Properties of synaptic transmission from the reticular formation dorsal to the facial nucleus to trigeminal motoneurons during early postnatal development in rats

We previously reported that electrical stimulation of the reticular formation dorsal to the facial nucleus (RdVII) elicited excitatory masseter responses at short latencies and that RdVII neurons were antidromically activated by stimulation of the trigeminal motor nucleus (MoV), suggesting that excitatory premotor neurons targeting the MoV are likely located in the RdVII. We thus examined the properties of synaptic transmission from the RdVII to jaw-closing and jaw-opening motoneurons in horizontal brainstem preparations from developing rats using voltage-sensitive dye, patch-clamp recordings and laser photostimulation. Electrical stimulation of the RdVII evoked optical responses in the MoV. Combined bath application of the non-N-methyl-d-aspartate (non-NMDA) receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), and the NMDA receptor antagonist DL-2-amino-5-phosphonopentanoic acid (APV) reduced these optical responses, and addition of the glycine receptor antagonist strychnine and the GABA_A receptor antagonist bicuculline further reduced the remaining responses. Electrical stimulation of the RdVII evoked postsynaptic currents (PSCs) in all 19 masseter motoneurons tested in postnatal day (P)1–4 rats, and application of CNQX and the NMDA receptor antagonist (±)-3(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP) reduced the PSC amplitudes by more than 50%. In the presence of CNQX and CPP, the GABA_A receptor antagonist SR95531 further reduced PSC amplitude, and addition of strychnine abolished the remaining PSCs. Photostimulation of the RdVII with caged glutamate also evoked PSCs in masseter motoneurons of P3–4 rats. In P8–11 rats, electrical stimulation of the RdVII also evoked PSCs in all 14 masseter motoneurons tested, and the effects of the antagonists on the PSCs were similar to those in P1–4 rats. On the other hand, RdVII stimulation evoked PSCs in only three of 16 digastric motoneurons tested. These results suggest that both neonatal and juvenile jaw-closing motoneurons receive strong synaptic inputs from the RdVII through activation of glutamate, glycine and GABA_A receptors, whereas inputs from the RdVII to jaw-opening motoneurons seem to be weak.     

Effects of 17β-estradiol on glutamate synaptic transmission and neuronal excitability in the rat medial vestibular nuclei

We investigated the effects of the neurosteroid 17β-estradiol (E₂) on the evoked and spontaneous activity of rat medial vestibular nucleus (MVN) neurons in brainstem slices. E₂ enhances the synaptic response to vestibular nerve stimulation in type B neurons and depresses the spontaneous discharge in both type A and B neurons. The amplitude of the field potential, as well as the excitatory post-synaptic potential (EPSP) and current (EPSC), in type B neurons, are enhanced by E₂. Both effects are long-term phenomena since they outlast the drug washout. The enhancement of synaptic response is mainly due to facilitation of glutamate release mediated by pre-synaptic n-methyl-d-aspartate receptors (NMDARs), since the reduction of paired pulse ratio (PPR) and the increase of miniature EPSC frequency after E₂ are abolished under D-(−)-2-amino-5-phosphonopentanoic acid (AP-5). E₂ also facilitates post-synaptic NMDARs, but it does not affect directly α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) and group I-metabotropic glutamate receptors (mGluRs-I). In contrast, the depression of the spontaneous discharge of type A and type B neurons appears to depend on E₂ modulation of intrinsic ion conductances, as the effect remains after blockade of glutamate, GABA and glycine receptors (GlyRs). The net effect of E₂ is to enhance the signal-to-noise ratio of the synaptic response in type B neurons, relative to resting activity of all MVN neurons. These findings provide evidence for a novel potential mechanism to modulate the responsiveness of vestibular neurons to afferent inputs, and so regulate vestibular function in vivo.     

Endogenous nociceptin/orphanin FQ (N/OFQ) contributes to haloperidol-induced changes of nigral amino acid transmission and parkinsonism: a combined microdialysis and behavioral study in naïve and nociceptin/orphanin FQ receptor knockout mice

The contribution of endogenous nociceptin/orphanin FQ (N/OFQ) to neuroleptic-induced parkinsonism has been evaluated in haloperidol-treated mice. Pharmacological blockade of N/OFQ receptors (NOP) via systemic administration of 1-[(3R,4R)-1-cyclooctylmethyl-3-hydroxymethyl-4-piperidyl]-3-ethyl-1,3-dihydro-2H benzimidazol-2-one (J-113397, 0.01–10 mg/kg i.p.) or central injection of [Nphe¹,Arg¹⁴,Lys¹⁵]N/OFQ-NH₂ (UFP-101, 10 nmol i.c.v.) attenuated (0.8 mg/kg) haloperidol-induced motor deficits as evaluated by a battery of behavioral tests providing complementary information on motor parameters: the bar, drag and rotarod tests. A combined neurochemical and behavioral approach was then used to investigate whether the substantia nigra reticulata could be involved in antiakinetic actions of J-113397. Microdialysis combined to the bar test revealed that haloperidol (0.3 and 0.8 mg/kg i.p.) caused a dose-dependent and prolonged elevation of immobility time (i.e. akinesia) which was associated with an increase in nigral glutamate and a reduction in GABA release. Conversely, J-113397 (1 mg/kg) alone reduced glutamate and elevated nigral GABA release, and when challenged against haloperidol, counteracted its behavioral and neurochemical effects. Microdialysis coupled to behavioral testing also demonstrated that NOP receptor knockout mice were resistant to haloperidol (0.3 mg/kg) compared to wild-type mice, lack of response being associated with a reversal of glutamate release facilitation into inhibition and no change in nigral GABA release. This study provides pharmacological and genetic evidence that endogenous N/OFQ contributes to haloperidol-induced akinesia and changes of amino acid transmission in mice. Moreover, it confirms the view that NOP receptor antagonists are capable of reversing akinesia across species and genotypes and may prove effective in relieving neuroleptic-induced parkinsonism.     

