title: D-aspartic acid in the nervous system of Aplysia limacina: possible role in neurotransmission.
abstract: 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 micromol/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.
authors.affiliation: Laboratory of Neurobiology, Stazione Zoologica A. Dohrn, Villa Comunale, Napoli, Italy.
authors.forename: Patrizia
authors.initials: P
authors.lastname: Spinelli
authors.forename: Euan R
authors.initials: ER
authors.lastname: Brown
authors.forename: Gabriele
authors.initials: G
authors.lastname: Ferrandino
authors.forename: Margherita
authors.initials: M
authors.lastname: Branno
authors.forename: Pier Giorgio
authors.initials: PG
authors.lastname: Montarolo
authors.forename: Enrico
authors.initials: E
authors.lastname: D'Aniello
authors.forename: Rakesh K
authors.initials: RK
authors.lastname: Rastogi
authors.forename: Biagio
authors.initials: B
authors.lastname: D'Aniello
authors.forename: Gabriella Chieffi
authors.initials: GC
authors.lastname: Baccari
authors.forename: George
authors.initials: G
authors.lastname: Fisher
authors.forename: Antimo
authors.initials: A
authors.lastname: D'Aniello
mesh_terms: D000818:Animals; D001048:Aplysia / Q000378:metabolism* / Q000502:physiology; D002467:Cell Nucleus / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D026603:D-Aspartic Acid / Q000378:metabolism*; D007150:Immunohistochemistry; D015759:Ionomycin / Q000494:pharmacology; D008854:Microscopy, Electron; D008954:Models, Biological; D009420:Nervous System / Q000201:enzymology / Q000378:metabolism*; D009490:Neurosecretory Systems / Q000502:physiology; D011188:Potassium / Q000494:pharmacology; D019998:Racemases and Epimerases / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D026603:D-Aspartic Acid; D015759:Ionomycin; D000242:Cyclic AMP; D019998:Racemases and Epimerases; D011188:Potassium