Effects of electroacupuncture pretreatment on GABAA receptor of fastigial nucleus and sympathetic nerve activity in rats with myocardial ischemia reperfusion injury / 中国针灸

OBJECTIVE@#To observe the effects of electroacupuncture (EA) pretreatment on cardiac function, sympathetic nerve activity, indexes of myocardial injury and GABAA receptor in fastigial nucleus in rats with myocardial ischemia reperfusion injury (MIRI), and to explore the neuroregulatory mechanism of EA pretreatment in improving MIRI.@*METHODS@#A total of 60 male SD rats were randomly divided into a sham operation group, a model group, an EA group, an agonist group and an agonist+EA group, 12 rats in each group. The MIRI model was established by ligation of the left anterior descending coronary artery. EA was applied at bilateral "Shenmen" (HT 7) and "Tongli" (HT 5) in the EA group and the agonist+EA group, with continuous wave, in frequency of 2 Hz and intensity of 1 mA, 30 min each time, once a day for 7 consecutive days. After intervention, the MIRI model was established. In the agonist group, the muscone (agonist of GABAA receptor, 1 g/L) was injected in fastigial nucleus for 7 consecutive days before modeling, 150 μL each time, once a day. In the agonist+EA group, the muscone was injected in fastigial nucleus 30 min before EA intervention. The data of electrocardiogram was collected by PowerLab standard Ⅱ lead, and ST segment displacement and heart rate variability (HRV) were analyzed; the serum levels of norepinephrine (NE), creatine kinase isoenzyme MB (CK-MB) and cardiac troponin I (cTnI) were detected by ELISA; the myocardial infarction area was measured by TTC staining; the morphology of myocardial tissue was observed by HE staining; the positive expression and mRNA expression of GABAA receptor in fastigial nucleus were detected by immunohistochemistry and real-time PCR.@*RESULTS@#Compared with the sham operation group, in the model group, ST segment displacement and ratio of low frequency to high frequency (LF/HF) of HRV were increased (P<0.01), HRV frequency domain analysis showed enhanced sympathetic nerve excitability, the serum levels of NE, CK-MB and cTnI were increased (P<0.01), the percentage of myocardial infarction area was increased (P<0.01), myocardial fiber was broken and interstitial edema was serious, the positive expression and mRNA expression of GABAA receptor in fastigial nucleus were increased (P<0.01). Compared with the model group, in the EA group, ST segment displacement and LF/HF ratio were decreased (P<0.01), HRV frequency domain analysis showed reduced sympathetic nerve excitability, the serum levels of NE, CK-MB and cTnI were decreased (P<0.01), the percentage of myocardial infarction area was decreased (P<0.01), myocardial fiber breakage and interstitial edema were lightened, the positive expression and mRNA expression of GABAA receptor in fastigial nucleus were decreased (P<0.01). Compared with the EA group, in the agonist group and the agonist+EA group, ST segment displacement and LF/HF ratio were increased (P<0.01), HRV frequency domain analysis showed enhanced sympathetic nerve excitability, the serum levels of NE, CK-MB and cTnI were increased (P<0.01), the percentage of myocardial infarction area was increased (P<0.01), myocardial fiber breakage and interstitial edema were aggravated, the positive expression and mRNA expression of GABAA receptor in fastigial nucleus were increased (P<0.01).@*CONCLUSION@#EA pretreatment can improve the myocardial injury in MIRI rats, and its mechanism may be related to the inhibition of GABAA receptor expression in fastigial nucleus, thereby down-regulating the excitability of sympathetic nerve.

Molecular modeling, synthesis, and evaluation of 1-(4-methoxybenzofuran-5-yl)-3-phenylpropane-1, 3-dione for its anxiolytic potentiality

The disabling mental illness anxiety is gradually affecting the modern society in any age group worldwide. The searchfor novel bioactive entity from herbal origin for different disorders has become the center of attraction significantlyfrom the past few decades. Gamma-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter known tobe responsible for the anxiolytic activity of most of the potent anxiolytic agents. All the available data of pongamol1-(4-methoxybenzofuran-5-yl)-3-phenylpropane-1, 3-dione (MPD) were based on natural or semi-synthetic source.The synthetic routes were using easily available source and quick, cost-effective, and high yielding process. MPD hastraditionally been acquired from natural sources mainly from the extracts of fruits of Pongamia pinnata and Pongamiaglabra, where the yield value and the yield time are the main drawbacks. Keeping in view of the above aspects in thepresent research, it was approached to synthesize and evaluate the anxiolytic potential 1-(methoxybenzofuran-5yl)-3-phenylpropane-1, 3-dione on experimental animals and docking procedure after its synthesis. The study of MPDon the gross behavior of mice showed a significant Central Nervous System (CNS) depressant effect. Furthermore,its anxiolytic activity was confirmed by observing its reduced locomotion of mice using actophotometer and elevatedplus-maze apparatus. The highest docking score was observed to be −3.22 than the diazepam (−3.21) against GammaAmino Butyric Acid-A (GABAA). The present study provides a promising anxiolytic agent, MPD, which has itspotency due to the GABAA receptor binding and causing the mitigation of the symptoms of anxiety.

