Characterization of GABAA receptor function in human temporal cortical neurons

1996 ◽  
Vol 75 (4) ◽  
pp. 1458-1471 ◽  
Author(s):  
J. W. Gibbs ◽  
Y. F. Zhang ◽  
C. Q. Kao ◽  
K. L. Holloway ◽  
K. S. Oh ◽  
...  
Keyword(s):  
Patch Clamp ◽  
Functional Properties ◽  
Cortical Neurons ◽  
Pyramidal Neurons ◽  
Temporal Cortex ◽  
Hill Coefficient ◽  
Excitatory Postsynaptic Potential ◽  
Adult Rat ◽  
Postsynaptic Potential ◽  
Resected Tissue

1. Surgically resected tissue from the tip of the human temporal lobe of seven patients undergoing temporal lobectomy was employed to study functional properties of GABAergic inhibition mediated through activation of GABAA receptors, using patch-clamp recording techniques in acutely isolated neurons and in slices of human temporal cortex. 2. Human temporal cortical pyramidal neurons from surgically resected tissue could be acutely isolated with the use of conventional methods. These neurons appeared normal in morphology, in their intrinsic membrane properties, and in their response to application of exogenous gamma-aminobutyric acid (GABA). 3. Application of GABA to acutely isolated human temporal cortical neurons elicited a large current with an average reversal potential of -65 mV, presumably mediated through a GABAA-activated chloride conductance. Application of varying concentrations of GABA generated a concentration/response relationship that could be well-fitted by a conventional sigmoidal curve, with an EC50 of 25.5 microM and a Hill coefficient of 1.0 4. Coapplication of the benzodiazepine clonazepam and 10 microM GABA augmented the amplitude of the GABA response. The concentration dependence of this benzodiazepine augmentation could be best-fitted by an equation assuming that the benzodiazepine interacted with two distinct binding sites, with differing potencies. The high-potency site had an EC50 of 0.06 nM and maximally contributed 38.5% augmentation to the total effect of clonazepam. The lower potency site had an EC50 of 16.4 nM, and contributed 66.1% maximal augmentation to the overall effect of clonazepam. These data derived from adult human temporal cortical neurons were very similar to our findings in adult rat sensory cortical neurons. 5. The effects of equimolar concentrations (100 nM) of clonazepam, a BZ1 and BZ2 agonist, and zolpidem, a selective BZ1 agonist, on acutely isolated human temporal cortical neurons were also investigated. Zolpidem and clonazepam were equally effective (71.5 vs. 65.0%, respectively) in potentiating GABA responses elicited by application of 10 microM GABA. This suggests that many of the functional benzodiazepine receptors in these neurons were of the BZ1 variety. 6. GABAergic synaptic inhibition was also studied with the use of patch-clamp recordings in slices of human temporal cortex. Extracellular stimulation at the white matter/gray matter border elicited compound synaptic events in layer II-V cortical neurons. These events usually consisted of an early excitatory postsynaptic potential (EPSP) and a late multiphasic inhibitory postsynaptic potential (IPSP). Application of either clonazepam or zolpidem (both at 100 nM) to the slice during extracellular stimulation reversibly augmented the late compound IPSP. 7. Spontaneous IPSPs were also recorded in approximately 50% of human temporal cortical neurons. These events did not have a preceding EPSP and were usually monopolar, with a single exponential rise and decay. This supported the idea that these events were triggered by spontaneous activity of GABAergic interneurons. Bath application of either clonazepam or zolpidem (both at 100nM) to the slice during ongoing spontaneous IPSP activity increased the amplitude and lengthened the time constant of decay of these events. 8. To our knowledge, this is one of the first detailed characterizations of the functional properties of GABAA-mediated inhibition in human cortical neurons using patch-clamp recordings in both isolated cells and slices of resected temporal cortex. Isolated pyramidal neurons exhibited GABAA-mediated currents that were comparable in many aspects with GABA currents recorded from adult rat cortical neurons, including similar GABA concentration/response curves, and similar two differing potency site effects for clonazepam augmentation of GABA currents. In addition, evoked and spontaneous IPSPs recorded in human cortical neurons appeared similar to IPSPs in rat cortical

