• The Korean Journal of Physiology and Pharmacology
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• v.2 no.3
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• pp.287-295
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• 1998

Diazepam is known to have cardiovascular depressive effects through a combined action on benzodiazepinergic receptor and the GABA receptor-chloride ion channel complex. Moreover, it is known that barbiturates also have some cardiovascular regulatory effects mediated by the central GABAergic system. Therefore, this study was undertaken to delineate the regulatory actions and interactions of these systems by measuring the responses of the cardiovascular system and renal nerve activity to muscimol, diazepam and pentobarbital, administered intracerebroventricularly in rabbits. When muscimol $(0.03{\sim}0.3\;{\mu}\;g/kg)$, diazepam $(10{\sim}100\;{\mu}\;g/kg)$ and pentobarbital $(1{\sim}10\;{\mu}\;g/kg)$ were injected into the lateral ventricle of the rabbit brain, there were similar dose-dependent decreases in blood pressure (BP) and renal nerve activity (RNA). The relative potency of the three drugs in decreasing BP and RNA was muscimol ＞ pentobarbital ＞ diazepam. Muscimol and pentobarbital also decreased the heart rate in a dose-dependent manner; however, diazepam produced a trivial, dose-independent decrease in heart rate. Diazepam $(30\;{\mu}g/kg)$ augmented the effect of muscimol $(0.1\;{\mu}g/kg)$ in decreasing blood pressure and renal nerve activity, but pentobarbital $(3\;{\mu}g/kg)$ did not. Bicuculline $(0.5\;{\mu}g/kg)$, a GABAergic receptor blocker, significantly attenuated the effect of muscimol in decreasing BP and RNA, either alone or with diazepam, and that of pentobarbital in decreasing BP and RNA, either alone or with muscimol. We inferred that the central benzodiazepinergic and barbiturate systems help regulate peripheral cardiovascular function by modulating the GABAergic system, which adjusts the output of the vasomotor center and hence controls peripheral sympathetic tone. Benzodiazepines more readily modulate the GABAergic system than barbiturates.

• The Korean Journal of Pharmacology
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• v.29 no.1
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• pp.23-32
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• 1993

Recent studies have shown that a GABAergic mechanism in the brain modulates arterial blood pressure (BP) through alterations of sympathetic activity in the brain. The purpose of the present study was to determine if this modulation is involved in the pressor response to raised intracranial pressure (ICP). The pressor response to raised ICP was abolished by pretreatment of anesthetized rabbits with intracerebroventricular (icv) muscimol (a GABA agonist) as well as with icv clonidine $(an\;{\alpha}_2-agonist)$. Raising ICP in the hypertensive state after icv yohimbine $(an\;{\alpha}_2-antagonist)$ did not cause an additional increase in the BP, whereas raising ICP in the hypertensive state following icv bicuculline (a GABA antagonist) produced a further increase. Bicuculline produced an increase of the BP which had been lowered by muscimol or by clonidine, whereas it failed to increase the hypertensive state induced by either previous yohimbine or raised ICP. Yohimbine reversed the BP which had been made low by clonidine but was incapable of raising the hypotensive state after muscimol. Yohimbine failed to increase the heightened BP due to raised ICP, whereas bicuculline-induced pressor state was further elevated by yohimbine. Muscimol, besides the bicuculline-antagonizing property, inhibited the pressor response to yohimbine, suggesting participation of a GABAergic mechanism in the pressor action of yohimbine. From these results it was inferred that there were three ways in which BP could be increased via raised ICP: inactivation of the inhibitory sympathetic activity through (1) ${\alpha}_{2}-adrenoceptors$, (2) bicuculline-sensitive GABA receptors, (3) yohimbine-sensitive, clonidine-acting GABAergic sites.