Actions of progesterone on depression-like behavior in a model of surgical menopause are mediated by GABAA receptors / Las acciones de progesterona sobre la conducta tipo depresión en un modelo de menopausia quirúrgica son mediadas por receptores GABAA

Abstract Introduction In rats, long-term ovariectomy results in low concentrations of steroid hormones and reproduces anxiety- and depression-like behavior after surgical menopause in women. Progesterone produces antidepressant-like effects two weeks post-ovariectomy (i.e., early post-ovariectomy) through actions on γ-aminobutyric acid-A (GABAA) receptors, but its antidepressant-like effects and mechanism of action in rats eight weeks post-ovariectomy (i.e., late post-ovariectomy, considered a model of surgical menopause) remain unknown. Objective To explore the antidepressant-like effects of progesterone and the participation of GABAA receptors in rats eight weeks post-ovariectomy. Method Long-term ovariectomized female Wistar rats were treated sub-acutely with vehicle or progesterone (.5, 1, and 2 mg/kg) and subjected to the open field and forced swim tests, and behavior was compared with cycling or fluoxetine-treated rats. The rats were then pretreated with picrotoxin (1 mg/kg) followed by progesterone (1 mg/kg) to explore the role of GABAA receptors in long-term-induced depression-like behavior. Results Long-term ovariectomized rats exhibited depression-like behavior in the forced swim test compared with intact rats, an effect that was not observed in progesterone- and fluoxetine-treated long-term ovariectomized rats. These effects were not attributable to psychomotor alterations. In the open field test, the time spent rearing and grooming was lower in ovariectomized rats compared with intact rats, which was not observed in progesterone- and fluoxetine-treated rats. Picrotoxin blocked the effects of progesterone in both behavioral tests. Discussion and conclusion These results indicated that sub-acute progesterone treatment reduced depression-like behavior through actions on GABAA receptors in a rat model of surgical menopause.

Resumen Introducción En la rata, la ovariectomía a largo plazo reproduce algunos síntomas de la menopausia quirúrgica, incluyendo la conducta de tipo depresiva. La progesterona produce efectos tipo antidepresivo en ratas con dos semanas de post-ovariectomía (post-ovariectomía temprana) con participación del receptor GABAA, pero se desconoce si este efecto y mecanismo de acción se mantiene en ratas con ocho semanas de post-ovariectomía (post-ovariectomía tardía considerada como un modelo de menopausia quirúrgica). Objetivo Evaluar el efecto tipo antidepresivo de la progesterona y la participación del receptor GABAA en ratas con ocho semanas de post-ovariectomía. Método Ratas con ocho semanas de post-ovariectomía fueron tratadas sub-agudamente con vehículo o progesterona (.5, 1, y 2 mg/kg) y comparadas con ratas intactas u ovariectomizadas tratadas con fluoxetina, evaluadas en campo abierto y nado forzado. Posteriormente, se identificó la participación del receptor GABAA en los efectos de progesterona (1 mg/kg) mediante el pretratamiento con picrotoxina (1 mg/kg). Resultados En nado forzado, la ovariectomía produjo conductas tipo depresión en comparación con las ratas intactas de la gónada, un efecto prevenido por la administración de progesterona y fluoxetina. En campo abierto, no hubo cambios significativos en la locomoción, pero la conducta vertical y el acicalamiento fueron bajos en las ratas ovariectomizadas respecto a las ratas intactas; lo cual fue prevenido por progesterona y fluoxetina. La picrotoxina bloqueó los efectos de la progesterona en ambas pruebas conductuales. Discusión y conclusión El tratamiento subagudo con progesterona reduce la conducta tipo depresión inducida en un modelo de menopausia quirúrgica con participación del receptor GABAA.

