RESUMO
Despite it being abhorrent and illegal, torture is sometimes employed for information gathering. However, the extreme stressors employed during torture force the brain away from the relatively narrow, adaptive range of function it operates within. Torture degrades signal-to-noise ratios of information yield and increases false positive discovery rates. As a discovery methodology, torture fails basic tests of veridical, reliable and replicable information discovery. Torture fails during interrogation because it is an assault on our core integrated, social, psychological and neural functioning. There is a need for a profound cultural shift regarding torture, recognizing that torture impairs, rather than facilitates, investigations and truth-finding. Rising to this challenge will increase operational effectiveness, eliminate prisoner abuse and torment, and aid veridical and actionable information gathering. Policy regarding prisoner and detainee interrogation need to be refocused as a behavioural and brain sciences problem, and not simply treated as a legal, ethical or philosophical problem. Getting the science, ethics and practice in line is a challenge, but it can and should be done.
Assuntos
Cognição/fisiologia , Prisioneiros/psicologia , Tortura/psicologia , Humanos , Memória/fisiologia , Filosofia , Mecânica Respiratória/fisiologia , Privação do Sono/psicologia , Estresse Psicológico/fisiopatologia , Estresse Psicológico/psicologia , Sinapses/fisiologia , Tortura/ética , Revelação da VerdadeRESUMO
Schizophrenia is a neurodevelopmental disorder that affects up to 1% of the general population. Various genes show associations with schizophrenia and a very weak nominal association with the tight junction protein, claudin-5, has previously been identified. Claudin-5 is expressed in endothelial cells forming part of the blood-brain barrier (BBB). Furthermore, schizophrenia occurs in 30% of individuals with 22q11 deletion syndrome (22q11DS), a population who are haploinsufficient for the claudin-5 gene. Here, we show that a variant in the claudin-5 gene is weakly associated with schizophrenia in 22q11DS, leading to 75% less claudin-5 being expressed in endothelial cells. We also show that targeted adeno-associated virus-mediated suppression of claudin-5 in the mouse brain results in localized BBB disruption and behavioural changes. Using an inducible 'knockdown' mouse model, we further link claudin-5 suppression with psychosis through a distinct behavioural phenotype showing impairments in learning and memory, anxiety-like behaviour and sensorimotor gating. In addition, these animals develop seizures and die after 3-4 weeks of claudin-5 suppression, reinforcing the crucial role of claudin-5 in normal neurological function. Finally, we show that anti-psychotic medications dose-dependently increase claudin-5 expression in vitro and in vivo while aberrant, discontinuous expression of claudin-5 in the brains of schizophrenic patients post mortem was observed compared to age-matched controls. Together, these data suggest that BBB disruption may be a modifying factor in the development of schizophrenia and that drugs directly targeting the BBB may offer new therapeutic opportunities for treating this disorder.
Assuntos
Claudina-5/genética , Claudina-5/fisiologia , Esquizofrenia/metabolismo , Síndrome da Deleção 22q11/genética , Síndrome da Deleção 22q11/psicologia , Animais , Barreira Hematoencefálica/metabolismo , Encéfalo/metabolismo , Modelos Animais de Doenças , Células Endoteliais/metabolismo , Feminino , Perfilação da Expressão Gênica/métodos , Células HEK293 , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Esquizofrenia/fisiopatologia , Junções ÍntimasRESUMO
The subiculum is a pivotal structure located in the hippocampal formation that receives inputs from grid and place cells and that mediates the output from the hippocampus to cortical and sub-cortical areas. Previous studies have demonstrated the existence of boundary vector cells (BVC) in the subiculum, as well as exceptional stability during recordings conducted in the dark, suggesting that the subiculum is involved in the coding of allocentric cues and also in path integration. In order to better understand the role of the subiculum in spatial processing and the coding of external cues, we recorded subicular units in freely moving rats while performing two experiments: the "size experiment" in which we modified the arena size, and the "barrier experiment" in which we inserted new barriers in a familiar open field thus dividing the enclosure into four comparable sub-chambers. We hypothesized that if physical boundaries were deterministic of the firing of subicular units a strong spatial replication pattern would be found in most spatially modulated units. In contrast, our results demonstrate heterogeneous space coding by different cell types: place cells, barrier-related units and BVC. We also found units characterized by narrow spike waveforms, most likely belonging to axonal recordings, that showed grid-like patterns. Our data indicate that the subiculum codes space in a flexible manner, and that it is involved in the processing of allocentric information, external cues and path integration, thus broadly supporting spatial navigation.
