scholarly journals Μελέτη της διεγερσιμότητας των πυραμιδοειδών νευρώνων της περιοχής CA1 του ιπποκάμπου

2003 ◽  
Author(s):  
Γκρέτα Βόζνιακ
Keyword(s):  
Current Pulse ◽  
Neuronal Excitability ◽  
Pyramidal Neurons ◽  
Epileptiform Activity ◽  
Input Resistance ◽  
Longitudinal Axis ◽  
Functional Differentiation ◽  
Membrane Properties ◽  
Resting Membrane Potential ◽  
Firing Characteristics

Recent reports have acknowledged the existence of functional differentiation along the longitudinal axis of the hippocampus, the ventral part being more prone to epileptogenesis. The aim of the present study was to investigate the membrane properties and firing characteristics of principal neurons of dorsal (DH) and ventral hippocampus (VH) that might account for this differentiation. Intracellular recordings were made from CA1 pyramidal neurons of DH and VH hippocampus. Resting membrane potential (DH: -64,17±0,65mV; VH: -63,84±0,82mV), input resistance (DH: 45,92±4,99ΜΩ; VH: 46,28±6,24ΜΩ), and time constant (DH: 22,11 ±1,13ms; VH: 19,32±0,87ms) did not differ between DH (n=21 and VH (n=12) neurons. Action potential (AP) parameters were measured from single AP's elicited by brief current pulse (3-1 Oms) in DH (n=7) and VH (n=7) neurons. Peak amplitude (DH: 89,71±1,99mV; VH: 80,57±1,92 mV), rise time (DH: 0,22±0,01ms; VH: 0,21±0,01ms), decay time (DH: 0,97±0,02ms: VH: 0,98±0,02ms), half width (DH: 1,31±0,07ms; VH: 1,14 ±0,03ms). However, fast afterhyperpolarizations (fAHP) following AP’s were significantly weaker in VH (-4,07±0,7mV) compared to DH (-7,53±1,16mV) neurons (p<0,05). Moreover, the 1st interspike interval (ISI; DH: 4,9±0,34ms, n=25; VH: 3,9±0,3ms, n=15) of a train of AP’s elicited by a depolarizing current pulse (500ms, 0.4nA), as well as the number of AP’s within the pulse (DH: 6,8±0,9; VH: 12,1 ±0,2), was significantly different between the two groups of neurons (p<0,05). The data suggest that the weaker fAHP in VH could underlie its higher neuronal excitability as expressed by the shorter ISI. These finding confirm and extend previous evidence for functional differentiation between DH and VH and explain, to some extend, the relatively higher tendency of VH toward epileptiform activity.

Differential Effects of Corticosterone on the Slow Afterhyperpolarization in the Basolateral Amygdala and CA1 Region: Possible Role of Calcium Channel Subunits

2008 ◽  
Vol 99 (2) ◽  
pp. 958-968 ◽  
Author(s):  
Lutz Liebmann ◽  
Henk Karst ◽  
Kyriaki Sidiropoulou ◽  
Neeltje van Gemert ◽  
Onno C. Meijer ◽  
...  
Keyword(s):  
Calcium Channel ◽  
Basolateral Amygdala ◽  
Pyramidal Neurons ◽  
Input Resistance ◽  
Calcium Currents ◽  
Membrane Properties ◽  
Resting Membrane Potential ◽  
Differential Distribution ◽  
Ca1 Region ◽  
Subunit Expression

