue : 2 | Page : 81-89
Antidepressant- and anxiolytic-like effect of novel 5-hydroxytryptamine3 receptor antagonist 2-[4-(3-chlorophenyl) piperazin-1-yl]-1,8-naphthyridine -3-carboxylic acid (7e)-: An approach using rodent behavioral antidepressant and anxiolytic test battery
Shvetank Bhatt1, Shreyas Mukund Bagal2, Sandeep Butola2, Arghya Kusum Dhar2, Radhakrishnan Mahesh2
1 Department of Pharmacology, Faculty of Pharmacy, M.S. Ramaiah University of Applied Sciences, Bengaluru, Karnataka, India
2 Department of Pharmacy, Birla Institute of Technology and Science, Pilani, Rajasthan, India
|Date of Web Publication||11-Apr-2016|
Department of Pharmacology, Faculty of Pharmacy, M.S. Ramaiah University of Applied Sciences, Bengaluru - 560 054, Karnataka
Source of Support: None, Conflict of Interest: None
| Abstract|| |
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.
Keywords: 5-hydroxytryptamine3 receptor antagonists, antidepressant, forced swim test, Serotonin, tail suspension test
|How to cite this article:|
Bhatt S, Bagal SM, Butola S, Dhar AK, Mahesh R. Antidepressant- and anxiolytic-like effect of novel 5-hydroxytryptamine3 receptor antagonist 2-[4-(3-chlorophenyl) piperazin-1-yl]-1,8-naphthyridine -3-carboxylic acid (7e)-: An approach using rodent behavioral antidepressant and anxiolytic test battery. Int J Nutr Pharmacol Neurol Dis 2016;6:81-9
|How to cite this URL:|
Bhatt S, Bagal SM, Butola S, Dhar AK, Mahesh R. Antidepressant- and anxiolytic-like effect of novel 5-hydroxytryptamine3 receptor antagonist 2-[4-(3-chlorophenyl) piperazin-1-yl]-1,8-naphthyridine -3-carboxylic acid (7e)-: An approach using rodent behavioral antidepressant and anxiolytic test battery. Int J Nutr Pharmacol Neurol Dis [serial online] 2016 [cited 2019 Oct 15];6:81-9. Available from: http://www.ijnpnd.com/text.asp?2016/6/2/81/179968
| Introduction|| |
Major depressive disorder and anxiety disorders are among the most prevalent forms of mental illness. According to the World Health Organization, depression is expected to be the second major cause of disability by 2020 after ischemic heart disease. , In depression, lifetime preponderance of disability is around 15-20%.  Females are two times more prone to depression than males, a rough affliction of 1-2% in case of bipolar disorder is observed equally in males and females.  An estimated annual economic burden of above $42 billion is accountable in the United States for anxiety disorders which are among the most common mental health conditions.  Around 6% of the general population tends to qualify for generalized anxiety disorder (GAD) diagnosis at some time in their lifetime.  The presence of anxiety disorders is reported in both adults and adolescents in 33.70% and 32.40%, respectively.  An excessive, uncontrollable worry across several arena lasting at least 6 months duration is associated with significant functional impairment are characterized in the current Diagnostic and Statistical Manual of Mental Disorders - Fifth Edition-Text Revision (DSM-IV-TR) for GAD.  According to DSM-IV-TR criteria for depression, at least five of the following symptoms should be present during the same 2 weeks: Depressed mood, anhedonia, significant weight loss or weight gain, insomnia or hypersomnia, psychomotor agitation, fatigue, suicidal tendency, etc. 