Assuntos
Hipocampo/fisiologia , Neurônios/fisiologia , Percepção Espacial/fisiologia , Potenciais de Ação , Animais , Eletrodos Implantados , Comportamento Exploratório/fisiologia , Masculino , Atividade Motora/fisiologia , RatosRESUMO
Hippocampally-driven oscillatory activity at theta frequency is found in the diencephalon, but an understanding of the fundamental role of theta in the hippocampo-diencephalic circuit remains elusive. An important strategy in determining how activity modifies oscillatory properties of hippocampo-diencephalic circuitry comprises investigations of anterior thalamic responses to their main inputs: the descending dorsal fornix and the ascending mammillothalamic tract. Here, we show that the amplitude of thalamic theta spectral power selectively increases after plasticity-inducing stimulation of the dorsal fornix, but not of the mammillothalamic tract in urethane-anaesthetized young male rats. Furthermore, we show that low-frequency stimulation (LFS) significantly augments the fornix-driven theta ratio (theta over delta power, T-ratio), in parallel with depressing thalamic synaptic responses. However, the mammillothalamic synaptic response after LFS did not correlate with the slow band of theta oscillation (low T-ratio), but did correlate positively with the fast band of theta oscillation (high T-ratio). Our data demonstrate that the descending direct fornix projection is a pathway that modulates theta rhythm in the hippocampo-diencephalic circuit, resulting in dynamic augmentation of thalamic neuronal responsiveness. These findings suggest that hippocampal theta differentially affects synaptic integration in the different structures with which the hippocampus is reciprocally connected.
Assuntos
Núcleos Anteriores do Tálamo/fisiologia , Hipocampo/fisiologia , Vias Neurais/fisiologia , Plasticidade Neuronal/fisiologia , Ritmo Teta/fisiologia , Animais , Eletrofisiologia , Potenciais Evocados/fisiologia , Masculino , RatosRESUMO
This study presents a new automatic spike sorting method based on feature extraction by Laplacian eigenmaps combined with k-means clustering. The performance of the proposed method was compared against previously reported algorithms such as principal component analysis (PCA) and amplitude-based feature extraction. Two types of classifier (namely k-means and classification expectation-maximization) were incorporated within the spike sorting algorithms, in order to find a suitable classifier for the feature sets. Simulated data sets and in-vivo tetrode multichannel recordings were employed to assess the performance of the spike sorting algorithms. The results show that the proposed algorithm yields significantly improved performance with mean sorting accuracy of 73% and sorting error of 10% compared to PCA which combined with k-means had a sorting accuracy of 58% and sorting error of 10%.A correction was made to this article on 22 February 2011. The spacing of the title was amended on the abstract page. No changes were made to the article PDF and the print version was unaffected.
