Antinociceptive effect of PnTx4(5-5), a peptide from Phoneutria nigriventer spider venom, in rat models and the involvement of glutamatergic system

The venom of Phoneutria nigriventer spider is a source of numerous bioactive substances, including some toxins active in insects. An example is PnTx4(5-5) that shows a high insecticidal activity and no apparent toxicity to mice, although it inhibited NMDA-evoked currents in rat hippocampal neurons. In this work the analgesic activity of PnTx4(5-5) (renamed Γ-ctenitoxin-Pn1a) was investigated. Methods: The antinociceptive activity was evaluated using the paw pressure test in rats, after hyperalgesia induction with intraplantar injection of carrageenan or prostaglandin E2 (PGE2). Results: PnTx4(5-5), subcutaneously injected, was able to reduce the hyperalgesia induced by PGE2 in rat paw, demonstrating a systemic effect. PnTx4(5-5) administered in the plantar surface of the paw caused a peripheral and dose-dependent antinociceptive effect on hyperalgesia induced by carrageenan or PGE2. The hyperalgesic effect observed in these two pain models was completely reversed with 5 µg of PnTx4(5-5). Intraplantar administration of L-glutamate induced hyperalgesic effect that was significantly reverted by 5 μg of PnTx4(5-5) injection in rat paw. Conclusion: The antinociceptive effect for PnTx4(5-5) was demonstrated against different rat pain models, i.e. induced by PGE2, carrageenan or glutamate. We suggest that the antinociceptive effect of PnTx4(5-5) may be related to an inhibitory activity on the glutamatergic system.(AU)

Spinal CCL2 Promotes Central Sensitization, Long-Term Potentiation, and Inflammatory Pain via CCR2: Further Insights into Molecular, Synaptic, and Cellular Mechanisms / 神经科学通报·英文版

Mounting evidence supports an important role of chemokines, produced by spinal cord astrocytes, in promoting central sensitization and chronic pain. In particular, CCL2 (C-C motif chemokine ligand 2) has been shown to enhance N-methyl-D-aspartate (NMDA)-induced currents in spinal outer lamina II (IIo) neurons. However, the exact molecular, synaptic, and cellular mechanisms by which CCL2 modulates central sensitization are still unclear. We found that spinal injection of the CCR2 antagonist RS504393 attenuated CCL2- and inflammation-induced hyperalgesia. Single-cell RT-PCR revealed CCR2 expression in excitatory vesicular glutamate transporter subtype 2-positive (VGLUT2) neurons. CCL2 increased NMDA-induced currents in CCR2/VGLUT2 neurons in lamina IIo; it also enhanced the synaptic NMDA currents evoked by dorsal root stimulation; and furthermore, it increased the total and synaptic NMDA currents in somatostatin-expressing excitatory neurons. Finally, intrathecal RS504393 reversed the long-term potentiation evoked in the spinal cord by C-fiber stimulation. Our findings suggest that CCL2 directly modulates synaptic plasticity in CCR2-expressing excitatory neurons in spinal lamina IIo, and this underlies the generation of central sensitization in pathological pain.

Rat Cerebrospinal Fluid Treatment Method through Cisterna Cerebellomedullaris Injection / 神经科学通报·英文版

Drugs that lack the ability to cross the blood-brain barrier (BBB) need to be placed directly into the central nervous system. Our laboratory studies the involvement of the glutamatergic system in the aggressiveness of glioma, and some ligands of glutamate receptors cannot permeate the BBB. Here, glioma-implanted rats were treated by a technique that delivers ligands directly into the cerebrospinal fluid by puncture into the cisterna cerebellomedullaris. Rats were anesthetized and fixed in a rodent stereotactic device. The head was gently tilted downwards at an angle that allowed exposure of the cisterna. Injection into the cisterna was done freehand using a gingival needle coupled to a microsyringe. The efficiency of intracisternal injection was demonstrated using a methylene blue solution. This type of injection is adaptable for any rodent model using small volumes of a variety of other drugs, and is an interesting method for neuroscience studies.

