scholarly journals Plasticity of intrinsic excitability in mature granule cells of the dentate gyrus

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Jeffrey Lopez-Rojas ◽  
Martin Heine ◽  
Michael R. Kreutz
Keyword(s):  
Dentate Gyrus ◽  
Granule Cells ◽  
Intrinsic Excitability

scholarly journals Heterogeneities in intrinsic excitability and frequency-dependent response properties of granule cells across the blades of the rat dentate gyrus

2019 ◽  
Author(s):  
Poonam Mishra ◽  
Rishikesh Narayanan
Keyword(s):  
Dentate Gyrus ◽  
Temporal Summation ◽  
Granule Cells ◽  
Neuronal Morphology ◽  
Intrinsic Excitability ◽  
Activity Levels ◽  
Frequency Dependent ◽  
Information Encoding ◽  
Response Properties ◽  
Electrophysiological Properties

ABSTRACTThe dentate gyrus (DG), the input gate to the hippocampus proper, is anatomically segregated into three different sectors, namely the suprapyramidal blade, the crest region and the infrapyramidal blade. Although there are well-established differences between these sectors in terms of neuronal morphology, connectivity patterns and activity levels, differences in electrophysiological properties of granule cells within these sectors have remained unexplored. Here, employing somatic whole-cell patch-clamp recordings from the rat DG, we demonstrate that granule cells in these sectors manifest considerable heterogeneities in their intrinsic excitability, temporal summation, action potential characteristics and frequency-dependent response properties. Across sectors, these neurons showed positive temporal summation of their responses to inputs mimicking excitatory postsynaptic currents, and showed little to no sag in their voltage responses to pulse currents. Consistently, the impedance amplitude profile manifested low-pass characteristics and the impedance phase profile lacked positive phase values at all measured frequencies, voltages and for all sectors. Granule cells in all sectors exhibited class I excitability, with broadly linear firing rate profiles, and granule cells in the crest region fired significantly less action potentials compared to those in the infrapyramidal blade. Finally, we found weak pairwise correlations across the 18 different measurements obtained individually from each of the three sectors, providing evidence that these measurements are indeed reporting distinct aspects of neuronal physiology. Together, our analyses show that granule cells act as integrators of afferent information, and emphasize the need to account for the considerable physiological heterogeneities in assessing their roles in information encoding and processing.

scholarly journals Dominant role of adult neurogenesis-induced structural heterogeneities in driving plasticity heterogeneity in dentate gyrus granule cells

2021 ◽  
Author(s):  
Sameera Shridhar ◽  
Poonam Mishra ◽  
Rishikesh Narayanan
Keyword(s):  
Dentate Gyrus ◽  
Adult Neurogenesis ◽  
Granule Cells ◽  
Dominant Role ◽  
Activity Patterns ◽  
Brain Regions ◽  
Intrinsic Excitability ◽  
Context Specific ◽  
Structural Heterogeneities ◽  
Strong Relationships

ABSTRACTNeurons and synapses manifest pronounced variability in the amount of plasticity induced by identical activity patterns. The mechanisms underlying such plasticity heterogeneity, implicated in context-specific resource allocation during encoding, have remained unexplored. Here, we employed a systematic, unbiased, and physiologically constrained search to identify the mechanisms behind plasticity heterogeneity in dentate gyrus granule cells. We found that each of intrinsic, synaptic, and structural heterogeneities independently yielded heterogeneous plasticity profiles obtained with two different induction protocols. However, prior predictions about strong relationships between neuronal intrinsic excitability and plasticity emerged only when adult-neurogenesis-induced structural heterogeneities were accounted for. Strikingly, despite the concomitant expression of heterogeneities in structural, synaptic, and intrinsic neuronal properties, similar plasticity profiles were attainable through synergistic interactions among these heterogeneities. Importantly, consequent to strong relationships with intrinsic excitability measurements, we found that synaptic plasticity in the physiological range was achieved in immature cells despite their electrophysiologically-observed weak synaptic strengths. Together, our analyses unveil the dominance of neurogenesis-induced structural heterogeneities in driving plasticity heterogeneity in granule cells. Broadly, these analyses emphasize that the mechanistic origins of and the implications for plasticity heterogeneities need quantitative characterization across brain regions, particularly focusing on context-specific encoding of learned behavior.

scholarly journals Heterogeneities in intrinsic excitability and frequency-dependent response properties of granule cells across the blades of the rat dentate gyrus

