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Journal of Neurophysiology May 2023It is well established that dysfunctional glucose metabolism and in particular hypoglycemia can lead to hyperexcitability and exacerbate epileptic seizures. The precise...
It is well established that dysfunctional glucose metabolism and in particular hypoglycemia can lead to hyperexcitability and exacerbate epileptic seizures. The precise mechanisms behind this form of hyperexcitability are still unresolved. The present study investigates to what extent oxidative stress can account for the acute proconvulsant effect of hypoglycemia. We used the glucose derivative 2-deoxy-d-glucose (2-DG) to mimic glucose deprivation in hippocampal slices during the extracellular recording of interictal-like (IED) and seizure-like (SLE) epileptic discharge in areas CA3 and CA1. After induction of IED in area CA3 by perfusion of Cs (3 mM), MK801 (10 µM), and bicuculline (10 µM), subsequent application of 2-DG (10 mM) resulted in the appearance of SLE in 78.3% of experiments. This effect was only observed in area CA3 and was reversibly blocked by tempol (2 mM), a scavenger of reactive oxygen species, in 60% of experiments. Preincubation with tempol reduced the incidence of 2-DG-induced SLE to 40%. Low-Mg-induced SLE in area CA3 and in the entorhinal cortex (EC) was also reduced by tempol. In contrast, to the above models, which depend on synaptic transmission, nonsynaptic epileptiform field bursts induced in area CA3 by a combination of Cs (5 mM) and Cd (200 µM), or in area CA1 using the "low-Ca model," was unaffected or even enhanced by tempol. These results indicate that oxidative stress significantly contributes to 2-DG-induced seizures in area CA3 and that the impact of oxidative stress differs between synaptic and nonsynaptic ictogenesis. The main findings of the current study are that area CA3 but not area CA1 can support 2-DG-induced seizure activity, that oxidative stress significantly contributes to 2-DG-induced seizure activity in area CA3, and that the impact of oxidative stress differs between synaptic and nonsynaptic epileptiform activity. In in vitro models where ictogenesis depends on synaptic interactions, oxidative stress lowers the seizure threshold, whereas in nonsynaptic models seizure threshold is unchanged or even increased.
Topics: Humans; Epilepsy; Glucose; Hippocampus; Hypoglycemia; Oxidative Stress; Seizures
PubMed: 37017330
DOI: 10.1152/jn.00004.2023 -
Biomedical Research (Tokyo, Japan) 2023Seizure-like burst activities are induced by blockade of GABAA and/or glycine receptors in various spinal ventral roots of brainstem-spinal cord preparation from...
Seizure-like burst activities are induced by blockade of GABAA and/or glycine receptors in various spinal ventral roots of brainstem-spinal cord preparation from neonatal rodents. We found that this is not applicable to the phrenic nerve and that a new inhibitory descending pathway may suppress seizure-like activity in the phrenic nerve. Experiments were performed in brainstem-spinal cord preparation from newborn rats (age: 0-1 day). Left phrenic nerve and right C4 activities were recorded simultaneously. When GABAA and glycine receptors were blocked by 10 μM bicuculline and 10 μM strychnine (Bic+Str), seizure-like burst activities appeared in the fourth cervical ventral root (C4) but not the phrenic nerve. After making a transverse section at C1, the inspiratory burst activity disappeared from both C4 and the phrenic nerve, whereas seizure-like activity appeared in both nerves. We hypothesized that inhibitory descending pathways other than those via GABAA and/or glycine receptors (from the medulla to the spinal cord) work to avoid disturbance of regular respiratory-related diaphragm contraction by seizure-like activity. We found that cannabinoid receptor antagonist, AM251 was effective for the induction of seizure-like activity by Bic+Str in the phrenic nerve in brainstem-spinal cord preparation. Cannabinoid receptors may be involved in this descending inhibitory system.
