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D ‐aspartic acid in the nervous system of Aplysia limacina : Possible role in neurotransmission
Author(s) -
Spinelli Patrizia,
Brown Euan R.,
Ferrandino Gabriele,
Branno Margherita,
Montarolo Pier Giorgio,
D'Aniello Enrico,
Rastogi Rakesh K.,
D'Aniello Biagio,
Baccari Gabriella Chieffi,
Fisher George,
D'Aniello Antimo
Publication year - 2006
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.20513
Subject(s) - aplysia , synaptic vesicle , ionomycin , nervous system , neurotransmission , biology , synaptosome , glutamate receptor , biochemistry , depolarization , central nervous system , vesicle , neuroscience , biophysics , receptor , in vitro , membrane
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.