• Nuclear Medicine and Molecular Imaging
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• v.41 no.2
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• pp.166-171
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• 2007

GABA is primary an inhibitory neurotransmitter that is localized in inhibitory interneurons. GABA is released from presynaptic terminals and functions by binding to GABA receptors. There are two types of GABA receptors, $GABA_{A}-receptor$ that allows chloride to pass through a ligand gated ion channel and $GABA_{B}-receptor$ that uses G-proteins for signaling. The $GABA_{A}$-receptor has a GABA binding site as well as a benzodiazepine binding sites, which modulate $GABA_{A}$-receptor function. Benzodiazepine GABAA receptor imaging can be accomplished by radiolabeling derivates that activates benzodiazepine binding sites. There has been much research on flumazenil (FMZ) labeled with $^{11}C-FMZ$, a benzodiazepine derivate that is a selective, reversible antagonist to GABAA receptors. Recently, $^{18}F-fluoroflumazenil$ (FFMZ) has been developed to overcome $^{11}C's$ short half-life. $^{18}F-FFMZ$ shows high selective affinity and good pharmacodynamics, and is a promising PET agent with better central benzodiazepine receptor imaging capabilities. In an epileptic focus, because the GABA/benzodiazepine receptor amount is decreased, using $^{11}C-FMZ$ PET instead of $^{18}F-FDG$ PET, restrict the foci better and may also help find lesions better than high resolution MR. $GABA_{A}$ receptors are widely distributed in the cerebral cortex, and can be used as an viable neuronal marker. Therefore it can be used as a neuronal cell viability marker in cerebral ischemia. Also, GABA-receptors decrease in areas where neuronal plasticity develops, therefore, $GAB_{A}$ imaging can be used to evaluate plasticity. Besides these usages, GABA receptors are related with psychological diseases, especially depression and schizophrenia as well as cerebral palsy, a motor-related disorder, so further in-depth studies are needed for these areas.

• Proceedings of the Korean Society of Life Science Conference
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• 2002.09a
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• pp.53-54
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• 2002

• Journal of Pharmacopuncture
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• v.19 no.2
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• pp.163-166
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• 2016

Objectives: Quercetin is a flavonoid and an important dietary constituent of fruits and vegetables. In recent years, several pharmacological activities of quercetin, such as its neuroprotective activity and, more specifically, its anti-convulsant effects in animal models of epilepsy, have been reported. This study evaluated the role of quercetin pretreatment on gene expression of ${\gamma}$-amino butyric acid type A ($GABA_A$) receptor beta subunits in kainic acid (KA)-induced seizures in mice. Methods: The animals were divided into four groups: one saline group, one group in which seizures were induced by using KA (10 mg/kg) without quercetin pretreatment and two groups pretreated with quercetin (50 and 100 mg/kg) prior to seizures being induced by using KA. Next, the messenger ribonucleic acid (mRNA) levels of the $GABA_A$ receptor ${\beta}$ subunits in the hippocampus of each animal were assessed at 2 hours and 7 days after KA administration. Quantitative real-time polymerase chain reaction (RT-PCR) assay was used to detect mRNA content in hippocampal tissues. Results: Pretreatments with quercetin at doses of 50 and 100 mg/kg prevented significant increases in the mRNA levels of the ${\beta}_1$ and the ${\beta}_3$ subunits of the $GABA_A$ receptor at 2 hours after KA injection. Pretreatment with quercetin (100 mg/kg) significantly inhibited ${\beta}_1$ and ${\beta}_3$ gene expression in the hippocampus at 7 days after KA injection. But, this inhibitory effect of quercetin at 50 mg/kg on the mRNA levels of the ${\beta}_3$ subunit of the $GABA_A$ receptor was not observed at 7 days after KA administration. Conclusion: These results suggest that quercetin (100 mg/kg) modulates the expression of the $GABA_A$ receptor ${\beta}_1$ and ${\beta}_3$ subunits in the KA model of epilepsy, most likely to prevent compensatory responses. This may be related to the narrow therapeutic dose range for the anticonvulsant activities of quercetin.

• The Korean Journal of Physiology and Pharmacology
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• v.13 no.6
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• pp.469-473
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• 2009

Induced activation of the gamma-aminobutyric $acid_A$ ($GABA_A$) receptor in the retina of goldfish caused the fish to rotate in the opposite direction to that of the spinning pattern during an optomotor response (OMR) measurement. Muscimol, a $GABA_A$ receptor agonist, modified OMR in a concentration-dependent manner. The $GABA_B$ receptor agonist baclofen and $GABA_C$ receptor agonist CACA did not affect OMR. The observed modifications in OMR included decreased anterograde rotation $(0.01\sim0.03\;{\mu}M)$, coexistence of retrograde rotation and decreased anterograde rotation $(0.1\sim30\;{\mu}M)$ and only retrograde rotation $(100\;{\mu}M\sim1\;mM)$. In contrast, the $GABA_A$ receptor antagonist bicuculline blocked muscimol-induced retrograde rotation. Based on these results, we inferred that the coding inducing retrograde movement of the goldfish retina is essentially associated with the GABAA receptor-related visual pathway. Furthermore, from our novel approach using observations of goldfish behavior the induced discrete snapshot duration was approximately 573 ms when the fish were under the influence of muscimol.

