Role In Hyperexcitability Research Articles

Therapeutic effects of p38 mitogen-activated protein kinase inhibition on hyperexcitability of capsaicin sensitive bladder afferent neurons in mice with spinal cord injury

AimsNerve growth factor (NGF) has been implicated as a key molecule of pathology-induced changes in C-fiber afferent nerve excitability, which contributes to the emergence of neurogenic detrusor overactivity due to spinal cord injury (SCI). It is also known that the second messenger signaling pathways activated by NGF utilize p38 Mitogen-Activated Protein Kinase (MAPK). We examined the roles of p38 MAPK on electrophysiological properties of capsaicin sensitive bladder afferent neurons with SCI mice. Main methodsWe used female C57BL/6 mice and transected their spinal cord at the Th8/9 level. Two weeks later, continuous administration of p38 MAPK inhibitor (0.51 μg/h, i.t. for two weeks) was started. Bladder afferent neurons were labelled with a fluorescent retrograde tracer, Fast-Blue (FB), injected into the bladder wall three weeks after SCI. Four weeks after SCI, freshly dissociated L6-S1 dorsal root ganglion neurons were prepared and whole cell patch clamp recordings were performed in FB-labelled neurons. After recording action potentials or voltage-gated K+ currents, the sensitivity of each neuron to capsaicin was evaluated. Key findingsIn capsaicin-sensitive FB-labelled neurons, SCI significantly reduced the spike threshold and increased the number of action potentials during 800 ms membrane depolarization. Densities of slow-decaying A-type K+ (KA) and sustained delayed rectifier-type K+ (KDR) currents were significantly reduced by SCI. The reduction of KA, but not KDR, current density was reversed by the treatment with p38 MAPK inhibitor. SignificanceP38 MAPK plays an important role in hyperexcitability of capsaicin-sensitive bladder afferent neurons due to the reduction in KA channel activity in SCI mice.

The Role of Hyperexcitability in Gliomagenesis.

Glioblastoma is the most common malignant primary brain tumor. Recent studies have demonstrated that excitatory or activity-dependent signaling-both synaptic and non-synaptic-contribute to the progression of glioblastoma. Glutamatergic receptors may be stimulated via neuron-tumor synapses or release of glutamate by the tumor itself. Ion currents generated by these receptors directly alter the structure of membrane adhesion molecules and cytoskeletal proteins to promote migratory behavior. Additionally, the hyperexcitable milieu surrounding glioma increases the rate at which tumor cells proliferate and drive recurrent disease. Inhibition of excitatory signaling has shown to effectively reduce its pro-migratory and -proliferative effects.

Nerve growth factor-dependent hyperexcitability of capsaicin-sensitive bladder afferent neurones in mice with spinal cord injury.

What is the central question of this study? Nerve growth factor (NGF) is reportedly a mediator inducing urinary bladder dysfunction. Is NGF directly involved in hyperexcitability of capsaicin-sensitive C-fibre bladder afferent pathways after spinal cord injury (SCI)? What is the main finding and its importance? Neutralization of NGF by anti-NGF antibody treatment reversed the SCI-induced increase in the number of action potentials and the reduction in spike thresholds and A-type K+ current density in mouse capsaicin-sensitive bladder afferent neurones. Thus, NGF plays an important and direct role in hyperexcitability of capsaicin-sensitive C-fibre bladder afferent neurones attributable to the reduction in A-type K+ channel activity in SCI. Nerve growth factor (NGF) has been implicated as an important mediator in the induction of C-fibre bladder afferent hyperexcitability, which contributes to the emergence of neurogenic lower urinary tract dysfunction after spinal cord injury (SCI). In this study, we determined whether NGF immunoneutralization using an anti-NGF antibody (NGF-Ab) normalizes the SCI-induced changes in electrophysiological properties of capsaicin-sensitive C-fibre bladder afferent neurones in female C57BL/6 mice. The spinal cord was transected at the Th8/Th9 level. Two weeks later, continuous administration of NGF-Ab (10μgkg-1 h-1 , s.c. for 2weeks) was started. Bladder afferent neurones were labelled with Fast-Blue (FB), a fluorescent retrograde tracer, injected into the bladder wall 3weeks after SCI. Four weeks after SCI, freshly dissociated L6-S1 dorsal root ganglion neurones were prepared. Whole-cell patch-clamp recordings were then performed in FB-labelled neurones. After recording action potentials or voltage-gated K+ currents, the sensitivity of each neurone to capsaicin was evaluated. In capsaicin-sensitive FB-labelled neurones, SCI significantly reduced the spike threshold and increased the number of action potentials during membrane depolarization for 800ms. These SCI-induced changes were reversed by NGF-Ab. Densities of slow-decaying A-type K+ (KA ) and sustained delayed rectifier-type K+ currents were significantly reduced by SCI. The NGF-Ab treatment reversed the SCI-induced reduction in the KA current density. These results indicate that NGF plays an important role in hyperexcitability of mouse capsaicin-sensitive C-fibre bladder afferent neurones attributable to a reduction in KA channel activity. Thus, NGF-targeting therapies could be effective for treatment of afferent hyperexcitability and neurogenic lower urinary tract dysfunction after SCI.

