Stress Affects Mast Cell Proteases in Murine Skin in a Model of Atopic Dermatitis-like Allergic Inflammation.

Stress exposure worsens allergic inflammatory diseases substantially. Mast cells (MCs) play a key role in peripheral immune responses to neuroendocrine stress mediators such as nerve growth factor (NGF) and substance P (SP). Mast cell proteases (MCPs) and cholinergic factors (Chrna7, SLURP1) were recently described to modulate MC stress response. We studied MCPs and Chrna7/SLURP1 and their interplay in a mouse model for noise induced stress (NiS) and atopic dermatitis-like allergic inflammation (AlD) and in cultured MC lacking Chrna7. We found that the cholinergic stress axis interacts with neuroendocrine stress mediators and stress-mediator cleaving enzymes in AlD. SP-cleaving mMCP4+ MC were upregulated in AlD and further upregulated by stress in NiS+AlD. Anti-NGF neutralizing antibody treatment blocked the stress-induced upregulation in vivo, and mMCP4+ MCs correlated with measures of AlD disease activity. Finally, high mMCP4 production in response to SP depended on Chrna7/SLURP1 in cultured MCs. In conclusion, mMCP4 and its upstream regulation by Chrna7/SLURP1 are interesting novel targets for the treatment of allergic inflammation and its aggravation by stress.

Protective effect of cholecalciferol against cobalt-induced neurotoxicity in rats: ZO-1/iFABP, ChAT/AchE and antioxidant pathways as potential therapeutic targets.

Cobalt (Co) toxicity has been reported to produce central nervous system and gastrointestinal abnormalities. This study assessed the therapeutic effect of cholecalciferol (Cho) supplementation against damages caused by sub-acute (14-day) cobalt chloride (CoCl2) exposure in the brain and intestines. Thirty-five male Wistar rats were divided equally into five groups: Group I (control) received no treatment; Group II received oral CoCl2 (100 mg/kg) only; Groups III, IV, and V received 1000, 3000 and 6000 IU/kg of cholecalciferol, respectively by oral gavage, and concurrently with CoCl2. Cobalt-treated rats showed neuronal vacuolation and presence of pyknotic nuclei in the cerebral cortex and hippocampus, depletion of Purkinje cells in the cerebellum, as well as inflammation and congestion in the intestinal mucosa. Cobalt also increased brain and intestinal hydrogen peroxide (H2O2) and malondialdehyde (MDA) concentrations, while simultaneously reducing glutathione (GSH) content, superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione S-transferase (GST) activities. Further, CoCl2 induced increases in brain acetylcholinesterase (AchE) activity and serum zonulin (ZO-1) levels. Conversely, Cho administration suppressed CoCl2-induced damages in the brain and intestines by reducing lipid peroxidation and increasing the activities of antioxidant enzymes. Remarkably, Cho produced stimulation of brain choline acetyltransferase (ChAT) and suppression of AchE activity, along with dose-dependent reduction in serum levels of ZO-1, intestinal fatty acid-binding protein (iFABP) and nitric oxide. In conclusion, the protective role of cholecalciferol against cobalt-induced toxicity occurred via modulation of cholinergic, intestinal permeability and antioxidant pathways. The results may prove significant in the context of the role of gut-brain connections in neuroprotection.

Potential effect of the non-neuronal cardiac cholinergic system on hepatic glucose and energy metabolism.

The vagus nerve belongs to the parasympathetic nervous system, which is involved in the regulation of organs throughout the body. Since the discovery of the non-neuronal cardiac cholinergic system (NNCCS), several studies have provided evidence for the positive role of acetylcholine (ACh) released from cardiomyocytes against cardiovascular diseases, such as sympathetic hyperreactivity-induced cardiac remodeling and dysfunction as well as myocardial infarction. Non-neuronal ACh released from cardiomyocytes is believed to regulate key physiological functions of the heart, such as attenuating heart rate, offsetting hypertrophic signals, maintaining action potential propagation, and modulating cardiac energy metabolism through the muscarinic ACh receptor in an auto/paracrine manner. Moreover, the NNCCS may also affect peripheral remote organs (e.g., liver) through the vagus nerve. Remote ischemic preconditioning (RIPC) and NNCCS activate the central nervous system and afferent vagus nerve. RIPC affects hepatic glucose and energy metabolism through the central nervous system and vagus nerve. In this review, we discuss the mechanisms and potential factors responsible for NNCCS in glucose and energy metabolism in the liver.

