Estradiol is concentrated in tyrosine hydroxylase-containing neurons of the hypothalamus

Localization of [3H]estradiol in tyrosine hydroxylase-containing neurons of rat brain was shown by a combined technique of autoradiography and immunohistochemistry. [3H]Estradiol was concentrated in the nuclei of tyrosine hydroxylase-containing neurons in the nucleus arcuatus, nucleus periventricularis hypothalami, and the zona incerta. These results suggest that estradiol acts directly on dopamine-producing neurons of the tuberoinfundibular system and incertohypothalamic system.     

Delayed transneuronal death of substantia nigra neurons prevented by gamma-aminobutyric acid agonist

In an investigation of the mechanism by which brain lesions result in delayed degeneration of neurons remote from the site of injury, neurons within the caudate nucleus of rats were destroyed by local injection of the excitotoxin ibotenic acid. Treatment resulted in the rapid degeneration of the striatonigral pathway including projections containing the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) and delayed transneuronal death of neurons in the substantia nigra pars reticulata. The distribution of nigral cell loss corresponded to the loss of GABAergic terminals. Neuronal death was prevented by long-term intraventricular infusion of the GABA agonist muscimol. Delayed transneuronal degeneration may be produced by neuronal disinhibition consequent to loss of inhibitory inputs. Replacement of inhibitory transmitters by suitable drugs may prevent some forms of delayed neuronal death.     

兔脑和脊髓内开胃素A免疫阳性神经元和神经纤维的分布

采用免疫组织化学法研究了10只青紫蓝兔脑内开胃素（Orexin） A免疫阳性神经元和神经纤维的分布。结果显示,Orexin A免疫阳性神经元分布于下丘脑的视上核、室旁核、背内侧核、穹隆周核、外侧区、前区和后区以及底丘脑的未定带。Orexin A免疫阳性神经纤维广泛分布于中枢神经系统内,在端脑分布于大脑皮质、尾状核、隔核和杏仁核;在间脑分布于丘脑、下丘脑、上丘脑和垂体;在中脑分布于中央灰质、前丘、后丘、黑质、网状结构和中缝核;在脑桥分布于蓝斑、网状结构和中缝核;在延髓分布于极后区、孤束核和迷走神经背侧运动核;在小脑和脊髓也有分布。     

Maternal oxytocin triggers a transient inhibitory switch in GABA signaling in the fetal brain during delivery

We report a signaling mechanism in rats between mother and fetus aimed at preparing fetal neurons for delivery. In immature neurons, gamma-aminobutyric acid (GABA) is the primary excitatory neurotransmitter. We found that, shortly before delivery, there is a transient reduction in the intracellular chloride concentration and an excitatory-to-inhibitory switch of GABA actions. These events were triggered by oxytocin, an essential maternal hormone for labor. In vivo administration of an oxytocin receptor antagonist before delivery prevented the switch of GABA actions in fetal neurons and aggravated the severity of anoxic episodes. Thus, maternal oxytocin inhibits fetal neurons and increases their resistance to insults during delivery.     

Parvalbumin in most gamma-aminobutyric acid-containing neurons of the rat cerebral cortex

gamma-Aminobutyric acid (GABA) is one of the major inhibitory neurotransmitters in the central nervous system. In the cerebral cortex, GABA-containing cells represent a subpopulation of interneurons. With semithin frozen sections, it is possible to demonstrate that most GABA neurons in the rat somatosensory cortex contain the calcium-binding protein parvalbumin and that parvalbumin is found virtually only in GABA neurons. Parvalbumin seems to influence the electrical properties and enzymatic machinery to modulate neuronal excitability and activity. The specific role of parvalbumin in GABA-containing cortical cells may be related to controlling the effectiveness of their inhibitory action.     

Leonurine protects ischemia-induced brain injury via modulating SOD,MDA and GABA levels

The present study was designed to investigate the protective effects of leonurine, a compound purified from Herba Leonuri that is active on ischemic rat behavior and cortical neurons, and explore the underlying mechanism. The general rat activity, cortical neuron morphology, superoxide dismutase (SOD), malondialdehyde (MDA), g-aminobutyric acid (GABA) and glutamate decarboxylase 67 (GAD67) levels were measured. We found leonurine significantly improve the general activity of rats in an open-field test, which was associated with attenuated neuronal damage induced by ischemia. Moreover, serum SOD activity was significantly greater, MDA level lower in the leonurine group as compared with ischemia group. In addition, GABA content in the cerebral cortex was significantly greater in high-dose leonurine group. Correspondingly, GAD67 protein level coincided with the GABA level. Taken together, our results demonstrated that leonurine attenuated brain injury during ischemia via antioxidative and anti-excitotoxicity effects by targeting GABA and leonurine might become a useful adjuvant neuroprotective agent.     

