scholarly journals Active dendrites enable strong but sparse inputs to determine orientation selectivity

2021 ◽  
Vol 118 (30) ◽  
pp. e2017339118
Author(s):  
Lea Goetz ◽  
Arnd Roth ◽  
Michael Häusser
Keyword(s):  
Action Potential ◽  
Pyramidal Neurons ◽  
Potential Output ◽  
Synaptic Inputs ◽  
Active Dendrites ◽  
Strongly Connected ◽  
Dendritic Spikes ◽  
Sensory Responses

The dendrites of neocortical pyramidal neurons are excitable. However, it is unknown how synaptic inputs engage nonlinear dendritic mechanisms during sensory processing in vivo, and how they in turn influence action potential output. Here, we provide a quantitative account of the relationship between synaptic inputs, nonlinear dendritic events, and action potential output. We developed a detailed pyramidal neuron model constrained by in vivo dendritic recordings. We drive this model with realistic input patterns constrained by sensory responses measured in vivo and connectivity measured in vitro. We show mechanistically that under realistic conditions, dendritic Na+ and NMDA spikes are the major determinants of neuronal output in vivo. We demonstrate that these dendritic spikes can be triggered by a surprisingly small number of strong synaptic inputs, in some cases even by single synapses. We predict that dendritic excitability allows the 1% strongest synaptic inputs of a neuron to control the tuning of its output. Active dendrites therefore allow smaller subcircuits consisting of only a few strongly connected neurons to achieve selectivity for specific sensory features.

scholarly journals Aloe-Emodin Relieves High-Fat Diet Induced QT Prolongation via MiR-1 Inhibition and IK1 Up-Regulation in Rats

2017 ◽  
Vol 43 (5) ◽  
pp. 1961-1973 ◽  
Author(s):  
Yan Bai ◽  
Zhenli Su ◽  
Hanqi Sun ◽  
Wei Zhao ◽  
Xue Chen ◽  
...  
Keyword(s):  
Action Potential ◽  
Protein Expression ◽  
High Fat Diet ◽  
Qt Prolongation ◽  
Electrical Remodeling ◽  
High Fat ◽  
Treatment Groups ◽  
Aloe Emodin

Background/Aims: High-fat diet (HFD) causes cardiac electrical remodeling and increases the risk of ventricular arrhythmias. Aloe-emodin (AE) is an anthraquinone component isolated from rhubarb and has a similar chemical structure with emodin. The protective effect of emodin against cardiac diseases has been reported in the literature. However, the cardioprotective property of AE is still unknown. The present study investigated the effect of AE on HFD-induced QT prolongation in rats. Methods: Adult male Wistar rats were randomly divided into three groups: control, HFD, and AE-treatment groups. Normal diet was given to rats in the control group, high-fat diet was given to rats in HFD and AE-treatment groups for a total of 10 weeks. First, HFD rats and AE-treatment rats were fed with high-fat diet for 4 weeks to establish the HFD model. Serum total cholesterol and triglyceride levels were measured to validate the HFD model. Afterward, AE-treatment rats were intragastrically administered with 100 mg/kg AE each day for 6 weeks. Electrocardiogram monitoring and whole-cell patch-clamp technique were applied to examine cardiac electrical activity, action potential and inward rectifier K+ current (IK1), respectively. Neonatal rat ventricular myocytes (NRVMs) were subjected to cholesterol and/or AE. Protein expression of Kir2.1 was detected by Western blot and miR-1 level was examined by real-time PCR in vivo and in vitro, respectively. Results: In vivo, AE significantly shortened the QT interval, action potential duration at 90% repolarization (APD90) and resting membrane potential (RMP), which were markedly elongated by HFD. AE increased IK1 current and Kir2.1 protein expression which were reduced in HFD rats. Furthermore, AE significantly inhibited pro-arrhythmic miR-1 in the hearts of HFD rats. In vitro, AE decreased miR-1 expression levels resulting in an increase of Kir2.1 protein levels in cholesterol-enriched NRVMs. Conclusions: AE prevents HFD-induced QT prolongation by repressing miR-1 and upregulating its target Kir2.1. These findings suggest a novel pharmacological role of AE in HFD-induced cardiac electrical remodeling.

scholarly journals The thalamic low-threshold Ca 2+ potential: a key determinant of the local and global dynamics of the slow (<1 Hz) sleep oscillation in thalamocortical networks

