scholarly journals Heterogeneous Biophysical Properties of Frog Dorsal Medullary Nucleus (Cochlear Nucleus) Neurons

2007 ◽  
Vol 98 (4) ◽  
pp. 1953-1964 ◽  
Author(s):  
Sungchil Yang ◽  
Albert S. Feng
Keyword(s):  
Cochlear Nucleus ◽  
Cell Types ◽  
Biophysical Properties ◽  
Leopard Frogs ◽  
Distinct Evolutionary Lineage ◽  
Dorsal Medullary Nucleus ◽  
Temporal Firing ◽  
Rana Pipiens Pipiens ◽  
Discharge Patterns ◽  
Northern Leopard Frogs

The cochlear nucleus (CN) in mammals, or its counterpart in birds, has multiple subdivisions each containing distinct morphological and functional (i.e., temporal discharge patterns and biophysical properties) cell types that project to different auditory nuclei in the brain stem in parallel. The analogous structure in frogs, the dorsal medullary nucleus (DMN), is a single phylogenetically older structure with no subdivision. Similar to the CN, the DMN has complex cytoarchitecture and contains neurons with diverse morphological phenotypes, but whether these cell types possess distinct biophysical characteristics, like their counterparts in mammals and avians, is unclear. Here we show that DMN neurons in young adult northern leopard frogs ( Rana pipiens pipiens) possess heterogeneous biophysical properties. There are four major biophysical phenotypes on the basis of the unit's response (i.e., its temporal firing pattern) to depolarizing currents: onset, phasic-burst, sustained-chopper, and adapting. These cells have distinct membrane input resistances and time constants, spike shapes, current-voltage relationships, first-spike latencies, entrainment characteristics, and ionic compositions (i.e., low-threshold potassium current, Ikl, and hyperpolarization-activated current, Ih). Furthermore, these phenotypes correspond to cells' dendritic morphologies, and they bear similarities and differences to those found in the mammalian CN. The similarities are remarkable considering that amphibians are a distinct evolutionary lineage from birds and mammals.

Kinetic Analyses of Three Distinct Potassium Conductances in Ventral Cochlear Nucleus Neurons

2003 ◽  
Vol 89 (6) ◽  
pp. 3083-3096 ◽  
Author(s):  
Jason S. Rothman ◽  
Paul B. Manis
Keyword(s):  
Fourth Order ◽  
Cochlear Nucleus ◽  
Cell Types ◽  
High Threshold ◽  
Ventral Cochlear Nucleus ◽  
First Order Kinetics ◽  
Recovery From Inactivation ◽  
Potassium Conductances ◽  
Voltage Dependent ◽  
Discharge Patterns

Neurons in the ventral cochlear nucleus (VCN) express three distinct K+ currents that differ in their voltage and time dependence, and in their inactivation behavior. In the present study, we quantitatively analyze the voltage-dependent kinetics of these three currents to gain further insight into how they regulate the discharge patterns of VCN neurons and to provide supporting data for the identification of their channel components. We find the transient A-type K+ current ( IA) exhibits fourth-order activation kinetics ( a4), and inactivates with one or two time constants. A second inactivation rate (leading to an a4 bc kinetic description) is required to explain its recovery from inactivation. The dendrotoxin-sensitive low-threshold K+ current ( ILT) also activates with fourth-order kinetics ( w4) but shows slower, incomplete inactivation. The high-threshold K+ current ( IHT) appears to consist of two kinetically distinct components ( n2 + p). The first component activates ∼10 mV positive to the second and has second-order kinetics. The second component activates with first-order kinetics. These two components also contribute to two kinetically distinct currents upon deactivation. The kinetic behavior of IHT was indistinguishable amongst cell types, suggesting the current is mediated by the same K+ channels amongst VCN neurons. Together these results provide a basis for more realistic modeling of VCN neurons, and provide clues regarding the molecular basis of the three K+ currents.

Oncogenesis and the Lucké Virus

1968 ◽  
Vol 26 ◽  
pp. 200-201
Author(s):  
A. E. Vatter ◽  
J. Zambernard
Keyword(s):  
Rna Viruses ◽  
Vegetative State ◽  
Temperature Sensitive ◽  
Structural Level ◽  
Oncogenic Viruses ◽  
Dna Viruses ◽  
Leopard Frogs ◽  
Renal Adenocarcinoma ◽  
Induced Tumors ◽  
Northern Leopard Frogs

Oncogenic viruses, like viruses in general, can be divided into two classes, those that contain deoxyribonucleic acid (DNA) and those that contain ribonucleic acid (RNA). The RNA viruses have been recovered readily from the tumors which they cause whereas, the DNA-virus induced tumors have not yielded the virus. Since DNA viruses cannot be recovered, the bulk of present day investigations have been concerned with RNA viruses.The Lucké renal adenocarcinoma is a spontaneous tumor which occurs in northern leopard frogs (Rana pipiens) and has received increased attention in recent years because of its probable viral etiology. This hypothesis was first advanced by Lucké after he observed intranuclear inclusions in some of the tumor cells. Tumors with inclusions were examined at the fine structural level by Fawcett who showed that they contained immature and mature virus˗like particles.The use of this system in the study of oncogenic tumors offers several unique features, the virus has been shown to contain DNA and it can be recovered from the tumor, also, it is temperature sensitive. This latter feature is of importance because the virus can be transformed from a latent to a vegetative state by lowering or elevating the environmental temperature.