2020 ◽  
Vol 123 (2) ◽  
pp. 755-772 ◽  
Author(s):  
Poonam Mishra ◽  
Rishikesh Narayanan
Keyword(s):  
Patch Clamp ◽  
Action Potential ◽  
Dentate Gyrus ◽  
Temporal Summation ◽  
Granule Cells ◽  
Intrinsic Excitability ◽  
Frequency Dependent ◽  
Response Properties ◽  
Whole Cell Patch Clamp ◽  
Afferent Information

The dentate gyrus (DG), the input gate to the hippocampus proper, is anatomically segregated into three different sectors, namely, the suprapyramidal blade, the crest region, and the infrapyramidal blade. Although there are well-established differences between these sectors in terms of neuronal morphology, connectivity patterns, and activity levels, differences in electrophysiological properties of granule cells within these sectors have remained unexplored. Here, employing somatic whole cell patch-clamp recordings from the rat DG, we demonstrate that granule cells in these sectors manifest considerable heterogeneities in their intrinsic excitability, temporal summation, action potential characteristics, and frequency-dependent response properties. Across sectors, these neurons showed positive temporal summation of their responses to inputs mimicking excitatory postsynaptic currents and showed little to no sag in their voltage responses to pulse currents. Consistently, the impedance amplitude profile manifested low-pass characteristics and the impedance phase profile lacked positive phase values at all measured frequencies and voltages and for all sectors. Granule cells in all sectors exhibited class I excitability, with broadly linear firing rate profiles, and granule cells in the crest region fired significantly fewer action potentials compared with those in the infrapyramidal blade. Finally, we found weak pairwise correlations across the 18 different measurements obtained individually from each of the three sectors, providing evidence that these measurements are indeed reporting distinct aspects of neuronal physiology. Together, our analyses show that granule cells act as integrators of afferent information and emphasize the need to account for the considerable physiological heterogeneities in assessing their roles in information encoding and processing. NEW & NOTEWORTHY We employed whole cell patch-clamp recordings from granule cells in the three subregions of the rat dentate gyrus to demonstrate considerable heterogeneities in their intrinsic excitability, temporal summation, action potential characteristics, and frequency-dependent response properties. Across sectors, granule cells did not express membrane potential resonance, and their impedance profiles lacked inductive phase leads at all measured frequencies. Our analyses also show that granule cells manifest class I excitability characteristics, categorizing them as integrators of afferent information.

scholarly journals PKA-RIIβ autophosphorylation modulates PKA activity and seizure phenotypes in mice

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Jingliang Zhang ◽  
Chenyu Zhang ◽  
Xiaoling Chen ◽  
Bingwei Wang ◽  
Weining Ma ◽  
...  
Keyword(s):  
Therapeutic Target ◽  
Neurological Disorders ◽  
Neuronal Excitability ◽  
Granule Cells ◽  
Critical Role ◽  
Intrinsic Excitability ◽  
Seizure Susceptibility ◽  
Seizure Onset ◽  
Potential Therapeutic Target ◽  
Seizure Model

AbstractTemporal lobe epilepsy (TLE) is one of the most common and intractable neurological disorders in adults. Dysfunctional PKA signaling is causally linked to the TLE. However, the mechanism underlying PKA involves in epileptogenesis is still poorly understood. In the present study, we found the autophosphorylation level at serine 114 site (serine 112 site in mice) of PKA-RIIβ subunit was robustly decreased in the epileptic foci obtained from both surgical specimens of TLE patients and seizure model mice. The p-RIIβ level was negatively correlated with the activities of PKA. Notably, by using a P-site mutant that cannot be autophosphorylated and thus results in the released catalytic subunit to exert persistent phosphorylation, an increase in PKA activities through transduction with AAV-RIIβ-S112A in hippocampal DG granule cells decreased mIPSC frequency but not mEPSC, enhanced neuronal intrinsic excitability and seizure susceptibility. In contrast, a reduction of PKA activities by RIIβ knockout led to an increased mIPSC frequency, a reduction in neuronal excitability, and mice less prone to experimental seizure onset. Collectively, our data demonstrated that the autophosphorylation of RIIβ subunit plays a critical role in controlling neuronal and network excitabilities by regulating the activities of PKA, providing a potential therapeutic target for TLE.

Degree and pattern of calbindin immunoreactivity in granule cells of the dentate gyrus differ in mesial temporal sclerosis, cortical malformation- and tumor-related epilepsies

2011 ◽  
Vol 1399 ◽  
pp. 66-78 ◽  
Author(s):  
Hajnalka Ábrahám ◽  
Zsófia Richter ◽  
Csilla Gyimesi ◽  
Zsolt Horváth ◽  
József Janszky ◽  
...  
Keyword(s):  
Dentate Gyrus ◽  
Granule Cells ◽  
Mesial Temporal Sclerosis ◽  
Cortical Malformation
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