Anaesthetic impairment of immune function is mediated via GABA(A) receptors.

BACKGROUND: GABA(A) receptors are members of the Cys-loop family of neurotransmitter receptors, proteins which are responsible for fast synaptic transmission, and are the site of action of wide range of drugs. Recent work has shown that Cys-loop receptors are present on immune cells, but their physiological roles and the effects of drugs that modify their function in the innate immune system are currently unclear. We are interested in how and why anaesthetics increase infections in intensive care patients; a serious problem as more than 50% of patients with severe sepsis will die. As many anaesthetics act via GABA(A) receptors, the aim of this study was to determine if these receptors are present on immune cells, and could play a role in immunocompromising patients. PRINCIPAL FINDINGS: We demonstrate, using RT-PCR, that monocytes express GABA(A) receptors constructed of α1, α4, β2, γ1 and/or δ subunits. Whole cell patch clamp electrophysiological studies show that GABA can activate these receptors, resulting in the opening of a chloride-selective channel; activation is inhibited by the GABA(A) receptor antagonists bicuculline and picrotoxin, but not enhanced by the positive modulator diazepam. The anaesthetic drugs propofol and thiopental, which can act via GABA(A) receptors, impaired monocyte function in classic immunological chemotaxis and phagocytosis assays, an effect reversed by bicuculline and picrotoxin. SIGNIFICANCE: Our results show that functional GABA(A) receptors are present on monocytes with properties similar to CNS GABA(A) receptors. The functional data provide a possible explanation as to why chronic propofol and thiopental administration can increase the risk of infection in critically ill patients: their action on GABA(A) receptors inhibits normal monocyte behaviour. The data also suggest a potential solution: monocyte GABA(A) receptors are insensitive to diazepam, thus the use of benzodiazepines as an alternative anesthetising agent may be advantageous where infection is a life threatening problem.

GABA release by hippocampal astrocytes

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GABA and its agonists improved visual cortical function in senescent monkeys

Human cerebral cortical function degrades during old age. Much of this change may result from a degradation of intracortical inhibition during senescence. We used multibarreled microelectrodes to study the effects of electrophoretic application of gamma-aminobutyric acid (GABA), the GABA type a (GABAa) receptor agonist muscimol, and the GABAa receptor antagonist bicuculline, respectively, on the properties of individual V1 cells in old monkeys. Bicuculline exerted a much weaker effect on neuronal responses in old than in young animals, confirming a degradation of GABA-mediated inhibition. On the other hand, the administration of GABA and muscimol resulted in improved visual function. Many treated cells in area V1 of old animals displayed responses typical of young cells. The present results have important implications for the treatment of the sensory, motor, and cognitive declines that accompany old age.

GABA Transporter-1 Activity Modulates Hippocampal Theta Oscillation and Theta Burst Stimulation-Induced Long-Term Potentiation

The network oscillation and synaptic plasticity are known to be regulated by GABAergic inhibition, but how they are affected by changes in the GABA transporter activity remains unclear. Here we show that in the CA1 region of mouse hippocampus, pharmacolog

1.初级视觉皮层功能，GABA系统功能在衰老过程中的变化; 2.奖赏机制，极低频磁场的生物学效应研究

1 初级视觉皮层功能，GABA系统功能在衰老过程中的变化 本章首先对衰老过程中神经形态学和神经电生理学上的研究进行了综述，然后报道了作者的博士学位论文研究工作。实验采用神经电生理的手段，探讨初级视觉皮层（primary visual cortex；V1）功能，以及GABA（gamma-aminobutyric acid）系统功能在衰老过程中的变化。 实验1和2均采用单细胞记录技术，检测了中年猴V1细胞的方位选择性、方向选择性、自发放和最大反应，并与年轻和老年猴进行对比；比较了年轻和老年猴V1细胞的感受野外周抑制能力。在实验3中，我们记录了年轻和中年大鼠在给予GABA直接或间接的激动剂，戊巴比妥钠或氯胺酮{通过拮抗NMDA（N-methyl-D-aspartate）受体}后，其皮层的EEG（electroencephalogram）活动，并分析与年龄相关的差异。结果如下： 实验1：中年猴V1细胞的方向选择性和自发放介于年轻猴和老年猴之间，而方位选择性和最大反应与年龄之间没有相关性。 实验2：感受野外周区的最优刺激明显降低了年轻和老年猴具有高方位选择性细胞的比例。同时，年轻猴所有细胞，以及老年猴高方位选择性细胞具有较高的最大抑制比，与它们相比，老年猴无明显方位偏好细胞的最大抑制比显著降低； 实验3：戊巴比妥钠注射后，在年轻和中年大鼠上，alpha (8-12 Hz) 和beta (12-20 Hz) 频段EEG功率增加，theta (4-8 Hz) 功率减少，这些变化在中年大鼠上较为明显。氯胺酮注射后，中年大鼠theta功率比年轻大鼠具有更大幅度的降低。 我们的结果表明，视觉皮层功能的下调在衰老早期就已发生，其机制可能与抑制系统功能普遍降低有关. 2 奖赏机制，极低频磁场的生物学效应研究 本章首先对自然奖赏和药物成瘾机制、极低频磁场生物学效应，以及极低频磁场对奖赏系统的影响进行了综述，然后报道了作者的博士论文研究工作。实验目的是探讨大鼠眶额叶皮质（orbitofrontal cortex；OFC）活动与食物奖赏刺激的相关性，以及极低频磁场对小鼠空间认知能力的影响。 实验1采用EEG记录技术，检测了大鼠OFC在食物奖赏和渴求过程中EEG各频段的功率变化。在实验2中，使用了一种探索型Y-迷宫实验范式，它仅依赖于啮齿类动物天生的探索欲望，避免了奖赏效应的干扰，利用此新型迷宫，我们检测了25和50 Hz磁场对小鼠空间识别记忆能力的影响。其结果如下： 实验1：大鼠OFC的delta频段（2-4 Hz）EEG活动与食物刺激显著相关，其相对功率在食物渴求时下降，在食物奖赏时升高。 实验2：与短时照射相比，长时的50 Hz磁场照射降低了小鼠对新异臂的探索能力，而25和50 Hz磁场暴露都不影响小鼠的活动力。 本研究表明，食物奖赏与OFC的delta频段EEG活动密切相关，而我们以前发现，大鼠和猴OFC的gamma（20-100 Hz）活动与吗啡成瘾相关，提示了OFC在自然奖赏和药物成瘾中具有不同的作用；另外，本实验首次证明，极低频磁场损害了小鼠不依赖于奖赏系统的空间认知能力，而我们先前发现，极低频磁场可以强化吗啡诱导的条件化位置偏好，从而说明极低频磁场对吗啡成瘾具有独特的生物学效应。

