Antidepressant & anxiolytic activities of N-(pyridin-3-yl) quinoxalin-2-carboxamide: A novel serotonin type 3 receptor antagonist in behavioural animal models.

BACKGROUND & OBJECTIVES: Alteration in the serotonin leads to the psychological illness, such as depression, anxiety, schizophrenia, eating disorders, obsessive-compulsive disorder, panic disorders and migraines. The objective of the current study was to investigate the antidepressant and anxiolytic activities of N-(pyridin-3-yl) quinoxalin-2-carboxamide (QCF-21), a novel 5-HT3receptor antagonist in preclinical models of depression and anxiety. METHODS: Antidepressant activity was evaluated in preliminary tests such as forced swim and tail suspension tests (FST & TST). Anti-anxiety effect of QCF-21 was investigated by employing elevated plus maze (EPM), light/dark and hole board tests. Olfactory bulbectomy (OBX) in rats was used as chronic model of depression. Mechanistic test of QCF-21 was evaluated by reserpine-induced hypothermia and 5-hydroxytryptophan (5-HTP)-induced head-twitch response. RESULTS: The dose-response study revealed an initial antidepressant-like effect of QCF-21(0.25-1 mg/kg, i.p.) in the FST and TST and anxiolytic-like effect in EPM, light and dark and hole board tests. QCF-21 potentiated the 5-HTP-induced head-twitches response in mice and reversed reserpine-induced hypothermia in rats. QCF-21 significantly reversed the behavioural anomalies post-OBX in rats. INTERPRETATION & CONCLUSIONS: The present findings indicate the potential antidepressant-like and anxiolytic-like effects of QCF-21 at low doses in rodent behavioural models of depression and anxiety. Further studies need to be done to understand the underlying mechanism.

Antidepressant-like activity of (4-phenylpiperazin-1-yl) (quinoxalin-2-yl) methanone (4a), a novel 5-HT(3) receptor antagonist: an investigation in behaviour-based rodent models of depression.

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.

Antidepressant and anxiolytic-like effects of 4n, a novel 5-HT3 receptor antagonist using behaviour based rodent models.

The present study was designed to investigate the putative antidepressant and anxiolytic-like effects of N-n-Butylquinoxalin-2-carboxamide (4n), a novel 5-HT3 receptor antagonist, with an optimal log P (2.01) and pA2 value (7.3) greater than ondansetron (6.9) using rodent behavioural models of depression and anxiety. Acute treatment of 4n (1-4 mg/kg, ip) in mice produced antidepressant-like effect in forced swim test (FST) without affecting the baseline locomotion in actophotometer test in mice. 4n (2-4 mg/kg, ip) treatment also potentiated the 5-hydroxytryptophan (5-HTP) induced head twitch response in mice. Further, 4n (1-4 mg/kg, ip) treatment antagonized reserpine induced hypothermia in rats. Chronic treatment (14 days) with 4n (1-4 mg/kg) and paroxetine (10 mg/kg) significantly attenuated the behavioural anomalies induced by bilateral olfactory bulbectomy in rats in modified open field paradigm. An anxiogenic-like behaviour was induced by light alone as the stimulus using light-dark aversion test. 4n (2-4 mg/kg, ip) treatment significantly increased no. of transitions between dark and lit area and the time spent in the lit area. In conclusion, these preliminary investigations confirm that 4n exhibited antidepressant and anxiolytic-like effects in rodent models of depression and anxiety.

Ligand-based design, synthesis, and pharmacological evaluation of 3-Methoxyquinoxalin-2-carboxamides as structurally novel serotonin type-3 receptor antagonists.

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).

Discovery of new anti-depressants from structurally novel 5-HT3 receptor antagonists: design, synthesis and pharmacological evaluation of 3-ethoxyquinoxalin-2-carboxamides.

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.

Quinoxalin-2-carboxamides: synthesis and pharmacological evaluation as serotonin type-3 (5-HT3) receptor antagonists.

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.

Design, synthesis and structure-activity relationship of novel quinoxalin-2-carboxamides as 5-HT3 receptor antagonists for the management 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.

Effect of anti-depressants on neuro-behavioural consequences following impact accelerated traumatic brain injury in rats.

Disruption of normal neuronal networks and neurotransmitters like serotonin and norepinephrine levels in post traumatic brain injury (TBI) are observed to be the primary causative agent for depression/anxiety. This communication reports the efficacy of various classes' anti-depressants in the treatment of depression/anxiety following TBI in rats. Chronic treatment with anti-depressants (escitalopram and venlafaxine) leads to improvement in the depressive/anxiogenic-like behaviour in the TBI rat and corroborates the notion of the involvement of serotonin and norepinephrine in the behavioural consequences of post-TBI. Chronic treatments with escitalopram and venlafaxine significantly reversed the effect of TBI as compared to vehicle-treated TBI group. The results showed a quantitative battery of neuro-behavioural functional assessments that correlates with neuronal damage following traumatic brain injury.

A novel 5-HT(2A) receptor antagonist exhibits antidepressant-like effects in a battery of rodent behavioural assays: approaching early-onset antidepressants.

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.

Depression-like and anxiety-like behavioural aftermaths of impact accelerated traumatic brain injury in rats: a model of comorbid depression and anxiety?

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 induces depressogenic-like behaviour in rodents by stimulating the neuronal 5-HT(2A) receptors: proposal of a modified rodent antidepressant assay.

1-(m-Chlorophenyl)piperazine (mCPP) has a fairly complex neuropsychopharmacological profile owing to its affinity to multiple serotonergic receptors. This investigation was designed to establish the effect of mCPP on rodent depression-like behaviour. mCPP 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). mCPP (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 mCPP (1-2 mg/kg) treatment as observed from the modified open field, elevated plus maze and social interaction paradigms. Interaction studies revealed that the mCPP 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 mCPP. Finally, the mCPP induced depression-like behaviour in rodents is envisaged as a modified antidepressant assay to identify novel serotonergic antidepressants.

Depressant-like effects of parthenolide in a rodent behavioural antidepressant test battery.

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-hydroxytryptophan-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.