Biomedical subjects

D Oertel

Publications and source records attributed to D Oertel.

At least 37 records · Page 2Linked to original sources

PubMed1993

Tuberculoventral cells of the dorsal cochlear nucleus of mice: intracellular recordings in slices.

1. Intracellular recordings were made from six tuberculoventral cells (also called vertical or corn cells) whose identity was confirmed by labeling with biocytin, with the aim of understanding their projection patterns and how their synaptic inputs and their intrinsic electrical properties shape their responses to activation of auditory nerve fibers. 2. The cell bodies, dendrites, and local axonal terminals of all six tuberculoventral cells lay in narrow bands, 70-100 microns wide and parallel to the path of auditory nerve fibers, in the dorsal cochlear nucleus (DCN). Terminals in the ventral cochlear nucleus (VCN) also lay in narrow bands, parallel to the path of auditory nerve fibers in either or both the anteroventral and posteroventral cochlear nuclei. 3. When depolarized with current, tuberculoventral cells fired regularly. The peaks of action potentials were usually overshooting and were followed by two afterhyperpolarizations, resembling other cells of the DCN. Unlike some other cells in the DCN, however, neither of the afterhyperpolarizations resulted in an undershoot of the resting potential in the presence of depolarizing currents stronger than 0.3 nA. The second afterhyperpolarization was more variable than the first. 4. Shocks to the auditory nerve evoked monosynaptic as well as polysynaptic excitation and weak polysynaptic inhibition. These results show that, in addition to receiving excitation directly through auditory nerve fibers, tuberculoventral cells also receive excitation through interneurons. 5. To locate the interneurons in the cochlear nuclei whose activation affects a tuberculoventral cell monosynaptically or polysynaptically, glutamate was applied focally to various loci in the VCN while responses were recorded in a target tuberculoventral cell that was subsequently labeled. Excitation of this tuberculoventral cell arose from a rostrocaudal band in the VCN. 6. The results are consistent with tuberculoventral cells receiving excitatory synaptic input from auditory nerve fibers and from T stellate cells in the VCN. They could be inhibited by D stellate cells in the VCN.

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PubMed1991

Tuberculoventral neurons project to the multipolar cell area but not to the octopus cell area of the posteroventral cochlear nucleus.

Tuberculoventral neurons in the deep layer of the dorsal cochlear nucleus (DCN) provide frequency-specific inhibition to neurons in the anteroventral cochlear nucleus (AVCN) of the mouse (Wickesberg and Oertel, '88, '90). The present experiments examine the projection from the deep DCN to the posteroventral cochlear nucleus (PVCN). Horseradish peroxidase (HRP) injections into the PVCN reveal that the multipolar cell area, but not the octopus cell area, is innervated by neurons in the deep layer of the DCN. Injections into the multipolar cell area, in the rostral and ventral PVCN, labeled neurons across the entire rostrocaudal extent of the deep DCN. The labeled tuberculoventral neurons generally lay within the band of labeled auditory nerve terminals in the DCN. Injections of HRP into the octopus cell area, in the dorsal caudal PVCN, labeled almost no cells within the band of auditory nerve fiber terminals that were labeled by the same injection. The inhibition from tuberculoventral neurons onto ventral cochlear nucleus (VCN) neurons is likely to be mediated by glycine (Wickesberg and Oertel, '90). Slices of the cochlear nuclear complex were immunolabeled by an antibody against glycine conjugated with glutaraldehyde to bovine serum albumin (Wenthold et al., '87). Glycine-like immunoreactivity was found throughout the DCN, the AVCN and the multipolar cell area, but there was little labeling in the octopus cell area. This finding provides independent evidence that tuberculoventral neurons do not innervate the octopus cell area and indicates that the octopus cell area is anatomically and functionally distinct.

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PubMed1991

The role of intrinsic neuronal properties in the encoding of auditory information in the cochlear nuclei.