2011 ◽  
Vol 369 (1952) ◽  
pp. 3820-3839 ◽  
Author(s):  
Vincenzo Crunelli ◽  
Adam C. Errington ◽  
Stuart W. Hughes ◽  
Tibor I. Tóth
Keyword(s):  
Action Potential ◽  
Slow Oscillation ◽  
Global Dynamics ◽  
Action Potential Firing ◽  
Local And Global Dynamics ◽  
Up States ◽  
Potential Firing ◽  
Low Threshold

During non-rapid eye movement sleep and certain types of anaesthesia, neurons in the neocortex and thalamus exhibit a distinctive slow (<1 Hz) oscillation that consists of alternating UP and DOWN membrane potential states and which correlates with a pronounced slow (<1 Hz) rhythm in the electroencephalogram. While several studies have claimed that the slow oscillation is generated exclusively in neocortical networks and then transmitted to other brain areas, substantial evidence exists to suggest that the full expression of the slow oscillation in an intact thalamocortical (TC) network requires the balanced interaction of oscillator systems in both the neocortex and thalamus. Within such a scenario, we have previously argued that the powerful low-threshold Ca 2+ potential (LTCP)-mediated burst of action potentials that initiates the UP states in individual TC neurons may be a vital signal for instigating UP states in related cortical areas. To investigate these issues we constructed a computational model of the TC network which encompasses the important known aspects of the slow oscillation that have been garnered from earlier in vivo and in vitro experiments. Using this model we confirm that the overall expression of the slow oscillation is intricately reliant on intact connections between the thalamus and the cortex. In particular, we demonstrate that UP state-related LTCP-mediated bursts in TC neurons are proficient in triggering synchronous UP states in cortical networks, thereby bringing about a synchronous slow oscillation in the whole network. The importance of LTCP-mediated action potential bursts in the slow oscillation is also underlined by the observation that their associated dendritic Ca 2+ signals are the only ones that inform corticothalamic synapses of the TC neuron output, since they, but not those elicited by tonic action potential firing, reach the distal dendritic sites where these synapses are located.

Effect of Common Anesthetics on Dendritic Properties in Layer 5 Neocortical Pyramidal Neurons

2008 ◽  
Vol 99 (3) ◽  
pp. 1394-1407 ◽  
Author(s):  
Sarah Potez ◽  
Matthew E. Larkum
Keyword(s):  
High Frequency ◽  
Pyramidal Neurons ◽  
Animal Experiments ◽  
Apical Dendrite ◽  
Network Activity ◽  
Calcium Spikes ◽  
Firing Properties ◽  
The Impact

Understanding the impact of active dendritic properties on network activity in vivo has so far been restricted to studies in anesthetized animals. However, to date no study has been made to determine the direct effect of the anesthetics themselves on dendritic properties. Here, we investigated the effects of three types of anesthetics commonly used for animal experiments (urethane, pentobarbital and ketamine/xylazine). We investigated the generation of calcium spikes, the propagation of action potentials (APs) along the apical dendrite and the somatic firing properties in the presence of anesthetics in vitro using dual somatodendritic whole cell recordings. Calcium spikes were evoked with dendritic current injection and high-frequency trains of APs at the soma. Surprisingly, we found that the direct actions of anesthetics on calcium spikes were very different. Two anesthetics (urethane and pentobarbital) suppressed dendritic calcium spikes in vitro, whereas a mixture of ketamine and xylazine enhanced them. Propagation of spikes along the dendrite was not significantly affected by any of the anesthetics but there were various changes in somatic firing properties that were highly dependent on the anesthetic. Last, we examined the effects of anesthetics on calcium spike initiation and duration in vivo using high-frequency trains of APs generated at the cell body. We found the same anesthetic-dependent direct effects in addition to an overall reduction in dendritic excitability in anesthetized rats with all three anesthetics compared with the slice preparation.

Differential Impact of Miniature Synaptic Potentials on the Soma and Dendrites of Pyramidal Neurons In Vivo

1997 ◽  
Vol 78 (3) ◽  
pp. 1735-1739 ◽  
Author(s):  
Denis Paré ◽  
Elen Lebel ◽  
Eric J. Lang
Keyword(s):  
Pyramidal Neurons ◽  
Pyramidal Cells ◽  
Input Resistance ◽  
Differential Impact ◽  
Synaptic Potentials ◽  
Ampa Antagonists ◽  
Intact Brain ◽  
The Impact

