AIM During the inflammatory processes in CNS,activated microglia can be induced by many factors.Activation of microglia induces the release of some neurotoxic substances such as nitric oxide (NO),which could induce neuronal death directly or indirectly.The present study evaluated the effects of curcumin,demethoxycurcumin and bidemethoxycurcumin,fractions extracted from Chinese medicinal herbs,on the NO production in LPS-activated rat primary microglial cells.METHODS The effects on the NO production in LPS-activated primary microglial cells were assessed by Griess reaction.RESULTS curcumin,demethyoxycurcumin and bidemethyoxycurcumin significantly inhibited the production of NO in LPS-activated primary microglial cells at doses that did not affect the cell proliferation.Meanwhile,all the compounds had neither NO production influencing nor NO scavenging effect in primary microglial cells.CONCLUSION It was suggested that these compounds could inhibit the activation of microglia.