Strychnine alters the fusiform cell output from the dorsal cochlear nucleus

Abstract

Anatomical and physiological evidence suggests that fusiform cells, the major output neurons of the dorsal cochlear nucleus (DCN), receive significant inhibitory input. Fusiform cells often display strongly non-monotonic rate-intensity functions and pauser-buildup or buildup tone-evoked temporal responses, patterns which may be mediated by inhibitory neurotransmitters. Other neurons located within the fusiform cell layer or in the more superficial molecular layer display varied rate-intensity functions and temporal responses. Neurons displaying response properties characteristics of fusiform cells are sensitive to iontophoretic application of the inhibitory amino acid neurotransmitter, glycine. Application of the glycine receptor antagonist, strychnine, alters the non-monotonic portion of the rate-intensity function at doses which do not alter spontaneous activity or near-threshold tone-evoked responses. These neurons are also sensitive to GABA and the GABA B agonist, (−)-baclofen, but are insensitive to the GABA A antagonist, bicuculline. DCN neurons which display monotonic rate-intensity functions and temporal response properties different than those associated with fusiform cells are sensitive to bicuculline, (−)-baclofen, and GABA. These data suggest that a glycinergic input onto fusiform cells may control the non-monotonic nature of the response of these neurons near characteristics frequency and therefore may contribute significantly to the nature of the output of the DCN.