Serotonin (5-hydroxytryptamine3 [5-HT 3 ]) receptor antagonists are widely used in the management of nausea and vomiting which is associated with cancer chemotherapy.  Several neuropharmacological studies prove the relation between 5-HT 3 receptor and depression as well as anxiety. 5-HT 3 receptor antagonist molecules have been used to a larger extent in various preclinical and clinical studies and are evaluated for their neuropsychopharmacological potentials.  On the basis of study conducted using ondansetron (selective 5-HT 3 receptor antagonist), local cerebral glucose utilization in the rat median raphe was found to be altered, and anti-immobility effects of selective serotonin reuptake inhibitors were potentiated. The study also indicates the role played by 5-HT 3 receptors in depression. ,
The compound 2 [4 (3 chlorophenyl) piperazin 1 yl] 1,8 naphthyridine 3 carboxylic acid (7e) [Table 1], selective 5 HT3 receptor antagonist, has shown to reduce the duration of immobility in the mouse tail suspension test (TST) and forced swim test (FST).  In a similar manner, compound 7e also exhibits anxiolytic-like effect in hole-board (HB) test, elevated plus maze (EPM), light and dark (L and D) model, and open field test (OFT).  On the basis of the abovementioned studies, the hypothesis of the antidepressant and anxiolytic effects of 5-HT 3 receptor antagonists and the role of 5-HT 3 receptors in the neurobiology of depression and anxiety respectively are strengthened by various preclinical studies. Several commercially available antidepressants such as fluoxetine, imipramine, phenelzine, and iproniazid exhibited antidepressant-like activity by blocking 5-HT 3 receptors.  Similarly, ondansetron, bemesetron, tropisetron, zacoprade, and itasetron are 5-HT 3 receptor antagonists showing anxiolytic effect. 
|Table 1: Physical constants of 2-(4-substituted piperazin-1-yl)-1,8-naphthyridine-3-carboxylic acids |
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| Materials And Methods|| |
Albino mice (25 ± 2 g) and Wistar rats (250 ± 20 g) were obtained from Agricultural University, Hissar, Haryana, India. All procedures were in adherence to the Institutional Animal Ethics Committee (IAEC) of Birla Institute of Technology and Science, Pilani, India (Protocol No. IAEC/RES/18/08, dated February 24, 2014). The animals were kept for at least 1 week before the experiments, at optimum temperature (23 ± 2°C) and humidity-controlled (50-60%) animal rooms under a 12:12 h light/dark cycle (light on 6.00-18.00 h) with free access to food and water ad libitum. Behavioral studies were carried out during the light phase (9.00 a.m-2.00 p.m). The animals were used only once for each experiment.
Chemistry of 2-[4-(3-chlorophenyl) piperazin-1-yl]- 1,8-naphthyridine-3-carboxylic acid
The targeted compound 2 [4 (3 chlorophenyl) piperazin 1 yl] 1,8 naphthyridine 3 carboxylic acid (7e) was synthesized in a sequence of reaction as shown in [Figure 1].  The structure of the synthesized compound was confirmed by the spectral data: Fourier transform-infrared spectroscopy (KBr/cm): 3290, 3172, 2831, 2750, 2644, 2358, 2328, 1749, 1625, 1510, 1462, 1350. 1H NMR, CDCl3, d (ppm): 8.92-8.91 (m, 1H, naphthyridine); 8.44 (s, 1H, naphthyridine), 8.01-7.99 (m, 1H, naphthyridine), 7.27-7.24 (m, 1H, naphthyridine), 7.19-7.10 (m, 1H, phenyl), 6.90-6.88 (m, 1H, phenyl), 6.83-6.73 (m, 1H, phenyl), 6.72-6.68 (m, 1H, phenyl), 3.50-3.45 (m, 4H, piperazine), 3.34-3.28 (m, 4H, piperazine). 13C-NMR, DMSO-d6: D (ppm) 170.72, 157.40,154.03, 152.38, 151.93, 151.31, 138.17, 136.57, 134.04, 133.94, 130.19, 130.03, 125.25, 119.18, 118.42, 47.40,47.14, 45.65, 42.54. MS (ESIve mode, ESI + ve mode): m/z (%) =367.1 (M-H+, 100) 369.0 (M + H+, 100).
|Figure 1: Synthetic route of 2-(4-substituted piperazin-1-yl)-1,8-naphthyridine-3-carboxylic acids; reagents and conditions: (a) Ammonium sulfamate, neat, 200°C, 20-24 h, 64%; (b) 4N HCl, 100°C, 1-2 h, 38%; (c) diethyl malonate, EtOH, reflux, 4-5 h, 60%; (d) POCl3, cat. DMF, 1-2 h, 67%; (e) K2CO3, acetonitrile, piperazines, 80°C, 1-2 h (f) 10% aq. NaOH, rt, 1 h, aq. citric acid|
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Drugs and chemicals
Duloxetine (DUL), bupropion (BUP), diazepam, and fluoxetine (FLX) were obtained as gift samples from Cipla Pharmaceuticals and IPCA Laboratories Private Limited, Mumbai, Maharashtra, India, respectively. The drugs for anesthesia, namely, ketamine and xylazine were purchased from Reidel Neon Labs, Indian Immunologicals (Mumbai, India). The drugs were freshly prepared in distilled water and administered per oral (p.o.) or intraperitoneally (i.p.) in a constant volume of 10 ml/kg. For interaction studies, the antidepressants/ligands and standards were administered i.p., 45 and 30 min, respectively, before testing in FST and TST as per the protocol adopted, earlier in our laboratory. The drugs were administered p.o. once a day for 14 days in the chronic treatment schedule.
