γ-氨基丁酸、谷氨酸等对蝙蝠中脑下丘薄片神经元诱发电活动的影响

采用脑薄片细胞外记录法,研究了γ－氨基丁酸（ＧＡＢＡ）及其拮抗剂荷包牡丹碱（Ｂｉｃｕｃｕｌｌｉｎｅ）、激动剂氨苯氨丁酸（Ｂａｃｌｏｆｅｎ）和谷氨酸（Ｇｌｕ）及其拮抗剂－２ＡＰＶ、挑动剂ＮＭＤＡ中脑下丘薄片上进行。双股绞合绝缘镍络丝刺激电极,置于下丘外侧核（ＩＣｘ）给予电刺激。五管玻璃微电极微电泳药物和记录细胞诱发场电位（Ｆｉｅｌｄ Ｐｏｔｅｎｔｉａｌ）。在下丘中央核（ＩＣｃ）共记录了１０２例诱发的     

N-甲基-D-天冬氨酸(NMDA)及荷包牡丹碱对不同年龄蝙蝠下丘神经元听反应的影响

分别对出生后第２周和第４周的中华鼠耳蝠（Ｍｙｏｔｉｓｃｈｉｎｅｎｓｉｓ）中脑下丘中央核１２１个听神经元进行了考察,同时与成年动物进行比较。结果表明,微电泳ＮＭＤＡ对下丘中央核绝大部分听神经元（２周龄、４周龄和成年动物分别为９６％、９５％和９６％）具有易化性影响,表现为听反应脉冲发放率增加、反应阈值下降、频率调谐曲线增宽。ＮＭＤＡ的易化性效应部分地与动物的周龄相关,表现为对听反应阈值和听反应脉冲发放率的易化效应在出生后２－４周逐渐增强,但４周以后的易化效应趋缓;微电泳ＧＡＢＡＡ受体的特异性拮抗剂Ｂｉｃｕｃｕｌｉｎｅ,对神经元的听反应也呈现易化性影响,表现为听反应脉冲发放率增加,反应阈值降低和频率调谐曲线增宽等。实验结果还提示,ｂｉｃｕｃｕｌｉｎｅ对下丘神经元听反应的易化作用,在出生后早期呈持续增强趋势。ＮＭＤＡ和ｂｉｃｕｃｕｌｉｎｅ的效应与动物周龄之间的关系略有差异,是否提示着下丘中央核ＮＭＤＡ受体和ＧＡＢＡＡ受体在出生后的发育进程有所差别,尚待进一步探讨。     

鲫鱼脑氨基酸类神经递质受体在两栖类卵母细胞中的表达

两栖类卵母细胞表达系统经注射鲫鱼脑ｍＲＮＡ后可表达多种神经递质受体和某些离子通道。本工作利用电压箝方法结合药理学手段对ＧＡＢＡ受体和谷氨酸离子型受体作了较详细的研究。结果表明,由ＧＡＢＡ诱发的电流反应中,约９０％由ＧＡＢＡＡ受体介导,乘余约１０％的成分对ＧＡＢＡＡ受体的专一性拮抗剂Ｂｉｃｕｃｕｌｌｉｎｅ不敏感,而ＧＡＢＡＢ受体的专一性激动剂Ｂａｃｌｏｆｅｎ不能引进电流反应,因此这部分受体特性与ＧＡ     

杏仁体影响兔内膝体双耳神经元的声反应

实验在２３只三碘季胺酚麻痹的新西兰兔上进行。采用记录单个神经元放电的方法,观察了刺激杏仁体对内膝体（ｍｅｄｉａｌｇｅｎｉｃｕｌａｔｅｂｏｄｙ,ＭＧＢ）６５个双耳神经元声反应的影响。实验结果表明：杏仁刺激对其中２１个神经元的活动产生抑制性影响（占３２．３％）。刺激杏仁外侧核或基底核,既能抑制内膝体神经元对单侧耳声刺激的反应,也可抑制该神经元对双耳声刺激的反应。杏仁体所产生的这种抑制性影响的潜伏期最短为２ｍｓ,表明是经由杏仁－内膝体单突触联系。一般认为,接受双耳信息的神经元与声源定位有关,因此可以推测杏仁体的活动可以干预动物对声源的定位。     

