The Postnatal Development of d-Serine in the Retinas of Two Mouse Strains, Including a Mutant Mouse with a Deficiency in d-Amino Acid Oxidase and a Serine Racemase Knockout Mouse

[Image: see text] d-Serine, an N-methyl d-aspartate receptor coagonist, and its regulatory enzymes, d-amino acid oxidase (DAO; degradation) and serine racemase (SR; synthesis), have been implicated in crucial roles of the developing central nervous system, yet the functional position that they play in regulating the availability of d-serine throughout development of the mammalian retina is not well-known. Using capillary electrophoresis and a sensitive method of enantiomeric amino acid separation, we were able to determine total levels of d-serine at specific ages during postnatal development of the mouse retina in two different strains of mice, one of which contained a loss-of-function point mutation for DAO while the other was a SR knockout line. Each mouse line was tested against conspecific wild type (WT) mice for each genetic strain. The universal trend in all WT and transgenic mice was a large amount of total retinal d-serine at postnatal age 2 (P2), followed by a dramatic decrease as the mice matured into adulthood (P70–80). SR knockout mice retinas had 41% less d-serine than WT retinas at P2, and 10 times less as an adult. DAO mutant mice retinas had significantly elevated levels of d-serine when compared to WT retinas at P2 (217%), P4 (223%), P8 (194%), and adulthood (227%).