5-hydroxytryptamine3 receptor antagonistic activity
The compounds were tested for their ability to inhibit the 5-HT 3 receptor in isolated guinea-pig ileum, and the pA 2 values were determined against 2-methyl-5-hydroxytryptamine. , To assess the 5-HT 3 receptor antagonistic activity, guinea-pigs were sacrificed with ketamine (40 mg/kg, i.p.) and xylazine (5 mg/kg, i.p.). The abdomen was cut open and a length of ileum excised about 2 cm from the ileocecal junction, the longitudinal muscle-myenteric plexus, 3-4 cm in length, was prepared and mounted as cited in the literature. The tissue was equilibrated for 30 min under a resting tension of 500 mg with constant aeration in a 40 ml organ bath containing tyrode solution, maintained at 37°C The physical constants of compound 7e have been mentioned in [Table 1].
Noncumulative concentrations of 2-methyl-5- hydroxytryptamine (HT) were added with a 15 min dosing cycle (to prevent desensitization) and left in contact with the tissue until the maximal contraction had developed. To study the antagonist effect of the test compounds on the response evoked by 2-methyl-5-HT, the compounds were added to the organ bath and left in contact with the tissue for at least 10 min before the addition of 2-methyl-5-HT. The contractions were recorded using a T-305 Force Transducer coupled to a Student's Physiograph (Bio Devices, Ambala, India). Antagonism was expressed in the form of pA 2 values, which were graphically determined. The pA 2 values of the test compound were compared with the standard antagonist, ondansetron.
Forced swim test
The FST was carried out as described elsewhere  with slight modifications.  Mice were dropped individually into a plexi-glass cylinder (height 30 cm; diameter 22.5 cm) filled with water to a depth of 15 cm and maintained at 23-25°C. After an initial vigorous activity (2 min), the mice acquire an immobile posture, making only those movements necessary to keep the head above the water. The duration of immobility was recorded during the last 4 min of the 6-min test. The mice were subjected to 15 min training under similar conditions, 24 h before the test.
Tail suspension test
Mice were individually suspended by the tail to a horizontal bar (distance from floor was 50 cm) using scotch tape (distance from tip of tail was approximately 1 cm). Typically, mice exhibited several escape-oriented behavior interspersed with temporally increasing bouts of immobility. The duration of immobility (in seconds) during the 6-min test session was recorded. ,
Spontaneous locomotor activity
The spontaneous locomotor activity (SLA) was assessed using an actophotometer.  The animals were individually placed in a square arena (30 cm × 30 cm) with walls painted black and are fitted with photocells just above the floor level. The photocells were checked before the beginning of the experiment. After an initial 2-min familiarization period, the digital locomotor scores were recorded for the next 10 min in a dimly lit room. The arena was cleaned with dilute alcohol and dried between trials.
5-Hydroxytryptophan-induced head twitch response
The method mentioned elsewhere  was adopted with slight modifications. The vehicle/drug treated mice were injected with pargyline (75 mg/kg i.p.) and 5-hydroxytryptophan (5-HTP) (5 mg/kg), 30 and 15 min before drug administration, respectively, and gently placed in separate, clear plexi-glass cages (12 cm × 12 cm × 10 cm). The total number of head twitches (characterized by abrupt lateral movements) episodes was recorded for the next 15 min.
