Examining protection from anoxic depolarization by the drugs dibucaine and carbetapentane using whole cell recording from CA1 neurons

2012 ◽  
Vol 107 (8) ◽  
pp. 2083-2095 ◽  
Author(s):  
Sean H. White ◽  
C. Devin Brisson ◽  
R. David Andrew
Keyword(s):  
Pyramidal Neurons ◽  
Cortical Excitability ◽  
Neuronal Damage ◽  
Input Resistance ◽  
Stroke Onset ◽  
Light Transmittance ◽  
Resting Membrane Potential ◽  
Whole Cell ◽  
Anoxic Depolarization

As an immediate consequence of stroke onset, failure of the Na+-K+-ATPase pump evokes a propagating anoxic depolarization (AD) across gray matter. Acute neuronal swelling and dendritic beading arise within seconds in the future ischemic core, imaged as changes in light transmittance (ΔLT). AD is itself not a target for drug-based reduction of stroke injury because it is generated in the 1st min of stroke onset. Peri-infarct depolarizations (PIDs) are milder AD-like events that recur during the hours following AD and contribute to infarct expansion. Inhibiting PIDs with drugs could limit expansion. Two types of drugs, “caines” and σ1-receptor ligands, have been found to inhibit AD onset (and may also oppose PID initiation), yet their underlying actions have not been examined. Imaging ΔLT in the CA1 region simultaneously with whole cell current-clamp recording from CA1 pyramidal neurons reveal that the elevated LT front and onset of the AD are coincident. Either dibucaine or carbetapentane pretreatment significantly delays AD onset without affecting resting membrane potential or neuronal input resistance. Dibucaine decreases excitability by raising spike threshold and decreasing action potential (AP) frequency, whereas carbetapentane eliminates the fast afterhyperpolarization while accentuating the slow afterhyperpolarization to reduce AP frequency. Orthodromic and antidromic APs are eliminated by dibucaine within 15 min but not by carbetapentane. Thus both drugs reduce cortical excitability at the level of the single pyramidal neuron but through strikingly different mechanisms. In vivo, both drugs would likely inhibit recurring PIDs in the expanding penumbra and so potentially could reduce developing neuronal damage over many hours poststroke when PIDs occur.

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.

Imaging Anoxic Depolarization During Ischemia-Like Conditions in the Mouse Hemi-Brain Slice

2001 ◽  
Vol 85 (1) ◽  
pp. 414-424 ◽  
Author(s):  
I. Joshi ◽  
R. D. Andrew
Keyword(s):  
Glutamate Receptor ◽  
Brain Slice ◽  
Neuronal Damage ◽  
Glucose Deprivation ◽  
Light Transmittance ◽  
Cell Swelling ◽  
Receptor Antagonists ◽  
Anoxic Depolarization ◽  
Glutamate Receptor Antagonists ◽  
Ischemic Core

Focal ischemia evokes a sudden loss of membrane potential in neurons and glia of the ischemic core termed the anoxic depolarization (AD). In metabolically compromised regions with partial blood flow, peri-infarct depolarizations (PIDs) further drain energy reserves, promoting acute and delayed neuronal damage. Visualizing and quantifying the AD and PIDs and their acute deleterious effects are difficult in the intact animal. In the present study, we imaged intrinsic optical signals to measure changes in light transmittance in the mouse coronal hemi-brain slice during AD generation. The AD was induced by oxygen/glucose deprivation (OGD) or by ouabain exposure. Potential neuroprotective strategies using glutamate receptor antagonists or reduced temperature were tested. Eight minutes of OGD ( n = 18 slices) or 4 min of 100 μM ouabain ( n = 14) induced a focal increase of increased light transmittance (LT) in neocortical layers II/III that expanded concentrically to form a wave front coursing through neocortex and independently through striatum. The front was coincident with a negative voltage shift in extracellular potential. Wherever the LT front (denoting cell swelling) propagated, a decrease in LT (denoting dendritic beading) followed in its wake. In addition the evoked field potential was permanently lost, indicating neuronal damage. Glutamate receptor antagonists did not block the onset and propagation of AD or the extent of irreversible damage post-AD. Lowering temperature to 25–30°C protected the tissue from OGD damage by inhibiting AD onset. This study shows that anoxic depolarization evoked by global ischemia-like conditions is a spreading process that is focally initiated at multiple sites in cortical and subcortical gray. The combined energy demands of O2/glucose deprivation and the AD greatly exacerbate neuronal damage. Glutamate receptor antagonists neither block the AD in the ischemic core nor, we propose, block recurrent PID arising close to the core.