Paré, Denis, Elen LeBel, and Eric J. Lang. Differential impact of miniature synaptic potentials on the somata and dendrites of pyramidal neurons in vivo. J. Neurophysiol. 78: 1735–1739, 1997. We studied the impact of transmitter release resistant to tetrodotoxin (TTX) in morphologically identified neocortical pyramidal neurons recorded intracellularly in barbiturate-anesthetized cats. It was observed that TTX-resistant release occurs in pyramidal neurons in vivo and at much higher frequencies than was previously reported in vitro. Further, in agreement with previous findings indicating that GABAergic and glutamatergic synapses are differentially distributed in the somata and dendrites of pyramidal cells, we found that most miniature synaptic potentials were sensitive to γ-aminobutyric acid-A (GABAA) or α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) antagonists in presumed somatic and dendritic impalements, respectively. Pharmacological blockage of spontaneous synaptic events produced large increases in input resistance that were more important in dendritic (≈50%) than somatic (≈10%) impalements. These findings imply that in the intact brain, pyramidal neurons are submitted to an intense spike-independent synaptic bombardment that decreases the space constant of the cells. These results should be taken into account when extrapolating in vitro findings to intact brains.

On the Origin of the Extracellular Action Potential Waveform: A Modeling Study

2006 ◽  
Vol 95 (5) ◽  
pp. 3113-3128 ◽  
Author(s):  
Carl Gold ◽  
Darrell A. Henze ◽  
Christof Koch ◽  
György Buzsáki
Keyword(s):  
Action Potential ◽  
Pyramidal Neurons ◽  
Ionic Currents ◽  
Dendritic Morphology ◽  
Electrode Position ◽  
Unit Recording ◽  
Extracellular Recordings ◽  
Ca1 Pyramidal Neurons ◽  
Varied Composition

Although extracellular unit recording is typically used for the detection of spike occurrences, it also has the theoretical ability to report about what are typically considered intracellular features of the action potential. We address this theoretical ability by developing a model system that captures features of experimentally recorded simultaneous intracellular and extracellular recordings of CA1 pyramidal neurons. We use the line source approximation method of Holt and Koch to model the extracellular action potential (EAP) voltage resulting from the spiking activity of individual neurons. We compare the simultaneous intracellular and extracellular recordings of CA1 pyramidal neurons recorded in vivo with model predictions for the same cells reconstructed and simulated with compartmental models. The model accurately reproduces both the waveform and the amplitude of the EAPs, although it was difficult to achieve simultaneous good matches on both the intracellular and extracellular waveforms. This suggests that accounting for the EAP waveform provides a considerable constraint on the overall model. The developed model explains how and why the waveform varies with electrode position relative to the recorded cell. Interestingly, each cell's dendritic morphology had very little impact on the EAP waveform. The model also demonstrates that the varied composition of ionic currents in different cells is reflected in the features of the EAP.

scholarly journals Dendritic spikes in apical oblique dendrites of cortical layer 5 pyramidal neurons

2020 ◽  
Author(s):  
Michael Lawrence G. Castañares ◽  
Greg J. Stuart ◽  
Vincent R. Daria
Keyword(s):  
Sensory Processing ◽  
Pyramidal Neurons ◽  
Low Frequency ◽  
Cortical Layer ◽  
Voltage Gated ◽  
Voltage Gated Calcium Channels ◽  
Basal Dendrites ◽  
Dendritic Spikes ◽  
Specific Computation

AbstractDendritic spikes in layer 5 pyramidal neurons (L5PNs) play a major role in cortical computation. While dendritic spikes have been studied extensively in apical and basal dendrites of L5PNs, whether oblique dendrites, which ramify in the input layers of the cortex, also generate dendritic spikes is unknown. Here we report the existence of dendritic spikes in apical oblique dendrites of L5PNs. In silico investigations indicate that oblique branch spikes are triggered by brief, low-frequency action potential (AP) trains (~40 Hz) and are characterized by a fast sodium spike followed by activation of voltage-gated calcium channels. In vitro experiments confirmed the existence of oblique branch spikes in L5PNs during brief AP trains at frequencies of around 60 Hz. Oblique branch spikes offer new insights into branch-specific computation in L5PNs and may be critical for sensory processing in the input layers of the cortex.