C/EBPα参与小鼠胰岛β细胞囊泡谷氨酰胺转运子2基因表达的调控

目的:探讨转录调节因子CCAAT增强子结合蛋白α(C/EBPα)在小鼠胰岛β细胞株MIN6的囊泡谷氨酰胺转运子2(VGLUT2)基因表达过程中的调控作用。方法:克隆小鼠VLGUT2基因的启动子区,并对其中C/EBPα的结合位点进行了核酸定点突变,以荧光素酶活力方法观察突变后的启动子活性改变情况。通过电泳迁移率实验(EMSA)检测C/EBPα与含有小鼠VGLUT2启动子区核酸序列的核苷核探针的结合能力,以CEBPαsiRNA特异性抑制转录调控因子C/EBPα的基因表达,通过荧光素酶,RT-PCR和Western blotting方法观察抑制C/EBPα基因表达后小鼠VGLUT2的基因表达情况。结果:在对小鼠VGLUT2启动子区C/EBPα结合位点进行核酸定点突变后,小鼠VGLUT2启动子活性下降约50%,EMSA实验表明C/EBPα可与小鼠VGLUT2启动子区结合,当以C/EBPαsiRNA特异性地下调C/EBPα的表达时,小鼠VGLUT2的启动子活性、mRNA和蛋白水平也相应各自下降约60%、40%及45%。结论:C/EBPα参与了小鼠VGLUT2的基因表达调控。     

人参皂甙Rd对皮层神经元兴奋性毒性损伤后胞内游离钙的影响

目的:探讨人参皂甙Rd(Ginsenoside Rd,GSRd)对皮层神经元兴奋性毒性损伤后细胞内游离钙离子浓度变化的影响。方法:采用原代方法培养大鼠皮层神经元,免疫荧光染色鉴定神经元纯度。应用激光共聚焦显微镜,观察GSRd对谷氨酸(Glutamate,Glu)和N-甲基-D-天门冬氨酸(NMDA)刺激后神经元胞内游离钙离子浓度变化的影响。使用钙离子荧光探针Fluo-4,AM标记细胞内游离钙,以Fluo-4的荧光强度反映细胞内游离钙浓度变化。结果:空白对照组荧光强度没有明显变化,而高浓度Glu刺激可迅速升高神经元胞内的荧光强度;在给予GSRd干预时,荧光强度升高的幅度明显降低,与MK-801的作用相似;NMDA刺激亦可使神经元胞内荧光强度明显升高,而加入GSRd干预时,荧光强度升高的幅度较NMDA损伤组有明显减小。结论:GSRd能够抑制高浓度Glu和NMDA引起的大量钙内流,提示减轻兴奋性毒性损伤过程中的钙超载可能是GSRd神经保护作用的机制之一。     

Effect of antibodies against AMPA glutamate receptors on brain neurons in primary cultures of the cerebellum and hippocampus

Rabbit antibodies against GluR₁ subunit of AMPA glutamate receptors in a concentration of 1 μg/ml significantly increased intracellular Ca²⁺ concentration and decreased mitochondrial potential in hippocampal neurons, i.e. produced changes typical of the influence of glutamate in toxic concentrations. In cerebellar neurons rabbit antibodies potentiated glutamate-induced increase in intracellular Ca²⁺ concentration and significantly decreased the mitochondrial potential (compared to the level observed after application of glutamate alone). The exposure of cultured cerebellar neurons to antibodies in a concentration of 0.1 μg/ml for 24 h was followed by a 50% decrease in ATP concentration and development of neuronal necrosis. Our results attest to an important role of autoimmune damage to neurons during hyperstimulation of glutamate receptors. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 142, No. 7, pp. 59–62, July, 2006     

The effect of monosodium glutamate on parotid salivary flow in comparison to the response to representatives of the other four basic tastes

Parotid salivary flow was recorded from eight fit and healthy subjects using modified Lashley cups connected to an instantaneous flow meter in response to gustatory stimuli. The gustatory stimuli were monosodium glutamate (MSG), sodium chloride, sucrose, magnesium sulphate and citric acid. Stimuli were applied for 30 s, and repeated after the flows had returned to baseline following the rinse. Subjects were a significant source of variation for salivary response to each different test stimuli (p<0.001). The normalised salivary flow showed a strong correlation to concentration for all test stimuli (p<0.0001). The parotid salivary flow to MSG (umami) showed a dose-dependant response in which both Na(+) and glutamate ions contributed. The overall order of relative salivary flow responses from highest to lowest flows was citric acid (sour)>MSG (umami)>NaCl (salt)>sucrose (sweet)>=magnesium sulphate (bitter). The relative responses of the peak salivary flows showed the same ordered relation. The peak salivary flow provided a greater contribution to the response to citric acid, NaCl and MSG compared to the response to sucrose and magnesium sulphate.     

