RESUMEN
There is accumulating evidence that the centre median-parafascicular (CM/Pf) complex of the thalamus is implicated in basal ganglia-related movement disorders and notably in Parkinson's disease. However, the impact of the changes affecting CM/Pf on the pathophysiological functioning of basal ganglia in parkinsonian state remains poorly understood. To address this issue, we have examined the effects of excitotoxic lesion of CM/Pf and of 6-hydroxydopamine-induced lesion of nigral dopamine neurons, separately or in association, on gene expression of markers of neuronal activity in the rat basal ganglia (striatal neuropeptide precursors, GAD67, cytochrome oxidase subunit I) by quantitative in situ hybridization histochemistry. CM/Pf lesion prevented the changes produced by the dopamine denervation in the components of the indirect pathway connecting the striatum to the output structures (striatopallidal neurons, globus pallidus, subthalamic nucleus), and among the output structures, in the entopeduncular nucleus. Preliminary data on the effects of deep brain stimulation of CM/Pf in rats with nigral dopamine lesion show that this surgical approach produces efficient anti-akinetic effect associated with partial reversal of the dopamine lesion-induced increase in striatal preproenkephalin A mRNA levels, a marker of the striatopallidal neurons. These data, which provide substrates for the potential of CM/Pf surgery in the treatment of movement disorders, are discussed in comparison with the effects of lesion or deep brain stimulation of the subthalamic nucleus, the currently preferred target for the surgical treatment of PD.
Asunto(s)
Ganglios Basales/fisiopatología , Núcleos Talámicos Intralaminares/fisiopatología , Enfermedad de Parkinson/fisiopatología , Animales , Ganglios Basales/efectos de los fármacos , Ganglios Basales/metabolismo , Estimulación Encefálica Profunda/métodos , Modelos Animales de Enfermedad , Dopamina/metabolismo , Núcleos Talámicos Intralaminares/efectos de los fármacos , Núcleos Talámicos Intralaminares/patología , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Oxidopamina/administración & dosificación , Oxidopamina/toxicidad , Enfermedad de Parkinson/patología , Enfermedad de Parkinson/terapia , RatasRESUMEN
Midbrain dopamine (DA) neurons play a central role in the regulation of voluntary movement, and their degeneration is associated with Parkinson's disease. Cell replacement therapies, and in particular embryonic stem (ES) cell-derived DA neurons, offer a potential therapeutic venue for Parkinson's disease. We sought to identify genes that can potentiate maturation of ES cell cultures to the midbrain DA neuron phenotype. A number of transcription factors have been implicated in the development of midbrain DA neurons by expression analyses and loss-of-function knockout mouse studies, including Nurr1, Pitx3, Lmx1b, Engrailed-1, and Engrailed-2. However, none of these factors appear sufficient alone to induce the mature midbrain DA neuron phenotype in ES cell cultures in vitro, suggesting a more complex regulatory network. Here we show that Nurr1 and Pitx3 cooperatively promote terminal maturation to the midbrain DA neuron phenotype in murine and human ES cell cultures.
Asunto(s)
Diferenciación Celular/genética , Proteínas de Unión al ADN/fisiología , Regulación del Desarrollo de la Expresión Génica , Proteínas de Homeodominio/fisiología , Mesencéfalo/crecimiento & desarrollo , Células Madre/citología , Factores de Transcripción/fisiología , Animales , Células Cultivadas , Proteínas de Unión al ADN/metabolismo , Dopamina/metabolismo , Embrión de Mamíferos/citología , Proteínas de Homeodominio/metabolismo , Humanos , Mesencéfalo/citología , Mesencéfalo/metabolismo , Ratones , Neuronas/citología , Neuronas/metabolismo , Miembro 2 del Grupo A de la Subfamilia 4 de Receptores Nucleares , Fenotipo , Trasplante de Células Madre , Factores de Transcripción/metabolismoRESUMEN
This study examined the effects of prolonged (4 days) high frequency stimulation (HFS) of the subthalamic nucleus (STN), in comparison with those of STN lesion, on the dopamine denervation-mediated cellular changes in the basal ganglia in a Wistar rat model of Parkinson's disease. STN HFS counteracted the dopamine lesion-induced increase in GAD67 mRNA expression in the output structures of the basal ganglia, as shown previously after STN lesion, providing cellular support for the similar antiparkinsonian benefits produced by the two surgical procedures. The dopamine denervation-induced increase in GAD67 mRNA levels in the globus pallidus was partially antagonized after HFS and totally reversed after ibotenate-induced STN lesion. The overexpression of striatal enkephalin mRNA tended to be further increased by HFS but was antagonized by STN lesion. The decrease in striatal substance P mRNA levels was affected neither by STN HFS nor lesion. As STN HFS for two hours was previously found not to interfere with the effects of dopamine lesion in the globus pallidus and striatum, the present data provide strong evidence that the effects of STN surgery in these structures involve long-term adaptive processes and that the rearrangements mediated by HFS and lesion are, at least in part, different.
