ABSTRACT
A number of acidic amino acids structurally related to l-glutamate have since been shown to exert stimulatory effects comparable to or even more potent than those induced by l-glutamate and l-aspartate. This group of substances, classified as excitatory amino acids (EAAs), includes both endogenous compounds, substances isolated from natural sources, and synthetic compounds. The stimulatory action of EAAs is exerted via an interaction with specific receptors in neuronal membranes. Although the N-Methyl-D-aspartate (NMDA) receptor has been characterized extensively in neuropharmacological experiments, it has proven difficult to develop a high-affinity NMDA selective radioligand for receptor binding studies. Few years ago the autoradiographic receptor binding technique was introduced for studies of the different EAA receptor subtypes in the brain. This technique offered the possibility of studying the regional distribution of each receptor subtype with a resolution at the cellular level. Specific receptor binding assays for the different EAA receptor subtypes are important tools as screening models for the development of new antagonists.
