RESUMO
The brain is one of the first organs affected during sepsis development resulting in apoptosis for a short-term and cognitive impairment for a long-term. Despite its importance, the mechanisms of brain dysfunction during sepsis are not fully elucidated. Thus, we here, in an animal model of sepsis, evaluated apoptosis in the dentate gyrus cell layer of the hippocampus to document the involvement of caspase-3 in the pathogenesis of neuronal apoptosis. Wistar rats sham-operated or submitted to the cecal ligation and perforation (CLP) procedure were killed at 12, 24, 48 h, and 10 days after surgery for the determination of caspase-3 and apoptosis rate. In a separate cohort of animals, a caspase-3-specific inhibitor was administered and animals were killed at 12 h after sepsis. An increase in the number of apoptotic cells 12, 24, and 48 h by histopathological evaluations and an increase of caspase-3 apoptotic cells 12 and 24 h after sepsis induction were observed. The caspase-3 inhibitor decreases the number of apoptotic cells by histopathological evaluations but not by immunohistochemistry evaluations. Caspase-3 is involved in part in apoptosis in the dentate gyrus cell layer of the hippocampus in septic rats submitted by CLP.
Assuntos
Apoptose , Caspase 3/metabolismo , Hipocampo/enzimologia , Hipocampo/patologia , Sepse/patologia , Animais , Giro Denteado/enzimologia , Giro Denteado/patologia , Masculino , Ratos , Ratos Wistar , Sepse/enzimologiaRESUMO
Although the hypothalamus has been long considered the main ghrelin (Ghr) target organ mediating orexigenic effects, recently it has been shown that in-vivo Ghr hippocampus administration improves learning and memory in the inhibitory avoidance paradigm. However, the possible mechanisms underlying this memory facilitation effect have not been clarified. Given that the biochemical memory cascade into the hippocampus involves nitric oxide (NO) synthesis via NO synthase (NOS) activation, we investigated 1) if Ghr administration modulated NOS activity in the hippocampus; and 2) if hippocampal NOS inhibition influenced Ghr-induced memory facilitation, using a behavioral paradigm, biochemical determinations and an electrophysiological model. Our results showed that intra-hippocampal Ghr administration increased the NOS activity in a dose dependent manner, and reduced the threshold for LTP generation in dentate gyrus of rat hippocampus. Moreover, pre-administration of NG-nitro-l-arginine (l-NOArg) in the hippocampus partially prevented the Ghr-induced memory improvement, abolished the increase in NOS activity, and prevented the decreased threshold to generate LTP induced by Ghr. These findings suggest that activation of the NOS/NO pathway in hippocampus participates in the effects of Ghr on memory consolidation and is related with plastic properties of the hippocampal three-synaptic loop.
Assuntos
Giro Denteado/enzimologia , Grelina/fisiologia , Potenciação de Longa Duração/fisiologia , Memória/fisiologia , Óxido Nítrico Sintase/metabolismo , Análise de Variância , Animais , Aprendizagem da Esquiva/fisiologia , Giro Denteado/efeitos dos fármacos , Giro Denteado/fisiologia , Relação Dose-Resposta a Droga , Ativação Enzimática , Grelina/administração & dosagem , Técnicas In Vitro , Potenciação de Longa Duração/efeitos dos fármacos , Masculino , Memória/efeitos dos fármacos , Óxido Nítrico Sintase/efeitos dos fármacos , Ratos , Ratos Wistar , Análise de Regressão , Sistemas do Segundo Mensageiro/fisiologia , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/fisiologiaRESUMO
In 30- and 90-day-old rats, using immunohistochemistry for glutamic acid decarboxylase 67 (GAD-67), we have tested whether malnutrition during different periods of hippocampal development produces deleterious effects on the population of GABA neurons in the dentate gyrus (DG) and cornu Ammonis (CA1-3) of the dorsal hippocampus. Animals were under one of four nutritional conditions: well-nourished controls (Con), prenatal protein malnourished (PreM), postnatal protein malnourished (PostM), and chronic protein malnourished (ChroM). We found that the number of GAD-67-positive (GAD-67+) interneurons was higher in the DG than in the CA1-3 areas of both Con and malnourished groups. Regarding the DG, the number of GAD-67+ interneurons was increased in PreM and PostM and decreased in ChroM at 30 days. At 90 days of age the number of GAD-67+ interneurons was increased in PostM and ChroM and remained unchanged in PreM. With respect to CA1-3, the number of labeled interneurons was decreased in PostM and ChroM at 30 days of age, but no change was found in PreM. At 90 days no changes in the number of these interneurons were found in any of the groups. These observations suggest that 1) the cell death program starting point is delayed in DG GAD-67+ interneurons, and 2) protein malnutrition differentially affects GAD-67+ interneuron development throughout the dorsal hippocampus. Thus, these changes in the number of GAD-67+ interneurons may partly explain the alterations in modulation of dentate granule cell excitability, as well as in the emotional, motivational, and memory disturbances commonly observed in malnourished rats.