Non-neuronal cell-derived acetylcholine, a key modulator of the vascular endothelial function in health and disease.

Vascular endothelial cells play an important role in regulating peripheral circulation by modulating arterial tone in the microvasculature. Elevated intracellular Ca2+ levels are required in endothelial cells to induce smooth muscle relaxation via endothelium-dependent mechanisms such as nitric oxide production, prostacyclin, and endothelial cell hyperpolarization. It is well established that exogenous administration of acetylcholine can increase intracellular Ca2+ concentrations, followed by endothelium-dependent vasodilation. Although endogenous acetylcholine's regulation of vascular tone remains debatable, recent studies have reported that endogenously derived acetylcholine, but not neuronal cell-derived acetylcholine, is a key modulator of endothelial cell function. In this minireview, we summarize the current knowledge of the non-neuronal cholinergic system (NNCS) in vascular function, particularly vascular endothelial cell function, which contributes to blood pressure regulation. We also discuss the possible pathophysiological impact of endothelial NNCS, which may induce the development of vascular diseases due to endothelial dysfunction, and the potential of endothelial NNCS as a novel therapeutic target for endothelial dysfunction in the early stages of metabolic syndrome, diabetes, and hypertension.

Expression and function of nicotinic acetylcholine receptors in specific neuronal populations: Focus on striatal and prefrontal circuits.

Nicotinic acetylcholine receptors (nAChRs) are widely expressed in the central nervous system and play an important role in the control of neural functions including neuronal activity, transmitter release and synaptic plasticity. Although the common subtypes of nAChRs are abundantly expressed throughout the brain, their expression in different brain regions and by individual neuronal types is not homogeneous or incidental. In recent years, several studies have emerged showing that particular subtypes of nAChRs are expressed by specific neuronal populations in which they have major influence on the activity of local circuits and behavior. It has been demonstrated that even nAChRs expressed by relatively rare neuronal types can induce significant changes in behavior and contribute to pathological processes. Depending on the identity and connectivity of the particular nAChRs-expressing neuronal populations, the activation of nAChRs can have distinct or even opposing effects on local neuronal signaling. In this review, we will summarize the available literature describing the expression of individual nicotinic subunits by different neuronal types in two crucial brain regions, the striatum and the prefrontal cortex. The review will also briefly discuss nicotinic expression in non-neuronal, glial cells, as they cannot be ignored as potential targets of nAChRs-modulating drugs. The final section will discuss options that could allow us to target nAChRs in a neuronal-type-specific manner, not only in the experimental field, but also eventually in clinical practice.

Phase synchrony between prefrontal noradrenergic and cholinergic signals indexes inhibitory control.

Inhibitory control is a critical executive function that allows animals to suppress their impulsive behavior in order to achieve certain goals or avoid punishment. We investigated norepinephrine (NE) and acetylcholine (ACh) dynamics and population neuronal activity in the prefrontal cortex during inhibitory control. Using fluorescent sensors to measure extracellular levels of NE and ACh, we simultaneously recorded the dynamics of prefrontal NE and ACh in mice performing an inhibitory control task. The prefrontal NE and ACh signals exhibited strong coherence at 0.4-0.8 Hz. Chemogenetic inhibition of locus coeruleus (LC) neurons that project to the basal forebrain region reduced inhibitory control performance to chance levels. However, this manipulation did not diminish the difference in NE/ACh signals between successful and failed trials; instead, it abolished the difference in NE-ACh phase synchrony between the successful and failed trials, indicating that NE-ACh phase synchrony is a task-relevant neuromodulatory feature. Chemogenetic inhibition of cholinergic neurons that project to the LC region did not impair the inhibitory control performance, nor did it abolish the difference in NE-ACh phase synchrony between successful or failed trials, further confirming the relevance of NE-ACh phase synchrony to inhibitory control. To understand the possible effect of NE-ACh synchrony on prefrontal population activity, we employed Neuropixels to record from the prefrontal cortex with and without inhibiting LC neurons that project to the basal forebrain during inhibitory control. The LC inhibition reduced the number of prefrontal neurons encoding inhibitory control. Demixed principal component analysis (dPCA) further revealed that population firing patterns representing inhibitory control were impaired by the LC inhibition. Disparities in NE-ACh phase synchrony relevant to inhibitory control occurred only in the prefrontal cortex, but not in the parietal cortex, somatosensory cortex, and the somatosensory thalamus. Taken together, these findings suggest that the LC modulates inhibitory control through its collective effect with cholinergic systems on population activity in the prefrontal cortex. Our results further revealed that NE-ACh phase synchrony is a critical neuromodulatory feature with important implications for cognitive control.

