RESUMEN
To assess the therapeutic potential of brain-derived neurotrophic factor (BDNF) in clinics, we extensively investigated the effects of BDNF on adult motor neurons in a rat spinal root avulsion model. Intrathecal administration of BDNF immediately after the spinal root avulsion greatly protected against the motor neuron cell death. BDNF also showed a protective effect on the atrophy of soma and on the reduction of transmitter-related enzymes such as choline acetyl transferase and acetylcholine esterase. Very interestingly, BDNF induced axonal outgrowth of severely damaged motor neurons at the avulsion site. The BDNF administration following 2-week treatment with phosphate-buffered saline after avulsion prevented further augmentation of cell death and reversed cholinergic transmitter-related enzyme deficiency. BDNF was demonstrated to possess a wide variety of biological effects on survival, soma size, cholinergic enzymes, and axonal outgrowth of adult motor neurons. These results provide a rationale for BDNF treatment in motor neuron diseases such as spinal cord injury and amyotrophic lateral sclerosis.
Asunto(s)
Axones/efectos de los fármacos , Factor Neurotrófico Derivado del Encéfalo/uso terapéutico , Ganglios Espinales/lesiones , Neuronas Motoras/efectos de los fármacos , Fármacos Neuroprotectores/uso terapéutico , Degeneración Retrógrada/efectos de los fármacos , Raíces Nerviosas Espinales/lesiones , Acetilcolinesterasa/análisis , Animales , Factor Neurotrófico Derivado del Encéfalo/administración & dosificación , Factor Neurotrófico Derivado del Encéfalo/farmacología , Muerte Celular , Colina O-Acetiltransferasa/análisis , Esquema de Medicación , Ganglios Espinales/patología , Infusiones Parenterales , Masculino , Neuronas Motoras/patología , Proteínas del Tejido Nervioso/análisis , Fármacos Neuroprotectores/administración & dosificación , Fármacos Neuroprotectores/farmacología , Ratas , Ratas Wistar , Médula Espinal/patología , Raíces Nerviosas Espinales/patología , Espacio SubaracnoideoRESUMEN
Glial cell line-derived neurotrophic factor (GDNF) and transforming growth factor beta 3 (TGF-beta 3) are members of the TGF-beta superfamily with high neurotrophic activity on cultured nigral dopamine neurons. We investigated the effects of intracerebral administration of GDNF and TGF-beta 3 on the delayed cell death of the dopamine neurons in the rat substantia nigra following 6-hydroxydopamine lesions of dopaminergic terminals in the striatum. Fluorescent retrograde tracer injections and tyrosine hydroxylase immunocytochemistry demonstrated nigral degeneration with an onset 1 week after lesion, leading to extensive death of nigral neurons 4 weeks postlesion. Administration of recombinant human GDNF for 4 weeks over the substantia nigra at a cumulative dose of 140 micrograms, starting on the day of lesion, completely prevented nigral cell death and atrophy, while a single injection of 10 micrograms 1 week postlesion had a partially protective effect. Continuous administration of TGF-beta 3, starting on the day of lesion surgery, did not affect nigral cell death or atrophy. These findings support the notion that GDNF, but not TGF-beta 3, is a potent neurotrophic factor for nigral dopamine neurons in vivo.
