The dual personality of NO

In the body, nitric oxide (NO) is an important physiological regulator of f unctions such as vasodilatation and neurotransmission. Under pathological c onditions, high concentrations of NO can either be beneficial (e.g. antibac terial, anti-parasitic and anti-viral) or detrimental; NO can therefore be considered a double-edged sword. When manipulating NO levels clinically, at tention should be paid to minimize the negative effects and maximize the be neficial effects of NO. This article highlights recent evidence that suppor ts the complexity of the regulatory mechanisms that lead to sophisticated e ndogenous NO production.