Molecular cloning has identified eight metabotropic glutamate receptor (mGluR) subtypes, each with distinct patterns of expression. However, the characteristic roles of these different mGluRs in physiological processes are not well understood. Identification of subtype-specific compounds may potentially act as therapeutic agents for the treatment of a wide range of conditions (including progressive brain disease, epilepsy and cerebral ischemia) all of which are associated with abnormal mGLuR activation. Zhang and Brownell (Chapter 22) present a superb overview of mGluR functions, radiotracer development and imaging findings to date, and raise important clinical implications and recommendations for further research