N-甲基-D-天冬氨酸和γ-氨基丁酸对蝙蝠下丘薄片诱发电活动的影响

在４７只不同年龄的蝙蝠的８６张中脑下丘的冠状薄片上,电刺激外侧丘系,记录到１４９例下丘中央核的诱发场电位。分别观察了微电泳Ｎ－甲基－Ｄ－天冬氨酸（ＮＭＤＡ）、２－氨基－５－磷酸戊酸（２－ＡＰＶ）、γ－氨基丁酸（ＧＡＢＡ）、荷包牡丹碱（ｂｉｃｕｃｕｌｌｉｎｅ）等对下丘中央核诱发场电位幅度的影响。实验结果表明,外侧丘系对蝙蝠中脑下丘中央核的传入影响可能主要由由ＧＡＢＡ、Ｇｌｕ以及ＧＡＢＡＡ、ＮＭＤＡ受     

孕酮诱发豚鼠精子顶体反应过程中的Ca^2＋内流通道

在体外,孕酮和γ－氨基丁酸可明显地引起豚鼠精子顶体反应,并且两者合并使用,对顶体瓜在的诱发有协同作用,这种反应不依赖于细胞外Ｃｌ＾－,在含Ｃｌ＾－培养液中,ＧＡＢＡＡ受体拮抗剂ｐｉｃｒｏｔｏｘｉｎ和ｂｏｃｕｃｕｌｌｉｎｅ不抑制孕酮诱发的顶体反应,而抑制ＧＡＢＡ诱发的顶体反应。相反在缺Ｃｌ＾－培养液中,ｐｉｃｒｏｔｏｘｉｎ则可明显地抑制孕酮和ＧＡＢＡ诱发的顶体反应。孕酮和ＧＡＢＡ诱发的顶体反应均可被     

螽斯听觉中间神经元TN2的声反应特征以及GABA对其影响

采用单细胞电生理记录技术,对螽斯Ｇａｍｐｏｃｌｅｉｓ ｇｒａｔｉｏｓａ听觉双轴突中间神经元ＴＮ２的声反应放电活动的基本特征进行了观测,发现ＴＮ２的放电模式为“ｐｈａｓｉｃ”型,最敏感频率为１３ｋＨｚ,反应阈值为３１ｄＢ ＳＰＬ,是一个高灵敏、宽带通的神经元。还研究了抑制性神经递质ＧＡＢＡ及其拮抗剂苦毒素对ＴＮ２声反应的影响,发现ＧＡＢＡ能抑制ＴＮ２的放电活动,而苦毒素则将其放电模式改变为“ｔｏｎｉ     

侧脑室注射一叶萩碱的心血管效应及作用机制

在麻醉大鼠侧脑室注射左旋一叶Ｑｉｕ碱（Ｌ－Ｓｅｃ）,记录动脉血压（ＡＰ）、心率（ＨＲ）及肾交感神经放电（ＲＳＮＤ）,观察前脑室周系统ＧＡＢＡ能紧张性活动改变引起的心血管效应。结果如下：（１）Ｌ－Ｓｅｃ可引起ＲＳＮＤ增加、ＡＰ升高和ＨＲ加快,并呈一定剂量－效应关系;但Ｌ－Ｓ盈余 于ｂｉｃｕｃｕｌｌｉｎｅ（Ｂｉｃ）。（２）Ｌ－Ｓｅｃ既能拮抗ｍｕｓｃｉｍｏｌ（Ｍｕｓ）,又能拮抗ｂａｃｌｏｆｅｎ（Ｂａｃ）     

GABA介导杏仁外侧核对皮层A Ⅰ区神经元声反应的抑制:在体微电泳研究

在SD大鼠上应用多顺利完成微电极方法,观察微电泳CABA及其受体的拮抗剂或激动剂对杏仁外侧核（LA）抑制皮层AⅠ神经元声反应效应的影响。结果显示,电泳GABA能抑制皮层AⅠ区神经元的电活动,电泳GABAA受体拮抗剂bicuculline（BIC）则能易化其反应;电刺激LA能抑制皮层AⅠ区听神经元声反应,电泳GABA产生类拟于刺激LA的抑制效应;LA对皮层AⅠ区神经的抑制效应能被BIC所翻转,而不能被什氨酸受体拮抗剂strychnine所翻转,电泳GABAB型受体例激动剂baclofen对神经元声反应无影响。上术结果表明,GABA可能是介民LA抑制皮层AⅠ区神经元声反应的最终递质,并且是通过GABAA受体作用的。     