The Roles Potassium Currents Play in Regulating the Electrical Activity of Ventral Cochlear Nucleus Neurons

2003 ◽  
Vol 89 (6) ◽  
pp. 3097-3113 ◽  
Author(s):  
Jason S. Rothman ◽  
Paul B. Manis
Keyword(s):  
Cochlear Nucleus ◽  
Auditory Nerve ◽  
Threshold Current ◽  
Repetitive Firing ◽  
Resting Membrane Potential ◽  
Type I ◽  
Type Ii Cells ◽  
Type Ii ◽  
Ventral Cochlear Nucleus ◽  
Discharge Patterns

Using kinetic data from three different K+ currents in acutely isolated neurons, a single electrical compartment representing the soma of a ventral cochlear nucleus (VCN) neuron was created. The K+ currents include a fast transient current ( IA), a slow-inactivating low-threshold current ( ILT), and a noninactivating high-threshold current ( IHT). The model also includes a fast-inactivating Na+ current, a hyperpolarization-activated cation current ( Ih), and 1–50 auditory nerve synapses. With this model, the role IA, ILT, and IHT play in shaping the discharge patterns of VCN cells is explored. Simulation results indicate that IHT mainly functions to repolarize the membrane during an action potential, and IA functions to modulate the rate of repetitive firing. ILT is found to be responsible for the phasic discharge pattern observed in Type II cells (bushy cells). However, by adjusting the strength of ILT, both phasic and regular discharge patterns are observed, demonstrating that a critical level of ILT is necessary to produce the Type II response. Simulated Type II cells have a significantly faster membrane time constant in comparison to Type I cells (stellate cells) and are therefore better suited to preserve temporal information in their auditory nerve inputs by acting as precise coincidence detectors and having a short refractory period. Finally, we demonstrate that modulation of Ih, which changes the resting membrane potential, is a more effective means of modulating the activation level of ILT than simply modulating ILT itself. This result may explain why ILT and Ih are often coexpressed throughout the nervous system.

Encoding timing and intensity in the ventral cochlear nucleus of the cat

1986 ◽  
Vol 56 (2) ◽  
pp. 261-286 ◽  
Author(s):  
W. S. Rhode ◽  
P. H. Smith
Keyword(s):  
Firing Rate ◽  
Cochlear Nucleus ◽  
Auditory Nerve ◽  
Cell Types ◽  
Nerve Fibers ◽  
Frequency Selectivity ◽  
Firing Rates ◽  
Ventral Cochlear Nucleus ◽  
Auditory Nerve Fibers ◽  
Different Cell Types

Physiological response properties of neurons in the ventral cochlear nucleus have a variety of features that are substantially different from the stereotypical auditory nerve responses that serve as the principal source of activation for these neurons. These emergent features are the result of the varying distribution of auditory nerve inputs on the soma and dendrites of the various cell types within the nucleus; the intrinsic membrane characteristics of the various cell types causing different responses to the same input in different cell types; and secondary excitatory and inhibitory inputs to different cell types. Well-isolated units were recorded with high-impedance glass microelectrodes, both intracellularly and extracellularly. Units were characterized by their temporal response to short tones, rate vs. intensity relation, and response areas. The principal response patterns were onset, chopper, and primary-like. Onset units are characterized by a well-timed first spike in response to tones at the characteristic frequency. For frequencies less than 1 kHz, onset units can entrain to the stimulus frequency with greater precision than their auditory nerve inputs. This implies that onset units receive converging inputs from a number of auditory nerve fibers. Onset units are divided into three subcategories, OC, OL, and OI. OC units have extraordinarily wide dynamic ranges and low-frequency selectivity. Some are capable of sustaining firing rates of 800 spikes/s at high intensities. They have the smallest standard deviation and coefficient of variation of the first spike latency of any cells in the cochlear nuclei. OC units are candidates for encoding intensity. OI and OL units differ from OC units in that they have dynamic ranges and frequency selectivity ranges much like those of auditory nerve fibers. They differ from one another in their steady-state firing rates; OI units fire mainly at the onset of a tone. OI units also differ from OL units in that they prefer frequency sweeps in the low to high direction. Primary-like-with-notch (PLN) units also respond to tones with a well-timed first spike. They differ from onset cells in that the onset peak is not always as precise as the spontaneous rate is higher. A comparison of spontaneous firing rate and saturation firing rate of PLN units with auditory nerve fibers suggest that PLN units receive one to four auditory nerve fiber inputs. Chopper units fire in a sustained regular manner when they are excited by sound.(ABSTRACT TRUNCATED AT 400 WORDS)