• The Korean Journal of Pain
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• v.36 no.4
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• pp.425-440
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• 2023

Background: Muscimol's quick onset and GABAergic properties make it a promising candidate for the treatment of pain. This systematic review and meta-analysis of preclinical studies aimed at summarizing the evidence regarding the efficacy of muscimol administration in the amelioration of nerve injury-related neuropathic pain. Methods: Two independent researchers performed the screening process in Medline, Embase, Scopus and Web of Science extracting data were extracted into a checklist designed according to the PRISMA guideline. A standardized mean difference (SMD [95% confidence interval]) was calculated for each. To assess the heterogeneity between studies, ² and chi-square tests were utilized. In the case of heterogeneity, meta-regression and subgroup analyses were performed to identify the potential source. Results: Twenty-two articles met the inclusion criteria. Pooled data analysis showed that the administration of muscimol during the peak effect causes a significant reduction in mechanical allodynia (SMD = 1.78 [1.45-2.11]; P < 0.0001; I² = 72.70%), mechanical hyperalgesia (SMD = 1.62 [1.28-1.96]; P < 0.0001; I² = 40.66%), and thermal hyperalgesia (SMD = 2.59 [1.79-3.39]; P < 0.0001; I² = 80.33%). This significant amendment of pain was observed at a declining rate from 15 minutes to at least 180 minutes post-treatment in mechanical allodynia and mechanical hyperalgesia, and up to 30 minutes in thermal hyperalgesia (P < 0 .0001). Conclusions: Muscimol is effective in the amelioration of mechanical allodynia, mechanical hyperalgesia, and thermal hyperalgesia, exerting its analgesic effects 15 minutes after administration for up to at least 3 hours.

• 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 Yeungnam Medical Science
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• v.8 no.2
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• pp.95-105
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• 1991

This study was designed to investigate the effect of GABA and related substances on the spontaneous contraction of rat small intestine. The rats(Sprague-Dawley), weighing 200-250g, were sacrificed by cervical dislocation, and the small intestine was isolated. Longitudinal muscle strips from duodenum, jejunum and ileum were suspended in Biancani's isolated muscle chambers and myographied isometrically. GABA and muscimol, a GABA A receptor agonist relaxed the duodenum and jejunum significantly, but baclofen-induced relaxation in those muscle strips was negligible. The effectiveness of GABA and muscimol in various regions were the greatest on duodenum, and greater on jejunum than on ileum The effect of GABA and muscimol was antagonized by bicuculline, a compeptitive GABA A receptor antagonist and picrotoxin, a noncomptitive GABA A receptor antagonist. Duodenal relaxation induced by GABA and muscimol was unaffected by hexamethonium, but was prevented by tetrodotoxin. These results suggest that GABA inhibit the contractility of smooth muscle with distinct regional difference of efficacy, and the site of inhibitory action is the GABA A receptor existing at the presynaptic membrane of postganglionic excitatory nerves.

• YAKHAK HOEJI
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• v.36 no.5
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• pp.496-505
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• 1992

The correlation between GABA receptors($GABA_A$ and $GABA_B$ receptor) and benzodiazepine receptor on the saline infusion-induced micturition reflex contraction was studied in the female rat. To investigate the effect of ${\gamma}-aminobutyric$ acid(GABA) on the micturition reflex, exogenous GABA(10 mg/kg) and GABA transaminase inhibitor(aminooxyacetic acid; AOAA $1\;{\mu}g$) were administered intravenously(i.v.) and intracerebroventriculary(i.c.v.), respectively. In result, both GABA and AOAA inhibited the saline induced micturition reflex contraction. This AOAA induced inhibition of micturition reflex was blocked by both bicuculine. $GABA_A$ receptor antagonist, and Ro 15-1788, benzodiazepine receptor antagonist. Muscimol, $GABA_A$ receptor antagonist($0.1\;{\mu}g$ i.c.v., $3\;{\mu}g$ intrathecal; i.t., 1 mg/kg i.v.) and baclofen, $GABA_A$ receptor agonist($1\;{\mu}g$ i.c.v., $3\;{\mu}g$ i.t., 1 mg/kg i.v.) also inhibited the bladder contraction. Pretreatment of bicuculline($1\;{\mu}g$ i.c.v.), but not of 5-aminovaleric acid(AVA, $1\;{\mu}g$ i.c.v.), $GABA_B$ receptor antagonist blocked the central inhibition of muscimol. These inhibitory effects were reversed by Ro15-1788 but were potentiated by flurazepam, benzodiazepine receptor antagonist. On the other hand, the inhibitory effects of baclofen were not affected by Ro 15-1788. Diazepam and flurazepam also inhibited the micturition reflex contraction when they were administered $3\;{\mu}g$ i.c.v., $10\;{\mu}g$ i.t., $10\;{\mu}M$, $30\;{\mu}M$ transurethrally, respectively. In conclusion, these results suggest that the micturition reflex is mediated by $GABA_A$, $GABA_B$ receptor and benzodiazepine receptor. The bezodiazepines increase the receptor binding of GABA to the $GABA_A$ receptor, so that the benzodiiazepines show the synergistic effect on the inhibition of the micturition reflex contraction, but not to the $GABA_B$ receptor.

