Novel alternative splicing of GABA receptor RDL exon 9 from Laodelphax striatellus modulates agonist potency

The resistance to dieldrin gene(RDL)encodes the primary subunit of the insect ionotropic y-aminobutyric acid(GABA)receptor(GABAR),which is the target of phenylpyrazole and isoxazoline insecticides.The splice variants in exons 3 and 6 of RDL,which have been widely explored in many insects,modulate the agonist potency of the homomeric RDL GABAR and potentially play an important role in the development of insects.In the present study,four splice variants of exon 9 were identified in RDL of the small brown planthopper,Laodelphax striatellus(LsRDL),resulting in LsRDL-9sl,LsRDL-92l\LsRDL-9b,and LsRDL-9c.LsRDL-9a has one more amino acid(E,glutamic acid)compared with LsRDL-9a\and LsRDL-9b lacked two amino acids and had seven different amino acids compared with LsRDL-9c.Two-electrode voltage-clamp recording on LsRDLs expressed in Xenopus oocytes showed that alternative splicing of exon 9 has significant impact on LsRDL sensitivity to the agonists GABA and 0-alanine,whereas no significant difference was observed in the potencies of the non-competitive antagonists(NCAs)ethiprole and fluralaner on the splice variants.Our results suggest that alternative splicing of RDL exon 9 broadens functional capabilities of the GABAR in L.striatellus by influencing the action of GABA.

GetArtemisininsByAnymeans (GABA)： artemisinins path to conquer diabetes go through GABA receptors

Diabetes is a chronic disease of elevated blood glucose levels that affects more than 400 million people worldwide.Complications of diabetes affect the neuronal and the vascular systems and causes diabetic kidney disease,cardiovascular disease,hypertension,retinopathy,peripheral neuropathy,and diabetic food diseases.Diabetes is caused by either the body’s inability to

Suppression of Human Liver Cancer Cell Migration and Invasion via the GABA_A Receptor

Objective To investigate the roles of theγ-aminobutyric acid(GABA) in the metastasis of hepatocellular carcinoma(HCC) and to explore the potential of a novel therapeutic approach for the treatment of HCC. Methods The expression levels of GABA receptor subunit genes in various HCC cell lines and patients’ tissues were detected by quantitative real-time polymerase chain reaction and Western blot analysis.Transwell cell migration and invasion assays were carried out for functional analysis.The effects of GABA on liver cancer cell cytoskeletal were determined by immunofluorescence staining. And the effects of GABA on HCC metastasis in nude mice were evaluated using an in vivo orthotopic model of liver cancer. Results The mRNA level of GABA receptor subunits varied between the primary hepatocellular carcinoma tissue and the adjacent non-tumor liver tissue.GABA inhibited human liver cancer cell migration and invasion via the ionotropic GABAa receptor as a result of the induction of liver cancer cell cytoskeletal reorganization.Pretreatment with GABA also significantly reduced intrahepatic liver metastasis and primary tumor formation in vivo. Conclusions These findings introduce a potential and novel therapeutic approach for the treatment of cancer patients based on the modulation of the GABAergic system.

Preliminary Study on γ-Aminobutyric Acid (GABA_A) Like Receptor in Rat Testis

For making it clear whether GABAA-like receptor is in cells or rat testis and how itsgene expresses in tissue cells, the mRNA of rat testis was microinjected into Xenopusoocyte. The membrane electrobiological results showed that an inward 30 nA micro-currentwas elicited, under two-electrode voltageclamped configuration, by extracellular GABA(500 μmol/L), and both Bicuculline and Picrotoxin could inhibit this effect. It is an indication that the mRNA of rat testis can express GABA receptor in the membrane of Xenonpus oocyte. Using Muscimol as a excitant of GABA receptor type A, the micro--currentwas also elicited to generate; however, using Baclofen as a excitant of GABA receptortype B, the micro-current could not be induced. These results indicate that GABA receptorexpressed in Xenopus oocyte membrane is not type B but for type A. On the basis of the research result above, 24-mer oligonucleotides to be complementary to the high conservativeregion of the cDNAs of neur-GABA receptors were synthesized as probes to hybridize respectively with the RNAs Of brain and testis of adult rat, and of rat testes of the variousages. The dot hybridizations showed that the hybrid signal of rat testis was stronger thanthat of rat brain, meaning that, compared with rat brain, the RNA of rat testis has morehomologous regions with probes, and also implying that the GABA receptor from theRNA Of rat testis may be similar to neural-GABA receptor. This receptor therefore iscalled as GABA_A-like receptor. The dot blot analysis above also showed the testis GABA_Alike receptor. The dot blot analysis above also showed testis GABA_A like receptor mRNAcontent changed with the develOPmental age of rats. There is a very low level of gene expression in the rat testis on day 5 postnatal; there is the highest expression of GABA_A-likereceptor gene in rat testes on day 30to 100 after birth; the expression begins to drop on day200 after birth.