Activity-Related Calcium Dynamics in Motoneurons of the Nucleus Hypoglossus From Mouse

1999 ◽  
Vol 82 (6) ◽  
pp. 2936-2946 ◽  
Author(s):  
Mario B. Lips ◽  
Bernhard U. Keller
Keyword(s):  
Quantitative Analysis ◽  
Action Potential ◽  
Calcium Binding ◽  
Calcium Influx ◽  
Binding Capacity ◽  
Calcium Transients ◽  
Calcium Dynamics ◽  
The Brain

A quantitative analysis of activity-related calcium dynamics was performed in motoneurons of the nucleus hypoglossus in the brain stem slice preparation from mouse by simultaneous patch-clamp and microfluorometric calcium measurements. Motoneurons were analyzed under in vitro conditions that kept them in a functionally intact state represented by rhythmic, inspiratory-related bursts of excitatory postsynaptic currents and associated action potential discharges. Bursts of electrical activity were paralleled by somatic calcium transients resulting from calcium influx through voltage-activated calcium channels, where each action potential accounted for a calcium-mediated charge influx around 2 pC into the somatic compartment. Under in vivo conditions, rhythmic-respiratory activity in young mice occurred at frequencies up to 5 Hz, demonstrating the necessity for rapid calcium elevation and recovery in respiratory-related neurons. The quantitative analysis of hypoglossal calcium homeostasis identified an average extrusion rate, but an exceptionally low endogenous calcium binding capacity as cellular parameters accounting for rapid calcium signaling. Our results suggest that dynamics of somatic calcium transients 1) define an upper limit for the maximum frequency of respiratory-related burst discharges and 2) represent a potentially dangerous determinant of intracellular calcium profiles during pathophysiological and/or excitotoxic conditions.

scholarly journals An In Vitro Protocol for Recording From Spinal Motoneurons of Adult Rats

2008 ◽  
Vol 100 (1) ◽  
pp. 474-481 ◽  
Author(s):  
Jonathan S. Carp ◽  
Ann M. Tennissen ◽  
Donna L. Mongeluzi ◽  
Christopher J. Dudek ◽  
Xiang Yang Chen ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Action Potential ◽  
Mechanical Stability ◽  
Pharmacological Study ◽  
Input Resistance ◽  
Spinal Motoneurons ◽  
Adult Rats ◽  
Precise Control

In vitro slice preparations of CNS tissue are invaluable for studying neuronal function. However, up to now, slice protocols for adult mammal spinal motoneurons—the final common pathway for motor behaviors—have been available for only limited portions of the spinal cord. In most cases, these preparations have not been productive due to the poor viability of motoneurons in vitro. This report describes and validates a new slice protocol that for the first time provides reliable intracellular recordings from lumbar motoneurons of adult rats. The key features of this protocol are: preexposure to 100% oxygen; laminectomy prior to perfusion; anesthesia with ketamine/xylazine; embedding the spinal cord in agar prior to slicing; and, most important, brief incubation of spinal cord slices in a 30% solution of polyethylene glycol to promote resealing of the many motoneuron dendrites cut during sectioning. Together, these new features produce successful recordings in 76% of the experiments and an average action potential amplitude of 76 mV. Motoneuron properties measured in this new slice preparation (i.e., voltage and current thresholds for action potential initiation, input resistance, afterhyperpolarization size and duration, and onset and offset firing rates during current ramps) are comparable to those recorded in vivo. Given the mechanical stability and precise control over the extracellular environment afforded by an in vitro preparation, this new protocol can greatly facilitate electrophysiological and pharmacological study of these uniquely important neurons and other delicate neuronal populations in adult mammals.

Differential conditioning of associative synaptic enhancement in hippocampal brain slices

Science ◽  
1986 ◽  
Vol 232 (4746) ◽  
pp. 85-87 ◽  
Author(s):  
Kelso ◽  
TH Brown
Keyword(s):  
Electrical Stimulation ◽  
High Frequency ◽  
Differential Conditioning ◽  
Pyramidal Neurons ◽  
Brain Slices ◽  
Synaptic Inputs ◽  
Hippocampal Synapses ◽  
Stimulation Paradigm ◽  
Stimulation Of

An electrophysiological stimulation paradigm similar to one that produces Pavlovian conditioning was applied to synaptic inputs to pyramidal neurons of hippocampal brain slices. Persistent synaptic enhancement was induced in one of two weak synaptic inputs by pairing high-frequency electrical stimulation of the weak input with stimulation of a third, stronger input to the same region. Forward (temporally overlapping) but not backward (temporally separate) pairings caused this enhancement. Thus hippocampal synapses in vitro can undergo the conditional and selective type of associative modification that could provide the substrate for some of the mnemonic functions in which the hippocampus is thought to participate.

Sign in / Sign up

Export Citation Format

Share Document