The animals were treated either with vehicle or with one of the following test compounds, namely, paroxetine (10 and 20 mg/kg, i.p.) - a selective serotonin re-uptake inhibitor, desipramine (10 and 20 mg/kg, i.p.), tricyclic antidepressant, parthenolide (1 mg/kg i.p.) - a serotonin release inhibitor, and BUP (10 and 20 mg/kg, i.p.). All the standard drug doses were adopted from the previous work and standard responses recorded. ,
Elevated plus maze
EPM test was first evaluated for rats  and later adapted for mice.  In brief, the apparatus consisted of wooden maze with two enclosed arms (30 cm × 5 cm × 15 cm) and two open arms (30 cm × 5 cm × 0.25 cm) that extended from a central platform (5 cm × 5 cm) to form a plus sign. The plus-maze apparatus was elevated to a height of 45 cm and placed inside a sound-attenuated room. The trial was started by placing a mouse on the central platform of the maze facing its head toward an open arm. The behavioral performances recorded during a 5-min test period were percentage open arm entries and percentage time spent in open arm.  Entry into an arm was considered valid only when all four paws of the mouse were inside the arm.  The animal activities were tracked and recorded via an overhead video camera linked to a monitor with computer software Smart version 2.5 (Panlab Co., MA, USA). The apparatus was thoroughly cleaned with 70% ethanol after each trial.
The HB test apparatus consisted of a gray PLEXIGLAS platform (40 cm × 40 cm) raised to a height of 15 cm from the floor of a gray wooden box (40 cm × 40 cm × 40 cm). The gray wooden Plexiglas platform consisted of 16 equivalent square compartments (12 peripheral and 4 central), each featuring a central circular hole (3 cm diameter). Test session was started by placing each animal in the center of the HB and was allowed to freely explore on the apparatus for 5 min. The behavioral performances such as number of head dippings and latency to the first head dipping  were tracked and recorded using computer software Smart Version 2.5 (Panlab Co., MA, USA).
Open field test
The apparatus consisted of a wooden box (60 cm × 60 cm × 30 cm) with the floor divided into 16 squares (15 cm × 15 cm) by black intersecting and parallel lines. The apparatus was illuminated with 60 W bulb suspended 100 cm above. At the beginning of the test, the mouse was placed individually at the center of the square arena. The ambulation scores (number of the squares crossed) and retaining number (standing upright on the hind legs) were recorded using computer software Smart Version 2.5 (Panlab Co., USA) for 5 min period. After each test session, the floor was thoroughly cleaned with 70% ethanol. 
Light and dark aversion test
The L and D apparatus comprised a box divided into two separate compartments, occupying two-third and one-third of the total size, respectively. The larger compartment (light compartment) was illuminated by a 60 W bulb while the smaller (dark compartment) was entirely dark and enclosed under a dark cover. The L and D compartments were separated by a partition with a tunnel to allow passage from one compartment to the other.  At the beginning of the test, the mouse was placed individually at the center of the light compartment facing toward the tunnel and was allowed to explore the entire apparatus for 5 min. The behavioral parameters such as the total time spent in the light compartment and number of transitions between the L and D compartments were tracked and recorded using computer software Smart Version 2.5 (Panlab Co., USA). A compartment entry was considered valid when the animal's all four paws were inside that chamber. The apparatus was thoroughly cleaned with 70% ethanol after each trial.
Data were expressed as the mean ± standard error of mean. The single treatment studies were analyzed using a one-way analysis of variance followed by a post-hoc Dunnett test. The interaction studies were analyzed using a two-way analysis of variance followed by a post-hoc Tukey test. The level of statistical significance was fixed at P < 0.05.
| Results|| |
Based on the pA 2 and log P values, compound 7e was taken for extensive behavioral pharmacological testing from among the series of compounds.
In FST, the acute treatment with 7e (1 and 2 mg/kg, i.p.) significantly decreased the duration of immobility as compared to vehicle treatment [Figure 2], whereas there was significant effect observed at dose of 0.5 mg/kg, i.p. in FST. Moreover, in TST, the acute treatment with 7e (0.5, 1 and 2 mg/kg, i.p.) significantly decreased the duration of immobility as compared to vehicle control [Figure 3]. The standard antidepressants, DUL (10 mg/kg, i.p.) and BUP (20 mg/kg, i.p.) also significantly reduced the immobility duration in FST and TST, respectively, as compared to the control group. None of the tested doses influenced the locomotion of mice in actophotmeter [Figure 4]. Compound 7e (0.5 mg, i.p.) ecreases the duration of immobility when used in combination with standard bupropion (10 & 20 mg/kg, i.p.) as shown in [Figure 5].
