scholarly journals Functional Role of GABAergic and Glycinergic Inhibition in the Intermediate Nucleus of the Lateral Lemniscus of the Big Brown Bat

2009 ◽  
Vol 101 (6) ◽  
pp. 3135-3146 ◽  
Author(s):  
Andrew Kutscher ◽  
Ellen Covey
Keyword(s):  
Gain Control ◽  
Stimulus Onset ◽  
Auditory Information ◽  
Lateral Lemniscus ◽  
Intermediate Nucleus ◽  
Medial Nucleus ◽  
Big Brown Bat ◽  
Glycinergic Inhibition

The intermediate nucleus of the lateral lemniscus (INLL) is a major input to the inferior colliculus (IC), the auditory midbrain center where multiple pathways converge to create neurons selective for specific temporal features of sound. However, little is known about how INLL processes auditory information or how it contributes to integrative processes at the IC. INLL receives excitatory projections from the cochlear nucleus and inhibitory projections from the medial nucleus of the trapezoid body (MNTB), so it must perform some form of integration. To address the question of what role inhibitory synaptic inputs play in the INLL of the big brown bat ( Eptesicus fuscus), we recorded sound-evoked responses of single neurons and iontophoretically applied bicuculline to block GABAA receptors or strychnine to block glycine receptors. Neither bicuculline nor strychnine had a consistent effect on response latency or frequency response areas. Bicuculline increased spike counts and response durations in most units, suggesting that GABAergic input suppressed the late part of the response and provided some gain control. Strychnine reduced the responses of some units with sustained discharge patterns to one or a few spikes at stimulus onset, but increased others. INLL is the only part of the auditory system where reduced responsiveness has been seen in vivo while blocking glycine. However, in vitro studies in the MNTB suggest that glycine can be facilitatory, possibly through presynaptic action. These results show that GABA consistently reduces spike counts and response durations, whereas glycine is suppressive in some INLL neurons but facilitatory in others.

scholarly journals GABAergic and glycinergic inhibition modulate monaural auditory response properties in the avian superior olivary nucleus

2011 ◽  
Vol 105 (5) ◽  
pp. 2405-2420 ◽  
Author(s):  
W. L. Coleman ◽  
M. J. Fischl ◽  
S. R. Weimann ◽  
R. M. Burger
Keyword(s):  
Phase Locking ◽  
Auditory Brainstem ◽  
Inhibitory Input ◽  
Auditory Information ◽  
Low Frequencies ◽  
Response Properties ◽  
Glycinergic Inhibition ◽  
Olivary Nucleus

The superior olivary nucleus (SON) is the primary source of inhibition in the avian auditory brainstem. While much is known about the role of inhibition at the SON's target nuclei, little is known about how the SON itself processes auditory information or how inhibition modulates these properties. Additionally, the synaptic physiology of inhibitory inputs within the SON has not been described. We investigated these questions using in vivo and in vitro electrophysiological techniques in combination with immunohistochemistry in the chicken, an organism for which the auditory brainstem has otherwise been well characterized. We provide a thorough characterization of monaural response properties in the SON and the influence of inhibitory input in shaping these features. We found that the SON contains a heterogeneous mixture of response patterns to acoustic stimulation and that in most neurons these responses are modulated by both GABAergic and glycinergic inhibitory inputs. Interestingly, many SON neurons tuned to low frequencies have robust phase-locking capability and the precision of this phase locking is enhanced by inhibitory inputs. On the synaptic level, we found that evoked and spontaneous inhibitory postsynaptic currents (IPSCs) within the SON are also mediated by both GABAergic and glycinergic inhibition in all neurons tested. Analysis of spontaneous IPSCs suggests that most SON cells receive a mixture of both purely GABAergic terminals, as well as terminals from which GABA and glycine are coreleased. Evidence for glycinergic signaling within the SON is a novel result that has important implications for understanding inhibitory function in the auditory brainstem.

scholarly journals Glycinergic inhibition to the medial nucleus of the trapezoid body shows prominent facilitation and can sustain high levels of ongoing activity

2014 ◽  
Vol 112 (11) ◽  
pp. 2901-2915 ◽  
Author(s):  
Florian Mayer ◽  
Otto Albrecht ◽  
Anna Dondzillo ◽  
Achim Klug
Keyword(s):  
Meriones Unguiculatus ◽  
Inhibitory Synapses ◽  
Auditory Information ◽  
Activity Levels ◽  
Synaptic Currents ◽  
Medial Nucleus ◽  
Highly Active ◽  
Glycinergic Inhibition ◽  
Trapezoid Body