It is now possible to relate the intrinsic electrical properties of particular cells in the cochlear nuclei of mammals with their biological function. In the layered dorsal cochlear nucleus, information concerning the location of a sound source seems to be contained in the spatial pattern of activation of a population of neurons. In the unlayered, ventral cochlear nucleus, however, neurons carry information in their temporal firing patterns. The voltage-sensitive conductances that make responses to synaptic current brief enable bushy cells to convey signals from the auditory nerve to the superior olivary complex with a temporal precision of at least 120 microseconds.

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PubMed1990

Morphology and physiology of cells in slice preparations of the posteroventral cochlear nucleus of mice.

In an effort to understand what integrative tasks are performed in the cochlear nuclei, the present study was undertaken to describe neuronal circuits in the posteroventral cochlear nucleus (PVCN) anatomically and physiologically. The cochlear nuclear complex receives auditory information from the cochlea through the auditory nerve. Within the cochlear nuclei, signals travel along several parallel and interconnected pathways. From the cochlear nuclei, transformed versions of the signals are passed to higher auditory centers in the brainstem. We have recorded electrophysiological responses from cells that were subsequently visualized with horseradish peroxidase (HRP). Responses to shocks to the auditory nerve root and to intracellularly injected current pulses were recorded and correlated with morphology. Two types of stellate cells and octopus cells were distinguished. T stellate cells project out of the cochlear nuclei through the Trapezoid body; D stellate cells do not. The axons of D stellate cells extend Dorsalward to the dorsal cochlear nucleus (DCN) but have not been traced out of the nucleus. Both T and D stellate cells have terminal collaterals in the multipolar cell region of the PVCN and in the DCN. The endings of one T stellate cell formed a narrow band rostrocaudally in the fusiform cell layer of the DCN that resembled an isofrequency band. The endings of one D stellate cell lay closely apposed to multipolar cells in the deep layer of the DCN. The dendrites of T stellate cells are often aligned along the path of auditory nerve fibers and end in tufts, whereas those of D stellate cells extend radially in the plane of the lateral surface of the PVCN toward granule cell areas and branch sparingly. Octopus cells have dendrites oriented perpendicularly to the path of auditory nerve fibers. Their axons were cut medially in the slices; none had collateral branches. Both T and D stellate cells were monosynaptically excited to threshold by shocks to the nerve root, indicating that they could participate in local circuits that we measure physiologically. T stellate cells have action potentials that peak at about 0 mV and are followed by single undershoots. The D stellate cell that was best impaled fired overshooting action potentials that were followed by double undershoots. Octopus cells were monosynaptically excited to threshold by shocks to the auditory nerve.

Action Potentials↗

PubMed1990

Delayed, frequency-specific inhibition in the cochlear nuclei of mice: a mechanism for monaural echo suppression.

To understand how auditory information is processed in the cochlear nuclei, it is crucial to know what circuitry exists and how it functions. Previous anatomical experiments have shown that neurons in the deep layer of the dorsal cochlear nucleus (DCN) project topographically to the anteroventral cochlear nucleus (AVCN) (Wickesberg and Oertel, 1988). Because interneurons in the DCN and their targets in AVCN are excited by the same group of auditory nerve fibers, the projection is frequency-specific. Here we report that microinjections of glutamate in the DCN evoke trains of IPSPs in individual, impaled AVCN neurons in brain slices of the cochlear nuclear complex. Only injections along a rostrocaudal band in the DCN, matching the anatomical projection of tuberculoventral neurons, evoke IPSPs; elsewhere, there were no responses to the glutamate. The inhibition is blocked by 0.5 microM strychnine. Both bushy and stellate cells are targets of the inhibitory projection. Inhibition in the AVCN is delayed by an additional synaptic delay with respect to the excitation. Delayed, frequency-specific inhibition allows the first wavefront to be transmitted to higher auditory centers by bushy and stellate cells, while following inputs encoding signals of similar frequencies are attenuated at least for the duration of an IPSP. These findings are consistent with results from psychoacoustic experiments and suggest that this circuit provides a source of monaural echo suppression.

