The possibility that iNos expression has implications in the pathophysiology of depression is also supported by studies showing that nitric oxide is an important signaling molecule known to modulate norepinephrine, serotonin, dopamine and glutamate, major neurotransmitters implicated in the neurobiology of depression (Dhir and Kulkarni, 2011). The gene discussed is NOS2; the disease is major depressive disorder.