Study on the GABA gated channels in the neurosecretory cells of MTXO in the eyestalks of Eriocheir sinensis

The responses to rapid application of gamma-aminobutyric acid (GABA) and the GABA receptor characteristics of MTXO neurosecretory cells in the eyestalks of Chinese mitten-handed crab (Eriocheir sinensis) were examined by whole-cell patch clamp. Under current clamp mode, the depolarization and hyperpolarization were evoked from the three types of neurosecretory cells in response to the GABA (0.1 mmol/L) depending on the Nernst Cl- potential. Under voltage clamp mode, the inward Cl- channel currents (I-GABA) were resolved from all three types of neurosecretory cells in response to GABA (0.01similar to5 mmol/L). The GABA currents were activated within 1 200 ms and peaked within 800 ms. No obviously desensitization was observed during GABA application. The dose-response curve showed usual S-shape, with a just-discernible effect at 0.01 mmol/L and near-saturation at 0.5 mmol/L. The GABA currents had reversal potentials that followed Nernst Cl- potentials when [Cl-] was varied. The pharmacological results revealed that the GABA receptor of the crab neurosecretory cells was sensitive to the Cl- channel blockers picrotoxin and niflumic acid (0.5 mmol/L), insensitive to GABA(A) receptor antagonist bicuculline and GABA(C) receptor agonist cis-4-aminocrotonic acid (CACA 1 mmol/L) and trans-4-aminocrotonic (TACA 1 mmol/L).

GABAA receptor chloride channels are involved in the neuroprotective role of GABA following oxygen and glucose deprivation in the rat cerebral cortex but not in the hippocampus.

Assays on "ex vivo" sections of rat hippocampus and rat cerebral cortex, subjected to oxygen and glucose deprivation (OGD) and a three-hour reperfusion-like (RL) recovery, were performed in the presence of either GABA or the GABA(A) receptor binding site antagonist, bicuculline. Lactate dehydrogenase (LDH) and propidium iodide were used to quantify cell mortality. We also measured, using real-time quantitative polymerase chain reaction (qPCR), the early transcriptional response of a number of genes of the glutamatergic and GABAergic systems. Specifically, glial pre- and post-synaptic glutamatergic transporters (namely GLAST1a, EAAC-1, GLT-1 and VGLUT1), three GABAA receptor subunits (α1, β2 and γ2), and the GABAergic presynaptic marker, glutamic acid decarboxylase (GAD65), were studied. Mortality assays revealed that GABAA receptor chloride channels play an important role in the neuroprotective effect of GABA in the cerebral cortex, but have a much smaller effect in the hippocampus. We also found that GABA reverses the OGD-dependent decrease in GABA(A) receptor transcript levels, as well as mRNA levels of the membrane and vesicular glutamate transporter genes. Based on the markers used, we conclude that OGD results in differential responses in the GABAergic presynaptic and postsynaptic systems.

Neuropeptide Co-Release with Gaba May Explain Functional Non-Monotonic Uncertainty Responses in Dopamine Neurons

Co-release of the inhibitory neurotransmitter GABA and the neuropeptide substance-P (SP) from single axons is a conspicuous feature of the basal ganglia, yet its computational role, if any, has not been resolved. In a new learning model, co-release of GABA and SP from axons of striatal projection neurons emerges as a highly efficient way to compute the uncertainty responses that are exhibited by dopamine (DA) neurons when animals adapt to probabilistic contingencies between rewards and the stimuli that predict their delivery. Such uncertainty-related dopamine release appears to be an adaptive phenotype, because it promotes behavioral switching at opportune times. Understanding the computational linkages between SP and DA in the basal ganglia is important, because Huntington's disease is characterized by massive SP depletion, whereas Parkinson's disease is characterized by massive DA depletion.