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PubMed1989

Jaundiced Gunn rats have increased synaptic delays in the ventral cochlear nucleus.

Recordings were made in vitro from cochlear nuclei of Gunn rats, a strain with a recessive mutation that predisposes rats to hyperbilirubinemia at birth. Delays between shocks to the auditory nerve and earliest synaptic responses of the cochlear nuclear neurons were on average longer in Gunn rats than in heterozygotes. Injections of sulfonamide further increased average synaptic delays in jaundiced rats. Responses to injected current in rats were like those in mice.

Action Potentials↗

PubMed1989

Morphology and physiology of cells in slice preparations of the dorsal cochlear nucleus of mice.

Horseradish peroxidase (HRP) was injected into cells from which intracellular recordings were made in slices of the dorsal cochlear nucleus (DCN) in order to correlate physiology with morphology. In general, the morphology of cells labeled intracellularly with HRP corresponded to those made with Golgi impregnations in mice and other mammals. The following cells were labeled: one granule cell, four cartwheel cells, eight fusiform cells, two other cells in the fusiform cell layer, and two tuberculoventral association cells in the deep layers of the DCN. The axon of the granule cell runs parallel to isofrequency laminae with collaterals branching perpendicularly and running along the tonotopic axis. The cartwheel cells have dendrites in the molecular layer that are densely covered with spines. The axon of one cell terminates just dorsally to the cell body. Fusiform cells have the characteristic spiny, apical and smooth, basal dendrites. The basal dendrites are conspicuously oriented parallel to isofrequency laminae. Axons of the fusiform cells exit through the dorsal acoustic stria without branching. The two tuberculoventral association cells in the deep DCN have axons that terminate both in the deep DCN, within the same isofrequency lamina that contains the cell body, and in the ventral cochlear nucleus (VCN). Intracellular recordings from 11 of these cells show that they cannot be distinguished on the basis of their responses to intracellularly injected current. All cell types fired large action potentials that were followed by a fast and a slower undershoot, distinguishing them from cells of the VCN but not from one another. Most cells responded to shocks of the auditory nerve root with early EPSPs and later IPSPs. The latencies of EPSPs show that some were monosynaptic and others polysynaptic. That there was no systematic relationship between the latencies of EPSPs and the cell types from which they were recorded shows that shocks to the nerve root may have activated more than just the large, myelinated, auditory nerve fibers.

Action Potentials↗

PubMed1989

Auditory nerve neurotransmitter acts on a kainate receptor: evidence from intracellular recordings in brain slices from mice.

Intracellular recordings from neurons in brain slice preparations of the mouse ventral cochlear nucleus (VCN) were used to examine the actions of excitatory amino acid agonists and antagonists. Synaptic responses to electrical stimulation of the auditory nerve root were partially blocked by kynurenic acid, an antagonist that is specific for glutamate receptors. The antagonists specific for N-methyl-D-aspartate (NMDA), DL-2-amino-5-phosphonovalerate (APV) and Mg2+, did not affect the response, arguing against a role for NMDA receptors at the VIIIth nerve synapse. To test postsynaptic sensitivity to excitatory amino acid agonists, responses to bath applications were measured in VCN neurons while synaptic transmission was blocked by the removal of Ca2+ from the bath or by the addition of tetrodotoxin. Neurons in the VCN were 500-1000 times more sensitive to kainate than to glutamate or aspartate. In the absence of Mg2+, they were also sensitive to NMDA. The responses to kainate and glutamate were increased by the removal of calcium from the bath. These results imply that VCN neurons have both kainate and NMDA receptors and that synaptic transmission between auditory nerve fibers and neurons in the cochlear nuclear complex could be mediated by a substance related to kainate.

Action Potentials↗

PubMed1988

Tonotopic projection from the dorsal to the anteroventral cochlear nucleus of mice.