Effects of leptin on GABA content and receptor expression in hypothalamus of mice with sleep deprivation / 解放军医学杂志

[Abstract] Objective To observe the effects of the adipocyte hormone leptin on GABA content and receptor expression in hypothalamus of mice with sleep deprivation, and explore the possible mechanisms. Methods Male C57BL/6 mice were randomly divided into three groups (8 each): control group, sleep deprivation (SD) group and leptin supplement (L-SD) group. Mice in control group were set up in a water environment without sleep deprivation, mice in SD group were set up in a "modified multi-platform water environment" to establish a sleep deprivation model, and mice in L-SD group were given leptin 1.3 mg/kg intraperitoneally twice daily in conjunction with sleep deprivation. Seven days after sleep deprivation, the general conditions of mice were observed, body weight was measured and hypothalamic tissues and plasma specimens were collected. ELISA was used to detect the plasma leptin levels, hypothalamic γ-aminobutyric acid (GABA) and glutamate (Glu) contents. Western blotting was performed to detect the expression levels of GABA key glutamate decarboxylase 67 (GAD67) and GABAA receptor α1 subtype protein (GABAARα1). Results Compared with control group, the weight of mice in SD group significantly reduced [(22.03±0.42) g vs. (17.75±0.75) g, P0.05). The hypothalamic Glu levels were obviously higher in SD group [(686.56±10.01) ng/g] and L-SD group [(668.64+9.93) ng/g] than that in control group [(577.11±16.36) ng/g] (P0.05). The expressive levels of GAD67 and GABAARα1 protein in the hypothalamus of mice in SD group [0.68±0.06, 0.69±0.07] were significantly lower than that in control group (1.09±0.13, 0.99±0.07) (P<0.05); While the expressive levels of GAD67 and GABAARα1 proteins in the hypothalamus of mice in L-SD group (1.39±0.19 and 1.33±0.14, respectively) were significantly higher than those in SD group and control group (P<0.05). Conclusion Leptin can up-regulate the expression of the key GABA synthase GAD67, increase the content of GABA and the expression of GABAARα1 protein in hypothalamus of sleep-deprived mice, which may be an important mechanism of leptin affecting sleep.

Effect of electroacupuncture on expression of GABA receptor mRNA in different brain regions in rats with chronic inflammatory pain / 中国针灸

OBJECTIVE@#To observe the expression of GABA receptor mRNA in different brain regions of the central nervous system in chronic inflammatory pain rats and the intervention effect of electroacupuncture (EA).@*METHODS@#A total of 48 SPF male SD rats were randomly divided into a blank control group, a model control group, an EA group and a sham EA group, 12 rats in each group. The model of chronic inflammatory pain was established by injecting Freund's complete adjuvant into the foot. The EA group was treated with EA 28 days after the model establishment. The "Housanli" (ST 36) and "Kunlun" (BL 60) were selected and treated with dilatational wave, 2 Hz/100 Hz in frequency, 0.5-1.5 mA for 30 min; EA was given only once. In the sham EA group, the same acupoints were selected but the needles were only inserted into subcutaneous area; EA was connected for 30 min without electrical stimulation. The behavior changes of mechanical pain threshold and thermal pain threshold before model establishment, 1 day, 3 days, 7 days, 14 days, 21 days and 28 days after the model establishment as well as emotional behavior 29 days after the model establishment were observed; the relative expressions of GABA receptor mRNA in anterior cingulate cortex, amygdala and hypothalamus were observed.@*RESULTS@#Compared with the blank control group, the change rates of mechanical pain threshold and thermal pain threshold in the model control group were decreased significantly 1 day, 3 days, 7 days, 14 days, 21 days, 28 days after model establishment (0.05). Compared with the blank control group, the expression of GABA receptor mRNA in the amygdala was decreased significantly in the model control group (<0.01); compared with the model control group and the sham EA group, the expression of GABA receptor mRNA in amygdala was increased after intervention in the EA group (<0.01).@*CONCLUSION@#Single treatment of EA could significantly increase the mechanical pain threshold and thermal pain threshold, improve abnormal emotional behavior in rats with chronic inflammatory pain, which may be related to the increasing of expression of GABA receptor mRNA in the amygdala.

