The well-documented co-existence of nNOS-containing neurons and serotonin in hippocampus, medial septum and amygdala, which are brain areas rich of 5-HT1A receptors and critically involved in anxiety (Bredt et al. 1991; Dawson et al. 1991) along with the ability of NO donors to modulate serotonin release from the above cited areas might be a support of this hypothesis (Prast and Philippu 2001). The gene discussed is HTR1A; the disease is Anxiety.