Eucommia ulmoides Leaves Alleviate Cognitive Dysfunction in Dextran Sulfate Sodium (DSS)-Induced Colitis Mice through Regulating JNK/TLR4 Signaling Pathway.

Ulcerative colitis (UC) is one of the inflammatory bowel diseases (IBD) that is characterized by systemic immune system activation. This study was performed to assess the alleviative effect of administering an aqueous extract of Eucommia ulmoides leaves (AEEL) on cognitive dysfunction in mice with dextran sulfate sodium (DSS)-induced colitis. The major bioactive compounds of AEEL were identified as a quinic acid derivative, caffeic acid-O-hexoside, and 3-O-caffeoylquinic acid using UPLC Q-TOF/MSE. AEEL administration alleviated colitis symptoms, which are bodyweight change and colon shortening. Moreover, AEEL administration protected intestinal barrier integrity by increasing the tight junction protein expression levels in colon tissues. Likewise, AEEL improved behavioral dysfunction in the Y-maze, passive avoidance, and Morris water maze tests. Additionally, AEEL improved short-chain fatty acid (SCFA) content in the feces of DSS-induced mice. In addition, AEEL improved damaged cholinergic systems in brain tissue and damaged mitochondrial and antioxidant functions in colon and brain tissues caused by DSS. Also, AEEL protected against DSS-induced cytotoxicity and inflammation in colon and brain tissues by c-Jun N-terminal kinase (JNK) and the toll-like receptor 4 (TLR4) signaling pathway. Therefore, these results suggest that AEEL is a natural material that alleviates DSS-induced cognitive dysfunction with the modulation of gut-brain interaction.

Neuroprotection of Cholinergic Neurons with a Tau Aggregation Inhibitor and Rivastigmine in an Alzheimer's-like Tauopathy Mouse Model.

Basal forebrain cholinergic dysfunction, most likely linked with tau protein aggregation, is a characteristic feature of Alzheimer's disease (AD). Recent evidence suggests that tau protein is a putative target for the treatment of dementia, and the tau aggregation inhibitor, hydromethylthionine mesylate (HMTM), has emerged as a potential disease-modifying treatment. However, its efficacy was diminished in patients already receiving approved acetylcholinesterase inhibitors. In this study, we ask whether this negative interaction can also be mimicked in experimental tau models of AD and whether the underlying mechanism can be understood. From a previous age profiling study, 6-month-old line 1 (L1) tau transgenic mice were characterized by a severe reduction in several cholinergic markers. We therefore assessed whether long-term pre-exposure with the acetylcholinesterase inhibitor rivastigmine alone and in conjunction with the tau aggregation inhibitor HMTM can reverse cholinergic deficits in L1. Rivastigmine and HMTM, and combinations of the two compounds were administered orally for 11 weeks to both L1 and wild-type mice. The brains were sectioned with a focus on the basal forebrain, motor cortex and hippocampus. Immunohistochemical staining and quantification of choline acetyltransferase (ChAT), tyrosine kinase A (TrkA)-positive neurons and relative optical intensity (ROI) for vesicular acetylcholine transporter (VAChT), and acetylcholinesterase (AChE) reactivity confirmed reversal of the diminished cholinergic phenotype of interneurons (nucleus accumbens, striatum) and projection neurons (medial septum, nucleus basalis magnocellularis) by HMTM, to a greater extent than by rivastigmine alone in L1 mice. Combined administration did not yield additivity but, in most proxies, led to antagonistic effects in which rivastigmine decreased the benefits shown with HMTM alone. Local markers (VAChT and AChE) in target structures of the basal forebrain, motor cortex and hippocampal CA3 seemed to be normalized by HMTM, but not by rivastigmine or the combination of both drugs. HMTM, which was developed as a tau aggregation inhibitor, strongly decreased the tau load in L1 mice, however, not in combination with rivastigmine. Taken together, these data confirm a cholinergic phenotype in L1 tau transgenic mice that resembles the deficits observed in AD patients. This phenotype is reversible by HMTM, but at the same time appears to be subject to a homeostatic regulation induced by chronic pre-treatment with an acetylcholinesterase inhibitor, which interferes with the efficacy of HMTM. The strongest phenotypic reversal coincided with a normalization of the tau load in the cortex and hippocampus of L1, suggesting that tau accumulation underpins the loss of cholinergic markers in the basal forebrain and its projection targets.