Diazepam reduces synaptic GABA type areceptor availability via multiple trafficking mechanisms

OBJECTIVE Investigate the effects of diazepam(DZP) on γ2 subunit containing GABA type A receptor(GABA A R) trafficking.METHODS Immunofluorescence microscopy measured surface GABA A Rs and gephyrin in rat cortical neurons after 24 h exposure of 1.0 μmol·L^(-1) DZP.Biochemical studies of mice injected with 10 mg·kg^(-1) DZP vs vehicle were assessed for γ2 subunit and total gephyrin cortical levels 12 h post-injection.Ubiquitination of the γ2 subunit was studied by immunoprecipitation after 12 h of 1.0 μmol·L^(-1) DZP exposure.A γ2 subunit encoding an N terminal fluorogen-activating peptide and pH-sensitive green fluorescent protein(γ2 pH FAP) measured lysosomal targeting of γ2 containing GABA A Rs.RFP-gephyrin and γ2 pH FAP synaptic diffusion rates were examined using fluorescence recovery after photobleaching(FRAP).RESULTS Extrasynaptic levels of γ2 GABA A Rs decreased by 12.2%,while synaptic gephyrin S270 phosphorylation increased by 18.3% in DZP-treated neurons after 24 h compared to control(P<0.05).Dendritic levels of gephyrin were also reduced to 74.1% of control,while S270 phosphorylation was elevated by 25.2%(P<0.05;P<0.01).Mice 12 h post-DZP injection demonstrated a 12.7% and 26.1% decrease in total γ2 and gephyrin levels,respectively(P<0.05;P<0.01).12 h DZP treatment enhanced γ2 subunit ubiquitination 1.13-fold relative to control(P<0.05).Internalized γ2 pH FAP GABA A Rs associated with lysosomes was 8.0% higher in neurons treated with 12-16 h DZP compared to control.Pilot FRAP experiments suggest gephyrin and γ2 have increased mobility and turnover at synapses following DZP.CONCLUSION DZP treatment decreases γ2 GABA A R levels and gephyrin scaffolding function after one day of exposure,which may contribute to the formation of DZP tolerance.

Electroacupuncture (EA) Speeds Up the Regulation of Hypothalamic Pituitary Adrenal Axis Dysfunction in Acute Surgical Trauma Rats: Mediated by Hypothalamic Gamma-Aminobutyric Acid (GABA)_AReceptors

Hypothalamic Corticotropin-releasing factor (CRF) directly activates the hypothalamic pituitary adrenal axis (HPA axis) during the surgical trauma induced stress response. Electroacupuncture (EA) has been demonstrated to have stress relieving effects in breast surgery, colorectal surgery, prostatectomy and craniotomy. This study was aimed to investigate the hypothesis that EA could regulate hypothalamic CRF in surgical trauma rats. In experiment one, Sprague-Dawley (SD) male rats were divided into intact, model (10% partial hepatectomy), sham EA and EA group. Rats from the Sham EA and EA group were stimulated at ST36-Zusanli and SP6-Sanyiniiao acupoints twice, 24 hours before the surgery and immediately after the surgery. Expressions of hypothalamic CRF and CRFR, GABA receptors, glutamate decarboxylase (GAD), serum adrenocorticotropic hormone (ACTH) and Corticosterone (CORT) were observed at 2, 4, 8 and 24 h after the surgery by radioimmunoassay (RIA), western blot, real-time PCR and immunohistochemistry. In the experiment two, SD male rats were divided into the intact, model, model + vehicle, model + L-838,417 EA and EA + L838,417 group. It was found that hypothalamus CRF, serum ACTH and CORT levels were increased in model group compared with the intact group, and those in the EA group decreased in comparison with the model group. Compared with the model group, hypothalamus-aminobutyric acid (GABA) receptor Aα3 mRNA and protein expressions of the EA group raised strikingly. In conclusion, EA alleviated surgical stress response by improving the GABA synthesis in hypothalamus, thus enhancing GABA receptors’ inhibitory regulation of the HPA axis dysfunction in rats with acute surgical trauma.