Asunto(s)
Fibras Adrenérgicas/efectos de los fármacos , Cuerpo Estriado/efectos de los fármacos , Factores de Crecimiento Nervioso/farmacología , Proteínas del Tejido Nervioso/farmacología , Oxidopamina/farmacología , Degeneración Retrógrada/efectos de los fármacos , Sustancia Negra/efectos de los fármacos , Factor de Crecimiento Transformador beta/farmacología , Fibras Adrenérgicas/patología , Animales , Cuerpo Estriado/cirugía , Dopamina/metabolismo , Femenino , Factor Neurotrófico Derivado de la Línea Celular Glial , Histocitoquímica , Neuronas/efectos de los fármacos , Neuronas/patología , Ratas , Ratas Sprague-Dawley , Sustancia Negra/patologíaRESUMEN
Multiple genetic and epigenetic events determine neuronal phenotype during nervous system development. After the mature mammalian neuronal phenotype has been determined it is usually static for the remainder of life, unless an injury or degenerative event occurs. Injured neurons may suffer one of three potential fates: death, persistent atrophy, or recovery. The ability of an injured adult neuron to recover from injury in adulthood may be determined by events that also influence neuronal phenotype during development, including expression of growth-related genes and responsiveness to survival and growth signals in the environment. The latter signals include neurotrophic factors and substrate molecules that promote neurite growth. Several adult CNS regions exhibit neurotrophic-factor responsiveness, including the basal forebrain, entorhinal cortex, hippocampus, thalamus, brainstem, and spinal cord. The specificity of neurotrophic-factor responsiveness in these regions parallels patterns observed during development. In addition, neurons of several CNS regions extend neurites after injury when presented with growth-promoting substrates. When both neurotrophic factors and growth-promoting substrates are provided to adult rats that have undergone bilateral fimbria-fornix lesions, then partial morphological and behavioral recovery can be induced. Gene therapy is one useful tool for providing these substances. Thus, the mature CNS remains robustly responsive to signals that shape nervous system development, and is highly plastic when stimulated by appropriate cues.
Asunto(s)
Lesiones Encefálicas/fisiopatología , Trasplante de Tejido Encefálico , Trasplante de Tejido Fetal , Terapia Genética , Factores de Crecimiento Nervioso/fisiología , Neuronas/fisiología , Animales , Lesiones Encefálicas/terapia , Células Cultivadas/trasplante , Fibras Colinérgicas/fisiología , Terapia Combinada , Fibroblastos/metabolismo , Fibroblastos/trasplante , Sustancias de Crecimiento/uso terapéutico , Hipocampo/embriología , Hipocampo/trasplante , Macaca fascicularis , Macaca mulatta , Factores de Crecimiento Nervioso/administración & dosificación , Factores de Crecimiento Nervioso/genética , Regeneración Nerviosa/efectos de los fármacos , Fenotipo , Ratas , Proteínas Recombinantes de Fusión/biosíntesis , Proteínas Recombinantes de Fusión/metabolismo , Degeneración Retrógrada/efectos de los fármacos , Tabique Pelúcido/lesiones , Traumatismos de la Médula Espinal/fisiopatología , Traumatismos de la Médula Espinal/terapia , TransgenesRESUMEN
The retrograde changes induced by an excitotoxic lesion of the striatum (Str) on the neurons in substantia nigra pars compacta (SNc) projecting to the neuron-depleted region were investigated in adult rats. The retrograde tracer Fluoro-Gold (FG) was injected bilaterally into the Str. 2 weeks later, the excitotoxic amino acid ibotenic acid (IA) was injected unilaterally into the same structure. At four different time points after the lesion (1 week and 1, 2 and 3 months, respectively), the size of the FG-labelled cells and number of tyrosine hydroxylase (TH)-positive cells in the SNc were evaluated on the lesioned and control sides. Parallel groups of animals received suspension grafts of fetal striatal tissue into the lesioned striata. At 1 week and 1 month after lesion, there were no changes in cell size, number of TH-positive cells or number of FG-labelled cells expressing TH at the SNc. At 2 and 3 months, however, there was a significant 30% shrinkage of the FG-labelled SNc cells but no evident decrease in TH-positive cell number, or in the expression of the TH protein, on the lesioned side as compared with the non-lesioned control side. Striatal transplants placed into the lesioned Str did not counteract this effect. This finding that an axon-sparing lesion of target cells results in cell shrinkage but no cell loss of the neurons that project to the lesioned area is in line with what has been shown to occur after similar lesions in the cholinergic septohippocampal and basalo-cortical systems.