Design, Synthesis, and Insecticidal Activity of Pyridino[1,2-a]pyrimidines Containing Indole Moeites at the 1-Position.

Research on mesoionic structures in pesticide design has gained significant attention in recent years. However, the 1-position of pyridino[1,2-a]pyrimidine is usually designed with 2-chlorothiazole, 2-chloropyridine, or cyano moieties commonly found in neonicotinoid insecticides. In order to enrich the available pharmacophore library, here, we disclose a series of new pyridino[1,2-a]pyrimidine mesoionics bearing indole-containing substituents at the 1-position. Most of these target compounds are confirmed to have good insecticidal activity against aphids through bioevaluation. In addition, a three-dimensional structure-activity relationship model is established to allow access to optimal compound F45 with an LC50 value of 2.97 mg/L. This value is comparable to the property achieved by the positive control triflumezopyrim (LC50 = 2.94 mg/L). Proteomics and molecular docking analysis suggest that compound F45 has the potential to modulate the functioning of the aphid nervous system through its interaction with neuronal nicotinic acetylcholine receptors. This study expands the existing pharmacophore library for the future development of new mesoionic insecticides based on 1-position modifications of the pyridino[1,2-a]pyrimidine scaffold.

New Pyridyl and Dihydroisoquinoline Alkaloids Isolated from the Chevron Nemertean Amphiporus angulatus.

Nemertean worms contain toxins that are used to paralyze their prey and to deter potential predators. Hoplonemerteans often contain pyridyl alkaloids like anabaseine that act through nicotinic acetylcholine receptors and crustacean chemoreceptors. The chemical reactivity of anabaseine, the first nemertean alkaloid to be identified, has been exploited to make drug candidates selective for alpha7 subtype nAChRs. GTS-21, a drug candidate based on the anabaseine scaffold, has pro-cognitive and anti-inflammatory actions in animal models. The circumpolar chevron hoplonemertean Amphiporus angulatus contains a multitude of pyridyl compounds with neurotoxic, anti-feeding, and anti-fouling activities. Here, we report the isolation and structural identification of five new compounds, doubling the number of pyridyl alkaloids known to occur in this species. One compound is an isomer of the tobacco alkaloid anatabine, another is a unique dihydroisoquinoline, and three are analogs of the tetrapyridyl nemertelline. The structural characteristics of these ten compounds suggest several possible pathways for their biosynthesis.

The Cyclic Imine Core Common to the Marine Macrocyclic Toxins Is Sufficient to Dictate Nicotinic Acetylcholine Receptor Antagonism.

Macrocyclic imine phycotoxins are an emerging class of chemical compounds associated with harmful algal blooms and shellfish toxicity. Earlier binding and electrophysiology experiments on nAChR subtypes and their soluble AChBP surrogates evidenced common trends for substantial antagonism, binding affinities, and receptor-subtype selectivity. Earlier, complementary crystal structures of AChBP complexes showed that common determinants within the binding nest at each subunit interface confer high-affinity toxin binding, while distinctive determinants from the flexible loop C, and either capping the nest or extending toward peripheral subsites, dictate broad versus narrow receptor subtype selectivity. From these data, small spiroimine enantiomers mimicking the functional core motif of phycotoxins were chemically synthesized and characterized. Voltage-clamp analyses involving three nAChR subtypes revealed preserved antagonism for both enantiomers, despite lower subtype specificity and binding affinities associated with faster reversibility compared with their macrocyclic relatives. Binding and structural analyses involving two AChBPs pointed to modest affinities and positional variability of the spiroimines, along with a range of AChBP loop-C conformations denoting a prevalence of antagonistic properties. These data highlight the major contribution of the spiroimine core to binding within the nAChR nest and confirm the need for an extended interaction network as established by the macrocyclic toxins to define high affinities and marked subtype specificity. This study identifies a minimal set of functional pharmacophores and binding determinants as templates for designing new antagonists targeting disease-associated nAChR subtypes.

Catharanthine Modulates Mesolimbic Dopamine Transmission and Nicotine Psychomotor Effects via Inhibition of α6-Nicotinic Receptors and Dopamine Transporters.

