Hippocampal synaptic dysfunction in the SOD1G93A mouse model of Amyotrophic Lateral Sclerosis: Reversal by adenosine A2AR blockade.

Amyotrophic Lateral Sclerosis (ALS) mostly affects motor neurons, but non-motor neural and cognitive alterations have been reported in ALS mouse models and patients. Here, we evaluated if time-dependent biphasic changes in synaptic transmission and plasticity occur in hippocampal synapses of ALS SOD1G93A mice. Recordings were performed in hippocampal slices of SOD1G93A and age-matched WT mice, in the pre-symptomatic and symptomatic stages. We found an enhancement of pre-synaptic function and increased adenosine A2A receptor levels in the hippocampus of pre-symptomatic mice. In contrast, in symptomatic mice, there was an impairment of long-term potentiation (LTP) and a decrease in NMDA receptor-mediated synaptic currents, with A2AR levels also being increased. Chronic treatment with the A2AR antagonist KW-6002, rescued LTP and A2AR values. Altogether, these findings suggest an increase in synaptic function during the pre-symptomatic stage, followed by a decrease in synaptic plasticity in the symptomatic stage, which involves over-activation of A2AR from early disease stages.

Disposable electrochemical detection of breast cancer tumour marker CA 15-3 using poly(Toluidine Blue) as imprinted polymer receptor.

In this work, electrically-conducting poly(Toludine Blue) was employed for the first time as synthetic receptor film, prepared by Molecular Imprinting strategies and using electrochemical methods, for the specific screening of breast cancer biomarker Carbohydrate Antigen 15-3 (CA 15-3). The protein imprinted poly(Toluidine Blue) film was grown in a pre-formed Toluidine Blue (TB) tailed SAM at the AuSPE surface, which greatly enhanced the stability against degradation of the Molecular Imprinted Polymer (MIP) film at the electrode surface. The MIP receptor film recognition ability towards the protein was investigated by fitting data to Freundlich isotherm. The binding affinity (KF) obtained for the MIP system was significantly higher (~ 12-fold) to that obtained for the NIP system, demonstrating the success of the approach in creating imprinted materials that specifically respond to CA 15-3 protein. The incubation of the MIP modified electrode with increasing concentration of protein (from 0.10 U mL-1 to 1000 U mL-1) resulted in a decrease of the ferro/ferricyanide redox current. The device displayed linear response from 0.10 U mL-1 to 100 U mL-1 and LODs below 0.10 U mL-1 were obtained from calibration curves built in neutral buffer and diluted artificial serum, using DPV technique, enabling the detection of the protein biomarker at clinically relevant levels. The developed MIP biosensor was applied to the determination of CA 15-3 in spiked serum samples with satisfactory results. The developed device provides a new strategy for sensitive, rapid, simple and cost-effective screening of CA 15-3 biomarker. Importantly, the overall approach seems suitable for point-of-care (PoC) use in clinical context.

Mismatch novelty exploration training enhances hippocampal synaptic plasticity: A tool for cognitive stimulation?

Memory formation relies on experience-dependent changes in synaptic strength such as long-term potentiation (LTP) or long-term depression (LTD) of synaptic activity, that in turn depend on previous learning experiences through metaplasticity. Novelty detection is a particularly important cognitive stimulus in this respect, and mismatch novelty has been associated with the activation of the hippocampal CA1 area in human studies. A single exposure to a new location of known objects in a familiar environment, a behavioural mismatch novelty paradigm, is known to favour the expression of LTD in hippocampal CA3 to CA1 synaptic transmission in vivo, through short-term metaplasticity. Aiming to shape hippocampal responsiveness to synaptic plasticity phenomena we developed a training program based on exploration of a known environment containing familiar objects, everyday presented in a new location. Repeated exposure to this new location of objects for two weeks caused a mild long-lasting decrease in synaptic efficacy. Furthermore, it enhanced both LTP evoked by theta-burst stimulation and depotentiation evoked by low-frequency stimulation of CA3 to CA1hippocampal synaptic transmission in juvenile rats. This suggests that training programs using these behavioural tasks involving mismatch novelty can be used to reshape brain circuits and promote cognitive recovery in pathologies where LTP/LTD imbalance occurs, such as epilepsy, aging or Down's syndrome, an approach that requires further investigation at the behavioural level.