The stress hormone corticosterone increases the amplitude of the slow afterhyperpolarization (sAHP) in CA1 pyramidal neurons, without affecting resting membrane potential, input resistance, or action potential characteristics. We here examined how corticosterone affects these properties in the basolateral amygdala (BLA). In the amygdala, corticosterone does not change the AHP amplitude, nor any of the passive and active membrane properties studied. The lack of effect on the AHP is surprising since in both areas corticosterone increases high-voltage–activated sustained calcium currents, which supposedly regulate the sAHP. We wondered whether corticosterone targets different calcium channel subunits in the two areas because currents through only one of the subunits (Cav1.3) are thought to alter the AHP amplitude. In situ hybridization studies revealed that CA1 cells express Cav1.2 and Cav1.3 subunits; corticosterone does not transcriptionally regulate Cav1.2 but increases Cav1.3 expression compared with vehicle treatment. In the BLA, Cav1.3 expression was not detectable, both after control and corticosterone treatment. Cav1.2 is moderately expressed. In a modeling study, we examined putative consequences of changes in specific calcium channel subunit expression and calcium extrusion by corticosterone for the AHP in CA1 and amygdala neurons. A differential distribution and transcriptional regulation of Cav1.2 and Cav1.3 in the CA1 area versus BLA partly explain the observed differences in AHP amplitude. The functional implication of these findings could be that stress-induced arousal of activity in the BLA is more prolonged than that in the CA1 hippocampal area, so that information with an emotional component is more effectively encoded.

scholarly journals Short-Term Epileptiform Activity Potentiates Excitatory Synapses but Does Not Affect Intrinsic Membrane Properties of Pyramidal Neurons in the Rat Hippocampus In Vitro

Biomedicines ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 1374
Author(s):  
Julia L. Ergina ◽  
Dmitry V. Amakhin ◽  
Tatyana Y. Postnikova ◽  
Elena B. Soboleva ◽  
Aleksey V. Zaitsev
Keyword(s):  
Pyramidal Neurons ◽  
Amplitude Ratio ◽  
Glutamate Release ◽  
Epileptiform Activity ◽  
Hippocampal Slices ◽  
Epileptic Seizures ◽  
Input Resistance ◽  
Membrane Properties ◽  
Intrinsic Membrane Properties

Even brief epileptic seizures can lead to activity-dependent structural remodeling of neural circuitry. Animal models show that the functional plasticity of synapses and changes in the intrinsic excitability of neurons can be crucial for epileptogenesis. However, the exact mechanisms underlying epileptogenesis remain unclear. We induced epileptiform activity in rat hippocampal slices for 15 min using a 4-aminopyridine (4-AP) in vitro model and observed hippocampal hyperexcitability for at least 1 hour. We tested several possible mechanisms of this hyperexcitability, including changes in intrinsic membrane properties of neurons and presynaptic and postsynaptic alterations. Neither input resistance nor other essential biophysical properties of hippocampal CA1 pyramidal neurons were affected by epileptiform activity. The glutamate release probability also remained unchanged, as the frequency of miniature EPSCs and the paired amplitude ratio of evoked responses did not change after epileptiform activity. However, we found an increase in the AMPA/NMDA ratio, suggesting alterations in the properties of postsynaptic glutamatergic receptors. Thus, the increase in excitability of hippocampal neural networks is realized through postsynaptic mechanisms. In contrast, the intrinsic membrane properties of neurons and the probability of glutamate release from presynaptic terminals are not affected in a 4-AP model.

scholarly journals Short-term Epileptiform Activity Potentiates Excitatory Synapses but does not Affect Intrinsic Membrane Properties of Pyramidal Neurons in the Rat Hippocampus in Vitro

2021 ◽  
Author(s):  
Julia L. Ergina ◽  
Dmitry V. Amakhin ◽  
Tatyana Y. Postnikova ◽  
Elena B. Soboleva ◽  
Aleksey V. Zaitsev
Keyword(s):  
Pyramidal Neurons ◽  
Amplitude Ratio ◽  
Glutamate Release ◽  
Epileptiform Activity ◽  
Hippocampal Slices ◽  
Epileptic Seizures ◽  
Input Resistance ◽  
Membrane Properties ◽  
Intrinsic Membrane Properties

Even brief epileptic seizures can lead to activity-dependent structural remodeling of neural circuitry. Animal models show that the functional plasticity of synapses and changes in the intrinsic excitability of neurons can be crucial for epileptogenesis. However, the exact mechanisms underlying epileptogenesis remain unclear. We induced epileptiform activity in rat hippocampal slices for 15 min using a 4-aminopyridine (4-AP) in vitro model and observed hippocampal hyperexcitability for at least 1 hour. We tested several possible mechanisms of this hyperexcitability, including changes in intrinsic membrane properties of neurons, presynaptic and postsynaptic alterations. Neither input resistance nor other essential biophysical properties of hippocampal CA1 pyramidal neurons were affected by epileptiform activity. The glutamate release probability also remained unchanged, as the frequency of miniature EPSCs and the paired amplitude ratio of evoked responses did not change after epileptiform activity. However, we found an increase in the AMPA/NMDA ratio, suggesting alterations in the properties of postsynaptic glutamatergic receptors. Thus, the increase in excitability of hippocampal neural networks is realized through postsynaptic mechanisms. In contrast, the intrinsic membrane properties of neurons and the probability of glutamate release from presynaptic terminals are not affected in a 4-AP model.

