Glutamate receptors underlying excitatory synaptic transmission in the rat's lateral superior olive studied in vitro.
Glutamate receptors underlying synaptic excitation in the rat's lateral superior olive were studied by whole-cell patch clamp recordings in a brain slice preparation. Recordings from two morphological types of cells, bipolar and multipolar, identified by intracellular labeling with biocytin, showed that there were no obvious differences in responses mediated or modulated by ionotropic and metabotropic receptors between these two types of neurons. The excitatory postsynaptic potentials (EPSPs) elicited by ipsilateral stimulation of the trapezoid body consisted of two components. An earlier component, which had faster rise time constant and decay time constant, was mediated by non-NMDA receptors. A later component, which had slower rise time and decay time constants, was mediated by NMDA receptors. Suprathreshold responses (action potentials), which arose from the early component, were always abolished by the non-NMDA antagonist, CNQX, but not by the NMDA antagonist, APV. These results suggest that both non-NMDA and NMDA receptors are present in LSO neurons, and that fast excitatory transmission in LSO is primarily mediated by non-NMDA receptors. The metabotropic glutamate receptor agonists, t-ACPD and L-AP4, reduced the size of EPSPs evoked by stimulation of the ipsilateral trapezoid body in LSO neurons; the reductive action of t-ACPD was reversed by the antagonist, MCPG, indicating that metabotropic glutamate receptors, probably group II and III subtypes, can modulate excitatory synaptic transmission in LSO.
Laboratory of Sensory Neuroscience, Institute of Neuroscience, Carleton University, Ottawa, Ontario, Canada. shwu@ccs.carleton.ca
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D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000613:Aminobutyrates / Q000494:pharmacology; D000818:Animals; D003515:Cycloleucine / Q000031:analogs & derivatives / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D066298:In Vitro Techniques; D018696:Neuroprotective Agents / Q000494:pharmacology; D009847:Olivary Nucleus / Q000187:drug effects* / Q000502:physiology; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D018094:Receptors, Metabotropic Glutamate / Q000187:drug effects* / Q000502:physiology; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects* / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects* / Q000502:physiology
D000613:Aminobutyrates; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D018696:Neuroprotective Agents; D018094:Receptors, Metabotropic Glutamate; D016194:Receptors, N-Methyl-D-Aspartate; D003515:Cycloleucine; C036361:1-amino-1,3-dicarboxycyclopentane; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; C012729:2-amino-4-phosphonobutyric acid