Neurobiology of disease
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Neurobiology of disease · Mar 2010
Kindling as a model of temporal lobe epilepsy induces bilateral changes in spontaneous striatal activity.
Basal ganglia are engaged in seizure propagation, control of seizures, and in epilepsy-induced neuroplasticity. Here, we tested the hypothesis that previously observed histological and neurochemical changes in the striatum of amygdala-kindled rats as a model of temporal lobe epilepsy are reflected in alterations of spontaneous striatal firing rates and patterns. Because experimental histological and clinical imaging studies indicated a bilateral involvement of the striatum in epilepsy-induced neuroplasticity, in vivo single-unit recordings were done bilaterally 1 day after a kindled seizure in rats kindled via the right amygdala. ⋯ The changes are probably caused by a combination of several factors including disturbed bilateral limbic and neocortical input as well as disturbed intrastriatal GABAergic function. The changes reflect a pathophysiological state predisposing the brain to epileptic discharge propagation or else (contralateral striatum) could represent a compensatory network of inhibitory circuits activated to prevent the propagation of seizure activity. The findings are relevant for a better understanding of kindling-induced network changes and might provide new targets for therapeutic manipulations in epilepsies.
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Neurobiology of disease · Mar 2010
Chronic expression of low levels of tumor necrosis factor-alpha in the substantia nigra elicits progressive neurodegeneration, delayed motor symptoms and microglia/macrophage activation.
Inflammation, and in particular microglia activation, is regarded as a constant component of brain pathology in Parkinson's disease (PD). Microglial activation has been found in the substantia nigra (SN), one of the main brain regions affected in PD, for many years after the initiation of the disease. Although many studies point towards a deleterious role of inflammation on PD, the functional role of many of its main components has not been clarified yet. ⋯ Thus, we conclude that extended duration of the expression of TNF-alpha is necessary and sufficient for a univocal toxic effect of TNF-alpha on dopaminergic neurons and motor disabilities. This study provides an animal model to study early events that lead to TNF-alpha-mediated neuronal demise in the SN. In addition, the cellular components of the inflammation elicited by TNF-alpha and the lack of IL-1beta expression support the growing idea of a distinct cytokine network in the brain.
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Neurobiology of disease · Mar 2010
Seizures in the developing brain result in a long-lasting decrease in GABA(B) inhibitory postsynaptic currents in the rat hippocampus.
Whether seizures in the developing brain cause long-term changes in the mature brain has been debated. We tested the hypothesis that a model of early-life seizures, induced by systemic injection of a GABA(B) receptor antagonist CGP56999A in immature rats, decreased GABA(B) receptor-mediated inhibitory postsynaptic currents (IPSCs) in the hippocampus of adolescent rats. Whole-cell recordings were made in CA1 pyramidal cells and dentate gyrus (DG) granule cells in vitro, 30-45 days after the rats had seizures induced by CGP56999A (1-1.5 mg/kg i.p.) or control saline injection on postnatal day 15. ⋯ Additionally, hippocampal neurons of early-life seizure rats, as compared to those in control rats, showed a more depolarized resting membrane potential in both CA1 and DG, and a larger input resistance but reduced spike frequency adaptation in DG neurons. In conclusion, early-life seizures result in a long-lasting reduction in GABA(B) receptor-mediated transmission in DG principal neurons and depolarization in CA1 and DG principal neurons. These alterations are expected to increase seizure susceptibility in the adult brain.