Selected Gamma Aminobutyric Acid (GABA) Esters may Provide Analgesia for Some Central Pain Conditions.

Central pain is an enigmatic, intractable condition, related to destruction of thalamic areas, resulting in likely loss of inhibitory synaptic transmission mediated by GABA. It is proposed that treatment of central pain, a localized process, may be treated by GABA supplementation, like Parkinson's disease and depression. At physiologic pH, GABA exists as a zwitterion that is poorly permeable to the blood brain barrier (BBB). Because the pH of the cerebral spinal fluid (CSF) is acidic relative to the plasma, ion trapping may allow a GABA ester prodrug to accumulate and be hydrolyzed within the CSF. Previous investigations with ester local anesthetics may be applicable to some GABA esters since they are weak bases, hydrolyzed by esterases and cross the BBB. Potential non-toxic GABA esters are discussed. Many GABA esters were investigated in the 1980s and it is hoped that this paper may spark renewed interest in their development.

Peripheral markers of the gamma-aminobutyric acid (GABA)ergic system in Angelman's syndrome.

It has recently been demonstrated that patients with Angelman's syndrome who exhibited a deletion on cytogenetic tests show more severe clinical pictures with drug-resistant epilepsy than patients with Angelman's syndrome not carrying the deletion. To verify if this difference in clinical severity can be attributed to genes for the three gamma-aminobutyric acid (GABA)A receptor subunits (GABRB3, GABRA5, GABRG3) located in the deleted region, a possible modification of peripheral markers of the GABAergic system was investigated in 12 subjects with Angelman's syndrome and 20 age-matched subjects (8 with idiopathic epilepsy and 12 not affected by neurologic diseases). The results confirmed a more severe clinical picture, and epilepsy syndrome in particular, in Angelman's syndrome patients with deletions versus patients without deletions. In contrast, biochemical study (based on dosage of plasma levels of GABA and diazepam binding inhibitor, an endogenous ligand of GABAA and peripheral benzodiazepine receptors, showed contradictory results: patients with Angelman's syndrome showed significantly higher levels of GABA and diazepam binding inhibitor than patients without neurologic impairment but significantly lower levels than epileptic controls.

Up-regulation of GABA transporters and GABAA Receptor α1 subunit in tremor rat hippocampus

The loss of GABAergic neurotransmission has been closely linked with epileptogenesis. The modulation of the synaptic activity occurs both via the removal of GABA from the synaptic cleft and by GABA transporters (GATs) and by modulation of GABA receptors. The tremor rat (TRM; tm/tm) is the parent strain of the spontaneously epileptic rat (SER; zi/zi, tm/tm), which exhibits absence-like seizure after 8 weeks of age. However, there are no reports that can elucidate the effects of GATs and GABAA receptors (GABARs) on TRMs. The present study was conducted to detect GATs and GABAR a1 subunit in TRMs hippocampus at mRNA and protein levels. In this study, total synaptosomal GABA content was significantly decreased in TRMs hippocampus compared with control Wistar rats by high performance liquid chromatography (HPLC); mRNA and protein expressions of GAT-1, GAT-3 and GABAR a1 subunit were all significantly increased in TRMs hippocampus by real time PCR and western blot, respectively; GAT-1 and GABAR a1 subunit proteins were localized widely in TRMs and control rats hippocampus including CA1, CA3 and dentate gyrus (DG) regions whereas only a wide distribution of GAT-3 was observed in CA1 region by immunohistochemistry. These data demonstrate that excessive expressions of GAT-1 as well as GAT-3 and GABAR a1 subunit in TRMs hippocampus may provide the potential therapeutic targets for genetic epilepsy.

GABA IN THE NERVOUS-SYSTEM OF PARASITIC FLATWORMS

In an immunocytochemical study, using an antiserum and a monoclonal antibody specific for the amino acid, gamma-aminobutyric acid (GABA), GABA-like immunoreactivity (GLIR) has been demonstrated for the first time in parasitic flatworms. In Moniezia expansa (Cestoda), GLIR was seen in nerve nets which were closely associated with the body wall musculature and in the longitudinal nerve cords. In the liver fluke Fasciola hepatica (Trematoda), the GLIR occurred in the longitudinal nerve cords and lateral nerves in the posterior half of the worm. GLIR was also detected in subtegumental fibres in F. hepatica. The presence of GABA was verified, using high-pressure liquid chromatography coupled with fluorescence detection. The concentration of GABA (mean+/-S.D.) in M. expansa anterior region was 124.8+/-15.3 picomole/mg wet weight, while in F. hepatica it was 16.8+/-4.9 picomole/mg. Since several insecticides and anti-nematodal drugs are thought to interfere with GABA-receptors, the findings indicate that GABAergic neurotransmission may be a potential target for chemotherapy in flatworms too.