A 10-Week Memantine Treatment in Bipolar Depression: A Case Report. Focus on Depressive Symptomatology, Cognitive Parameters and Quality of Life

Memantine and other glutamatergic agents have been currently investigated in some off-label indications due to glutamatergic involvement in several psychoneurological disorders. We assumed that memantine similarly to ketamine may positively influence mood, moreover having a potential to improve cognition and general quality of life. We report a case of a 49-year-old male hospitalized during a manic and a subsequent moderate depressive episode. After an ineffective use of lithium, olanzapine and antidepressive treatment with mianserin, memantine was added up to 20 mg per day for 10 weeks. The mental state was assessed using the Hamilton Depression Rating Scale, the Young Mania Rating Scale, the Hamilton Anxiety Scale, the Clinical Global Inventory, the World Health Organization Quality of Life Scale and psychological tests. After 10 weeks the patient achieved a partial symptomatic improvement in mood, anxiety and quality of sleep, but his activity remained insufficient. We also observed an improvement in the parameters of cognitive functioning and quality of life. There was neither significant mood variations during the memantine use nor mood changes after its termination. No significant side effects were noted during the memantine treatment. We conclude that using memantine in bipolar depression may improve mood, cognitive functioning and quality of life.

Disfunción del transportador de glutamato / Glutamate Transporter disfunction

El glutamato, principal neurotransmisor excitatorio, está involucrado en mecanismos de plasticidad sináptica, memoria y muerte neuronal o glial, y el adecuado mantenimiento de sus niveles extracelulares es esencial para evitar la excitotoxicidad. En los últimos años se han producido muchos avances en el estudio de los transportadores de glutamato (VGLUTs y EAATs) encargados de su re-captura en las sinapsis. Haremos una revisión bibliográfica de sus propiedades, alteraciones producidas por su disfunción y posibles alternativas de neuroprotección. Así mismo revisaremos otro aspecto importante, la liberación de glutamato por los astrocitos bajo diversas situaciones patológicas, descubrimiento este de las últimas décadas de investigación sobre la glia

Glutamate, the major excitatory neurotransmitter, is involved in synaptic plasticity, memory and neuronal or glial death, and it is essential to proper maintenance of extracellular levels to prevent excitotoxicity. In recent years there have been many advances in the study of glutamate transporters (EAATs and VGLUTs) responsable for its re-capture at synapses. We will do a bibliographic review of their properties, changes caused by their dysfunction and possible alternatives for neuroprotection. We will also review antoher important aspect, the release of glutamate by astrocytes under different pathological conditions, discovered on the last decades by the research on glia

Modulation of basal glutamatergic transmission by nicotinic acetylcholine receptors in rat hippocampal slices

Nicotinic acetylcholine receptors [nAChRs] regulate epileptiform activity and produce a sustained proepileptogenic action within the hippocampal slices. In the present study, we investigated the effect of nAChRs on evoked glutamatergic synaptic transmission in area CA3 and CA1 of rat hippocampal slices to identify possible excitatory circuits through which activation of nAChRs produce their pro-epileptogenic effects. Hippocampal slices [400 micro m thick] prepared in vitro from male Wistar rats [3-5 weeks], using standard procedures. Following 1 hr equilibration in artificial cerebrospinal fluid [ACSF], slices transferred to an interface recording chamber. Stimulatory electrodes placed within the hilus or Schaffer-collateral pathways and extracellular field recordings made in the stratum radiatum of the CA1 and CA3 regions to investigate evoked synaptic responses. Bath application of the selective nAChR agonist dimethylphenyl-piperanzinium [DMPP, 30 micro M] resulted in a sustained and reversible enhancement of glutamate afferent evoked fEPSP amplitude by 15.7 +/- 5.1% [mean +/- SEM; n = 8 of 12] in the CA3 region of the hippocampus but not in the CA1 [-5.25 +/- 8.3%, mean +/- SEM; n = 5]. Activation of nAChRs may produce pro-epileptogenic actions in part through regulating glutamatergic circuits. Difference in nAChR regulation is also evident between different regions of hippocampus