The Effect of 4-hydroxybenzaldehyde on the γ-aminobutyric Acid Type A Receptor

in the mammalian cortex and hippocampus. It is expressed heterologously in the Xenopus laevis oocyte as a α1β2γ2S/L subtype for application as an in vitro model for the screening of compounds that modulate receptor activities. In fact, 4-hydroxybenzaldehyde (4-HB) has been identified as one of the major components in Dendrocalamus asper bamboo shoots in our previous study, and the current study showed that at 101.7 μM, 4-HB significantly reduced the GABA-induced chloride current of GABAA receptors expressed on Xenopus oocytes, indicating a possible GABAergic antagonistic effect at high concentrations.

Analgesic effect and central mechanisms of CQ prescription on cancer invasion induced mirror image pain in model mice / 中国中药杂志

This study aimed to analyze the analgesic effect and related central mechanisms of CQ prescription on cancer invasion induced mirror image pain (CIIMIP)in model mice.In the study, male BALB/c mice were randomly divided into normal group, operation control group (injected with 0.2 mL inactivated S180 sarcoma cell sap), model group (injected with 0.2 mL S180 sarcoma cell sap on the right leg near the greater trochanter of femur) and CQ prescription low dose group (intraperitoneally injected with CQ prescription 100 mg•kg⁻¹ on the basis of model mice), CQ prescription middle dose group (intraperitoneally injected with CQ prescription 150 mg•kg⁻¹ on the basis of model mice), and CQ prescription high dose group (intraperitoneally injected with CQ prescription 200 mg•kg⁻¹ on the basis of model mice). Mechanical withdraw threshold (MWT) of the mirror image lateral hind paws were evaluated by Von Frey hairs before modeling and after surgery. The levels of glutamate (Glu), gamma aminobutyric acid (GABA), glycine (Gly), and taurine (Tau) in the L3-L5 spinal cord were measured by the high performance liquid chromatography-fluorescence detector (HPLC-FLD); AimPlex detection technology with multiple factors was used to detect the levels of regulated on activation in normal T-cell expressed and secreted (RANTES), monocyte chemoattractant protein (MCP-3) in the L3-L5 spinal cord. Then we observed the influence of GABAa receptor antagonist (Bicuculline) on analgesic effect of CQ prescription.The results indicated that CQ prescription could remarkably increase MWT of model mice(P<0.01, P<0.05), decrease the level of Glu(P<0.01, P<0.05), improve the levels of GABA, Gly, Tau(P<0.01, P<0.05), lower the ratio of Glu/GABA(P<0.01, P<0.05), and reduce the levels of RANTES, MCP-3(P<0.05) in the L3-L5 spinal cord, and GABAa receptor antagonist significantly blocked the analgesic effect of CQ prescription at two time points(P<0.05).This study showed that CQ prescription had significant analgesic effect on CIIMIP model mice, and its mechanism was associated with regulating the balance between excitability amino acid(EAA) and inhibitory amino acid (IAA) transmitters in central nervous system, partially activating GABAa receptor, and reducing the release of RANTES and MCP-3 in the spinal cord.

Effects of sub-chronic exposure to deltamethrin on the behavior of mice in learning and memory and expression of GABAA receptor α1 and γ2 subunits in the hippocampus of mice / 中华行为医学与脑科学杂志

Objective To study the effect of sub-chronic exposure to deltamethrin(DM) on the behavior of mice in learning and memory and expression of GABAA receptor α1 and γ2 subunits in the hippocampus of mice.Methods 60 female SPF Kunming mice were randomly divided into solvent control group,low-dose group,middle-dose group and high-dose group, 15 mice in each group.The latter three groups were exposured to deltamethrin for 60 days by gavage.Open field test (OFT) was applied to evaluate locomotor activity and exploratory behavior in mice.RQ-PCR was employed to measure the expression of GABAA receptor α1 and γ2 subunits in hippocampus of mice.Results After exposure to DM,the moving distance of the central area in the middle-dose group ((555.1 ± 12.8) cm) and high-dose group ((516.4± 11.88) cm) was significantly higher than that in the solvent control group ((327.3± 117.8) cm, P＜0.05).Numbers of standing in marginal area (F=4.117, P=0.010) and total movement distance (F=2.914, P=0.042) in the high-dose group ((27.9±9.9) times, (3211.3±379.8) cm) were also significantly higher than that in the solvent control group ((15.1 ±8.9)times, (3211.3±379.8)cm).The expression of GABAA receptor α1 subunit mRNA in the middle-dose group and high-dose group was significantly lower than that in the low-dose group and solvent control group(F=8.508, P=0.001) and the expression of GABAA receptor γ2 subunit mRNA in high-dose group was significantly lower than that in the other groups (F=6.738, P=0.002).Conclusion Sub-chronic exposure to DM can damage the function of locomotor activity and exploratory behavior,and inhibit the expression of GABAA receptor α1 and γ2 subunits in the hippocampus of mice.