To understand how auditory information is processed in the cochlear nuclei, it is crucial to know what circuitry exists and how it functions. In slice preparations, horseradish peroxidase (HRP) injections into the anteroventral cochlear nucleus (AVCN) reveal two circuits: a connection between the dorsal cochlear nucleus (DCN) and AVCN and a local circuit confined to the AVCN. Extracellular injection in the AVCN labels a band of cells in the DCN. The labeled cells in the DCN lie within a band of auditory nerve fiber terminals that are labeled by the same injection, showing that the connection from the DCN to the AVCN is frequency specific. The injections into the AVCN also labeled a cluster of neurons in the AVCN dorsal to the injection site. These cells may be interneurons that relay information from areas encoding higher frequencies to areas encoding lower frequencies within the AVCN. In the parasagittal plane, the AVCN is organized along two orthogonal axes that are indicated with HRP labeling of fibers and cell bodies. The tonotopic axis runs approximately dorsoventrally; the isofrequency axis runs approximately rostrocaudally. The axons of labeled DCN neurons and the cluster lie along the tonotopic axis, whereas the labeled auditory nerve fibers define the isofrequency axis. Where they cross is where HRP is taken up by the fibers. The area of uptake is small and lies in the middle of the darkly stained injection site.

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PubMed1988

Intrinsic properties of neurones in the dorsal cochlear nucleus of mice, in vitro.

1. Intracellular recordings were made from the dorsal cochlear nucleus (DCN) in slices of the cochlear nuclear complex. Probably the larger and most frequent cells were impaled. 2. The steady-state current-voltage (I-V) properties of all cells impaled were nonlinear. The I-V curve was steepest in the voltage range depolarized from the resting potential and most shallow when the cell was hyperpolarized from rest by more than about 10 mV. Thus, the inwardly rectifying I-V characteristics of cells in the DCN distinguish them from those of ventral cochlear nuclear neurones (Oertel, 1983). 3. When depolarized with current, most cells fired trains of large, all-or-none action potentials. The undershoot after single spikes comprised an initial, fast component followed by a second, slower wave. A few cells (15%) generated bursts of smaller, graded spikes in addition to the large ones. 4. Repetitive firing evoked by depolarizing pulses of current was followed by an after-hyperpolarization whose magnitude depended on the strength and duration of the preceding current pulse. 5. Blocking the large action potentials with tetrodotoxin (TTX) revealed Ca2+-dependent spikes in all cells examined. 6. The steady-state I-V relationship became linear in the presence of TTX, suggesting that a persistent Na+ conductance probably mediates the inward rectification seen above the resting potential. 7. Muscarine at micromolar concentrations excited cells and increased their input resistance.

4-Aminopyridine↗

PubMed1988

Synaptic connections in the dorsal cochlear nucleus of mice, in vitro.

1. Intracellular recordings were made from the dorsal cochlear nucleus (DCN) in slices that contained the root of the auditory nerve and parts of the dorsal and ventral cochlear nuclei. Probably the largest and most common cells were impaled. 2. Weak shocks to the nerve usually evoked an excitatory postsynaptic potential (EPSP) that lasted about 90 ms and whose latency was often less than 1.2 ms, indicating monosynaptic input. 3. Stronger shocks elicited a larger EPSP and a later train of inhibitory postsynaptic potentials (IPSPs). Increasing the stimulus voltage shortened the latency of the train of IPSPs and increased its efficacy so that at large stimulus strengths inhibition dominated the synaptic response. 4. To determine whether any of the neuronal circuitry which generated the synaptic responses involved the ventral cochlear nucleus, recordings were made from slices containing only the dorsal nucleus. Synaptic responses to stimulation of the pial surface of the isolated DCN resembled those driven from the nerve root. That is, weak shocks evoked long-lasting, monosynaptic EPSPs and stronger stimuli elicited a larger EPSP followed by trains of IPSPs. The DCN, therefore, contains intrinsic inhibitory interneurones. 5. The parallel fibres of the DCN course superficially, near the stimulating electrodes, whereas the axons of the auditory nerve terminate in deeper areas. Thus, the monosynaptic EPSPs evoked from the pial surface are probably generated by parallel fibres. Apparently the inhibitory interneurones are also excited by a circuit including parallel fibres. 6. The putative neurotransmitter of parallel fibres, glutamate, excited all neurones tested. 7. Cells were sensitive both to glycine and to gamma-aminobutyric acid (GABA). Only strychnine, however, not picrotoxin or bicuculline, blocked IPSPs.