Assuntos
Giro Denteado/patologia , Glutamato Descarboxilase/metabolismo , Hipocampo/patologia , Interneurônios/patologia , Desnutrição Proteico-Calórica/enzimologia , Desnutrição Proteico-Calórica/patologia , Envelhecimento/metabolismo , Animais , Animais Recém-Nascidos , Contagem de Células , Giro Denteado/enzimologia , Embrião de Mamíferos/enzimologia , Doenças Fetais/enzimologia , Doenças Fetais/patologia , Hipocampo/enzimologia , Imuno-Histoquímica , Interneurônios/enzimologia , Ratos , Ratos Sprague-DawleyRESUMO
PURPOSE: We describe the use of a clinically relevant pharmacological intervention that alters the clinical history of status epilepticus (SE)-induced spontaneous recurrent seizures (SRS) in the pilocarpine model and the possible plastic changes underlying such an effect. METHODS: Two hours after pilocarpine-induced SE (320-350 mg/kg, i.p.), rats received scopolamine 1-2 mg/kg i.p. or saline, every 6 h for 3 days. After that, osmotic minipumps were implanted for continuous delivery of scopolamine or saline for an additional 14 days. Animals were video-monitored for 12 h/week during the following 3-month period for the occurrence of SRS and, thereafter, were perfused, processed, and coronal brain sections were stained for acetylcholinesterase (AChE) and for the presence of supragranular mossy fibers (Timm). RESULTS: Treatment with scopolamine led to significantly fewer SRS. Staining for AChE in the dentate gyrus was significantly more intense in naïve animals. The scopolamine group had the least intense AChE staining of all groups. However, regression analysis of the AChE staining for this group did not correlate with the presence or absence of SRS, or the latency or frequency of SRS. Supragranular mossy fiber sprouting developed in all animals experiencing pilocarpine-induced SE, irrespective of whether or not they were treated with scopolamine. CONCLUSIONS: Pilocarpine-induced SE in the presence of scopolamine might produce animals that, despite mossy fiber sprouting, were not seen to exhibit spontaneous seizures. In addition, our data suggest that the encountered changes in the AChE staining in the dentate gyrus that followed treatment with scopolamine do not help to explain its disease-modifying effects.