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Ácido Iboténico/toxicidad , Neostriado/efectos de los fármacos , Degeneración Retrógrada/efectos de los fármacos , Estilbamidinas , Sustancia Negra/ultraestructura , Animales , Trasplante de Tejido Encefálico/fisiología , Femenino , Trasplante de Tejido Fetal/fisiología , Colorantes Fluorescentes , Inmunohistoquímica , Ratas , Ratas Sprague-Dawley , Sustancia Negra/efectos de los fármacos , Sustancia Negra/enzimología , Tirosina 3-Monooxigenasa/inmunología , Tirosina 3-Monooxigenasa/metabolismoRESUMEN
1. The alterations of voltage-sensitive calcium currents produced in thalamic cells by injury were investigated under voltage clamp using patch-clamp recordings in the whole-cell configuration. 2. One day after unilateral cortical ablation in immature rats (postnatal day 7), low-threshold transient calcium (T) currents in acutely isolated thalamic relay neurons (RNs) were increased by 68% compared with contralateral controls (P < 0.001). Three days after the operation, T currents in injured neurons were at 44% of control levels (P < 0.001). On the other hand, high-threshold (L) calcium currents in RNs did not change over the same interval. 3. To investigate the mechanism for the increase of T current, both kinetics and voltage dependency of activation and inactivation were examined. At a test voltage of -40 mV, the activation time constant decreased from 4.1 to 3.2 ms (P < 0.05); however, this small change was insufficient to explain the large increase in T current. Time constants for both fast and slow inactivation did not change significantly, nor did voltage dependence of activation or inactivation of thalamic T currents. 4. Methyl-phenyl-succinimide (MPS, 1 mM), a compound known to block T currents, was used to examine possible alterations in the pharmacological properties of T channels after injury. MPS was more effective in reducing T currents in normal versus injured RNs (24 and 20% reductions, respectively; P < 0.05), suggesting that pharmacological properties of T channels in the injured RNs may be different from those of the normal RNs.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Canales de Calcio/fisiología , Corteza Cerebral/fisiología , Regeneración Nerviosa/fisiología , Plasticidad Neuronal/fisiología , Degeneración Retrógrada/fisiología , Transmisión Sináptica/fisiología , Tálamo/fisiología , Vías Aferentes/efectos de los fármacos , Vías Aferentes/fisiología , Animales , Anticonvulsivantes/farmacología , Calcio/fisiología , Canales de Calcio/efectos de los fármacos , Células Cultivadas , Corteza Cerebral/efectos de los fármacos , Decorticación Cerebral , Dominancia Cerebral/efectos de los fármacos , Dominancia Cerebral/fisiología , Potenciales de la Membrana/efectos de los fármacos , Potenciales de la Membrana/fisiología , Regeneración Nerviosa/efectos de los fármacos , Plasticidad Neuronal/efectos de los fármacos , Neuronas/efectos de los fármacos , Neuronas/fisiología , Ratas , Ratas Sprague-Dawley , Degeneración Retrógrada/efectos de los fármacos , Succinimidas/farmacología , Transmisión Sináptica/efectos de los fármacos , Tálamo/efectos de los fármacos , Regulación hacia Arriba/efectos de los fármacos , Regulación hacia Arriba/fisiologíaRESUMEN
Recent investigations into the mechanisms of neurotoxicity of acrylamide and gamma-diketones have demonstrated reductions in the delivery of radiolabelled proteins to the distal axon. To differentiate a toxicant-induced compromise in the capacity of the fast anterograde axonal transport system from a neuron cell body processing effect, selective exposure of either the L5 dorsal root ganglion or sciatic nerve to 0.7 mM acrylamide (ACR) or 4 mM 2,5-hexanedione (2,5-HD) was performed during in vitro transport. Nerve exposure to ACR decreased the quantity of transport by 32%, 2,5-HD reduced the quantity by 44%. Ganglion exposure produced no significant changes. We conclude that both toxicants penetrate the nerve barriers and act directly and/or indirectly on the axonal transport mechanisms to cause the reductions in transport.
