Role of Nitric Oxide and Nitric Oxide Synthases in Ischemia-reperfusion Injury in Rat Organotypic Hippocampus Slice

To investigate the effects of ischemia-reperfusion on the levels of nitric oxide and nitric oxide synthasc isoforms （nNOS and iNOS）, rat organotypic hippocampus slice were cultured in vitro and subjected to ischemia by oxygen glucose deprivation （OGD） for 30 min and then placed in the normal culture condition. The ischemia-reperfusion produced a time-dependent increase in nitrite levels in the culture medium. Reverse transcriptional-polymerase chain reaction showed augmented levels of mRNA for both nNOS and iNOS when compared with control at 12 h and remained increase at 36 h after OGD （P〈0.05）. The protein levels of both nitric oxide synthase isoforms increased significantly as determined by Western Blot. OGD also caused neurotoxicity in this model as revealed by the elevated lactate dehydrogenase （LDH） efflux into the incubation solution. The resuits suggest that organotypic hippocampus slice is a useful model in studying ischemia-reperfusion brain injury. NO and NOS may play a critical role in the ischemia-reperfusion brain damage in vitro.

Ex Vivo Characterization of the Action of Sideritis Extract Using Electrical Activity in the Rat Hippocampus Slice Preparation

A hydroethanolic extract (20% V/V) from Herba Sideritis scardica has been recognized to positively influence cognition. The present investigation aimed at the question if this extract would be able to modify intra-hippocampal communication after oral administration of 100 mg/kg daily for one week. The glutamatergic synapse between Schaffer Collaterals and pyramidal cells can be tested by electric stimulation using single pulses or theta burst stimulation. The resulting population spike is modulated by compounds acting at the central nervous system or other preparations directly or as ex vivo approach. In this case the effect of the special extract was tested in vitro the next day after repetitive in vitro administration. Conventional recording technique in the in vitro hippocampus slice revealed an increase of the population spike in the presence of single stimuli and theta burst stimuli resulting in increased long-term potentiation. This effect was tried to modulate by several glutamate receptor antagonists, among them compounds targeting at the ionic NMDA receptor (CGS19755), AMPA receptor (NBQX), Kainate receptor (UBP301) and targeting at three metabotropic glutamate receptors (mGluR I (YM298198), mGluRII ((RS)-APICA)) and mGluRIII (MSOP). Only NBQX was able to prevent the action of the Sideritis scardica extract. Since the AMPA receptor has been related to cognition in several reports in the literature, it is concluded from this result that the positive action of Sideritis scardica extract on brain function involves a modulation of AMPA receptor dependent neurotransmission.

Opposite Neurophysiological Findings Induced by Sideritis scardica and Sideritis euboa Extract in the Rat

Psychophysiological effects of Sideritis herba extracts depend on biologically active ingredients, which might be different for several botanical types of this plant. The present investigation aimed at the characterization of extracts from Sideritis scardica and Sideritis euboa in vivo and in vitro. Construction of electropharmacograms on the base of recording of electrical field potentials from four different brain regions was used to compare the possible pharmacological effects to a database of reference drugs with known clinical indications. Whereas Sideritis scardica produced decreases of spectral power in line with stimulatory frequency patterns as observed in the presence of Ginkgo biloba extract, administration of Sideritis euboa produced opposite effects. Electrical stimulation of the Schaffer Collaterals was used to elicit a pyramidal cell response called population spike in vitro. The amplitude of this spike was determined in the presence of single as well as theta burst stimuli. Direct exposure of brain matter to Sideritis scardica extract led to concentration dependent increases of the population spike amplitude under both stimulation patterns in the range from 12.5 to 100 mg/L. On the opposite, extract from Sideritis euboa did not change the electric response up to 50 mg/L. Higher concentrations of this extract attenuated the signal amplitude. A 1:1 blend of both gave intermediate results. The in vitro results are in line with the in vivo EEG recordings, where both extracts induced opposite changes of the electric power with respect to electric frequency patterns. The results from both models suggest a stimulatory and/or memory-enhancing action for the extract from Sideritis scardica but not for Sideritis euboa extract, where a more tranquillizing effect like that observed in the presence of Humulus cone extract may be expected.

