Laminar and Neurochemical Organization of the Dorsal Cochlear Nucleus of the Human, Monkey, Cat, and Rodents

Abstract

The dorsal cochlear nucleus (DCN) is a brainstem structure that receives input from the auditory nerve. Many studies in a diversity of species have shown that the DCN has a laminar organization and identifiable neuron types with predictable synaptic relations to each other. In contrast, studies on the human DCN have found a less distinct laminar organization and fewer cell types, although there has been disagreement among studies in how to characterize laminar organization and which of the cell types identified in other animals are also present in humans. We have reexamined DCN organization in the human using immunohistochemistry to analyze the expression of several proteins that have been useful in delineating the neurochemical organization of other brainstem structures in humans: nonphosphorylated neurofilament protein (NPNFP), nitric oxide synthase (nNOS), and three calcium-binding proteins. The results for humans suggest a laminar organization with only two layers, and the presence of large projection neurons that are enriched in NPNFP. We did not observe evidence in humans of the inhibitory interneurons that have been described in the cat and rodent DCN. To compare humans and other animals directly we used immunohistochemistry to examine the DCN in the macaque monkey, the cat, and three rodents. We found similarities between macaque monkey and human in the expression of NPNFP and nNOS, and unexpected differences among species in the patterns of expression of the calcium-binding proteins.

Volumes of cochlear nucleus regions in rodents

“…Results so far from anatomical studies of the human cochlear nucleus are consistent with this possibility for the VCN, where even some of the same neuron types have been reported (Dublin, 1976; Moore and Osen, 1979; Adams, 1986; Wagoner and Kulesza, 2009), but results for the DCN for humans and other primates have been more controversial (Dublin, 1976; Moore and Osen, 1979; Moore, 1980; Heiman-Patterson and Strominger, 1985; Adams, 1986; Rubio et al, 2008; Wagoner and Kulesza, 2009; Baizer et al, 2012, 2014). This might be consistent with our observation that, when we did occasionally find significant differences among rodents in cochlear nucleus structure, as for pocket gopher and especially mountain beaver, these differences tended to be in the DCN and granular region.…”

The emerging framework of mammalian auditory hindbrain development

“…The human DCN shows a laminar organization with only two layers instead of the typical three found in most mammals (Baizer et al 2014). Furthermore, two cell types were described based on location, morphology and immunoreactivity against non-phosphorylated neurofilament protein and neuronal nitric oxide synthetase, which lack counterparts in non-primates (Baizer et al 2014). Within the SOC, the human MSO appears as a very prominent nucleus, while the LSO is rather small (Kulesza 2007;Moore 1987;Strominger and Hurwitz 1976).…”

“…Differences have only been reported in fine structure. The human DCN shows a laminar organization with only two layers instead of the typical three found in most mammals (Baizer et al 2014). Furthermore, two cell types were described based on location, morphology and immunoreactivity against non-phosphorylated neurofilament protein and neuronal nitric oxide synthetase, which lack counterparts in non-primates (Baizer et al 2014).…”

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

“…The endothelial eNOS is mainly involved in controlling vascular tone, but may provide a uniform background level of NO that determines the baseline levels of nearby neurones (Garthwaite, ). The nNOS has been identified in many stages of the auditory system, from the cochlea through the cochlear nucleus, superior olivary complex (SOC) and inferior colliculus to the auditory cortex (Baizer et al., ; Burette, Petrusz, Schmidt, & Weinberg, ; Coote & Rees, ; Eliasson, Blackshaw, Schell, & Snyder, ; Fessenden, Altschuler, Seasholtz, & Schacht, ; Fessenden, Coling, & Schacht,; Lee, Cho, Huh, Cha, & Yeo, ; Rodrigo et al., ). The presence of nNOS throughout the auditory system suggests that NO contributes significantly to auditory processing and that it does so in a number of ways.…”