Dorsal and Ventral Distribution of Excitable and Synaptic Properties of Neurons of the Bed Nucleus of the Stria Terminalis

2003 ◽  
Vol 90 (1) ◽  
pp. 405-414 ◽  
Author(s):  
Regula E. Egli ◽  
Danny G. Winder
Keyword(s):  
Receptor Antagonist ◽  
Drugs Of Abuse ◽  
Input Resistance ◽  
Membrane Properties ◽  
Resting Membrane Potential ◽  
Stria Terminalis ◽  
Bed Nucleus ◽  
Adult Mice ◽  
Dependent Potential

The bed nucleus of the stria terminalis (BNST) is a structure uniquely positioned to integrate stress information and regulate both stress and reward systems. Consistent with this arrangement, evidence suggests that the BNST, and in particular the noradrenergic input to this structure, is a key component of affective responses to drugs of abuse. We have utilized an in vitro slice preparation from adult mice to determine synaptic and membrane properties of these cells, focusing on the dorsal and ventral subdivisions of the anterolateral BNST (dBNST and vBNST) because of the differential noradrenergic input to these two regions. We find that while resting membrane potential and input resistance are comparable between these subdivisions, excitable properties, including a low-threshold spike (LTS) likely mediated by T-type calcium channels and an Ih-dependent potential, are differentially distributed. Inhibitory and excitatory postsynaptic potentials (IPSPs and EPSPs, respectively) are readily evoked in both dBNST and vBNST. The fast IPSP is predominantly GABAA-receptor mediated and is partially blocked by the AMPA/kainate-receptor antagonist CNQX. In the presence of the GABAA-receptor antagonist picrotoxin, cells in dBNST but not vBNST are more depolarized and have a higher input resistance, suggesting tonic GABAergic inhibition of these cells. The EPSPs elicited in BNST are monosynaptic, exhibit paired pulse facilitation, and contain both an AMPA- and an N-methyl-d-aspartate (NMDA) receptor-mediated component. These data support the hypothesis that neurons of the dorsal and ventral BNST differentially integrate synaptic input, which is likely of behavioral significance. The data also suggest mechanisms by which information may flow through stress and reward circuits.

Postnatal Changes in Membrane Properties of Mice Trigeminal Ganglion Neurons

2002 ◽  
Vol 87 (5) ◽  
pp. 2398-2407 ◽  
Author(s):  
Carmen Cabanes ◽  
Mikel López de Armentia ◽  
Félix Viana ◽  
Carlos Belmonte
Keyword(s):  
Postnatal Development ◽  
Trigeminal Ganglion ◽  
Input Resistance ◽  
Membrane Capacitance ◽  
Membrane Properties ◽  
Inward Rectification ◽  
Resting Membrane Potential ◽  
Depolarization Rate ◽  
Ganglion Neurons