Persistent hyperexcitability in isolated hippocampal CA1 of kainate-lesioned rats

1992 ◽  
Vol 68 (6) ◽  
pp. 2120-2127 ◽  
Author(s):  
C. L. Meier ◽  
A. Obenaus ◽  
F. E. Dudek
Keyword(s):  
Pyramidal Neurons ◽  
Hippocampal Sclerosis ◽  
Mean Amplitude ◽  
Cell Loss ◽  
Stratum Radiatum ◽  
Excitatory Postsynaptic Potential ◽  
Population Spikes ◽  
Acute Seizures ◽  
Postsynaptic Potential ◽  
Area Ca1

1. Subcutaneous kainate injection in rats evoked acute seizures and led to cell loss in the hilus and areas CA1 and CA3, which resembled the pattern of hippocampal sclerosis often associated with temporal lobe epilepsy in humans. 2. Simultaneous intra- and extracellular recordings were performed in the stratum pyramidale of area CA1 while stimulating in the stratum radiatum close to the recording electrodes. Responses from control slices consisted of a brief excitatory postsynaptic potential (EPSP) with only one action potential, corresponding to a single extracellular population spike, followed by a clear biphasic inhibitory postsynaptic potential (IPSP). In slices from kainate-treated animals, however, stimulation evoked a prolonged EPSP, which often triggered multiple action potentials corresponding to multiple extracellular population spikes. 3. In slices from kainate-treated animals, the mean amplitude but not the duration of the stimulation-evoked IPSP was reduced. The extent of the kainate-induced loss of inhibition in area CA1 was highly variable. 4. Low concentrations of bicuculline in control slices led to a moderate hyperexcitability, which consisted of multiple population spikes and mirrored the responses observed in slices from kainate-treated animals in normal ACSF. Prolonged application of 10-30 microM bicuculline for > or = 30 min led to a much higher level of hyperexcitability, which was similar in slices from controls and kainate-treated rats. These findings are consistent with the hypothesis that the hyperexcitability of CA1 pyramidal neurons following kainate treatment is mainly due to decreased GABAA-receptor-mediated inhibition and that the loss of inhibition is only partial.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Large and fast human pyramidal neurons associate with intelligence

2018 ◽  
Author(s):  
Natalia A. Goriounova ◽  
Djai B. Heyer ◽  
René Wilbers ◽  
Matthijs B. Verhoog ◽  
Michele Giugliano ◽  
...  
Keyword(s):  
Action Potential ◽  
Brain Imaging ◽  
Cortical Thickness ◽  
Cortical Neurons ◽  
Information Transfer ◽  
Pyramidal Neurons ◽  
Temporal Cortex ◽  
Neuron Activity ◽  
Human Intelligence ◽  
Iq Scores

AbstractIt is generally assumed that human intelligence relies on efficient processing by neurons in our brain. Behavioral and brain-imaging studies robustly show that higher intelligence associates with faster reaction times and thicker gray matter in temporal and frontal cortical areas. However, no direct evidence exists that links individual neuron activity and structure to human intelligence. Since a large part of cortical grey matter consists of dendrites, these structures likely determine cortical architecture. In addition, dendrites strongly affect functional properties of neurons, including action potential speed. Thereby, dendritic size and action potential firing may constitute variation in cortical thickness, processing speed, and ultimately IQ.To investigate this, we took advantage of brain tissue available from neurosurgery and recorded from pyramidal neurons in the medial temporal cortex, an area showing high association between cortical thickness, cortical activity and intelligence. Next, we reconstructed full dendritic structures of recorded neurons and combined these with brain-imaging data and IQ scores from the same subjects. We find that high IQ scores and large temporal cortical thickness associate with larger, more complex dendrites of human pyramidal neurons. We show in silico that larger dendrites enable pyramidal neurons to track activity of synaptic inputs with higher temporal precision, due to fast action potential initiation. Finally, we find that human pyramidal neurons of individuals with higher IQ scores sustain faster action potentials during repeated firing. These findings provide first evidence that human intelligence is associated with neuronal complexity, action potential speed and efficient information transfer in cortical neurons.