Non-neuronal cholinergic system in the heart influences its homeostasis and an extra-cardiac site, the blood-brain barrier.

The non-neuronal cholinergic system of the cardiovascular system has recently gained attention because of its origin. The final product of this system is acetylcholine (ACh) not derived from the parasympathetic nervous system but from cardiomyocytes, endothelial cells, and immune cells. Accordingly, it is defined as an ACh synthesis system by non-neuronal cells. This system plays a dispensable role in the heart and cardiomyocytes, which is confirmed by pharmacological and genetic studies using murine models, such as models with the deletion of vesicular ACh transporter gene and modulation of the choline acetyltransferase (ChAT) gene. In these models, this system sustained the physiological function of the heart, prevented the development of cardiac hypertrophy, and negatively regulated the cardiac metabolism and reactive oxygen species production, resulting in sustained cardiac homeostasis. Further, it regulated extra-cardiac organs, as revealed by heart-specific ChAT transgenic (hChAT tg) mice. They showed enhanced functions of the blood-brain barrier (BBB), indicating that the augmented system influences the BBB through the vagus nerve. Therefore, the non-neuronal cardiac cholinergic system indirectly influences brain function. This mini-review summarizes the critical cardiac phenotypes of hChAT tg mice and focuses on the effect of the system on BBB functions. We discuss the possibility that a cholinergic signal or vagus nerve influences the expression of BBB component proteins to consolidate the barrier, leading to the downregulation of inflammatory responses in the brain, and the modulation of cardiac dysfunction-related effects on the brain. This also discusses the possible interventions using the non-neuronal cardiac cholinergic system.

The role of the cholinergic system in the memory-protecting effects of metformin in a model of scopolamine-induced memory impairment in aged rats.

PURPOSE: As the elderly population grows, the prevalence of dementia is also rapidly increasing worldwide. Metformin, an antidiabetic drug, has been shown to have ameliorative effects on impaired cognitive functions in experimental models. However, studies have generally used young animals. Additionally, although it has a major role in Alzheimer's disease (AD) and memory, literature information about the effects of metformin on the cholinergic system is limited. In this study, we investigated the effects of metformin on memory in a model of scopolamine-induced memory impairment in aged rats. We also examined the effects of metformin on the cholinergic system, which is very important in cognitive functions. METHODS: Metformin was administered orally to male Wistar rats (20-22 months old) at 100 mg/kg/day for three weeks. Morris water maze (MWM) tests were performed to assess spatial memory. Before the probe test of the MWM test, scopolamine was injected intraperitoneally at a dose of 1 mg/kg. After testing, animals were sacrificed, whole brains were removed, and hippocampus samples were separated for biochemical analysis. RESULTS: Impaired memory associated with scopolamine administration was reversed by metformin. In addition, metformin administration ameliorated scopolamine-induced changes in acetylcholine (ACh) levels, acetylcholinesterase (AChE), butyrylcholinesterase (BuChE), and choline acetyltransferase (ChAT) activity. CONCLUSION: Our results show that metformin may have protective effects in a scopolamine-induced memory impairment model in aged animals by improving cholinergic function. Metformin shows promise in preventing dementia with its dual cholinesterase inhibition and ChAT activation effect.

A comprehensive assessment of the cholinergic-supporting and cognitive-enhancing effects of Rosa damascena Mill. (Damask rose) essential oil on scopolamine-induced amnestic rats.

