Neuroscience research
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Neuroscience research · Jan 2007
Migration and nucleogenesis of mouse precerebellar neurons visualized by in utero electroporation of a green fluorescent protein gene.
Neural migration is a critical step for accurate CNS development, but the molecular mechanisms that regulate migration, settlement and nucleogenesis remain largely unknown. The precerebellar neurons (PCNs), generated in the lower rhombic lip (LRL), migrate towards their destinations: some neurons form the pontine gray nucleus (PGN) and reticulotegmental nucleus (RTN) in the ipsilateral pons, while others form the lateral reticular and external cuneate nuclei in the contralateral medulla after crossing the midline. Here, by introducing an EGFP gene into a unilateral LRL of mouse embryos by in utero electroporation, we specifically labeled and tracked the PCNs in vivo. ⋯ In addition, we found that a subpopulation of the interpolar subnucleus of the spinal trigeminal nucleus, which projects the axons to the cerebellum, was one of the PCNs derived from the LRL. Furthermore, because the electroporated mice were born and grew up healthy, we could visualize the PCNs and their mossy fibers in the adult brain. Therefore, the EGFP labeling of PCNs can be applied to studying the physiology of the mossy fiber system as well as PCN development in embryos.
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Neuroscience research · Nov 2006
Comparative StudyDynamic changes in Robo2 and Slit1 expression in adult rat dorsal root ganglion and sciatic nerve after peripheral and central axonal injury.
Robos are transmembrane receptors that mediate Slit signaling to repel growth cone outgrowth and neural migration in the developing central nervous system. Their distribution and function in the peripheral nervous system remains unclear. In the present study, we examined expression of Slit1 and Robo2 in adult rat dorsal root ganglion (DRG), spinal cord and sciatic nerve after peripheral nerve injury (axotomy). ⋯ Sciatic nerve transection also led to an accumulation of Slit1 protein in peripheral region of the traumatic neuroma. In conclusion, we report an altered expression and redistribution of Robo2 and Slit1 in the DRG and sciatic nerve trunk after peripheral axotomy. Our results indicate that Slit1 and Robo2 likely play an important role in regeneration after peripheral nerve injury.
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Neuroscience research · Sep 2006
Assessing mechanical sensitivity of masseter muscle in lightly anesthetized rats: a model for craniofacial muscle hyperalgesia.
In this report, we present a simple and reliable way of assessing mechanical sensitivity of masseter muscle as a model for craniofacial muscle hyperalgesia. Mechanical thresholds that evoke nocifensive hindpaw responses following noxious masseter stimulation were assessed. ⋯ This lightly anesthetized rodent paradigm allows us to provide calibrated and reliable mechanical stimulus, which is not possible in behaving animals. The technique can be applied to study mechanistic bases for craniofacial muscle tenderness.
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Neuroscience research · Aug 2006
The lumbar spinal cord glial cells actively modulate subcutaneous formalin induced hyperalgesia in the rat.
We investigated the response and relationship of glial cells and neurons in lumbar spinal cord to hyperalgesia induced by the unilateral subcutaneous formalin injection into the hindpaw of rats. It was demonstrated that Fos/NeuN immunoreactive (-IR) neurons, glial fibrillary acidic protein (GFAP)-IR astrocytes and OX42-IR microglia were distributed in dorsal horn of lumbar spinal cord, predominantly in the superficial layer. In the time-course studies, GFAP-IR astrocytes were firstly detected, OX42-IR microglia were sequentially observed, Fos/NeuN-IR neurons were found slightly late. ⋯ Ninety-one HGJs were found in 100 areas of experimental rats and occupied 91%, while only 39% HGJs were found in control rats. In experimental rats pretreated with intrathecal (i.t.) application of the carbenoxolone (a gap junction blocker) or fluorocitrate (a glial metabolic inhibitor), the paw withdrawal thermal latency was prolonged than those application of the sterile saline (i.t.). It suggests that spinal cord glial cells may play an important role for modulation of hyperalgesia induced by noxious stimuli through HGJs which located between astrocytes and neurons.
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Neuroscience research · Aug 2006
Theoretical and experimental studies of relationship between pinwheel centers and ocular dominance columns in the visual cortex.
In the visual cortex, pinwheel centers, which appear as point singularities in orientation maps, are likely to be found at the centers of ocular dominance columns in normal cats and monkeys. To elucidate the mechanism underlying the geometrical relationship, we performed computer simulation based on our correlation-based self-organization model. The simulation showed that pinwheel centers tended to be located at the ocular dominance centers at higher correlations of activities between the left- and right-eye specific pathways, whereas they tended to appear along the borders of ocular dominance columns at lower correlations. ⋯ The between-eye activity correlation in dark-reared cats is expected to be lower than that in normal cats due to the lack of common visual input in the two eyes. The statistical analysis of experimental data showed that while more pinwheel centers tended to be located in the center subregion of ocular dominance columns than in the border subregion in the normal cats, a weak tendency in the opposite direction was found in the dark-reared cats. Based on the consistent results from the model and experiment, it is suggested that the activity correlation between the left- and right-eye specific pathways has influence on the establishment of geometrical relationship in the cortical representation between orientation preference and ocular dominance.