TIMING BEHAVIOR AFTER LESIONS OF ZONA INCERTA AND MAMMILLARY BODY

Rats with mammillary body lesions produced with an angled approach do not show a "scalloping" in their behavioral records during fixedinterval reinforcement. Control experiments suggest that this effect was due to the electrode piercing the zona incerta, implicating the participation of extrapyramidal structures in timing behavior.     

Channel-mediated tonic GABA release from glia

Synaptic inhibition is based on both tonic and phasic release of the inhibitory transmitter γ-aminobutyric acid (GABA). Although phasic GABA release arises from Ca(2+)-dependent exocytosis from neurons, the mechanism of tonic GABA release is unclear. Here we report that tonic inhibition in the cerebellum is due to GABA being released from glial cells by permeation through the Bestrophin 1 (Best1) anion channel. We demonstrate that GABA directly permeates through Best1 to yield GABA release and that tonic inhibition is eliminated by silencing of Best1. Glial cells express both GABA and Best1, and selective expression of Best1 in glial cells, after preventing general expression of Best1, fully rescues tonic inhibition. Our results identify a molecular mechanism for tonic inhibition and establish a role for interactions between glia and neurons in mediating tonic inhibition.     

外源性γ-氨基丁酸抵抗仔猪氧化应激的效果及机制

【目的】 研究外源性γ-氨基丁酸（GABA）抵抗仔猪氧化应激的作用效果,及海马神经元GABA受体调节凋亡信号通路在其中可能的介导作用,为GABA作为动物应激调节剂的应用提供科学依据。【方法】 基于成功构建的仔猪活体和大鼠海马神经元氧化应激模型,考察外源性GABA对仔猪血清及海马组织中氧化/抗氧化相关指标、仔猪日增重、脑海马GABA受体以及大鼠海马神经元中GABA受体及凋亡信号通路相关基因表达水平的影响。【结果】 低、中、高浓度的GABA灌喂组（LD+OS; MD+OS;HD+OS）仔猪血清的MDA含量均极显著低于氧化应激（OS）组(P<0.01),而GSH水平均极显著高于OS组(P<0.01),同时HD+OS 组仔猪血清T-AOC水平极显著高于OS组和对照组(P<0.01);且高浓度(100 mg·kg^-1 BW)GABA降低仔猪血清MDA含量和增加GSH水平的幅度均高于低浓度(20 mg·kg^-1 BW)和中浓度(60 mg·kg^-1 BW)GABA。因此,后续研究仅考察100 mg·kg^-1 BW GABA的作用效果及其抗氧化应激的机制。OS组仔猪0-7、8-14和0-28日龄的日增重极显著低于对照组(P<0.01),而HD+OS组0-7、8-14和0-28日龄仔猪的日增重极显著高于OS组(P<0.01);OS组仔猪15-28日龄的日增重显著低于对照组(P<0.05),HD+OS组15-28日龄的日增重极显著高于OS组(P<0.01)。以上结果表明,100 mg·kg^-1 BW GABA的灌喂极显著地增加了仔猪的日增重。对照组、OS组和HD+OS组在前、中、后期的腹泻率均无显著差异(P>0.05)。氧化应激组海马组织的MDA含量极显著高于对照组和HD+OS组 (P<0.01),而T-AOC和GSH的水平均极显著低于另外两组(P<0.01),表明GABA能提高仔猪海马组织抗氧化能力。HD+OS组的海马组织GABA_A和GABA_B受体水平均极显著高于对照组和氧化应激组(P<0.01),表明GABA提高了海马组织GABA_A和GABA_B的水平。氧化应激组脑海马Bcl-2蛋白水平显著低于对照组(P<0.05),Bax和Caspase-3蛋白水平极显著高于对照组(P<0.01)。HD+OS组的Bcl-2蛋白水平极显著高于氧化应激组（P<0.01）,Bax蛋白水平极显著低于氧化应激组（P<0.01）,Caspase-3蛋白水平显著低于氧化应激组（P<0.05）。与此一致的是,氧化应激组、GABA+OS+Picrotoxin组和GABA+OS+CGP54626组大鼠海马神经元的Bax和Caspase-3蛋白水平均显著高于对照组和GABA+OS组（P<0.05）,表明GABA缓解了氧化应激状态下海马神经元的损伤,而GABA受体抑制剂的添加阻挡了GABA的抗应激损伤作用。【结论】 GABA降低了仔猪海马的氧化应激水平,而GABA抗应激的作用机制可能与其降低凋亡蛋白基因的表达相关,而GABA_A和GABA_B受体介导了该过程。     