Intracellular recordings from neurons in the mouse trigeminal ganglion (TG) in vitro were used to characterize changes in membrane properties that take place from early postnatal stages (P0–P7) to adulthood (>P21). All neonatal TG neurons had uniformly slow conduction velocities, whereas adult neurons could be separated according to their conduction velocity into Aδ and C neurons. Based on the presence or absence of a marked inflection or hump in the repolarization phase of the action potential (AP), neonatal neurons were divided into S- (slow) and F-type (fast) neurons. Their passive and subthreshold properties (resting membrane potential, input resistance, membrane capacitance, and inward rectification) were nearly identical, but they showed marked differences in AP amplitude, AP overshoot, AP duration, rate of AP depolarization, rate of AP repolarization, and afterhyperpolarization (AHP) duration. Adult TG neurons also segregated into S- and F-type groups. Differences in their mean AP amplitude, AP overshoot, AP duration, rate of AP depolarization, rate of AP repolarization, and AHP duration were also prominent. In addition, axons of 90% of F-type neurons and 60% of S-type neurons became faster conducting in their central and peripheral branch, suggestive of axonal myelination. The proportion of S- and F-type neurons did not vary during postnatal development, suggesting that these phenotypes were established early in development. Membrane properties of both types of TG neurons evolved differently during postnatal development. The nature of many of these changes was linked to the process of myelination. Thus myelination was accompanied by a decrease in AP duration, input resistance ( R in), and increase in membrane capacitance (C). These properties remained constant in unmyelinated neurons (both F- and S-type). In adult TG, all F-type neurons with inward rectification were also fast-conducting Aδ, suggesting that those F-type neurons showing inward rectification at birth will evolve to F-type Aδ neurons with age. The percentage of F-type neurons showing inward rectification also increased with age. Both F- and S-type neurons displayed changes in the sensitivity of the AP to reductions in extracellular Ca2+ or substitution with Co2+ during the process of maturation.

Altered desensitization produces enhancement of EPSPs in neocortical neurons

1994 ◽  
Vol 72 (2) ◽  
pp. 1032-1036 ◽  
Author(s):  
M. R. Pelletier ◽  
J. J. Hablitz
Keyword(s):  
Nmda Receptors ◽  
Time Course ◽  
Glutamate Release ◽  
Epileptiform Activity ◽  
Brain Slices ◽  
Synaptic Activity ◽  
Membrane Properties ◽  
Repetitive Firing ◽  
Resting Membrane Potential ◽  
Bath Application

1. Neocortical brain slices were prepared from rats (35–50 days of age) and maintained in vitro. Intracellular recordings were obtained from neurons in cortical layers II/III. The effect of bath application of cyclothiazide (CYZ), a potent blocker of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor desensitization, on evoked synaptic activity and passive membrane properties was investigated. 2. Bath application of CYZ did not significantly affect resting membrane potential, input resistance, or repetitive firing. CYZ increased both the amplitude and duration of evoked excitatory postsynaptic potentials (EPSPs). Polysynaptic responses were also augumented. These effects persisted after the blockade of N-methyl-D-aspartate (NMDA) receptors with D-2-amino-5-phosphonovaleric acid (D-APV). The magnitude of these effects appeared to vary directly with stimulation intensity and presumably, amount of glutamate release. 3. Epileptiform activity was induced by bath application of bicuculline methiodide. The amplitude and duration of evoked paroxysmal discharges were increased by CYZ. Similar results were seen in presence of D-APV. 4. These results indicate that CYZ has significant effects on synaptic transmission. Desensitization of non-NMDA receptors may be an important mechanism for determining the time course of EPSPs and in curtailing epileptiform responses in the rat neocortex.

scholarly journals Transmitter Regulation of Plateau Properties in Turtle Motoneurons

1998 ◽  
Vol 79 (1) ◽  
pp. 45-50 ◽  
Author(s):  
Gytis Svirskis ◽  
Jørn Hounsgaard
Keyword(s):  
Membrane Potential ◽  
Metabotropic Glutamate Receptors ◽  
Input Resistance ◽  
Pattern Generation ◽  
Synaptic Activity ◽  
Membrane Properties ◽  
Resting Membrane Potential ◽  
Type I ◽  
Plateau Potentials ◽  
Inward Current

Svirskis, Gytis and Jørn Hounsgaard. Transmitter regulation of plateau properties in turtle motoneurons. J. Neurophysiol. 79: 45–50, 1998. In motoneurons, generation of plateau potentials is promoted by modulators that block potassium channels. In voltage-clamp experiments with triangular voltage ramp commands, we show that cis-(±)-1-aminocyclopentane-1,3-dicarboxylic acid ( cis-ACPD) and muscarine promote the generation of plateau potentials by increasing the dihydropyridine sensitive inward current, by increasing the input resistance, and by depolarizing the resting membrane potential. Type I metabotropic glutamate receptors (mGluR I) mediate the effects of cis-ACPD. Baclofen suppresses generation of plateau potentials by decreasing the dihydropyridine sensitive inward current, by decreasing the input resistance, and by hyperpolarizing the resting membrane potential. These results suggest that membrane properties of motoneurons are continuously modulated by synaptic activity in ways that may have profound effects on synaptic integration and pattern generation.