Asunto(s)
Cuerpo Estriado/patología , Dopamina/metabolismo , Globo Pálido/patología , Núcleo Subtalámico/patología , Animales , Cuerpo Estriado/metabolismo , Desnervación/métodos , Estimulación Eléctrica/métodos , Globo Pálido/metabolismo , Masculino , Mazindol/metabolismo , Oxidopamina/toxicidad , Unión Proteica/fisiología , ARN Mensajero/biosíntesis , Ratas , Ratas Wistar , Núcleo Subtalámico/metabolismoRESUMEN
Intralaminar thalamic nuclei represent a major site of non-dopaminergic degeneration in Parkinson disease, but the impact of this degeneration on the pathophysiological functioning of basal ganglia remains unknown. To address this issue, we compared the effects of 6-hydroxydopamine-induced lesions of nigral dopamine neurons alone or combined with ibotenate-induced lesions of intralaminar thalamic neurons on markers of neuronal metabolic activity in the rat basal ganglia using in situ hybridization histochemistry. Thalamic lesions prevented most of the dopamine denervation-induced changes (i.e. the increases in mRNA levels of enkephalin and GAD67 in the striatum, of GAD67 in the globus pallidus and entopeduncular nucleus, and of cytochrome oxidase subunit-I in the subthalamic nucleus), but did not affect the downregulation of striatal substance P and upregulation of GAD67 in the substantia nigra pars reticulata. We also provide immunohistochemical evidence that thalamic lesions markedly decreased striatal expression of the vesicular glutamate transporter vGluT2, confirming the association of this transporter with the thalamic projections to the basal ganglia. Altogether, these data reveal a major antagonistic influence of thalamic and dopaminergic afferents onto the basal ganglia and suggest that degeneration of thalamic neurons in Parkinson disease may represent an important factor counteracting expression of the defects associated with the dopamine denervation.
Asunto(s)
Ganglios Basales/metabolismo , Expresión Génica/efectos de los fármacos , Núcleos Talámicos Intralaminares/patología , Proteínas de Transporte de Membrana , Neuronas/metabolismo , Simpatectomía Química , Proteínas de Transporte Vesicular , Adrenérgicos/farmacología , Animales , Autorradiografía , Ganglios Basales/efectos de los fármacos , Ganglios Basales/patología , Proteínas Portadoras/biosíntesis , Proteínas Portadoras/efectos de los fármacos , Dopamina/metabolismo , Femenino , Glutamato Descarboxilasa/biosíntesis , Glutamato Descarboxilasa/efectos de los fármacos , Ácido Iboténico/farmacología , Inmunohistoquímica , Hibridación in Situ , Núcleos Talámicos Intralaminares/efectos de los fármacos , Isoenzimas/biosíntesis , Isoenzimas/efectos de los fármacos , Neuronas/efectos de los fármacos , Neuronas/patología , Neuropéptidos/biosíntesis , Neuropéptidos/efectos de los fármacos , Oxidopamina/farmacología , Trastornos Parkinsonianos/inducido químicamente , Ratas , Ratas Wistar , Sustancia Negra/patología , Proteína 2 de Transporte Vesicular de GlutamatoRESUMEN
