scholarly journals Dentate Granule Cells Recruited in the Home Environment Display Distinctive Properties

2021 ◽  
Vol 14 ◽  
Author(s):  
Claire Pléau ◽  
Angélique Peret ◽  
Edouard Pearlstein ◽  
Thomas Scalfati ◽  
Alexandre Vigier ◽  
...  
Keyword(s):  
Home Environment ◽  
Home Cage ◽  
Granule Cells ◽  
Ex Vivo ◽  
Dendritic Tree ◽  
Input Resistance ◽  
Dentate Granule Cells ◽  
Shunting Inhibition ◽  
Cage Condition ◽  
Functional Features

The dentate granule cells (DGCs) play a crucial role in learning and memory. Many studies have described the role and physiological properties of these sparsely active neurons using different behavioral contexts. However, the morpho-functional features of DGCs recruited in mice maintained in their home cage (without training), considered as a baseline condition, have not yet been established. Using fosGFP transgenic mice, we observed ex vivo that DGCs recruited in animals maintained in the home cage condition are mature neurons that display a longer dendritic tree and lower excitability compared with non-activated cells. The higher GABAA receptor-mediated shunting inhibition contributes to the lower excitability of DGCs activated in the home environment by shifting the input resistance towards lower values. Remarkably, that shunting inhibition is neither observed in non-activated DGCs nor in DGCs activated during training in virtual reality. In short, our results suggest that strong shunting inhibition and reduced excitability could constitute a distinctive neural signature of mature DGCs recruited in the context of the home environment.

scholarly journals Mature dentate granule cells show different intrinsic properties depending on the behavioral context of their activation

2018 ◽  
Author(s):  
Angélique Peret ◽  
Claire Pléau ◽  
Edouard Pearlstein ◽  
Thomas Scalfati ◽  
Geoffrey Marti ◽  
...  
Keyword(s):  
Transgenic Mice ◽  
Home Cage ◽  
Granule Cells ◽  
Ex Vivo ◽  
Spatial Navigation ◽  
Intrinsic Excitability ◽  
Intrinsic Properties ◽  
Behavioral Context ◽  
Dentate Granule Cells ◽  
Neural Signature

AbstractThe dentate gyrus (DG) plays a crucial role in learning, memory and spatial navigation. Only a small fraction of mature dentate granule cells (mDGCs) is active during behavior, while the large majority remains silent. To date, the properties of this active subset of neurons remain poorly investigated. Using fosGFP transgenic mice, we show ex vivo that activated mDGCs, from mice maintained in their home cage, exhibit a marked lower intrinsic excitability compared to the non-activated cells. Remarkably, activated mDGCs, from mice trained in a virtual environment, are more excitable than those from mice maintained in their home cage. Therefore, we show that activated mDGCs display different intrinsic properties and excitable states depending on the context of their activation. We propose that these properties could constitute a neural signature of cell assemblies recruited in different behavioral contexts.

Electrotonic parameters of rat dentate granule cells measured using short current pulses and HRP staining

1983 ◽  
Vol 50 (5) ◽  
pp. 1080-1097 ◽  
Author(s):  
D. Durand ◽  
P. L. Carlen ◽  
N. Gurevich ◽  
A. Ho ◽  
H. Kunov
Keyword(s):  
Time Constant ◽  
Granule Cells ◽  
Short Pulse ◽  
Dendritic Tree ◽  
Input Resistance ◽  
Synaptic Activity ◽  
Branch Points ◽  
Pulse Technique ◽  
Current Pulses ◽  
Branching Points

The passive electrotonic parameters of nerve cells in the dentate gyrus of the rat were studied in vitro. Intracellular recordings from 30 granule cells and 3 pyramidal basket cells followed by intracellular injection of horseradish peroxidase (HRP), allowed calculations of input resistance (RN), membrane time constant (tau m), electrotonic length (L), ratio of dendritic to somatic conductance (rho), membrane specific capacitance and resistance (Rm, Cm), and specific axoplasmic resistance (Ri). The analysis of the voltage decays from long saturating (100 ms) and short (0.5 ms) current pulses showed that the short-pulse method gave better resolution for the measurement of the time constants and avoided some of the time-dependent nonlinearities but required larger currents than the long pulse. Morphological analysis of 49 branching points taken from the dendritic trees of granule cells showed that the branching power, n, is equal to 1.56 +/- 0.186 and was fairly constant throughout the tree. Given the fact that all dendrites have approximately the same length and number of branch points, the granule cell dendritic tree can be meaningfully collapsed into an equivalent cable. Moreover, electrophysiological data suggested that the cable had a "sealed" end or at least a high-impedance termination. Based on an equivalent cable model with a sealed end and a lumped soma impedance, a method was implemented to analyze the multiexponential decays from hyperpolarizing current pulses and to solve the equations of the model. This was done successfully in only 40% of the cells and yielded the following mean values for L = 1.13 and rho = 7.58. From the measurements of the soma surface area (S) and the equivalent cable diameter (D), the average specific membrane parameters were calculated: Rm = 2,726 alpha x cm2, Cm = 5.24 microF/cm2, Ri = 101 alpha x cm. The input resistance and time constant of the granule cells as measured from the short-pulse technique averaged to RN 58.57 M alpha and tau m = 16.21 ms. The failure of the model to fit 60% of the cells was interpreted to be due to the presence of a somatic shunt resulting from electrode injury, tonic synaptic activity, a lower somatic membrane specific resistance, or electronic coupling.(ABSTRACT TRUNCATED AT 400 WORDS)

