Plasticity of excitatory amino acid receptors: Implications for aging and Alzheimer's disease

In view of the critical role of the N-methyl-D-aspartate (NMDA) and other excitatory amino acid (EAA) receptors in higher brain function, it is essential to understand their properties in the developing, mature, aged, injured, and diseased brain. This chapter develops radioligand binding techniques to examine the various receptor components of the EAA system. NMDA receptors have been found to be important in the process of stabilizing appropriate synaptic contacts during development. In the adult brain, no such role has been established, but it is possible that these receptors at least in part play some role in reactive synaptogenesis. The chapter focuses on the hippocampus, in particular the hippocampal alterations that occur following the loss of the major cortical input to the hippocampus, which originates in the entorhinal cortex. The entorhinal cortex is vulnerable in normal aging and in Alzheimer's disease, and lesions of the entorhinal cortex have been widely used as a model system in which to examine synaptic plasticity.