PD19-10 P38 MITOGEN-ACTIVATED PROTEIN KINASE INHIBITOR REDUCES HYPEREXCITABILITY OF CAPSAICIN SENSITIVE BLADDER AFFERENT NEURONS IN MICE WITH SPINAL CORD INJURY

You have accessJournal of UrologyUrodynamics/Lower Urinary Tract Dysfunction/Female Pelvic Medicine: Basic Research & Pathophysiology I1 Apr 2018PD19-10 P38 MITOGEN-ACTIVATED PROTEIN KINASE INHIBITOR REDUCES HYPEREXCITABILITY OF CAPSAICIN SENSITIVE BLADDER AFFERENT NEURONS IN MICE WITH SPINAL CORD INJURY Takahisa Suzuki, Takahiro Shimizu, Nobutaka Shimizu, Jianshu Ni, Shinsuke Mizoguchi, Eiichiro Takaoka, Hideaki Miyake, Anthony J Kanai, and Naoki Yoshimura Takahisa SuzukiTakahisa Suzuki More articles by this author , Takahiro ShimizuTakahiro Shimizu More articles by this author , Nobutaka ShimizuNobutaka Shimizu More articles by this author , Jianshu NiJianshu Ni More articles by this author , Shinsuke MizoguchiShinsuke Mizoguchi More articles by this author , Eiichiro TakaokaEiichiro Takaoka More articles by this author , Hideaki MiyakeHideaki Miyake More articles by this author , Anthony J KanaiAnthony J Kanai More articles by this author , and Naoki YoshimuraNaoki Yoshimura More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2018.02.1000AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Nerve growth factor (NGF) has been implicated as an important mediator to induce C-fiber bladder afferent hyperexcitability, which contributes to the emergence of neurogenic detrusor overactivity following spinal cord injury (SCI). It is also known that the second messenger signaling pathways activated by NGF utilize p38 Mitogen-Activated Protein Kinase (MAPK). We examined whether p38 MAPK inhibition using SB203580 (p38 MAPK inhibitor) normalizes the SCI-induced changes in electrophysiological properties of capsaicin-sensitive C-fiber bladder afferent neurons in the mouse SCI model. METHODS The spinal cord was transected at the Th8/9 level in 8-9 weeks old female C57BL/6 mice. Two weeks later, SB203580 (1 mg/ml) was injected intrathecally using an osmotic pump at infusion rate of 0.51 µl/hr for 2 weeks. Instead of SB203580, artificial cerebrospinal fluid was injected in separate groups of spinal intact (SI) and SCI mice as controls. Bladder afferent neurons were labeled with axonal transport of Fast Blue (FB), a fluorescent retrograde tracer, injected into the bladder wall 3 weeks after SCI. Dissociated L6 and S1 dorsal root ganglion neurons were prepared 4 weeks after SCI. Whole cell patch clamp recordings were performed in FB-labeled bladder afferent neurons, and the data were compared among control SI, SCI and SCI treated with p38 MAPK inhibitor mice. After recording action potentials (AP) or voltage-gated K+ (Kv) currents, the sensitivity of each neuron to capsaicin was evaluated. RESULTS In capsaicin-sensitive bladder afferent neurons, the threshold for eliciting AP was significantly reduced in control SCI compared to SI mice. Also, SCI increased the number of AP during 800 ms membrane depolarization. These SCI induced hyperexcitability was reversed by p38 MAPK inhibitor. Densities of slow decaying KA and sustained KDR currents evoked by depolarization to 0 mV were significantly reduced after SCI. The treatment with a p38 MAPK inhibitor reversed the SCI-induced reduction in the KA current density, but not in the KDR. CONCLUSIONS In SCI mice, p38 MAPK signaling pathways play an important role in hyperexcitability of capsaicin sensitive C-fiber bladder afferent neurons due to KA current reduction. Thus, p38 MAPK-targeting therapies could be effective for treatment of afferent hyperexcitability in SCI. © 2018FiguresReferencesRelatedDetails Volume 199Issue 4SApril 2018Page: e399-e400 Advertisement Copyright & Permissions© 2018MetricsAuthor Information Takahisa Suzuki More articles by this author Takahiro Shimizu More articles by this author Nobutaka Shimizu More articles by this author Jianshu Ni More articles by this author Shinsuke Mizoguchi More articles by this author Eiichiro Takaoka More articles by this author Hideaki Miyake More articles by this author Anthony J Kanai More articles by this author Naoki Yoshimura More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