Assuntos
Potenciais de Ação/fisiologia , Algoritmos , Modelos Neurológicos , Neurônios/fisiologia , Análise por Conglomerados , Bases de Dados Factuais , Análise de Componente PrincipalRESUMO
AIMS: Glioblastoma multiforme is the most common and most malignant adult brain tumour. Despite numerous advances in cancer therapy there has been little change in the prognosis of glioblastoma multiforme, which remains invariably fatal. We examined the Semliki Forest virus virus-like particle (SFV VLP) expression system encoding interleukin-12 (IL-12) as a therapeutic intervention against the syngeneic RG2 rat glioma model. METHODS: Glioma-bearing rats were treated with IL-12-encoding SFV VLPs via an implanted cannula. Animals were treated with 5 × 107 (low-dose) or 5 × 108 (high-dose) VLPs per treatment and the effect on glioma growth and survival was assessed. RESULTS: Low-dose treatment produced a 70% reduction in tumour volume, associated with a significant extension (20.45%) in survival that was dependent upon IL-12 expression. High-dose treatment resulted in an 87% reduction in tumour volume, related to the oncolytic capacity of the SFV VLP system. VLP delivery to the central nervous system (CNS) demonstrated the potential of the vector system to induce lethal pathology that was unrelated to replication-competent virus or high-level IL-12 expression. Treatment-related death was pronounced in high dose-treated animals and appeared to be the result of inflammation, necrosis and oedema at the inoculation site. CONCLUSION: The efficacy of an IL-12 gene therapy approach for the treatment of the RG2 glioma model has been demonstrated in addition to the oncolytic capacity of the VLP vector system. Despite this, the broad tropism of the SFV-based expression vector may limit use as a CNS gene therapy vector unless this inherent limitation can be overcome.
Assuntos
Neoplasias Encefálicas/terapia , Terapia Genética/métodos , Glioma/terapia , Vírus da Floresta de Semliki/genética , Animais , Neoplasias Encefálicas/patologia , Linhagem Celular Tumoral , Determinação de Ponto Final , Terapia Genética/mortalidade , Glioma/patologia , Interleucina-12/biossíntese , Interleucina-12/genética , Estimativa de Kaplan-Meier , Masculino , Transplante de Neoplasias , Ratos , Ratos Endogâmicos F344 , Técnicas Estereotáxicas , Replicação ViralRESUMO
The objectives of this research were to investigate the role played by the enzyme cyclooxygenase (COX) in learning and memory, synaptic plasticity and synaptic transmission in the rat brain in vivo. Male Wistar rats were treated with isoform-selective inhibitors for COX-1 and COX-2, either chronically and tested in the watermaze or acutely before electrophysiological recordings were made. We found a significant impairment in acquisition of the watermaze with inhibition of COX-2. Furthermore, we found COX-2 but not COX-1 inhibition significantly blocked long-term potentiation (LTP) induction but had no effect on already established LTP. Moreover, exogenous replacement of the main metabolite of COX-2 activity, PGE(2), was sufficient to restore LTP induction and for normal downstream signalling to ensue, namely extracellular signalling-regulated kinase (ERK)-phosphorylation and c-FOS expression. We conclude that endogenous basal levels of PGE(2) resulting from COX-2 but not COX-1 activity are necessary for synaptic plasticity and memory acquisition.
Assuntos
Ciclo-Oxigenase 2/metabolismo , Hipocampo/enzimologia , Aprendizagem/fisiologia , Potenciação de Longa Duração/fisiologia , Via Perfurante/enzimologia , Percepção Espacial/fisiologia , Animais , Ciclo-Oxigenase 1/efeitos dos fármacos , Ciclo-Oxigenase 1/metabolismo , Ciclo-Oxigenase 2/efeitos dos fármacos , Dinoprostona/metabolismo , Inibidores Enzimáticos/farmacologia , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Masculino , Aprendizagem em Labirinto/fisiologia , Proteínas de Membrana/efeitos dos fármacos , Proteínas de Membrana/metabolismo , Transtornos da Memória/enzimologia , Transtornos da Memória/fisiopatologia , Plasticidade Neuronal/fisiologia , Fosforilação , Proteínas Proto-Oncogênicas c-fos/metabolismo , Ratos , Ratos Wistar , Sinapses/enzimologia , Transmissão Sináptica/fisiologiaRESUMO
There is ongoing theoretical debate regarding episodic memory and how it can be accurately measured, in particular if the focus should be content-based recall of episodic details or something more experiential involving the subjective capacity to mentally travel back in time and "re-live" aspects of the original event. The autonoetic subscale of the Episodic Autobiographical Memory Interview (EAMI) is presented here as a new test instrument that attempts to redress theoretical and methodological shortcomings in autobiographical memory assessment. The EAMI merges a phenomenological detail-based approach with an assessment of autonoetic consciousness, departing considerably from traditional Remember/Know paradigms used within this field. We present findings from an initial pilot study investigating the potential markers of autonoetic consciousness that may accompany episodic retrieval. Key behavioural indices of autonoetic consciousness, notably those of viewer perspective, visual imagery, and emotional re-experiencing, emerged as being inextricably bound with the level of phenomenological detail recalled and the overall re-living judgment. The autonoetic subscale of the EAMI permits conceptually refined assessment of episodic personal memories and the accompanying subjective experience of mental re-living, characteristic of episodic memory.