Neurons in the medial nucleus of the trapezoid body (MNTB) are well known for their prominent excitatory inputs, mediated by the calyx of Held. Less attention has been paid to the prominent inhibitory inputs that MNTB neurons also receive. Because of their auditory nature, both excitatory and inhibitory synapses are highly active in vivo. These high levels of activity are known to reduce excitatory synaptic currents considerably, such that in vivo synaptic currents produced by the calyx are smaller than typically measured in standard brain slice experiments. The goal of this study was to investigate the properties of the inhibitory inputs in the Mongolian gerbil ( Meriones unguiculatus) under activity levels that correspond to those in the intact brain to facilitate a direct comparison between the two inputs. Our results suggest that inhibitory inputs to MNTB are largely mediated by a fast and phasic glycinergic component, and to a lesser degree by a GABAergic component. The glycinergic component can sustain prolonged high levels of activity. Even when challenged with stimulus patterns consisting of thousands of stimuli over tens of minutes, glycinergic inputs to MNTB maintain large conductances and fast decays and even facilitate substantially when the stimulation frequency is increased. The inhibition is mediated by a relatively small number of independent input fibers. The data presented here suggest that inhibitory inputs to MNTB sustain high levels of activity and need to be considered for a full understanding of mechanisms underlying processing of auditory information in MNTB.

scholarly journals A novel transdermal nanoethosomal gel of betahistine dihydrochloride for weight gain control: in-vitro and in-vivo characterization

2017 ◽  
Vol Volume 11 ◽  
pp. 3377-3388 ◽  
Author(s):  
Shahira El- Menshawe ◽  
Adel Ahmed Ali ◽  
Abdelkhalk Ali Halawa ◽  
Ahmed S.G. Srag El-Din
Keyword(s):  
Weight Gain ◽  
Gain Control ◽  
Betahistine Dihydrochloride ◽  
In Vivo Characterization

scholarly journals How to build a fast and highly sensitive sound detector that remains robust to temperature shifts

2019 ◽  
Author(s):  
Minghui Chen ◽  
Henrique von Gersdorff
Keyword(s):  
Hair Cell ◽  
Hair Cells ◽  
Auditory Information ◽  
Temperature Changes ◽  
Temporal Precision ◽  
Auditory Nerves ◽  
Afferent Fibers ◽  
Vesicle Exocytosis

AbstractFrogs must have sharp hearing abilities during the warm summer months to successfully find mating partners. This study aims to understand how frog hair cell ribbon-type synapses preserve both sensitivity and temporal precision during temperature changes. We performedin vitropatch-clamp recordings of hair cells and their afferent fibers in bullfrog amphibian papillae under room (23-25°C) and high (30-33°C) temperature. Afferent fibers exhibited a wide heterogeneity in membrane input resistance (Rin) from 100 MΩ to 1000 MΩ, which may contribute to variations in spike threshold and firing frequency. At higher temperatures, most fibers increased their frequency of action potential firing due to an increase in spontaneous EPSC frequencies. Hair cell resting membrane potential (Vrest) remained surprisingly stable during temperature increases, although both inward Ca2+current and outward K+current increased in amplitude. This increase in Ca2+current may explain the higher spontaneous EPSC frequencies. The larger “leak currents” at Vrestlowered Rinand produced higher electrical resonant frequencies. However, lower Rinshould decrease sensitivity to sound detection via smaller receptor potentials. Using membrane capacitance measurements, we suggest that hair cells can partially compensate for this reduced sensitivity by increasing exocytosis efficiency and the size of the readily releasable pool of synaptic vesicles. Furthermore, paired recordings of hair cells and their afferent fibers showed that synaptic delays become shorter and multivesicular release becomes more synchronous at higher temperatures, which should improve temporal precision. Altogether, our results explain many previousin vivoobservations on the temperature dependence of spikes in auditory nerves.Significance StatementThe vertebrate inner ear detects and transmits auditory information over a broad dynamic range of sound frequency and intensity. It achieves remarkable sensitivity to soft sounds and precise frequency selectivity. How does the ear of cold-blooded vertebrates maintain its performance level as temperature changes? More specifically, how does the hair cell to afferent fiber synapse in bullfrog amphibian papilla adjust to a wide range of physiological temperatures without losing its sensitivity and temporal fidelity to sound signals? This study usesin vitroexperiments to reveal the biophysical mechanisms that explain many observations made fromin vivoauditory nerve fiber recordings. We find that higher temperature facilitates vesicle exocytosis and electrical tuning to higher sound frequencies, which benefits sensitivity and selectivity.