• Journal of Convergence for Information Technology
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• v.10 no.7
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• pp.116-121
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• 2020

This study was undertaken to investigate the influence and related mechanisms that have yet to be clearly demonstrated of Lithospermum erythrorhizon derived-naphthoquinone (shikonin) on the anxiety, insomnia, depression in rats. We hypothesized that naphthoquinone, the primary ingredient of Lithospermum erythrorhizon, plays a role in the modulation of insomnia evoked by stress, depression evoked by forced swimming or anxiety evoked by elevated plus maze. Male ICR (Institute of Cancer Research) mice were used and the immobility or swimming time, the duration of sleep, the duration and entry frequency into open arms were measured and recorded. The administration of naphthoquinone (10, 30 and 100 mg/kg) potentiated barbiturate-induced sleep suggesting the activation of GABAA receptor. It also potentiated the time spent in open arms of the maze and decreased the immobility time in forced swimming. In conclusion, naphthoquinone has anxiolytic, hypnotic and anti-depressant properties and is a potential therapeutic for anxiety, insomnia and depression.

• The Korean Journal of Physiology and Pharmacology
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• v.19 no.6
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• pp.523-531
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• 2015

Serotonin [5-hydroxytryptamine (5-HT)] regulates synaptic plasticity in the visual cortex. Although the effects of 5-HT on plasticity showed huge diversity depending on the ages of animals and species, it has been unclear how 5-HT can show such diverse effects. In the rat visual cortex, 5-HT suppressed long-term potentiation (LTP) at 5 weeks but enhanced LTP at 8 weeks. We speculated that this difference may originate from differential regulation of neurotransmission by 5-HT between the age groups. Thus, we investigated the effects of 5-HT on apha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)-, ${\gamma}$-aminobutyric acid receptor type A (GABAAR)-, and N-methyl-D-aspartic acid receptor (NMDAR)-mediated neurotransmissions and their involvement in the differential regulation of plasticity between 5 and 8 weeks. AMPAR-mediated currents were not affected by 5-HT at both 5 and 8 weeks. GABAAR-mediated currents were enhanced by 5-HT at both age groups. However, 5-HT enhanced NMDAR-mediated currents only at 8 weeks. The enhancement of NMDAR-mediated currents appeared to be mediated by the enhanced function of GluN2B subunit-containing NMDAR. The enhanced GABAAR- and NMDAR-mediated neurotransmissions were responsible for the suppression of LTP at 5 weeks and the facilitation of LTP at 8 weeks, respectively. These results indicate that the effects of 5-HT on neurotransmission change with development, and the changes may underlie the differential regulation of synaptic plasticity between different age groups. Thus, the developmental changes in 5-HT function should be carefully considered while investigating the 5-HT-mediated metaplastic control of the cortical network.

• Biomolecules & Therapeutics
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• v.16 no.4
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• pp.328-335
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• 2008

This study was undertaken to investigate whether honokiol could enhance the pentobarbitalinduced sleeping behaviors through $\gamma$-aminobutyric acid (GABA) receptor $Cl^-$ channel activation. Thirty minutes after the oral administration of honokiol, mice were received sodium pentobarbital (42 mg/kg, i.p.). The time elapsed from pentobarbital injection to the loss of the righting reflex was taken as sleeping latency. The time elapsed between the loss and voluntary recovery of the righting reflex was considered as the total sleeping time. Western blot technique and $Cl^-$ sensitive fluorescence probe were used to detect the expression of $GABA_A$ receptor subunits and $Cl^-$ influx in the primary cultured cerebellar granule cells. Honokiol (0.1 and 0.2 mg/kg) prolonged the sleeping time induced by pentobarbital (42 mg/kg) in a dosage-dependent manner. Honokiol (20 and 50 ${\mu}M$) increased $Cl^-$ influx in primary cultured cerebellar granule cells, and selectively increased the $GABA_A$ receptor $\alpha$-subunit expression, but had no effect on the abundance of $\beta$ or $\gamma$-subunits. Chronic treatment with 20 ${\mu}M$ honokiol in primary cultured cerebellar neurons did not affect the abundance of GAD65/67. The results suggested that honokiol could potentiate pentobarbital-induced sleeping through $GABA_A$ receptor $Cl^-$ channel activation.