Iboga alkaloids, also known as coronaridine congeners, have shown promise in the treatment of alcohol and opioid use disorders. The objective of this study was to evaluate the effects of catharanthine and 18-methoxycoronaridine (18-MC) on dopamine (DA) transmission and cholinergic interneurons in the mesolimbic DA system, nicotine-induced locomotor activity, and nicotine-taking behavior. Utilizing ex vivo fast-scan cyclic voltammetry (FSCV) in the nucleus accumbens core of male mice, we found that catharanthine or 18-MC differentially inhibited evoked DA release. Catharanthine inhibition of evoked DA release was significantly reduced by both α4 and α6 nicotinic acetylcholine receptors (nAChRs) antagonists. Additionally, catharanthine substantially increased DA release more than vehicle during high-frequency stimulation, although less potently than an α4 nAChR antagonist, which confirms previous work with nAChR antagonists. Interestingly, while catharanthine slowed DA reuptake measured via FSCV ex vivo, it also increased extracellular DA in striatal dialysate from anesthetized mice in vivo in a dose-dependent manner. Superfusion of catharanthine or 18-MC inhibited the firing rate of striatal cholinergic interneurons in a concentration dependent manner, which are known to potently modulate presynaptic DA release. Catharanthine or 18-MC suppressed acetylcholine currents in oocytes expressing recombinant rat α6/α3ß2ß3 or α6/α3ß4 nAChRs. In behavioral experiments using male Sprague-Dawley rats, systemic administration of catharanthine or 18-MC blocked nicotine enhancement of locomotor activity. Importantly, catharanthine attenuated nicotine self-administration in a dose-dependent manner while having no effect on food reinforcement. Lastly, administration of catharanthine and nicotine together greatly increased head twitch responses, indicating a potential synergistic hallucinogenic effect. These findings demonstrate that catharanthine and 18-MC have similar, but not identical effects on striatal DA dynamics, striatal cholinergic interneuron activity and nicotine psychomotor effects.

The response of Anisakis simplex (s. s.) to anthelmintics - Specific changes in xenobiotic metabolic processes.

Anisakiasis is a parasitic disease transmitted through the consumption of raw or undercooked fish and cephalopods that are infected with larvae of Anisakis simplex (sensu stricto) or Anisakis pegreffii. The purpose of this study was to investigate how A. simplex (s. s.) responds to the influence of anthelmintics such as ivermectin (IVM) and pyrantel (PYR). In vitro experiments were conducted using larvae at two developmental stages of A. simplex (s. s.) (L3 and L4) obtained from Baltic herring (Clupea harengus membras). Larvae were cultured with different concentrations of IVM or PYR (1.56, 3.125, and 6.25 µg/mL) for various durations (3, 6, 9, and 12 h) under anaerobic conditions (37 °C, 5% CO2). The gene expression of actin, ABC transporter, antioxidant enzymes, γ-aminobutyric acid receptors, and nicotinic acetylcholine receptors, as well as the oxidative status were analyzed. The results showed that A. simplex (s. s.) L3 stage had lower mobility when cultured with PYR compared to IVM. The analysis of relative gene expression revealed significant differences in the mRNA level of ABC transporters after treatment with IVM and PYR, compared to the control group. Similar patterns were observed in the gene expression of antioxidant enzymes in response to both drugs. Furthermore, the total antioxidant capacity (TAC) and glutathione S-transferase (GST) activity were higher in the treatment groups than in the control group. These findings suggest a relationship between the expression of the studied genes, including those related to oxidative metabolism, and the effectiveness of the tested drugs.

Cytisinicline for Smoking Cessation: A Randomized Clinical Trial.