Transient Neurophysiological Changes in CA3 Neurons and Dentate Granule Cells After Severe Forebrain Ischemia In Vivo

1998 ◽  
Vol 80 (6) ◽  
pp. 2860-2869 ◽  
Author(s):  
T. M. Gao ◽  
E. M. Howard ◽  
Z. C. Xu
Keyword(s):  
Synaptic Transmission ◽  
Neuronal Excitability ◽  
Granule Cells ◽  
Input Resistance ◽  
Cell Types ◽  
Forebrain Ischemia ◽  
Postsynaptic Potentials ◽  
Dentate Granule Cells ◽  
Ca3 Neurons

Gao, T. M., E. M. Howard, and Z. C. Xu. Transient neurophysiological changes in CA3 neurons and dentate granule cells after severe forebrain ischemia in vivo. J. Neurophysiol. 80: 2860–2869, 1998. The spontaneous activities, evoked synaptic responses, and membrane properties of CA3 pyramidal neurons and dentate granule cells in rat hippocampus were compared before ischemia and ≤7 days after reperfusion with intracellular recording and staining techniques in vivo. A four-vessel occlusion method was used to induce ∼14 min of ischemic depolarization. No significant change in spontaneous firing rate was observed in both cell types after reperfusion. The amplitude and slope of excitatory postsynaptic potentials (EPSPs) in CA3 neurons decreased to 50% of control values during the first 12 h reperfusion and returned to preischemic levels 24 h after reperfusion. The amplitude and slope of EPSPs in granule cells slightly decreased 24–36 h after reperfusion. The amplitude of inhibitory postsynaptic potentials in CA3 neurons transiently increased 24 h after reperfusion, whereas that in granule cells showed a transient decrease 24–36 h after reperfusion. The duration of spike width of CA3 and granule cells became longer than that of control values during the first 12 h reperfusion. The spike threshold of both cell types significantly increased 24–36 h after reperfusion, whereas the frequency of repetitive firing evoked by depolarizing current pulse was decreased during this period. No significant change in rheobase and input resistance was observed in CA3 neurons. A transient increase in rheobase and a transient decrease in input resistance were detected in granule cells 24–36 h after reperfusion. The amplitude of fast afterhyperpolarization in both cell types increased for 2 days after ischemia and returned to normal values 7 days after reperfusion. The results from this study indicate that the neuronal excitability and synaptic transmission in CA3 and granule cells are transiently suppressed after severe forebrain ischemia. The depression of synaptic transmission and neuronal excitability may provide protection for neurons after ischemic insult.

Quantifying the Role of Inhibition in Associative Long-Term Potentiation in Dentate Granule Cells With Computational Models

1997 ◽  
Vol 78 (1) ◽  
pp. 103-116 ◽  
Author(s):  
William R. Holmes ◽  
William B. Levy
Keyword(s):  
Computational Models ◽  
Granule Cells ◽  
Dendritic Tree ◽  
Long Term Potentiation ◽  
Inhibitory Synapses ◽  
Shunting Inhibition ◽  
Term Potentiation ◽  
Spatial Convergence ◽  
Voltage Attenuation

