scholarly journals Modulation of EPSP shape and efficacy by intrinsic membrane conductances in rat neocortical pyramidal neurons in vitro.

1993 ◽  
Vol 468 (1) ◽  
pp. 693-710 ◽  
Author(s):  
A Nicoll ◽  
A Larkman ◽  
C Blakemore
Keyword(s):  
Pyramidal Neurons ◽  
Membrane Conductances ◽  
Neocortical Pyramidal Neurons

Simulations of Intrinsically Bursting Neocortical Pyramidal Neurons

1994 ◽  
Vol 6 (6) ◽  
pp. 1086-1110 ◽  
Author(s):  
Paul A. Rhodes ◽  
Charles M. Gray
Keyword(s):  
Visual Cortex ◽  
Ion Channels ◽  
Pyramidal Neurons ◽  
Compartment Model ◽  
Morphological Data ◽  
High Threshold ◽  
Simulation Results ◽  
Dendritic Branches ◽  
Neocortical Pyramidal Neurons

Neocortical layer 5 intrinsically bursting (IB) pyramidal neurons were simulated using compartment model methods. Morphological data as well as target neurophysiological responses were taken from a series of published studies on the same set of rat visual cortex pyramidal neurons (Mason, A. and Larkman, A. J., 1990. J. Neurosci. 9,1440-1447; Larkman, A. J. 1991. J. Comp. Neurol. 306, 307-319). A dendritic distribution of ion channels was found that reproduced the range of in vitro responses of layer 5 IB pyramidal neurons, including the transition from repetitive bursting to the burst/tonic spiking mode seen in these neurons as input magnitude increases. In light of available data, the simulation results suggest that in these neurons bursts are driven by an inward flow of current during a high threshold Ca2+ spike extending throughout both the basal and apical dendritic branches.

Linear to Supralinear Summation of AMPA-Mediated EPSPs in Neocortical Pyramidal Neurons

2000 ◽  
Vol 83 (6) ◽  
pp. 3310-3322 ◽  
Author(s):  
Jilda S. Nettleton ◽  
William J. Spain
Keyword(s):  
Cortical Neurons ◽  
Pyramidal Neurons ◽  
Coincidence Detection ◽  
Layer V ◽  
Layer I ◽  
The Individual ◽  
Dc Current ◽  
Neocortical Pyramidal Neurons

It has been hypothesized that voltage-sensitive conductances present on the dendrites of neurons can influence summation of excitatory postsynaptic potentials (EPSPs) and hence affect how neurons compile information. Greater than linear summation of EPSPs has been postulated to facilitate coincidence detection by cortical neurons. This study examined whether the summation of subthreshold AMPA-mediated EPSPs generated on layer V neocortical pyramidal neurons in vitro was linear and if any nonlinearities could be attributed to dendritic conductances. Evoked EPSPs (1–12 mV) were recorded somatically by means of intracellular sharp electrodes in the presence of 100 μM amino-5-phosphonopentanoic acid (AP-5) and 3 μM bicuculline. Two independent EPSPs were evoked by a stimulating electrode in layer I and another in layers III–V. The areas of stimulation were isolated from each other by a horizontal cut below layer I. By subtracting the algebraic sum of the individual EPSPs from the evoked response when both EPSPs were evoked simultaneously, we determined that they summed linearly to supralinearly. Supralinear summation was more likely when the soma was hyperpolarized by DC current injection. Summation was predominantly linear when postsynaptic conductances (i.e., Na+ and Ca2+) were blocked with intracellular QX-314. The supralinear summation of EPSPs (without QX-314) decreased as the time between inputs was increased from 0 to 30 ms. To determine the role of dendrites in nonlinear summation, we substituted a current pulse (simulated EPSP) delivered at the soma for either or both of the evoked EPSPs. Simulated EPSPs combined with either an evoked EPSP or another simulated EPSP showed significantly less supralinear summation than two evoked EPSPs, indicating that the dendritic conductances were largely responsible for the observed supralinear summation.

Impact of Spontaneous Synaptic Activity on the Resting Properties of Cat Neocortical Pyramidal Neurons In Vivo

1998 ◽  
Vol 79 (3) ◽  
pp. 1450-1460 ◽  
Author(s):  
Denis Paré ◽  
Eric Shink ◽  
Hélène Gaudreau ◽  
Alain Destexhe ◽  
Eric J. Lang
Keyword(s):  
Cortical Neurons ◽  
Pyramidal Neurons ◽  
Brain Slices ◽  
Synaptic Activity ◽  
Intact Brain ◽  
Lower Temperature ◽  
The Impact ◽  
Neocortical Pyramidal Neurons

Paré, Denis, Eric Shink, Hélène Gaudreau, Alain Destexhe, and Eric J. Lang. Impact of spontaneous synaptic activity on the resting properties of cat neocortical pyramidal neurons in vivo. J. Neurophysiol. 79: 1450–1460, 1998. The frequency of spontaneous synaptic events in vitro is probably lower than in vivo because of the reduced synaptic connectivity present in cortical slices and the lower temperature used during in vitro experiments. Because this reduction in background synaptic activity could modify the integrative properties of cortical neurons, we compared the impact of spontaneous synaptic events on the resting properties of intracellularly recorded pyramidal neurons in vivo and in vitro by blocking synaptic transmission with tetrodotoxin (TTX). The amount of synaptic activity was much lower in brain slices (at 34°C), as the standard deviation of the intracellular signal was 10–17 times lower in vitro than in vivo. Input resistances ( R ins) measured in vivo during relatively quiescent epochs (“control R ins”) could be reduced by up to 70% during periods of intense spontaneous activity. Further, the control R ins were increased by ∼30–70% after TTX application in vivo, approaching in vitro values. In contrast, TTX produced negligible R in changes in vitro (∼4%). These results indicate that, compared with the in vitro situation, the background synaptic activity present in intact networks dramatically reduces the electrical compactness of cortical neurons and modifies their integrative properties. The impact of the spontaneous synaptic bombardment should be taken into account when extrapolating in vitro findings to the intact brain.

Dopamine Increases the Gain of the Input-Output Response of Rat Prefrontal Pyramidal Neurons

2008 ◽  
Vol 99 (6) ◽  
pp. 2985-2997 ◽  
Author(s):  
Kay Thurley ◽  
Walter Senn ◽  
Hans-Rudolf Lüscher
Keyword(s):  
Working Memory ◽  
Neuronal Excitability ◽  
Pyramidal Neurons ◽  
D1 Receptors ◽  
Input Output ◽  
Prefrontal Cortical ◽  
Noisy Input ◽  
Relationship Of

Dopaminergic modulation of prefrontal cortical activity is known to affect cognitive functions like working memory. Little consensus on the role of dopamine modulation has been achieved, however, in part because quantities directly relating to the neuronal substrate of working memory are difficult to measure. Here we show that dopamine increases the gain of the frequency-current relationship of layer 5 pyramidal neurons in vitro in response to noisy input currents. The gain increase could be attributed to a reduction of the slow afterhyperpolarization by dopamine. Dopamine also increases neuronal excitability by shifting the input-output functions to lower inputs. The modulation of these response properties is mainly mediated by D1 receptors. Integrate-and-fire neurons were fitted to the experimentally recorded input-output functions and recurrently connected in a model network. The gain increase induced by dopamine application facilitated and stabilized persistent activity in this network. The results support the hypothesis that catecholamines increase the neuronal gain and suggest that dopamine improves working memory via gain modulation.

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.

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