Characterization of sodium-independent β-alanine binding to cerebral cortical membranes from 7-day-old and adult mice

The sodium-independent binding of β-alanine to cerebral cortical membranes from adult (3- and 12-month-old) and developing (7-day-old) mice was characterized for the first time. The binding was saturable in each age group, consisting of only one component. The affinity for β-alanine was highest and the number of available binding sites greatest in young animals. The binding was not affected by strychnine, but inhibited by β-alanine itself, glycine, l-alanine and l-serine, the IC₅₀ values being lower in immature mice. Glycine was shown to be a competitive inhibitor. The binding was also inhibited, albeit only in adults, by N-methyl-d-aspartate receptor antagonists acting at the glycine modulatory site and by some GABAergic substances. It is concluded that even though β-alanine may possess binding sites of its own, particularly in the immature cerebral cortex, β-alanine could at least partly bind to strychnine-insensitive glycine sites in the N-methyl-d-aspartate receptor complex.