Hippocampal hyperactivity in a rat model of Alzheimer’s disease

AbstractNeuronal network dysfunction is a hallmark of Alzheimer’s disease (AD). However, the underlying pathomechanisms remain unknown. We analyzed the hippocampal micronetwork in a rat model of AD at an early disease stage at the beginning of extracellular amyloid beta (Aβ) deposition. We established two-photon Ca2+-imaging in vivo in the hippocampus of rats and found hyperactivity of CA1 neurons. Patch-clamp recordings in brain slices in vitro revealed changes in the passive properties and intrinsic excitability of CA1 pyramidal neurons. Furthermore, we observed increased neuronal input resistance and prolonged action potential width in CA1 pyramidal neurons. Surprisingly, all parameters measured to quantify synaptic inhibition and excitation onto CA1 pyramidal neurons were intact suggesting a cell immanent deficit. Our data support the view that altered intrinsic excitability of CA1 neurons may precede inhibitory dysfunction at an early stage of disease progression.

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Crocin attenuates the granular cells damages on the dentate gyrus and pyramidal neurons in the CA3 regions of the hippocampus and frontal cortex in the rat model of Alzheimer's disease

Journal of Chemical Neuroanatomy ◽

10.1016/j.jchemneu.2020.101837 ◽

2020 ◽

pp. 101837 ◽

Cited By ~ 1

Author(s):

Mohammadmehdi Hadipour ◽

Gholam Hossein Meftahi ◽

Mohammad Reza Afarinesh ◽

Gila Pirzad Jahromi ◽

Boshra Hatef

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Dentate Gyrus ◽

Frontal Cortex ◽

Rat Model ◽

Pyramidal Neurons ◽

Granular Cells ◽

Model Of Alzheimer’S Disease

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Reduction of Dendritic Inhibition in CA1 Pyramidal Neurons in Amyloidosis Models of Early Alzheimer’s Disease

Journal of Alzheimer s Disease ◽

10.3233/jad-200527 ◽

2020 ◽

Vol 78 (3) ◽

pp. 951-964

Author(s):

Marvin Ruiter ◽

Lotte J. Herstel ◽

Corette J. Wierenga

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Action Potentials ◽

Pyramidal Neurons ◽

Early Stage ◽

Brain Slices ◽

Pyramidal Cells ◽

Excitatory Input ◽

Aβ Oligomers ◽

Ca1 Pyramidal Neurons

Background: In an early stage of Alzheimer’s disease (AD), before the formation of amyloid plaques, neuronal network hyperactivity has been reported in both patients and animal models. This suggests an underlying disturbance of the balance between excitation and inhibition. Several studies have highlighted the role of somatic inhibition in early AD, while less is known about dendritic inhibition. Objective: In this study we investigated how inhibitory synaptic currents are affected by elevated Aβ levels. Methods: We performed whole-cell patch clamp recordings of CA1 pyramidal neurons in organotypic hippocampal slice cultures after treatment with Aβ-oligomers and in hippocampal brain slices from AppNL-F-G mice (APP-KI). Results: We found a reduction of spontaneous inhibitory postsynaptic currents (sIPSCs) in CA1 pyramidal neurons in organotypic slices after 24 h Aβ treatment. sIPSCs with slow rise times were reduced, suggesting a specific loss of dendritic inhibitory inputs. As miniature IPSCs and synaptic density were unaffected, these results suggest a decrease in activity-dependent transmission after Aβ treatment. We observed a similar, although weaker, reduction in sIPSCs in CA1 pyramidal neurons from APP-KI mice compared to control. When separated by sex, the strongest reduction in sIPSC frequency was found in slices from male APP-KI mice. Consistent with hyperexcitability in pyramidal cells, dendritically targeting interneurons received slightly more excitatory input. GABAergic action potentials had faster kinetics in APP-KI slices. Conclusion: Our results show that Aβ affects dendritic inhibition via impaired action potential driven release, possibly due to altered kinetics of GABAergic action potentials. Reduced dendritic inhibition may contribute to neuronal hyperactivity in early AD.

