Morphology of HRP-labelled cochlear nerve axons in the dorsal cochlear nucleus of the developing hamster

Schweitzer, Laura; Cecil, Tina

doi:10.1016/0378-5955(92)90056-s

Cited by 15 publications

(12 citation statements)

References 38 publications

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“…As axons mature, they become smooth and larger in diameter. These observations are consistent with studies which have noted varicosities on developing axons that become less common in older animals (Young and Rubel 1986;Schweitzer and and Cecil 1992;Kandler and Friauf 1993). One aspect of axonal morphology that we do not observe with the NF immunohistochemical method is terminal formations representing growth cones.…”

Section: Discussionsupporting

confidence: 94%

“…One aspect of axonal morphology that we do not observe with the NF immunohistochemical method is terminal formations representing growth cones. Animal studies of developing axons that utilize HRP, Golgi impregnation, DiI or biocytin consistently observe expansions at the leading tips of axons that are interpreted as growth cones (Schweitzer and Cant 1984;Young and Rubel 1986;Schweitzer and Cecil 1992;Kandler and Friauf 1993). The probable explanation for the lack of visualization of growth cones in our material is that growth cone constituent filaments consist of actin, neuromodulin and other specialized proteins, rather than neurofilaments (e.g.…”

Section: Discussionmentioning

confidence: 82%

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Axogenesis in the human fetal auditory system, demonstrated by neurofilament immunohistochemistry

Moore

Guan

Shi

1996

Anatomy and Embryology

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Morphological, electrophysiological and behavioral evidence indicates that the onset of rapid, synchronized conduction of auditory impulses occurs in the human brainstem during the 28th-29th fetal weeks. This implies that axonal connections in the brainstem auditory pathway are generated prior to this time. In order to investigate the sequence of axogenic events in the human brainstem pathway, we employed immunohistochemical techniques and an antibody to neurofilament protein. Immunostaining for axonal neurofilaments in an age-graded series of fetal brains demonstrates that a small number of cochlear nerve axons have invaded the ventral cochlear nucleus by the 16th fetal week. By this same time point, a limited number of trapezoid body-lateral lemniscus axons have reached the superior olivary complex and inferior colliculus. Between gestational weeks 16 and 26, there is marked expansion and collateralization of the ascending pathway from cochlear nerve to inferior colliculus. By week 26, ascending axons have begun to form plexuses of terminal neuropil within all of the brainstem auditory nuclei. Beginning in week 22, there is development of commissural axons (dorsal commissure of the lateral lemniscus and commissure of the inferior colliculus) and descending projections (descending collicular axons and olivocochlear bundle). This early establishment of a mature pattern of axonal connections presumably forms the basis for the appearance of myelin, acousticomotor reflexes and recordable brainstem responses by fetal week 29.

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Section: Discussionsupporting

confidence: 94%

Section: Discussionmentioning

confidence: 82%

Axogenesis in the human fetal auditory system, demonstrated by neurofilament immunohistochemistry

Moore

Guan

Shi

1996

Anatomy and Embryology

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“…However, if the thickness is normalized for the increase in the size of the CN with age, the mean normalized thickness of the P6 laminae is not significantly different from that of the adult laminae in any of the three major CN subdivisions. It is possible that individual fiber terminal fields are relatively restricted at birth and that they expand as the animal matures as suggested by studies in the DCN of hamsters (Schweitzer and Cecil, 1992). If individual arbors were initially narrow, it would account for the relatively sparse fiber density in the projection laminae of very young kittens.…”

Section: Discussionmentioning

confidence: 95%

Topography of spiral ganglion projections to cochlear nucleus during postnatal development in cats