乙酰胆碱,谷氨酸与GABA对丘脑腹内侧核神经元活动的影响

本文采用微电泳方法观察到在大鼠丘脑腹内侧核（ＶＭ）,微电泳给予乙酰胆碱（ＡＣＨ）使所有受试神经元自发放电频率加快,谷氨酸（ＧＬＵ）使大多数神经元放电加快,它们的作用依赖于电流强度;而γ氨基丁酸（ＧＡＢＡ）和氯苯氨丁酸则抑制大多数神经元的放电活动,但前者的作用快速而暂短,而后者的作用相对缓慢而持久。在微电泳ＡＣＨ或ＧＬＵ的过程中,给予ＧＡＢＡ可拮抗它们的兴奋作用。双钴碱使大多数神经元的自发放电频率加快,而阿托品和ＭＫ８０１对自发放电的影响较小。这些结果表明ＧＡＢＡ,ＡＣＨ和ＧＬＵ等递质活动在同一ＶＭ神经元有重要的会聚作用;ＧＡＢＡ对ＶＭ神经元有紧张性抑制作用。     

Evidence for GABA-mediated control of putative nociceptive modulating neurons in the rostral ventromedial medulla: iontophoresis of bicuculline eliminates the off-cell pause.

This study was undertaken to test the hypothesis that gamma-aminobutyric acid (GABA) is an endogeneous neurotransmitter regulating the activity of a class of putative nociceptive modulatory neurons (termed "off-cells") in the rostral ventromedial medulla (RVM) of the barbiturate-anesthetized rat. Off-cells, which are believed to correspond to the RVM output neuron that inhibits nociceptive processing at the level of the spinal cord, exhibit an abrupt pause in firing that begins immediately prior to the occurrence of the tail flick response (TF), a nocifensive reflex evoked by application of noxious heat to the tail. Single-unit recording and iontophoretic techniques were used to examine the ability of the GABAA receptor antagonist bicuculline methiodide (BIC) to antagonize selectively the characteristic off-cell pause. Iontophoretic application of BIC (5-30 nA) blocked the TF-related pause in each of the off-cells tested. This effect of BIC was generally slow in onset, and outlasted the period of application by several minutes. BIC iontophoresis also eliminated the cyclic alternation between active and silent periods that is often displayed by off-cells in lightly anesthetized rats. BIC application did not have a consistent effect on the firing of two other classes of RVM neurons ("on-cells" and "neutral cells"). Iontophoretically applied BIC antagonized the inhibitory effect of iontophoretically applied GABA, but not that produced by glycine. The glycine receptor antagonist strychnine did not mimic the action of BIC on off-cell activity. These data demonstrate antagonism of a synaptically evoked response using iontophoretic application of BIC, and provide strong evidence that the inhibitory neurotransmitter GABA mediates the TF-related off-cell pause. Taken together with behavioral experiments demonstrating that a GABA-mediated inhibitory process within RVM is crucial in permitting execution of the TF response, the present observations point to the significant functional relevance of GABA transmission within RVM in modulation of nociception.     

γ—氨基丁酸在联合皮层抑制C类纤维皮层诱发电位效应中的作用

电刺激猫大脑皮层前外侧回联合区(ALA)对隐神经C类纤维传入引起的体感皮层(SI)诱发电位(C-CEP)有明显的抑制作用;侧脑室注射γ-氨基丁酸(GABA)能使C-CEP的幅值显著变小,潜伏期延长,表明GABA对C-CEP也有抑制作用;侧脑室注射GABA受体拮抗剂荷包牡丹硷后,电刺激ALA对C-CEP的抑制作用明显减弱,提示内源性GABA的释放可能参与大脑皮层联合区对C-CEP的调制过程。     

Various effects of angiotensin II on amygdaloid neuronal activity in normotensive control and hypertensive transgenic [TGR(mREN-2)27] rats.