Topics: Animals; Rats; Receptors, Glycine; Animals, Newborn; Receptors, Cannabinoid; Spinal Cord; Bicuculline; Strychnine; Seizures; Phrenic Nerve
PubMed: 37005282
DOI: 10.2220/biomedres.44.41 -
Nutrients Mar 2023Dried (Chry) flowers have been used in Korea as a traditional insomnia treatment. In this study, the sleep-promoting activity and improving sleep quality of Chry...
Dried (Chry) flowers have been used in Korea as a traditional insomnia treatment. In this study, the sleep-promoting activity and improving sleep quality of Chry extract (ext) and its active substance linarin were analyzed by pentobarbital-induced sleep experiment in mice and electroencephalography (EEG), electromyogram (EMG) analysis in rats. In a dose-dependent manner, Chry ext and linarin promoted longer sleep duration in the pentobarbital-induced sleep test compared to pentobarbital-only groups at both hypnotic and subhypnotic doses. Chry ext administration also significantly improved sleep quality, as seen in the relative power of low-frequency (delta) waves when compared with the control group. Linarin increased Cl uptake in the SH-SY5Y human cell line and chloride influx was reduced by bicuculline. After administration of Chry ext, the hippocampus, frontal cortex, and hypothalamus from rodents were collected and blotted for glutamic acid decarboxylase (GAD) and gamma-aminobutyric acid (GABA) receptors subunit expression levels. The expression of α1-subunits, β2-subunits, and GAD of the GABA receptor was modulated in the rodent brain. In conclusion, Chry ext augments pentobarbital-induced sleep duration and enhances sleep quality in EEG waves. These effects might be due to the activation of the Cl channel.
Topics: Rats; Mice; Humans; Animals; Pentobarbital; Receptors, GABA-A; Sleep Quality; Rodentia; Chlorides; Neuroblastoma; Sleep
PubMed: 36986039
DOI: 10.3390/nu15061309 -
ENeuro Apr 2023Brain stores new information by modifying connections between neurons. When new information is learnt, a group of neurons gets activated and they are connected to each...
Brain stores new information by modifying connections between neurons. When new information is learnt, a group of neurons gets activated and they are connected to each other via synapses. Dendritic spines are protrusions along neuronal dendrites where excitatory synapses are located. Dendritic spines are the first structures to protrude out from the dendrite to reach out to other neurons and establish a new connection. Thus, it is expected that neuronal activity enhances spine initiation. However, the molecular mechanisms linking neuronal activity to spine initiation are poorly known. Membrane binding BAR domain proteins are involved in spine initiation, but it is not known whether neuronal activity affects BAR domain proteins. Here, we used bicuculline treatment to activate excitatory neurons in organotypic hippocampal slices. With this experimental setup, we identified F-BAR domain containing growth arrest-specific protein (Gas7) as a novel spine initiation factor responding to neuron activity. Upon bicuculline addition, Gas7 clustered to create spine initiation hotspots, thus increasing the probability to form new spines in activated neurons. Gas7 clustering and localization was dependent on PI3-kinase (PI3K) activity and intact F-BAR domain. Gas7 overexpression enhanced N-WASP localization to clusters as well as it increased the clustering of actin. Arp2/3 complex was required for normal Gas7-induced actin clustering. Gas7 overexpression increased and knock-down decreased spine density in hippocampal pyramidal neurons. Taken together, we suggest that Gas7 creates platforms under the dendritic plasma membrane which facilitate spine initiation. These platforms grow on neuronal activation, increasing the probability of making new spines and new connections between active neurons. As such, we identified a novel molecular mechanism to link neuronal activity to the formation of new connections between neurons.
Topics: Actins; Bicuculline; Cells, Cultured; Dendritic Spines; Hippocampus; Membrane Proteins; Neurons; Synapses; Nerve Tissue Proteins
PubMed: 36963834
DOI: 10.1523/ENEURO.0344-22.2023 -
CNS Neuroscience & Therapeutics Jul 2023Beyond digestion, bile acids have been recognized as signaling molecules with broad paracrine and endocrine functions by activating plasma membrane receptor (Takeda G...
