Interaction of catecholamine and amino acid metabolism in brain: effect of pargyline and l-dopa / W. J. Nicklas, S. Berl, and D. D. Clarke Department of Neurology, College of Physicians and Surgeons, Columbia University, 640 West 168th Street, New York, NY 10032 and Department of Chemistry, Fordham University, Bronx, NY 10458, U.S.A.

Abstract

The combination of L-DOPA and pargyline caused a decrease in level of aspartate and an increase in that of glutamine in vivo in cerebral cortex, cerebellum, brain stem, hypothalamus, neostriatum and cervical cord of rat. There was also a decreased incorporation of radioactivity from [1-14C]acetate into amino acids in rico, most notably in cerebellum and brain stem. The labelling of glutamine was especially affected. In addition, cortical slices were prepared from guinea pigs which had been pretreated with pargyline. These slices were incubated with and without 1 mM L-DOPA in media containing [l- 14C]acetate. Pargyline alone caused a stimulation of the labelling of glutamate and aspartate but not glutamine and GABA ; the levels of aspartate and GABA were greater than in control slices. The addition ofL-DOPA to slices from pargylinized animals caused a severe decrease in glutamine labelling but not in that of glutamate or aspartate; the level of glutamine was increased while that of glutamate was decreased. The results are discussed in terms of the known biochemical and morphological compartmentation of amino acids in brain. It is suggested that catecholamines, in the process of functioning as transmitters, may also function as metabolic regulators of other transmitters, e.g. amino acids, as well as of the energy required for balanced neuronal functio