MP42-03 EFFECTS OF NERVE GROWTH FACTOR NEUTRALIZATION ON HYPEREXCITABILITY OF CAPSAICIN SENSITIVE BLADDER AFFERENT NEURONS IN MICE WITH SPINAL CORD INJURY

You have accessJournal of UrologyBladder & Urethra: Anatomy, Physiology & Pharmacology I1 Apr 2017MP42-03 EFFECTS OF NERVE GROWTH FACTOR NEUTRALIZATION ON HYPEREXCITABILITY OF CAPSAICIN SENSITIVE BLADDER AFFERENT NEURONS IN MICE WITH SPINAL CORD INJURY Takahiro Shimizu, Tsuyoshi Majima, Takahisa Suzuki, Nobutaka Shimizu, Naoki Wada, Shun Takai, Eiichiro Takaoka, Joonbeom Kwon, Pradeep Tyagi, Motoaki Saito, and Naoki Yoshimura Takahiro ShimizuTakahiro Shimizu More articles by this author , Tsuyoshi MajimaTsuyoshi Majima More articles by this author , Takahisa SuzukiTakahisa Suzuki More articles by this author , Nobutaka ShimizuNobutaka Shimizu More articles by this author , Naoki WadaNaoki Wada More articles by this author , Shun TakaiShun Takai More articles by this author , Eiichiro TakaokaEiichiro Takaoka More articles by this author , Joonbeom KwonJoonbeom Kwon More articles by this author , Pradeep TyagiPradeep Tyagi More articles by this author , Motoaki SaitoMotoaki Saito More articles by this author , and Naoki YoshimuraNaoki Yoshimura More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2017.02.1292AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Nerve growth factor (NGF) has been implicated as an important mediator to induce C-fiber bladder afferent hyperexcitability, which contributes to the emergence of neurogenic detrusor overactivity (NDO) following spinal cord injury (SCI). In this study, we examined whether NGF neutralization using anti-NGF antibody normalizes the SCI-induced changes in electrophysiological properties of capsaicin-sensitive C-fiber bladder afferent neurons in the mouse model. METHODS In female C57BL/6 mice, the spinal cord was transected at the Th8/9 level. Two weeks later, an osmotic pump was placed subcutaneously to administer anti-NGF antibody at 10 µg/kg/h for 2 weeks. Bladder afferent neurons were labeled with axonal transport of Fast Blue (FB), a fluorescent retrograde tracer, injected into the bladder wall 3 weeks after SCI. Four weeks after SCI, freshly dissociated L6-S1 dorsal root ganglion neurons were prepared. Whole cell patch clamp recordings were then performed in FB-labeled bladder afferent neurons, and the data were compared between SCI and spinal intact (SI) mice. After recording action potentials (AP) or voltage-gated K+ (Kv) currents, the sensitivity of each neuron to capsaicin was evaluated. RESULTS In capsaicin-sensitive bladder afferent neurons, the resting membrane potentials and the peak and duration of AP did not changed by SCI. On the other hand, the threshold for eliciting AP was significantly reduced in SCI vs. SI mice. Also, SCI increased the number of AP during 800 ms membrane depolarization. These SCI induced changes were reversed by NGF neutralization. SCI induced significant increases in the diameter and cell input capacitance of capsaicin-sensitive bladder afferent neurons, which were not reversed by NGF neutralization. Densities of slow decaying KA and sustained KDR currents evoked by depolarization to 0 mV were significantly reduced by SCI. NGF neutralization reversed the SCI-induced reduction in the KA current density. CONCLUSIONS In SCI mice, NGF plays an important role in hyperexcitability of capsaicin sensitive C-fiber bladder afferent neurons due to KA current reduction. Thus, NGF-targeting therapies could be effective for treatment of afferent hyperexcitability and NDO in SCI. © 2017FiguresReferencesRelatedDetails Volume 197Issue 4SApril 2017Page: e544-e545 Advertisement Copyright & Permissions© 2017MetricsAuthor Information Takahiro Shimizu More articles by this author Tsuyoshi Majima More articles by this author Takahisa Suzuki More articles by this author Nobutaka Shimizu More articles by this author Naoki Wada More articles by this author Shun Takai More articles by this author Eiichiro Takaoka More articles by this author Joonbeom Kwon More articles by this author Pradeep Tyagi More articles by this author Motoaki Saito More articles by this author Naoki Yoshimura More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Neonatal seizures and disruption to neurotransmitter systems