Action Potentials↗

PubMed1987

Maturation of synapses and electrical properties of cells in the cochlear nuclei.

Auditory nerve fibers carry impulses from the cochlea to the cochlear nuclei. There the temporal firing patterns of auditory nerve fibers are preserved by some cells and altered by others. The two factors which govern how firing patterns are shaped are (1) the intrinsic electrical properties of cells that determine the size and time course of voltage changes caused by synaptic currents and (2) the synaptic circuitry between cells. The electrical properties of cells were measured by recording the responses to current injected intracellularly into brain slice preparations. The synaptic responses to electrical shocks of the auditory nerve were used to determine the functional properties of synaptic connections. The three distinct types of electrical properties of cells that can be distinguished electrophysiologically in similar preparations of mature tissue, bushy and stellate cells in the ventral cochlear nucleus [(1984) J. Neurosci. 4, 1577-1588] and cells in the dorsal cochlear nucleus [Hirsch and Oertel (1987) (submitted); Oertel et al. (1987) In: Functions of the Auditory System, Editor: S. Hassler. J. Wiley and Sons (in press)] can be differentiated at least as early as 7 days after birth. Young cells, however, have higher input resistances and lower input capacitances than mature cells, and they cannot sustain high firing rates. Bushy and stellate cells in the ventral cochlear nucleus respond to electrical stimulation of the auditory nerve with both excitatory and inhibitory postsynaptic potentials as early as 4 days after birth. The synaptic potentials occur with longer and more variable latencies than in mature cells and synapses fatigue more easily, however. Cells of the dorsal cochlear nucleus also receive both excitatory and inhibitory synaptic inputs 4 days after birth, upon stimulation of the auditory nerve. No systematic changes were detected in these synaptic responses as a function of age but this may have been because the variability in the shape and timing of synaptic responses was large even in mature tissue.

Action Potentials↗

PubMed1986

Inhibitory circuitry in the ventral cochlear nucleus is probably mediated by glycine.

Intracellular recordings from brain slice preparations of the ventral cochlear nuclei (VCN) of mice have shown that both the major cell types, stellate and bushy cells, distinguishable by their responses to intracellularly injected current (Oertel, 1983; Wu and Oertel, 1984), receive late inhibitory as well as early excitatory inputs when the auditory nerve is stimulated electrically. When the extracellular Cl- concentration was lowered or when the intracellular Cl- was raised, the reversal potential of IPSPs became more positive; the reversal potentials were independent of the extracellular K+ concentration. Therefore, IPSPs result from increases in Cl- permeability. To determine whether either or both GABA or glycine might mediate the inhibition, the sensitivity of cells to bath-applied putative neurotransmitters was tested. All cells responded to applications of 0.1-10 mM GABA and glycine with large drops in input resistance; these drops were Cl- dependent. To determine which of these 2 substances was more likely to mediate the IPSPs, antagonists specific to GABA and glycine were tested for their ability to block the IPSPs. All IPSPs were eliminated by 1 microM strychnine, a blocker of glycine-mediated inhibition; they were not consistently blocked by 100 microM bicuculline or by 100 microM picrotoxin, blockers of GABA-mediated inhibition. These results indicate that the inhibition is likely to be mediated by glycine. A simple interpretation of the finding that IPSPs have latencies (1.2-4 msec) at least 2X as long as EPSPs (0.6-0.9 msec) is that cells in the VCN are excited monosynaptically by auditory nerve fibers, and that they are inhibited disynaptically through interneurons within the VCN. To test physiologically whether EPSPs and IPSPs are, respectively, monosynaptic and polysynaptic, 500-700 microM sodium pentobarbital was applied to the preparation. Pentobarbital raised the thresholds of all impaled cells and their synaptic inputs. EPSPs could be evoked in the presence of pentobarbital by raising the stimulus strength, as expected when thresholds are raised in a monosynaptic circuit; even if the thresholds of IPSPs were lower than those of EPSPs in normal saline, they were raised above those of EPSPs in the presence of pentobarbital. The finding that the thresholds of IPSPs are raised more than those of EPSPs supports the interpretation that IPSPs are mediated through a polysynaptic pathway, and this may explain why inhibition has been detected inconsistently in vivo.