Asunto(s)
Acrilamidas/toxicidad , Hexanonas/toxicidad , Filamentos Intermedios/efectos de los fármacos , Degeneración Retrógrada/efectos de los fármacos , Acrilamida , Animales , Masculino , Proteínas del Tejido Nervioso/metabolismo , Nervios Periféricos/efectos de los fármacos , Nervios Periféricos/metabolismo , Ratas , Ratas EndogámicasRESUMEN
FPF1070 is an aqueous protein-free solution, which consists of 85% free amino acids and 15% small peptides. Our previous study showed a potent neurotrophic factor-like activity in cultured embryonic cells of dorsal root ganglia. The present study investigated whether FPF1070 regenerated the cholinergic cells in the medial septal nucleus after axonal transections by cutting the fimbria-fornix. Fimbrial transection reduced the number of septal cholinergic cells by 30 +/- 3.6%, compared with the number on contralateral sides at 4 weeks. Intraperitoneal injections of FPF1070 caused 49.9 +/- 6.3% of the cholinergic neurons to survive. Furthermore, the cell sizes of the cholinergic neurons were significantly different: 16.4 +/- 4.2 microns, 14.3 +/- 3.8 microns in FPF1070 treatment and vehicle treatment, respectively. These results indicated that FPF1070 prevents the degeneration and atrophy of impaired cholinergic neurons by systemic administration.
Asunto(s)
Aminoácidos/farmacología , Fibras Colinérgicas/efectos de los fármacos , Hipocampo/efectos de los fármacos , Péptidos/farmacología , Degeneración Retrógrada/efectos de los fármacos , Animales , Recuento de Células , Supervivencia Celular , Colina O-Acetiltransferasa/análisis , Fibras Colinérgicas/química , Hipocampo/cirugía , Masculino , Factores de Crecimiento Nervioso , Proteínas del Tejido Nervioso/farmacología , Ratas , Ratas EndogámicasRESUMEN
Excitotoxic mechanisms due to overactivity of the amino acid neurotransmitters glutamate and aspartate maybe responsible for brain damage after injury. In this review we examine ischaemia and shear injury, which are relevant to human head injury. The opportunities for treatment using glutamate antagonist drugs are discussed.
Asunto(s)
Daño Encefálico Crónico/prevención & control , Lesiones Encefálicas/complicaciones , Fármacos del Sistema Nervioso Central/uso terapéutico , Receptores de N-Metil-D-Aspartato/antagonistas & inhibidores , Animales , Daño Encefálico Crónico/fisiopatología , Lesiones Encefálicas/fisiopatología , Isquemia Encefálica/fisiopatología , Isquemia Encefálica/prevención & control , Maleato de Dizocilpina/uso terapéutico , Evaluación Preclínica de Medicamentos , Antagonistas de Aminoácidos Excitadores , Glutamatos/fisiología , Ácido Glutámico , Humanos , Receptores de N-Metil-D-Aspartato/fisiología , Degeneración Retrógrada/efectos de los fármacos , Degeneración Retrógrada/fisiologíaRESUMEN
Multiple injections of 2 nmols of cyclised ethylcholine mustard aziridinium ion (ECMA), a putative cholinergic neurotoxin, were made (unilaterally) into the cortical terminal field of cholinergic neurons projecting from the nucleus basalis of Meynert (NBM) in the rat basal forebrain. After 30 days, choline acetyltransferase enzymatic activity, a marker for cholinergic function, was significantly lowered in both ipsilateral cortex and NBM, and cholinergic cell bodies in the latter reduced in cross-sectional area, a spectrum of effects characteristic of retrograde degeneration of this pathway. These results are discussed in the context of neurodegenerative diseases affecting cholinergic function.