Neonatal seizures and disruption to neurotransmitter systems

Inhibition of the small GTPase Cdc42 in regulation of epileptic-seizure in rats

Altered expression of neuronal cytoskeletal proteins are known to play an important role in hyper-excitability of neurons in patients and animal models of epilepsy. Our previous work showed that cell division cycle 42 GTP-binding protein (Cdc42), a small GTPase of the Rho-subfamily, is significantly increased in the brain tissue of patients with temporal lobe epilepsy (TLE) and in the brain tissues of the epileptic model of rats. However, whether inhibition of Cdc42 can modify epileptic seizures has not been investigated. In this study, using a pilocarpine-induced epileptic model, we found that pretreatment with ML141, a specific inhibitor of Cdc42, reduces seizure severity. Whole-cell patch-clamp recording on CA1 pyramidal neurons in hippocampal slices from pilocarpine-induced epileptic model demonstrated that ML141 significantly inhibits the frequency of action potentials (APs), increases the amplitude and frequency of miniature inhibitory postsynaptic currents (mIPSCs), and increases the amplitude of evoked inhibitory postsynaptic currents (eIPSCs). However, ML141 did not have an impact on the miniature excitatory postsynaptic currents (mEPSCs). Our results are the first to indicate that Cdc42 plays an important role in the onset and progression of epileptic-seizures by regulating synaptic inhibition.

Distinct increased metabotropic glutamate receptor type 5 (mGluR5) in temporal lobe epilepsy with and without hippocampal sclerosis

Metabotropic glutamate receptor type 5 (mGluR5) upregulation in temporal lobe epilepsy (TLE) and the correlation of its expression with features of hippocampal sclerosis (HS) remains unclear. Here we characterized mGluR5 immunoreactivity in hippocampus, entorhinal cortex (EC), and subiculum of TLE specimens with confirmed HS, with neocortical TLE (non-HS) and necropsy controls. We correlated mGluR5 immunoreactivity with neuronal density, mossy fiber sprouting, astrogliosis (GFAP), and dendritic alterations (MAP2). TLE specimens showed increased mGluR5 expression, which was most pronounced in the EC, subiculum, CA2, and dentate gyrus outer molecular layer. Increased mGluR5 expression was seen in hippocampal head and body segments and was independent of neuronal density, astrogliosis, or dendritic alterations. Positive correlation between mGluR5 expression with mossy fiber sprouting and with MAP2 in CA3 and CA1 was found only in HS specimens. Negative correlation between mGluR5 expression with seizure frequency and epilepsy duration was found only in non-HS cases. Specimens from HS patients without previous history of febrile seizure (FS) showed higher mGluR5 and MAP2 expression in CA2. Our study suggests that mGluR5 upregulation is part of a repertoire of post-synaptic adaptations that might control overexcitation and excessive glutamate release rather than a dysfunction that leads to seizure facilitation. That would explain why non-HS cases, on which seizures are likely to originate outside the hippocampal formation, also exhibit upregulated mGluR5. On the other hand, lower mGluR5 expression was related to increased seizure frequency. In addition to its role in hyperexcitability, mGluR5 upregulation could play a role in counterbalance mechanisms along the hyperexcitable circuitry uniquely altered in sclerotic hippocampal formation. Inefficient post-synaptic compensatory morphological (dendritic branching) and glutamatergic (mGluR5 expression) mechanisms in CA2 subfield could potentially underlie the association of FS with HS and TLE. © 2013 Wiley Periodicals, Inc.