INTRODUCTION: Alzheimer's disease (AD) is a neurodegenerative condition characterized by gradual loss of cognitive abilities (dementia) and is a major public health problem. Here, we aimed at investigating the effects of Rosa damascena essential oil (RDEO) on learning and memory functions in a rat model of amnesia induced by scopolamine, as well as on changes in acetylcholinesterase (AChE) activity, M1 muscarinic acetylcholine receptor (mAChR) expression, and brain-derived neurotrophic factor (BDNF) levels in the extracted brain tissues. METHODS: The control, amnesia (scopolamine, 1 mg/kg/i.p.) and treatment (RDEO, 100 µL/kg/p.o. or galantamine, 1.5 mg/kg/i.p.) groups were subjected to Morris water maze and new object recognition tests. AChE activity was assayed by ELISA, and M1 mAChR and BDNF concentration changes were determined by western blotting. Also, using computational tools, human M1 mAChR was modeled in an active conformation, and the major components of RDEO were docked onto this receptor. RESULTS: According to our behavioral tests, RDEO was able to mitigate the learning and memory impairments caused by scopolamine in vivo. Our in vitro assays showed that the observed positive effects correlated well with a decrease in AChE activity and an increase in M1 mAChR and BDNF levels in amnestic rat brains. We also demonstrated in an in silico setting that the major components of RDEO, specifically -citronellol, geraniol, and nerol, could be accommodated favorably within the allosteric binding pocket of active-state human M1 mAChR and anchored here chiefly by hydrogen-bonding and alkyl-π interactions. CONCLUSION: Our findings offer a solid experimental foundation for future RDEO-based medicinal product development for patients suffering from AD.

Contributions of Non-Neuronal Cholinergic Systems to the Regulation of Immune Cell Function, Highlighting the Role of α7 Nicotinic Acetylcholine Receptors.

Loewi's discovery of acetylcholine (ACh) release from the frog vagus nerve and the discovery by Dale and Dudley of ACh in ox spleen led to the demonstration of chemical transmission of nerve impulses. ACh is now well-known to function as a neurotransmitter. However, advances in the techniques for ACh detection have led to its discovery in many lifeforms lacking a nervous system, including eubacteria, archaea, fungi, and plants. Notably, mRNAs encoding choline acetyltransferase and muscarinic and nicotinic ACh receptors (nAChRs) have been found in uninnervated mammalian cells, including immune cells, keratinocytes, vascular endothelial cells, cardiac myocytes, respiratory, and digestive epithelial cells. It thus appears that non-neuronal cholinergic systems are expressed in a variety of mammalian cells, and that ACh should now be recognized not only as a neurotransmitter, but also as a local regulator of non-neuronal cholinergic systems. Here, we discuss the role of non-neuronal cholinergic systems, with a focus on immune cells. A current focus of much research on non-neuronal cholinergic systems in immune cells is α7 nAChRs, as these receptors expressed on macrophages and T cells are involved in regulating inflammatory and immune responses. This makes α7 nAChRs an attractive potential therapeutic target.

Endogenous Cholinergic System Involved in Peripheral Analgesic Control in Mice Is Activated by TNF-α, CXCL-1, and IL-1ß.

INTRODUCTION: Tissue injury results in the release of inflammatory mediators, including a cascade of algogenic substances, which contribute to the development of hyperalgesia. During this process, endogenous analgesic substances are peripherally released to counterbalance hyperalgesia. The present study aimed to investigate whether inflammatory mediators TNF-α, IL-1ß, CXCL1, norepinephrine (NE), and prostaglandin E2 (PGE2) may be involved in the deflagration of peripheral endogenous modulation of inflammatory pain by activation of the cholinergic system. METHODS: Male Swiss mice were subjected to paw withdrawal test. All the substances were injected via the intraplantar route. RESULTS: The main findings of this study were as follows: (1) carrageenan (Cg), TNF-α, CXCL-1, IL1-ß, NE, and PGE2 induced hyperalgesia; (2) the acetylcholinesterase enzyme inhibitor, neostigmine, reversed the hyperalgesia observed after Cg, TNF-α, CXCL-1, and IL1-ß injection; (3) the non-selective muscarinic receptor antagonist, atropine, and the selective muscarinic type 1 receptor (m1AChr) antagonist, telenzepine, potentiated the hyperalgesia induced by Cg and CXCL-1; (4) mecamylamine, a non-selective nicotinic receptor antagonist, potentiated the hyperalgesia induced by Cg, TNF-α, CXCL-1, and IL1-ß; (5) Cg, CXCL-1, and PGE2 increased the expression of the m1AChr and nicotinic receptor subunit α4protein. CONCLUSION: These results suggest that the cholinergic system may modulate the inflammatory pain induced by Cg, PGE2, TNF-α, CXCL-1, and IL1-ß.