Importance: Cytisinicline (cytisine) is a plant-based alkaloid that, like varenicline, binds selectively to α4ß2 nicotinic acetylcholine receptors, which mediate nicotine dependence. Although not licensed in the US, cytisinicline is used in some European countries to aid smoking cessation, but its traditional dosing regimen and treatment duration may not be optimal. Objective: To evaluate the efficacy and tolerability of cytisinicline for smoking cessation when administered in a novel pharmacokinetically based dosing regimen for 6 or 12 weeks vs placebo. Design, Setting, and Participants: A 3-group, double-blind, placebo-controlled, randomized trial (ORCA-2) compared 2 durations of cytisinicline treatment (6 or 12 weeks) vs placebo, with follow-up to 24 weeks, among 810 adults who smoked cigarettes daily and wanted to quit. It was conducted at 17 US sites from October 2020 to December 2021. Interventions: Participants were randomized (1:1:1) to cytisinicline, 3 mg, 3 times daily for 12 weeks (n = 270); cytisinicline, 3 mg, 3 times daily for 6 weeks then placebo 3 times daily for 6 weeks (n = 269); or placebo 3 times daily for 12 weeks (n = 271). All participants received behavioral support. Main Outcomes and Measures: Biochemically verified continuous smoking abstinence for the last 4 weeks of cytisinicline treatment vs placebo (primary) and from end of treatment to 24 weeks (secondary). Results: Of 810 randomized participants (mean age, 52.5 years; 54.6% female; mean of 19.4 cigarettes smoked daily), 618 (76.3%) completed the trial. For the 6-week course of cytisinicline vs placebo, continuous abstinence rates were 25.3% vs 4.4% during weeks 3 to 6 (odds ratio [OR], 8.0 [95% CI, 3.9-16.3]; P < .001) and 8.9% vs 2.6% during weeks 3 to 24 (OR, 3.7 [95% CI, 1.5-10.2]; P = .002). For the 12-week course of cytisinicline vs placebo, continuous abstinence rates were 32.6% vs 7.0% for weeks 9 to 12 (OR, 6.3 [95% CI, 3.7-11.6]; P < .001) and 21.1% vs 4.8% during weeks 9 to 24 (OR, 5.3 [95% CI, 2.8-11.1]; P < .001). Nausea, abnormal dreams, and insomnia occurred in less than 10% of each group. Sixteen participants (2.9%) discontinued cytisinicline due to an adverse event. No drug-related serious adverse events occurred. Conclusions and Relevance: Both 6- and 12-week cytisinicline schedules, with behavioral support, demonstrated smoking cessation efficacy and excellent tolerability, offering new nicotine dependence treatment options. Trial Registration: ClinicalTrials.gov Identifier: NCT04576949.

Brain antioxidant status and gene expressions of nicotinic and dopamine receptors are improved by black seed oil administration in cigarette smoke or nicotine vapour-exposed rats.

BACKGROUND: Smoking is associated with dysregulation of the antioxidant system and addiction. AIM: This study sought to ascertain the effect of Nigella Sativa (NS) oil on the antioxidant system, nicotine/tobacco addiction as well as the expressions of α4ß2 nicotinic (nAChR) and dopamine type-2 (DRD2) receptors in selected brain regions of the rat. METHODS: Thirty male Sprague-Dawley rats were divided into 6 groups comprising of vehicle-treated control, NS oil only, Smoke only, Smoke + NS oil, Nicotine only and Nicotine + NS oil. Animals were passively exposed to cigarette smoke or nicotine vapour for 12 weeks, however, NS oil treatment commenced from 9th-12th week of the experimental duration. RESULTS: Nicotine vapour and cigarette smoke-induced increase in cotinine level were significantly ameliorated by NS treatment. Cigarette smoke or nicotine vapour exposure significantly (p<0.05) decreased the level of antioxidant enzymes while increasing malondialdehyde level in the brain homogenates of the rats.  Administration of NS oil significantly (p<0.05) reversed the reduced antioxidant level. Cigarette-smoke also significantly increased α4-nAChR expression in the frontal cortex and olfactory bulb compared to control. Nicotine vapour significantly increased DRD2 expression only in the olfactory cortex. NS oil administration reduced both the cigarette-smoke-induced increase in α4-nAChR and nicotine vapour-induced increase in DRD2 gene expression only in the olfactory cortex. CONCLUSION: Findings from this study suggest that NS oil improves brain antioxidant status while ameliorating nicotine vapour and cigarette smoke addiction through down-regulation of α4-nAChR and DRD2 gene expressions in discrete brain regions in Sprague-Dawley rats.

Dequalinium chloride is an antagonists of α7 nicotinic acetylcholine receptors.