Assuntos
Antagonistas Muscarínicos/farmacologia , Plasticidade Neuronal/efeitos dos fármacos , Pilocarpina , Escopolamina/farmacologia , Convulsões/prevenção & controle , Estado Epiléptico/induzido quimicamente , Acetilcolinesterase/metabolismo , Animais , Giro Denteado/efeitos dos fármacos , Giro Denteado/enzimologia , Giro Denteado/fisiopatologia , Modelos Animais de Doenças , Masculino , Fibras Musgosas Hipocampais/enzimologia , Fibras Musgosas Hipocampais/metabolismo , Ratos , Ratos Wistar , Convulsões/enzimologia , Convulsões/fisiopatologia , Estado Epiléptico/fisiopatologiaRESUMO
PURPOSE: Adenosine is a major negative neuromodulator of synaptic activity in the central nervous system and can exert anticonvulsant and neuroprotective effects in many experimental models of epilepsy. Extracellular adenosine can be formed by a membrane-anchored enzyme ecto-5'-nucleotidase. The purposes of this study were to characterize the role of adenosine receptors in modulating status epilepticus (SE) induced by pilocarpine and evaluate its neuroprotective action. Ecto-5'-nucleotidase activity was studied during the different phases of pilocarpine-induced epilepsy in rats. METHODS: Adult rats were pretreated with different adenosinergic agents to evaluate the latency and incidence of SE induced by pilocarpine in rats. The neuroprotective effect also was evaluated. RESULTS: A proconvulsant effect was observed with DPCPX and DMPX that reduced the latency of SE in almost all rats. Pretreatment with the MRS 1220 did not alter the incidence of SE but reduced the latency to develop SE. An anticonvulsant and neuroprotective effect was detected with R-PIA. Rats pretreated with R-PIA had a decreased number of apoptotic cells in the hippocampus, whereas pretreatment with DPCPX did not modify the hippocampal damage. An intensification of neuronal death was observed in the dentate gyrus and CA3 when rats were pretreated with DMPX. MRS-1220 did not modify the number of apoptotic cells in the hippocampus. An increase in the ecto-5 -nucleotidase staining was detected in the hippocampus during silent and chronic phases. CONCLUSIONS: The present data show that adenosine released during pilocarpine-induced SE via A1-receptor stimulation can exhibit neuroprotective and anticonvulsant roles. Similar effects could also be inferred with A2a and A3 adenosinergic agents, but further experiments are necessary to confirm their roles. Ecto-5 -nucleotidase activity during silent and chronic phases might have a role in blocking spontaneous seizures by production of inhibitory neuromodulator adenosine, besides taking part in the mechanism that controls sprouting.
Assuntos
Adenosina/análogos & derivados , Modelos Animais de Doenças , Epilepsia do Lobo Temporal/fisiopatologia , Plasticidade Neuronal/fisiologia , Receptores Purinérgicos P1/fisiologia , Sinapses/fisiologia , 5'-Nucleotidase/metabolismo , Adenosina/farmacologia , Animais , Giro Denteado/efeitos dos fármacos , Giro Denteado/enzimologia , Giro Denteado/metabolismo , Epilepsia do Lobo Temporal/enzimologia , Epilepsia do Lobo Temporal/prevenção & controle , Hipocampo/efeitos dos fármacos , Hipocampo/enzimologia , Hipocampo/metabolismo , Marcação In Situ das Extremidades Cortadas , Masculino , Fármacos Neuroprotetores/farmacologia , Pilocarpina , Antagonistas de Receptores Purinérgicos P1 , Quinazolinas/farmacologia , Ratos , Ratos Wistar , Receptores Purinérgicos P1/metabolismo , Estado Epiléptico/induzido quimicamente , Estado Epiléptico/metabolismo , Estado Epiléptico/prevenção & controle , Triazóis/farmacologia , Xantinas/farmacologiaRESUMO
Tissue distribution of nitric oxide-synthases was investigated in the rat hippocampus and visual cortex under nutritional changes induced by modification of the litter size. Young (30-45-days-old) rats, suckled in litters formed by 3,6 or 12 pups (called small, medium and large litters, respectively), were studied by using nicotine-adenine-dinucleotide phosphate-diaphorase histochemistry (shortly, diaphorase), a simple and robust procedure to characterize tissue distribution of nitric oxide-synthases. We assessed morphometric features of the diaphorase-positive cells in visual cortex, and the neuropil histochemical activity in hippocampal CA1 and dentate gyrus using densitometry analysis. In the large-litter group, the labeled-cell density in white matter of area 17 was higher, as compared to the small-litter group. There was a clear trend, in the large-litter group, to lower values of soma area, dendritic field and branches per neuron, but the differences were not significant. Densitometry analysis of hippocampus revealed a significant increase in the relative neuropil histochemical activity of the dentate gyrus molecular layer in the larger litters, which may be associated to increased compensatory blood flow in the hippocampus. The pathophysiological mechanisms of the observed changes remain to be investigated.