Electrochemical detection of cardiac biomarker myoglobin using polyphenol as imprinted polymer receptor.

An electrochemical biosensor was developed by merging the features of Molecular Imprinting technique and Screen-Printed Electrode (SPE) for the simple and fast screening of cardiac biomarker myoglobin (Myo) in point-of-care (POC). The MIP artificial receptor for Myo was prepared by electrooxidative polymerization of phenol (Ph) on a AuSPE in the presence of Myo as template molecule. The choice of the most effective protein extraction procedure from the various extraction methods tested (mildly acidic/basic solutions, pure/mixed organic solvents, solutions containing surfactants and enzymatic digestion methods), and the optimization of the thickness of the polymer film was carefully undertaken in order to improve binding characteristics of Myo to the imprinted polymer receptor and increase the sensitivity of the MIP biosensor. The film thickness was optimized by adjusting scan rate and the number of cycles during cyclic voltammetric electropolymerization of Ph. The thickness of the polyphenol nanocoating of only few nanometres (∼4.4 nm), and similar to the protein diameter, brought in significant improvements in terms of sensor sensitivity. The binding affinity of MIP receptor film was estimated by fitting the experimental data to Freundlich isotherm and a ∼8 fold increase in the binding affinity of Myo to the imprinted polymer (KF = 0.119 ± 0.002 ng-1 mL) when compared to the non-imprinted polymer (KF = 0.015 ± 0.002 ng-1 mL) which demonstrated excellent (re)binding affinity for the imprinted protein. The incubation of the Myo MIP receptor modified electrode with increasing concentration of protein (from 0.001 ng mL-1 to 100 µg mL-1) resulted in a decrease of the ferro/ferricyanide redox current. LODs of 2.1 and 14 pg mL-1 were obtained from calibration curves built in neutral buffer and diluted artificial serum, respectively, using SWV technique, enabling the detection of the protein biomarker at clinically relevant levels. The prepared MIP biosensor was applied to the determination of Myo spiked serum samples with satisfactory results.

Toxicidade do pericarpo da Jatropha curcas em ovinos / Jatropha curcas pericarp toxicity in sheep

O pinhão manso (Jatropha curcas) é uma planta cultivada para a produção de biocombustível. O pericarpo é um coproduto com potencial para alimentação animal, e a presença de componentes tóxicos, principalmente ésteres de forbol, pode limitar sua utilização. Assim, objetivou-se avaliar a toxicidade do pericarpo. Vinte ovinos foram distribuídos em quatro grupos - um grupo-controle, que não recebeu a planta, e três experimentais, que receberam o pericarpo nas concentrações de 15% (G15), 30% (G30) e 45% (G45), durante 23 dias. Após o 10º dia, a ingestão do pericarpo promoveu redução do consumo de alimento, diarreia, desidratação e caquexia. Todos os grupos tratados apresentaram redução na concentração de fosfatase alcalina. Animais do G30 apresentaram redução na concentração de ureia e proteínas totais e elevação de potássio e sódio. No G45, houve aumento de aspartato aminotransferase, albumina, creatinina bilirrubina indireta e total. A avaliação anatomo-histopatológica revelou ascite, hidropericárdio, congestão no trato gastrintestinal e nos pulmões, edema pulmonar, aderências à parede torácica, degeneração hepática centrolobular e das células tubulares renais, pneumonia linfo-histiocitica e enterite linfoplasmocitária e histiocítica. À análise fitoquímica, constatou-se 0,3845mg de ésteres de forbol/g de pericarpo. Conclui-se que o pericarpo de J. curcas é tóxico, não sendo recomendado para alimentação de ovinos.

Physic nut (Jatropha curcas) is a plant cultivated for biofuel production. Pericarp is a potential livestock food source by-product. However, its use may be limited due to the presence of toxic compounds, mainly phorbol esters. Thus, this study aimed to evaluate pericarp toxicity. Twenty sheep were divided in four groups, one control group which did not receive the plant and three experimental groups which received pericarp in 15% (G15), 30% (G30) and 45% (G45) concentrations for 23 days. After 10 days of treatment, pericarp ingestion produced food intake decrease, diarrhea, dehydration and loss of body condition. All treated groups showed decrease in alkaline phosphatase activity. G30 animals presented reductions in urea and total protein concentrations, and increase in potassium and sodium levels. G45 animals showed increase in serum aspartate aminotransferase activity and in albumin, creatinin, total and indirect bilirubin levels. Anatomohistopathologic findings included ascites, hydropericardium, congestion of the gastintestinal tract and lungs, pulmonary edema and adhesions in the thoracic cavity, renal tubular cells and centrilobular cytoplasmic vacuolation and lymphohistiocytic pneumonia and lymphoplasmacytic and histiocytic enteritis. On the physiochemical analysis 0.3845mg of phorbol esters/g of pericarp were detected. It is concluded that J. curcas pericarp is toxic and is not recommended for sheep feeding.