• Biomolecules & Therapeutics
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• v.27 no.6
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• pp.584-590
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• 2019

Luteolin, a widespread flavonoid, has been known to have neuroprotective activity against various neurologic diseases such as epilepsy, and Alzheimer's disease. However, little information is available regarding the hypnotic effect of luteolin. In this study, we evaluated the hypnotic effect of luteolin and its underlying mechanism. In pentobarbital-induced sleeping mice model, luteolin (1, and 3 mg/kg, p.o.) decreased sleep latency and increased the total sleep time. Through electroencephalogram (EEG) and electromyogram (EMG) recording, we demonstrated that luteolin increased non-rapid eye movement (NREM) sleep time and decreased wake time. To evaluate the underlying mechanism, we examined the effects of various pharmacological antagonists on the hypnotic effect of luteolin. The hypnotic effect of 3 mg/kg of luteolin was not affected by flumazenil, a GABAA receptorbenzodiazepine (GABAAR-BDZ) binding site antagonist, and bicuculine, a GABAAR-GABA binding site antagonist. On the other hand, the hypnotic effect of 3 mg/kg of luteolin was almost completely blocked by caffeine, an antagonist for both adenosine A1 and A2A receptor (A1R and A2AR), 8-Cyclopentyl-1,3-dipropylxanthine (DPCPX), an A1R antagonist, and SCH-58261, an A2AR antagonist. From the binding affinity assay, we have found that luteolin significantly binds to not only A1R but also A2AR with $IC_{50}$ of 1.19, $0.84{\mu}g/kg$, respectively. However, luteolin did not bind to either BDZ-receptor or GABAAR. From these results, it has been suggested that luteolin has hypnotic efficacy through A1R and A2AR binding.

• Journal of Ginseng Research
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• v.44 no.1
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• pp.86-95
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• 2020

Background: Ginsenoside Rb1 (Rb1), one of the most abundant protopanaxadiol-type ginsenosides, exerts excellent neuroprotective effects even though it has low intracephalic exposure. Purpose: The present study aimed to elucidate the apparent contradiction between the pharmacokinetics and pharmacodynamics of Rb1 by studying the mechanisms underlying neuroprotective effects of Rb1 based on regulation of microflora. Methods: A pseudo germ-free (PGF) rat model was established, and neuroprotective effects of Rb1 were compared between conventional and PGF rats. The relative abundances of common probiotics were quantified to reveal the authentic probiotics that dominate in the neuroprotection of Rb1. The expressions of the gamma-aminobutyric acid (GABA) receptors, including GABAA receptors (α2, β2, and γ2) and GABAB receptors (1b and 2), in the normal, ischemia/reperfusion (I/R), and I/R+Rb1 rat hippocampus and striatum were assessed to reveal the neuroprotective mechanism of Rb1. Results: The results showed that microbiota plays a key role in neuroprotection of Rb1. The relative abundance of Lactobacillus helveticus (Lac.H) increased 15.26 fold after pretreatment with Rb1. I/R surgery induced effects on infarct size, neurological deficit score, and proinflammatory cytokines (IL-1β, IL-6, and TNF-α) were prevented by colonizing the rat gastrointestinal tract with Lac.H (1 × 10⁹ CFU) by gavage 15 d before I/R surgery. Both Rb1 and Lac.H upregulated expression of GABA receptors in I/R rats. Coadministration of a GABA_A receptor antagonist significantly attenuated neuroprotective effects of Rb1 and Lac.H. Conclusion: In sum, Rb1 exerts neuroprotective effects by regulating Lac.H and GABA receptors rather than through direct distribution to the target sites.

• Journal of Oriental Neuropsychiatry
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• v.22 no.2
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• pp.129-146
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• 2011

Objectives : The purpose of this study was to characterize the putative antidepressant and antianxiolytic effects of the 70% ethanol extract of Polygala japonica(EEPJ) using animal's behavioral experiment in mice. Methods : The effect of EEPJ on the anxioty and depressive disorder was investigated via mice's behavioral experiment like Elevated plus-maze, Horizontal wire test, Open field test, Forced swimming test, Tail suspension test, and it was happen via any mechanism by WAY 100635, a 5-HT1A receptor antagonist and by Flumazenil, a GABAA antagonist Results : 1. In the EPM, single treatments of the EEPJ(200 and 400mg/kg) had usefully antianxiolytic effects versus vehicle, which was medicated via the serotonergic nervous system. 2. In the HWT, single treatments of the EEPJ were no changes in the myorelaxant effects versus vehicle. 3. In the OFT, single treatments of the EEPJ were no changes in the locomotor activity versus vehicle. 4. In the FST, single treatments of the EEPJ(50mg/kg) significantly reduced the immobility time versus vehicle. 5. In the TST, single treatments of the EEPJ(50mg/kg) significantly reduced the immobility time versus vehicle. Conclusions : These results indicate that EEPJ is an effective antidepressant and antianxiolytic activity in mice, and it might be usefully applied for prevention and treatment of depressive disorder through evolutive study like development of various experimental models.