Clonal production and organization of inhibitory interneurons in the neocortex

The neocortex contains excitatory neurons and inhibitory interneurons. Clones of neocortical excitatory neurons originating from the same progenitor cell are spatially organized and contribute to the formation of functional microcircuits. In contrast, relatively little is known about the production and organization of neocortical inhibitory interneurons. We found that neocortical inhibitory interneurons were produced as spatially organized clonal units in the developing ventral telencephalon. Furthermore, clonally related interneurons did not randomly disperse but formed spatially isolated clusters in the neocortex. Individual clonal clusters consisting of interneurons expressing the same or distinct neurochemical markers exhibited clear vertical or horizontal organization. These results suggest that the lineage relationship plays a pivotal role in the organization of inhibitory interneurons in the neocortex.     

Decreased hippocampal inhibition and a selective loss of interneurons in experimental epilepsy

The occurrence of seizure activity in human temporal lobe epilepsy or status epilepticus is often associated with a characteristic pattern of cell loss in the hippocampus. An experimental model that replicates this pattern of damage in normal animals by electrical stimulation of the afferent pathway to the hippocampus was developed to study changes in structure and function that occur as a result of repetitive seizures. Hippocampal granule cell seizure activity caused a persistent loss of recurrent inhibition and irreversibly damaged adjacent interneurons. Immunocytochemical staining revealed unexpectedly that gamma-aminobutyric acid (GABA)-containing neurons, thought to mediate inhibition in this region and predicted to be damaged by seizures, had survived. In contrast, there was a nearly complete loss of adjacent somatostatin-containing interneurons and mossy cells that may normally activate inhibitory neurons. These results suggest that the seizure-induced loss of a basket cell-activating system, rather than a loss of inhibitory basket cells themselves, may cause disinhibition and thereby play a role in the pathophysiology and pathology of the epileptic state.     

Vaccination with a synthetic zona pellucida peptide produces long-term contraception in female mice

The zona pellucida surrounding mouse oocytes is an extracellular matrix composed of three sulfated glycoproteins, ZP1, ZP2, and ZP3. It has been demonstrated that a monoclonal antibody to ZP3 injected into female mice inhibits fertilization by binding to the zona pellucida and blocking sperm penetration. A complementary DNA encoding ZP3 was randomly cleaved and 200- to 1000-base pair fragments were cloned into the expression vector lambda gt11. This epitope library was screened with the aforementioned contraceptive antibody, and the positive clones were used to map the seven-amino acid epitope recognized by the antibody. Female mice were immunized with a synthetic peptide containing this B cell epitope coupled to a carrier protein to provide helper T cell epitopes. The resultant circulating antibodies to ZP3 bound to the zona pellucida of immunized animals and produced long-lasting contraception. The lack of ovarian histopathology or cellular cytotoxicity among the immunized animals may be because of the absence of zona pellucida T cell epitopes in this vaccine.     

低频磁场对紫色红曲菌固态发酵产γ-氨基丁酸的影响

采用低频磁场处理紫色红曲菌(Monascus purpurcus),发酵产生γ-氨基丁酸(GABA)。分别研究了低频磁场强度、处理时间和处理时期对紫红曲霉固态发酵产GABA的影响,并研究了最佳处理条件下,紫红曲霉产GABA的发酵动力学。结果表明:用1.6 m T的低频磁场在紫色红曲菌发酵培养的第4~8 d,其产GABA的增长率提高了31.6%,最终产量增加了35.7%。低频磁场增强或抑制GABA产量可能与低频磁场改变其代谢途径有关。     

Functional coupling of gamma-aminobutyric acid receptors to chloride channels in brain membranes

gamma-Aminobutyric acid (GABA), the major inhibitory neurotransmitter in mammalian brain, is believed to act by increasing membrane conductance of chloride ions. In this study it was found that GABA agonists increased the uptake of chloride-36 by cell-free membrane preparations from mouse brain. This influx was rapid (less than 5 seconds), and 13 micromolar GABA produced a half-maximal effect. The GABA antagonists (bicuculline and picrotoxin) blocked the effect of GABA, whereas pentobarbital enhanced the action. This may be the first demonstration of functional coupling among GABA and barbiturate receptors and chloride channels in isolated membranes. The technique should facilitate biochemical and pharmacological studies of GABA receptor-effector coupling.     

