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Topography and morphology of the inhibitory projection from superior olivary nucleus to nucleus laminaris in chickens (Gallus gallus).

ABSTRACT: The avian nucleus laminaris (NL) is involved in computation of interaural time differences (ITDs) that encode the azimuthal position of a sound source. Neurons in NL are bipolar, with dorsal and ventral dendritic arbors receiving input from separate ears. NL neurons act as coincidence detectors that respond maximally when input from each ear arrives at the two dendritic arbors simultaneously. Computational and physiological studies demonstrated that the sensitivity of NL neurons to coincident inputs is modulated by an inhibitory feedback circuit via the superior olivary nucleus (SON). To understand the mechanism of this modulation, the topography of the projection from SON to NL was mapped, and the morphology of the axon terminals of SON neurons in NL was examined in chickens (Gallus gallus). In vivo injection of AlexaFluor 568 dextran amine into SON demonstrated a coarse topographic projection from SON to NL. Retrogradely labeled neurons in NL were located within the zone of anterogradely labeled terminals, suggesting a reciprocal projection between SON to NL. In vivo extracellular physiological recording further demonstrated that this topography is consistent with tonotopic maps in SON and NL. In addition, three-dimensional reconstruction of single SON axon branches within NL revealed that individual SON neurons innervate a large area of NL and terminate on both dorsal and ventral dendritic arbors of NL neurons. The organization of the projection from SON to NL supports its proposed functions of controlling the overall activity level of NL and enhancing the specificity of frequency mapping and ITD detection.

SUBMITTER: Tabor KM

PROVIDER: S-EPMC3299086 | biostudies-literature | 2011 Feb

REPOSITORIES: biostudies-literature

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Topography and morphology of the inhibitory projection from superior olivary nucleus to nucleus laminaris in chickens (Gallus gallus).

Tabor Kathryn M KM Wong Rachel O L RO Rubel Edwin W EW

The Journal of comparative neurology 20110201 2

The avian nucleus laminaris (NL) is involved in computation of interaural time differences (ITDs) that encode the azimuthal position of a sound source. Neurons in NL are bipolar, with dorsal and ventral dendritic arbors receiving input from separate ears. NL neurons act as coincidence detectors that respond maximally when input from each ear arrives at the two dendritic arbors simultaneously. Computational and physiological studies demonstrated that the sensitivity of NL neurons to coincident in ...[more]

PMID: 21165979

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Project description:The superior olivary complex (SOC) is an essential auditory brainstem structure involved in sound localization. In order to identify the genetic program underlying its maturation, we profiled the transcriptome of the rat SOC at postnatal days (P)0, P4, P16, and P25, using genome-wide microarrays (41,012 sequences). Differences in gene expression between two consecutive stages were highest between P4 versus P16 (3.6%), but dropped to 0.06% between P16 versus P25. To identify SOC-related genetic programs, we also profiled the brain at P4 and P25. Differentially expressed sequences between SOC and brain almost doubled from P4 (4.4%) to P25 (7.6%). These datademonstrate considerable molecular specification around hearing onset, which is rapidly finalized. Prior to hearing onset, several transcription factors associated with the peripheral auditory system were up-regulated, likely coordinating auditory system development. Additionally, serotonin-related genes and crystalline-gamma subunits were highly expressed. The molecular repertoire of mature neurons was sculpted by SOC-related up- and down-regulation of several protein categories, among which voltage-gated channels and myelination were prominent. Comparison with the brain revealed a significant enrichment of deafness-related oligos in the SOC-related genetic program (26 in the SOC, only 11 in the brain). Furthermore, 29 out of 453 SOC-related oligos mapped within 19 genetic intervals associated with hearing impairment. Together, we identified sequential genetic programs in the SOC, thereby pinpointing candidates which may guide its development and ensure proper function. The enrichment of deafness-related genes in the SOC may have implications for restoring hearing, as central auditory structures might be more severely affected than previously appreciated. This SuperSeries is composed of the SubSeries listed below. The genome wide expression during the postnatal development of the SOC was investigated at four different time points: at postnatal (P) day 0, P4, P16 and P25. Concerning the brain, P4 and P25 were used. Samples were hybridized onto two color platforms. At least 6 up to nine biological replicates per sample were performed.

Project description:BackgroundThere has been considerable confusion concerning the number and classification of Sarcocystis spp. in chickens. Scarce nucleotide data of Sarcocystis spp. from chickens are provided in GenBank. The study aimed to investigate the morphological and molecular characteristics of Sarcocystis spp. found in chickens in China.MethodsTissues from 33 chickens were collected in 2019. Sarcocysts were observed using light (LM) and transmission electron microscopy (TEM). Individual sarcocysts from different chickens were selected for DNA extraction, and five loci, 18S rDNA, 28S rDNA, ITS1 region, the mitochondrial cox1 gene and the apicoplastic rpoB gene, were amplified from each sarcocyst, sequenced and analyzed.ResultsOnly S. wenzeli was found in 14 of 33 (42.4%) chickens. Under LM, the sarcocysts were microscopic and exhibited palisade-like villar protrusions measuring 1.5-2.8 μm. Ultrastructurally, the sarcocyst wall contained numerous stubby hill-like villar protrusions. The protrusions included scattered microtubules, which extended from the tips of the protrusions into the ground substance. The five loci were successfully sequenced and the sequences deposited in GenBank. At 18S rDNA, ITS1 and cox1, the most similar sequences in GenBank were those of Sarcocystis sp. obtained from the brains of chickens, i.e. 99.9-100%, 98.1-98.5% and 99.3% identity, respectively. The five loci (18S rDNA, 28S rDNA, ITS1, cox1 and rpoB) showed different levels of interspecific sequence similarity with other closely related species of Sarcocystis (e.g. 99.8%, 99.0-99.2%, 89.3-89.7%, 98.5%, and 97.5%, respectively, with S. anasi). Phylogenetic analysis based on four of the loci (18S rDNA, cox1, rpoB and ITS1) revealed that S. wenzeli formed an independent clade with Sarcocystis spp. that utilize geese or ducks as intermediate hosts and canines as the known or presumed definitive host.ConclusionsTo our knowledge, the sequences of 28S rDNA and rpoB reported here constitute the first records of genetic markers of Sarcocystis spp. in chickens. Based on molecular analysis, S. wenzeli might be responsible for the neurological disease in chickens, and ITS1 and rpoB are more suitable for discriminating it from closely related Sarcocystis spp. Phylogenetic analysis revealed that S. wenzeli presents a close relationship with Sarcocystis spp. in geese or ducks.

Dataset Information

Topography and morphology of the inhibitory projection from superior olivary nucleus to nucleus laminaris in chickens (Gallus gallus).

Publications

Topography and morphology of the inhibitory projection from superior olivary nucleus to nucleus laminaris in chickens (Gallus gallus).

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