RESUMEN
Injection of kainic acid into the cerebellum leads to a neuroexcitatory and neurotoxic effect on neurons connected with cerebellar granule cells. Observation of the activities of dehydrogenases taking part in glucose metabolism and glutamate dehydrogenase shows that Purkinje cells undergo a rapid destruction. Lesions of small stellate cells come later. But the basket cells present a long period of hyperactivity revealed by an increase of dehydrogenase activity.
Asunto(s)
Cerebelo/efectos de los fármacos , Ácido Kaínico/farmacología , Neuronas/efectos de los fármacos , Pirrolidinas/farmacología , Animales , Cerebelo/enzimología , Histocitoquímica , Neuronas/enzimología , Oxidorreductasas/metabolismo , Células de Purkinje/efectos de los fármacos , Ratas , Ratas EndogámicasRESUMEN
In former investigations on human focal epilepsy and on experimental epilepsy by cobalt implantation, the authors have demonstrated the signaletic importance of "activated astrocytes": cortical astrocytes endowed with a modified metabolism and an accelerated turnover. The present study concerns the results of the intra-amygdaloid injections of kainic acid, a strong excitatory and neurotoxic amino acid. Injections in semi-chronic conditions in the rat lead to electrical and motor seizures and to the production of activated astrocytes not only in regions that might trigger off epileptic seizures (cerebral cortex, amygdala, possibly hippocampus), but also in the neostriatum. Stimulation of this last region results in a Huntington chorea-like syndrome. Thus, the importance of activated astrocytes must be extended to include other conditions of intense hyperactivity of neurons than epilepsy.
Asunto(s)
Encéfalo/patología , Epilepsia/patología , Neuronas/patología , Animales , Astrocitos/patología , Electroencefalografía , Epilepsia/inducido químicamente , Ácido Kaínico , Ratas , Ratas EndogámicasAsunto(s)
Astrocitos/metabolismo , Epilepsia del Lóbulo Temporal/metabolismo , Ácido Kaínico/farmacología , Oxidorreductasas/metabolismo , Pirrolidinas/farmacología , Retina/efectos de los fármacos , Animales , Hipocampo/efectos de los fármacos , Histocitoquímica , Ratas , Ratas Endogámicas , Telencéfalo/efectos de los fármacosAsunto(s)
Sistema Nervioso/anatomía & histología , Neuroanatomía/historia , Animales , Encéfalo/anatomía & histología , Historia del Siglo XIX , Humanos , Regeneración Nerviosa , Neuronas/citología , Publicaciones Periódicas como Asunto/historia , Nervios Periféricos/anatomía & histología , Médula Espinal/anatomía & histologíaRESUMEN
Production of an epileptogenic focus by cobalt-gelatin implantation in the cerebral cortex of the rat determines a local increase of cytochrome oxidase activity in neurones and probably a decrease of its activity in neuroglia. This variation of oxidative metabolism is not characteristic of the "epileptic neuron" since it takes also place after non irritative lesions, though remaining less conspicuous and less extensive.
Asunto(s)
Corteza Cerebral/enzimología , Complejo IV de Transporte de Electrones/metabolismo , Epilepsias Parciales/enzimología , Animales , Encefalopatías/enzimología , Neuroglía/enzimología , Neuronas/enzimología , RatasRESUMEN
Investigation of the localization in the central nervous system of the rat of an epileptogenic agent, methylseleno-2-benzoic acid, did not lead to its selective distribution in the cerebral cortex or in the brainstem in relation with its biological activity. But a systematic study of the distribution of this compound labelled with 75Se at a high specific activity has revealed a rate of fixation by the pineal gland 4 to 5 times higher than that of other tissues of the central nervous system. After a survival time of 4 hours, the radioactivity of the pineal gland exceeds that of the blood. A parallel study of the distribution of the 75SeO3- ion on the one hand of the 35S homolog of the 75Se compound on the other hand has demonstrated that the fixation by the pineal gland is bound to the molecular structure of the selenium compound.
Asunto(s)
Benzoatos/metabolismo , Compuestos de Organoselenio , Glándula Pineal/metabolismo , Selenio/metabolismo , Animales , Encéfalo/metabolismo , Corteza Cerebral/metabolismo , Cinética , Especificidad de Órganos , Hipófisis/metabolismo , RatasRESUMEN
A previous study showed a strong relationship between human focal epilepsy and the presence in the cortex of "activated" astrocytes characterized by an intense activity of dehydrogenases (DH) involved in glucose metabolism and of glutamate DH. Using the semi-chronic model of cobalt-induced experimental focal epilepsy in the rat, we investigated a possible correlation between astrocyte modifications and the chronological development of the epileptic manifestations on the ECoG. After a few days the cobalt-implanted rats present spikes, then sharp waves followed by an electrical crisis and ultimately motor seizures. Activated astrocytes were found in each phase of this evolution. Their number increases with the intensity of the manifestations. There is a close relationship between activated astrocytes and focal epileptic phenomena. At this stage of our study it is clear that the presence of activated astrocytes is not a consequence of seizures. However, it is impossible to say whether the activation is secondary to the hyperactivity of the neurons or directly responsible for the constitution of the epileptic focus. In any case, activated astrocytes provide a new means of localizing an epileptogenic focus.
