Strychnine blocks binaural inhibition in lateral superior olivary neurons

TLDR

Neurons in the lateral superior olivary nucleus receive bilateral inputs and are thought to encode spatial sound localization. The study aims to identify neurotransmitters mediating binaural inhibition in lateral superior olivary nucleus neurons. Iontophoretic glycine mimicked binaural inhibition, which was blocked by the glycine antagonist strychnine but not by the GABA antagonist bicuculline, indicating that glycine mediates binaural inhibition in certain SOC neurons and that the medial nucleus of the trapezoid body projects glycinergic inputs to the LSO.

Abstract

The present study seeks to identify neurotransmitters mediating binaural inhibition in lateral superior olivary nucleus neurons. Neurons in this auditory structure receive inputs from both ears and are thought to code for localization of sound in space. Iontophoretic application of glycine during monaural stimulation was found to mimic the inhibition observed with binaural stimulation. Binaural inhibition was blocked by application of the glycine receptor antagonist, strychnine, as were the effects of iontophoretic application of glycine. The post-strychnine recovery time course for return of synaptically mediated binaural inhibition and recovery of the effects of iontophoretic glycine application were identical. Although the superior olivary complex (SOC) neurons displaying binaural inhibition could in some cases be inhibited by GABA, the binaural inhibition rarely was blocked by iontophoretic application of the GABA receptor antagonist, bicuculline. These findings suggest that glycine may be a neurotransmitter mediating binaural inhibition in certain SOC neurons and that the projection to the lateral superior olivary nucleus from the medial nucleus of the trapezoid body may be glycinergic.