GABAA Receptors in Neuropsychiatric Disorders and Its Therapeutic Potential / 世界科学技术-中医药现代化

Abundant evidences indicate a role of GABAergic system in the pathogenesis of neuropsychiatric dis-orders. GABAA receptors modulators have been long used in clinical. But the unwanted side-effect and risk of drug dependence have limited their use. With the increase understanding of the role of individual GABAA recep-tor subtypes in the pathology of these diseases, the subtype-selective GABAA receptors modulators and the multi-compound therapy may serve as potential therapeutic strategies. Here we review the researches which revealed the involvement of GABAA receptors in anxiety, depression and schizophrenia, and the research for new development in subtype-selective GABAA receptor modulators.

Is the GABA System Related to the Social Competence Improvement Effect of Aripiprazole? An 18F-Fluoroflumazenil PET Study

OBJECTIVE: Patients with schizophrenia who are treated with aripiprazole experience some benefits including an improvement of social competence, but the underlying mechanism of this improvement has not been investigated yet. This study aimed to provide preliminary evidence that the GABA system may be involved in the effect of aripiprazole on social competence. METHODS: Seventeen outpatients with schizophrenia (9 taking aripiprazole and 8 taking risperidone) and 18 healthy controls underwent 18F-fluoroflumazenil PET, and GABAA receptor binding potential was compared between the three groups. RESULTS: Voxelwise one-way ANOVA showed that GABAA receptor binding potentials in the right medial prefrontal cortex (p=0.04) and right dorsolateral prefrontal cortex (p=0.02) were significantly lower in the aripiprazole group than the risperidone group, and those in the left frontopolar cortex (p=0.03) and right premotor cortex (p=0.02) were significantly lower in the aripiprazole group than the risperidone and control groups. CONCLUSION: Our results suggest that aripiprazole administration results in increased GABA transmission in the prefrontal regions, and that these increases may be a neural basis of aripiprazole's clinical benefits on an improvement of social competence.

Neuroactive steroids and their role in epilepsy.

Neuroactive steroids are the certain steroids that alter neuronal excitability via the cell surface through interaction with certain neurotransmitter receptors. Neuroactive steroids regulate physiological functions of the central nervous system and have possible therapeutic potential in neurological diseases. They have been shown to affect neuronal excitability via their interaction with the ligand-gated ion channel family, such as the GABAA receptor by acting genomically as well as nongenomically. Positive modulators of GABAA receptor have anticonvulsant action as they enhance GABAergic transmission thereby increasing the seizure threshold. By virtue of these properties, neurosteroids appear to be relevant to pathophysiology and pharmacological treatment of many neurological diseases including catamenial epilepsy, stress induced epilepsy, temporal lobe epilepsy, alcohol withdrawal seizures, infantile spasm and status epilepticus. So far, only synthetic neurosteroid, ganaxolone has been tried in treatment of epilepsy and has shown good efficacy and tolerability. But, human data of trials are limited and hence, large double-blinded, placebo-controlled, randomized clinical trials are required before their use. The paper reviews the biosynthesis and GABAA receptor modulation of neurosteroids and their potential role in epilepsy.

Mutation Screening of the gamma-Aminobutyric Acid Type-A Receptor Subunit gamma2 Gene in Korean Patients with Childhood Absence Epilepsy

BACKGROUND AND PURPOSE: Since the gamma-aminobutyric acid type-A receptor subunit gamma2 gene (GABRG2) mutation was discovered in an Australian family with childhood absence epilepsy (CAE) and febrile convulsions, a few screening studies for the GABRG2 mutation have been conducted in sporadic individuals with CAE from other ethnic groups. The aim of this study was to determine whether or not the previously reported genetic mutations and single-nucleotide polymorphisms (SNPs) of GABRG2 can be reproduced in sporadic Korean individuals with CAE, compared to healthy Korean individuals. METHODS: Thirty-five children with CAE in Chonnam National University Hospital and healthy controls (n=207) were enrolled, and the medical records of patients with CAE were reviewed. CAE was diagnosed according to the Classification and Terminology of the International League Against Epilepsy. All nine exons of GABRG2 were directly sequenced. In addition, the two SNPs found in our CAE patients were analyzed: C315T in exon 3 (E3) and C588T in exon 5 (E5). The frequencies of the two SNPs in the CAE patients were compared with data from healthy controls (for E3 and E5) and from previously reported Korean population data (only for E3). RESULTS: No mutation of GABRG2 was found in our CAE patients. In addition, the allele and genotype frequencies of the two polymorphisms did not differ significantly between CAE patients, healthy controls, and the Korean general population (p>0.05). CONCLUSIONS: Our study of sporadic Korean individuals with CAE found no evidence that GABRG2 contributes to the genetic basis of CAE.