Modulation and metamodulation of synapses by adenosine.

The presence of adenosine in all nervous system cells (neurones and glia) together with its intensive release following insults makes adenosine as a sort of 'regulator' of synaptic communication, leading to the homeostatic coordination of brain function. Besides the direct actions of adenosine on the neurosecretory mechanisms, to tune neurotransmitter release, adenosine receptors interact with other receptors as well as with transporters as part of its attempt to fine-tune synaptic transmission. This review will focus on examples of the different ways adenosine can use to modulate or metamodulate synapses, in other words, to trigger or brake the action of some neurotransmitters and neuromodulators, to cross-talk with other G protein-coupled receptors, with ionotropic receptors and with receptor kinases as well as with transporters. Most of these interactions occur through A2A receptors, which in spite of their low density in some brain areas, such as the hippocampus, may function as amplifiers of the signalling of other mediators at synapses.

Intraoperative bleeding during vitrectomy for diabetic tractional retinal detachment with versus without preoperative intravitreal bevacizumab (IBeTra study).

AIMS: To compare the amount of intraoperative intraocular bleeding in patients with diabetes with macula-involving tractional retinal detachment (TRD) undergoing pars plana vitrectomy (PPV) with and without preoperative intravitreal bevacizumab (IVB) injection. METHODS: An institutional study was carried out with consecutive patients with diabetic retinopathy and macula-involving TRD of recent (3 months) onset who were randomly assigned to PPV only (PPV group) or PPV combined with one IVB (1.5 mg/0.06 ml) injection 2 weeks prior to surgery (bevacizumab (BEV)/PPV group). All patients underwent 23-gauge PPV 3 weeks after baseline. The main outcome measure was erythrocyte count in the fluid retrieved from the vitrectomy cassette using a Neubauer counting chamber. RESULTS: The study included 20 patients. The mean erythrocyte count was 14,865x10(3) (SD 19,332x10(3); median 4,500x10(3)) cells in the BEV/PPV group, and 176,240x10(3) (SD 108,375x10(3); median 166,600x10(3)) cells in the PPV group. The mean erythrocyte count was significantly lower in the BEV/PPV group than in the PPV group (p<0.0001). No major adverse events were identified. CONCLUSION: Preoperative IVB injection was associated with reduced intraocular bleeding during 23-gauge PPV for diabetic macula-involving TRD. Further studies are needed to confirm our preliminary findings. TRIAL REGISTRATION NUMBER: NCT00690768.

Tuning and fine-tuning of synapses with adenosine.

The 'omnipresence' of adenosine in all nervous system cells (neurons and glia) together with the intensive release of adenosine following insults, makes adenosine as a sort of 'maestro' of synapses leading to the homeostatic coordination of brain function. Besides direct actions of adenosine on the neurosecretory mechanisms, where adenosine operates to tune neurotransmitter release, receptor-receptor interactions as well as interplays between adenosine receptors and transporters occur as part of the adenosine's attempt to fine tuning synaptic transmission. This review will focus on the different ways adenosine can use to trigger or brake the action of several neurotransmitters and neuromodulators. Adenosine receptors cross talk with other G protein coupled receptors (GPCRs), with ionotropic receptors and with receptor kinases. Most of these interactions occur through A2A receptors, which in spite their low density in some brain areas, such as the hippocampus, may function as metamodulators. Tonic adenosine A2A receptor activity is a required step to allow synaptic actions of neurotrophic factors, namely upon synaptic transmission at both pre- and post-synaptic level as well as upon synaptic plasticity and neuronal survival. The implications of these interactions in normal brain functioning and in neurologic and psychiatric dysfunction will be discussed.

The Brazilian Peritoneal Dialysis Multicenter Study (BRAZPD) : characterization of the cohort.