Effects of Nourishing “Yin”-Removing “Fire” Chinese Herb Mixture on the Differential Expression of GABA_AReceptor <i>α</i>Subunits in Hypothalamus of Precocious Puberty Female Rats

GABAergic input to Gonadotropin-releasing hormone (GnRH) neurons is necessary to initiate the onset of puberty and its action mainly depends on GABAA receptor of which the subunit composition, properties and consequently function varies during this period. Nourishing “Yin”-Removing “Fire” Chinese herb mixture, a Chinese herb-based formulation, has been proved that it may retard the initiation of pubertal development in female precocious puberty rats. Our objective is to investigate the effects of Nourishing “Yin”-Removing “Fire” Chinese herb mixture on the expression of GABAA receptor α subunits in hypothalamus. Female Sprague-Dawley rats were divided into normal (N), precocious puberty model (M) induced by danazol, model exposed to saline (MS) and model exposed to Chinese herb mixture (CHM) groups. All rats were administered by the Chinese herb mixture from P15 on. Coefficients of reproductive organs and serum gonadotropins and estradiol levels in M were significantly enhanced while they were significantly decreased in CHM. The hypothalamic GnRH mRNA was also significantly increased in M and in CHM, as well as ERα mRNA. At the mean time, the hypothalamic GABAA receptor α1 and α3 subunits mRNA were more significantly decreased in M than those of N, while they were more significantly enhanced in CHM than those in M (p 0.01), the protein expression of which in hypothalamus had the same trend as the mRNA expression. The evidence suggests that Nourishing “Yin”-Removing “Fire” Chinese herb mixture could significantly retard the sexual development of the precocious rats, and up-regulate the expressions of hypothalamic GABAA receptor α1 and α3 subunits. Our result indicated that GABAA receptor α1 and α3 subunits might involve in the effective treatment of herb mixture on idiopathic precocious puberty.

Differential Effect of Unilateral Amygdalar GABAA Receptor Agonist Injection on Low- and High-Anxiety Rats

The influence of γ-aminobutyric type-A (GABAA) receptors agonist (muscimol hydrobromide, 0.1 μg/0.5 μl) injections into the right or left basolateral amygdala (BLA) on the behavior of high-anxiety (HA) and low-anxiety (LA) rats subjected to the elevated plus-maze (EPM) test was investigated. Anxiolytic-like effects (increase of open-arm entries and open-arm time) was revealed only after administration of muscimol into the left (but not right) amygdala of HA animals. No effect was observed upon administration of muscimol to LA rats. These findings suggest an important role in anxiety regulation of the amygdalar GABA levels, and the assumed GABA hemispheric lateralization.

海洛因诱导大鼠伏隔核NMDA受体亚基对GABA表达的影响

目的:研究大鼠伏隔核(NAc)在海洛因诱导条件性位置偏爱(CPP)状态及戒断状态下,NMDA受体亚基NR2B和NR2C对GABA表达的调控,探索GABA能神经元上NR2B和NR2C亚基在海洛因诱导中的作用。方法:将SD大鼠随机分为两组,即对照组和海洛因诱导组。海洛因诱导组又分为海洛因诱导CPP状态和海洛因戒断状态。采用海洛因小剂量递增法皮下连续注射7 d,建立海洛因诱导CPP模型,再自然戒断7 d,免疫组织化学染色检测各组大鼠伏隔核GABA和NR2B、NR2C亚基的位置关系。结果:采用小剂量递增法连续注射7 d海洛因,大鼠形成了稳定的海洛因诱导CPP模型。免疫荧光染色结果可见,各组大鼠伏隔核均有GABA、NR2B和NR2C表达,且GABA与NR2B及NR2C受体均有共表达。免疫组织化学结果显示,海洛因成瘾状态大鼠伏隔核GABA表达量明显高于对照组和戒断状态,具显著性差异(P<0.01)。戒断状态大鼠GABA表达量最低。结论:GABA的表达变化受NMDA受体亚基活性的影响;NR2B亚基对GABA的调控作用可能参与了海洛因依赖的复燃。

How do lateral septum projections to the ventral CA1 influence sociability?