scholarly journals Differentially synchronized spiking enables multiplexed neural coding

2019 ◽  
Vol 116 (20) ◽  
pp. 10097-10102 ◽  
Author(s):  
Milad Lankarany ◽  
Dhekra Al-Basha ◽  
Stéphanie Ratté ◽  
Steven A. Prescott
Keyword(s):  
Neural Coding ◽  
Tactile Stimulation ◽  
Stimulus Onset ◽  
Natural Scenes ◽  
Common Input ◽  
Low Contrast ◽  
Intensity Changes ◽  
Stimulus Features

Multiplexing refers to the simultaneous encoding of two or more signals. Neurons have been shown to multiplex, but different stimuli require different multiplexing strategies. Whereas the frequency and amplitude of periodic stimuli can be encoded by the timing and rate of the same spikes, natural scenes, which comprise areas over which intensity varies gradually and sparse edges where intensity changes abruptly, require a different multiplexing strategy. Recording in vivo from neurons in primary somatosensory cortex during tactile stimulation, we found that stimulus onset and offset (edges) evoked highly synchronized spiking, whereas other spikes in the same neurons occurred asynchronously. Stimulus intensity modulated the rate of asynchronous spiking, but did not affect the timing of synchronous spikes. From this, we hypothesized that spikes driven by high- and low-contrast stimulus features can be distinguished on the basis of their synchronization, and that differentially synchronized spiking can thus be used to form multiplexed representations. Applying a Bayesian decoding method, we verified that information about high- and low-contrast features can be recovered from an ensemble of model neurons receiving common input. Equally good decoding was achieved by distinguishing synchronous from asynchronous spikes and applying reverse correlation methods separately to each spike type. This result, which we verified with patch clamp recordings in vitro, demonstrates that neurons receiving common input can use the rate of asynchronous spiking to encode the intensity of low-contrast features while using the timing of synchronous spikes to encode the occurrence of high-contrast features. We refer to this strategy as synchrony-division multiplexing.

Induction and Differentiation of Dental Epithelium in Vivo and in Vitro

1982 ◽  
Vol 40 ◽  
pp. 142-145
Author(s):  
E. J. Kollar
Keyword(s):  
Connective Tissue ◽  
Oral Mucosa ◽  
Basal Lamina ◽  
Functional Derivatives ◽  
Specific Source ◽  
Dental Epithelium ◽  
Connective Tissue Stroma

The differentiation and maintenance of many specialized epithelial structures are dependent on the underlying connective tissue stroma and on an intact basal lamina. These requirements are especially stringent in the development and maintenance of the skin and oral mucosa. The keratinization patterns of thin or thick cornified layers as well as the appearance of specialized functional derivatives such as hair and teeth can be correlated with the specific source of stroma which supports these differentiated expressions.

Ultrastructural Correlations between Clonal Human Tumor Colonies and in Vivo Neoplasms

1982 ◽  
Vol 40 ◽  
pp. 210-211
Author(s):  
M.J. Murphy ◽  
R.R. Price ◽  
J.C. Sloman
Keyword(s):  
Cultured Cells ◽  
Human Tumor ◽  
Cell Type ◽  
Tumor Mass ◽  
Initial Cell ◽  
Cloning Assay ◽  
Human Tumor Cloning ◽  
The Relationship

The in vitro human tumor cloning assay originally described by Salmon and Hamburger has been applied recently to the investigation of differential anti-tumor drug sensitivities over a broad range of human neoplasms. A major problem in the acceptance of this technique has been the question of the relationship between the cultured cells and the original patient tumor, i.e., whether the colonies that develop derive from the neoplasm or from some other cell type within the initial cell population. A study of the ultrastructural morphology of the cultured cells vs. patient tumor has therefore been undertaken to resolve this question. Direct correlation was assured by division of a common tumor mass at surgical resection, one biopsy being fixed for TEM studies, the second being rapidly transported to the laboratory for culture.