Snyder

Leake

1997

J. Comp. Neurol.

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A fundamenntal organizational principle of the central auditory system is that virtually all areas are tonotopically organized. However, we know very little about the timing or mechanisms that are responsible for the development of this organization. When cats are born, their auditory nervous systems are extremely immature, and their hearing thresholds are very high. Until postnatal days 7-10 (P7-10), cats have behavioral and physiological thresholds which are near or above the pain threshold for adults and also have poor frequency selectivity. Physiological thresholds for auditory nerve fibers and cochlear nucleus neurons are typically above 100-120 dB SPL (sound pressure level re 20 microPa). Three weeks later (at approximately P31), the sensitivity and frequency discrimination (tuning) of these neurons approximate adult values. This study examines the development of the tonotopic projections from the spiral ganglion to the cochlear nucleus during the period in cat development in which the auditory system undergoes the transition from being essentially nonfunctional to having adult-like function. With the animals heavily anesthetized, the cochleas were surgically exposed in kittens ranging in age from P6 to P45. Focal injections of Neurobiotin (NB) were made into Rosenthal's canal, labeling a small cluster of cells in the spiral ganglion of each cochlea. The projections of these labeled cells were visualized as frequency-specific bands of labeled axons and terminals in all major subdivisions of the cochlear nucleus. The thickness of these bands (i.e., the dimension of the bands orthogonal to the isofrequency representation and across the frequency gradient) were measured and compared to similar projections in adults. As in adult cats, the thickness of the bands varied only slightly with the location of the injection site (frequency representation) over a range of 1-7 mm from the cochlear base (45-13 kHz). Moreover, band thickness did not vary significantly with age. These data indicate that the tonotopic organization of spiral ganglion projections to the cochlear nucleus is as precise in kittens as young as P6 as it is in adults.

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“…Changes in either one of these could be interpreted as part of a process of refinement. For example, some studies have reported that, although axonal morphology and size remain unchanged during development, the target nucleus increases in size (Schweitzer and Cecil, 1992;Rathjen et al, 2003). This leads to a progressive reduction in the proportion of the nucleus innervated and could contribute to maturational changes in response properties.…”

Section: Anatomical Refinement During Developmentmentioning

confidence: 96%

Development of the projection from the nucleus of the brachium of the inferior colliculus to the superior colliculus in the ferret

Nodal

Doubell

Jiang

et al. 2005

J of Comparative Neurology

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Neurons in the deeper layers of the superior colliculus (SC) have spatially tuned receptive fields that are arranged to form a map of auditory space. The spatial tuning of these neurons emerges gradually in an experience-dependent manner after the onset of hearing, but the relative contributions of peripheral and central factors in this process of maturation are unknown. We have studied the postnatal development of the projection to the ferret SC from the nucleus of the brachium of the inferior colliculus (nBIC), its main source of auditory input, to determine whether the emergence of auditory map topography can be attributed to anatomical rewiring of this projection. The pattern of retrograde labeling produced by injections of fluorescent microspheres in the SC on postnatal day (P) 0 and just after the age of hearing onset (P29), showed that the nBIC-SC projection is topographically organized in the rostrocaudal axis, along which sound azimuth is represented, from birth. Injections of biotinylated dextran amine-fluorescein into the nBIC at different ages (P30, 60, and 90) labeled axons with numerous terminals and en passant boutons throughout the deeper layers of the SC. This labeling covered the entire mediolateral extent of the SC, but, in keeping with the pattern of retrograde labeling following microsphere injections in the SC, was more restricted rostrocaudally. No systematic changes were observed with age. The stability of the nBIC-SC projection over this period suggests that developmental changes in auditory spatial tuning involve other processes, rather than a gross refinement of the projection from the nBIC.

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Morphology of HRP-labelled cochlear nerve axons in the dorsal cochlear nucleus of the developing hamster

Cited by 15 publications

References 38 publications

Axogenesis in the human fetal auditory system, demonstrated by neurofilament immunohistochemistry

Axogenesis in the human fetal auditory system, demonstrated by neurofilament immunohistochemistry

Topography of spiral ganglion projections to cochlear nucleus during postnatal development in cats

Development of the projection from the nucleus of the brachium of the inferior colliculus to the superior colliculus in the ferret

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