AIMS
Beyond digestion, bile acids have been recognized as signaling molecules with broad paracrine and endocrine functions by activating plasma membrane receptor (Takeda G protein-coupled receptor 5, TGR5) and the nuclear farnesoid X receptor (FXR). The present study investigated the role of bile acids in alleviating neuropathic pain by activating TGR5 and FXR.
METHOD
Neuropathic pain was induced by spared nerve injury (SNI) of the sciatic nerve. TGR5 or FXR agonist was injected intrathecally. Pain hypersensitivity was measured with Von Frey test. The amount of bile acids was detected using a bile acid assay kit. Western blotting and immunohistochemistry were used to assess molecular changes.
RESULTS
We found that bile acids were downregulated, whereas the expression of cytochrome P450 cholesterol 7ahydroxylase (CYP7A1), a rate-limiting enzyme for bile acid synthesis, was upregulated exclusively in microglia in the spinal dorsal horn after SNI. Furthermore, the expression of the bile acid receptors TGR5 and FXR was increased in glial cells and GABAergic neurons in the spinal dorsal horn on day 7 after SNI. Intrathecal injection of either TGR5 or FXR agonist on day 7 after SNI alleviated the established mechanical allodynia in mice, and the effects were blocked by TGR5 or FXR antagonist. Bile acid receptor agonists inhibited the activation of glial cells and ERK pathway in the spinal dorsal horn. All of the above effects of TGR5 or FXR agonists on mechanical allodynia, on the activation of glial cells, and on ERK pathway were abolished by intrathecal injection of the GABA receptor antagonist bicuculline.
CONCLUSION
These results suggest that activation of TGR5 or FXR counteracts mechanical allodynia. The effect was mediated by potentiating function of GABA receptors, which then inhibited the activation of glial cells and neuronal sensitization in the spinal dorsal horn.
Topics: Mice; Animals; Hyperalgesia; Signal Transduction; Spinal Cord Dorsal Horn; Bile Acids and Salts; Neuralgia
PubMed: 36880297
DOI: 10.1111/cns.14154 -
Nature Communications Feb 2023Epilepsy is a disorder in which abnormal neuronal hyperexcitation causes several types of seizures. Because pharmacological and surgical treatments occasionally...
Epilepsy is a disorder in which abnormal neuronal hyperexcitation causes several types of seizures. Because pharmacological and surgical treatments occasionally interfere with normal brain function, a more focused and on-demand approach is desirable. Here we examined the efficacy of a chemogenetic tool-designer receptors exclusively activated by designer drugs (DREADDs)-for treating focal seizure in a nonhuman primate model. Acute infusion of the GABA receptor antagonist bicuculline into the forelimb region of unilateral primary motor cortex caused paroxysmal discharges with twitching and stiffening of the contralateral arm, followed by recurrent cortical discharges with hemi- and whole-body clonic seizures in two male macaque monkeys. Expression of an inhibitory DREADD (hM4Di) throughout the seizure focus, and subsequent on-demand administration of a DREADD-selective agonist, rapidly suppressed the wide-spread seizures. These results demonstrate the efficacy of DREADDs for attenuating cortical seizure in a nonhuman primate model.
Topics: Male; Animals; Seizures; Brain; Bicuculline; Body Fluids; GABA-A Receptor Antagonists; Macaca
PubMed: 36854724
DOI: 10.1038/s41467-023-36642-6 -
Origin of Retinal Oscillatory Potentials in the Mouse, a Tool to Specifically Locate Retinal Damage.International Journal of Molecular... Feb 2023To determine the origin of oscillatory potentials (OPs), binocular electroretinogram (ERG) recordings were performed under light and dark adaptation on adult healthy...
