Deposits of amyloid beta peptides (A beta) is thought to cause progressive cognitive loss and involve to Alzheimer's disease in humans. Intracerebral or intracerebroventricular injections or infusions of A beta peptides are Commonly used to design animal models that imitate Alzheimer's disease (AD) with cognitive impairment and neurodegenerative disorders. It has been demonstrated that inflammatory responses develop after administration of A beta in vitro and in vivo. A beta and activated microglia stimulates cytokines and nitric oxide (NO). NO can also be neurotoxic primarily to its free radical properties and it has been implicated in neurodegenerative diseases. And also, there are conradictory results about the alterations of NO and nitric oxide synthase system in AD brain.