Excitation and inhibition in the dorsal nucleus of the lateral lemniscus influence binaural response properties of neurons in the rat’s inferior colliculus

Abstract

In vitro brain slice studies have shown that neurons in the rat’s dorsal nucleus of the lateral lemniscus (DNLL) are affected by both NMDA and non-NMDA receptor-mediated excitation and glycineric inhibition evoked by electrical stimulation of ascending afferent fibers in the lateral lemniscus and GABAergic inhibition evoked by stimulation of the commissure of Probst [Wu and Kelly, 1996]. The effects of excitatory and inhibitory events in the DNLL on binaural responses in the rat’s inferior colliculus are reported here for in vivo experiments. Receptor specific antagonists were injected locally into the DNLL before and after recording extracellular single-neuron responses from the contralateral inferior colliculus. Binaural responses were evoked by paired clicks delivered to the two ears. Both NMDA and non-NMDA excitatory amino acid antatonists (NBQX and CPP) produced a release from binaural inhibition and glycinergic and GABAergic antagonists (strychnine and bicuculline) resulted in enhanced binaural inhibition. The results support the idea that the DNLL plays a role in binaural processing through an inhibitory (GABAergic) influence on the contralateral central nucleus of the inferior colliculus. [Research supported by NSERC of Canada.]