Ultrastructure of melanocyte-keratinocyte interactions and pigment transfer in vitro

1978 ◽  
Vol 36 (2) ◽  
pp. 650-651
Author(s):  
Raul I. Garcia ◽  
Evelyn A. Flynn ◽  
George Szabo
Keyword(s):  
Direct Injection ◽  
Skin Pigmentation ◽  
Freeze Fracture ◽  
Pigment Granule ◽  
Time Lapse ◽  
Ultrastructural Level ◽  
Lanthanum Tracer ◽  
A Cell

Skin pigmentation in mammals involves the interaction of epidermal melanocytes and keratinocytes in the structural and functional unit known as the Epidermal Melanin Unit. Melanocytes(M) synthesize melanin within specialized membrane-bound organelles, the melanosome or pigment granule. These are subsequently transferred by way of M dendrites to keratinocytes(K) by a mechanism still to be clearly defined. Three different, though not necessarily mutually exclusive, mechanisms of melanosome transfer have been proposed: cytophagocytosis by K of M dendrite tips containing melanosomes, direct injection of melanosomes into the K cytoplasm through a cell-to-cell pore or communicating channel formed by localized fusion of M and K cell membranes, release of melanosomes into the extracellular space(ECS) by exocytosis followed by K uptake using conventional phagocytosis. Variability in methods of transfer has been noted both in vivo and in vitro and there is evidence in support of each transfer mechanism. We Have previously studied M-K interactions in vitro using time-lapse cinemicrography and in vivo at the ultrastructural level using lanthanum tracer and freeze-fracture.

In vitro and in vivo polysaccharides assembly: ultrastructural and cytochemical study of growing plant cell wall components.

1978 ◽  
Vol 36 (2) ◽  
pp. 434-435
Author(s):  
D. Reis ◽  
B. Vian ◽  
J. C. Roland
Keyword(s):  
Cell Wall ◽  
Self Assembly ◽  
Plant Cell Wall ◽  
Higher Plants ◽  
Three Dimensional ◽  
Cytochemical Study ◽  
Wall Components

Wall morphogenesis in higher plants is a problem still open to controversy. Until now the possibility of a transmembrane control and the involvement of microtubules were mostly envisaged. Self-assembly processes have been observed in the case of walls of Chlamydomonas and bacteria. Spontaneous gelling interactions between xanthan and galactomannan from Ceratonia have been analyzed very recently. The present work provides indications that some processes of spontaneous aggregation could occur in higher plants during the formation and expansion of cell wall.Observations were performed on hypocotyl of mung bean (Phaseolus aureus) for which growth characteristics and wall composition have been previously defined.In situ, the walls of actively growing cells (primary walls) show an ordered three-dimensional organization (fig. 1). The wall is typically polylamellate with multifibrillar layers alternately transverse and longitudinal. Between these layers intermediate strata exist in which the orientation of microfibrils progressively rotates. Thus a progressive change in the morphogenetic activity occurs.

Probing the ultrastructure of the mitotic and meiotic spindle in eggs: An expeditious approach based on semi-thin (0.25 μm) serial sections

1983 ◽  
Vol 41 ◽  
pp. 552-555
Author(s):  
Conly L. Rieder ◽  
S. Bowser ◽  
R. Nowogrodzki ◽  
K. Ross ◽  
G. Sluder
Keyword(s):  
Small Sample Size ◽  
Small Sample ◽  
Meiotic Spindle ◽  
Serial Sections ◽  
Mitotic Apparatus ◽  
Thin Sections ◽  
Cell Cycles ◽  
Ultrastructural Studies

Eggs have long been a favorite material for studying the mechanism of karyokinesis in-vivo and in-vitro. They can be obtained in great numbers and, when fertilized, divide synchronously over many cell cycles. However, they are not considered to be a practical system for ultrastructural studies on the mitotic apparatus (MA) for several reasons, the most obvious of which is that sectioning them is a formidable task: over 1000 ultra-thin sections need to be cut from a single 80-100 μm diameter egg and of these sections only a small percentage will contain the area or structure of interest. Thus it is difficult and time consuming to obtain reliable ultrastructural data concerning the MA of eggs; and when it is obtained it is necessarily based on a small sample size.We have recently developed a procedure which will facilitate many studies concerned with the ultrastructure of the MA in eggs. It is based on the availability of biological HVEM's and on the observation that 0.25 μm thick serial sections can be screened at high resolution for content (after mounting on slot grids and staining with uranyl and lead) by phase contrast light microscopy (LM; Figs 1-2).

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