RESUMEN
The parafascicular nucleus (PFN) of the thalamus is a primary structure in the feedback circuit of the basal ganglia-thalamo-cortical system, as well as in the neural circuit of the vestibulo-thalamo-striatal pathway. We investigated the characteristics of the functional connectivity between the peripheral vestibular system and the PFN in rats. A single electrical stimulation was applied to the horizontal semicircular canal nerve in the peripheral vestibular end-organs. This resulted in polysynaptic local field potentials (LFPs) in the PFN, which were composed of long-lasting multiple waves. The LFPs were prominently seen contralateral to the stimulation site. The PFN LFPs were suppressed by transient chemical de-afferentation of peripheral vestibular activity using a 5% lidocaine injection into the middle ear. The spontaneous firing rate of the single units increased after electrical stimulation to the horizontal canal nerve in a frequency-dependent manner. The induction of cFos protein was more prominent in the contralateral PFN than in the ipsilateral PFN following horizontal semicircular canal nerve stimulation. The functional vestibulo-parafascicular connection is a neural substrate for the transmission of vestibular sensory information to the basal ganglia.
Asunto(s)
Vías Aferentes/fisiología , Estimulación Eléctrica , Núcleos Talámicos Intralaminares/fisiología , Neuronas/fisiología , Nervio Vestibular/fisiología , Potenciales de Acción/fisiología , Análisis de Varianza , Animales , Biofisica , Lateralidad Funcional , Núcleos Talámicos Intralaminares/citología , Proteínas Proto-Oncogénicas c-fos/metabolismo , Ratas , Ratas Sprague-Dawley , Potenciales Sinápticos/fisiologíaRESUMEN
BACKGROUND: Anodal transcranial direct current stimulation (A-tDCS) induces a long-lasting increase in cortical excitability that can increase gene transcription in the brain. OBJECTIVE: The purpose of this study was to evaluate the expression of genes related to activity-dependent neuronal plasticity in the sensorimotor cortex and hippocampus of young Sprague-Dawley rats following A-tDCS. METHODS: We applied A-tDCS over the right sensorimotor cortex epicranially with a circular electrode (3âmm diameter) at 250 µA for 20âmin per day for 7 consecutive days. Levels of mRNA for brain-derived neurotrophic factor (BDNF), cAMP response element-binding protein (CREB), synapsin I, Ca2+/calmodulin-dependent protein kinase II (CaMKII), activity-regulated cytoskeleton-associated protein (Arc), and c-Fos were analyzed using SYBR Green quantitative real-time polymerase chain reaction (PCR). RESULTS: We found that 7 days of unilateral A-tDCS resulted in significant increases in transcription of all plasticity-related genes tested in the ipsilateral cortex. Daily A-tDCS also resulted in a significant increase in c-Fos mRNA in the ipsilateral hippocampus. CONCLUSION: These results indicate that altered expression of plasticity-associated genes in the cortex and hippocampus is a molecular substrate of A-tDCS-induced neural plasticity.
Asunto(s)
Corteza Cerebral/metabolismo , Expresión Génica/fisiología , Hipocampo/metabolismo , Plasticidad Neuronal/fisiología , Estimulación Transcraneal de Corriente Directa , Animales , Factor Neurotrófico Derivado del Encéfalo/genética , Factor Neurotrófico Derivado del Encéfalo/metabolismo , Proteína de Unión a CREB/genética , Proteína de Unión a CREB/metabolismo , Proteína Quinasa Tipo 2 Dependiente de Calcio Calmodulina/genética , Proteína Quinasa Tipo 2 Dependiente de Calcio Calmodulina/metabolismo , Proteínas del Citoesqueleto/genética , Proteínas del Citoesqueleto/metabolismo , Electrodos , Masculino , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/metabolismo , Proteínas Proto-Oncogénicas c-fos/genética , Proteínas Proto-Oncogénicas c-fos/metabolismo , ARN Mensajero/metabolismo , Ratas , Ratas Sprague-Dawley , Sinapsinas/genética , Sinapsinas/metabolismoRESUMEN
PURPOSE: Transcranial direct current stimulation (tDCS) is increasingly seen as a useful tool for noninvasive cortical neuromodulation. A number of studies in humans have shown that when tDCS is applied to the motor cortex it can modulate cortical excitability. It is especially interesting to note that when applied with sufficient duration and intensity, tDCS can enable long-lasting neuroplastic effects. However, the mechanism by which tDCS exerts its effects on the cortex is not fully understood. We investigated the effects of anodal tDCS under urethane anesthesia on field potentials in in vivo rats. METHODS: These were measured on the skull over the right motor cortex of rats immediately after stimulating the left corpus callosum. RESULTS: Evoked field potentials in the motor cortex were gradually increased for more than one hour after anodal tDCS. To induce these long-lasting effects, a sufficient duration of stimulation (20 minutes or more) was found to may be required rather than high stimulation intensity. CONCLUSION: We propose that anodal tDCS with a sufficient duration of stimulation may modulate transcallosal plasticity.