Synaptic organization of globular bushy cells in the ventral cochlear nucleus of the cat: A quantitative study

Ostapoff, E.-Michael; Morest, D. Kent

doi:10.1002/cne.903140314

Cited by 63 publications

(64 citation statements)

References 85 publications

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“…Estimates of the number of AN synapses on a globular bushy cell vary from ∼15 to ∼60 (Liberman, 1991;Ostapoff and Morest, 1991;Spirou et al, 2005). These numbers correspond to the effectiveness values in Fig.…”

Section: Primarylike Versus Chopper Responsessupporting

confidence: 66%

Auditory nerve inputs to cochlear nucleus neurons studied with cross-correlation

Young

Sachs

2008

Neuroscience

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The strength of synapses between auditory nerve (AN) fibers and ventral cochlear nucleus (VCN) neurons is an important factor in determining the nature of neural integration in VCN neurons of different response types. Synaptic strength was analyzed using cross-correlation of spike trains recorded simultaneously from an AN fiber and a VCN neuron in anesthetized cats. VCN neurons were classified as chopper, primarylike, and onset using previously defined criteria, although onset neurons usually were not analyzed because of their low discharge rates. The correlograms showed an excitatory peak (EP), consistent with monosynaptic excitation, in AN-VCN pairs with similar best frequencies (49% 24/49 of pairs with best frequencies within ±5%). Chopper and primarylike neurons showed similar EPs, except that the primarylike neurons had shorter latencies and shorter-duration EPs. Large EPs consistent with endbulb terminals on spherical bushy cells were not observed, probably because of the low probability of recording from one. The small EPs observed in primarylike neurons, presumably spherical bushy cells, could be derived from small terminals that accompany endbulbs on these cells. EPs on chopper or primarylike-with-notch neurons were consistent with the smaller synaptic terminals on multipolar and globular bushy cells. Unexpectedly, EPs were observed only at sound levels within about 20 dB of threshold, showing that VCN responses to steady tones shift from a 1:1 relationship between AN and VCN spikes at low sound levels to a more autonomous mode of firing at high levels. In the high level mode, the pattern of output spikes seems to be determined by the properties of the postsynaptic spike generator rather than the input spike patterns. The EP amplitudes did not change significantly when the presynaptic spike was preceded by either a short or long interspike interval, suggesting that synaptic depression and facilitation have little effect under the conditions studied here.

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Section: Primarylike Versus Chopper Responsessupporting

confidence: 66%

Auditory nerve inputs to cochlear nucleus neurons studied with cross-correlation

Young

Sachs

2008

Neuroscience

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“…Scale bar 5 20 µm. Ostapoff and Morest, 1991). The dearth of neuropil staining suggests that axons and terminals of type I primary afferents do not express the Kv3.1 channel.…”

Section: Localization Of Kv31 Immunoreactivity In the Cnmentioning

confidence: 95%

Localization of a high threshold potassium channel in the rat cochlear nucleus

1997

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Potassium channels play a major role in determining the pattern and frequency of neuronal firing. In the cochlear nucleus (CN), various morphologically defined types of neurons have different responses to a sound. We have previously identified one type of cloned K+ channel, termed Kv3.1, which is highly expressed in many auditory neurons. Expression studies indicate that Kv3.1 channels have an unusually high threshold for activation. In this study, we used both in situ hybridization and immunohistochemistry to examine the expression patterns of the Kv3.1 channel in the CN. In the ventral CN, bushy cells hybridized strongly with Kv3.1 specific probes and a subpopulation of stellate/multipolar cells hybridized with Kv3.1 probes. In the dorsal CN, pyramidal and large multipolar/giant cells expressed Kv3.1 mRNA. Abundant Kv3.1 immunolabeling was also observed in the CN. The pattern of immunolabeling revealed that the Kv3.1 protein is distributed along the soma, proximal dendrites, unmyelinated axons, and axon terminals of stained neurons. In the case of pyramidal and octopus cells, no immunolabeling was detected at the somata, even though these cells expressed Kv3.1 mRNA. Computer simulations were used to explore the functional role of the Kv3.1 channel. The simulations indicate that Kv3.1 conductances may contribute to repolarization of large synaptic potentials. When stimulated at high frequencies, the presence of Kv3.1 enhances the ability of a model cell with some of the features of bushy cells to follow high frequency input with temporal precision.

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“…A number of modi¢ed endbulbs from separate auditory nerve ¢bers converge upon a single globular bushy cell (Lorente de Nö , 1981;Fekete et al, 1984;Ostapo¡ and Morest, 1991). This number has been estimated to be 17 (Spirou et al, 1990), representing 60% of the terminal space along the somatic surface (Tolbert and Morest, 1982c).…”

Section: Electron Microscopymentioning

confidence: 99%

The effects of congenital deafness on auditory nerve synapses and globular bushy cells in cats

2000

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It is well known that auditory deprivation affects the structure and function of the central nervous system. Congenital deafness represents one form of deprivation, and in the adult white cat, it has been shown to have a clear effect upon the synaptic interface between endbulbs of Held and spherical bushy cells. It is not known, however, whether all primary synapses are affected and/or whether they are affected in the same way and to the same extent. Thus, we studied a second neuronal circuit in the deaf white cat involving modified (small) endbulbs and globular bushy cells. Compared to normal hearing cats, modified endbulbs of congenitally deaf cats were 52.2% smaller but unchanged in structural complexity. There was also a striking loss of extracellular space between ending and cell body. The somata of postsynaptic globular bushy cells were 13.4% smaller and had enlarged postsynaptic densities. These data reveal that axosomatic synapses demonstrate abnormal structure as a consequence of deafness and that the extent of the abnormalities can vary with respect to the circuits involved. The implication of these observations is that synaptic anomalies would introduce differential delays within separate circuits, thereby desynchronizing neural activity from sound stimuli. This loss of synchronization could in turn disrupt temporal processing and compromise a host of related functions, including language comprehension. ß

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Synaptic organization of globular bushy cells in the ventral cochlear nucleus of the cat: A quantitative study

Cited by 63 publications

References 85 publications

Auditory nerve inputs to cochlear nucleus neurons studied with cross-correlation

Auditory nerve inputs to cochlear nucleus neurons studied with cross-correlation

Localization of a high threshold potassium channel in the rat cochlear nucleus

The effects of congenital deafness on auditory nerve synapses and globular bushy cells in cats

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