Glycine- and GABA-mimetic Actions of Shilajit on the Substantia Gelatinosa Neurons of the Trigeminal Subnucleus Caudalis in Mice

Shilajit, a medicine herb commonly used in Ayurveda, has been reported to contain at least 85 minerals in ionic form that act on a variety of chemical, biological, and physical stressors. The substantia gelatinosa (SG) neurons of the trigeminal subnucleus caudalis (Vc) are involved in orofacial nociceptive processing. Shilajit has been reported to be an injury and muscular pain reliever but there have been few functional studies of the effect of Shilajit on the SG neurons of the Vc. Therefore, whole cell and gramicidin-perfotrated patch clamp studies were performed to examine the action mechanism of Shilajit on the SG neurons of Vc from mouse brainstem slices. In the whole cell patch clamp mode, Shilajit induced short-lived and repeatable inward currents under the condition of a high chloride pipette solution on all the SG neurons tested. The Shilajit-induced inward currents were concentration dependent and maintained in the presence of tetrodotoxin (TTX), a voltage gated Na+ channel blocker, CNQX, a non-NMDA glutamate receptor antagonist, and AP5, an NMDA receptor antagonist. The Shilajit-induced responses were partially suppressed by picrotoxin, a GABAA receptor antagonist, and totally blocked in the presence of strychnine, a glycine receptor antagonist, however not affected by mecamylamine hydrochloride (MCH), a nicotinic acetylcholine receptor antagonist. Under the potassium gluconate pipette solution at holding potential 0 mV, Shilajit induced repeatable outward current. These results show that Shilajit has inhibitory effects on the SG neurons of Vc through chloride ion channels by activation of the glycine receptor and GABAA receptor, indicating that Shilajit contains sedating ingredients for the central nervous system. These results also suggest that Shilajit may be a potential target for modulating orofacial pain processing.

The effects of midazolam and sevoflurane on the GABAA receptors with alternatively spliced variants of the gamma2 subunit / 대한마취과학회지

BACKGROUND: Emergence agitation after sevoflurane anesthesia in children can be prevented by midazolam. Alternative splicing of the GABAA receptor changes with age. Therefore, we hypothesized that alternative splicing of the gamma2 subunit affects the GABA current when applying sevoflurane and midazolam. METHODS: We performed the whole-cell patch clamp technique on human embryonic kidney 293 cells that were transfected with alpha1beta2gamma2L or alpha1beta2gamma2S. The concentration-response relations were recorded for midazolam and sevoflurane, and the co-application responses were measured at concentrations of 1.5 nM, 15 nM and 300 nM of midazolam and 0.5%, 2.0% and 4.0% of sevoflurane. Each GABA current was compared with that produced by 5 microM of GABA. RESULTS: The concentration-response relationships for midazolam and sevoflurane were dose-dependent without any differences between the alpha1beta2gamma2L and alpha1beta2gamma2S subtypes. 1.5 nM and 15 nM of midazolam did not significantly enhance the current after treatment with 0.5% sevoflurane for both subtypes. The current after treatment with 2.0% sevoflurane was enhanced by 1.5 nM midazolam for the alpha1beta2gamma2S subtype, but not for the alpha1beta2gamma2L subtype. In the case of 2.0% sevoflurane with 15 nM of midazolam, and 4.0% sevoflurane with 300 nM of midazolam, the GABA currents were significantly enhanced for both subtypes. CONCLUSIONS: These results show that the difference in the gamma2 subunit cannot explain the emergence agitation after sevoflurane anesthesia in children in vitro. This suggests that co-application of sevoflurane and midazolam enhances the GABA current according to the alternative splicing of the gamma2 subunit and the concentration of both drugs.

