RESUMEN

INTRODUCTION: Dendritic spines are the main sites of excitatory synaptic contacts. Moreover, they present plastic responses to different stimuli present in synaptic activity or damage, ranging from an increase or decrease in their total number, to redistribution of progenitor dendritic spines, to variations in their size or shape. However, the spines can remain stable for a long time. BACKGROUND: The use of experimental models has shown that different molecules of the F-actin binding and signalling pathways are closely related to the development, maintenance and plasticity of excitatory synapses, which could affect the number, size and shape of the dendritic spines; these mechanisms affect and depend on the reorganisation of the actin cytoskeleton. DEVELOPMENT: It is proposed that the filopodia are precursors of dendritic spines. Drebrin is an F-actin binding protein, and it is responsible for concentrating F-actin and PSD-95 in filopodia that will guide the formation of the new spines. CONCLUSION: The specific mechanisms of actin regulation are an integral part in the formation, maturing process and plasticity of dendritic spines in association with the various actin cytoskeleton-binding proteins The signalling pathways mediated by small GTPases and the equilibrium between G-actin and F-actin are also involved.

Asunto(s)

Espinas Dendríticas/fisiología , Proteínas de Microfilamentos/fisiología , Transducción de Señal/fisiología , Encéfalo/citología , Encéfalo/fisiología , Citoesqueleto/fisiología , Espinas Dendríticas/ultraestructura , Humanos , Proteínas de Microfilamentos/genética , Neurogénesis/genética , Neurogénesis/fisiología , Seudópodos/fisiología , Seudópodos/ultraestructura , Transducción de Señal/genética

RESUMEN

Experimental paradigms conducted to assess the neurotoxic effects of ethanol exposure on hippocampus development have yielded controversial findings. Hippocampal CA1 population and some cytoarchitectural parameters of pyramidal cells were studied after exposure to ethanol during early development, in rats. Examination of 30-day-old offspring of rats exposed to moderate levels of ethanol during gestation through lactation showed an increased volume of the hippocampal CA1 field compared to untreated or pair-fed control pups, as well as a reduced number of pyramidal neurons. In addition, the number of spines from surviving CA1 pyramidal neurons was reduced. Furthermore, stubby and wide spines were proportionally increased, while the proportion of mushroom and ramified spines was reduced; no variation in the proportion of thin spines was observed. Because alcoholic women usually drink alcohol before, during, and after pregnancy, a broad-range experimental model of alcohol exposure was used in this study. The present findings show that experimental exposure to moderate levels of ethanol, resembling the human situation in alcoholic mothers, leads to loss of hippocampal CA1 pyramidal neurons, along with several pathological and plastic events in the dendritic arborization of these neurons. Some ethanol-induced excitotoxicity-related mechanisms, which may be underlying these effects, are discussed.

Asunto(s)

Animales Recién Nacidos/fisiología , Depresores del Sistema Nervioso Central/toxicidad , Etanol/toxicidad , Hipocampo/patología , Animales , Peso Corporal/efectos de los fármacos , Muerte Celular/efectos de los fármacos , Femenino , Tamaño de la Camada/efectos de los fármacos , Masculino , Plasticidad Neuronal/efectos de los fármacos , Tamaño de los Órganos/efectos de los fármacos , Embarazo , Efectos Tardíos de la Exposición Prenatal , Ratas , Ratas Sprague-Dawley , Sobrevida

RESUMEN

Sprague-Dawley male rats, fed with a tryptophan-deficient and 8% protein corn-based diet were compared with a group of animals fed with 8% protein alone, and with a group fed with Chow Purina containing 23% protein. Retardation of Bergmann glial cell maturation and a concomitant retardation in granule cell migration were observed in the corn-fed group at 21 days. At 30 days of age, the dendrites of granule cells of both hypoproteic and corn-fed groups were larger than those of the Chow-fed animals. At 60 days of age, dendritic arborization of Purkinje cells was more profuse in both the hypoproteic and corn-fed rats compared with the Chow-fed group. This retardation in granule cell migration could be partially due to Bergmann glial cell immaturity. Consequently, several plastic and maybe compensatory events in both granule and Purkinje cells could have occurred, due to tryptophan deficiency resulting from the corn-based diet.