Dequalinium chloride has been used primarily as antiseptic compounds, but recently has been investigated for its effects on specific targets, including muscarinic acetylcholine receptors. Here we investigated dequalinium chloride as an antagonist to α7 nicotinic acetylcholine receptors. The pharmacological properties of dequalinium were established using cell lines stably co-transfected with the calcium-permeable human α7 nicotinic acetylcholine receptors and its chaperone NACHO, calcium dye fluorescent measurements or a calcium-sensitive protein reporter, and patch clamp recording of ionic currents. Using calcium dye fluorescence plate reader measurements, we find dequalinium chloride is an antagonist of α7 nicotinic acetylcholine receptors with an IC50 of 672 nM in response to activation with 500 µM acetylcholine chloride and positive allosteric modulator PNU-120596. However, using a membrane-tethered GCAMP7s calcium reporter allowed detection of α7-mediated calcium flux in the absence of PNU-120596. Using this approach revealed an IC50 of 157 nM for dequalinium on 300 µM acetylcholine-evoked currents. Using patch clamp recordings with 300 µM acetylcholine chloride and 10 µM PNU-120596, we find lower concentrations are sufficient to block ionic currents, with IC50 of 120 nM for dequalinium chloride and 54 nM for the related UCL 1684 compound. In summary, we find that dequalinium chloride and UCL1684, which are generally used to block SK-type potassium channels, are also highly effective antagonists of α7 nicotinic acetylcholine receptors. This finding, in combination with previous studies of muscarinic acetylcholine receptors, clearly establishes dequalinium compounds within the class of general anti-cholinergic antagonists.

A Novel α4/7-Conotoxin QuIA Selectively Inhibits α3ß2 and α6/α3ß4 Nicotinic Acetylcholine Receptor Subtypes with High Efficacy.

α6ß4 nAChR is expressed in the peripheral and central nervous systems and is associated with pain, addiction, and movement disorders. Natural α-conotoxins (α-CTxs) can effectively block different nAChR subtypes with higher efficacy and selectivity. However, the research on α6ß4 nAChR is relatively poor, partly because of the lack of available target-specific α-CTxs. In this study, we synthesized a novel α-4/7 conotoxin QuIA that was found from Conus quercinus. We investigated the efficacy of this peptide to different nAChR subtypes using a two-electrode voltage-clamp technique. Remarkably, we found α-QuIA inhibited the neuronal α3ß2 and α6/α3ß4 nAChR subtypes with significantly high affinity (IC50 was 55.7 nM and 90.68 nM, respectively), and did not block other nAChR subtypes even at a high concentration of 10 µM. In contrast, most α-CTxs have been determined so far to effectively block the α6/α3ß4 nAChR subtype while also maintaining a similar higher efficacy against the closely related α6ß2ß3 and/or α3ß4 subtypes, which are different from QuIA. In conclusion, α-QuIA is a novel α4/7-CTx, which has the potential to develop as an effective neuropharmacology tool to detect the function of α6ß4 nAChR.

Inhibition of TRPC1, TRPM4 and CHRNA6 ion channels ameliorates depression-like behavior in rats.

The roles of ion channels, miRNAs and, neurotransmitters in the pathophysiology of major depressive disorder (MDD) are not yet fully elucidated. The current study aims to investigate ion channel gene expressions in the brain, the therapeutic efficacies of TRPC1, TRPM4, and CHRNA6 inhibitors, miRNAs specific to these ion channels and, neurotransmitter interactions in a chronic unpredictable mild stress (CUMS) induced MDD rat model. 48 two-month-old male albino Wistar rats were divided into Control, CUMS, Sham, CUMS+Pico145 (TRPC1 inhibitor), CUMS+ 9-Phe (TRPM4 inhibitor), and CUMS+BPiDl (CHRNA6 inhibitor) groups. Seven-week CUMS was used to induce MDD. Inhibitors were administered subacutely on the final of CUMS. Rats were subjected to behavioral tests. Gene expression levels were analyzed using qRT-PCR and neurotransmitter levels using ELISA. CUMS lead to a significant upregulation in the expression of channels in the hippocampus, and channels in the prefrontal cortex. Behavioral experiments determined the antidepressant effects as follows: Pico145 > BPiDl > 9-Phe. Compared to the Control, serotonin and noradrenaline levels remained unchanged, whereas dopamine levels increased. Acetylcholine levels decreased in CUMS and CUMS+Pico145 groups. CUMS significantly altered the expression of 6 miRNAs in the brain. BPiDl upregulated the expression of miR-6334 and Pico145 upregulated the expression of miR-135b-5p and miR-875 in the prefrontal cortex. The interactions of ion channels, miRNAs, and disruptions of neurotransmitter networks can play an important role in the pathophysiology of MDD. Moreover, as shown in this study, ion channel inhibitors have significant potential in the treatment of this disease.

Nicotinic Acetylcholine Receptors in the Respiratory Tract.