Assuntos
Autobiografias como Assunto , Estado de Consciência , Memória , Autoimagem , Adolescente , Adulto , Feminino , Humanos , Imaginação , Entrevista Psicológica , Masculino , Rememoração Mental , Pessoa de Meia-Idade , Fatores SexuaisRESUMO
The ability of an organism to develop, maintain, and act upon an abstracted internal representation of spatially extensive environments can provide an increased chance in ensuring that organism's survival. Here, we propose a neurocognitive model of spatial representation describing how several different processes interact and segregate the differing types of information used to produce a unified cognitive map. This model proposes that view-based egocentric and vestibulomotor translational information are functionally and anatomically separate, and that these parallel systems result in independent, but interacting, models within a neurocognitive map of space. In this context, we selectively review relevant portions of the large literature, addressing the establishment and operation of such spatial constructs in humans and the brain systems that underpin them, with particular reference to the hippocampal formation (HF). We present a reinterpretation of the types of knowledge used in the formation of this spatial construct, the processes that act upon this information, the nature of the final spatial representation, and describe how these universal concepts relate to the proposed model of spatial processing. The relevant experimental paradigms used to examine the neural basis of spatial representation and the main findings from previous research are also briefly presented. Finally, we detail a series of testable theoretical, behavioral, and anatomical predictions made by the model.
Assuntos
Mapeamento Encefálico , Hipocampo/fisiologia , Modelos Neurológicos , Percepção Espacial/fisiologia , Hipocampo/citologia , Humanos , Vias NeuraisRESUMO
Neurodegeneration can produce behavioral impairments. Previously, we have found that inhibition of cyclooxygenase-2 activity or physical activity was neuroprotective during kainic-acid-induced neural loss. Here, we investigated the combined effect of exercise pre-insult and cyclooxygenase inhibitor treatment post-kainate-induced brain damage. However, in spite of an increase in BDNF levels, the combination did not improve behavioral performance in Morris watermaze and object exploration tasks.
Assuntos
Dano Encefálico Crônico/metabolismo , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Comportamento Exploratório/fisiologia , Aprendizagem em Labirinto/fisiologia , Condicionamento Físico Animal/fisiologia , Prostaglandina-Endoperóxido Sintases/metabolismo , Análise de Variância , Animais , Dano Encefálico Crônico/induzido quimicamente , Celecoxib , Ciclo-Oxigenase 2 , Inibidores de Ciclo-Oxigenase 2 , Inibidores de Ciclo-Oxigenase/farmacologia , Ácido Caínico , Masculino , Degeneração Neural/induzido quimicamente , Degeneração Neural/metabolismo , Prostaglandina-Endoperóxido Sintases/efeitos dos fármacos , Pirazóis/farmacologia , Ratos , Ratos Wistar , Sulfonamidas/farmacologiaRESUMO
Previous studies have suggested that exercise in a running wheel can be neuroprotective, perhaps due to, among others, gene-expression changes after exercise, increases in trophic proteins and/or enhanced cardiovascular responsivity. Here we ask whether physical exercise or environmental enrichment provide protection after brain damage, especially in terms of recovery of cognitive function. To evaluate the neuroprotective effect of these conditions, we used the kainic acid (KA) model of neuronal injury. Systemically-administered KA induces excitotoxicity by overstimulation of glutamate receptors, resulting in neuronal death by necrosis and apoptosis. Our results show that exercise, but not enriched environment, prior to KA-induced brain damage, improved behavioural performance in both Morris watermaze and object exploration tasks. However, prior exercise did not decrease to control levels the hyperactivity normally seen in KA-treated animals, as measured by ambulation in the open field. Furthermore, both exercise and enriched environment did not protect against neuron loss in CA1, CA2 and CA3 areas of the hippocampus, despite a substantial increase in brain-derived neutrophic factor (BDNF) levels in dentate gyrus of the exercise and KA-treated animals.
