RESUMO
Previous evidence indicated a potential mechanism that might support the fact that primates exhibit greater neural integration capacity as a result of the activation of different structures of the central nervous system, as compared to rodents. The current study aimed to provide further evidence to confirm previous findings by analyzing the patterns of c-Fos expression in more neocortical structures of rats and marmosets using a more robust quantitative technique and evaluating a larger number of brain areas. Nineteen Wistar rats and 21 marmosets (Callithrix jacchus) were distributed among control groups (animals without injections) and animals injected with pentylenetetrazol (PTZ) and euthanized at different time points after stimulus. Immunohistochemical detection of c-Fos was quantified using unbiased and efficient stereological cell counting in eight neocortical regions. Marmosets had a c-Fos expression that was notably more widely expressed (5× more cells) and longer lasting (up to 3 hr) than rats. c-Fos expression in rats presented similar patterns of expression according to the function of the brain cortical structures (associative, sensorial, and motor functions), which was not observed for marmosets (in which no clear pattern could be drawn, and a more diverse profile emerged). Our results provide evidence that the marmoset brain has a greater neuronal activation after intense stimulation by means of PTZ and a more complex pattern of brain activation. We speculate that these functional differences may contribute for the understanding of the different neuronal processing capacities of the neocortex in these mammals' orders.
Assuntos
Neocórtex/fisiologia , Proteínas Proto-Oncogênicas c-fos/metabolismo , Animais , Callithrix , Antagonistas GABAérgicos/farmacologia , Masculino , Neocórtex/efeitos dos fármacos , Pentilenotetrazol/farmacologia , Ratos , Ratos WistarRESUMO
The hypothesis of enhanced vulnerability following perinatal asphyxia was investigated with a protocol combining in vivo and in vitro experiments. Asphyxia-exposed (AS) (by 21 min water immersion of foetuses containing uterine horns) and caesarean-delivered control (CS) rat neonates were used at P2-3 for preparing triple organotypic cultures (substantia nigra, neostriatum and neocortex). At DIV 18, cultures were exposed to different concentrations of H2O2 (0.25-45 mM), added to the culture medium for 18 h. After a 48-h recovery period, the cultures were either assessed for cell viability or for neurochemical phenotype by confocal microscopy. Energy metabolism (ADP/ATP ratio), oxidative stress (GSH/GSSG) and a modified ferric reducing/antioxidant power assay were applied to homogenates of parallel culture series. In CS cultures, the number of dying cells was similar in substantia nigra, neostriatum and neocortex, but it was several times increased in AS cultures evaluated under the same conditions. A H2O2 challenge led to a concentration-dependent increase in cell death (>fourfold after 0.25 mM of H2O2) in CS cultures. In AS cultures, a significant increase in cell death was only observed after 0.5 mM of H2O2. At higher than 1 mM of H2O2 (up to 45 mM), cell death increased several times in all cultures, but the effect was still more prominent in CS than in AS cultures. The cell phenotype of dying/alive cells was investigated in formalin-fixed cultures exposed to 0 or 1 mM of H2O2, co-labelling for TUNEL (apoptosis), MAP-2 (neuronal phenotype), GFAP (astroglial phenotype) and TH (tyrosine hydroxylase; for dopamine phenotype), counterstaining for DAPI (nuclear staining), also evaluating the effect of a single dose of nicotinamide (0.8 nmol/kg, i.p. injected in 100 µL, 60 min after delivery). Perinatal asphyxia produced a significant increase in the number of DAPI/TUNEL cells/mm3, in substantia nigra and neostriatum. One millimolar of H202 increased the number of DAPI/TUNEL cells/mm3 by ≈twofold in all regions of CS and AS cultures, an effect that was prevented by neonatal nicotinamide treatment. In substantia nigra, the number of MAP-2/TH-positive cells/mm3 was decreased in AS compared to CS cultures, also by 1 mM of H202, both in CS and AS cultures, prevented by nicotinamide. In agreement, the number of MAP-2/TUNEL-positive cells/mm3 was increased by 1 mM H2O2, both in CS (twofold) and AS (threefold) cultures, prevented by nicotinamide. The number of MAP-2/TH/TUNEL-positive cells/mm3 was only increased in CS (>threefold), but not in AS (1.3-fold) cultures. No TH labelling was observed in neostriatum, but 1 mM of H2O2 produced a strong increase in the number of MAP-2/TUNEL-positive cells/mm3, both in CS (>2.9-fold) and AS (>fourfold), decreased by nicotinamide. In neocortex, H2O2 increased the number of MAP-2/TUNEL-positive cells/mm3, both in CS and AS cultures (≈threefold), decreased by nicotinamide. The ADP/ATP ratio was increased in AS culture homogenates (>sixfold), compared to CS homogenates, increased by 1 mM of H202, both in CS and AS homogenates. The GSH/GSSG ratio was significantly decreased in AS, compared to CS cultures. One millimolar of H2O2 decreased that ratio in CS and AS homogenates. The present results demonstrate that perinatal asphyxia induces long-term changes in metabolic pathways related to energy and oxidative stress, priming cell vulnerability with both neuronal and glial phenotype. The observed effects were region dependent, being the substantia nigra particularly prone to cell death. Nicotinamide administration in vivo prevented the deleterious effects observed after perinatal asphyxia in vitro, a suitable pharmacological strategy against the deleterious consequences of perinatal asphyxia.
