Neurons pass signals to each other through highly specialized junctions called synapses, where the axon of the sending neuron passes a signal to a dendrite on the receiving neuron. Dendrites are normally highly branched like a tree, so that they can form many synapses with other neurons. In individuals with Alzheimer's Disease, neurons lose dendrites and synapses. These changes likely underlie the memory loss observed in these patients. The Rho protein is a molecular switch that when turned on in neurons causes a loss of dendrites. Our laboratory has identified a biochemical pathway that turns off Rho and protects neurons from dendrite loss. Our studies have suggested that drugs that inhibit Rho may prevent dendrite and synapse loss in Alzheimer's Disease. We will test whether Rho kinase inhibitors can prevent dendrite loss in mouse models of Alzheimer's Disease. Our longer-term goal is to determine whether inhibition of Rho signaling can prevent dendrite loss in individuals with Alzheimer's Disease.