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Effects of Memantine on the Spontaneous Firing Frequency of CA1 Pyramidal Neurons in Intact and Alzheimer's Rats Model: An Electrophysiological Study

Basic and Clinical Neuroscience Journal ◽

10.32598/bcn.2021.1970.1 ◽

2021 ◽

Author(s):

Nastaran Zamani ◽

◽

Ahmad Ali Moazedi ◽

Mohamad Reza Afarinesh ◽

Mehdi Pourmehdi ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Pyramidal Neurons ◽

Saline Group ◽

Firing Frequency ◽

Male Rats ◽

Spontaneous Firing ◽

Ca1 Pyramidal Neurons ◽

Model Of Alzheimer’S Disease ◽

The Mean

Introduction: Memantine (MEM) is a noncompetitive NMDAR antagonist clinically used for the treatment Alzheimer’s disease (AD) in mild to severe conditions. The present study was conducted to investigate the effects of Memantine on the spontaneous firing frequency of CA1 pyramidal neurons in rats with electrical lesion of nucleus basalis magnocellularis (NBM) as an animal model of Alzheimer's disease compared with intact adult males. Methods: In this study, adult male rats were divided into two groups. Group I (Lesion NBM, n=53) includes the following subgroups: Lesion+Saline; Sham+Saline; Lesion+MEM5mg/kg; Lesion+MEM10mg/kg; Lesion+MEM20mg/kg. And Group II (Intact, n=48) include the following subgroups: Intact+Saline; Intact+MEM3mg/kg; Intact+MEM5mg/kg; Intact+MEM10mg/kg. Extracellular single unit recording (15 min baseline+105 min after MEM or saline) was performed under urethane-anesthetized rats. Results: The results showed that the mean frequency of CA1 pyramidal neurons after saline in the Lesion+Saline (P<0.001) group significantly decreases compared with the Intact+Saline and Sham+Saline groups. In addition, after saline and memantine, the mean frequency of CA1 pyramidal neurons in the Lesion+MEM10mg/kg (P<0.01) and Lesion+MEM20mg/kg (P<0.001) groups significantly increases compared with the Lesion+Saline group. In addition the mean frequencies of CA1 pyramidal neurons in the Intact+MEM10mg/kg (P<0.001) group significantly decreases compared with the intact+saline group. Conclusion: Results showed that memantine increases the electrical activity of CA1 pyramidal neurons in rats model of Alzheimer's disease. Furthermore, in intact adult male rats, it was shown that low-dose memantine contrary to its high dose not decrease the electrical activity of CA1 pyramidal neurons.

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Reduced Synaptic and Intrinsic Excitability of a Subtype of Pyramidal Neurons in the Medial Prefrontal Cortex in a Mouse Model of Alzheimer’s Disease

Journal of Alzheimer s Disease ◽

10.3233/jad-210585 ◽

2021 ◽

pp. 1-12

Author(s):

Xiao-Qin Zhang ◽

Le Xu ◽

Si-Yu Yang ◽

Lin-Bo Hu ◽

Fei-Yuan Dong ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Prefrontal Cortex ◽

Synaptic Transmission ◽

Pyramidal Neurons ◽

Intrinsic Excitability ◽

Rodent Models ◽

Morphological Complexity ◽

Sholl Analysis ◽

Model Of Alzheimer’S Disease

Background: Abnormal morphology and function of neurons in the prefrontal cortex (PFC) are associated with cognitive deficits in rodent models of Alzheimer’s disease (AD), particularly in cortical layer-5 pyramidal neurons that integrate inputs from different sources and project outputs to cortical or subcortical structures. Pyramidal neurons in layer-5 of the PFC can be classified as two subtypes depending on the inducibility of prominent hyperpolarization-activated cation currents (h-current). However, the differences in the neurophysiological alterations between these two subtypes in rodent models of AD remain poorly understood. Objective: To investigate the neurophysiological alterations between two subtypes of pyramidal neurons in hAPP-J20 mice, a transgenic model for early onset AD. Methods: The synaptic transmission and intrinsic excitability of pyramidal neurons were investigated using whole-cell patch recordings. The morphological complexity of pyramidal neurons was detected by biocytin labelling and subsequent Sholl analysis. Results: We found reduced synaptic transmission and intrinsic excitability of the prominent h-current (PH) cells but not the non-PH cells in hAPP-J20 mice. Furthermore, the function of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels which mediated h-current was disrupted in the PH cells of hAPP-J20 mice. Sholl analysis revealed that PH cells had less dendritic intersections in hAPP-J20 mice comparing to control mice, implying that a lower morphological complexity might contribute to the reduced neuronal activity. Conclusion: These results suggest that the PH cells in the medial PFC may be more vulnerable to degeneration in hAPP-J20 mice and play a sustainable role in frontal dysfunction in AD.

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