Acute Treatment of Noise Trauma with Local Caroverine Application in the Guinea Pig

Intense sound stimulation may result in excessive glutamate release from the inner hair cells, resulting in binding to the post-synaptic glutamate receptors and leading to neuronal degeneration and functional impairment. In this study we investigated the therapeutic effect and time window of caroverine, an N-methyl-D-aspartate and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor antagonist, on noise-induced hearing loss. Guinea pigs were exposed to one-third octave band noise centered at 6.3 kHz (110 dB sound pressure limit) for 1 h. One or 24 h after noise exposure, caroverine was applied to the round window membrane. Auditory brainstem responses were recorded at regular time intervals. It was shown that caroverine could significantly decrease hearing impairment after noise trauma when applied 1 but not 24 h after noise exposure.     

Antidiabetic and antioxidant activities of Toddalia asiatica (L.) Lam. leaves in Streptozotocin induced diabetic rats

Ethnopharmacological relevance

The leaves of Toddalia asiatica (L.) Lam. have been utilized traditionally for the cure of diabetes.

Aim of the study

The present study was aimed to assess the antidiabetic and antioxidant effects of T. asiatica leaves in Streptozotocin (STZ) induced diabetic rats.

Materials and methods

The phytochemical screening, total phenolic content, HPLC analysis, acute toxicity study and oral glucose tolerance test were carried out. Glucose lowering effect of the hexane, ethyl acetate and methanol extracts of T. asiatica leaves was studied in STZ-induced diabetic rats. The antidiabetic and antioxidant activities were studied for the ethyl acetate extract. The effects of extracts on blood glucose, body weight, plasma insulin, total protein, liver glycogen, plasma enzymes (SGOT, SGPT and ALP) and activities of SOD, CAT and GPx were analyzed.

Results

T. asiatica leaves ethyl acetate extract (TALEe) showed highly significant blood glucose lowering effect. Phytochemical evaluation of TALEe showed the presence of alkaloids, terpenoids, cumarins, flavonoids and phenolic compounds. The total phenolic content of TALEe was 126 mg of gallic acid equivalents/g extract. HPLC analysis revealed the presence of flindersine and ulopterol. Acute toxicity study of TALEe revealed no death or toxicity. The oral glucose tolerance test showed lowered area under curve (AUC_glucose) values in TALEe treated rats. After treatment with TALEe (250 and 500 mg/kg) for 28 days there was a significant decrease in blood glucose, plasma enzymes (SGOT, SGPT and ALP) and significant increase in body weight, total protein, serum insulin and liver glycogen levels in treated diabetic rats. The activities of antioxidant enzymes SOD, CAT and GPx were reversed to near normal in treated diabetic rats. Histopathology of pancreas in TALEe treated groups showed regeneration of β-cells.

Conclusion

The results of the experiments showed that TALEe exerted significant antidiabetic and antioxidant effects in STZ-induced diabetic rats justifying its traditional use.     

Rheum australe D. Don: a review of its botany, ethnobotany, phytochemistry and pharmacology

Ethnopharmacological relevance

Rheum australe D. Don (Polygonaceae) has been commonly used in traditional medicine for a wide range of ailments related to the circulatory, digestive, endocrine, respiratory and skeletal systems as well as to infectious diseases.

Aim of the review

To provide the up-to-date information that is available on the botany, traditional uses, phytochemistry, pharmacology and toxicology of Rheum australe. Additionally, to highlight the possible uses of this species to treat different diseases and to provide a basis for future research.

Materials and methods

The present review covers the literature available from 1980 to 2011. The information was collected from scientific journals, books, theses and reports via a library and electronic search (Google Scholar, Web of Science and ScienceDirect).

Results

Ethnomedical uses of Rheum australe have been recorded from China, India, Nepal and Pakistan for 57 different types of ailments. The phytochemical studies have shown the presence of many secondary metabolites belonging to anthraquinones, stilbenes, anthrones, oxantrone ethers and esters, chromones, flavonoids, carbohydrate, lignans, phenols and sterols. Crude extracts and isolated compounds from Rheum australe show a wide spectrum of pharmacological activities, such as antidiabetic, anti-inflammatory, antifungal, antimicrobial, antioxidant, anticancer, hepatoprotective and immune-enhancing activities, as well as a usefulness for improving renal function.

Conclusion

Rheum australe has been widely used source of medicine for years without any adverse effects. Many studies have provided evidence for various traditional uses. However, there is a need for additional studies of the isolated compounds to validate the traditional uses in human models. The present review on the botany, traditional uses, phytochemistry and toxicity has provided preliminary information for further studies and commercial exploitations of the plant.