5-HT3 antagonist 5 is a quinoxalin-2-carboxamide compound that acts as a 5-HT3 receptor antagonist, counteracting 5-HT3 agonist and 2-methyl-5-HT, and demonstrating an anti-depressant effect in mice [1].

Compound 4c, a 5-HT3 antagonist, demonstrates effective antagonism against the 5-HT3 receptor in the longitudinal muscle myenteric plexus of the guinea pig ileum. This activity is observed when challenged with the 5-HT3 agonist, 2-methyl-5-HT, manifesting a pA2 value of 5 [1].

Compound 4c, a 5-HT3 antagonist administered at 1 mg/kg intraperitoneally as a single dose, effectively reduced immobility duration, demonstrating an antidepressant effect in Forced Swim Test (FST) mice [1]. This experiment utilized Swiss albino mice weighing 23 ± 2 g [1]. Despite its significant effect on immobility, compound 4c did not alter the spontaneous locomotor activity in these animals, indicating its specificity in exhibiting the antidepressant effect without affecting general locomotion.