Zynamite^(■) (Mangifera indica Leaf Extract)and Caffeine Act in a Synergistic Manner on Electrophysiological Parameters of Rat Central Nervous System

Zynamite®, a special extract from Mangifera indica, exerted stimulatory properties on the central nervous system during a pilot study. The question arose if Zynamite®?would have a similar action on the central nervous system as caffeine. Two well established animal models were used: a) quantitation of spectral power of field potentials in the freely moving rat and b) induction of long term potentiation (LTP) in the hippocampus slice preparation ex vivo after one week of daily administration. In the presence of 25 mg/kg of Zynamite®, predominantly alpha2 and beta1 spectral frequencies were attenuated in all brain areas during the first hour after administration. Exactly this pattern of frequency changes had been observed in earlier studies with i.p. administration of caffeine. Discriminant analysis confirmed this similarity by projection of Zynamite®?and 0.5 mg/kg caffeine into close neighborhood and showing identical colours, which points to a similar mechanism of action in this analysis. In addition, when Zynamite®?was combined with very low doses of caffeine synergistic effects were observed. Since alpha2 waves are under the control of dopamine, activation of this neurotransmitter system might be responsible for the stimulating property of Zynamite®. These results are corroborated by the results from the ex vivo study using the hippocampus slice in vitro to follow changes in excitability in the presence of 0.5 mg/kg of caffeine, 25 mg/kg of Zynamite®?or their combination in comparison to Placebo after daily administration for one week. Both caffeine and Zynamite®?increased LTP. LTP relates to space and time dependent memory. From these studies it is evident that both caffeine and Zynamite®?act in similar ways on brain electrical activity, and have potential to improve cognitive function. Bioactive compounds of Zynamite®?clearly pass the blood brain barrier to act on the central nervous system. Due to the demonstrated similarity of action, Zynamite®?has potential as a CNS-activating nutraceutical that could be used to replace caffeine.

Deconstructing brain-derived neurotrophic factor actions in adult brain circuits to bridge an existing informational gap in neuro-cell biology

Brain-derived neurotrophic factor（BDNF） plays an important role in neurodevelopment,synaptic plasticity,learning and memory,and in preventing neurodegeneration.Despite decades of investigations into downstream signaling cascades and changes in cellular processes,the mechanisms of how BDNF reshapes circuits in vivo remain unclear.This informational gap partly arises from the fact that the bulk of studies into the molecular actions of BDNF have been performed in dissociated neuronal cultures,while the majority of studies on synaptic plasticity,learning and memory were performed in acute brain slices or in vivo.A recent study by Bowling-Bhattacharya et al.,measured the proteomic changes in acute adult hippocampal slices following treatment and reported changes in proteins of neuronal and non-neuronal origin that may in concert modulate synaptic release and secretion in the slice.In this paper,we place these findings into the context of existing literature and discuss how they impact our understanding of how BDNF can reshape the brain.

EFFECTS OF GLUTAMATE ON SODIUM CHANNEL IN ACUTELY DISSOCIATED HIPPOCAMPAL CA1 PYRAMIDAL NEURONS OF RATS

Objective To observe the effects of glutamate on sodium channel in acutely dissociated hippocampal CA1 pyramidal neurons of rats.Methods Voltage-dependent sodium currents (INa) in acutely dissociated hippocampal CA1 pyramidal neurons of neonate rats were recorded by whole-cell patchclamp of the brain slice technique when a series of doses of glutamate (100-1000μmol/L) were applied.Results Different concentrations of glutamate could inhibit INa,and higher concentration of glutamate affected greater inhibition.In same concentration on INa at different times,longer time glutamate affected greater inhibition.And glutamate could significantly shift activation curve of INa to the right and make inactivation curve of INa negative drift.Conclusion Glutamate can inhibit voltage-dependent sodium channel.Its blockage on INa has voltage-dependent,time-dependent,and dose-dependent characteristics.