Neuropharmacology
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Pro-inflammatory cytokines are implicated in the pathogenesis of depression. However, few animal models of cytokine-induced depression well characterized regarding its response to antidepressants are available. Hence, the aim of this study was to propose a model of depressive-like behavior induced by the administration of tumor necrosis factor-α (TNF-α) responsive to antidepressant treatments. ⋯ In addition, TNF-α (0.1 fg/site, i.c.v.) administration produced an anhedonic response in a sucrose intake test, which was prevented by anti-TNF-α antibody (0.01 pg/site, i.c.v) or fluoxetine (32 mg/kg, i.p). Taken together, these results indicate that TNF-α produces a depressive-like state in mice, reinforcing the notion that an inflammatory component may play an important role in the pathophysiology of depression and suggesting that the central administration of TNF-α may be a novel approach to study the inflammatory component of depressive disorder. This article is part of a Special Issue entitled 'Anxiety and Depression'.
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Positive allosteric modulators (PAMs) of nicotinic acetylcholine receptors (nAChRs) have attracted considerable interest as a novel area of therapeutic drug discovery. Two types of α7-selective PAMs have been identified (type I and type II). Whilst both potentiate peak agonist-induced responses, they have different effects on the rate of agonist-induced receptor desensitization. ⋯ Functional characterization of a series of mutated α7 nAChRs indicates that mutation of amino acids within a proposed intrasubunit transmembrane cavity have a broadly similar effect on these two PAMs. In addition, we have employed a functional assay designed to examine the ability of ligands to act competitively at either the orthosteric or allosteric binding site of α7 nAChRs. These data, together with computer docking simulations, lead us to conclude that both the type I PAM NS1738 and the type II PAM PNU-120596 bind competitively at a mutually exclusive intrasubunit transmembrane site.
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Dichlorvos is a synthetic insecticide that belongs to the family of chemically related organophosphate (OP) pesticides. It can be released into the environment as a major degradation product of other OPs, such as trichlorfon, naled, and metrifonate. Dichlorvos exerts its toxic effects in humans and animals by inhibiting neural acetylcholinesterase. ⋯ In addition, MitoQ also suppressed DNA fragmentation, cyt c release and caspase-3 activity in dichlorvos treated rats compared to the control group. Further electron microscopic studies revealed that MitoQ attenuates dichlorvos induced mitochondrial swelling, loss of cristae and chromatin condensation. These results indicate that MitoQ may be beneficial against OP (dichlorvos) induced neurodegeneration.
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Post-operative cognitive dysfunction (POCD) is a clinical phenomenon characterized with cognitive decline in patients after anesthesia and surgery. It has been shown that interleukin-1β (IL-1β) contributes to the cognitive impairment of mice after surgery and isoflurane anesthesia. This study is designed to determine whether isoflurane alone increases inflammatory cytokines and causes cell injury and cognitive impairment. ⋯ Isoflurane also increased activated caspase 3 in the hippocampus and decreased the neuronal density in the CA1 region. However, isoflurane did not change the amount of β-amyloid peptide in the cerebral cortex at 29 days after isoflurane exposure when cognitive impairment was present. These results suggest that isoflurane increases inflammatory cytokine expression and causes cell injury in the hippocampus, which may contribute to isoflurane-induced cognitive impairment in rats.
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Alzheimer's disease (AD) is a neurodegenerative disorder with progressive memory loss. It has been shown that the cholinergic neurotransmission deficit is one of the neurochemical characteristics of AD, and that L-arginine and its metabolites also play a prominent role in AD pathogenesis. Scopolamine, a non-selective muscarinic receptor antagonist, blocks cholinergic neurotransmission and impairs behavioural function, including learning and memory. ⋯ There were significantly decreased NOS activity, increased arginase activity, and increased L-ornithine and putrescine levels in the DG, but not other regions examined, in the scopolamine treated rats as compared to the controls. These findings suggest that scopolamine impairs behavioural function and alters L-arginine metabolism in the DG sub-region of the hippocampus specifically. The underlying mechanisms of it remain to be explored further.