Had to look up several references but was finally able to confirm that nitric oxide synthase inhibitor, when combined with melatonin, measurably improves antidepressant effects in mice. Now the combination of nitric oxide synthase inhibitor and melatonin are being tested prophylactically to help with sleep disturbances that are associated with stroke and to effectively reduce post-stroke depression.
Having known someone who had a stroke at a fairly young age and seeing how he had to struggle with depression, I am especially glad to hear of finding new ways to help with this difficult problem using natural means.