Assuntos
Fator Neurotrófico Derivado do Encéfalo/metabolismo , Meio Ambiente , Hipocampo/metabolismo , Aprendizagem/fisiologia , Neurônios/metabolismo , Condicionamento Físico Animal/fisiologia , Análise de Variância , Animais , Comportamento Exploratório/fisiologia , Hipocampo/efeitos dos fármacos , Hipocampo/patologia , Abrigo para Animais , Ácido Caínico , Masculino , Atividade Motora/fisiologia , Degeneração Neural/induzido quimicamente , Neurônios/efeitos dos fármacos , Neurônios/patologia , Neurotoxinas , Ratos , Ratos Wistar , Comportamento Espacial/fisiologiaRESUMO
Environmental enrichment promotes structural and functional changes in the brain, including enhanced learning and memory performance in rodents. Transient global cerebral ischemia (15 min) causes specific damage to dorsal hippocampal area CA1 pyramidal cells of the rat concomitantly with cognitive deficits. Thus, we investigated if environmental enrichment can protect rats against the cognitive and neurological consequences of transient ischemia. We evaluated the impairment of learning and memory with three tasks: odour discrimination, object exploration and spatial learning. Contrary to expectation, we found that the enriched environment improved performances for both ischemic and sham rats in odour discrimination and object exploration tasks compared with standard condition housed rats. After exposure to an enriched environment, ischemic rats performed better in the water maze than those in the standard housing conditions. However, exposure to an enriched environment does not protect against actual loss of CA1 pyramidal cells. Brain-derived neurotrophic factor (BDNF) levels were increased in environmental enrichment animals compared to those housed in standard conditions. We conclude that environmental enrichment has positive effects that are independent of the effects of ischemic brain lesions.
Assuntos
Fator Neurotrófico Derivado do Encéfalo/metabolismo , Transtornos Cognitivos/etiologia , Ataque Isquêmico Transitório/metabolismo , Ataque Isquêmico Transitório/fisiopatologia , Análise de Variância , Animais , Comportamento Animal , Transtornos Cognitivos/metabolismo , Aprendizagem por Discriminação/fisiologia , Meio Ambiente , Ensaio de Imunoadsorção Enzimática , Comportamento Exploratório/fisiologia , Hipocampo/patologia , Hipocampo/fisiopatologia , Masculino , Aprendizagem em Labirinto/fisiologia , Neurônios/metabolismo , Neurônios/fisiologia , Odorantes , Ratos , Ratos Wistar , Tempo de Reação/fisiologia , Fatores de TempoRESUMO
We have investigated the role of inflammation in the excitotoxicity induced by overstimulation of glutamate receptors using kainic acid, an important tool for studying functions related to excitatory amino acid transmission and for producing neuronal death, especially in areas CA1 and CA3 of the hippocampus. We hypothesised that by inhibiting one of the major components of the neuroinflammation response, after kainic acid injection, that there would be less inflammation and therefore a reduction in cell loss, an enhancement of cognitive function (using spatial learning and object exploration tasks) or both. We examined brain-derived neurotrophic factor levels, expecting that there would be a correlation between its level and subsequent recovery. Our results confirmed our hypothesis: the kainic acid injected-rats treated with celecoxib (after kainic injection) performed better in the spatial and non-spatial tasks than the kainic acid-treated group. However, there was not any improvement if celecoxib was given before kainic acid treatment, underlining also the importance of the production of prostaglandin at the beginning of inflammation.
