The concept that receptive sites on neuronal membranes are the key to specificity in the mediation and modulation of chemical neurotransmission is a widely held tenet of neurobiology. Thus receptive sites on postsynaptic membranes are thought to mediate transmission while additional receptive sites coupled to transport systems are thought to be responsible for the regulation fo extracellular levels of neurotransmitter. In addition, extrajunctional and/or presynaptic receptive sites may play roles in the modulation of chemical transmission. In the past we have identified, characterized, and partially purified three receptive sites for gamm-aminobutryic acid (GABA): the neuronal and glial uptake receptive sites and that postsynaptic receptive sites associated with junctional comples (or postsynaptic densities). We propose to produce monoclonal antibodies directed at the active (that is, ligand-binding) site of these receptive systems and to employ these antibodies in biochemical, immunologic and pharmacologic studies of the GABA synapse. Immunohistochemical studies would allow the location of each receptive species in discrete subcellular regions of neurons or glia). Antibodies and pharmacologic agents would be employed to study their interaction with specific receptive species. Finally, immobolized antibodies would be employed in an attempt to purify GABA receptive species to homogeneity.