• Journal of Yeungnam Medical Science
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• v.9 no.2
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• pp.382-395
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• 1992

GABA is an inhibitory neurotransmitter in central nervous system and produce sedative, antianxiety and muscle reaxing effects via $GABA_A$ receptor or $GABA_B$ receptor. Recently it is known that GABA is widely distributed throughout peripheral organs and may playa physiological role in certain organ. The vas deferens is innervated by species-difference. These study, therefore, was performed to investigate the mode and the mechanism of action of GABA on the norepiniphrine-, ATP- and electric stimulation-induced contraction of vas deferens of rat. Sprague-Dawley rats were sacrificed by cervical dislocation. The smooth muscle strips were isolated from the prostastic portion and were mounted in the isolated muscle bath. PSS in the bath was aerated with 95/5%-$O_2/CO_2$ at $33^{\circ}C$. Muscle tensions were measured by isometric tension transducer and were recorded by biological recording system. 1. GABA, muscimol, a $GAB_A$ agonist, and baclofen, a $GABA_B$ agonist inhibited the electric field stimulation(EFS, 0.2Hz, 1mSec, 80 V, monophasic square wave)-induced contraction with a rank order of potency of GABA greater than baclofen greater than muscimol. 2. The inhibitory effect of GABA was antagonized by delta aminovaleric acid(DAVA), a $GABA_B$ antagonist, but not by bicuculline, a $GABA_A$ mtagonist. 3. The inhibitory effect of baclofen was antagonized by DAVA, but the effect of muscimol was not antagonized by bicuculline. 4. Exogenous norepinephrine(NE) and ATP contracted muscle strip concentration dependently, but the effect of acetylcholine was negligible : and GABA did not affect the NE-and ATP-induced contractions. 5. GABA, baclofen and muscimol did not affect basal tone, and GABA did not affect the NE-and ATP-induced contractionsm 6. EFS-induced contraction was including 2 distinctable components. The first phasic component was inhibited by beta gamma-methylene ATP(mATP), a desensitizing agent of APT receptor and the second tonic component was reduced by pretreatment of reserpine(3 mg/Kg, IP). 7. GABA inhibited the EFS-induced contraction of reserpinized strips, but not the mATP-treated strips. These results suggest that in the prostatic portion of the rat vas deferens, adrenergic and purinergic neurotransmissions are exist, and GABA inhibits the release of ATP via presynaptic $GABA_B$ receptor on the excitatory neurons.

• The Korean Journal of Pain
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• v.19 no.1
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• pp.22-32
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• 2006

Background: This study was conducted to investigate the roles of the spinal and peripheral ${\gamma}$-aminobutyric acid (GABA)- ergic systems for the mechanical hypersensitivity produced by chronic compression of the dorsal root ganglion (CCD). Methods: CCD was performed at the left 5th lumbar dorsal root ganglion. The paw withdrawal threshold (PWT) to von Frey stimuli was measured. The mechanical responsiveness of the lumbar dorsal horn neurons was examined. GABAergic drugs were delivered with intrathecal (i.t.) or intraplantar (i.pl.) injection or by topical application onto the spinal cord. Results: CCD produced mechanical hypersensitivity, which was evidenced by the decrease of the PWT, and it lasting for 10 weeks. For the rats showing mechanical hypersensitivity, the mechanical responsiveness of the lumbar dorsal horn neurons was enhanced. A similar increase was observed with the normal lumbar dorsal horn neurons when the GABA-A receptor antagonist bicuculline was topically applied. An i.t. injection of GABA-A or GABA-B receptor agonist, muscimol or baclofen, alleviated the CCD-induced hypersensitivity. Topical application of same drugs attenuated the CCD-induced enhanced mechanical responsiveness of the lumbar dorsal horn neurons. CCD-induced hypersensitivity was also improved by low-dose muscimol applied (i.pl.) into the affected hind paw, whereas no effects could be observed with high-dose muscimol or baclofen. Conclusions: The results suggest that the neuropathic pain associated with compression of the dorsal root ganglion is caused by hyperexcitability of the dorsal horn neurons due to a loss of spinal GABAergic inhibition. Peripheral application of low-dose GABA-A receptor agonist can be useful to treat this pain.