Assuntos
Asfixia Neonatal/tratamento farmacológico , Neocórtex/efeitos dos fármacos , Neostriado/efeitos dos fármacos , Fármacos Neuroprotetores/farmacologia , Niacinamida/farmacologia , Substância Negra/efeitos dos fármacos , Animais , Animais Recém-Nascidos , Asfixia Neonatal/metabolismo , Asfixia Neonatal/patologia , Astrócitos/efeitos dos fármacos , Astrócitos/metabolismo , Astrócitos/patologia , Morte Celular/efeitos dos fármacos , Morte Celular/fisiologia , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/fisiologia , Modelos Animais de Doenças , Suscetibilidade a Doenças , Neurônios Dopaminérgicos/efeitos dos fármacos , Neurônios Dopaminérgicos/metabolismo , Neurônios Dopaminérgicos/patologia , Relação Dose-Resposta a Droga , Feminino , Peróxido de Hidrogênio/metabolismo , Masculino , Neocórtex/metabolismo , Neocórtex/patologia , Neostriado/metabolismo , Neostriado/patologia , Técnicas de Cultura de Órgãos , Estresse Oxidativo/efeitos dos fármacos , Estresse Oxidativo/fisiologia , Ratos Wistar , Substância Negra/metabolismo , Substância Negra/patologiaRESUMO
Nowadays, it is known that brain derived neurotrophic-factor (BDNF) is a protein critically involved in regulating long-term memory related mechanisms. Previous studies from our group in the insular cortex (IC), a brain structure of the temporal lobe implicated in acquisition, consolidation and retention of conditioned taste aversion (CTA), demonstrated that BDNF is essential for CTA consolidation. Recent studies show that BDNF-TrkB signaling is able to mediate the enhancement of memory. However, whether BDNF into neocortex is able to enhance aversive memories remains unexplored. In the present work, we administrated BDNF in a concentration capable of inducing in vivo neocortical LTP, into the IC immediately after CTA acquisition in two different conditions: a "strong-CTA" induced by 0.2M lithium chloride i.p. as unconditioned stimulus, and a "weak-CTA" induced by 0.1M lithium chloride i.p. Our results show that infusion of BDNF into the IC converts a weak CTA into a strong one, in a TrkB receptor-dependent manner. The present data suggest that BDNF into the adult insular cortex is sufficient to increase an aversive memory-trace.
Assuntos
Aprendizagem da Esquiva/efeitos dos fármacos , Fator Neurotrófico Derivado do Encéfalo/farmacologia , Memória/efeitos dos fármacos , Neocórtex/efeitos dos fármacos , Nootrópicos/farmacologia , Percepção Gustatória/efeitos dos fármacos , Animais , Aprendizagem da Esquiva/fisiologia , Cateteres de Demora , Condicionamento Psicológico/efeitos dos fármacos , Condicionamento Psicológico/fisiologia , Cloreto de Lítio , Masculino , Memória/fisiologia , Microinjeções , Neocórtex/fisiologia , Ratos Wistar , Percepção Gustatória/fisiologia , Privação de ÁguaRESUMO
Higher cognitive functions require the integration and coordination of large populations of neurons in cortical and subcortical regions. Oscillations in the gamma band (30-45 Hz) of the electroencephalogram (EEG) have been involved in these cognitive functions. In previous studies, we analysed the extent of functional connectivity between cortical areas employing the 'mean squared coherence' analysis of the EEG gamma band. We demonstrated that gamma coherence is maximal during alert wakefulness and is almost absent during rapid eye movement (REM) sleep. The nucleus pontis oralis (NPO) is critical for REM sleep generation. The NPO is considered to exert executive control over the initiation and maintenance of REM sleep. In the cat, depending on the previous state of the animal, a single microinjection of carbachol (a cholinergic agonist) into the NPO can produce either REM sleep [REM sleep induced by carbachol (REMc)] or a waking state with muscle atonia, i.e. cataplexy [cataplexy induced by carbachol (CA)]. In the present study, in cats that were implanted with electrodes in different cortical areas to record polysomnographic activity, we compared the degree of gamma (30-45 Hz) coherence during REMc, CA and naturally-occurring behavioural states. Gamma coherence was maximal during CA and alert wakefulness. In contrast, gamma coherence was almost absent during REMc as in naturally-occurring REM sleep. We conclude that, in spite of the presence of somatic muscle paralysis, there are remarkable differences in cortical activity between REMc and CA, which confirm that EEG gamma (≈40 Hz) coherence is a trait that differentiates wakefulness from REM sleep.