Effects of Agmatine on GABAA Receptor Antagonist-induced Tactile Allodynia / 대한통증학회지

BACKGROUND: The intrathecal (IT) GABAA receptor antagonist, bicuculline (BIC), results in tactile allodynia (TA) through disinhibition in the spinal cord. Such disinhibition is considered to be an important mechanism for neuropathic pain. Agmatine, an endogenous polyamine, has a neuro-protective effect in the central nervous system. We investigated the analgesic effects and mechanisms of agmatine action on BIC-induced TA. METHODS: Male Sprague-Dawley rats, weighting 250-300 g, were subjected to implantations of PE-10 into the lumbar subarachnoid space for IT drug injection. Five days after surgery, either 10 microliter of normal saline (NS) or agmatine (30 microgram or 10 microgram) in 10 microliter NS were injected 10 min prior to BIC (10 microgram) or NMDA (5 microgram). We assessed the degree of TA (graded 0: no response, 1: mild response, 2: moderate response, 3: strong response) every 5 min for 30 min. Areas under curves and degree of TA were expressed as mean +/- SEM. Results were analyzed using one-way ANOVA followed by a Tukey test for multiple comparisons. P < 0.05 was considered significant. RESULTS: IT BIC-induced strong TA reached its peak and plateaued between 10 to 15 min. IT NS-NMDA induced mild transient TA for up to 15 min. Preemptive IT AG attenuated IT BIC-induced TA dose dependently and preemptive IT AG10 completely abolished the IT NMDA-induced TA. CONCLUSIONS: Preemptive IT AG attenuated the IT BIC-induced TA through inhibitory actions on postsynaptic NMDA receptor activation. AG might be a viable therapeutic option in the treatment of neuropathic pain.

MODULATORY EFFECT OF CAFFEINE ON GABA-ACTIVATED CURRENT FROM ACUTELY ISOLATED RAT DORSAL ROOT GANGLION NEURONS / 神经解剖学杂志

Whole-cell patch clamp technique was performed on acutely isolated rat dorsal root ganglion (DRG) neurons to investigate the modulatory effect of caffeine on γ-aminobutyric acid (GABA)-activated currents (IGABA). The results showed that the majority of the neurons examined (97.4%, 113/116) were sensitive to GABA. 1-1000 μmol/L GABA activated a concentration-dependent inward current which manifested obvious desensitization. After the neurons were treated with caffeine (0.01-100 μmol/L) prior to the application of GABA (100 μmol/L) for 30 s, GABA-activated membrane currents were obviously inhibited. Caffeine shifted the GABA dose-response curve downward and decreased the maximum response to 57% without changing Kd value. These results indicate that the inhibitory effect is non-competitive. Theophylline showed a similar and stronger inhibitory effect on IGABA. The pretreatment with caffeine (10 μmol/L) inhibited IGABA, which was potentized by diazepam (1 μmol/L). Intracellular application of H-8 almost completely abolished the inhibitory effect of caffeine on IGABA. The present results suggest that caffeine may be able to antagonize the effect of presynaptic inhibition of GABA in primary afferent.

The Change in the Expression of Gamma-Amino Butyric Acid A Receptor Subunits in Rat's Flocculus / 听力学及言语疾病杂志

Objective To observe the expression of gamma-amino butyric acid A receptor(GABAA receptor)?3、?1、? subunits in rat flocculus following unilateral labyrinthectomy(UL).Methods 24 wistar rats were randomly divided into two groups.18 animals received unilateral labyrinthectomy while the others maintained labyrinthine well.After removing left labyrinthine,the change of GABAA receptor ?3、?1、? subunits was detected by immunohistochemistry.Results GABAA receptor ?1、? subunits in flocculus was induced on the operated side after unilateral labyrinthectomy.The most expression was on the 1st day flocculus of following UL.The expression is descending from the 3rd day to 7th day flocculus of following UL.The GABAA receptor ?3 subunit immunostaining in flocculus was weak and did not change in the process of vestibular compensation.Conclusion GABAA receptor ?1、? subunits were induced increase in the flocculus after unilateral labyrinthectomy.The alteration in the resting discharge of the central vestibular neurons may be caused by the increase of GABAA receptor ?1、? subunits in the flocculus.But the significance of the change of GABAA receptor ?1、? subunits in the vestibular compensation is still unknown.Our study suggests that GABAA receptor ?3 subunits may not participate in constructing GABAA receptor in the flocculus.