Asunto(s)
Enfermedad de Alzheimer/inducido químicamente , Aziridinas/farmacología , Azirinas/farmacología , Ganglios Basales/efectos de los fármacos , Corteza Cerebral/efectos de los fármacos , Colina/análogos & derivados , Fibras Colinérgicas/efectos de los fármacos , Degeneración Nerviosa/efectos de los fármacos , Receptores Colinérgicos/efectos de los fármacos , Degeneración Retrógrada/efectos de los fármacos , Sustancia Innominada/efectos de los fármacos , Animales , Colina/farmacología , Colina O-Acetiltransferasa/metabolismo , Modelos Animales de Enfermedad , Masculino , Ratas , Ratas EndogámicasAsunto(s)
Encéfalo/patología , Fibras Colinérgicas/patología , Degeneración Nerviosa , Degeneración Retrógrada , Enfermedad de Alzheimer/patología , Animales , Corteza Cerebral/patología , Fibras Colinérgicas/efectos de los fármacos , Colchicina/farmacología , Gangliósidos/farmacología , Hipocampo/patología , Humanos , Degeneración Nerviosa/efectos de los fármacos , Neurotoxinas/farmacología , Degeneración Retrógrada/efectos de los fármacos , Sustancia Innominada/patologíaRESUMEN
Organotypic tissue cultures, composed of structurally and functionally coupled explants of mouse spinal cord, dorsal root ganglia, and striated muscle, have been used to create a model of the distal (dying-back) axonopathy found in animals and humans with aliphatic hexacarbon neuropathy. Mature explants were treated with 50-650 micrograms/ml of the following hexacarbons dissolved in nutrient fluid: n-hexane, 2-hexanol, 2,5-hexanediol, methyl n-butyl ketone, 5-hydroxy-2-hexanone, 2,5-hexanedione (all neurotoxic), or 2,4-hexanedione (a non-neurotoxic diketone). High concentrations (400-650 micrograms/ml) induced pancytotoxic damage and necrosis of tissue within days, while the lower doses (50-100 micrograms/ml) induced no pathological changes over a period of several weeks. Continuous exposure of explants to 245-325 micrograms/ml (2.8 mM) of the neurotoxic hexacarbons caused specific pathological changes to develop in distal nerve fibers after three to six weeks. Initial changes seen in distal, nonterminal regions of myelinated fibers included: nodal elongation, axonal swellings on proximal-side paranodes, and paranodal myelin retraction. Prolonged treatment was associated with Wallerian-like degeneration of distal nerve fibers. Denuded paranodal swellings in more proximal regions of affected myelinated fibers adopted a more-normal size and underwent remyelination; this occurred during and after the course of treatment. Remyelination by lateral extension from adjacent Schwann cells was documented in living and fixed tissue. The observations confirm the spatial-temporal evolution of hexacarbon distal axonopathy previously suggested from comparable studies in vivo.
Asunto(s)
Axones/efectos de los fármacos , Hexanos/toxicidad , Degeneración Nerviosa/efectos de los fármacos , Degeneración Retrógrada/efectos de los fármacos , Animales , Axones/ultraestructura , Técnicas de Cultivo , Modelos Animales de Enfermedad , Relación Dosis-Respuesta a Droga , Ratones , Fibras Nerviosas Mielínicas/efectos de los fármacos , Fibras Nerviosas Mielínicas/ultraestructura , Degeneración Walleriana/efectos de los fármacosRESUMEN
Experimental degeneration was used in this study to determine if the hypoglossal nerve implanted already in the superior cervical ganglion of adult rat under GABA treatment has established morphologically-identifiable synapses with the dendrites of principal ganglion cells. The implanted hypoglossal nerve trunk was cut in a re-operation, and the ganglionic samples were studied by electron microscopy after 0, 6, 12, 24 and 48 h survival times. First signs of degenerative changes were found in the myelinated and non-myelinated axons alike, 6 h after axotomy. The fine-structural signs of degeneration resembled those of the preganglionic nerve fibres. Degenerating nerve terminals establishing synaptic contacts with the dendrites of the principal ganglion cells were also seen, indicating that the axonal sprouts of the implanted hypoglossal nerve established synaptic contacts with the ganglion cells. It remained, however, to be elucidated whether or not these synapses of the hypoglossal nerve are functionally active contacts while the preganglionic innervation is also present within the ganglion.