Does Epileptiform Activity Contribute to Cognitive Impairment in Alzheimer's Disease?

Alzheimer's disease is a devastating neurological disorder. The role of hyperexcitability in the disease's cognitive decline is not completely understood. In this issue of Neuron, Palop et al. report both limbic seizures and presumed homeostatic responses to seizures in an animal model of Alzheimer's.

Malevolent lurkers no more: NMDA receptors come of age

Malevolent lurkers no more: NMDA receptors come of age

Inflammatory cytokines and related genes are induced in the rat hippocampus by limbic status epilepticus.

Limbic status epilepticus was induced in rats by unilateral 60-min electrical stimulation of the CA3 region of the ventral hippocampus. As assessed by RT-PCR followed by Southern blot analysis, transcripts of interleukin-1beta, interleukin-6, interleukin-1 receptor antagonist and inducible nitric oxide synthase were significantly increased 2 h after status epilepticus in the stimulated hippocampus. Induction was maximal at 6 h for interleukin-1beta (445%), interleukin-6 (405%) and tumour necrosis factor-alpha (264%) and at 24 h for interleukin-1 receptor antagonist (494%) and inducible nitric oxide synthase (432%). In rats with spontaneous seizures (60 days after status epilepticus), interleukin-1beta mRNA was still higher than controls (241%). Immunocytochemical staining of interleukin-1beta, interleukin-6 and tumour necrosis factor-alpha was enhanced in glia with a time-course similar to that of the respective transcripts. Sixty days after status epilepticus, interleukin-1beta immunoreactivity was increased exclusively in neurons in one third of the animals. Multiple intracerebroventricular injections of interleukin-1 receptor antagonist (0.5 microg/3 microL) significantly decreased the severity of behavioural convulsions during electrical stimulation and selectively reduced tumour necrosis factor-alpha content in the hippocampus measured 18 h after status epilepticus. Thus, the induction of spontaneously recurring seizures in rats involves the activation of inflammatory cytokines and related pro- and anti-inflammatory genes in the hippocampus. These changes may play an active role in hyperexcitability of the epileptic tissue.

Alterations in NMDA receptors in a rat model of cortical dysplasia.

Recent studies have demonstrated an important role for the N-methyl-D-aspartate receptor (NMDAR) in epilepsy. NMDARs have also been shown to play a critical role in hyperexcitability associated with several animal models of human epilepsy. Using whole-cell voltage clamp recordings in brain slices, we studied evoked paroxysmal discharges in the freeze-lesion model of neocortical microgyria. The voltage dependence of epileptiform discharges indicated that these paroxysmal events were produced by a complex pattern of excitatory and inhibitory inputs. We examined the effect of the NMDAR antagonist D-2-amino-5-phosphopentanoic acid (APV) and the NMDA receptor subunit type 2B (NR2B)-selective antagonist ifenprodil on the threshold, peak amplitude, and area of evoked epileptiform discharges in brain slices from lesioned animals. Both compounds consistently raised the threshold for evoking the discharge but had modest effects on the discharge peak and amplitude. For comparison with nonlesioned cortex, we examined the effects of ifenprodil on the epileptiform discharge evoked in the presence of 2 microM bicuculline (partial disinhibition). In slices from nonlesioned cortex, 10 microM ifenprodil had little effect on the threshold whereas 71% of the recordings in bicuculline-treated lesioned cortex showed a >25% increase in threshold. These results suggest that NR2B-containing receptors are functionally enhanced in freeze-lesioned cortex and may contribute to the abnormal hyperexcitability observed in this model of neocortical microgyria.