scholarly journals Unique membrane properties and enhanced signal processing in human neocortical neurons

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Guy Eyal ◽  
Matthijs B Verhoog ◽  
Guilherme Testa-Silva ◽  
Yair Deitcher ◽  
Johannes C Lodder ◽  
...  
Keyword(s):  
Signal Processing ◽  
Cortical Neurons ◽  
Pyramidal Neurons ◽  
Temporal Cortex ◽  
Building Blocks ◽  
Membrane Properties ◽  
Human Neocortex ◽  
Neocortical Neurons ◽  
Fitting In

The advanced cognitive capabilities of the human brain are often attributed to our recently evolved neocortex. However, it is not known whether the basic building blocks of the human neocortex, the pyramidal neurons, possess unique biophysical properties that might impact on cortical computations. Here we show that layer 2/3 pyramidal neurons from human temporal cortex (HL2/3 PCs) have a specific membrane capacitance (Cm) of ~0.5 µF/cm2, half of the commonly accepted 'universal' value (~1 µF/cm2) for biological membranes. This finding was predicted by fitting in vitro voltage transients to theoretical transients then validated by direct measurement of Cm in nucleated patch experiments. Models of 3D reconstructed HL2/3 PCs demonstrated that such low Cm value significantly enhances both synaptic charge-transfer from dendrites to soma and spike propagation along the axon. This is the first demonstration that human cortical neurons have distinctive membrane properties, suggesting important implications for signal processing in human neocortex.

Increased Pyramidal Excitability and NMDA Conductance Can Explain Posttraumatic Epileptogenesis Without Disinhibition: A Model

1999 ◽  
Vol 82 (4) ◽  
pp. 1748-1758 ◽  
Author(s):  
Paul C. Bush ◽  
David A. Prince ◽  
Kenneth D. Miller
Keyword(s):  
Experimental Data ◽  
Pyramidal Neurons ◽  
Rapid Development ◽  
Pyramidal Cells ◽  
Membrane Properties ◽  
Excitatory Postsynaptic Potential ◽  
Physiological Basis ◽  
Postsynaptic Potential ◽  
Layer V ◽  
Epileptiform Events

Partially isolated cortical islands prepared in vivo become epileptogenic within weeks of the injury. In this model of chronic epileptogenesis, recordings from cortical slices cut through the injured area and maintained in vitro often show evoked, long- and variable-latency multiphasic epileptiform field potentials that also can occur spontaneously. These events are initiated in layer V and are synchronous with polyphasic long-duration excitatory and inhibitory potentials (currents) in neurons that may last several hundred milliseconds. Stimuli that are significantly above threshold for triggering these epileptiform events evoke only a single large excitatory postsynaptic potential (EPSP) followed by an inhibitory postsynaptic potential (IPSP). We investigated the physiological basis of these events using simulations of a layer V network consisting of 500 compartmental model neurons, including 400 principal (excitatory) and 100 inhibitory cells. Epileptiform events occurred in response to a stimulus when sufficient N-methyl-d-aspartate (NMDA) conductance was activated by feedback excitatory activity among pyramidal cells. In control simulations, this activity was prevented by the rapid development of IPSPs. One manipulation that could give rise to epileptogenesis was an increase in the threshold of inhibitory interneurons. However, previous experimental data from layer V pyramidal neurons of these chronic epileptogenic lesions indicate: upregulation, rather than downregulation, of inhibition; alterations in the intrinsic properties of pyramidal cells that would tend to make them more excitable; and sprouting of their intracortical axons and increased numbers of presumed synaptic contacts, which would increase recurrent EPSPs from one cell onto another. Consistent with this, we found that increasing the excitability of pyramidal cells and the strength of NMDA conductances, in the face of either unaltered or increased inhibition, resulted in generation of epileptiform activity that had characteristics similar to those of the experimental data. Thus epileptogenesis such as occurs after chronic cortical injury can result from alterations of intrinsic membrane properties of pyramidal neurons together with enhanced NMDA synaptic conductances.