The Brazilian Peritoneal Dialysis Multicenter Study (BRAZPD) was launched in December 2004 aiming to collect data monthly and continuously from a representative cohort, allowing for a continuous snapshot of the peritoneal dialysis (PD) reality in the country. This is an observational study of PD patients comprising follow-up from December 2004 to February 2007 (mean follow-up of 13.6 months-ranging from 1 to 26 months) in 114 Brazilian centers. All centers report data through a central web-based database. After an initial baseline retrospective data collection, all patients are followed prospectively every month until they drop out from the PD program. Total number of patients recruited until February 2007 was 3226 (2094 incident patients). Mean age was 54+/-19 years (37% above 65 years old), with 55% females and 64% Caucasians. The more frequent causes of renal failure were diabetic nephropathy (34%), renal vascular disease associated with hypertension (26%), and glomerulopathies (13%). The most common comorbidities were hypertension (76%), diabetes (36%), and ischemic heart disease (23%). Automated PD (APD) was the modality utilized in 53%. The estimated overall peritonitis rate was 1 episode per 30 patient-months (most frequently due to Staphylococcus aureus). The total dropout rate was 33%, mainly due to deaths, whereas 20% of dropouts were due to renal transplant. The gross mortality was 17.6% and the main causes of mortality were cardiovascular diseases (40%) and infections (15%). The initial results of this first Brazilian PD registry provide a unique opportunity to develop future clinical studies addressing specific PD questions in the Brazilian reality and context.

Enhancement of long-term potentiation by brain-derived neurotrophic factor requires adenosine A2A receptor activation by endogenous adenosine.

The excitatory action of brain-derived neurotrophic factor (BDNF) on synaptic transmission is triggered by adenosine A2A receptor activation. Since high-frequency neuronal firing, such as that inducing long-term potentiation (LTP), favours both A2A receptor activation and BDNF effects on transmission, we now evaluated the influence of adenosine on the facilitatory action of BDNF upon CA1 hippocampal LTP. theta-Burst stimulation of the pyramidal inputs induced a significant and persistent increase in field EPSP slopes, and this potentiation was augmented in the presence of BDNF (20 ng/ml), an action prevented by the inhibitor of Trk receptor autophosphorylation, K252a (200 nM). Removal of endogenous extracellular adenosine with adenosine deaminase (ADA, 1 U/ml), as well as the antagonism of adenosine A2A receptors with SCH58261 (100 nM), prevented the excitatory action of BDNF upon LTP. In an adenosine depleted background (with ADA), activation of adenosine A2A receptors (with 10nM CGS21680) restored the facilitatory effect of BDNF on LTP; this was fully prevented by the protein kinase A inhibitor, H-89 (1 microM) and mimicked by the adenylate cyclase activator, forskolin (10 microM). In similar experiments, activation of adenosine inhibitory A1 receptors (with 5 nM CPA) did not affect the facilitatory effect of BDNF. In conclusion, the facilitatory action of BDNF upon hippocampal LTP is critically dependent on the presence of extracellular adenosine and A2A receptor activation through a cAMP/PKA-dependent mechanism. Since extracellular adenosine accumulates upon high-frequency neuronal firing, the present results reveal a key process to allow the influence of BDNF upon synaptic plasticity.

Interleukin-6 upregulates neuronal adenosine A1 receptors: implications for neuromodulation and neuroprotection.

The immunological response in the brain is crucial to overcome neuropathological events. Some inflammatory mediators, such as the immunoregulatory cytokine interleukin-6 (IL-6) affect neuromodulation and may also play protective roles against various noxious conditions. However, the fundamental mechanisms underlying the long-term effects of IL-6 in the brain remain unclear. We now report that IL-6 increases the expression and function of the neuronal adenosine A1 receptor, with relevant consequences to synaptic transmission and neuroprotection. IL-6-induced amplification of A1 receptor function enhances the responses to readily released adenosine during hypoxia, enables neuronal rescue from glutamate-induced death, and protects animals from chemically induced convulsing seizures. Taken together, these results suggest that IL-6 minimizes the consequences of excitotoxic episodes on brain function through the enhancement of endogenous adenosinergic signaling.

