Discovery of a Novel Inhibitory Neuron Class, the L-Stellate Cells of the Cochlear Nucleus

Abstract

12Auditory processing depends upon inhibitory signaling by interneurons, even at its earliest stages 13 in the ventral cochlear nucleus (VCN). Remarkably, to date only a single subtype of inhibitory 14 neuron has been documented in the VCN, a projection neuron termed the D-stellate cell. With 15 the use of a transgenic mouse line, optical clearing and imaging techniques, combined with 16 electrophysiological tools, we revealed a population of glycinergic cells in the VCN distinct from 17 the D-stellate cell. These novel multipolar glycinergic cells were smaller in soma size and 18 dendritic area, but over 10-fold more numerous than D-stellate cells. They were activated by 19 auditory nerve fibers and T-stellate cells, and made local inhibitory synaptic contacts on 20 principal cells of the VCN. Given their abundance, combined with their narrow dendritic fields 21 and axonal projections, it is likely that these neurons, here termed L-stellate cells, play a 22 significant role in frequency-specific processing of acoustic signals. 23Axon-dendritic arbors of cell types 132

Nitric oxide regulates the firing rate of neuronal subtypes in the guinea pig ventral cochlear nucleus

“…We divided our cells into a minimum number of classes but bushy cells (Cao et al.,), onset cells (Arnott et al., ) and choppers (Palmer et al., ; Rhode et al., ) can all be subdivided into different subclasses in terms of both their physiological properties and axonal projections. They can also differ in neurotransmitter type: one type of small stellate cell with chopper responses is thought to be glycinergic (Ngodup & Trussell, ) while most choppers are thought to be glutamatergic. The T‐stellate chopper cells of the mouse VCN form a bidirectional, positive feedback network that is dependent on NO (Cao et al.,).…”

“…These are the globular and spherical bushy cells, which show primary‐like peri‐stimulus time histograms (PSTHs; Smith & Rhode, ); small‐ to medium‐sized stellate cells, with chopper PSTHs (Palmer, Wallace, Arnott, & Shackleton, ; Smith & Rhode, ); and large stellate cells and octopus cells (OC) with distinctive onset responses (Arnott, Wallace, Shackleton, & Palmer, ; Oertel, Wu, Garb, & Dizack, ; Rhode, Oertel, & Smith, ). The afferent inputs from the auditory nerve and the majority of VCN neurones with intrinsic branches are excitatory, while the large stellate onset cells and some small chopping stellates are glycinergic (Doucet, Ross, Gillespie, & Ryugo, ; Ngodup & Trussell, ). All of these intrinsic neurones can contain nNOS, but within each class there are large variations in the quantity of enzyme present (Coomber et al., ).…”

Nitric Oxide-Mediated Plasticity of Interconnections Between T-Stellate cells of the Ventral Cochlear Nucleus Generate Positive Feedback and Constitute a Central Gain Control in the Auditory System

“…Synaptic terminals in the multipolar cell area appear as immunolabeled puncta, although puncta can also reflect cross sections of dendrites and axons. Terminals arise from auditory nerve fibers (Doucet and Ryugo, 1997;Cao et al, 2008), local collateral terminals of T-and D-stellate cells Doucet and Ryugo, 1997), newly discovered small glycinergic cells (Ngodup and Trussell, 2019), tuberculoventral cells (Zhang and Oertel, 1993), somatosensory afferents (Zeng et al, 2012), and possibly from unidentified excitatory neurons. NO-GC-positive puncta appose both large and small cells ( Fig.…”