Holmes, William R. and William B. Levy. Quantifying the role of inhibition in associative long-term potentiation in dentate granule cells with computational models. J. Neurophysiol. 78: 103–116, 1997. In the dentate gyrus, coactivation of a mildly strong ipsilateral perforant path (pp) input with a weak contralateral pp input will not induce associative long-term potentiation in the weak input path unless both inputs project to the same part of the molecular layer. This “spatial convergence requirement” is thought to arise from either voltage attenuation between input locations or inhibition. Simulations with a detailed model of a dentate granule cell were performed to rule out voltage attenuation and to quantify the inhibition necessary to obtain the spatial convergence requirement. Strong lateral and weak medial or strong medial and weak lateral pp input were activated eight times at 400 Hz. Calcium current through N-methyl-d-aspartate receptor channels and subsequent changes in calcium concentration and the concentration of calmodulin bound with four calcium ions ([Cal-Ca4]) in the spine head were computed for a medial and a lateral pp synapse. To satisfy the spatial convergence requirement, peak [Cal-Ca4] had to be much larger in the strongly activated path synapse than in the weakly activated path synapse. With no inhibition in the model, differences in peak [Cal-Ca4] at the two synapses were small, ruling out voltage attenuation as the explanation of the spatial convergence requirement. However, with shunting inhibition, modeled by reducing membrane resistivity to 1,600 Ω cm2 in the distal two-thirds of the dendritic tree, peak [Cal-Ca4] was 3–5 times larger in the strongly activated path synapse than in the weakly activated path synapse. The magnitude of shunting inhibition was varied to determine the level that maximized this difference in peak [Cal-Ca4]. For strong lateral and weak medial pp input, the optimal level was one that prevented the cell from firing an action potential. For strong medial and weak lateral pp input, the optimal level was one at which the cell fired two action potentials. The distribution of shunting inhibition that best satisfied the spatial convergence requirement was inhibition on the distal two-thirds of the dendritic tree with or without inhibition at the soma, with inhibition stronger in the distal third than in the middle third. It was estimated that the number of inhibitory synapses involved in the shunting inhibition should be 25–50% of the number of excitatory synapses activated by the eight-pulse, 400-Hz tetanus. This number could be 20–50% of the total number of inhibitory synapses in the distal two-thirds of the dendritic tree. The addition of a single inhibitory synapse on a dendrite had a significant effect on peak spine head [Cal-Ca4] in nearby spines. Inhibitory synapses had to be activated four or more times at 100 Hz for effective shunting to take place, and the inhibition had to begin no later than2–5 ms after the first excitatory input. The results suggest that inhibition can isolate potentiated synapses to particular dendritic domains and that the location of activated inhibitory synapses may affect potentiation of individual synapses on individual dendrites.

scholarly journals Congenital hypothyroidism impairs spine growth of dentate granule cells by downregulation of CaMKIV

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Qingying Tang ◽  
Shuxia Chen ◽  
Hui Wu ◽  
Honghua Song ◽  
Yongjun Wang ◽  
...  
Keyword(s):  
Congenital Hypothyroidism ◽  
Granule Cells ◽  
Spine Density ◽  
Drug Induced ◽  
Distinct Cell Type ◽  
Cognitive Behaviors ◽  
Dentate Granule Cells ◽  
Rat Pups ◽  
Cognitive Deficiency ◽  
Underlying Mechanisms

AbstractCongenital hypothyroidism (CH), a common neonatal endocrine disorder, can result in cognitive deficits if delay in diagnose and treatment. Dentate gyrus (DG) is the severely affected subregion of the hippocampus by the CH, where the dentate granule cells (DGCs) reside in. However, how CH impairs the cognitive function via affecting DGCs and the underlying mechanisms are not fully elucidated. In the present study, the CH model of rat pups was successfully established, and the aberrant dendrite growth of the DGCs and the impaired cognitive behaviors were observed in the offspring. Transcriptome analysis of hippocampal tissues following rat CH successfully identified that calcium/calmodulin-dependent protein kinase IV (CaMKIV) was the prominent regulator involved in mediating deficient growth of DGC dendrites. CaMKIV was shown to be dynamically regulated in the DG subregion of the rats following drug-induced CH. Interference of CaMKIV expression in the primary DGCs significantly reduced the spine density of dendrites, while addition of T3 to the primary DGCs isolated from CH pups could facilitate the spine growth of dendrites. Insights into relevant mechanisms revealed that CH-mediated CaMKIV deficiency resulted in the significant decrease of phosphorylated CREB in DGCs, in association with the abnormality of dendrites. Our results have provided a distinct cell type in hippocampus that is affected by CH, which would be beneficial for the treatment of CH-induced cognitive deficiency.

Early appearance of developmental alterations in the dendritic tree of the hippocampal granule cells in the Ts65Dn model of Down syndrome

Hippocampus ◽  
2021 ◽  
Author(s):  
Beatrice Uguagliati ◽  
Abdel‐Rahman Al‐Absi ◽  
Fiorenza Stagni ◽  
Marco Emili ◽  
Andrea Giacomini ◽  
...  
Keyword(s):  
Down Syndrome ◽  
Granule Cells ◽  
Dendritic Tree ◽  
Early Appearance
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