Assuntos
Carbacol/farmacologia , Cataplexia/fisiopatologia , Agonistas Colinérgicos/farmacologia , Neurônios/efeitos dos fármacos , Sono REM/efeitos dos fármacos , Animais , Cataplexia/induzido quimicamente , Gatos , Eletroencefalografia/métodos , Neocórtex/efeitos dos fármacos , Neurônios/fisiologia , Ponte/efeitos dos fármacos , Ponte/fisiologia , Vigília/efeitos dos fármacosRESUMO
In hippocampal slices, inhibition of AMPA receptors unmasks synaptic transmission via NMDA receptors, suggesting that AMPA receptor activation normally inhibits synaptic transmission via NMDA receptors. Activation of NMDA receptors is involved in the pathogenesis of cortical spreading depression (CSD) which has been implicated in the pathogenesis of migraine aura and neuronal damage from peri-infarct depolarizations. In this study we examined whether NMDA receptor transmission could be unmasked in the neocortex in vivo by AMPA receptor blockage and whether AMPA receptors could affect CSD induced by 200 mM KCl. We further compared the effects of AMPA to those of the NMDA receptor antagonist, 2-amino-5-phosphono-pentanoic acid (2AP5), and the GABA-mimetic drug clomethiazole. The NMDA receptor antagonist MK-801 did not affect the baseline somatosensory evoked potentials (SEPs). In a medium with no Mg(2+), the AMPA receptor antagonist 6,7-dinitroquinoxaline-2,3-dione (DNQX) caused marked reduction in the SEP size which subsequently recovered partially; MK-801 blocked these partially recovered SEPs. AMPA (50 µM but not at 5 µM or 250 µM) and 2AP5 (10 µM) significantly reduced the number of CSD cycles. The effect of AMPA was not changed by co-applying it with cyclothiazide, which blocks AMPA receptor desensitization. Clomethiazole (100 mg/kg i.p.) did not significantly affect the number of CSD cycles. Only 2AP5 significantly reduced the potentiation that follows CSD. We conclude that activation of AMPA receptors can suppress the actions of NMDA receptors in the neocortex; this could be an intrinsic protective mechanism against CSD and also provide a possible therapeutic strategy against CSD-related neurological conditions.
Assuntos
Clormetiazol/farmacologia , Depressão Alastrante da Atividade Elétrica Cortical/efeitos dos fármacos , Receptores de AMPA/efeitos dos fármacos , Ácido alfa-Amino-3-hidroxi-5-metil-4-isoxazol Propiônico/farmacologia , Animais , Maleato de Dizocilpina/farmacologia , Relação Dose-Resposta a Droga , Potenciais Somatossensoriais Evocados/efeitos dos fármacos , Agonistas de Aminoácidos Excitatórios/administração & dosagem , Agonistas de Aminoácidos Excitatórios/farmacologia , Moduladores GABAérgicos/farmacologia , Masculino , Neocórtex/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Receptores de AMPA/metabolismo , Receptores de N-Metil-D-Aspartato/efeitos dos fármacos , Receptores de N-Metil-D-Aspartato/metabolismo , Transmissão Sináptica/efeitos dos fármacos , Ácido alfa-Amino-3-hidroxi-5-metil-4-isoxazol Propiônico/administração & dosagemRESUMO
The present study investigated the effects of toluene inhalation and the restorative effects of melatonin on branching and basal dendritic outgrowth of superficial pyramidal neurons in rat's frontal, parietal, and occipital cortices. At postnatal day 21 (P21), Sprague-Dawley male rats were randomly assigned to either an air-only group or a toluene group. From P22 to P32 the animals were exposed to either clean air or toluene vapors (5000-6000 ppm) for 10 min/day. This strategy simulated common toluene abuse in humans, which consists of 15-20 rapid inhalations of highly concentrated solvent. Once the inhalation period was over (P32), toluene exposed animals were randomly reassigned to one of following experimental groups: (i) air-control/saline; (ii) toluene/saline; (iii) toluene/melatonin 0.5mg/kg; (iv) toluene/melatonin 1.0mg/kg; (v) toluene/melatonin 5.0mg/kg; and (vi) toluene/melatonin 10mg/kg. Seven days after the last inhalation (P39), all the animals were sacrificed under deep anesthesia; brains were dissected out and stained according to the Golgi-Cox-Sholl procedure. Layer II/III pyramidal neurons were morphologically analyzed by measuring their basilar dendritic length and the number of branches. The results obtained revealed that (i) toluene inhalation significantly reduced dendritic outgrowth and branching in all cortical areas studied, and (ii) intraperitoneal administration of melatonin (0.5-10mg/kg) was able to restore the dendritic impairment induced by toluene exposure.
