5-HT3 antagonists showed an antidepressant effect in the mouse FST and TST.
nNOS inhibitor enhanced the effect of 5-HT3 antagonists in behavioral tests.
NO precursor and 5-PDE inhibitor attenuated the effect of 5-HT3 antagonists.
5-HT3 antagonists and nNOS inhibitor decreased the hippocampal nitrite levels.
Antidepressant effect of 5-HT3 antagonists is partly mediated via NO-cGMP pathway.