CA3 neuron excitation and epileptiform discharge are sensitive to osmolality

1993 ◽  
Vol 69 (6) ◽  
pp. 2200-2208 ◽  
Author(s):  
V. Saly ◽  
R. D. Andrew
Keyword(s):  
Action Potential ◽  
Cortical Neurons ◽  
Hippocampal Slices ◽  
Clinical Signs ◽  
Field Potential ◽  
Mossy Fibers ◽  
Excitatory Postsynaptic Potential ◽  
Epsp Amplitude ◽  
Postsynaptic Potential ◽  
Ca3 Neurons

1. The clinical signs of rapidly developing overhydration commonly include generalized tonic-clonic seizure, which can be combatted by raising plasma osmolality. How cortical neurons respond to osmotic imbalance has been addressed only recently. In the CA3 cell region of hippocampal slices, lowered osmolality (-40 mOsm) rapidly swelled cells, increasing field potential amplitude over a period of 8 min and thereby elevating field effects and associated neuronal synchronization. 2. Over a longer time course (10-30 min), spontaneous excitatory postsynaptic potential (EPSP) amplitude gradually increased in 7 of 10 CA3 neurons recorded intracellularly. In nine additional CA3 cells, hyposmolality gradually induced combinations of action potential discharge, endogenous bursting, and increased synchronized synaptic input. All of these effects reversed in normosmotic ACSF. 3. Hyperosmotic artificial cerebrospinal fluid (ACSF) using mannitol reduced field potentials and dramatically lowered CA3 excitability by reducing spontaneous EPSP amplitude and associated bursting. Again, the gradual onset (10-30 min) of changes in spontaneous EPSP amplitude appeared independent of field potential changes, which were already maximal by 8 min. 4. Cutting mossy fibers did not affect the excitability changes induced by osmotic stress noted above. The EPSP/inhibitory postsynaptic potential (IPSP) sequence evoked from mossy fibers or stratum oriens was unaltered by osmotic change and so did not represent osmosensitive afferent input to CA3 neurons. Furthermore, as measured at the soma, resting membrane potential, cell input resistance, and the action potential threshold were unchanged in all cells. It followed that, because the CA3 neurons themselves were not responsive, a recurrent excitatory pathway could not represent the osmosensitive input.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Human cortical pyramidal neurons: From spines to spikes via models

2018 ◽  
Author(s):  
Guy Eyal ◽  
Matthias B. Verhoog ◽  
Guilherme Testa-Silva ◽  
Yair Deitcher ◽  
Ruth Benavides-Piccione ◽  
...  
Keyword(s):  
Dendritic Spines ◽  
Cortical Neurons ◽  
Pyramidal Neurons ◽  
Temporal Cortex ◽  
Pyramidal Cells ◽  
Physiological Data ◽  
Excitatory Synapses ◽  
Basal Dendrites ◽  
Cortical Pyramidal Neurons ◽  
Dendritic Branches

