Neuropharmacology
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Recent in vivo studies have shown that erythropoietin (EPO) offers strong protection against brain edema. However, the intracellular and molecular mechanisms behind this beneficial effect have not been specified. The aim of this study was to determine whether human erythropoietin (rhEPO) reduces the astrocytic swelling created by oxygen-glucose deprivation followed by reoxygenation (OGD/Reox) in vitro and whether this effect can be mediated through the modulation of aquaporin4 (AQP4) expression in the plasma membrane (PM) and phosphorylation of the mitogen-activated protein kinase pathway (MAPK) pathway. ⋯ Furthermore, the over-activation of these MAPK after OGD/Reox was attenuated by rhEPO treatment significantly. In conclusion, our data strongly suggest that rhEPO can protect astrocytes from swelling caused by ischemia and reperfusion-like injury. This neuroprotective capacity is partially mediated by diminishing the MAPK-activity-dependent overabundance of AQP4 in PM.
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The development of novel therapeutic agents for disorders of cognition such as Alzheimer's disease (AD) is of paramount importance given the ever-increasing elderly population, however; there is also considerable interest in any strategy that might enhance the clinical efficacy of currently available treatments. The purpose of this study was to evaluate an adjunctive treatment strategy to memory enhancement, namely combining the commonly prescribed acetylcholinesterase inhibitor (AChEI) donepezil, with a positive allosteric modulator (PAM) of α7 nicotinic-acetylcholine receptors (α7-nAChRs), PNU-120596. The treatment strategy was evaluated in a (non-spatial) spontaneous novel object recognition (NOR) task in young rats; a water maze spatial learning and recall procedure in aged, cognitively-impaired rats, and a delayed match to sample (working/short term memory) task in aged rhesus monkeys. ⋯ The positive effect of the drug combination appeared to be α7-nAChR mediated given that it was blocked in the NOR task by the selective α7-nAChR antagonist methyllycaconitine (MLA). Collectively, these data indicate that PNU-120596 increases the effective dose range of donepezil in learning/memory-related tasks in young and age-impaired animal models. The results suggest that α7-nAChR-selective PAMs like PNU-120596 have potential as adjunctive treatments with acetylcholinesterase inhibitors (e.g., donepezil) for age-related illnesses such as AD as well memory disorders not necessarily associated with advanced age.
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Traumatic brain injury (TBI) evokes an intense neuroinflammatory reaction that is essentially mediated by activated microglia and that has been reported to act as a secondary injury mechanism that further promotes neuronal death. It involves the excessive production of inflammatory cytokines and the diminution of neuroprotective and neurotrophic factors, such as the soluble form alpha of the amyloid precursor protein (sAPPα), generated by the activity of α-secretases. Hence, the aim of this study was to examine the effects of etazolate, an α-secretase activator, on acute and belated post-TBI consequences. ⋯ A single administration of etazolate exerted a dose-dependent anti-inflammatory and anti-œdematous effect accompanied by lasting memory improvement, reduction of locomotor hyperactivity and olfactory bulb tissue protection, with a therapeutic window of at least 2 h. These effects were associated with the restoration of the levels of the sAPPα protein post-TBI. Taken together, these results highlight for the first time the therapeutic interest of an α-secretase activator in TBI.
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Excessive N-Methyl-d-aspartate receptor (NMDAR)-dependent production of nitric oxide (NO) is involved in the development and maintenance of chronic pain states, and is mediated by postsynaptic density protein-95 (PSD-95). By binding to both the NMDAR and neuronal NO synthase (nNOS), PSD-95 mediates a specific coupling between NMDAR activation and NO production. NMDAR antagonism shows anti-nociceptive action in humans and animal models of chronic pain but is associated with severe disturbances of cognitive and motor functions. ⋯ At the dose reducing hypersensitivity, MK-801 disrupted attention, long-term memory, and motor performance. By contrast, even high doses of UCCB01-125 were devoid of side-effects in these tests. The data suggest that PSD-95 inhibition is a feasible strategy to prevent both development and maintenance of chronic inflammatory pain, while avoiding NMDAR antagonism-related side-effects.
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We have demonstrated that the activation of P2X3 receptor on peripheral afferent neurons is critical to development of inflammatory hyperalgesia in peripheral tissue, although pharmacological administration of prostaglandin E(2) or sympathomimetic amines is enough to sensitize primary afferent neurons by acting directly in neuronal receptors. Therefore, to clarify this ambiguity this study verifies whether P2X3 receptor activation on primary afferent neurons enables the sensitization induced by prostaglandin E(2) or sympathomimetic amine. ⋯ Furthermore, because PKCɛ translocation induces an increase of neuronal susceptibility to inflammatory mediators, this study demonstrates that αβmeATP in peripheral tissue increases the expression of PKCɛ in cell membranes of DRG-L5, and in contrast, the administration of PKCɛ translocation inhibitor (1 μg/paw) in peripheral tissue 45 min before αβmeATP, prevented the hyperalgesia induced by sub-threshold dose of PGE(2) (4 ng/paw). In conclusion, this study suggests that neuronal P2X3 receptor activation and the consequent PKCɛ translocation increase the susceptibility of nociceptor to inflammatory mediators allowing the development of inflammatory hyperalgesia.