Cellular and molecular neurobiology
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Cell. Mol. Neurobiol. · Nov 2013
Clonidine suppresses the induction of long-term potentiation by inhibiting HCN channels at the Schaffer collateral-CA1 synapse in anesthetized adult rats.
Activation of alpha2-adrenoceptors inhibits long-term potentiation and long-term depression in many brain regions. However, effectiveness and mechanism of alpha2-adrenoceptors for synaptic plasticity at the Schaffer collateral-CA1 synapses in rat in vivo is unclear. In the present study, we investigated the effects of alpha2-adrenoceptors agonist clonidine on high-frequency stimulation (HFS)-induced long-term potentiation (LTP) and paired-pulse facilitation (PPF) at the Schaffer collateral-CA1 synapse of rat hippocampus in vivo. ⋯ Moreover, the inhibition was accompanied by a significant increase of the normalized PPF ratio. Furthermore, clonidine at 1 and 10 μM significantly decreased glutamate (Glu) content in the culture supernatants of hippocampal neurons, and yohimbine at 1 and 10 μM had no effect on Glu release, while it could reverse the inhibition of clonidine (1 and 10 μM) on Glu release. In conclusion, clonidine can suppress the induction of LTP at the Schaffer collateral-CA1 synapse, and the possible mechanism is that activation of presynaptic alpha2-adrenoceptors reduces the Glu release by inhibiting HCN channels.
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Cell. Mol. Neurobiol. · Oct 2013
Differential regulation of glucocorticoid receptor expression in distinct columns of periaqueductal grey in rats with behavioural disability following nerve injury.
Neuropathic pain is diagnosed primarily by sensory dysfunction, which includes both spontaneous, and stimulus-evoked pain. Clinical evaluation highlights the disabilities which characterise this condition for most patients. Chronic constriction injury of the sciatic nerve (CCI) evokes sensory dysfunction characteristic of neuropathic pain. ⋯ The dorsolateral PAG had significant increases in the number of GR-immunoreactive (GR-IR) cells and the caudal lateral and ventrolateral PAG each had significant reductions in the number of GR-IR cells. These regional increases and decreases correlated with the degree of disability, as indicated by the degree of change in social behaviours. Our results suggest a role for altered PAG, GR-corticosterone interactions and their resultant cellular consequences in the expression of disabilities in a subpopulation of nerve-injured rats.
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Cell. Mol. Neurobiol. · Jul 2013
Effect of subpressor dose of angiotensin II on pain-related behavior in relation with neuronal injury and activation of satellite glial cells in the rat dorsal root ganglia.
To clarify the role of angiotensin II (Ang II) in the regulation of sensory signaling, we studied the effect of subpressor dose (150 ng/kg/min) of Ang II on pain-related behavior in relation with neuronal injury and activation of satellite glial cells (SGCs) in the dorsal root ganglia (DRGs) after chronic constriction injury (CCI). Systemic continuous delivery of Ang II induced the tactile, heat and cold hyperlagesia, when measured at 7 days ofpost-injury. ⋯ Subpressor dose of Ang II induced an increase of activated SGCs (detected by GFAP immunolabeling) enveloping large-diameter neurons. Our results suggested that Ang II through the AT1 receptor activation is an important regulatory factor in neuropathic pain perception and plays an important role in the injury of large-sized primary afferent neurons and activation of SGCs elicited by the CCI.
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To determine if recent observations of hypoglycemia in patients receiving high-dose methadone extended to an animal model, we explored the effects of methadone and other mu-opioids on blood glucose levels in mice. Methadone lowered blood glucose in a dose-dependent manner with 20 mg/kg yielding a nadir in average glucose levels to 55 ± 6 mg/dL from a baseline of 172 ± 7 mg/dL, an effect that was antagonized by naloxone and mu selective antagonists β-funaltrexamine and naloxonazine. ⋯ Similar differences among mu-opioid agonists have been observed in other systems, suggesting the possible role of selected splice variants of the mu-opioid receptor gene Oprm1. This mouse model recapitulates our clinical observations and emphasizes the need to carefully monitor glucose levels when using high methadone doses, particularly intravenously, and the need for controlled clinical trials.
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Cell. Mol. Neurobiol. · May 2013
Initial contact of glioblastoma cells with existing normal brain endothelial cells strengthen the barrier function via fibroblast growth factor 2 secretion: a new in vitro blood-brain barrier model.
Glioblastoma multiforme (GBM) cells invade along the existing normal capillaries in brain. Normal capillary endothelial cells function as the blood-brain barrier (BBB) that limits permeability of chemicals into the brain. To investigate whether GBM cells modulate the BBB function of normal endothelial cells, we developed a new in vitro BBB model with primary cultures of rat brain endothelial cells (RBECs), pericytes, and astrocytes. ⋯ Fibroblast growth factor 2 (FGF-2) strengthens the endothelial cell BBB function by increased occludin and ZO-1 expression. In our model, LN-18 and NCI-H1299 cells secreted FGF-2, and a neutralization antibody to FGF-2 inhibited LN-18 cells enhanced BBB function. These results suggest that FGF-2 would be a novel therapeutic target for GBM in the perivascular invasive front.