In order to provide a novel nitric oxide generation regulator for effectively regulating nitric oxide generation from vascular endothelial cells, macrophage cells including microglial cells, and the like that can be safely used in vivo, disclosed is a nitric oxide generation regulator that has the trinuclear pentamethine cyanine dye represented by the belowmentioned general formula (1) as the active ingredient. (In the general formula (1), R represents a potentially branched alkyl group having 2-4 carbon atoms, and X- represents an appropriate counteranion.)本發明課題為提供一種新的一氧化氮生成調節劑，可安全地適用於生物體，並且用於有效地調節來自於包含小神經膠質細胞的巨噬系細胞或血管內皮細胞等的一氧化氮生成，課題之解決係藉由提供一種一氧化氮生成調節劑，其有效成分為下述一般式1所表示之三核型五甲炔系花青色素，【化1】一般式1(一般式1之中，R表示可具有分支而碳數為2至4之烷基，X-表示適當的相對陰離子)。