Social dysfunction is a risk factor for several neuropsychiatric illnesses.Previous studies have shown that the lateral septum(LS)-related pathway plays a critical role in mediating social behaviors.Howeve r,the role of the connections between the LS and its downstream brain regions in social behavio rs remains unclea r.In this study,we conducted a three-chamber test using electrophysiological and chemogenetic approaches in mice to determine how LS projections to ventral CA1(vCA1)influence sociability.Our res ults showed that gamma-aminobutyric acid(GABA)-e rgic neuro ns were activated following social experience,and that social behavio rs were enhanced by chemogenetic modulation of these neurons.Moreover,LS GABAergic neurons extended their functional neural connections via vCA1 glutamatergic pyramidal neurons,and regulating LSGABA→vCA1Gluneural projections affected social behaviors,which were impeded by suppressing LSprojecting vCA1 neuronal activity or inhibiting GABAAreceptors in vCA1.These findings support the hypothesis that LS inputs to the vCA1 can control social prefe rences and social novelty behaviors.These findings provide new insights rega rding the neural circuits that regulate sociability.

激活GABA_B受体在针刺镇痛中的作用

目的 :脑室注射γ 氨基丁酸 (GABA)A受体的拮抗剂荷包牡丹碱 (Bic)未能阻断针刺镇痛效应 ,微电泳导入Bic部分阻断电针抑制脊髓背角伤害性反应 ,说明GABA可通过激活A受体参与针刺镇痛中脊髓节段性抑制。本文进一步探讨了激活GABAB 受体在针刺镇痛中的作用。方法 :以辐射热照射大鼠尾部引起甩尾反射潜伏期作为痛阈的指标 ,以针刺“次”穴后痛阈最大变化百分率判断镇痛效应 ,观察脑室注射 (icv) 5μL或蛛网膜下腔 (ith)注射 1 0 μLGABAB 受体的拮抗剂CGP 55845对针刺镇痛效应的影响。每组 6～ 8例。结果 :icvGABA( 1 2 5μg、2 50 μg、50 0 μg)或GABAB 受体激动剂苯氯丁氨酸 (Baclofen ,2 5ng、2 50ng、2 50 0ng)可产生剂量依赖的镇痛效应。icvCGP 55845( 5ng、50ng)可大部分阻断GABA和Baclofen的镇痛效应。针刺双侧“次”穴( 50Hz,1～ 2mA) 1 0min ,痛阈提高到针前值的 ( 1 42 .5± 2 .1 ) % ,镇痛效应显著。针前icvCGP55845针后痛阈分别提高到 ( 1 1 1 .2± 1 .2 ) %和 ( 1 1 2 .1± 1 .1 ) % ,阻断率分别为 73 .7%和 71 .6% ,和事先icv生理盐水 ( 1 43 .7± 2 .0 ) %相比 ,阻断效应明显。若针刺前ithCGP 55845( 50ng、50 0ng) ,也能明显阻断针刺镇痛效应。结论 :脑内注射GABA或Baclofen可通过激?

表皮穿透和GABA_A受体不敏感性在小菜蛾对阿维菌素抗性中的作用

用氚标记阿维菌素点滴处理阿维菌素敏感 (ABM S)和抗性 (ABM R)种群小菜蛾幼虫 ,结果显示 ,在 5～ 36 0min内的 7个不同处理时间 ,ABM R种群的平均表皮穿透量比ABM S种群少 1 5倍 ,处理 2 4h后 ,ABM R种群仍有 45 9%的3 H 阿维菌素滞留于体表 ,而ABM S种群却有 98 4%的药剂穿透表皮。放射配体结合分析表明 ,GABAA 受体结合性质的改变是小菜蛾对阿维菌素的另一抗性机制 ,ABM S种群 (Kd=10 936 8± 0 4374nmol L)和ABM R种群 (Kd=9 832 8± 0 3933nmol L)的受体亲和力无显著差异 ,但抗性种群的最大结合量 (Bmax =71 2 842± 4 9910fmol mg蛋白 )比敏感种群 (Bmax =112 0 2 5 5± 7 8418fmol mg蛋白 )降低 6 3 6 % ,即抗性是受体数目的减少而非结构上的改变。