The effects of iontophoretically ejected angiotensin II (Ang II) on the firing rate of neurons in the basolateral complex and the central and cortical amygdala were investigated in two strains of urethane anesthetized rats. In normotensive Sprague-Dawley rats, Ang II induced a significant increase in the discharge rate of responsive amygdaloid neurons. In contrast, in the hypertensive transgenic [TGR(mREN-2)27] rats with higher brain Ang II level, Ang II more often caused inhibitory effects on the amygdaloid firing rate in comparison with controls. The distribution of nonresponsive, excited, and inhibited neurons differed significantly in the two rat strains. Moreover, the responsiveness of amygdaloid neurons was significantly higher in transgenic rats in comparison with controls. Both the increase and the decrease in the firing rate caused by Ang II could be blocked either by angiotensin AT(1) or by AT(2) receptor-specific antagonists. In many cases, the Ang II-induced decrease in the firing rate was antagonized by bicuculline, a gamma-aminobutyric acid (GABA(A)) antagonist. The higher responsiveness of amygdaloid neurons in transgenic rats as well as the predominance of inhibitory effects, presumedly mediated by GABAergic interneurons, could change the output of the amygdala and its influence on thirst, kidney, and cardiovascular function or on processes of learning and anxiety.     

Evidence that glycine and GABA mediate postsynaptic inhibition of bulbar respiratory neurons in the cat.

Experiments were carried out on decerebrate cats to identify transsynaptic mediators of spontaneous postsynaptic inhibition of bulbar inspiratory and postinspiratory neurons. Somatic membrane potentials were recorded through the central micropipette of a coaxial multibarreled electrode. Blockers of type A gamma-aminobutyric acid (GABA-A) and glycine receptors were iontophoresed extracellularly from peripheral micropipettes surrounding the central pipette. Effective antagonism was demonstrated by iontophoresis of agonists with antagonists; application of strychnine antagonized the action of glycine but not GABA, and application of bicuculline antagonized the action of GABA but not glycine. In both types of neurons, iontophoresis of either antagonist depolarized the somatic membrane and increased input resistance throughout the respiratory cycle. Bicuculline preferentially depolarized the somatic membrane in both types of neurons during inactive phases. Strychnine increased the firing rate of inspiratory neurons during inspiration despite maintenance of somatic membrane potential at preiontophoresis levels. Tetrodotoxin reduced the effects of iontophoresed bicuculline and strychnine, suggesting that the action of the antagonists required presynaptic axonal conduction. The present results suggest that presynaptic release of both GABA and glycine contributes to tonic postsynaptic inhibition of bulbar respiratory neurons. GABA-A receptors appear to contribute to inhibition during inactive phases in inspiratory and postinspiratory neurons, whereas glycinergic mechanisms appear to contribute to inspiratory inhibition in inspiratory neurons.     

Transmitters and pathways mediating inhibition of spinal itch-signaling neurons by scratching and other counterstimuli

Scratching relieves itch, but the underlying neural mechanisms are poorly understood. We presently investigated a role for the inhibitory neurotransmitters GABA and glycine in scratch-evoked inhibition of spinal itch-signaling neurons in a mouse model of chronic dry skin itch. Superficial dorsal horn neurons ipsilateral to hindpaw dry skin treatment exhibited a high level of spontaneous firing that was significantly attenuated by cutaneous scratching, pinch and noxious heat. Scratch-evoked inhibition was nearly abolished by spinal delivery of the glycine antagonist, strychnine, and was markedly attenuated by respective GABA(A) and GABA(B) antagonists bicuculline and saclofen. Scratch-evoked inhibition was also significantly attenuated (but not abolished) by interruption of the upper cervical spinal cord, indicating the involvement of both segmental and suprasegmental circuits that engage glycine- and GABA-mediated inhibition of spinal itch-signaling neurons by noxious counterstimuli.     

5-HT对弓状核神经元的直接兴奋作用和通过GABA能局部神经元实现的抑制作用

用大鼠离体灌流脑片的细胞外单一神经元电生理记录技术,观察了5－HT对弓状核神经元自发放电的影响。结果表明：（1）在随机选取的149个神经元中,有33个（22．2％）可被5－HT兴奋,82个（55．0％）被抑制,其余34个（22．8％）出现双相反应或不出现反应;（2）用低Ca^2 -高Mg^2 人工脑脊液替换正常人工脑脊液后,5－HT引起的兴奋效应仍可出现,但5－HT引起的抑制效应不再出现;（3）5－HT受体的非选择性拮抗剂cyproheptadine对5－HT引起的兴奋或抑制都有阻断作用;（4）用GABA受体拮抗剂bicuculline(Bic)可以阻断5－HT引起的抑制作用。据此推测：（1）5－HT的兴奋效应对低Ca^2 环境不敏感,因而是5－HT直接作用于所记录细胞的结果;（2）5－HT的抑制效应对低C a^2 敏感,并可被Bic所阻断,因而－HT可能是兴奋了局部GABA能中间神经元,后者再通过释放GABA抑制了所记录的神经元。     

