As shown in Fig

As shown in Fig. 4gh, we found no significant difference in the total distance traveled or average speed between the treated and the untreated mice, indicating that CRS, DMXBA, and -BGT had no effect on the locomotor activity of mice. == DMXBA alleviates CRS-induced neuronal damage in hippocampus == Neuronal damage in mouse hippocampal formations Autophinib after CRS was estimated by Nissl and Golgi staining (Fig. 5). alleviated CRS-induced depressive-like behavior, neuroinflammation, and neuronal damage, but these effects were abolished by the selective 7nAChR antagonist -bungarotoxin. Furthermore, activation of 7nAChRs restored the central cholinergic signaling function, inhibited TLR4-mediated inflammatory signaling and microglial activity, and increased the number of regulatory T cells in the hippocampus. == Conclusions == These findings provide evidence that 7nAChR activation mitigates CRS-induced neuroinflammation and cell death, suggesting that 7nAChRs could be a new therapeutic target for the prevention and treatment of depression. == Electronic supplementary material == The online version of this article (10. 1186/s12974-017-1007-2) contains supplementary Sele material, which is available to authorized users. Keywords: Chronic restraint stress, Nicotinic acetylcholine receptor, TLR4, Neuroinflammation, Depression == Background == Chronic mental and emotional stress are detrimental to physical and mental well-being and often cause affective disorders such as depression and anxiety [1]. It has been shown that chronic stress challenges are associated with an inflammatory response in brain that is characterized by toll-like receptor-4 (TLR4)/nuclear factor kappa B (NF-B) activation and release of proinflammatory cytokines [2, 3]. TLRs are pattern recognition receptors thought to mediate the innate immune response [4, 5]. Their expression is modulated rapidly in response to pathogens, a variety of cytokines, and environmental stress. Specifically, TLR4 regulates the adrenal response to stress and inflammatory stimuli as well as the brains response to stress [6]. TLR4 recruits adapter proteins, such as myeloid differentiation factor 88 (MyD88), and activates downstream signaling molecules, such as transcription factor nuclear factor kappa B (NF-B), to elicit production of multiple proinflammatory cytokines. Activation of Autophinib TLR4 complex may underlie the pathophysiology of many inflammatory diseases, such as depression, diabetes, obesity, chronic fatigue syndrome, and neuroinflammatory disorders [7]. Drugs and compounds that attenuate the TLR signaling pathway could represent new treatment possibilities for TLR4-mediated inflammatory disorders. The cholinergic system plays a crucial role in motor, cognitive, and affective processes, and also regulates central and peripheral inflammation [8, 9]. Acetylcholine interacts with nicotinic acetylcholine receptor 7 subunit (7nAChR) in tissue macrophages and other immune cells and inhibits the synthesis/release of tumor necrosis factor- (TNF-) and other inflammatory cytokines. This neural anti-inflammatory response, known as the cholinergic anti-inflammatory pathway, is fast and integrated through the central nervous system (CNS) [8]. 7nAChRs, composed of five identical 7 subunits, mainly regulate the cholinergic anti-inflammatory pathway by mediating peripheral macrophage activity [10]. In the CNS, both microglia and neurons express functional 7nAChRs. Indeed, stimulation of microglial 7nAChRs was shown to inhibit glial activation and decrease proinflammatory mediator expression and reactive oxygen species production [11, 12]. Dysregulation of cholinergic signaling has been implicated in multiple inflammatory disorders, including sepsis, myocardial or cerebral ischemia, cerebral hemorrhage, and Alzheimers disease [1216]. Autophinib Activation of the cholinergic system after brain injury might repair the CNS capacity to Autophinib control the exaggerated inflammation. Neuronal cell damage after chronic stress is observed predominantly in the hippocampus, a structure densely populated with 7nAChRs. Although the TLR4 proinflammatory pathway has been implicated in the development of chronic stress [2, 17], the roles of cholinergic signaling and 7nAChR-associated anti-inflammatory properties in chronic stress have not yet been examined. We therefore investigated whether chronic immobilization stress disrupts cholinergic function and activates the inflammatory responses, and whether treatment aimed at restoring 7nAChR function offers benefits by regulating inflammation and reducing neuronal death. == Methods == == Animals == Adult male Kunming mice (25 2 g) were obtained from the Center Autophinib for Experimental Animals, Huazhong University of Science and Technology, China. Animals were housed under standard laboratory conditions with a 12-h light/dark cycle and free access to food and water. All procedures were approved by the Institutional Animal Care and Use Committee at the Huazhong University of Science and Technology and conformed to the National Institutes of HealthGuide for the Care and Use of Laboratory Animals(approval number S634/2016). == Chronic restraint stress (CRS) procedure and assessment == Each mouse was restrained without access to food or water for 6 h per day (10: 00 to 16: 00) in a well-ventilated 50-mL conical Plexiglas tube for 21 days, as described previously [18]. During the restraint time, control animals were handled and stayed in their home cage without water or food. Animals were returned to their home cages after each period of restraint. An investigator without knowledge of the groups evaluated depressive-like behaviors with the sucrose preference test, tail suspension test, and forced swim test beginning 24 h after the last immobilization exposure. Each behavioral test was carried out on a different day. After behavioral.