盐酸川芎嗪通过干预GABAR和FOXP2的表达保护低压低氧大鼠学习记忆

目的探讨盐酸川芎嗪对低压低氧大鼠学习记忆功能的影响及其作用机制。方法将120只SD大鼠随机分为2组,低氧对照组(5 500 m)、低氧药物组(5 500 m),按时间段不同又分为1 d、3 d、7 d、15 d、30 d组,每组12只;对照组和药物组在模拟海拔5500 m的低压氧仓造模,对照组腹腔注射生理盐水,药物组用同样的方法注射盐酸川芎嗪进行干预。用Morris水迷宫实验检测大鼠行为学变化;Western blot检测大鼠海马GABAAα1R、GABAB1R、FOXP2表达情况。结果(1)通过计算对照组和药物组定位航行实验中的总路程和穿越平台次数可以得出,两组1 d结果差异无统计学意义(P>0.05),从3 d组开始,药物组总路程较对照组逐渐缩短(P<0.01),而穿越中心平台次数较对照组逐渐增多(P<0.01);(2)Western blot检测海马GABAAα1R受体,不同时间段对照组与药物组海马中该受体表达差异无统计学意义(P>0.05);GABAB1R受体和FOXP2蛋白,1 d对照组药物组表达没有差异,从3 d组开始,对照组该受体和蛋白表达量均低于药物组(P<0.05);(3)对照组海马中GABAB1R与水迷宫总路程呈负相关(r=-0.738,P<0.05);对照组海马中FOXP2蛋白与水迷宫总路程呈负相关(r=-0.693,P<0.05);对照组海马中GABAB1R、FOXP2蛋白表达呈正相关(r=0.834,P<0.05)。结论盐酸川芎嗪对低压低氧大脑学习记忆能力起到一定的保护作用,其机制可能与增加大鼠脑内递质GABAB1R和蛋白FOXP2表达量有关。

调理心肾中药对拟痴呆大鼠脑组织中M和GABA受体功能的影响

以~3H-QNB和~3H-GABA为放射性配基,用受体放射性配基结合分析法,测出拟痴呆模型大鼠大脑皮层和海马组织中的M受体和小脑组织中的GABA受体的R_t值明显降低;M受体的K_D值在大脑皮层中明显减少,在海马中略有升高。小脑中GABA受体的K_D值显著降低。调理心肾中药及喜德镇(Hydergin,为国外常用抗老年痴呆药)能使降低的M受体和GABA受体的R_t值均明显升高,接近正常水平。对K_D值则有不同程度的调整作用。

羟丁酸钠对大鼠原代培养皮层神经元缺氧复氧损伤的保护作用与GABA_A受体的关系

目的 :探讨羟丁酸钠 (SO)对大鼠皮层神经元缺氧复氧损伤的保护作用与GABAA 受体的关系。方法 :采用原代培养大鼠皮层神经元建立缺氧复氧损伤模型 ,观察细胞的形态学 ,测定其LDH漏出率、MDA含量、SOD、GPx活力。结果 :缺氧复氧可引起神经元损伤 ,LDH漏出率增加 ,MDA含量升高 (P <0 .0 1) ,SOD、GPx活力降低 (P <0 .0 1)。SO能显著减少损伤神经元的LDH漏出率及MDA的生成 (P <0 .0 1) ,升高SOD、GPx(P <0 .0 1)的活力 ,这种作用可被GABAA 受体阻断剂seurinine减弱 (P <0 .0 1)。结论 :SO对缺氧复氧神经元损伤的保护作用可能与其激动GABAA 受体有关。

有机磷农药急性中毒对大鼠GABA受体影响的研究

探索有机磷农药急性中毒的γ -氨基丁酸系统机理 ,为有机磷农药急性中毒的治疗提供理论依据。实验 :用大鼠脑神经末梢微囊GABA受体做模型 ,从大鼠体外实验、体内染毒实验 (动物抽搐发作和不发作 ) ,观察GABA受体的变化。结果 :在体外实验中 ,1× 10 -2 mol/L的二嗪农或丙氟磷能显著降低大鼠GABA受体的结合 (P <0 .0 1) ,1× 10 -3 mol/L的二嗪农仍能显著降低GABA受体的结合 (P <0 .0 5 )。二嗪农 1.0 95 g/kg灌胃大鼠 ,结果发现3 H -GABA的结合值在抽搐发作时显著降低 ,大鼠腹腔注射丙氟磷 6mg/kg ,观察大鼠抽搐发作与不发作 ,3 H -GABA的结合值均显著降低。结论 :有机磷农药在一定浓度下能显著降低大鼠脑GABA受体的结合 。