Assuntos
Dendritos/efeitos dos fármacos , Melatonina/farmacologia , Neocórtex/efeitos dos fármacos , Fármacos Neuroprotetores/farmacologia , Células Piramidais/efeitos dos fármacos , Tolueno/toxicidade , Animais , Dendritos/patologia , Feminino , Exposição por Inalação/efeitos adversos , Masculino , Melatonina/administração & dosagem , Melatonina/uso terapêutico , Neocórtex/patologia , Fármacos Neuroprotetores/administração & dosagem , Fármacos Neuroprotetores/uso terapêutico , Síndromes Neurotóxicas/etiologia , Síndromes Neurotóxicas/patologia , Síndromes Neurotóxicas/prevenção & controle , Células Piramidais/patologia , Ratos , Ratos Sprague-Dawley , DesmameRESUMO
Modafinil is a novel wake-promoting agent whose effects on cognitive performance have begun to be addressed at both preclinical and clinical level. The present study was designed to investigate in rats the effects of chronic modafinil administration on cognitive performance by evaluating: (i) working and reference memories in an Olton 4×4 maze, and (ii) learning of a complex operant conditioning task in a Skinner box. In addition, the effect of modafinil on the ability of the rat frontal cortex to develop long-term potentiation (LTP) was also studied. Chronic modafinil did not significantly modify working memory errors but decreased long-term memory errors on the Olton 4×4 maze, meaning that the drug may have a favourable profile on performance of visuo-spatial tasks (typically, a hippocampus-dependent task) when chronically administered. On the other hand, chronic modafinil resulted in a marked decrease of successful responses in a complex operant conditioning learning, which means that repeated administration of the drug influences negatively problem-solving abilities when confronting the rat to a sequencing task (typically, a prefrontal cortex-dependent task). In addition, in vivo electrophysiology showed that modafinil resulted in impaired capacity of the rat prefrontal cortex to develop LTP following tetanization. It is concluded that modafinil can improve the performance of spatial tasks that depend almost exclusively on hippocampal functioning, but not the performance in tasks including a temporal factor where the prefrontal cortex plays an important role. The fact that modafinil together with preventing operant conditioning learning was also able to block LTP induction in the prefrontal cortex, suggests that the drug could interfere some critical component required for LTP can be developed, thereby altering neuroplastic capabilities of the prefrontal cortex.
Assuntos
Compostos Benzidrílicos/farmacologia , Estimulantes do Sistema Nervoso Central/farmacologia , Aprendizagem/efeitos dos fármacos , Potenciação de Longa Duração/efeitos dos fármacos , Neocórtex/efeitos dos fármacos , Neocórtex/fisiologia , Animais , Condicionamento Operante/efeitos dos fármacos , Masculino , Memória de Curto Prazo/efeitos dos fármacos , Modafinila , Ratos , Ratos Sprague-DawleyRESUMO
beta-Adrenergic receptor stimulation can significantly facilitate synaptic potentiation in the hippocampus and enhance memory processes, but its effect on neocortical plastic mechanisms is less conclusive. In the present study we determined the effect of propranolol, a beta-adrenoceptor antagonist, on long-term potentiation (LTP) induced in vivo in rat occipital cortex by tetanizing stimulation of corpus callosum and observed a dose-dependent inhibition of LTP. We further administered propranolol through mini-osmotic pumps during 3 days, and observed the performance of rats in a complex operant conditioning learning paradigm and assessed the expression of brain-derived neurotrophic factor (BDNF) in the occipital cortex. Propranolol exposure depressed both the number of reinforced responses in the operant conditioning task and BDNF expression in occipital cortex. Taken together, our results suggest that propranolol impairs memory formation by inhibiting cortical LTP induction and associated BDNF expression.
