title: The binaural auditory pathway: excitatory amino acid receptors mediate dual timecourse excitatory postsynaptic currents in the rat medial nucleus of the trapezoid body.
abstract: We show here that synaptic transmission to the medial nucleus of the trapezoid body (MNTB) is mediated principally by excitatory amino acid receptors and has two components. A fast excitatory postsynaptic current (EPSC) is mediated by non-NMDA receptors and a slow EPSC is mediated by NMDA receptors. Each neuron receives a large synaptic input (calyx of Held) which produces an EPSC with a mean peak conductance of 37 nS. The somatic location of this synapse gives good resolution of the EPSC timecourse with the fast EPSC decaying with a time constant of 1.1 ms (at 25 degrees C). The slow EPSC exhibits a double exponential decay with time constants of 41 ms and 106 ms and is voltage dependent in the presence of extracellular magnesium. Other smaller EPSCS mediated by NMDA and non-NMDA receptors, and a strychnine-sensitive synaptic current, are also present. Although the intrinsic membrane properties of MNTB neurons (Forsythe & Barnes-Davies (Proc. R. Soc. Lond. B 251, 143 (1993)), preceding paper) promote high-fidelity transmission, we show that voltage-dependent modulation of synaptic transmission can occur. Given the specialization of the calyx of Held, it seems that the NMDA-receptor ion channel complex is not primarily serving to potentiate a subthreshold input, but may be involved in the development and maintenance of this exuberant somatic synapse.
authors.affiliation: Department of Physiology, University of Leicester, U.K.
authors.forename: I D
authors.initials: ID
authors.lastname: Forsythe
authors.forename: M
authors.initials: M
authors.lastname: Barnes-Davies
mesh_terms: D000818:Animals; D001306:Auditory Pathways / Q000502:physiology*; D004594:Electrophysiology; D066298:In Vitro Techniques; D007700:Kinetics; D009847:Olivary Nucleus / Q000502:physiology*; D051381:Rats; D017459:Receptors, Amino Acid / Q000502:physiology*; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology
chemical_list: D017459:Receptors, Amino Acid; D016194:Receptors, N-Methyl-D-Aspartate