Brain research bulletin
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Brain research bulletin · Nov 2011
Involvement of spinal cord BDNF in the generation and maintenance of chronic neuropathic pain in rats.
Brain-derived neurotrophic factor (BDNF) is involved in neuronal survival and synaptic plasticity of the central and peripheral nervous system. In chronic pain, plastic changes in dorsal horn neurons contribute to a phenomenon of hypersensitivity to pain sensation that is maintained over time, known as central sensitization. This process is accompanied by BDNF overexpression, but the role of BDNF in the generation and maintenance of the hyperalgesic phenomenon is still unclear. ⋯ Furthermore, the hyperalgesia generated was comparable to that observed in rats with a 42-day history of mononeuropathy. Increasing the dose or administering additional doses of BDNF resulted neither in additional effectiveness in reducing the pain threshold nor in the prolongation of the hyperalgesic effect, thus showing that central sensitization induced by BDNF is a dose-independent, all-or-none process. It is concluded that BDNF alone is sufficient for generating a long-lasting neural excitability change in the spinal cord via tyrosine kinase B receptor signaling, similar to that observed in chronic pain models such as neuropathy.
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Brain research bulletin · Nov 2011
Chemical stimulation of the ST36 acupoint reduces both formalin-induced nociceptive behaviors and spinal astrocyte activation via spinal alpha-2 adrenoceptors.
Spinal astrocytes have emerged as important mechanistic contributors to pathological and chronic pain. Recently, we have demonstrated that injection of diluted bee venom (DBV) into the Zusanli (ST36) acupoint produces a potent anti-nociceptive effect via the activation of spinal alpha-2 adrenoceptors. However, it is unclear if this anti-nociceptive effect is associated with alterations in spinal astrocytes. ⋯ These effects of DBV were prevented by intrathecal pretreatment with selective alpha-2A and alpha-2C adrenoceptor antagonists. Moreover, low dose intrathecal injection of FC in conjunction with low dose DBV injection into the ST36 acupoint synergistically suppressed pain responses and GFAP expression. These results demonstrate that DBV stimulation of the ST36 acupoint inhibits the formalin-induced activation of spinal astrocytes and nociceptive behaviors in this inflammatory pain model and this inhibition is associated with the activation of spinal alpha-2 adrenoceptors.
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Brain research bulletin · Nov 2011
Natriorexigenic effect of baclofen is reduced by AT₁ receptor blockade in the lateral parabrachial nucleus.
GABA(A) and GABA(B) receptors activation with agonists muscimol and baclofen, respectively in the lateral parabrachial nucleus (LPBN), induces water and hypertonic NaCl intake in rats. The purpose of this study was to examine the effects of previous injections of losartan (AT(1) angiotensin receptor antagonist) into the LPBN on 0.3M NaCl and water intake induced by baclofen injected bilaterally in the same area in fluid replete rats and in rats treated with the diuretic furosemide combined with a low dose of the angiotensin-converting enzyme inhibitor captopril injected subcutaneously. ⋯ In rats treated with furosemide+captopril, pre-treatment with losartan into the LPBN attenuated the increase in 0.3M NaCl intake (13.3 ± 3.2 vs. saline+baclofen: 24.3 ± 3.9 ml/180 min) and water intake (4.8 ± 2.1 vs. saline+baclofen: 19.5 ± 6.6 ml/180 min) produced by baclofen. We conclude that baclofen may produce a non-specific blockade of the inhibitory mechanisms of LPBN (deactivation of LPBN inhibitory mechanisms) and this blockade is facilitated by angiotensin II acting on AT(1) receptors in the LPBN, which drives rats to ingest large amounts of water and hypertonic NaCl independent if rats are fluid depleted or normohydrated.
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Brain research bulletin · Oct 2011
Electrical stimulation of olfactory bulb downregulates RGMa expression after ischemia/reperfusion injury in rats.
Repulsive guidance molecule A (RGMa) is associated with limited axonal growth after cerebral ischemia. This study focused on the effects of electrical stimulation of olfactory bulb (OB) on the expression of RGMa and axonal regeneration after focal cerebral ischemia/reperfusion injury. Sprague-Dawley (SD) rats were randomly divided into sham-operated group, ischemia/reperfusion (I/R) group (48h, 1 w), stimulation group (48h, 1 w), and sham-stimulated group (48h, 1 w). ⋯ The levels of RGMa were significantly elevated after ischemia/reperfusion injury. Stimulation treatment downregulated the expression of RGMa, reduced infarct volume and improved neurological function. These observations demonstrated that electrical stimulation of OB might promote axonal regeneration and function recovery after ischemic cerebral injury.
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Brain research bulletin · Oct 2011
Quercetin protects oligodendrocyte precursor cells from oxygen/glucose deprivation injury in vitro via the activation of the PI3K/Akt signaling pathway.
The aim of this study was to investigate the protection of quercetin (QUE) on oligodendrocyte precursor cells (OPCs) from oxygen/glucose deprivation (OGD)-induced injury in vitro and explore whether the PI3K/Akt signaling pathway contributed to the protection provided by quercetin. The OGD condition was induced by including 2mM sodium dithionite (Na(2)S(2)O(4)) in glucose-free DMEM medium. The concentration of QUE in this study ranged from 3μM to 81μM. ⋯ Western blotting showed that the expression levels of Bax and cleaved-caspase-3 proteins were down-regulated, while Bcl-2 and p-Akt were up-regulated. Further study showed that the increase in p-Akt by QUE was reduced by the PI3K inhibitor LY294002. These results indicated that QUE effectively protected OPCs from OGD-induced injury and that the mechanism might be related to the activation of the PI3K/Akt signaling pathway.