To determine the origin of oscillatory potentials (OPs), binocular electroretinogram (ERG) recordings were performed under light and dark adaptation on adult healthy C57BL/6J mice. In the experimental group, 1 μL of PBS was injected into the left eye, while the right eye was injected with 1 μL of PBS containing different agents: APB, GABA, Bicuculline, TPMPA, Glutamate, DNQX, Glycine, Strychnine, or HEPES. The OP response depends on the type of photoreceptors involved, showing their maximum response amplitude in the ERG induced by mixed rod/cone stimulation. The oscillatory components of the OPs were affected by the injected agents, with some drugs inducing the complete abolition of oscillations (APB, GABA, Glutamate, or DNQX), whereas other drugs merely reduced the oscillatory amplitudes (Bicuculline, Glycine, Strychnine, or HEPES) or did not even affect the oscillations (TPMPA). Assuming that rod bipolar cells (RBC) express metabotropic Glutamate receptors, GABA, GABA, and Glycine receptors and that they release glutamate mainly on Glycinergic AII amacrine cells and GABAergic A17 amacrine cells, which are differently affected by the mentioned drugs, we propose that RBC-AII/A17 reciprocal synapses are responsible for the OP generation in the ERG recordings in the mice. We conclude that the reciprocal synapses between RBC and AII/A17 are the basis of the ERG OP oscillations of the light response, and this fact must be taken into consideration in any ERG test that shows a decrease in the OPs' amplitude.
Topics: Mice; Animals; Strychnine; Bicuculline; HEPES; Mice, Inbred C57BL; Retina; Retinal Diseases; Glycine; gamma-Aminobutyric Acid; Glutamates
PubMed: 36834538
DOI: 10.3390/ijms24043126 -
Medicine Feb 2023Cerebral atherosclerosis (CA) is a chronic disease caused by multiple infarcts and atrophy causing nerve degenerative syndrome. Ginkgo Folium (GF) and Forsythiae Fructus...
BACKGROUND
Cerebral atherosclerosis (CA) is a chronic disease caused by multiple infarcts and atrophy causing nerve degenerative syndrome. Ginkgo Folium (GF) and Forsythiae Fructus (FF) have shown positive effects on vascular protection, but their relationship with CA is unclear. This study aimed to identify the potential CA targets and mechanisms of action of GF-FF, using network pharmacology.
OBJECTIVE
This study used network pharmacology and molecular docking to examine the potential targets and pharmacological mechanism of GF-FF on CA.
METHODS
Using the traditional Chinese medicine systems pharmacology database and analysis platform, components were screened and corresponding targets were predicted using boundary values and Swiss Target Prediction. Using Cytoscape 3.8.0, a network was established between GF-FF components and CA targets. We extracted disease genes and constructed a network of targets based on the protein-protein interaction networks functional enrichment analysis database. Using Metascape, the Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes of the enriched targets were determined. AutoDock Vina was used to perform molecular docking.
RESULTS
Twenty-three active ingredients of GF-FF were confirmed to treat CA, covering 109 targets, of which 48 were CA-related. Luteolin, bicuculline, sesamin, kaempferol, quercetin, and ginkgolide B were the vital active compounds, and EGFR, CYP2E1, CREB1, CYP19A1, PTGS2, PPARG, PPARA, ESR1, MMP9, MAPK14, MAPK8, and PLG were the major targets. The molecular docking showed that these compounds and targets exhibited good intercalation. These 48 protein targets produced effects on CA by modulating pathways such as "apoptosis-multiple species," "IL-17 signaling pathway," and "relaxin signaling pathway."
CONCLUSIONS
As predicted by network pharmacology, GF-FF exerts anti-tumor effects through multiple components and targets for treatment of CA, providing new clinical ideas for CA treatment.
Topics: Humans; Molecular Docking Simulation; Ginkgo biloba; Network Pharmacology; Protein Interaction Maps; Apoptosis; Drugs, Chinese Herbal; Medicine, Chinese Traditional
PubMed: 36800633
DOI: 10.1097/MD.0000000000032823 -
Neuroscience Letters Mar 2023Brown adipose tissue (BAT) activity is controlled by the sympathetic nervous system. Activation of BAT has shown significant promise in preclinical studies to elicit...