|Figure 2: Effect of 2-[4-(3-chlorophenyl) piperazin-1-yl]-1,8-naphthyridine-3-carboxylic acid on duration of immobility of mice forced swim test. The columns represent mean duration of immobility in seconds (s) and error bars indicate standard error of mean n = 6 per group. *P < 0.05 compared with vehicle-treated group. DUL = Duloxetine|
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|Figure 3: Effect of 2-[4-(3-chlorophenyl) piperazin-1-yl]-1,8-naphthyridine-3-carboxylic acid on duration of immobility of mice tail suspension test. The columns represent mean duration of immobility in seconds (s) and error bars indicate standard error of mean n = 6 per group. *P < 0.05 compared with vehicle-treated group. BUP = Bupropion|
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|Figure 4: Effect of 2 [4 (3 chlorophenyl) piperazin 1 yl] 1,8 naphthyridine 3 carboxylic acid on SLA of mice forced swim test and tail suspension test. The columns represent mean duration of immobility in seconds (s) and error bars indicate standard error of mean n=6 per group|
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|Figure 5: Effect of 2-[4-(3-chlorophenyl) piperazin-1-yl]-1,8-naphthyridine-3-carboxylic acid (0.5 mg/kg) on antidepressant activity of bupropion (10 and 20 mg/kg) in mice forced swim test. The columns represent mean duration of immobility (s) and error bars indicate standard error of mean, n = 6 per group. *P < 0.05 compared with vehicle-treated group, #P < 0.05 compared with paroxetine-treated group. BUP = Bupropion|
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The 5-HTP-induced head twitches were performed to confirm the involvement of serotonergic pathway. The combination of 5-HTP (5 mg/kg, i.p.) and pargyline (75 mg/kg, i.p.) induced the characteristic head twitch response. The compound 7e (2 mg/kg, i.p.) and FLX (10 mg/kg, i.p.) significantly potentiated the 5-HTP/pargyline-induced head twitches, respectively [Figure 6].
|Figure 6: Effect of 2-[4-(3-chlorophenyl) piperazin-1-yl]-1,8-naphthyridine-3-carboxylic acid and fluoxetine on 5-hydroxytryptophan (5 mg/kg) + pargyline (75 mg/kg)-induced head twitch response in mice. The columns represent mean number of head twitches and error bars indicate standard error of mean n = 6 per group. *P < 0.05 compared with vehicle-treated group. FLX = Fluoxetine|
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Elevated plus maze
The effects of 7e on the behavior of albino mice were analyzed in EPM paradigm [Table 2]. The dose levels of 7e (0.5, 1.0, and 2.0 mg/kg, i.p.) were selected based on the data obtained from FST and TST. Treatment with 7e significantly (P < 0.05) increased the percentage time spent in the open arms and percentage number of entries into open arms in albino mice compared to control group albino mice. Diazepam treatment (1 and 2 mg/kg, i.p.) also significantly increased the percentage time spent in the open arms and percentage number of entries into open arms in albino mice as compared to control group albino mice.
|Table 2: Effects of diazepam (1.0 and 2.0 mg/kg) and 7e (0.5, 1.0, and 2.0 mg/kg) on elevated plus maze behavior (% time spent in open arm, % time spent in closed arm, % number of open arm entries, and % number of closed arm entries) in albino mice |
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The results of the HB test are shown in [Table 3]. Here, 7e (1.0 and 2.0 mg/kg, i.p.) and diazepam (2 mg/kg, i.p.) treatment significantly (P < 0.05) decreased the nose poking latency and increased the number of nose pokings as compared to the control group mice. Lower dose of 7e (0.5 mg/kg, i.p.) and diazepam (1.0 mg/kg, i.p.) did not produce significant change in any of the parameters.
|Table 3: Effects of diazepam (1.0 and 2.0 mg/kg) and 7e (0.5, 1.0, and 2.0 mg/kg) on hole-board test behavior (latency time, number of nose poking, and time of nose poking) in albino mice |
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Open field test
Compound 7e (1.0 and 2.0 mg/kg, i.p.) and diazepam (1.0 and 2.0 mg/kg, i.p.) treatment significantly at P < 0.05 increased the ambulation scores and also increased the rearings as compared to vehicle treatment group whereas the lower dose of 7e (0.5 mg/kg, i.p.) did not produce significant change in any of the parameters [Table 4].
|Table 4: Effects of diazepam (1.0 and 2.0 mg/kg) and 7e (0.5, 1.0, and 2.0 mg/kg) on open field test behavior (ambulation scores and rearings) in albino mice |
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Light and dark aversion test
The results of the L and D test are shown in [Table 5]. Compound 7e (1.0 mg/kg, i.p.) and diazepam (1.0 and 2.0 mg/kg, i.p.) treatment significantly at P < 0.05 increased the number of transitions from one compartment to other, as well as increased the time spent in lit area. Lower dose of 7e (0.5 mg/kg, i.p.) did not produce significant change in any of the parameters [Table 5].
