A cationic dye with diverse biological activities; inhibits the catalytic function of inducible and constitutive nitric oxide synthases; inhibits MAO and increases the activity of mitochondrial cytochrome C oxidase; stabilizes systemic circulation without increasing peripheral resistance, decreases lipid peroxidation, and reduces anoxic tissue injury in brain and heart in a porcine model of global ischemia and reperfusion injury; inhibits MAO activity in brain and reduces the age-related decline in grip strength and spatial memory in old mice at 250 μM in drinking water; reduces immobility time in the forced swim test in mice at 15,30, and 60 mg/kg; commonly used to stain cells and tissues in research