Free L-amino acids and D-aspartate content in the nervous system of Cephalopoda. A comparative study

We have determined the content of free L-amino acids and D-aspartate in the nervous tissue of three representative cephalopods: Sepia officinalis, Octopus vulgaris, and Loligo vulgaris, and the optic lobes of adult and embryo Sepia ofJicinalis. Taurine is the most abundant amino acid in the cephalopod nervous tissue. Its content amounts to more than 50% of the total free amino acids. The other most concentrated amino acids are Glu, Ala, Asp, and GABA. High concentrations of D-aspartate were found in the nervous tissue of all cephalopods examined (7-12 mu mol/g wet tissue) which represents 50-80% of the total aspartate (D + L), depending on the animal. Among the various regions of the brain of Octopus vulgaris, D-aspartate was found to be evenly distributed in the various regions of the brain. In nerve tissue of Sepia officinalis, there is no significant difference in the pattern of free L-amino acids, in particular of the D-aspartate concentration, between adults and embryos, except for GABA, Gly, His and Thr. This suggests that D-aspartate in nerve tissue of the Cephalopoda is of endogenous origin and not a product of accumulation from exogenous sources. From a comparative study of the content of D-aspartate in the nervous tissue of different animals, we found that protostomia contain a significantly higher amount than deuterostomia. Thus, D-aspartate could be a criterion to distinguish the protostomia phyla from the deuterostomia phyla.