title: Characterization of spontaneous excitatory synaptic currents in newt retinal bipolar cells.
abstract: The kinetics of glutamate concentration in the synaptic cleft is an important determinant of synaptic function. To elucidate peak concentration of glutamate released from a single vesicle in the cleft, spontaneous excitatory postsynaptic currents (sEPSCs) in Off-bipolar cells from the sliced newt retina were analyzed using whole-cell patch clamp recording and the computer simulation. The sEPSCs were blocked by an AMPA/kainate (KA) antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), and prolonged by cyclothiazide. However, an N-methyl-D-aspartate (NMDA) antagonist, D-2-amino-5-phosphonopentanoic acid (D-AP5), was ineffective. These suggest that sEPSCs in Off-bipolar cells are mediated exclusively by AMPA/KA receptors. sEPSCs simulated by a detailed kinetic model of AMPA receptor best approximated the data, when peak glutamate concentration was 10 microM. Therefore, it was concluded that peak concentration of glutamate released from a single vesicle would be elevated to approximately 10 microM at the newt Off-bipolar dendrite.
authors.affiliation: Department of Information Physiology, National Institute for Physiological Sciences, Okazaki, Japan. fusao@retina.anatomy.upenn.edu
authors.forename: F
authors.initials: F
authors.lastname: Kawai
mesh_terms: D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D001581:Benzothiadiazines / Q000494:pharmacology; D003198:Computer Simulation; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000502:physiology; D066298:In Vitro Techniques; D008959:Models, Neurological; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D018091:Receptors, AMPA / Q000502:physiology; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology; D012160:Retina / Q000166:cytology* / Q000502:physiology*; D012455:Salamandridae; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*
chemical_list: D001581:Benzothiadiazines; D018691:Excitatory Amino Acid Antagonists; D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D015763:2-Amino-5-phosphonovalerate; C004639:cyclothiazide