title: Glycinergic inhibition to the medial nucleus of the trapezoid body shows prominent facilitation and can sustain high levels of ongoing activity.
abstract: Neurons in the medial nucleus of the trapezoid body (MNTB) are well known for their prominent excitatory inputs, mediated by the calyx of Held. Less attention has been paid to the prominent inhibitory inputs that MNTB neurons also receive. Because of their auditory nature, both excitatory and inhibitory synapses are highly active in vivo. These high levels of activity are known to reduce excitatory synaptic currents considerably, such that in vivo synaptic currents produced by the calyx are smaller than typically measured in standard brain slice experiments. The goal of this study was to investigate the properties of the inhibitory inputs in the Mongolian gerbil (Meriones unguiculatus) under activity levels that correspond to those in the intact brain to facilitate a direct comparison between the two inputs. Our results suggest that inhibitory inputs to MNTB are largely mediated by a fast and phasic glycinergic component, and to a lesser degree by a GABAergic component. The glycinergic component can sustain prolonged high levels of activity. Even when challenged with stimulus patterns consisting of thousands of stimuli over tens of minutes, glycinergic inputs to MNTB maintain large conductances and fast decays and even facilitate substantially when the stimulation frequency is increased. The inhibition is mediated by a relatively small number of independent input fibers. The data presented here suggest that inhibitory inputs to MNTB sustain high levels of activity and need to be considered for a full understanding of mechanisms underlying processing of auditory information in MNTB.
authors.affiliation: Department of Physiology and Biophysics, University of Colorado School of Medicine, Aurora, Colorado.
authors.forename: Florian
authors.initials: F
authors.lastname: Mayer
authors.affiliation: Department of Physiology and Biophysics, University of Colorado School of Medicine, Aurora, Colorado.
authors.forename: Otto
authors.initials: O
authors.lastname: Albrecht
authors.affiliation: Department of Physiology and Biophysics, University of Colorado School of Medicine, Aurora, Colorado.
authors.forename: Anna
authors.initials: A
authors.lastname: Dondzillo
authors.affiliation: Department of Physiology and Biophysics, University of Colorado School of Medicine, Aurora, Colorado achim.klug@ucdenver.edu.
authors.forename: Achim
authors.initials: A
authors.lastname: Klug
mesh_terms: D000818:Animals; D001306:Auditory Pathways / Q000166:cytology / Q000502:physiology; D019706:Excitatory Postsynaptic Potentials; D005260:Female; D005849:Gerbillinae; D005998:Glycine / Q000494:pharmacology*; D053444:Inhibitory Postsynaptic Potentials; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D065833:Trapezoid Body / Q000166:cytology / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
chemical_list: D005680:gamma-Aminobutyric Acid; D005998:Glycine
keywords: auditory brain stem; calyx of Held; inhibition; medial nucleus of the trapezoid body; short-term plasticity