AbstractWe present the first-ever detailed models of pyramidal cells from human neocortex, including models on their excitatory synapses, dendritic spines, dendritic NMDA- and somatic/axonal- Na+ spikes that provided new insights into signal processing and computational capabilities of these principal cells. Six human layer 2 and layer 3 pyramidal cells (HL2/L3 PCs) were modeled, integrating detailed anatomical and physiological data from both fresh and post mortem tissues from human temporal cortex. The models predicted particularly large AMPA- and NMDA- conductances per synaptic contact (0.88 nS and 1.31nS, respectively) and a steep dependence of the NMDA-conductance on voltage. These estimates were based on intracellular recordings from synaptically-connected HL2/L3 pairs, combined with extra-cellular current injections and use of synaptic blockers. A large dataset of high-resolution reconstructed HL2/L3 dendritic spines provided estimates for the EPSPs at the spine head (12.7 ± 4.6 mV), spine base (9.7 ± 5.0 mV) and soma (0.3 ± 0.1 mV), and for the spine neck resistance (50 – 80 MΩ). Matching the shape and firing pattern of experimental somatic Na+-spikes provided estimates for the density of the somatic/axonal excitable membrane ion channels, predicting that 134 ± 28 simultaneously activated HL2/L3- HL2/L3 synapses are required for generating (with 50% probability) a somatic Na+ spike. Dendritic NMDA spikes were triggered in the model when 20 ± 10 excitatory spinous synapses were simultaneously activated on individual dendritic branches. The particularly large number of basal dendrites in HL2/L3 PCs and the distinctive cable elongation of their terminals imply that ~25 NMDA- spikes could be generated independently and simultaneously in these cells, as compared to ~14 in L2/3 PCs from the rat temporal cortex. These multi-sites nonlinear signals, together with the large (~30,000) excitatory synapses/cell, equip human L2/L3 PCs with enhanced computational capabilities. Our study provides the most comprehensive model of any human neuron to-date demonstrating the biophysical and computational distinctiveness of human cortical neurons.

Electrically coupled pacemaker neurons respond differently to same physiological inputs and neurotransmitters

1984 ◽  
Vol 51 (6) ◽  
pp. 1362-1374 ◽  
Author(s):  
E. Marder ◽  
J. S. Eisen
Keyword(s):  
Motor Neurons ◽  
Slow Wave ◽  
Lucifer Yellow ◽  
Electrical Coupling ◽  
Excitatory Postsynaptic Potential ◽  
Panulirus Interruptus ◽  
Bursting Neuron ◽  
Postsynaptic Potential ◽  
Pyloric Dilator ◽  
Muscarinic Cholinergic

The two pyloric dilator (PD) motor neurons and the single anterior burster (AB) interneuron are electrically coupled and together comprise the pacemaker for the pyloric central pattern generator of the stomatogastric ganglion of the lobster, Panulirus interruptus. Previous work (31) has shown that the AB neuron is an endogenously bursting neuron, while the PD neuron is a conditional burster. In this paper the effects of physiological inputs and neurotransmitters on isolated PD neurons and AB neurons were studied using the lucifer yellow photoinactivation technique (33). Stimulation of the inferior ventricular nerve (IVN) fibers at high frequencies elicits a triphasic response in AB and PD neurons: a rapid excitatory postsynaptic potential (EPSP) followed by a slow inhibitory postsynaptic potential (IPSP), followed by an enhancement of the pacemaker slow-wave depolarizations. Photoinactivation experiments indicate that the enhancement of the slow wave is due primarily to actions of the IVN fibers on the PD neurons but not on the AB neuron. Bath-applied dopamine dramatically alters the motor output of the pyloric system. Photoinactivation experiments show that 10(-4) M dopamine increases the amplitude and frequency of the slow-wave depolarizations recorded in the AB neurons but hyperpolarizes and inhibits the PD neurons. Bath-applied serotonin increases the frequency and amplitude of the slow-wave depolarizations in the AB neuron but has no effect on PD neurons. Pilocarpine, a muscarinic cholinergic agonist, stimulates slow-wave depolarization production in both PD neurons and the AB neuron, but the waveform and frequency of the slow waves elicited are quite different. These results show that although the electrically coupled PD and AB neurons always depolarize synchronously and act together as the pacemaker for the pyloric system, they respond differently to a neuronal input and to several putative neuromodulators. Thus, despite electrical coupling sufficient to ensure synchronous activity, the PD and AB neurons can be modulated independently.

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