Assuntos
Regulação da Expressão Gênica/fisiologia , Neocórtex/fisiologia , Plasticidade Neuronal/fisiologia , Receptores Adrenérgicos beta/metabolismo , Antagonistas Adrenérgicos beta/farmacologia , Análise de Variância , Animais , Fator Neurotrófico Derivado do Encéfalo/administração & dosagem , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Condicionamento Operante/fisiologia , Corpo Caloso/fisiologia , Relação Dose-Resposta a Droga , Estimulação Elétrica/métodos , Regulação da Expressão Gênica/efeitos dos fármacos , Potenciação de Longa Duração/efeitos dos fármacos , Potenciação de Longa Duração/fisiologia , Masculino , Neocórtex/efeitos dos fármacos , Plasticidade Neuronal/efeitos dos fármacos , Propranolol/farmacologia , Ratos , Ratos Sprague-Dawley , Fatores de TempoRESUMO
Previous studies suggest the presence of a minicolumnopathy in autism. Minicolumnar abnormalities as well as certain migratory and proliferative defects, common to autism, may be rooted in the general mechanics of periventricular germinal cell division and maturation. Increased numbers of periventricular germinal cell/radial glia can be mimicked by a variety of different transgenic mouse models and environmental factors. These murine models and environmental factors illustrate how a fairly homogenous neuroanatomical phenotype can diverge at the genetic level. By first defining the lowest common denominator (i.e., the minicolumn) and then examining which pathways are vulnerable to involved genetic and environmental factors, we may gain a greater understanding of the pathophysiologic mechanisms underlying Autism Spectrum Conditions.
Assuntos
Transtorno Autístico/classificação , Neocórtex/patologia , Animais , Transtorno Autístico/epidemiologia , Transtorno Autístico/genética , Transtorno Autístico/patologia , Divisão Celular , Linhagem da Célula , Movimento Celular , Modelos Animais de Doenças , Exposição Ambiental , Epigênese Genética , Heterogeneidade Genética , Hormônios/efeitos adversos , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/genética , Peptídeos e Proteínas de Sinalização Intracelular/fisiologia , Redes e Vias Metabólicas , Camundongos , Camundongos Transgênicos , Mutação , Neocórtex/efeitos dos fármacos , Neocórtex/embriologia , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/fisiologia , Neuroglia/patologia , Células-Tronco Pluripotentes/patologia , Especificidade da Espécie , Teratogênicos/toxicidadeRESUMO
UNLABELLED: Perinatal asphyxia occurs in approximately 0.3% full-term newborn babies, and this percentage has not decreased despite medical advances. There are now evidences indicating that neurosteroids are important in neurodevelopment showing neuroprotective effects. We studied the potential protective effect of allopregnanolone (Allo) in vitro using organotypic cultures from neocortex, striatum, and hippocampus. Immunocytochemistry and confocal microscopy showed an increase of the glial fibrillary acidic protein (GFAP) signal in the studied brain areas after hypoxia. Western blot studies supported these results (hippocampus, 193%; neocortex, 306%; and striatum, 231%). Twenty-four-hour pretreatment with Allo showed different effects at the brain areas studied. In the hippocampus and the neocortex, 24-h pretreatment with Allo 5x10(-6) M showed to be neuroprotective as there was a significant decrease of the GFAP signal compared to control cultures exposed to hypoxia. Pretreatment with 5x10(-8) M Allo attenuated the astrogliosis response in the hippocampus and the neocortex in a nonsignificant way. Allo pretreatment at all doses did not show to affect the astrogliosis triggered by hypoxia in the striatum. Cell survival was analyzed by measuring LDH. After 1 h of hypoxia, all cultures showed a nonsignificant increase of LDH, which was greater after 24 h of hypoxia (hippocampus, 180%; striatum-cortex co-cultures, 140%). LDH levels have no changes by Allo pretreatment before hypoxia. CONCLUSION: 24 h pretreatment with 5x10(-6) M of Allo does not change neuronal viability but it prevents astrogliosis induced by hypoxia in the hippocampus and the neocortex.