α4 nicotinic receptors on GABAergic neurons mediate a cholinergic analgesic circuit in the substantia nigra pars reticulata.

Nicotinic acetylcholine receptors (nAChRs) regulate pain pathways with various outcomes depending on receptor subtypes, neuron types, and locations. But it remains unknown whether α4ß2 nAChRs abundantly expressed in the substantia nigra pars reticulata (SNr) have potential to mitigate hyperalgesia in pain states. We observed that injection of nAChR antagonists into the SNr reduced pain thresholds in naïve mice, whereas injection of nAChR agonists into the SNr relieved hyperalgesia in mice, subjected to capsaicin injection into the lower hind leg, spinal nerve injury, chronic constriction injury, or chronic nicotine exposure. The analgesic effects of nAChR agonists were mimicked by optogenetic stimulation of cholinergic inputs from the pedunculopontine nucleus (PPN) to the SNr, but attenuated upon downregulation of α4 nAChRs on SNr GABAergic neurons and injection of dihydro-ß-erythroidine into the SNr. Chronic nicotine-induced hyperalgesia depended on α4 nAChRs in SNr GABAergic neurons and was associated with the reduction of ACh release in the SNr. Either activation of α4 nAChRs in the SNr or optogenetic stimulation of the PPN-SNr cholinergic projection mitigated chronic nicotine-induced hyperalgesia. Interestingly, mechanical stimulation-induced ACh release was significantly attenuated in mice subjected to either capsaicin injection into the lower hind leg or SNI. These results suggest that α4 nAChRs on GABAergic neurons mediate a cholinergic analgesic circuit in the SNr, and these receptors may be effective therapeutic targets to relieve hyperalgesia in acute and chronic pain, and chronic nicotine exposure.

Oxidized/unmodified-polyethylene microplastics neurotoxicity in mice: Perspective from microbiota-gut-brain axis.

Microplastics (MPs) are inevitably oxidized in the environment, and their potential toxicity to organisms has attracted wide attention. However, the neurotoxicity and mechanism of oxidized polyethylene (Ox-PE) MPs to organisms remain unclear. Herein, we prepared oxidized low-density polyethylene (Ox-LDPE) and established a model of MPs exposure by continuously orally gavage of C57BL/6 J mice with LDPE-MPs/Ox-LDPE-MPs for 28 days with or without oral administration of Lactobacillus plantarum DP189 and galactooligosaccharides (DP189&GOS). The experimental results indicated that LDPE-MPs or Ox-LDPE-MPs caused several adverse effects in mice, mainly manifested by behavioral changes, disruption of the intestinal and blood-brain barrier (BBB), and simultaneous oxidative stress, inflammatory reactions, and pathological damage in the brain and intestines. Brain transcriptomic analysis revealed that the cholinergic synaptic signaling pathways, which affect cognitive function, were significantly disrupted after exposure to LDPE-MPs or Ox-LDPE-MPs. Real-time quantitative polymerase chain reaction and Western Blotting results further demonstrated that the critical genes (Slc5a7, Chat and Slc18a3) and proteins (Chat and Slc18a3) in the cholinergic synaptic signaling pathway were significantly down-regulated after exposure to LDPE-MPs or Ox-LDPE-MPs. These alterations lead to reduced acetylcholine concentration, which causes cognitive dysfunction in mice. Importantly, the DP189&GOS interventions effectively mitigated the MPs-induced cognitive dysfunction and intestinal microbiota alteration, improved intestinal and BBB integrity, attenuated the oxidative stress and inflammatory response, and also saw a rebound in the release of acetylcholine. These results indicated that LDPE-MPs and Ox-LDPE-MPs exert neurotoxic effects on mice by inducing oxidative stress, inflammatory responses, and dysregulation of cholinergic signaling pathways in the mouse brain. That probiotic supplementation is effective in attenuating MPs-induced neurotoxicity in mice. Overall, this study reveals the potential mechanisms of neurotoxicity of LDPE-MPs and Ox-LDPE-MPs on mice and their improvement measures, necessary to assess the potential risks of plastic contaminants to human health.

Interaction of acetylcholine and oxytocin neuromodulation in the hippocampus.

