title: Physiological evidence that D-aspartate activates a current distinct from ionotropic glutamate receptor currents in Aplysia californica neurons.
abstract: D-Aspartate (D-Asp) activates an excitatory current in neurons of Aplysia californica. Although D-Asp is presumed to activate a subset of L-glutamate (L-Glu) channels, the identities of putative d-Asp receptors and channels are unclear. Whole cell voltage- and current-clamp studies using primary cultures of Aplysia buccal S cluster (BSC) neurons were executed to characterize D-Asp-activated ion channels. Both D-Asp and L-Glu evoked currents with similar current-voltage relationships, amplitudes, and relatively slow time courses of activation and inactivation when agonists were pressure applied. D-Asp-induced currents, however, were faster and desensitized longer, requiring 40 s to return to full amplitude. Of cells exposed to both agonists, 25% had D-Asp- but not L-Glu-induced currents, suggesting a receptor for D-Asp that was independent of l-Glu receptors. D-Asp channels were permeable to Na(+) and K(+), but not Ca²⁺, and were vulnerable to voltage-dependent Mg²⁺ block similarly to vertebrate NMDA receptor (NMDAR) channels. d-Asp may activate both NMDARs and non-l-Glu receptors in the nervous system of Aplysia.
authors.affiliation: Division of Marine Biology and Fisheries, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida, USA.
authors.forename: Stephen L
authors.initials: SL
authors.lastname: Carlson
authors.forename: Lynne A
authors.initials: LA
authors.lastname: Fieber
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001048:Aplysia; D001224:Aspartic Acid / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology; D002412:Cations / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D018846:Excitatory Amino Acids / Q000494:pharmacology*; D017952:Ganglia, Invertebrate / Q000166:cytology; D018698:Glutamic Acid / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D007473:Ion Channels / Q000145:classification / Q000187:drug effects* / Q000502:physiology; D008274:Magnesium / Q000494:pharmacology; D008536:Meglumine / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D058468:Receptors, Ionotropic Glutamate / Q000502:physiology; D012964:Sodium / Q000378:metabolism; D013237:Stereoisomerism
chemical_list: D002412:Cations; D018846:Excitatory Amino Acids; D007473:Ion Channels; D058468:Receptors, Ionotropic Glutamate; D001224:Aspartic Acid; D018698:Glutamic Acid; D008536:Meglumine; D012964:Sodium; D008274:Magnesium; D011188:Potassium; D002118:Calcium