N-Methyl-D-aspartic Acid (NMDA) in the nervous system of the amphioxus Branchiostoma lanceolatum

<p>Abstract</p> <p>Background</p> <p>NMDA (<it>N</it>-methyl-D-aspartic acid) is a widely known agonist for a class of glutamate receptors, the NMDA type. Synthetic NMDA elicits very strong activity for the induction of hypothalamic factors and hypophyseal hormones in mammals. Moreover, endogenous NMDA has been found in rat, where it has a role in the induction of GnRH (Gonadotropin Releasing Hormone) in the hypothalamus, and of LH (Luteinizing Hormone) and PRL (Prolactin) in the pituitary gland.</p> <p>Results</p> <p>In this study we show evidence for the occurrence of endogenous NMDA in the amphioxus <it>Branchiostoma lanceolatum</it>. A relatively high concentration of NMDA occurs in the nervous system of this species (3.08 ± 0.37 nmol/g tissue in the nerve cord and 10.52 ± 1.41 nmol/g tissue in the cephalic vesicle). As in rat, in amphioxus NMDA is also biosynthesized from D-aspartic acid (D-Asp) by a NMDA synthase (also called D-aspartate methyl transferase).</p> <p>Conclusion</p> <p>Given the simplicity of the amphioxus nervous and endocrine systems compared to mammalian, the discovery of NMDA in this protochordate is important to gain insights into the role of endogenous NMDA in the nervous and endocrine systems of metazoans and particularly in the chordate lineage.</p

-Methyl-D-aspartic Acid (NMDA) in the nervous system of the amphioxus -1

<p><b>Copyright information:</b></p><p>Taken from "-Methyl-D-aspartic Acid (NMDA) in the nervous system of the amphioxus "</p><p>http://www.biomedcentral.com/1471-2202/8/109</p><p>BMC Neuroscience 2007;8():109-109.</p><p>Published online 20 Dec 2007</p><p>PMCID:PMC2241627.</p><p></p>before purification by OPA treatment. The same sample after purification with OPA, which eliminates all the amino acids (or almost all) except NMDA. Note that it is not possible to see the NMDA in this graphic because it does not react with OPA-mercaptoethanol, that is the reagent used for the determination of free amino acids at HPLC. The same sample as B, but after treatment with D-AspO. In this case, the D-AspO oxidizes NMDA producing the CHNHwhich reacts with OPA-mercaptoethanol to give a well-defined sharp peak at the end of the chromatogram at retention time 11.8–12.0 min

Oxidation reaction of NMDA by D-Aspartate oxidase and production of methylamine (CHNH)

<p><b>Copyright information:</b></p><p>Taken from "-Methyl-D-aspartic Acid (NMDA) in the nervous system of the amphioxus "</p><p>http://www.biomedcentral.com/1471-2202/8/109</p><p>BMC Neuroscience 2007;8():109-109.</p><p>Published online 20 Dec 2007</p><p>PMCID:PMC2241627.</p><p></p

D-aspartic acid in the nervous system of Aplysia limacina:possible role in neurotransmission

In the marine mollusk Aplysia limacina, a substantial amount of endogenous D-aspartic acid (D-Asp) was found following its synthesis from L-aspartate by an aspartate racemase. Concentrations of D-Asp between 3.9 and 4.6 μmol/g tissue were found in the cerebral, abdominal, buccal, pleural, and pedal ganglia. In non nervous tissues, D-Asp occurred at a very low concentration compared to the nervous system. Immunohistochemical studies conducted on cultured Aplysia neurons using an anti-D-aspartate antibody demonstrated that D-Asp occurs in the soma, dendrites, and in synaptic varicosities. Synaptosomes and synaptic vesicles from cerebral ganglia were prepared and characterized by electron microscopy. HPLC analysis revealed high concentrations of D-Asp together with L-aspartate and L-glutamate in isolated synaptosomes. In addition, D-Asp was released from synaptosomes by K+ depolarization or by ionomycin. D-Asp was one of the principal amino acids present in synaptic vesicles representing about the 25% of total amino acids present in these cellular organelles. Injection of D-Asp into live animals or addition to the incubation media of cultured neurons, caused an increase in cAMP content. Taken as a whole, these findings suggest a possible role of D-Asp in neurotransmission in the nervous system of Aplysia limacina. © 2005 Wiley-Liss, Inc