Assuntos
Inibidores de Ciclo-Oxigenase/uso terapêutico , Doenças Neurodegenerativas/prevenção & controle , Recuperação de Função Fisiológica/efeitos dos fármacos , Sulfonamidas/uso terapêutico , Análise de Variância , Animais , Comportamento Animal , Fator Neurotrófico Derivado do Encéfalo/análise , Celecoxib , Sobrevivência Celular/efeitos dos fármacos , Inibidores de Ciclo-Oxigenase/farmacologia , Relação Dose-Resposta a Droga , Esquema de Medicação , Interações Medicamentosas , Ensaio de Imunoadsorção Enzimática/métodos , Reação de Fuga/efeitos dos fármacos , Comportamento Exploratório/efeitos dos fármacos , Hipocampo/citologia , Hipocampo/efeitos dos fármacos , Hipocampo/patologia , Ácido Caínico , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Atividade Motora/efeitos dos fármacos , Doenças Neurodegenerativas/induzido quimicamente , Neurônios , Desempenho Psicomotor/efeitos dos fármacos , Pirazóis , Ratos , Ratos Wistar , Tempo de Reação/efeitos dos fármacos , Convulsões/induzido quimicamente , Convulsões/tratamento farmacológico , Sulfonamidas/farmacologia , Fatores de TempoRESUMO
In this study, the authors investigate changes in the presynaptic terminal of the dentate gyrus that accompany 2 types of hippocampal-dependent plasticity: spatial learning and long-term potentiation (LTP). Parallel changes occurred in the dentate gyrus of rats that had undergone training in the Morris water maze and had sustained LTP. In both cases, KCl-induced brain-derived neurotrophic factor release was increased, and this was accompanied by increased phosphorylation of TrkB and the mitogen-activated protein kinase, ERK. Glutamate release was also enhanced, and the data suggest that this may be a consequence of increased activation of TrkB and ERK. Because the data indicate that similar cellular modifications are shared by these 2 forms of plasticity, they provide circumstantial evidence that LTP satisfies some of the requirements of a memory-inducing cellular substrate.
Assuntos
Fator Neurotrófico Derivado do Encéfalo/metabolismo , Giro Denteado/metabolismo , Aprendizagem/fisiologia , Potenciação de Longa Duração/fisiologia , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Receptor trkB/metabolismo , Animais , Fator Neurotrófico Derivado do Encéfalo/biossíntese , Fator Neurotrófico Derivado do Encéfalo/fisiologia , Masculino , Fosforilação , Ratos , Ratos Wistar , Transdução de Sinais/fisiologia , Comportamento Espacial/fisiologiaRESUMO
Several neurophysiological and computational theories of the rodent navigational system suggest that the differing cortices of the frontal lobe and thalamus share information and therefore undergo changes in synaptic strength. We examine here for the first time three forms of synaptic plasticity in the projection from the anterior thalamic nuclei to the anterior cingulate cortex: we demonstrate that this projection is capable of expressing paired-pulse facilitation, long-term potentiation, and short-term depression. Furthermore, input/output curves show that field excitatory post-synaptic potential amplitude increased at all stimulus intensities following high-frequency stimulation. These findings add important information to our understanding of synaptic plasticity in this important pathway, which has been widely hypothesized to play important roles in memory and spatial representation in the rodent.