Asunto(s)

Corteza Cerebelosa/patología , Plasticidad Neuronal/efectos de los fármacos , Trastornos Nutricionales/fisiopatología , Proteínas de Plantas/química , Complicaciones del Embarazo/fisiopatología , Efectos Tardíos de la Exposición Prenatal , Proteínas , Triptófano/deficiencia , Zea mays , Alimentación Animal/análisis , Animales , Peso al Nacer , Peso Corporal , Corteza Cerebelosa/embriología , Dendritas/ultraestructura , Desarrollo Embrionario y Fetal , Femenino , Masculino , Neuroglía/patología , Embarazo , Deficiencia de Proteína/fisiopatología , Células de Purkinje/ultraestructura , Ratas , Ratas Sprague-Dawley , Serotonina/biosíntesis , Zea mays/química

RESUMEN

Monosodium glutamate was administered subcutaneously to male neonate rats, and the effects on cell number and cytoarchitecture of third-layer pyramidal neurons from the prefrontal cerebral cortex were studied in the adult. Monosodium glutamate treatment (4 mg/g of body weight, on post-natal days 1, 3, 5 and 7) resulted in fewer neurons, and shorter and less ramified dendritic processes, than those observed in control animals. Both density and proportional shapes of dendritic spines were not modified. We propose a dual effect of neonatal exposure to glutamate: an excitotoxic effect leading to cell death, and; a secondary neuroprotective effect, arising from the proliferation of glial cells and their subsequent uptake of glutamate, that favors the survival of the remaining neurons, and leads to a further hypotrophic effect on their dendritic processes.

Asunto(s)

Muerte Celular/efectos de los fármacos , Dendritas/patología , Aditivos Alimentarios/farmacología , Corteza Prefrontal/efectos de los fármacos , Células Piramidales/patología , Glutamato de Sodio/farmacología , Animales , Animales Recién Nacidos , Tamaño de la Célula/efectos de los fármacos , Dendritas/efectos de los fármacos , Masculino , Neurotoxinas/farmacología , Corteza Prefrontal/patología , Células Piramidales/efectos de los fármacos , Células Piramidales/ultraestructura , Ratas , Ratas Wistar

RESUMEN

The prefrontal cortex activity is involved in organizing the short-term memory. Although the involvement of serotonin for an appropriate performance in learning and memory tests is well known, its role is still unclear; as is the cellular basis of short-term memory behavioral performance. Sprague-Dawley rats were stereotactically injected with 1 microg/microl of 5, 7-dihydroxitryptamine to cause a lesion to the dorsal raphe nucleus. Sham-operated or intact rats were also studied as control groups. Before surgery and 20 days post-operatively, each animal was placed in the Biel maze for five consecutive trials. In the pre-treatment test, all three groups decreased significantly the number of errors beginning with the fourth trial. The same occurred in the post-treatment test, except for the experimental group, whose animals committed less errors beginning with the second trial. After behavioral testing, the dorsomedial prefrontal cerebral cortex was dissected out, and the Golgi study of the third-layer pyramidal neurons revealed that the length of both the apical and the basilar dendrites was smaller than that of controls, and that the apical and oblique dendrites had a greater spine density. A major proportion of thin spines was also seen on the basilar and oblique dendrites, and more stubby spines were seen on the apical dendrite. Serotonin depletion in the prefrontal cerebral cortex resulted in cytoarchitectural alterations of the prefrontocortical pyramidal neurons, which may be underlying partially the greater efficiency observed in the short-term memory behavioral performance.

Asunto(s)

Memoria a Corto Plazo/fisiología , Corteza Prefrontal/metabolismo , Células Piramidales/fisiología , Serotonina/metabolismo , Animales , Conducta Animal/fisiología , Dendritas/fisiología , Disección , Femenino , Aprendizaje por Laberinto/fisiología , Plasticidad Neuronal , Corteza Prefrontal/citología , Corteza Prefrontal/cirugía , Células Piramidales/citología , Núcleos del Rafe/efectos de los fármacos , Núcleos del Rafe/patología , Núcleos del Rafe/fisiopatología , Ratas , Ratas Sprague-Dawley

RESUMEN

The CA1 hippocampal region is involved in organizing several neuropsychological processes. Pyramidal cell dendritic spines in the CA1 field of rats subjected to chronic tryptophan diet restriction were quantified at 21, 40, and 60 days of age. At 40 days of age, the number of spines in the distal third of the apical dendrite was smaller in experimental animais. The same was true for the medial third of the apical dendrite and the basal dendrite at 60 days of age. The results could be interpreted as a trans-synaptic plastic response due to understimulation of serotoninergic receptors located in the hippocampal Ammon's horn and, particularly, on the CA1 pyramidal neurons as well as on aferences to the hippocampus. Since the present is a model of generalized tryptophan restriction, neurochemical studies are needed to dilucidate this hypothesis.