家兔伏核—杏仁核神经通路在吗啡镇痛中的作用

用辐射热照射家兔鼻嘴侧部皮肤,测量其躲避反应潜伏期作为痛反应阈,简称痛阈。通过预先埋植的慢性套管向伏核或杏仁核内进行注射,结果表明:(1)在家兔的伏核内微量注射吗啡可产生镇痛作用,该作用可被杏仁核内注射纳洛酮所削弱,并有量效依从关系;在杏仁核内注射甲啡肽抗血清(ME AS)或β-內啡肽抗血清(β-EP AS)亦可削弱上述镇痛作用;(2)在杏仁核内微量注射吗啡可产生镇痛作用,此作用不能被伏核内注射纳洛酮所阻断;(3)在伏核内注射吗啡所产生的镇痛作用可被同一部位注射γ-氨基丁酸(GAEA)受体阻断剂氯甲基荷包牡丹碱所增强,被 GABA 受体激动剂异鹅羔胺所削弱。上述结果提示:在家兔脑内从伏核到杏仁核可能存在一条与镇痛有关的神经通路,伏核内的阿片样物质及杏仁核内的甲啡肽,β-内啡肽可能参与镇痛信息的传递,而伏核内的 GABA 可能有对抗吗啡镇痛的作用。     

Effect of GABAergic substances on firing rate and thermal coefficient of hypothalamic neurons in the juvenile chicken

The goal of the study is to investigate the GABAergic action on firing rate (FR) and temperature coefficient (TC) on hypothalamic neurons in the juvenile chicken. Extracellular recordings were obtained from 37 warm-sensitive, 32 cold-sensitive and 56 temperature-insensitive neurons in brain slices to determine the effect of GABA(A)-receptor agonist muscimol, GABA(A)-receptor antagonist bicuculline, GABA(B)-receptor agonist baclofen and GABA(B)-receptor antagonist CGP 35348. Muscimol and baclofen in equimolar concentrations (1 microM) significantly inhibited FR of the neurons, regardless of their type of thermosensitivity. In contrast, bicuculline, as well as CGP 35348 (10 microM) increased FR of the majority of the neurons. The TC of most chick hypothalamic neurons could not be estimated during muscimol application because FR was completely inhibited. GABA(B)-receptor agonist specifically increased TC. This effect was restricted to cold-sensitive neurons, which were determined in a high number. The TC was significantly increased (p<0.05) by baclofen and significantly decreased (p<0.05) by CGP 35348. The effects of muscimol and baclofen on FR and TC were prevented by co-perfusion of the appropriate antagonists bicuculline and CGP 35348. The results suggest that the fundamental mechanisms of GABAergic influence on temperature sensitive and insensitive neurons in the chicken PO/AH are conserved during evolution of amniotes.     

Mediation by calcium/calmodulin-dependent protein kinase II of suppression of GABAA receptors by NMDA

Using nystatin-perforated whole-cell recording configuration, the modulatory effect of N-methyl-D-aspartate (NMDA) on -aminobutyric acid (GABA)-activated whole-cell currents was investigated in neurons freshly dissociated from the rat sacral dorsal commissural nucleus (SDCN). The results showed that: (I) NMDA suppressed GABA- and muscimol (Mus)-activated currents (IGABA and Imus), respectively in the Mg2+-free external solution containing 1 mol/L glycine at a holding potential (VH) of 40 mV in SDCN neurons. The selective NMDA receptor antagonist, D-2-amino-5-phosphonovaleric acid (APV, 100 mol/L), inhibited the NMDA-evoked currents and blocked the NMDA-induced suppression of IGABA; (ii) when the neurons were incubated in a Ca2+-free bath or pre-loaded with a membrane-permeable Ca2+ chelator, BAPTA AM (10 mol/L), the inhibitory effect of NMDA on IGABA disappeared. Cd2+ (10 mol/L) or La3+ (30 mol/L), the non-selective blockers of voltage-dependent calcium channels, did not affect the suppression of IGABA by NMDA application; (iii) the suppression of IGABA by NMDA was inhibited by KN-62, a calcium/calmodulin-dependent protein kinase II (CaMKII) inhibitor. These results indicated that the inhibition of GABA response by NMDA is Ca2+-dependent and CaMKII is involved in the process of the Ca2+-dependent inhibition.