|Table 5: Effects of diazepam (1.0 and 2.0 mg/kg) and 7e (0.5, 1.0, and 2.0 mg/kg) on open field test behavior (squares crossed, number of transitions, and time spent in light area) in albino mice |
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| Discussion|| |
The present investigation shows antidepressant- and anxiolytic-like activity of compound 7e, a novel 5-HT 3 antagonist in rodent models. Blocking of limbic hyperactivity response (antidepressant effect) by 5-HT 3 antagonist was concluded after the animal studies.  The preliminary parameters of 7e were (i) log P = 4.01, which is optimum for blood-brain barrier permeability to show 5-HT 3 antagonist effect (impairment of mood disorder), (ii) pA 2 value 7.3 greater than selective 5-HT 3 receptor antagonist ondansetron (6.9), and (iii) antidepressant-like effect observed in mouse FST and TST encourage the present study based on standardized antidepressant assay. 
Screening antidepressants as well as exploring the underlying mechanism of action is usually achieved by FST behavior despair test which is frequently used as an authentic animal model of depression.  The predictive assays of antidepressant activity as seen in mice FST and TST are observed to give positive results to major class of antidepressants including tricyclics, SSRIs, and serotonin-norepinephrine reuptake inhibitors irrespective of the laboratories where the tests were performed. While studying the antidepressant potential of any novel 5-HT 3 antagonist, the hyper-locomotive activity (HLA) should be unaltered when compared to the HLA of standard drug used. Assessment of antidepressant potential is interfered by possible hyper-locomotive property of a test substance leading to false positive results. 
The dose range (0.5-2.0 mg/kg) of compound 7e selected for mouse FST and TST did not alter SLA. Acute treatment with compound 7e significantly (i) decreased the duration of immobility in the FST and TST and (ii) increased the swimming behavior in FST, reflecting the antidepressant-like effects of molecule. Interaction study of compound 7e with standard antidepressant (Bupropion) was performed to evaluate the probable mechanism of the compound and to find out whether the combination of two gives better effect than standard alone or not. Outcomes of the earlier investigations suggest the involvement of 5-HT 3 receptor in the pathophysiology of depression and anxiety. , Regulation of depression- and anxiety-related behaviors by 5-HT 3A receptors was revealed after performing studies using 5-HT 3A knockout mice.
In the present study, the pargyline (MAO inhibitor) and 5-HTP-induced head twitches response was significantly increased by compound 7e and FLX. The action is mediated by the action of serotonin at 5-HT2 A receptor. The increase in monoamine (5-HT) levels in the synapse leads to antidepressant-like effect of compound 7e.
In the present study, various animal models of anxiety such as EPM, L and D test, HB test, and OFT were used to examine anxiolytic effects of compound 7e. Hypothesis that 5-HT 3 receptor antagonists play a vital role in pathogenesis of anxiety disorder by increasing the availability of serotonin at postsynaptic receptors was designed before initiating the current study and was further confirmed after studying the results. All of the components of the complex expression of anxiety are uncertain to be found in a single animal model. For the same reason, battery of tests were used to evaluate the potential anxiolytic effect of compound 7e in the present study.
In case of EPM, it was found that compound 7e produced anxiolytic-like effect evidenced by increased percentages of both open arm entries and time spent in open arms. In addition, the present study results revealed that compound 7e treatment significantly increased the number of nose pokings and decreased latency of nose pokings in HB test depicting anxiolytic-like behavior. Furthermore, compound 7e treatment increased the ambulation scores in OFT indicating anxiolytic effect of compound 7e. In addition to that, compound 7e administration significantly increased the time spent in lit compartment as well as number of transitions in the L and D test.
Based on the present results, it is suggested that compound 7e, a novel 5-HT 3 receptor antagonist, could be a potential candidate for the management of depression and anxiety. Further studies are warranted to examine the possible mechanism(s) such as the postreceptor action and signal transduction.
We would like to thank the Indian Council of Medical Research, New Delhi, India, BITS, Pilani, India, and Sophisticated Analytical Instrument Facilities, Panjab University, Chandigarh, India, for providing financial support, laboratory and analytical facilities, respectively.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]