UDMH对GABA及其受体影响的研究

目的 :探索UDMH急性中毒的γ -氨基丁酸及其受体机制 ,为UDMH急性中毒的治疗提供论理依据。实验 :大鼠气管染毒 ,测定脑组织中GABA含量和GAD活性 ,观察脑神经末梢微囊受体的变化。结果 :UDMH使脑组织中GABA含量和GAD活力显著降低 (P <0 .0 1)。体外试验发现UDMH使GABA与其受体的结合下降 ;体内染毒试验发现在大鼠惊厥发作前GABA受体的结合显著下降 ,惊厥发作时GABA与受体的结合显著上升。结论

周边γ-氨基丁酸通过GABA_B受体调控骶髓后联合核神经元谷氨酸能突触

目的研究突触周边γ-氨基丁酸(ambient GABA)通过GABAB受体调控骶髓后联合核(SDCN)神经元谷氨酸能突触的机制。方法在急性切取的骶段脊髓薄片上,利用全细胞膜片钳法记录骶髓后联合核神经元谷氨酸能兴奋性突触后电流(EPSCs),将GABAB受体用其特异性受体拮抗剂CGP52432阻断,观察谷氨酸突触终末上的GABAB受体被周边GABA作用的影响。结果在突触后GABAB受体被从胞内阻断的条件下,再灌流CGP52432阻断谷氨酸能突触前GABAB受体,可增加刺激引发的EPSCs(eEPSCs)幅度;改变配对刺激的两个EPSC比率(paired-pulse ratio,PPR),并激发沉默突触(silent synapse)。但CGP52432对微小兴奋性突触后电流(mEPSCs)无影响。结论位于SDCN神经元谷氨酸能突触前的GABAB受体受周边GABA调控。这种影响参与调节谷氨酸释放并可能参与痛觉信息在脊髓水平的传递。

Mg^(2+)对神经元保护机制的研究-Mg^(2+)对培养的大鼠海马神经元GABA_A受体介导电流的影响

目的 研究镁离子(Mg2+)对神经元保护的机制。方法 采用全细胞膜片钳技术,研究Mg2+对培养的大鼠海马神经元GABA_A受体介导电流的作用。结果 (1)在钳制电压为-40mV时,GABA可通过GABA_A受体介导产生内向电流;(2)当GABA和Mg2+同时作用时,该电流峰值增高;(3)在Mg2+存在的情况下,GABA的浓度-效应曲线平行左移。结论 Mg2+通过正性变构调节机制影响GABA_A受体的功能,达到保护神经元的作用。

非洲爪蟾卵母细胞GABA_B和GABA_C受体介导的电流反应

实验应用双电极电压箝技术 ,在具有滤泡膜的非洲爪蟾 (Xenopuslaevis)卵母细胞上记录到γ 氨基丁酸(γ aminobutyricacid ,GABA) 激活电流。此GABA 激活电流的特点及有关GABA受体类型的研究和分析如下 :( 1)在 3 5 5 % ( 5 5 / 15 5 )的受检细胞外加GABA可引起一慢的浓度依赖性的外向电流。 ( 2 )GABAA 受体的选择性拮抗剂bicuculline ( 10 -5mol/L)对GABA ( 10 -5mol/L)引起的外向电流无阻断作用 (n =6)。 ( 3 )GABAB 受体的选择性拮抗剂2 hydroxysaclofen ( 10 -4mol/L)能将GABA ( 10 -5mol/L)引起的外向电流可逆性地转变为内向电流 ,后者又可被GABAC 受体的选择性拮抗剂I4AA ( 10 -5mol/L)所消除 (n =6)。 ( 4 )GABAB 受体的特异性激动剂baclofen可引起部分 ( 2 0 % ,12 / 60 )受检细胞产生一慢的浓度依赖性的外向电流。 3× 10 -6 、3× 10 -5及 3× 10 -4mol/L 2 hydroxysaclofen分别阻断baclofen ( 10 -5mol/L) 激活电流 ( 6 3± 3 2 ) % ,( 4 4 1± 2 2 ) %及 ( 86 0± 1 6) % (n =6)。 ( 5 )baclofen激活电流的I V曲线显示逆转电位在 - 96 8± 7 2mV左右 ,此电流可分别被TEA ( 5mmol/L)和BaCl2 ( 2mmol/L)所阻断。以上结果提示 :在非洲爪蟾的卵母细胞上存在内源性GABAB 和GABAC 受体 。