Assuntos
Núcleos Anteriores do Tálamo/fisiologia , Potenciais Pós-Sinápticos Excitadores/fisiologia , Giro do Cíngulo/fisiologia , Potenciação de Longa Duração/fisiologia , Inibição Neural/fisiologia , Vias Neurais/fisiologia , Transmissão Sináptica/fisiologia , Animais , Núcleos Anteriores do Tálamo/citologia , Estimulação Elétrica , Giro do Cíngulo/citologia , Aprendizagem em Labirinto/fisiologia , Memória/fisiologia , Vias Neurais/citologia , Neurônios/fisiologia , Orientação/fisiologia , Ratos , Percepção Espacial/fisiologia , Sinapses/fisiologiaRESUMO
We investigated the effects of a single injection and a daily injection of lipopolysaccharide (LPS) on spatial learning and brain-derived neurotrophic factor (BDNF) expression in the rat dentate gyrus. LPS is derived from the cell wall of Gram-negative bacteria and is a potent endotoxin that causes the release of cytokines such as interleukin-1 and tumour necrosis factor. LPS is thought to activate both the neuroimmune and neuroendocrine systems; it also blocks long-term potentiation in the hippocampus. Here, we examined the effects of LPS on a form of hippocampal-dependent learning-spatial learning in the water maze. Rats were injected with LPS intraperitoneally (100 microg/kg) and trained in the water maze. The first group of rats were injected on day 1 of training, 4 h prior to learning the water maze task. Groups 2 and 3 were injected daily, again 4 h prior to the water-maze task; group 2 with LPS and group 3 with saline. A number of behavioural variables were recorded by a computerised tracking system for each trial. The behavioural results showed a single injection of LPS (group 1) impaired escape latency in both the acquisition and retention phases of the study, whereas a daily injection of LPS did not significantly impair acquisition or retention. BDNF expression was analysed in the dentate gyrus of all animals. No significant differences in BDNF expression were found between the three groups.
Assuntos
Fator Neurotrófico Derivado do Encéfalo/análise , Reação de Fuga/efeitos dos fármacos , Hipocampo/efeitos dos fármacos , Lipopolissacarídeos/farmacologia , Aprendizagem em Labirinto/efeitos dos fármacos , Orientação/efeitos dos fármacos , Animais , Mapeamento Encefálico , Giro Denteado/efeitos dos fármacos , Giro Denteado/patologia , Relação Dose-Resposta a Droga , Esquema de Medicação , Hipocampo/patologia , Injeções Intraperitoneais , Masculino , Ratos , Ratos WistarRESUMO
We review the neuroanatomical, neurophysiological and functional properties of the mammalian subiculum in this paper. The subiculum is a pivotal structure positioned between the hippocampus proper and entorhinal and other cortices, as well as a range of subcortical structures. It is an under-investigated region that plays a key role in the mediation of hippocampal-cortical interaction. We argue that on neuroanatomical, physiological and functional grounds, the subiculum is properly part of the hippocampal formation, given its pivotal role in the hippocampal circuit. We suggest that the term "subicular complex" embraces a heterogenous range of distinct structures and this phrase does not connote a functionally or anatomically meaningful grouping of structures. The subiculum has a range of electrophysiological and functional properties which are quite distinct from its input areas; given the widespread set of cortical and subcortical areas with which it interacts, it is able to influence activity in quite disparate brain regions. The rules which govern the plasticity of synaptic transmission are not well-specified; it shares some properties in common with the hippocampus proper, but behaves quite differently in other respects. Equally, its functional properties are not well-understood, it plays an important but ill-defined role both in spatial navigation and in mnemonic processing. The important challenges for the future revolve around the theoretical specification of its unique contribution to hippocampal formation processing on the one hand, and the experimental investigation of the many open questions (anatomical, physiological, pharmacological, functional) regarding its properties, on the other.
Assuntos
Hipocampo/citologia , Hipocampo/fisiologia , Vias Neurais/citologia , Vias Neurais/fisiologia , Neurônios/citologia , Neurônios/fisiologia , Potenciais de Ação/fisiologia , Animais , Comportamento Animal/fisiologia , Humanos , Aprendizagem/fisiologia , RatosRESUMO
Lipopolysaccharide is derived from the cell wall of gram-negative bacteria and is a potent endotoxin which causes the release of cytokines in the CNS. We examined the effect of lipopolysaccharide on synaptic transmission and synaptic plasticity in the hippocampal area CA1-subicular pathway in vivo. We found that lipopolysaccharide did not affect baseline synaptic transmission in this pathway; it did, however, reduce the magnitude of paired-pulse facilitation, a form of short-term plasticity thought to be primarily presynaptic in origin. We then examined the interaction between lipopolysaccharide and two common models for the biological basis of memory: high-frequency stimulation induced long-term potentiation and low-frequency stimulation induced long-term depression of synaptic transmission. We found that lipopolysaccharide blocked long-term potentiation following high-frequency stimulation and also induced potentiation of synaptic transmission after low-frequency stimulation. Lipolysaccharide blocked paired-pulse facilitation selectively at short rather than longer interstimulus intervals. Thus, lipopolysaccharide has different effects on synaptic transmission in this pathway depending on the frequency and length of stimulation. These results provide new insights into the action of lipopolysaccharide on various forms of plasticity in the hippocampus, an area known to play a vital role in learning and memory.