Brown adipose tissue (BAT) activity is controlled by the sympathetic nervous system. Activation of BAT has shown significant promise in preclinical studies to elicit weight loss. Since the hypothalamic paraventricular nucleus (PVN) contributes to the regulation of BAT thermogenic activity, we sought to determine the effects of electrical stimulation of the PVN as a model of deep brain stimulation (DBS) for increasing BAT sympathetic nerve activity (SNA). The rostral raphe pallidus area (rRPa) was also chosen as a target for DBS since it contains the sympathetic premotor neurons for BAT. Electrical stimulation (100 µA, 100 µs, 100 Hz, for 5 min at a 50 % duty cycle) of the PVN increased BAT SNA and BAT thermogenesis. These effects were prevented by a local nanoinjection of bicuculline, a GABA receptor antagonist. We suggest that electrical stimulation of the PVN elicited local release of GABA, which inhibited BAT sympathoinhibitory neurons in PVN, thereby releasing a restraint on BAT SNA. Electrical stimulation of the rRPa inhibited BAT thermogenesis and this was prevented by a local nanoinjection of bicuculline, suggesting that local release of GABA suppressed BAT SNA. Electrical stimulation of the PVN activates BAT metabolism via a mechanism that may include activation of local GABA receptors. These findings contribute to our understanding of the mechanisms underlying the effects of DBS in the regulation of fat metabolism and provide a foundation for further DBS studies targeting hypothalamic circuits regulating BAT thermogenesis as a therapy for obesity.
Topics: Rats; Animals; Paraventricular Hypothalamic Nucleus; Rats, Sprague-Dawley; Bicuculline; Adipose Tissue, Brown; Deep Brain Stimulation; Thermogenesis; Hypothalamus; gamma-Aminobutyric Acid; Sympathetic Nervous System
PubMed: 36792026
DOI: 10.1016/j.neulet.2023.137130 -
Frontiers in Physiology 2022The rostral ventrolateral medulla (RVLM) is an important brain region involved in both resting and reflex regulation of the sympathetic nervous system. Anatomical...
The rostral ventrolateral medulla (RVLM) is an important brain region involved in both resting and reflex regulation of the sympathetic nervous system. Anatomical evidence suggests that as a bilateral structure, each RVLM innervates sympathetic preganglionic neurons on both sides of the spinal cord. However, the functional importance of ipsilateral contralateral projections from the RVLM is lacking. Similarly, during hypotension, the RVLM is believed to rely primarily on withdrawal of tonic gamma aminobutyric acid (GABA) inhibition to increase sympathetic outflow but whether GABA withdrawal mediates increased activity of functionally different sympathetic nerves is unknown. We sought to test the hypothesis that activation of the ipsilateral contralateral RVLM produces differential increases in splanchnic adrenal sympathetic nerve activities, as representative examples of functionally different sympathetic nerves. We also tested whether GABA withdrawal is responsible for hypotension-induced increases in splanchnic and adrenal sympathetic nerve activity. To test our hypothesis, we measured splanchnic and adrenal sympathetic nerve activity simultaneously in Inactin-anesthetized, male Sprague-Dawley rats during ipsilateral or contralateral glutamatergic activation of the RVLM. We also produced hypotension (sodium nitroprusside, i.v.) before and after bilateral blockade of GABA receptors in the RVLM (bicuculline, 5 mM 90 nL). Glutamate (100 mM, 30 nL) injected into the ipsilateral or contralateral RVLM produced equivalent increases in splanchnic sympathetic nerve activity, but increased adrenal sympathetic nerve activity by more than double with ipsilateral injections contralateral injections ( < 0.05; = 6). In response to hypotension, increases in adrenal sympathetic nerve activity were similar after bicuculline ( > 0.05), but splanchnic sympathetic nerve activity responses were eliminated ( < 0.05; = 5). These results provide the first functional evidence that the RVLM has predominantly ipsilateral innervation of adrenal nerves. In addition, baroreflex-mediated increases in splanchnic but not adrenal sympathetic nerve activity are mediated by GABA receptors in the RVLM. Our studies provide a deeper understanding of neural control of sympathetic regulation and insight towards novel treatments for cardiovascular disease involving sympathetic nervous system dysregulation.
PubMed: 36733693
DOI: 10.3389/fphys.2022.1099513