Complex distribution of renal vessels

The retroperitoneal lumbar vessels should be immediately recognized during urological, vascular and radiologicalmedical procedures. Few studies have tried to define an exact pattern for the lumbar vasculature andmost of the anatomical descriptions suggest the presence of a regular pattern. Nevertheless, for the renal bloodvessels, despite the described regular pattern, several anatomical variations have interested anatomists for morethan a century. Taking into account that there is a constant need for reviewing this anatomy due to the advancesin surgical and/or uroradiological procedures techniques, we describe a complex variation of the renalblood vessels found during the dissection routine in our laboratory. A male cadaver, aged 65 years, embalmedwith 10% formalin solution presented, on the left side, two renal arteries arising from the abdominal aorta,both of them entering the kidney on the hilar region. From the hilar region of the left kidney, there were alsotwo tributary renal veins, which join together 3.0 cm from the hilus, before draining into the inferior venacava. These two tributary veins were large in diameter, and made a loop around the two renal arteries and alsothe ureter. No anatomical variations were found on the right side. This is a complex anatomical variation of therenal vessels which might have functional implications once the venous loop described might be a compressionfactor for the renal arteries and for the ureter.

Tonic adenosine A1 and A2A receptor activation is required for the excitatory action of VIP on synaptic transmission in the CA1 area of the hippocampus.

Adenosine can regulate synaptic transmission through modulation of the action of other neurotransmitters. The influence of adenosine on VIP enhancement of synaptic transmission in hippocampal slices was investigated. Facilitation of fEPSP slope by 1 nM VIP (23.3+/-1.3%) was turned into an inhibition (-12.1+/-3.4%) when extracellular endogenous adenosine was removed using adenosine deaminase (ADA, 1U/ml). Blockade of adenosine A(1) receptors with 1,3-dipropyl-8-cyclopentylxanthine (DPCPX, 10 nM) or of A(2A) receptors with ZM241385 (20 nM) attenuated the effect of VIP. When both DPCPX and ZM241385 were present the effect of VIP was abolished. In the presence of ADA, selective A(1) receptor activation with N(6)-cyclopentyladenosine (CPA, 15 nM) or A(2A) receptor-activation with CGS21680 (10 nM) partially readmitted the excitatory effect of VIP on fEPSPs. In contrast, facilitation of PS amplitude by 1 nM VIP (19.1+/-1.2%) was attenuated in the presence of ADA or DPCPX but was not changed by ZM241385. CPA, in the presence of ADA, fully restored the effect of VIP on PS amplitude. In conclusion, VIP facilitation of synaptic transmission to hippocampal pyramidal cell dendrites is dependent on both A(1) and A(2A) receptor activation by endogenous adenosine. VIP effects on PS amplitude are only dependent on A(1) adenosine receptor activation. This differential sensitivity to adenosine modulation might be due to the different VIP circuits contributing to VIP effects on pyramidal cell dendrites and pyramidal cell bodies.

Hypoxia-induced desensitization and internalization of adenosine A1 receptors in the rat hippocampus.

Activation of A1 adenosine receptors is important for both the neuromodulatory and neuroprotective effects of adenosine. However, short periods of global ischemia decrease A1 adenosine receptor density in the brain and it is not known if a parallel loss of functional efficiency of A1 adenosine receptors occurs. We now tested if hypoxia leads to changes in the density and efficiency of A1 adenosine receptors to inhibit excitatory synaptic transmission in rat hippocampal slices. In control conditions, the adenosine analog 2-chloroadenosine, inhibited field excitatory post-synaptic potentials with an EC50 of 0.23 microM. After hypoxia (95% N2 and 5% CO2, for 60 min) and reoxygenation (30 min), the EC50 increased to 0.73 microM. This EC50 shift was prevented by the presence of the A1 adenosine receptor antagonist 8-phenyltheophyline, but not by the A(2A)R antagonist 7-(2-phenylethyl)-5-amino-2-(2-furyl)-pyrazolo-[4,3-e]-1,2,4-triazolo[1,5-c] pyrimidine, during the hypoxic period. This decreased efficiency of A1 adenosine receptors was not paralleled by a global change of A1 adenosine receptor density or affinity (as evaluated by the binding parameters obtained in nerve terminal membranes). However, the density of biotinylated A1 adenosine receptors at the plasma membrane of nerve terminals was reduced by 30% upon hypoxia/reoxygenation, in a manner prevented by the A1 adenosine receptor antagonist 1,3-dipropyl-8-cyclopentylxanthine and mimicked by prolonged (60 min) supra-maximal activation of A1 adenosine receptors with 2-chloroadenosine (10 microM). These results indicate that hypoxia leads to a rapid (<90 min) homologous desensitization of A1 adenosine receptor-mediated inhibition of synaptic transmission that is likely due to an internalization of A1 adenosine receptors in nerve terminals.