Electrotonic structure of olfactory sensory neurons analyzed by intracellular and whole cell patch techniques

1991 ◽  
Vol 65 (3) ◽  
pp. 747-758 ◽  
Author(s):  
F. Pongracz ◽  
S. Firestein ◽  
G. M. Shepherd
Keyword(s):  
Sensory Neurons ◽  
Information Transfer ◽  
Experimental Studies ◽  
Input Resistance ◽  
Resting Membrane Potential ◽  
Ambystoma Tigrinum ◽  
Olfactory Sensory Neurons ◽  
Isolated Cells ◽  
Whole Cell

1. Experimental studies employing whole cell patch recordings from freshly isolated olfactory sensory neurons of the salamander (Ambystoma tigrinum) yield much higher estimates of specific membrane resistance (Rm) than studies using conventional intracellular recordings from in situ neurons. Because Rm is critical for understanding information transfer in these cells, we have used computational methods to analyze the possible reasons for this difference. 2. Compartmental models were constructed for both the in situ and isolated neurons, using SABER, a general-purpose simulation program. For Rm in the in situ cell, we used a high value of 100,000 omega.cm2, as estimated in the whole cell recordings from isolated cells. A shunt across the cell membrane caused by the penetrating microelectrode was simulated by several types of shunt mechanisms, and its effects on lowering the apparent value of resting membrane potential (MP), input resistance (RN), and membrane time constant (tau m) and increasing the electrotonic length (L) were analyzed. 3. A good approximation of the electrotonic properties recorded intracellularly was obtained in the in situ model with high Rm combined with an electrode shunt consisting of Na and K conductances. A raised K conductance (1-5 nS) helps to maintain the resting MP while contributing to the increased conductance, which lowers RN and shortens the apparent tau m toward the experimental values. 4. Combined shunt resistances of 0.1-0.2 G omega (5-10 nS) gave the best fits with the experimental data. These shunts were two to three orders of magnitude smaller than the values reported from intracellular penetrations in muscle cells and motoneurons. This may be correlated with the smaller electrode tips used in the recordings from these small neurons. We thus confirm the prediction that even small values of electrode shunt have relatively large effects on the recorded electrotonic properties of small neurons, because of their high RN (2-5 G omega). 5. We have further explored the effects on electrotonic structure of a nonuniform Rm by giving higher Rm values to the distally located cilia compared with the proximal soma-dendritic region, as indicated by recent experiments. For the same RN, large increases in ciliary Rm above 100,000 omega.cm2 can be balanced by relatively small decreases below that value in soma-dendritic Rm. A high ciliary Rm appears to be a specialization for transduction of the sensory input, as reported also in photoreceptors and hair cells.

scholarly journals Cellular and Synaptic Mechanisms That Differentiate Mitral Cells and Superficial Tufted Cells Into Parallel Output Channels in the Olfactory Bulb

2020 ◽  
Vol 14 ◽  
Author(s):  
Shelly Jones ◽  
Joel Zylberberg ◽  
Nathan Schoppa
Keyword(s):  
Olfactory Bulb ◽  
Plexiform Layer ◽  
Input Resistance ◽  
Cell Types ◽  
Mitral Cells ◽  
Whole Cell ◽  
Wide Range ◽  
Tufted Cells ◽  
Parallel Output