Effects of aging on the intrinsic membrane properties of medial NTS neurons of Fischer-344 rats

1993 ◽  
Vol 70 (5) ◽  
pp. 1975-1987 ◽  
Author(s):  
S. M. Johnson ◽  
R. B. Felder
Keyword(s):  
Action Potential ◽  
Nucleus Tractus Solitarius ◽  
Input Resistance ◽  
Membrane Properties ◽  
Repetitive Firing ◽  
Resting Membrane Potential ◽  
Fischer 344 Rats ◽  
Fischer 344 ◽  
Steady State Current ◽  
Intrinsic Membrane Properties

1. Recent studies have demonstrated that the arterial baroreflex is imparied with aging and have implicated central components of the baroreflex arc in this autonomic dysfunction. Neurons in the medial portion of the nucleus tractus solitarius (mNTS) receive a major input from the arterial baroreceptors. The present study was undertaken to characterize the intrinsic membrane properties of mNTS neurons in young rats and to test the hypothesis that these properties are altered with aging. An in vitro brain stem slice preparation was used to record intracellularly from mNTS neurons; passive membrane properties, action potential characteristics, and repetitive firing properties were examined and compared. 2. Neurons in the mNTS of young (3-5 mo old) Fischer-344 rats (F-344; n = 35) had a resting membrane potential of -57 +/- 6.9 mV (mean +/- SD), a membrane time constant of 18 +/- 9.0 ms, and an input resistance of 110 +/- 60 m omega. Action potential amplitude was 81 +/- 7.5 mV with a duration at half-height of 0.83 +/- 0.15 ms. The spontaneous firing rate in 24 cells was 4.3 +/- 2.9 Hz. The amplitude and duration of the action potential afterhyperpolarization (AHP) were 6.6 +/- 3.0 mV and 64 +/- 34 ms, respectively. All neurons expressed spike frequency adaptation, action potential AHP, and posttetanic hyperpolarization. Delayed excitation and postinhibitory rebound were present in 34 and 14% of neurons tested, respectively. Neurons from adult (10-12 mo old) F-344 rats (n = 34) were similar to the young F-344 rats with respect to all of these variables. 3. Neurons from aged (21-24 mo old) F-344 (n = 32) were similar to those from young and adult rats, but there were two potentially important differences: the mean input resistance of the aged neurons was higher (170 +/- 150 M omega), with a larger proportion (46% of aged neurons vs. 20% of young neurons and 21% of adult neurons) having input resistances > 150 M omega; and there was a tendency for a smaller percentage of aged neurons (16% of aged neurons vs. 34% of young neurons and 29% of adult neurons) to express delayed excitation. 4. The potential significance of a high input resistance was tested by comparing the steady-state current-voltage (I-V) relationships and the frequency-current (f-I) relationships among low-resistance (1-100 M omega), medium-resistance (101-200 M omega).(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Melatonin Reduces Excitability in Dorsal Root Ganglia Neurons with Inflection on the Repolarization Phase of the Action Potential

2019 ◽  
Vol 20 (11) ◽  
pp. 2611 ◽  
Author(s):  
Klausen Oliveira-Abreu ◽  
Nathalia Silva-dos-Santos ◽  
Andrelina Coelho-de-Souza ◽  
Francisco Ferreira-da-Silva ◽  
Kerly Silva-Alves ◽  
...  
Keyword(s):  
Action Potential ◽  
Dorsal Root Ganglia ◽  
Dorsal Root ◽  
Neuronal Excitability ◽  
Input Resistance ◽  
Cell Types ◽  
Neuronal Population ◽  
Resting Membrane Potential ◽  
Electrophysiological Properties ◽  
Repolarization Phase