What can adenosine neuromodulation do for neuroprotection?

The possibility of repairing brain lesions is a crucial issue. Knowing how regeneration occurs allows novel concepts in the process of protecting the nervous system, in other words to induce and to develop neuroprotection. Brain insults cause irreversible tissue damage by at least three mechanisms: First, through consequences of mechanical disruption of neurons or their projections; secondly, through biochemical or metabolic changes that are initiated by the insult; and finally, through inflammatory reactions or gliotic changes. The cellular elements and the chemical neuro-mediators involved in brain injury act via interconnections between the cellular elements and their secretions; the immune system and the nervous system are highly regulated in normal physiology, which benefits the organism. When these cells suffer insults in the central nervous system (CNS), the connections between the systems are altered; these systems act together to strangulate the tissue, depriving it of the local control over microcirculation and necessary oxygen, rendering membrane potentials useless to modulate neuronal function. Surgical interventions during the stages of brain injury continue to progress as do biochemical and bioelectric therapeutics during the chronic and rehabilitation stages. There is some hope, too, for effective neuropharmacological intervention. The fact that chemical mediators are already part of normal physiology, whether during development or adulthood, means that their activity can be modified by specific agonists and antagonists to restore homeostasis or to promote the safe pathways that can lead to regeneration. This is the orientation of much of current basic and clinical research. During the past decade considerable experimental and clinical data have been accumulated regarding cellular and biochemical events associated with brain repair.

Eating seizures and emotional facial paresis: evidence suggesting the amygdala is a common anatomophysiological substratum.

The medial basotemporal lobes (hippocampus, amygdala, parahippocampal gyrus) are considered to be parts of the system responsible for nonvolitional facial movements. In patients with temporal lobe epilepsy, lower facial weakness during emotional expression has been found to occur almost exclusively contralateral to the temporal lobe with the epileptogenic focus. Repetitive and chronic stimulation of the amygdala during eating has also been postulated as a probable mechanism for eating seizures. The authors present the illustrative aspects of both facial asymmetry and eating seizures in a case of mesial temporal lobe epilepsy (MTLE). This report provides evidence that the amygdala may be the common anatomical basis for three different aspects of this patient: emotional facial paresis, eating seizures, and sleep paroxysmal microarousals.

Tratamento dos craniofaringiomas por via trans-esfenoidal: resultados e seguimento pós-operatórios / Trans-sphenoidal approach to craniopharyngiomas: postoperative and follow-up results

Introdução: O craniofaringioma é uma neoplasia benignade difde difícil tratamento mesmo com ampla variedade de procedimentosterapêuticos disponíveis. Este fato decorre dassuas características biológicas peculiares e de sua localizaçãohabitual. Material e métodos: Este é um estudo retrospectivo depacientes com diagnóstico de craniofaringioma operados pelavia trans-esfenoidal no Hospital das Clínicas da Faculdadede Medicina da Universidade de São Paulo. Trinta e quatropacientes, operados no período de 1981 a 2000, tiveram seusprontuários avaliados. Dados referentes à condição clínica,exames de tomografi a e ressonância magnética, bem como dadosendocrinológicos foram verifi cados antes e após o procedimentocirúrgico, referentes ao último retorno ambulatorial conhecido.Os dados obtidos foram submetidos à análise estatística. Resultados:A faixa etária foi de 4 a 45 anos; 55,88% dos pacienteseram do sexo feminino. A média do tempo de seguimento foi de5,7 anos (d.p.= 5,9 anos); 44% dos casos tinham exame de imageminicial mostrando compressão de vias ópticas pelo tumor.Fístula liquórica foi a complicação mais freqüente associadaao procedimento. Conclusão: Concluímos que a via trans-esfenoidalé um procedimento válido para este tipo de tumor. Osmelhores resultados foram para os tumores de volume menor. As seqüelas endócrinas são muito freqüentes no seguimentoem longo prazo.

Presynaptic kainate receptors modulating glutamatergic transmission in the rat hippocampus are inhibited by arachidonic acid.