Modelling the sensitivity of cells in the anteroventral cochlear nucleus to spatiotemporal discharge patterns

1992 ◽  
Vol 336 (1278) ◽  
pp. 403-406 ◽  
Keyword(s):  
Cochlear Nucleus ◽  
Auditory Nerve ◽  
Cross Correlation ◽  
Low Frequency ◽  
Phase Spectrum ◽  
Coincidence Detection ◽  
Potential Mechanism ◽  
Complex Sounds ◽  
Anteroventral Cochlear Nucleus ◽  
Discharge Patterns

This study investigates a potential mechanism for the processing of acoustic information that is encoded in the spatiotemporal discharge patterns of auditory nerve (AN) fibres. Recent physiological evidence has demonstrated that some low-frequency cells in the anteroventral cochlear nucleus (AVCN) are sensitive to manipulations of the phase spectrum of complex sounds (Carney 1990 b ). These manipulations result in systematic changes in the spatiotemporal discharge patterns across groups of low-frequency an fibres having different characteristic frequencies (CFS). One interpretation of these results is that these neurons in the AVCN receive convergent inputs from AN fibres with different CFS, and that the cells perform a coincidence detection or cross-correlation upon their inputs. This report presents a model that was developed to test this interpretation.

scholarly journals Effect of glucocorticoids on expression of cutaneous antimicrobial peptides in northern leopard frogs (Lithobates pipiens)

2015 ◽  
Vol 11 (1) ◽  
Author(s):  
Laetitia Tatiersky ◽  
Louise A. Rollins-Smith ◽  
Ray Lu ◽  
Claire Jardine ◽  
Ian K. Barker ◽  
...  
Keyword(s):  
Antimicrobial Peptides ◽  
Lithobates Pipiens ◽  
Leopard Frogs ◽  
Northern Leopard Frogs

Development and Survivorship of Northern Leopard Frogs (Rana pipiens) and Green Frogs (Rana clamitans) Exposed to Contaminants in the Water and Sediments of the St. Lawrence River near Cornwall, Ontario

2004 ◽  
Vol 39 (3) ◽  
pp. 160-174 ◽  
Author(s):  
Tana V. McDaniel ◽  
Megan L. Harris ◽  
Christine A. Bishop ◽  
John Struger
Keyword(s):  
Rana Pipiens ◽  
Early Stage ◽  
Sediment Quality ◽  
Leopard Frog ◽  
Reference Sites ◽  
Aquatic Life ◽  
Leopard Frogs ◽  
Water And Sediment ◽  
Northern Leopard Frogs ◽  
St Lawrence River

Abstract High levels of contamination in the aquatic environment and wildlife within the Ontario portion of the St. Lawrence River at the Cornwall Area of Concern (AOC) have raised questions about potential impacts on wildlife health. Northern leopard frog embryos were raised in two wetland sites within the AOC and at two reference sites to assess differences in water and sediment quality on survivorship and deformity rates. Chlorinated hydrocarbons (total polychlorinated biphenyls, organochlorine pesticides), polycyclic aromatic hydrocarbons, nutrients and heavy metals were measured in sediment and/or water from the study sites. Levels of some metals such as aluminium, cadmium, chromium and copper, exceeded federal and provincial guidelines for the protection of aquatic life, especially in the two AOC wetlands. Early stage tadpole survivorship was significantly lower and deformity frequency significantly higher at wetlands within the AOC; however, differences were likely not biologically significant. Survivorship and deformity rates of leopard frogs (Rana pipiens) at metamorphosis did not differ significantly among sites. Onset of metamorphosis was accelerated in tadpoles raised in wetlands within the AOC. Tadpoles raised in wetlands within the St. Lawrence River AOC took significantly less time to complete metamorphosis (53–55 days) than did tadpoles raised at reference sites (61–64 days). The phenology of metamorphosis was also more synchronous in tadpoles raised in the AOC, with all tadpoles reaching metamorphosis within a space of 3 to 7 days, as compared to 9 to 12 days at reference wetlands; these differences could not be accounted for by water temperature. Differences in development and survivorship rates between AOC and reference sites may be related to contaminant concentrations in water and sediment. However, no strong evidence for beneficial use impairment in terms of reproductive impairments or elevated deformity rates were seen from caged leopard frogs in the two AOC wetlands.

Sign in / Sign up

Export Citation Format

Share Document