Neuroscience research
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Neuroscience research · Oct 2000
Downregulation of TrkA expression in primary sensory neurons after unilateral lumbar spinal nerve transection and some rescuing effects of nerve growth factor infusion.
Peripheral nerve injury results in sprouting of sympathetic and sensory nerve terminals around large diameter neurons in the dorsal root ganglia (DRG), but the underlying mechanism is not clear. Current study sought to examine changes of the nerve growth factor (NGF) receptor TrkA in DRG and spinal cord after a spinal nerve transection by an immunohistochemical technique and to investigate effects of NGF on the expression of TrkA protein in the same animal model. In the control rat, TrkA immunoreactivity was localized to about 55 +/ -1% of total neurons in DRG and to laminae I and II of the spinal cord. ⋯ Exogenous NGF delivered to DRG for 2 weeks partially reversed the reduction of TrkA expression as well as atrophy of TrkA immunoreactive neurons. No TrkA immunoreactive basket was found around neuronal somata. Our data show that unilateral peripheral nerve injury results in dynamic downregulation of TrkA in sensory neurons in bilateral DRG and spinal cord, and that TrkA expression in sensory neurons is partially regulated by target-derived NGF.
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Neuroscience research · Sep 2000
Involvement of G-protein-activated inwardly rectifying K (GIRK) channels in opioid-induced analgesia.
To investigate the role of G-protein-activated inwardly rectifying K+ (GIRK) channels in opioid-induced analgesia, we compared the effects of opioids in wild-type and weaver mutant mice having mutant GIRK channels. In the tail-flick and hot-plate tests, weaver mutant mice displayed significantly lower analgesia after either morphine or (-)-U-50488 administration. These findings suggest that GIRK channel activation is important in the induction of analgesia by opioids.
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Neuroscience research · Aug 2000
VAMP-2 promotes neurite elongation and SNAP-25A increases neurite sprouting in PC12 cells.
Recent studies suggest that the soluble N-ethylmaleimide-sensitive factor attached protein (SNAP) receptor (SNARE)-mediated membrane fusion system is involved in vesicle fusion in the plasma membrane that allows expansion for neurite elongation. There have been several reports analyzing the effects of neurite outgrowth by inhibition of SNAREs. In this study, we took the opposite approach by overexpressing green fluorescent protein (GFP)-fusion SNAREs, including VAMP-2, SNAP-25A, and syntaxin1A, in PC12 cells to investigate the role of SNAREs in the neurite outgrowth of PC12 cells. ⋯ These findings suggest that when overexpressed in PC12 cells, VAMP-2 can promote neurite elongation, while SNAP-25A can stimulate neurite sprouting. On the other hand, overexpression of syntaxin1A neither promotes nor inhibits neurite outgrowth. Thus VAMP-2 and SNAP-25A play different roles in neurite elongation and sprouting.
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Neuroscience research · Apr 2000
The effect of intrastriatal single injection of GDNF on the nigrostriatal dopaminergic system in hemiparkinsonian rats: behavioral and histological studies using two different dosages.
Glial cell line-derived neurotrophic factor (GDNF) is a member of the transforming growth factor-beta superfamily and acts as a neurotrophic factor for the nigrostriatal dopamine (DA) system. Although previous studies have shown that pretreatment with GDNF could prevent degenerative changes of nigrostriatal DA system by DA neurotoxin 6-hydroxydopamine (6-OHDA), it is not really known whether GDNF can induce recovery of nigrostriatal DA system after partial lesioning by 6-OHDA. Substantia nigra has been commonly chosen as injection site for GDNF but a limited number of studies have used striatum as injection site where neural transplantation is commonly performed. ⋯ These immunocytochemical results have also shown that 100 microg of GDNF was more potent than 10 microg of GDNF. These morphological and functional results indicate that GDNF treatment 4 weeks after 6-OHDA lesioning could induce recovery of nigrostriatal DA system. Striatum was a good site for GDNF administration for hemiparkinsonian rats and a single injection of 100 microg of GDNF was more potent than 10 microg of GDNF.
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Neuroscience research · Jan 2000
Direct projection from the cardiovascular control region of the cerebellar cortex, the lateral nodulus-uvula, to the brainstem in rabbits.
In decerebrate unanesthetized rabbits, electrical stimulation of the lateral nodulus-uvula in the cerebellar vermal cortex evoked an increase in renal sympathetic nerve activity, an increase in blood pressure and a decrease in renal arterial blood flow, which were all in contrast to the effects reported previously in the anesthetized rabbits. In order to identify the pathway mediating these responses, we investigated the Purkinje cell projection from the lateral nodulus-uvula using both anterograde (biotinylated dextran amine, BDA) and retrograde (horseradish peroxidase, HRP) tracing methods in rabbits. When BDA was iontophoretically injected into the lateral nodulus-uvula, labeled Purkinje cell axons were found within and around the superior and inferior cerebellar peduncles (SCP and ICP, respectively). ⋯ When HRP was microinjected into the lateral PB, retrogradely labeled Purkinje cells were found in the lateral nodulus-uvula. These results indicate that Purkinje cells in the lateral nodulus-uvula project into the vestibular nuclei via the ICP and to the lateral PB via the SCP. We suggest that these two pathways mediating cardiovascular responses have different sensitivities to anesthetics.