• Natural Product Sciences
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• v.18 no.2
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• pp.67-75
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• 2012

Zizyphi Spinosi Semen (ZSS) have been widely used for the treatment of insomnia in Asia. This experiment was performed to investigate whether methanol extract of ZSS (MEZSS) has hypnotic effects through the ${\gamma}$-amino butyric acid (GABA)ergic systems. MEZSS inhibited the locomotor activity. MEZSS enhanced pentobarbital-induced sleep behaviors. However, MEZSS itself did not induce sleep at higher dose, similar to muscimol. On the other hand, both pentobarbital and MEZSS increased the non rapid eye move (NREM) sleep, especially reducing the -wave electroencephalogram (EEG) activity in REM sleep. MEZSS showed similar effects with muscimol on potentiating chloride influx induced by pentobarbital. MEZSS significantly increased GABAA receptors ${\gamma}$-subunit expression and slightly decreased ${\beta}$-subunit expression in hypothalamus and thalamus, showing that subunit-expression was similar to diazepam. In addition, MEZSS enhanced the expression of glutamic acid decarboxylase (GAD). In conclusion, it is suggested that MEZSS might augment pentobarbital-induced sleep behaviors through the modification of GABAergic systems.

• Proceedings of the Ginseng society Conference
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• 2002.10a
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• pp.96-112
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• 2002

In the present study, we have investigated the effects of centrally administered ginsenoside Rc or Rgl on the modulation of NMDA receptor and $GABA_A$ receptor binding in rat brain. The NMDA receptor binding was analyzed by quantitative autoradiography using $[^3H]MK-801$ binding, and $GABA_A$ receptor bindings were analyzed by using $[^3H]muscimol\;and\;[^3H]flunitrazepam$ in rat brain slices. Rats were infused with ginsenoside Rc or Rg1 ($10\;{\mu}g/10{\mu}l/hr$, i.c.v.) for 7 days, through pre-implanted cannula by osmotic minipumps (Alzet, model 2ML), The levels of $[^3H]MK-801$ binding were highly decreased in part of cortex and cingulated by ginsenoside Rc and Rgl. The levels of $[^3H]muscimol$ binding were strongly elevated in almost all regions of frontal cortex by the treatment of ginseoside Rc but decreased by ginsenoside Rg 1. However, the $[^3H]flunitrazepam$ binding was not modulated by ginsenoside Rc or ginsenoside Rgl infusion. These results suggest that prolonged infusion of ginsenoside could differentially modulate $[^3H]MK-801\;and\;[^3H]muscimol$ binding in a region-specific manner. Also, we investigated the influence of centrally administered ginsenoside on the regulation of mRNA levels of the family of NMDA receptor subtypes (NR1, NR2A, NR2B, NR2C) by in situ hybridization histochemistry in the rat brain. The level of NR1 mRNA is significantly increased in temporal cortex, caudate putamen, hippocampus, and granule layer of cerebellum in Rgl-infused rats as compared to control group. The level of NR2A mRNA is elevated in the frontal cortex. In contrast, it was decreased in CAI area of hippocampus in Rgl-infused rats. However, there was no significant change of NR1 and NR2A mRNA levels in Rc-infused rats. The level of NR2B mRNA is elevated in cortex, caudate putamen, and thalamus in both Rc- and Rg-infused rats. In contrast, NR2B level is decreased in CA3 in Rgl-infused rats. The level of NR2C mRNA is increased in the granule layer of cerebellum in only Rg1 but not Rc infused rats. These results show that structure difference of ginsenoside may diversely affect the modulation of expression of NMDA receptor subunit mRNA after infusion into cerebroventricle in rats.