Assuntos
Hipocampo/efeitos dos fármacos , Lipopolissacarídeos/farmacologia , Vias Neurais/efeitos dos fármacos , Plasticidade Neuronal/efeitos dos fármacos , Transmissão Sináptica/efeitos dos fármacos , Animais , Estimulação Elétrica/métodos , Eletrodos Implantados , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Potenciais Pós-Sinápticos Excitadores/fisiologia , Hipocampo/fisiologia , Potenciação de Longa Duração/efeitos dos fármacos , Masculino , Vias Neurais/fisiologia , Plasticidade Neuronal/fisiologia , Ratos , Ratos Wistar , Tempo de Reação/efeitos dos fármacos , Transmissão Sináptica/fisiologiaRESUMO
Using assays based on the inhibition of restriction enzyme cleavage of plasmid and synthetic DNA, the complex (2-amino-2-methyl-3-butanone oxime)dichloroplatinum(II), [PtCl2(ambo)], has been shown to have an increased tendency for binding to adenine-rich sequences when compared to cis[PtCl2(NH3)2] (cisplatin). [PtCl2(ambo)] was found to form substantially fewer interstrand adducts than does cisplatin. The in vitro cytotoxicity of [PtCl2(ambo)] against a human bladder cancer cell line was determined and found to be more than two orders of magnitude lower than that of cisplatin, yet it was also found to be equally effective at passing into cells and binding to isolated DNA.
Assuntos
Adenina/metabolismo , Antineoplásicos/metabolismo , DNA/efeitos dos fármacos , Compostos Organoplatínicos/metabolismo , Animais , Antineoplásicos/química , Antineoplásicos/farmacologia , Sequência de Bases , Bovinos , DNA/química , DNA/metabolismo , Desenho de Fármacos , Ensaios de Seleção de Medicamentos Antitumorais , Humanos , Dados de Sequência Molecular , Compostos Organoplatínicos/química , Compostos Organoplatínicos/farmacologia , Células Tumorais CultivadasRESUMO
There has been little electrophysiological examination of the afferent projection from lateral entorhinal cortex to dorsal subiculum. Here we provide evidence that synaptic inputs from lateral entorhinal cortex and CA1 converge onto single dorsal subicular neurons in vivo. Subicular responses to CA1 stimulation consisted of excitation and/or long-duration inhibition. Neurons excited by CA1 activation usually showed inhibition to entorhinal stimulation. The latter inhibition was usually of short duration, however, long duration inhibition was seen in a significant proportion of responses. Entorhinal stimulation produced excitatory responses in four bursting cells and it was these cells that also tended to show the longest inhibition. Only bursting cells could be driven antidromically by entorhinal stimulation. Biocytin-filled multipolar and pyramidal cells displayed excitation-inhibition sequences to CA1 and inhibition to entorhinal stimulation. These data strongly suggest that subicular inhibitory neurons receive excitatory input from CA1 and display mutual inhibition. The source of entorhinal-evoked inhibition is less clear. The relative sparseness of observed entorhinal-evoked responses suggests that the input to dorsal subiculum from any one part of lateral entorhinal cortex is spatially restricted. These data show that excitation-inhibition sequences can be seen in subicular pyramidal and multipolar cells and that single subicular neurons receive convergent inputs from CA1 and entorhinal cortex. We show for the first time that bursting cells can be driven both orthodromically and antidromically by direct entorhinal stimulation. These data support the existence of a reciprocal excitatory connection between lateral entorhinal cortex and dorsal subiculum and suggest further that this connection may involve only bursting subicular neurons.