Asunto(s)
Nervio Hipogloso/efectos de los fármacos , Degeneración Nerviosa/efectos de los fármacos , Regeneración Nerviosa/efectos de los fármacos , Degeneración Retrógrada/efectos de los fármacos , Sinapsis/efectos de los fármacos , Ácido gamma-Aminobutírico/farmacología , Animales , Fibras Autónomas Preganglionares/ultraestructura , Axones/ultraestructura , Femenino , Ganglios Simpáticos/cirugía , Nervio Hipogloso/trasplante , Nervio Hipogloso/ultraestructura , Microscopía Electrónica , Ratas , Sinapsis/ultraestructuraRESUMEN
The study of toxic experimental models of neuropathies has been a decisive step to understand some cellular mechanisms of human neuropathies. The progressive development of toxic neuropathies allow to the possibility of isolating their initial mechanism. Dying back axonopathies are the commonest neuropathies as observed in clinical practice, and their experimental models had been extensively studied. Acrylamide and n-hexane intoxications have shown the following results : 1) The onset of the neuropathy is located at the most distal node of the longest and largest fibres. Sensory fibres are impaired before the motor ones. 2) Fast axoplasmic transport stops distally. 3) Impaired enzymes of the energetic cycle were observed distally. Proximal axonopathies as those resulting from IDPN intoxication are a possible model to clear up the cellular mechanisms of the lateral amyotrophic sclerosis. Human toxic neuronopathies and myelinopathies are uncommon. Such experimental models are described in relation to other human neuropathies.
Asunto(s)
Acrilamidas/toxicidad , Hexanos/toxicidad , Nitrilos/toxicidad , Enfermedades del Sistema Nervioso Periférico/fisiopatología , Animales , Transporte Axonal , Axones/patología , Enfermedades Desmielinizantes/inducido químicamente , Doxorrubicina/toxicidad , Humanos , Modelos Biológicos , Fibras Nerviosas Mielínicas/fisiología , Enfermedades del Sistema Nervioso Periférico/inducido químicamente , Enfermedades del Sistema Nervioso Periférico/patología , Nódulos de Ranvier/patología , Degeneración Retrógrada/efectos de los fármacos , Células de Schwann/fisiología , Vincristina/toxicidad , Degeneración Walleriana/efectos de los fármacosRESUMEN
Electrophysiological exploration was carried out in 12 patients before and during administration of vincristine sulphate 1,4 mg/m2 body surface area. The patients had stage III or IV lymphoreticulosarcoma and received one injection of vincristine weekly for 6 weeks. Compared with pretreatment findings, (1) motor and sensory conduction velocity, as well as delay in triceps surae H reflex remained unchanged; (2) sensory nerve amplitude and density of distal muscle electromyographic recordings rapidly decreased; (3) the amplitude of distal tendinous reflexes rapidly diminished, whereas that of the H reflex remained stable. These results being similar to those observed in experimental acrylamide toxicity, where a "dying back" hemopathy has been demonstrated, it is suggested that the neuropathy induced by vincristine in man is of the same type.
Asunto(s)
Axones/efectos de los fármacos , Enfermedades del Sistema Nervioso Periférico/inducido químicamente , Vincristina/efectos adversos , Acrilamidas/envenenamiento , Adulto , Electrofisiología , Femenino , Humanos , Linfoma no Hodgkin/tratamiento farmacológico , Masculino , Persona de Mediana Edad , Enfermedades del Sistema Nervioso Periférico/fisiopatología , Degeneración Retrógrada/efectos de los fármacos , Factores de TiempoRESUMEN
The material, with few exceptions, consists of PAS-gallocyanin stained paraffin sections from 4- to 6-month-old male rabbits fixed by perfusion first with saline and then with Bouin's solution. (1) In animals treated with cortisone prior to and subsequent to axotomy, the neurons exhibit an accelerated dispersal and delayed reconstitution of Nissl substance (ribosomes). While mitotic activity is depressed at various sites, formation of new microglial cells is evident. Neuronal degeneration with karyorrhexis is occasionally noted in single neurons in the lateral parts of the facial nucleus. An increase in intraneuronal glycogen deposition is manifested by a greater number of glycogen-rich neurons; such neurons are depleted of their glycogen after axotomy. (2) In other animals, reoperation of the facial nerve on the 6th, 22nd, 60th and 120th day, followed by survival of 3 days, results in dispersal of restored Nissl substance and in increased extravascular mitotic activity which is of less intensity than in single-operated animals.