This study examined the consequences of systemic treatment with either L-dopa or MK-801 on the levels of mRNAs encoding the 65 and 67 kDa isoforms of glutamate decarboxylase (GAD65 and GAD67) in the striatum and globus pallidus (GP) of rats rendered hemiparkinsonian by intranigral 6-hydroxydopamine injection. GADs mRNA levels were assessed by means of in situ hybridization histochemistry. In the striatum, dopamine denervation resulted in increased GAD67 mRNA levels at the rostral and caudal levels, whereas GAD65 showed selective increase at the caudal level. L-dopa and MK-801 treatments showed differential effects on the two GAD isoform levels in rats with 6-hydroxydopamine lesion. The lesion-induced increases in GAD67 transcripts were potentiated by L-dopa but unaffected by MK-801, whereas the increases in GAD65 were suppressed by MK-801 but unaffected by L-dopa. These data suggest a heterogeneity of glutamate-dopamine interaction in the anteroposterior extent of the striatum and show that NMDA-mediated mechanisms are involved in the 6-hydroxydopamine lesion-induced transcriptional changes in striatal GAD65 but not GAD67. In GP, the 6-OHDA lesion elicited increases in both GAD65 and GAD67 mRNA levels. L-dopa or MK-801 treatment suppressed the lesion-induced augmentations in the two GADs mRNA levels. These results indicate that dopamine denervation-induced changes in the functional activity of GP neurons involve both dopamine and glutamate NMDA receptor-mediated mechanisms. Comparison between the effects of L-dopa and MK-801 treatments on markers of the activity of striatal and pallidal GABA neurons further suggest that the impact of these treatments at the GP level do not depend solely on the striatopallidal input.
Asunto(s)
Maleato de Dizocilpina/farmacología , Globo Pálido/efectos de los fármacos , Glutamato Descarboxilasa/biosíntesis , Isoenzimas/biosíntesis , Levodopa/farmacología , Trastornos Parkinsonianos/enzimología , Animales , Maleato de Dizocilpina/uso terapéutico , Femenino , Globo Pálido/enzimología , Inyecciones Subcutáneas , Levodopa/uso terapéutico , Trastornos Parkinsonianos/inducido químicamente , Trastornos Parkinsonianos/tratamiento farmacológico , ARN Mensajero/biosíntesis , Ratas , Ratas WistarRESUMEN
This study investigated the influence of thalamic inputs on neuronal metabolic activity in the rat basal ganglia. By means of in situ hybridization histochemistry, we examined the consequences of ibotenate-induced unilateral lesion of intralaminar thalamic nuclei on mRNA expression of cytochrome oxidase subunit-I (CoI) in the striatum and the subthalamic nucleus (STN) and of the two isoforms of glutamate decarboxylase (GAD65 and GAD67) in the striatum, globus pallidus (GP), entopeduncular nucleus (EP) and substantia nigra pars reticulata (SNr). In the striatum, GAD67 mRNA expression decreased selectively in the rostral part of the structure at 5 and 12 days postlesion (approximately -30%), whereas, GAD65 mRNA levels was downregulated only in the caudal striatum at 12 days (-29%). In both the striatum and STN, CoI mRNA expression decreased ipsilaterally at 5 and bilaterally at 12 days. In GP, GAD67 and GAD65 mRNA expression decreased ipsilaterally at 5 (-20% and -26%) and 12 days (-23% and -36%). In EP, selective bilateral decreases in GAD67 mRNA expression were found at 5 and 12 days (-50% and -40%). Conversely, in SNr, only GAD65 mRNA expression was reduced bilaterally at both time points. These data show that the thalamus exerts a widespread excitatory influence on the basal ganglia network that cannot be accounted for solely by its known direct connections. Given the recent data showing that intralaminar thalamic nuclei are a major nondopaminergic site of neurodegeneration in Parkinson's disease, these results may have a critical bearing on understanding the cellular basis of basal ganglia dysfunction in parkinsonism.