A postulated role of subcortical neuromodulators is to control brain states. Mechanisms by which different neuromodulators compete or cooperate at various temporal scales remain an open question. We investigated the interaction of acetylcholine (ACh) and oxytocin (OXT) at slow and fast timescales during various brain states. Although these neuromodulators fluctuated in parallel during NREM packets, transitions from NREM to REM were characterized by a surge of ACh but a continued decrease of OXT. OXT signaling lagged behind ACh. High ACh was correlated with population synchrony and gamma oscillations during active waking, whereas minimum ACh predicts sharp-wave ripples (SPW-Rs). Optogenetic control of ACh and OXT neurons confirmed the active role of these neuromodulators in the observed correlations. Synchronous hippocampal activity consistently reduced OXT activity, whereas inactivation of the lateral septum-hypothalamus path attenuated this effect. Our findings demonstrate how cooperative actions of these neuromodulators allow target circuits to perform specific functions.

Dual role of α7 nicotinic acetylcholine receptors in the retrosplenial cortex for aversive memory acquisition and retrieval.

In the retrosplenial cortex (RSC), the role of cholinergic modulation via α7 nicotinic receptors and their involvement in memory is unknown. In recent years, the RSC has been shown to deteriorate in the early stages of Alzheimer's disease (AD). Likewise, the cholinergic system has been postulated as one of those responsible for cognitive impairment in patients with AD. Great interest has arisen in the study of α7 nicotinic receptors as more specific targets for the treatment of this disease. For this reason, we aim to study the role of α7 receptors of the RSC in memory processing. We infused a selective α7 receptor antagonist into the anterior part of the RSC (aRSC) to assess its role in different phases of aversive memory processing using an inhibitory avoidance task. We found that α7 nicotinic receptors are involved in memory acquisition and expression, but not in its consolidation. These results identify aRSC α7 nicotinic receptors as key players in aversive memory processing and highlight their significant potential as therapeutic targets for Alzheimer's disease.

M1 cholinergic signaling in the brain modulates cytokine levels and splenic cell sub-phenotypes following cecal ligation and puncture.

BACKGROUND: The contribution of the central nervous system to sepsis pathobiology is incompletely understood. In previous studies, administration of endotoxin to mice decreased activity of the vagus anti-inflammatory reflex. Treatment with the centrally-acting M1 muscarinic acetylcholine (ACh) receptor (M1AChR) attenuated this endotoxin-mediated change. We hypothesize that decreased M1AChR-mediated activity contributes to inflammation following cecal ligation and puncture (CLP), a mouse model of sepsis. METHODS: In male C57Bl/6 mice, we quantified basal forebrain cholinergic activity (immunostaining), hippocampal neuronal activity, serum cytokine/chemokine levels (ELISA) and splenic cell subtypes (flow cytometry) at baseline, following CLP and following CLP in mice also treated with the M1AChR agonist xanomeline. RESULTS: At 48 h. post-CLP, activity in basal forebrain cells expressing choline acetyltransferase (ChAT) was half of that observed at baseline. Lower activity was also noted in the hippocampus, which contains projections from ChAT-expressing basal forebrain neurons. Serum levels of TNFα, IL-1ß, MIP-1α, IL-6, KC and G-CSF were higher post-CLP than at baseline. Post-CLP numbers of splenic macrophages and inflammatory monocytes, TNFα+ and ILß+ neutrophils and ILß+ monocytes were higher than baseline while numbers of central Dendritic Cells (cDCs), CD4+ and CD8+ T cells were lower. When, following CLP, mice were treated with xanomeline activity in basal forebrain ChAT-expressing neurons and in the hippocampus was significantly higher than in untreated animals. Post-CLP serum concentrations of TNFα, IL-1ß, and MIP-1α, but not of IL-6, KC and G-CSF, were significantly lower in xanomeline-treated mice than in untreated mice. Post-CLP numbers of splenic neutrophils, macrophages, inflammatory monocytes and TNFα+ neutrophils also were lower in xanomeline-treated mice than in untreated animals. Percentages of IL-1ß+ neutrophils, IL-1ß+ monocytes, cDCs, CD4+ T cells and CD8+ T cells were similar in xanomeline-treated and untreated post-CLP mice. CONCLUSION: Our findings indicate that M1AChR-mediated responses modulate CLP-induced alterations in serum levels of some, but not all, cytokines/chemokines and affected splenic immune response phenotypes.