Assuntos
Hipocampo/enzimologia , Lactação , Tamanho da Ninhada de Vivíparos , NADPH Desidrogenase/análise , Neurônios/enzimologia , Córtex Visual/enzimologia , Animais , Densitometria , Giro Denteado/enzimologia , Histocitoquímica , Neurópilo/enzimologia , Ratos , Ratos Wistar , DesmameRESUMO
Stimulation of the hippocampal formation can modulate nociceptive mechanisms, whereas painful stimuli can activate this structure. Stress exposure can produce plastic changes in the hippocampus. Nitric oxide (NO) is an important neuroregulatory agent present in the hippocampus. The objective of the present study was to investigate the effects of intrahippocampal administration of N(omega)-nitro-L-arginine methyl ester hydrochloride (L-NAME), an inhibitor of NO synthase (NOS), on nociceptive processes in stressed and nonstressed rats. Male Wistar rats (n=6-11/group) received unilateral microinjection of L-NAME (50-300 nmol/0.2 microl) into the dentate gyrus (DG) of the dorsal hippocampus. Immediately after the injection tail-flick reflex latency was measured. Stressed animals were submitted to 2 h of restraint and tested immediately or 1, 2, 5 or 10 days later. L-NAME failed to modify nociception in nonstressed rats. However, 5 days after, restraint L-NAME, at all doses tested, produced an antinociceptive effect (ANOVA, P<.05). The dose-response curve had an inverted U shape. L-NAME antinociceptive effect was antagonized by previous treatment with L-arginine (150 nmol/0.2 microl, P<.05). The results suggest that the modulation of nociceptive processes by NO in the dorsal hippocampus is dependent on previous stress exposure and on poststress interval.
Assuntos
Giro Denteado/enzimologia , Inibidores Enzimáticos/farmacologia , Óxido Nítrico Sintase/antagonistas & inibidores , Óxido Nítrico/fisiologia , Estresse Psicológico/enzimologia , Estresse Psicológico/psicologia , Animais , Giro Denteado/efeitos dos fármacos , Relação Dose-Resposta a Droga , Masculino , Microinjeções , NG-Nitroarginina Metil Éster/farmacologia , Óxido Nítrico Sintase Tipo I , Medição da Dor/efeitos dos fármacos , Ratos , Ratos Wistar , Tempo de Reação/efeitos dos fármacos , Restrição Física , Técnicas EstereotáxicasRESUMO
Two groups of Sprague-Dawley male rats received bilateral aspirative lesions of the fimbria fornix under chloral hydrate anesthesia. One group (n = 9) received no further treatment (lesioned). In the second group (n = 8), a piece of septal fetal tissue, obtained at day E15-16, was implanted into each lesion cavity (transplanted). A third group consisted of shamlesioned rats (controls, n = 14). Two months after the operations, a recording electrode was implanted in the hilar region of the dentate gyrus of each animal, and a bipolar stimulating electrode was implanted in the perforant path. Long-term potentiation at 400 Hz was induced and followed for two hours. FF-lesioned rats showed an impaired potentiation of the field excitatory post-synaptic potential, which rapidly declined to basal levels within 15 minutes. The transplanted rats showed a normal potentiation of this parameter, similar to that seen in the control animals. A decrease in choline acetyltransferase activity in the hippocampi of the lesioned animals showed a tendency toward recovery after septal fetal tissue transplantation. In all the dorsal hippocampal areas of the lesioned animals, acetylcholinesterase histochemistry showed an almost complete loss of enzymatic activity, which was partially restored by the transplants. The improved synaptic plasticity in the transplanted animals might be related to septal transplant-induced recovery of mnemonic functions.