Alzheimer’s disease is one of the most prevalent brain neurodegenerative diseases with severe learning and memory defects that destruction of neurons in areas associated with cognitive functions(1).The hippocampus is made up of three areas: CA1, CA2 and CA3. The evolution of the diseasethe most prominent reduction of neuronal density especially was found in the CA1 and CA3 hippocampal areas(2).Alzheimer’s disease patients damage neurons involved in memory processing in different areas of the brain that seen such as the hippocampus (3). This study investigated the effect of ICV injection of streptozotocin (STZ) in memory retention and CA1 hippocampus neuronal density in male rats.