A common feature of the primary processing structures of sensory systems is the presence of parallel output “channels” that convey different information about a stimulus. In the mammalian olfactory bulb, this is reflected in the mitral cells (MCs) and tufted cells (TCs) that have differing sensitivities to odors, with TCs being more sensitive than MCs. In this study, we examined potential mechanisms underlying the different responses of MCs vs. TCs. For TCs, we focused on superficial TCs (sTCs), which are a population of output TCs that reside in the superficial-most portion of the external plexiform layer, along with external tufted cells (eTCs), which are glutamatergic interneurons in the glomerular layer. Using whole-cell patch-clamp recordings in mouse bulb slices, we first measured excitatory currents in MCs, sTCs, and eTCs following olfactory sensory neuron (OSN) stimulation, separating the responses into a fast, monosynaptic component reflecting direct inputs from OSNs and a prolonged component partially reflecting eTC-mediated feedforward excitation. Responses were measured to a wide range of OSN stimulation intensities, simulating the different levels of OSN activity that would be expected to be produced by varying odor concentrations in vivo. Over a range of stimulation intensities, we found that the monosynaptic current varied significantly between the cell types, in the order of eTC > sTC > MC. The prolonged component was smaller in sTCs vs. both MCs and eTCs. sTCs also had much higher whole-cell input resistances than MCs, reflecting their smaller size and greater membrane resistivity. To evaluate how these different electrophysiological aspects contributed to spiking of the output MCs and sTCs, we used computational modeling. By exchanging the different cell properties in our modeled MCs and sTCs, we could evaluate each property's contribution to spiking differences between these cell types. This analysis suggested that the higher sensitivity of spiking in sTCs vs. MCs reflected both their larger monosynaptic OSN signal as well as their higher input resistance, while their smaller prolonged currents had a modest opposing effect. Taken together, our results indicate that both synaptic and intrinsic cellular features contribute to the production of parallel output channels in the olfactory bulb.

scholarly journals Maturation of Intrinsic and Synaptic Properties of Layer 2/3 Pyramidal Neurons in Mouse Auditory Cortex

2008 ◽  
Vol 99 (6) ◽  
pp. 2998-3008 ◽  
Author(s):  
Anne-Marie M. Oswald ◽  
Alex D. Reyes
Keyword(s):  
Auditory Processing ◽  
Pyramidal Neurons ◽  
Input Resistance ◽  
Transitional Period ◽  
Resting Membrane Potential ◽  
Neural Excitability ◽  
Age Related ◽  
Mean And Variance ◽  
Whole Cell Recordings

We investigated the development of L2/3 pyramidal cell (PC) circuitry in juvenile mice from postnatal day 10 (P10) to P29. Using whole cell recordings in an in vitro thalamocortical slice preparation, we examined the connection architecture and intrinsic and synaptic properties of PCs. The excitatory connections between PCs were highly localized: the probability of connection between PCs declined with intersomatic distance from 0.18 to about 0.05 over 150 μm, but did not vary with age. However, the mean and variance of the intrinsic and synaptic properties of PCs changed dramatically between P10 and P29. The input resistance, membrane time constant, and resting membrane potential decreased, leading to reduced neural excitability in older animals. Likewise, there were age-dependent decreases in the amplitude and decay time of the excitatory postsynaptic potentials as well as short-term synaptic depression. Both the intrinsic and synaptic properties underwent a transitional period between P10 and P18 prior to reaching steady state at P19–P29. We show that these properties combine to produce age-related differential synaptic responses to low- and high-frequency synaptic input that may contribute to differences in auditory processing during development.

High-conductance states and A-type K+ channels are potential regulators of the conductance-current balance triggered by HCN channels

2015 ◽  
Vol 113 (1) ◽  
pp. 23-43 ◽  
Author(s):  
Poonam Mishra ◽  
Rishikesh Narayanan
Keyword(s):  
Dominant Role ◽  
Input Resistance ◽  
Resting Membrane Potential ◽  
Voltage Response ◽  
Hcn Channels ◽  
Type K ◽  
Conductance States ◽  
The Impact ◽  
High Conductance

An increase in the hyperpolarization-activated cyclic nucleotide-gated (HCN) channel conductance reduces input resistance, whereas the consequent increase in the inward h current depolarizes the membrane. This results in a delicate and unique conductance-current balance triggered by the expression of HCN channels. In this study, we employ experimentally constrained, morphologically realistic, conductance-based models of hippocampal neurons to explore certain aspects of this conductance-current balance. First, we found that the inclusion of an experimentally determined gradient in A-type K+ conductance, but not in M-type K+ conductance, tilts the HCN conductance-current balance heavily in favor of conductance, thereby exerting an overall restorative influence on neural excitability. Next, motivated by the well-established modulation of neuronal excitability by synaptically driven high-conductance states observed under in vivo conditions, we inserted thousands of excitatory and inhibitory synapses with different somatodendritic distributions. We measured the efficacy of HCN channels, independently and in conjunction with other channels, in altering resting membrane potential (RMP) and input resistance ( Rin) when the neuron received randomized or rhythmic synaptic bombardments through variable numbers of synaptic inputs. We found that the impact of HCN channels on average RMP, Rin, firing frequency, and peak-to-peak voltage response was severely weakened under high-conductance states, with the impinging synaptic drive playing a dominant role in regulating these measurements. Our results suggest that the debate on the role of HCN channels in altering excitability should encompass physiological and pathophysiological neuronal states under in vivo conditions and the spatiotemporal interactions of HCN channels with other channels.

