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The compound 6o (at 0.5, 1 and 2 mg/kg, ip) with optimum log P and pA2 value, was subjected to forced swim test (FST) and tail suspension test (TST). The compound 6o significantly reduced the duration of immobility in mice without affecting the base line locomotion in actophotometer. Moreover, 6o (2 mg/kg, ip), potentiated the 5-hydroxytryptophan (5-HTP)-induced head twitch responses in mice and at 1 and 2 mg/kg, ip antagonized the reserpine-induced hypothermia (RIH) in rats. In interaction studies with various standard drugs/ligands using FST, 6o (1 and 2 mg/kg, ip) potentiated the anti-depressant effect fluoxetine (5 mg/kg, ip) and reversed the depressant effect of parthenolide (1 mg/kg, ip) by reducing the duration of immobility. Furthermore, 6o (1 and 2 mg/kg, ip) potentiated the effect of bupropion (10 mg/kg, ip) in TST. The behavioural anomalies of the olfactory bulbectomised (OBX) rats were augmented by chronic 6o (1 and 2 mg/kg) treatment as observed from the modified open field test (parameters: ambulation, rearing, fecal pellet). The results suggest that compound 6o exhibited anti-depressant like effect in rodent models of depression.

The present research was designed to explore the anxiolytic-like activity of a novel 5-HT3 receptor antagonist (60) in experimental mouse models of anxiety. The anxiolytic activity of '6o' at (1 and 2 mg/kg, ip) was evaluated in mice by using a battery of behavioural tests of anxiety such as elevated plus maze (EPM), light/dark aversion test, hole board (HB) and open field test (OFT) with diazepam (2 mg/kg, ip) as a standard anxiolytic. None of the tested doses of '6o' affected the base line locomotion. Compound '6o' (2 mg/kg, ip) and diazepam (2 mg/kg, ip) significantly increased the percentage of both time spent and open arm entries in the EPM test. Compound '6o' in (1 mg/kg, ip) dose was only able to affect the percentage time spent in open arm significantly in the EPM test. In the light and dark test, compound '6o' (2 mg/kg, ip) and diazepam (2 mg/kg, ip) significantly increased the total time spent in light compartment as well as number of transitions from one compartment to other and number of square crossed. Compound '6o' (1 and 2 mg/kg, ip) and diazepam (2 mg/kg, ip) also significantly increased number of head dips and number of squares crossed, whereas significantly decreased the head dipping latency in HB test as compared to vehicle control group. In addition, '6o' in both the doses and diazepam (2 mg/kg, ip) significantly increased the ambulation scores (squares crossed) in OFT however, there was no significant effect of '6o' (1 and 2 mg/kg, ip) and diazepam (2 mg/kg, ip) on rearing scores. To conclude compound '6o' exhibited an anxiolytic-like effect in animal models of anxiety.

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.

N-Cyclohexyl-3-methoxyquinoxalin-2-carboxamide (QCM-13), a novel 5-HT3 antagonist identified from a series of compounds with higher pA2 (7.6) and good log P (2.91) value was screened in rodent models of depression such as forced swim test (FST), tail suspension test (TST), interaction studies with standard anti-depressants and confirmatory studies such as reversal of parthenolide induced depression and reserpine induced hypothermia. In FST (2 and 4 mg/kg) and TST (2 and 4 mg/kg), QCM-13 significantly reduced the duration of immobility in mice without affecting the base line locomotion. QCM-13 (2 and 4 mg/kg) was also found to have significant interaction with standard anti-depressants (fluoxetine and bupropion in FST and TST respectively). Further, reversal of parthenolide induced depression in mice and reserpine induced hypothermia in rat models indicate the serotonergic influence of QCM-13 for anti-depressant potential.

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.