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PubMed1985

Use of brain slices in the study of the auditory system: spatial and temporal summation of synaptic inputs in cells in the anteroventral cochlear nucleus of the mouse.

One of the more dramatic technological developments in recent years in neurobiology is the ability to extract a slice of brain tissue and to maintain its viability over extended periods of time. The development of brain slice preparations of the mammalian central nervous system provides a powerful tool for studying the physiology and pharmacology of neurons. In vitro preparations allow stable intracellular recordings to be made from cells. The characteristics of synaptic potentials and the intrinsic electrical properties can be measured while the extracellular environment is controlled and manipulated. Intracellular physiological studies in the anteroventral cochlear nucleus reveal that different morphological classes of cells have characteristic intrinsic electrical properties. Bushy cells are particularly well suited to preserve and convey the temporal firing pattern of inputs from the auditory nerve. Stellate cells can transform inputs from the auditory nerve by summing in time and space.

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PubMed1984

Cells in the anteroventral cochlear nucleus are insensitive to L-glutamate and L-aspartate; excitatory synaptic responses are not blocked by D-alpha-aminoadipate.

Auditory nerve fibers transmit signals from the cochlea to the 3 regions of the cochlear nuclear complex, the anteroventral (AVCN), posteroventral, and dorsal cochlear nucleus in the brainstem. It has been suggested that the amino acids L-aspartate and L-glutamate might serve as a neurotransmitter in auditory nerve fibers. The sensitivity of postsynaptic cells in the cochlear nuclei to these amino acids has been tested by iontophoretic techniques. One difficulty with these experiments is that responses were recorded only extracellularly. A second difficulty is that the concentrations needed to affect cells could not be determined. To avoid these difficulties a brain slice preparation was used to test the sensitivity of cells in the AVCN to bath applied L-glutamate and L-aspartate at concentrations ranging from 10(-5) to 10(-2) M. All cells that were tested in the cochlear nuclear complex were insensitive at all concentrations used; the resting potentials and the input resistances remained unchanged and the synaptic responses to electrical stimulation of the auditory nerve were not desensitized. All cells that were tested in the hippocampus, however, depolarized in the presence of 10(-4) M L-glutamate and L-aspartate. The synaptic responses to electrical stimulation of the auditory nerve were not blocked by D-alpha-aminoadipate, an amino acid which has been shown to block excitation of cells in the cochlear nuclei by auditory nerve fibers. The results are not consistent with L-glutamate and L-aspartate serving as neurotransmitters in the AVCN.

2-Aminoadipic Acid↗

PubMed1984

Intracellular injection with horseradish peroxidase of physiologically characterized stellate and bushy cells in slices of mouse anteroventral cochlear nucleus.

Nissl-stained tissue from brain slice preparations of the anteroventral cochlear nucleus of the mouse resembles tissue fixed in situ. Multipolar, spherical, globular, and granule cells can be distinguished after intracellular injection with horseradish peroxidase (HRP). Stellate cells have relatively large dendritic fields; their axons have collaterals which terminate within the cochlear nuclear complex. Bushy cells have smaller dendritic fields; where they can be seen, axons have no collaterals. Granule cells have few short dendrites; their very fine axons branch close to the cell body and could be followed only for short distances. Intracellular recordings from six stellate cells labeled by intracellular injection of HRP revealed that they have linear current-voltage relationships around the resting potential and that they respond to suprathreshold depolarization with large, regularly firing action potentials. Intracellular recordings from four bushy cells, also labeled by injection of HRP, showed that these cells have nonlinear current-voltage relationships around the resting potential and that they respond to suprathreshold depolarizations with only one or two small action potentials. The anatomical and physiological features of bushy cells reduce summing in time and space and make bushy cells well suited to preserve the firing patterns of auditory nerve inputs. The anatomical and physiological features of stellate cells, in contrast, allow summing in time and space.