Permanent Reduction of Seizure Threshold in Post-Ischemic CA3 Pyramidal Neurons

2000 ◽  
Vol 83 (4) ◽  
pp. 2040-2046 ◽  
Author(s):  
Patrice Congar ◽  
Jean-Luc Gaïarsa ◽  
Théodora Popovici ◽  
Yezekiel Ben-Ari ◽  
Valérie Crépel
Keyword(s):  
Pyramidal Neurons ◽  
Hippocampal Slices ◽  
Pyramidal Cells ◽  
Input Resistance ◽  
Seizure Threshold ◽  
Resting Membrane Potential ◽  
Epileptic Syndromes ◽  
Ca3 Pyramidal Neurons ◽  
Ca3 Pyramidal Cells ◽  
Firing Properties

The effects of ischemia were examined on CA3 pyramidal neurons recorded in hippocampal slices 2–4 mo after a global forebrain insult. With intracellular recordings, CA3 post-ischemic neurons had a more depolarized resting membrane potential but no change of the input resistance, spike threshold and amplitude, fast and slow afterhyperpolarization (AHP) or ADP, and firing properties in response to depolarizing pulses. With both field and whole-cell recordings, synaptic responses were similar in control and post-ischemic neurons. Although there were no spontaneous network-driven discharges, the post-ischemic synaptic network had a smaller threshold to generate evoked and spontaneous synchronized burst discharges. Thus lower concentrations of convulsive agents (kainate, high K+) triggered all-or-none network-driven synaptic events in post-ischemic neurons more readily than in control ones. Also, paired-pulse protocol generates, in post-ischemics but not controls, synchronized field burst discharges when interpulse intervals ranged from 60 to 100 ms. In conclusion, 2–4 mo after the insult, the post-ischemic CA3 pyramidal cells are permanently depolarized and have a reduced threshold to generate synchronized bursts. This may explain some neuropathological and behavioral consequences of ischemia as epileptic syndromes observed several months to several years after the ischemic insult.

scholarly journals Dopamine Increases Excitability of Pyramidal Neurons in Primate Prefrontal Cortex

2000 ◽  
Vol 84 (6) ◽  
pp. 2799-2809 ◽  
Author(s):  
Darrell A. Henze ◽  
Guillermo R. González-Burgos ◽  
Nathaniel N. Urban ◽  
David A. Lewis ◽  
German Barrionuevo
Keyword(s):  
Prefrontal Cortex ◽  
Action Potential ◽  
Pyramidal Neurons ◽  
Pyramidal Cells ◽  
Input Resistance ◽  
Initiation Site ◽  
D1 Receptor ◽  
Resting Membrane Potential ◽  
Cellular Mechanisms

Dopaminergic modulation of neuronal networks in the dorsolateral prefrontal cortex (PFC) is believed to play an important role in information processing during working memory tasks in both humans and nonhuman primates. To understand the basic cellular mechanisms that underlie these actions of dopamine (DA), we have investigated the influence of DA on the cellular properties of layer 3 pyramidal cells in area 46 of the macaque monkey PFC. Intracellular voltage recordings were obtained with sharp and whole cell patch-clamp electrodes in a PFC brain-slice preparation. All of the recorded neurons in layer 3 ( n = 86) exhibited regular spiking firing properties consistent with those of pyramidal neurons. We found that DA had no significant effects on resting membrane potential or input resistance of these cells. However DA, at concentrations as low as 0.5 μM, increased the excitability of PFC cells in response to depolarizing current steps injected at the soma. Enhanced excitability was associated with a hyperpolarizing shift in action potential threshold and a decreased first interspike interval. These effects required activation of D1-like but not D2-like receptors since they were inhibited by the D1 receptor antagonist SCH23390 (3 μM) but not significantly altered by the D2 antagonist sulpiride (2.5 μM). These results show, for the first time, that DA modulates the activity of layer 3 pyramidal neurons in area 46 of monkey dorsolateral PFC in vitro. Furthermore the results suggest that, by means of these effects alone, DA modulation would generally enhance the response of PFC pyramidal neurons to excitatory currents that reach the action potential initiation site.