Antiepileptic and Neuroprotective Effect of Ketamine in Lithium-Pilocarpine Induced Status Epilepticus Rat Model / 대한간질학회지

PURPOSE: To examine the putative seizure-protective properties of ketamine in lithium-pilocarpine induced status epilepticus (LPSE). METHODS: Lithium chloride followed 24 h later by pilocarpine was administered for seizure induction. Ketamine (40 mg/kg) or phenytoin (50 mg/kg) was injected intraperitoneally 10 min or 60 min after the onset of continuous ictal discharge. Then the seizure behavior and EEG were observed and histological changes were compared through Nissl stain at 72 hours. RESULTS: The antiepileptic effect of ketamine, injected during the early stages of LPSE (10 min after the onset of continuous ictal discharge), was comparable to that of phenytoin. Ketamine was more effective than phenytoin in decreasing spike frequency, when administered on the plateau of LPSE (injection 60 min after onset of continuous ictal discharge electrographically). Anticonvulsant action of ketamine was confirmed by a less neuronal injury in hippocampus compared with control rats injected with phenytoin. CONCLUSIONS: In prolonged status epilepticus rat model, ketamine was effective as an antiepileptic, but phenytoin was not. Ketamine was also neuroprotective on the neuronal injury in the hippocampus. These results suggest that ketamine might be useful as an antiepileptic drug when standard antiepileptic drugs fail in the treatment of the refractory cases of status epilepticus.

Neuronal Excitatory Action of GABA on the Pelvic Ganglia

OBJECTIVE: In the central nervous system, gamma-aminobutyric acid (GABA) is well known to act as an inhibitory neurotransmitter by hyperpolarizing postsynaptic neurons through gating GABA-activated Cl- channels. To date, however, the functional roles of GABA remain unclear in the autonomic nervous system. In the present study, we characterize GABA-activated Cl- currents in the neurons of major pelvic ganglia (MPG). METHODS: MPG neurons, located on the lateral surfaces of the prostate gland, from male rats were enzymatically dissociated. Ionic currents were recorded using whole-cell variant patch-clamp technique. Membrane potential was recorded under current clamp mode. Current traces were filterd at 2kHz by using 4-pole Bassel filter in the amplifier. RESULTS: Application of GABA (100micrometer) induced inward currents in the neurons, with holding potentials being maintained below the Cl- equilibrium potential (ECl). The GABA response was concentration-dependent and its reversal potential was close to the theoretical ECl. The GABA-induced Cl- currents were largely blocked by bicuculline (10micrometer, n=5), a GABAA receptor antagonist, but were not affected by 9-AC and niflumic acid, chloride channel blockers. GABA also produced significant membrane depolarization (19mV, n=28). As in the case of the Cl- currents, the GABA-induced depolarizations were largely blocked by bicuculline(10micrometer, n=6), but not by DIDS(50micrometer, n=4), another chloride channel blocker. CONCLUSION: The data suggest that GABAergic roles may be due to it's activation of excitatory GABAA receptors, which are expressed in MPG neurons.

Inhibitory and Excitatory Postsynaptic Currents of Medial Vestibular Nucleus Neurons of Rats

The medial vestibular nucleus (MVN) neurons are controlled by excitatory synaptic transmission from the vestibular afferent and commissural projections, and by inhibitory transmission from interneurons. Spontaneous synaptic currents of MVN neurons were studied using whole cell patch clamp recording in slices prepared from 13- to 17-day-old rats. The spontaneous inhibitory postsynaptic currents (sIPSCs) were significantly reduced by the GABAA antagonist bicuculline (20micrometer), but were not affected by the glycine antagonist strychnine (1micrometer). The frequency, amplitude, and decay time constant of sIPSCs were 4.3 0.9 Hz, 18.1 2.0 pA, and 8.9 0.4 ms, respectively. Spontaneous excitatory postsynaptic currents (sEPSCs) were mediated by non-NMDA and NMDA receptors. The specific AMPA receptor antagonist GYKI-52466 (50micrometer) completely blocked the non-NMDA mediated sEPSCs, indicating that they are mediated by an AMPA-preferring receptor. The AMPA mediated sEPSCs were characterized by low frequency (1.5 0.4 Hz), small amplitude (13.9 1.9 pA), and rapid decay kinetics (2.8 0.2 ms). The majority (15/21) displayed linear I-V relationships, suggesting the presence of GluR2-containing AMPA receptors. Only 35% of recorded MVN neurons showed NMDA mediated currents, which were characterized by small amplitude and low frequency. These results suggest that the MVN neurons receive excitatory inputs mediated by AMPA, but not kainate, and NMDA receptors, and inhibitory transmission mediated by GABAA receptors in neonatal rats.