Circadian variations of amino acid content of suprachiasmatic nucleus in rats.

The suprachiasmatic nucleus (SCN) has been known as an oscillator of circadian rhythm and recently some reports suggested that excitatory amino acids were functioning in this nucleus. The purpose of this study is to measure the physiological amino acid content of this nucleus, to estimate the circadian variation in amino acids and the effect of light on amino acid content in the SCN. The content of aspartate, asparagine, glycine and serine tended to be lower in the light phase compared to the dark, but was not significant. As to the light effect on amino acid content of the SCN, only aspartate decreased when a light pulse was applied. These results suggest that aspartate is involved in the transmission of photic information within the SCN.