Neuroscience
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Comparative Study
Estradiol inhibits atp-induced intracellular calcium concentration increase in dorsal root ganglia neurons.
Estrogen has been implicated in modulation of pain processing. Although this modulation occurs within the CNS, estrogen may also act on primary afferent neurons whose cell bodies are located within the dorsal root ganglia (DRG). Primary cultures of rat DRG neurons were loaded with Fura-2 and tested for ATP-induced changes in intracellular calcium concentration ([Ca(2+)](i)) by fluorescent ratio imaging. ⋯ Co-administration of these blockers with estrogen induced a further decrease of the ATP-induced [Ca(2+)](i) flux. Together, these results suggest that although ATP stimulation of P2X receptors activates L-, N-, and P-type VGCC, estradiol primarily blocks L-type VGCC. The estradiol regulation of this ATP-induced [Ca(2+)](i) transients suggests a mechanism through which estradiol may modulate nociceptive signaling in the peripheral nervous system.
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Comparative Study
Sec6 is localized to the plasma membrane of mature synaptic terminals and is transported with secretogranin II-containing vesicles.
The sec6/8 (exocyst) complex is implicated in targeting of vesicles for regulated exocytosis in various cell types and is believed to play a role in synaptogenesis and brain development. We show that the subunits sec6 and sec8 are present at significant levels in neurons of adult rat brain, and that immunoreactivity for the two subunits has a differential subcellular distribution. We show that in developing as well as mature neurons sec6 is concentrated at the inside of the presynaptic plasma membrane, while sec8 immunoreactivity shows a diffuse cytoplasmic distribution. ⋯ Neuronal induction of the PC12 cells with nerve growth factor shows that sec8 is not freely soluble, but may probably interact with cytoskeletal elements. The complex may facilitate the targeting of membrane material to presynaptic sites and may possibly shuttle vesicles from the cytoskeletal transport machinery to presynaptic membrane sites. Thus, we suggest that the exocyst complex serves to modulate exocytotic activity, by targeting membrane material to its presynaptic destination.
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Comparative Study
Distribution and colocalisation of glutamate decarboxylase isoforms in the rat spinal cord.
The inhibitory neurotransmitter GABA is synthesized by glutamic acid decarboxylase (GAD), and two isoforms of this enzyme exist: GAD65 and GAD67. Immunocytochemical studies of the spinal cord have shown that whilst both are present in the dorsal horn, GAD67 is the predominant form in the ventral horn. The present study was carried out to determine the pattern of coexistence of the two GAD isoforms in axonal boutons in different laminae of the cord, and also to examine the relation of the GADs to the glycine transporter GLYT2 (a marker for glycinergic axons), since many spinal neurons are thought to use GABA and glycine as co-transmitters. ⋯ GLYT2 immunoreactivity was associated with many GAD-immunoreactive boutons; however, this did not appear to be related to the pattern of GAD expression. It has recently been reported that there is selective depletion of GAD65, accompanied by a loss of GABAergic inhibition, in the ipsilateral dorsal horn in rats that have undergone peripheral nerve injuries [J Neurosci 22 (2002) 6724]. Our finding that some boutons in the superficial laminae showed relatively high levels of GAD65 and low levels of GAD67 immunoreactivity is therefore significant, since a reduction in GABA synthesis in these axons may contribute to neuropathic pain.
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Comparative Study
Role and regulation of p53 in depolarization-induced neuronal death.
The tumor suppressor gene p53 is a potent transcriptional regulator for genes involved in many cellular activities including cell cycle arrest and apoptosis. In this study, we examined the role of p53 in neuronal death induced by the sodium channel modulator veratridine. We also analyzed the involvement of Ca2+, mitochondria and reactive oxygen species in p53 activation. ⋯ Antisense knockdown of p53 resulted in a significant increase in neuronal survival after veratridine treatment. This protective effect was maintained on N-methyl-D-aspartate or ischemia-induced death but not on staurosporine cytotoxicity. These results together suggest that p53-expression is involved in veratridine-induced neuronal death and that p53 might be a link between toxic stimuli of different types and neuronal death.
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Comparative Study
P2 receptors in satellite glial cells in trigeminal ganglia of mice.
There is strong evidence for the presence of nucleotide (P2) receptors in sensory neurons, which might play a role in the transmission of pain signals. In contrast, virtually nothing is known about P2 receptors in satellite glial cells (SGCs), which are the main glial cells in sensory ganglia. We investigated the possibility that P2 receptors exist in SGCs in murine trigeminal ganglia, using Ca(2+) imaging, patch-clamp recordings, and immunohistochemistry. ⋯ Patch-clamp recordings of SGCs did not reveal any inward current due to ATP. Therefore, there was no evidence for the activation of ionotropic P2X receptors under the present conditions. The results indicate the presence of functional nucleotide (P2Y) receptors in SGCs.