Asunto(s)
Astrocitos/enzimología , Cobalto , Epilepsias Parciales/inducido químicamente , Oxidorreductasas/análisis , Lóbulo Parietal/efectos de los fármacos , Animales , Astrocitos/fisiología , Electroencefalografía , Epilepsias Parciales/enzimología , Epilepsias Parciales/fisiopatología , Glucosafosfato Deshidrogenasa/análisis , Glutamato Deshidrogenasa/análisis , Histocitoquímica , Isoenzimas/análisis , L-Lactato Deshidrogenasa/análisis , Masculino , Lóbulo Parietal/fisiopatología , Ratas , Succinato Deshidrogenasa/análisisRESUMEN
Implantation of cobalt powder in the cerebral cortex of rat determines an epileptogenic focus where two types of reactive astrocytes are observed. The first type is mostly represented in the subcortical white matter but it does exist in the cortex around the implant. Phosphorylase and branching enzyme are both very active in these cells which are filled with glycogen. The second type is limited to the cortex and phosphorylase activity leads to an unbranched polysaccharid. These cells correspond to the "activated astrocytes" described by the authors in a previous paper and observed round irritative lesions which, in the cerebral cortex, produce epileptogenic foci.
Asunto(s)
Enzima Ramificadora de 1,4-alfa-Glucano/análisis , Astrocitos/enzimología , Glucosiltransferasas/análisis , Fosforilasas/análisis , Enzima Ramificadora de 1,4-alfa-Glucano/metabolismo , Animales , Astrocitos/patología , Corteza Cerebral/enzimología , Corteza Cerebral/patología , Cobalto , Glucógeno/biosíntesis , Histocitoquímica , Masculino , Fosforilasas/metabolismo , Ratas , Convulsiones/inducido químicamente , Convulsiones/enzimología , Convulsiones/patologíaRESUMEN
A semi-chronic model of cobalt-induced experimental epilepsy in the rat was used to investigate the action of two classic anticonvulsant drugs, phenytoin and ethosuximide. Single injections of ethosuximide lead to an inhibition of the epileptic discharges. We failed to demonstrate an inhibitory effect of phenytoin after preventive administration. The carbidopa-L-dopa association was investigated owing to the inhibitory effects of dopamine and its presence in the cortex. We showed that a dose of 100 mg/kg of L-dopa combined with 25 mg/kg of carbidopa is necessary and sufficient to produce an almost complete inhibition of the discharges.
Asunto(s)
Carbidopa/farmacología , Cobalto/farmacología , Etosuximida/farmacología , Hidrazinas/farmacología , Levodopa/farmacología , Fenitoína/farmacología , Convulsiones/fisiopatología , Animales , Relación Dosis-Respuesta a Droga , Interacciones Farmacológicas , Electroencefalografía , Masculino , Ratas , Convulsiones/inducido químicamenteRESUMEN
Injection of 3-acetylpyridine at a LD50 dose to albino rats produces in a few days the destruction of olivary neurons. But the caudal part of the olivary complex, particularly accessory olives, escapes the destruction by this antimetabolite of nicotinamide. Nicotinamide protects olives agains 3-acetylpyridine. However, a preliminary histoenzymological study of dehydrogenases demanding a coenzyme derived from nicotinamide has given no significant results. The authors invoke the necessity of a rostro-caudal systematization of the olivary complex, based on fine structure, connnections and metabolism of neurons.
Asunto(s)
Núcleo Olivar/citología , Animales , Recuento de Células , Niacinamida/farmacología , Núcleo Olivar/efectos de los fármacos , Piridinas/antagonistas & inhibidores , Piridinas/farmacología , RatasRESUMEN
Investigation of astrocytes in the pyramidal tract of the rat 2 to 100 days after a lesion of the motor cortex indicates that the glial reaction, with increase in size of astrocytes and in affinity for Cajal's gold-sublimate, begins at the lesion and extends to the distal segments of the spinal cord. But this reaction recedes and disappears in lumbar and dorsal cord about 70 days after the operation. It persists in the cervical cord and in the brain. On the other hand, a characteristic increase in activity of glutamate andglucose-6-phosphate dehydrogenases is restricted to the vicinity of the lesion and does not even encroach upon the posterior limb of the internal capsule.