Cortex is driven by weak but synchronously active thalamocortical synapses

Sensory stimuli reach the brain via the thalamocortical projection, a group of axons thought to be among the most powerful in the neocortex. Surprisingly, these axons account for only approximately 15% of synapses onto cortical neurons. The thalamocortical pathway might thus achieve its effectiveness via high-efficacy thalamocortical synapses or via amplification within cortical layer 4. In rat somatosensory cortex, we measured in vivo the excitatory postsynaptic potential evoked by a single synaptic connection and found that thalamocortical synapses have low efficacy. Convergent inputs, however, are both numerous and synchronous, and intracortical amplification is not required. Our results suggest a mechanism of cortical activation by which thalamic input alone can drive cortex.     

Identified sources and targets of slow inhibition in the neocortex

There are two types of inhibitory postsynaptic potentials in the cerebral cortex. Fast inhibition is mediated by ionotropic gamma-aminobutyric acid type A (GABA(A)) receptors, and slow inhibition is due to metabotropic GABA(B) receptors. Several neuron classes elicit inhibitory postsynaptic potentials through GABA(A) receptors, but possible distinct sources of slow inhibition remain unknown. We identified a class of GABAergic interneurons, the neurogliaform cells, that, in contrast to other GABA-releasing cells, elicited combined GABA(A) and GABA(B) receptor-mediated responses with single action potentials and that predominantly targeted the dendritic spines of pyramidal neurons. Slow inhibition evoked by a distinct interneuron in spatially restricted postsynaptic compartments could locally and selectively modulate cortical excitability.     

Subthalamic GAD gene therapy in a Parkinson's disease rat model

The motor abnormalities of Parkinson's disease (PD) are caused by alterations in basal ganglia network activity, including disinhibition of the subthalamic nucleus (STN), and excessive activity of the major output nuclei. Using adeno-associated viral vector-mediated somatic cell gene transfer, we expressed glutamic acid decarboxylase (GAD), the enzyme that catalyzes synthesis of the neurotransmitter GABA, in excitatory glutamatergic neurons of the STN in rats. The transduced neurons, when driven by electrical stimulation, produced mixed inhibitory responses associated with GABA release. This phenotypic shift resulted in strong neuroprotection of nigral dopamine neurons and rescue of the parkinsonian behavioral phenotype. This strategy suggests that there is plasticity between excitatory and inhibitory neurotransmission in the mammalian brain that could be exploited for therapeutic benefit.     

Nerve growth factor gene expression in the developing rat brain

The regulation of nerve growth factor (NGF) protein and NGF messenger RNA (mRNA) in the developing rat brain has been studied to assess the hypothesis that NGF supports the differentiation of cholinergic neurons in the basal forebrain. In the adult, the major targets of these neurons, the hippocampus and neocortex, contain the highest concentrations of NGF mRNA, but comparatively low ratios of NGF protein to its mRNA. In contrast, a high concentration of NGF protein and a low concentration of NGF mRNA were seen in the basal forebrain, consistent with retrograde transport of NGF protein into this region from the neocortex and hippocampus. In these two target regions NGF and NGF mRNA were barely detectable at birth, their concentrations increased to a peak at day 21, and then NGF mRNA, but not NGF protein, declined threefold by day 35. NGF accumulation in the basal forebrain paralleled that in the target regions and preceded an increase in choline acetyltransferase, suggesting that the differentiation of cholinergic projection neurons is indeed regulated by retrogradely transported NGF. In addition, high ratios of NGF protein to NGF mRNA, comparable to that in the basal forebrain, were seen in the olfactory bulb and cerebellum, suggesting that NGF may be transported into these regions by unidentified neurons.     

GABAA-receptor function in hippocampal cells is maintained by phosphorylation factors

Gamma aminobutyric acid (GABA) mediates fast synaptic inhibition in the central nervous system by activating the chloride-permeable GABAA channel. The GABAA conductance progressively diminishes with time when the intracellular contents of hippocampal neurons are perfused with a minimal intracellular medium. This "run down" of the GABA-activated conductance can be prevented by the inclusion of magnesium adenosine triphosphate and calcium buffer in the intracellular medium. The amount of chloride conductance that can be activated by GABA is determined by competition between a calcium-dependent process that reduces the conductance and a phosphorylation process that maintains the conductance.     

On the origin of interictal activity in human temporal lobe epilepsy in vitro

The origin and mechanisms of human interictal epileptic discharges remain unclear. Here, we describe a spontaneous, rhythmic activity initiated in the subiculum of slices from patients with temporal lobe epilepsy. Synchronous events were similar to interictal discharges of patient electroencephalograms. They were suppressed by antagonists of either glutamatergic or gamma-aminobutyric acid (GABA)-ergic signaling. The network of neurons discharging during population events comprises both subicular interneurons and a subgroup of pyramidal cells. In these pyramidal cells, GABAergic synaptic events reversed at depolarized potentials. Depolarizing GABAergic responses in neurons downstream to the sclerotic CA1 region contribute to human interictal activity.