D,L-Homocysteic acid

Although specific neurotoxic effects of D,L-homocysteic acid were observed at doses of 1.6 pmol, L-glutamic acid was ineffective at a dose as high as 3.4 prnol (Schwarcz et ah, 1978 ). The virtual absence of neurotoxic effects of L-glutamic acid in the adult rat striatum (Olney and deGubreff, 1977) may be due to the acute form of administration and the substantial activity of uptake and metabolic processes which rapidly reduce free levels... 

Other neurotransmitters. The abundant glutamate, GABA, and glycine are major neurotransmitters. Do other amino acids also function in the brain Roles for L-aspartate and D-serine (p. 1785) have been identified, but it is very difficult either to discover or to disprove a neurotransmitter function for other amino acids. It is even more difficult for small amounts of various amines and small peptides that are present in the brain. Taurine (Fig. 24-25) is one of the most abundant free amino acids in animals and meets several criteria for consideration as both an inhibitory and an excitatory transmitter.797 798 However, its function is still uncertain (see Chapter 24). Homocysteic acid, formed by oxidation of homocysteine, is a powerful neuroexcitatory substance, but its concentration in the brain is very low.149 d-Aspartate is also present... 

Smolin L A., Crenshaw T D, Kurtycz D, and Benevenga N J (1983) Homocyst(e)ine accumulation in pigs fed diets deficient in vitamin B-6 Relationship to atherosclerosis. / Nutr 113, 2122-2133 Snyderman S E, Holt Jr, L E, Norton P M, Rottman E, and Phanslaker S. V (1968) The plasma aminogram. 1. Influence of the level of protein intake and a comparison of whole protein and amino acid diets Pediat, Res 2, 131-144. 

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