The objective of this research is to identify chemical markers for specific populations of auditory synopatic terminals in the superior olivary complex, cochlear nucleus and cochlea so that we may map their distribution and location on specific classes of auditory neurons and describe differences in their chemical properties, especially those related to their neurotransmitters. These studies will examine the localization of radiolabeled compounds related to putative neurotransmitter amino acids with light and electron microscopic autoradiography. A fresh brain slice preparation in cats and gerbils and an in vivo cochlear preparation in gerbils will be used. Conditions affecting the accumulation and release of label will be characterized to determine whether the labeled compound may belong to one of the various categories of neurotransmitter related compounds, or to provide evidence of metabolic properties which may be related to transmitters.