Melatonin is a neurohormone produced and secreted at night by pineal gland. Many effects of melatonin have already been described, for example: Activation of potassium channels in the suprachiasmatic nucleus and inhibition of excitability of a sub-population of neurons of the dorsal root ganglia (DRG). The DRG is described as a structure with several neuronal populations. One classification, based on the repolarizing phase of the action potential (AP), divides DRG neurons into two types: Without (N0) and with (Ninf) inflection on the repolarization phase of the action potential. We have previously demonstrated that melatonin inhibits excitability in N0 neurons, and in the present work, we aimed to investigate the melatonin effects on the other neurons (Ninf) of the DRG neuronal population. This investigation was done using sharp microelectrode technique in the current clamp mode. Melatonin (0.01–1000.0 nM) showed inhibitory activity on neuronal excitability, which can be observed by the blockade of the AP and by the increase in rheobase. However, we observed that, while some neurons were sensitive to melatonin effect on excitability (excitability melatonin sensitive—EMS), other neurons were not sensitive to melatonin effect on excitability (excitability melatonin not sensitive—EMNS). Concerning the passive electrophysiological properties of the neurons, melatonin caused a hyperpolarization of the resting membrane potential in both cell types. Regarding the input resistance (Rin), melatonin did not change this parameter in the EMS cells, but increased its values in the EMNS cells. Melatonin also altered several AP parameters in EMS cells, the most conspicuously changed was the (dV/dt)max of AP depolarization, which is in coherence with melatonin effects on excitability. Otherwise, in EMNS cells, melatonin (0.1–1000.0 nM) induced no alteration of (dV/dt)max of AP depolarization. Thus, taking these data together, and the data of previous publication on melatonin effect on N0 neurons shows that this substance has a greater pharmacological potency on Ninf neurons. We suggest that melatonin has important physiological function related to Ninf neurons and this is likely to bear a potential relevant therapeutic use, since Ninf neurons are related to nociception.

scholarly journals Layer- and subregion-specific differences in the neurophysiological properties of rat medial prefrontal cortex pyramidal neurons

2018 ◽  
Vol 119 (1) ◽  
pp. 177-191 ◽  
Author(s):  
Chenghui Song ◽  
James R. Moyer
Keyword(s):  
Prefrontal Cortex ◽  
Medial Prefrontal Cortex ◽  
Pyramidal Neurons ◽  
Conditioned Fear ◽  
Input Resistance ◽  
Underlying Mechanism ◽  
Fear Memory ◽  
Membrane Properties ◽  
Spike Threshold ◽  
Memory Acquisition

Medial prefrontal cortex (mPFC) is critical for the expression of long-term conditioned fear. However, the neural circuits involving fear memory acquisition and retrieval are still unclear. Two subregions within mPFC that have received a lot of attention are the prelimbic (PL) and infralimbic (IL) cortices (e.g., Santini E, Quirk GJ, Porter JT. J Neurosci 28: 4028–4036, 2008; Song C, Ehlers VL, Moyer JR Jr. J Neurosci 35: 13511–13524, 2015). Interestingly, PL and IL may play distinct roles during fear memory acquisition and retrieval but the underlying mechanism is poorly understood. One possibility is that the intrinsic membrane properties differ between these subregions. Thus, the current study was carried out to characterize the basic membrane properties of mPFC neurons in different layers and subregions. We found that pyramidal neurons in L2/3 were more hyperpolarized and less excitable than in L5. This was observed in both IL and PL and was associated with an enhanced h-current in L5 neurons. Within L2/3, IL neurons were more excitable than those in PL, which may be due to a lower spike threshold and higher input resistance in IL neurons. Within L5, the intrinsic excitability was comparable between neurons obtained in IL and PL. Thus, the heterogeneity in physiological properties of mPFC neurons may underlie the observed subregion-specific contribution of mPFC in cognitive function and emotional control, such as fear memory expression. NEW & NOTEWORTHY This is the first study to demonstrate that medial prefrontal cortical (mPFC) neurons are heterogeneous in both a layer- and a subregion-specific manner. Specifically, L5 neurons are more depolarized and more excitable than those neurons in L2/3, which is likely due to variations in h-current. Also, infralimbic neurons are more excitable than those of prelimbic neurons in layer 2/3, which may be due to differences in certain intrinsic properties, including input resistance and spike threshold.

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