Doxorubicin and etoposide induce somatic recombination in diploid cells of Aspergillus nidulans

Doxorubicin and etoposide are intercalating agents that inhibit the action of the enzyme topoisomerase II. Both drugs present therapeutic activity in numerous human neoplasms In the present work the recombinagenic potential of these drugs was evaluated by ascomycete Aspergillus nidulans. Their effects on the asexual cycle of A. nidulans was also appraised. Two heterozygous diploid strains of A. nidulans, a wild (uvsH+//uvsH+) and a defective to the DNA repair (uvsH//uvsH) were used. The drugs' recombinagenic potential was evaluated by their capacity to induce homozygosis of recessive genes from heterozygous cells. Both drugs have a recombinagenic effect on diploid cells of A. nidulans. Doxorubicin and etoposide are potentially capable to induce secondary malignancies, mediated by the mitotic crossing-over in eukaryotic cells

Effects of entorhinal cortex lesions on memory in different tasks

Lesions of the entorhinal cortex produce retrograde memory impairment in both animals and humans. Here we report the effects of bilateral entorhinal cortex lesions caused by the stereotaxic infusion of N-methyl-D-aspartate (NMDA) in rats at two different moments, before or after the training session, on memory of different tasks: two-way shuttle avoidance, inhibitory avoidance and habituation to an open field. Pre-or post-training entorhinal cortex lesions caused an impairment of performance in the shuttle avoidance task, which agrees with the previously described role of this area in the processing of memories acquired in sucessive sessions. In the inhibitory avoidance task, only the post-training lesions had an effect (amnesia). No effect was observed on the open field task. The findings suggest that the role of the entorhinal cortex in memory processing is task-dependent, perhaps related to the complexity of each task.

Control of the phosphorylation of the astrocyte marker glial fibrillary acidic protein (GFP) in the immature rat hippocampus by glutamate and calcium ions: possible key factor in astrocytic plasticity

The present review describes recent research on the regulation by glutamate and Ca2+ of the phosphorylation state of the intermediate filament protein of the astrocytic cytoskeleton, glial fibrillary acidic protein (GFAP), in immature hippocampal slices. The results of this research are discussed against a background of modern knowledge of the functional importance of astrocytes in the brain and of the structure and dynamic properties of intermediate filament proteins. Astrocytes are now recognized as partners with neurons in many aspects of brain function with important roles in neural plasticity. Site-specific phosphorylation of intermediate filament proteins, including GFAP, has been shown to regulate the dynamic equilibrium between the polymerized and depolymerized state of the filaments and to play a fundamental role in mitosis. Glutamate was found to increase the phosphorylation state of GFAP in hippocampal slices from rats in the post-natal age range of 12-16 days in a reaction that was dependent on external Ca2+. The lack of external Ca2+ in the absence of glutamate also increased GFAP phosphorylation to the same extent. These effects of glutamate and Ca2+ were absent in adult hippocampal slices, where the phosphorylation of GFAP was completely Ca2+ -dependent. Studies using specific agonists of glutamate receptors showed that the glutamate response was mediated by a G protein-linked group II metabotropic glutamate receptor (mGluR). Since group II mGluRs do not act by liberating Ca2+ from internal stores, it is proposed that activation of thereceptor by glutamate inhibits Ca2+ entry into the astrocytes andconsequently down-regulates a Ca2+-dependent dephosphorylationcascade regulating the phosphorylation state of GFAP. The functional significance of these results may be related to the narrow developmental window when the glutamate response is present. In the rat brain this window corresponds to the period of massive synaptogenesis during which astrocytes are known to proliferate. Possibly, glutamate liberated from developing synapses during this period may signal an increase in the phosphorylation state of GFAP and a consequent increase in the number of mitotic astrocytes.