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PubMed1983

Physiological response properties of cells labeled intracellularly with horseradish peroxidase in cat dorsal cochlear nucleus.

The physiology and morphology of fusiform cells in the dorsal cochlear nucleus were studied using extracellular and intracellular recording and intracellular injection of horseradish peroxidase. Fusiform cells displayed a variety of responses to tone pips presented at the characteristic frequency; most often these cells exhibited the pauser/buildup pattern defined in earlier studies. The response pattern of each neuron was dependent on frequency and sound-pressure level. Tone pips evoked short-lasting depolarizations of about 10 mV and long-lasting hyperpolarizations of about 10 mV in cells whose resting potentials were -50 to -65 mV. The time courses of both the excitation and the inhibition depended on frequency and sound-pressure level. Generally the depolarization was sustained for the duration of the tone pip, whereas the hyperpolarization could last as long as 600 ms after the end of the tone pip. Often a neuron exhibited a sustained chopper pattern after microelectrode impalement. This was probably a result of a decrease in membrane potential which altered the relative effectiveness of the excitatory and inhibitory inputs. The large, bitufted fusiform cells had many apical dendrites, which branched one to five times and were covered with spines, and fewer basal dendrites, which exhibited little branching and had few appendages. The morphology of fusiform cells varied systematically as a function of location within the dorsal cochlear nucleus. Response patterns for tone pips were not exclusive to individual cell types as two nonfusiform cells were found to exhibit a buildup pattern. Axons of injected neurons left the nucleus via the dorsal acoustic stria and 14 of 15 had collaterals within the dorsal cochlear nucleus.

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PubMed1983

Physiological response properties of cells labeled intracellularly with horseradish peroxidase in cat ventral cochlear nucleus.

To determine the correspondence between anatomical and physiological cell types in the ventral cochlear nucleus of the cat, intracellular injections of horseradish peroxidase were made into cells whose extracellular and intracellular responses to sound had been studied. Three identified cells responded to a short tone burst at their characteristic frequencies with an onset pattern. This pattern is characterized by a strong response to the onset of the stimulus. One was an octopus cell. The second cell, located in the octopus-cell area, was a giant cell with a few somatic spines and thin tapering dendrites; the intracellular record revealed that even in the absence of sound it received continuous synaptic input, while tones at characteristic frequency produced a sustained depolarization. A third cell, which had an onset response at low intensities and a chopper response at high intensities, was a stellate cell located in the intermediate acoustic stria with dendrites oriented parallel to the fiber tract. This cell had an unusually broad dynamic range in response to changes in intensity. Two cells with transient chopper response patterns were stellate cells in the posteroventral cochlear nucleus with many branched and beaded dendrites. Three cells with more sustained chopper response patterns were stellate cells in the anteroventral cochlear nucleus with fewer, less-branched, smooth dendrites. Two cells with primarylike responses to tones were bushy cells with numerous short, thin, highly branched dendrites in the posterior division of the anteroventral cochlear nucleus. Intracellular responses to tones at the characteristic frequency consisted of large brief depolarizations, which were not sustained. Another cell, which responded to tones in a phase-locked fashion, was also located in the anteroventral cochlear nucleus. It was a small, stellate cell with relatively few, smooth dendrites. The labeled cells largely support previous attempts at physiological-morphological correlations: (1) bushy cells exhibit primarylike pattern; (2) stellate cells exhibit chopper patterns; and (3) octopus cells exhibit an onset pattern. It was also demonstrated that more than one cell type can exhibit a particular response pattern.

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