Functional Roles of Kv1 Channels in Neocortical Pyramidal Neurons

2007 ◽  
Vol 97 (3) ◽  
pp. 1931-1940 ◽  
Author(s):  
D. Guan ◽  
J. C. F. Lee ◽  
M. H. Higgs ◽  
W. J. Spain ◽  
R. C. Foehring
Keyword(s):  
Voltage Clamp ◽  
Pyramidal Neurons ◽  
Brain Slices ◽  
Outward Current ◽  
Input Resistance ◽  
Repetitive Firing ◽  
Resting Membrane Potential ◽  
Voltage Threshold ◽  
Functional Roles ◽  
Ramp Voltage

Pyramidal neurons from layers II/III of somatosensory and motor cortex express multiple Kv1 α-subunits and a current sensitive to block by α-dendrotoxin (α-DTX). We examined functional roles of native Kv1 channels in these cells using current-clamp recordings in brain slices and current- and voltage-clamp recordings in dissociated cells. α-DTX caused a significant negative shift in voltage threshold for action potentials (APs) and reduced rheobase. Correspondingly, a ramp-voltage protocol revealed that the α-DTX–sensitive current activated at subthreshold voltages. AP width at threshold increased with successive APs during repetitive firing. The steady-state threshold width for a given firing rate was similar in control and α-DTX, despite an initially broader AP in α-DTX. AP voltage threshold increased similarly during a train of spikes under control conditions and in the presence of α-DTX. α-DTX had no effect on input resistance or resting membrane potential and modest effects on the amplitude or width of a single AP. Accordingly, experiments using AP waveforms (APWs) as voltage protocols revealed that α-DTX–sensitive current peaked late during the AP repolarization phase. Application of α-DTX increased the rate of firing to intracellular current injection and increased gain (multiplicative effects), but did not alter spike-frequency adaptation. Consistent with these findings, voltage-clamp experiments revealed that the proportion of outward current sensitive to α-DTX was highest during the interval between two APWs, reflecting slow deactivation kinetics at −50 mV. Finally, α-DTX did not alter the selectivity of pyramidal neurons for DC versus time-varying stimuli.

scholarly journals Enhanced Neuronal Damage After Ischemic Insults in Mice Lacking Kir6.2-Containing ATP-Sensitive K+ Channels

2006 ◽  
Vol 95 (4) ◽  
pp. 2590-2601 ◽  
Author(s):  
Hong-Shuo Sun ◽  
Zhong-Ping Feng ◽  
Takashi Miki ◽  
Susumu Seino ◽  
Robert J. French
Keyword(s):  
Hippocampal Neurons ◽  
Pyramidal Neurons ◽  
Neuronal Damage ◽  
Focal Cerebral Ischemia ◽  
Hippocampal Slices ◽  
Immunocytochemical Staining ◽  
Sulfonylurea Receptor ◽  
Ca1 Pyramidal Neurons

Adenosine triphosphate (ATP)–sensitive potassium (KATP) channels, incorporating Kir6.x and sulfonylurea receptor subunits, are weak inward rectifiers that are thought to play a role in neuronal protection from ischemic insults. However, the involvement of Kir6.2-containing KATP channel in hippocampus and neocortex has not been tested directly. To delineate the physiological roles of Kir6.2 channels in the CNS, we used knockout (KO) mice that do not express Kir6.2. Immunocytochemical staining demonstrated that Kir6.2 protein was expressed robustly in hippocampal neurons of the wild-type (WT) mice and absent in the KO. To examine neuronal sensitivity to metabolic stress in vitro, and to ischemia in vivo, we 1) exposed hippocampal slices to transient oxygen and glucose deprivation (OGD) and 2) produced focal cerebral ischemia by middle cerebral artery occlusion (MCAO). Both slice and whole animal studies showed that neurons from the KO mice were severely damaged after anoxia or ischemia, whereas few injured neurons were observed in the WT, suggesting that Kir6.2 channels are necessary to protect neurons from ischemic insults. Membrane potential recordings from the WT CA1 pyramidal neurons showed a biphasic response to OGD; a brief hyperpolarization was followed by a small depolarization during OGD, with complete recovery within 30 min after returning to normoxic conditions. By contrast, CA1 pyramidal neurons from the KO mice were irreversibly depolarized by OGD exposure, without any preceding hyperpolarization. These data suggest that expression of Kir6.2 channels prevents prolonged depolarization of neurons resulting from acute hypoxic or ischemic insults, and thus protects these central neurons from the injury.

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