Kainate receptors are ionotropic glutamate receptors located postsynaptically, mediating frequency-dependent transmission, and presynaptically, modulating transmitter release. In contrast to the excitatory postsynaptic kainate receptors, presynaptic kainate receptor can also be inhibitory and their effects may involve a metabotropic action. Arachidonic acid (AA) modulates most ionotropic receptors, in particular postsynaptic kainate receptor-mediated currents. To further explore differences between pre- and postsynaptic kainate receptors, we tested if presynaptic kainate receptors are affected by AA. Kainate (0.3-3 microM) and the kainate receptor agonist, domoate (60-300 nM), inhibited by 19-54% the field excitatory postsynaptic potential (fEPSP) slope in rat CA1 hippocampus, and increased by 12-32% paired-pulse facilitation (PPF). AA (10 microM) attenuated by 37-72% and by 62-66% the domoate (60-300 nM)-induced fEPSP inhibition and paired-pulse facilitation increase, respectively. This inhibition by AA was unaffected by cyclo- and lipo-oxygenase inhibitors, indomethacin (20 microM) and nordihydroguaiaretic acid (NDGA, 50 microM) or by the free radical scavenger, N-acetyl-L-cysteine (0.5 mM). The K+ (20 mM)-evoked release of [3H]glutamate from superfused hippocampal synaptosomes was inhibited by 18-39% by domoate (1-10 microM), an effect attenuated by 35-63% by AA (10 microM). Finally, the KD (40-55 nM) of the kainate receptor agonist [3H]-(2S,4R)-4-methylglutamate ([3H]MGA) (0.3-120 nM) binding to hippocampal synaptosomal membranes was increased by 151-329% by AA (1-10 microM). These results indicate that AA directly inhibits presynaptic kainate receptor controlling glutamate release in the CA1 area of the rat hippocampus.

Purinergic P2 receptors trigger adenosine release leading to adenosine A2A receptor activation and facilitation of long-term potentiation in rat hippocampal slices.

Electrophysiological recordings were used to investigate the effects of ATP analogues on theta-burst-induced long-term potentiation (LTP) in rat hippocampal slices. alpha,beta-Methylene ATP (alpha,beta-MeATP; 20 microM) decreased LTP from 36+/-9% to 17+/-5%, an effect prevented by adenosine A(1) receptor blockade in accordance with the localised catabolism of ATP analogues into adenosine, leading to adenosine A(1) receptor activation. Thus, to probe the role of extracellular ATP, all experiments were performed with the A(1) receptor selective antagonist, 1,3-dipropyl-8-cyclopentylxanthine (50 nM). In these conditions, alpha,beta-MeATP or 5'-adenylylimido-diphosphate (beta,gamma-ImATP; 20 microM) facilitated LTP by 120%, an effect prevented by the P2 receptor antagonists, pyridoxalphosphate-6-azophenyl-2'-4'-disulphonic acid (PPADS; 20 microM) or suramin (75 microM), as well as by the P2X(1/3)-selective antagonist 8-(benzamido)naphthalene-1,3,5-trisulfonate (10 microM). The facilitations of LTP by either alpha,beta-MeATP or beta,gamma-ImATP (20 microM) were also prevented by both 4-(2-[7-amino-2-(2-furyl(1,2,4)-triazolo(2,3a)-(1,3,5)triazin-5-yl-amino]ethyl)phenol (50 nM) or 7-2(-phenylethyl)-5-amino-2-(2-furyl)-pyrazolo-[4,3-e]-1,2,4-triazolo[1,5-c] pyrimidine (50 nM), antagonists of facilitatory adenosine A(2A) receptors, were occluded by the A(2A) receptor agonist, CGS 21680 (10 nM) and were prevented by the protein kinase C inhibitor, chelerythrine (6 microM) and unaffected by the protein kinase A inhibitor, H89 (1 microM). Furthermore, beta,gamma-ImATP (20 microM) enhanced [(3)H]adenosine outflow from rat hippocampal slices by nearly 150%, an effect prevented by PPADS (20 microM) or suramin (75 microM). The adenosine transport inhibitors, nitrobenzylthioinosine (5 microM) and dipyridamole (10 microM) also prevented beta,gamma-ImATP (20 microM)-induced [(3)H]adenosine outflow and facilitation of LTP. These results suggest that ATP analogues facilitate LTP through P2 receptor activation that mainly triggers adenosine release leading to the activation of adenosine A(2A) receptors.