The long-range goals of this project are to study the release and metabolism at selected neural sites of amino acids that may serve as neurotransmitter compounds. The demonstration of a synaptic release of glutamate or aspertate is made more difficult in light of our observations of an impulse-enhanced efflux of these two amino acids from non-synaptic regions of conducting nerve trunks. Our efforts will be directed at understanding the functional relationship between the non- synaptic release of glutamate and aspartate, and the possible synaptic release of these and other transmitter compounds. The metabolic compartmentation of putative transmitter amino acids will be examined in discrete regions of spinal cord where these compounds (glutamate, aspartate, glycine) have been proposed to function as transmitters. Axoplasmic transport of these same amino acids and of enzymes involved in their metabolism will also be studied in spinal neurons. By these approaches, mechanisms may be determined by which a common intermediate metabolite may also function in the highly specific manner required of a neurotransmitter. Bibliographic references: Dravid, A.R. and Hammerschlag, R. (1975). Axoplasmic transport of proteins in vitro in primary afferent neurons of frog spinal cord: effect of Ca 2 ion-free incubation conditions. J. Neurochem. 24, 711-718; Hammerschlag, R., Dravid, A. R. and Chiu, A. (1975). Mechanism of axonal transport: a proposed role for calcium ions. Science 188, 273-275.