Hippocampal Sclerosis in Pilocarpine Epilepsy: Survival of Peptide-Containing Neurons and Learning and Memory Disturbances in the Adult NMRI Strain Mouse

Abstract

The present experiments reveal the alterations of the hippocampal neuronal populations in chronic epilepsy. The mice were injected with a single dose of pilocarpine. They had status epilepticus and spontaneously recurrent motor seizures. Three months after pilocarpine treatment, the animals were investigated with the Barnes maze to determine their learning and memory capabilities. Their hippocampi were analyzed 2 weeks later (at 3.5 months) with standard immunohistochemical methods and cell counting. Every animal displayed hippocampal sclerosis. The neuronal loss was evaluated with neuronal-N immunostaining, and the activation of the microglia was measured with Iba1 immunohistochemistry. The neuropeptide Y, parvalbumin, and calretinin immunoreactive structures were qualitatively and quantitatively analyzed in the hippocampal formation. The results were compared statistically to the results of the control mice. We detected neuronal loss and strongly activated microglia populations. Neuropeptide Y was significantly upregulated in the sprouting axons. The number of parvalbumin- and calretinin-containing interneurons decreased significantly in the Ammon’s horn and dentate gyrus. The epileptic animals displayed significantly worse learning and memory functions. We concluded that degeneration of the principal neurons, a numerical decrease of PV-containing GABAergic neurons, and strong peptidergic axonal sprouting were responsible for the loss of the hippocampal learning and memory functions.

Interactions between astrocytes and extracellular matrix structures contribute to neuroinflammation-associated epilepsy pathology

“…Neuroinflammation and its associated changes have been found in practically every neurodegenerative disorder ( Escartin et al, 2019 ). Many studies have linked neuroinflammation with epilepsy in human patients ( Ravizza et al, 2008 ; Aronica et al, 2012 ; Gibbons et al, 2013 ; Bedner et al, 2015 ; Ferrer, 2017 ; DeSena et al, 2018 ; Wenzel et al, 2019 ; Tan et al, 2021 ; Aulická et al, 2022 ), which has been replicated by a variety of animal epilepsy models including but not limited to: traumatic brain injury (TBI) associated epilepsy ( Abdul-Muneer et al, 2016 ; Kim et al, 2016 ; Webster et al, 2017 ; Sharma et al, 2019 ; Zhou et al, 2020 ; Gao et al, 2022 ; Golub and Reddy, 2022 ), post-ischemic stroke epilepsy ( Tröscher et al, 2021 ), glioma-associated epilepsy ( Olsen and Sontheimer, 2008 ; Buckingham et al, 2011 ; Buckingham and Robel, 2013 ; MacKenzie et al, 2016 ; Tewari et al, 2018 ; Campbell et al, 2020 ; Komiyama, 2022 ), kainic acid (KA)-induced epilepsy ( Canto et al, 2022 ; Han et al, 2019 ; Huang et al, 2022 ; Hubbard et al, 2016 ; McRae et al, 2010 ; Takahashi et al, 2010 ; Wolinski et al, 2022 ; Wu, Z et al, 2021 ), pilocarpine-induced epilepsy ( Borges et al, 2003 ; Canto et al, 2022 ; Han et al, 2019 ; Kong et al, 2012 ; Mátyás, A et al, 2021 ; Ravizza et al, 2008 ; Schauwecker, 2012 ; Shapiro et al, 2008 ; Wyeth et al, 2012 ), kindling models of epilepsy ( Kołosowska et al, 2016 ; Ueno et al, 2020 ), and a β1-integrin knockout astrogliosis mouse model ( Robel et al, 2015 ). The models particularly analogous to human MTLE-HS include the pilocarpine model and the KA model, which exhibit varying degrees of HS in addition to upregulation of proteins associated with immune responses and inflammation (…”

The recycling of AMPA receptors/GABAa receptors is related to neuronal excitation/inhibition imbalance and may be regulated by KIF5A

“…On the 8th day of the culture, the neurons were divided into the Ctl and Mg 2+ -free extracellular fluid groups. The neurons in the Ctl group were exposed to a normal extracellular solution consisting of (in mM) NaCl [145], KCl [2.5], HEPES [10], CaCl 2 [2], glucose [10], glycine [0.002], and MgCl 2 [1]. Conversely, the neurons in the Mg 2+ -free extracellular fluid group were exposed to a normal extracellular solution consisting of (in mM) NaCl [145], KCl [2.5], HEPES [10], CaCl 2 [2], glucose [10], and glycine [0.002] for 3 hours.…”

“…The action potentials (Aps) were obtained by whole-cell patch-clamp recording with a Digidata 1550B patch-clamp amplifier, Axon Digidata 1550B 16-bit data acquisition system, and pClamp 10.7 data acquisition software. All the recordings were performed in an extracellular recording solution containing (in mM) NaCl [122], KCl [2], HEPES [25], CaCl 2 [2], MgCl 2 [4], and glucose [10] with a pH of 7.4. The recordings were obtained using patch electrodes (with a resistance of 3-6 MΩ) filled with an intracellular solution containing (in mM) KCl [110], NaCl [1], EGTA [2], HEPES [25], Mg-ATP [4], Na 2-GTP [0.3], and phosphocreatine [10] with a pH of 7.3.…”

“…All the recordings were performed in an extracellular recording solution containing (in mM) NaCl [122], KCl [2], HEPES [25], CaCl 2 [2], MgCl 2 [4], and glucose [10] with a pH of 7.4. The recordings were obtained using patch electrodes (with a resistance of 3-6 MΩ) filled with an intracellular solution containing (in mM) KCl [110], NaCl [1], EGTA [2], HEPES [25], Mg-ATP [4], Na 2-GTP [0.3], and phosphocreatine [10] with a pH of 7.3. Wholecell recordings were used, and the APs were recorded with a clamping voltage of -70 mV.…”

“…E/I imbalance is a well-recognized factor in seizures ( 1 ). Recurrent seizures can cause hippocampal sclerosis which could lead to cognitive impairment ( 2 ). The longer the E/I imbalance would lead to Status epilepticus (SE), which is a neurological emergency ( 3 , 4 ).…”