Nicotinic acetylcholine receptors (nAChR) are widely distributed in neuronal and non-neuronal tissues, where they play diverse physiological roles. In this review, we highlight the recent findings regarding the role of nAChR in the respiratory tract with a special focus on the involvement of nAChR in the regulation of multiple processes in health and disease. We discuss the role of nAChR in mucociliary clearance, inflammation, and infection and in airway diseases such as asthma, chronic obstructive pulmonary disease, and cancer. The subtype diversity of nAChR enables differential regulation, making them a suitable pharmaceutical target in many diseases. The stimulation of the α3ß4 nAChR could be beneficial in diseases accompanied by impaired mucociliary clearance, and the anti-inflammatory effect due to an α7 nAChR stimulation could alleviate symptoms in diseases with chronic inflammation such as chronic obstructive pulmonary disease and asthma, while the inhibition of the α5 nAChR could potentially be applied in non-small cell lung cancer treatment. However, while clinical studies targeting nAChR in the airways are still lacking, we suggest that more detailed research into this topic and possible pharmaceutical applications could represent a valuable tool to alleviate the symptoms of diverse airway diseases.

Acute effects of the imidacloprid metabolite desnitro-imidacloprid on human nACh receptors relevant for neuronal signaling.

Several neonicotinoids have recently been shown to activate the nicotinic acetylcholine receptor (nAChR) on human neurons. Moreover, imidacloprid (IMI) and other members of this pesticide family form a set of diverse metabolites within crops. Among these, desnitro-imidacloprid (DN-IMI) is of special toxicological interest, as there is evidence (i) for human dietary exposure to this metabolite, (ii) and that DN-IMI is a strong trigger of mammalian nicotinic responses. We set out here to quantify responses of human nAChRs to DN-IMI and an alternative metabolite, IMI-olefin. To evaluate toxicological hazards, these data were then compared to those of IMI and nicotine. Ca2+-imaging experiments on human neurons showed that DN-IMI exhibits an agonistic effect on nAChRs at sub-micromolar concentrations (equipotent with nicotine) while IMI-olefin activated the receptors less potently (in a similar range as IMI). Direct experimental data on the interaction with defined receptor subtypes were obtained by heterologous expression of various human nAChR subtypes in Xenopus laevis oocytes and measurement of the transmembrane currents evoked by exposure to putative ligands. DN-IMI acted on the physiologically important human nAChR subtypes α7, α3ß4, and α4ß2 (high-sensitivity variant) with similar potency as nicotine. IMI and IMI-olefin were confirmed as nAChR agonists, although with 2-3 orders of magnitude lower potency. Molecular docking studies, using receptor models for the α7 and α4ß2 nAChR subtypes supported an activity of DN-IMI similar to that of nicotine. In summary, these data suggest that DN-IMI functionally affects human neurons similar to the well-established neurotoxicant nicotine by triggering α7 and several non-α7 nAChRs.

Pursuing High-Resolution Structures of Nicotinic Acetylcholine Receptors: Lessons Learned from Five Decades.

Since their discovery, nicotinic acetylcholine receptors (nAChRs) have been extensively studied to understand their function, as well as the consequence of alterations leading to disease states. Importantly, these receptors represent pharmacological targets to treat a number of neurological and neurodegenerative disorders. Nevertheless, their therapeutic value has been limited by the absence of high-resolution structures that allow for the design of more specific and effective drugs. This article offers a comprehensive review of five decades of research pursuing high-resolution structures of nAChRs. We provide a historical perspective, from initial structural studies to the most recent X-ray and cryogenic electron microscopy (Cryo-EM) nAChR structures. We also discuss the most relevant structural features that emerged from these studies, as well as perspectives in the field.

Ethanol interaction with α3ß4 nicotinic acetylcholine receptors in neurons of the laterodorsal tegmentum.

BACKGROUND: Nicotinic acetylcholine receptors (nAChRs) play a key role in the rewarding effects of ethanol (EtOH), and while several nAChR subtypes have been implicated, attention has recently shifted to a role for the α3ß4 nAChR. The laterodorsal tegmental nucleus (LDTg), a brainstem cholinergic nucleus that sends excitatory projections to the ventral tegmental area, is an Integral part of the brain reward pathway. Here we investigate a potential role for LDTg α3ß4 nAChRs in EtOH self-administration and reward. METHODS: Sprague-Dawley rats were given ad libitum access to a 20% EtOH solution, as part of a two-bottle choice paradigm. Approximately 1 week after removal of EtOH access, we measured LDTg α3ß4 nAChR current responses to focal application of acetylcholine (ACh), using whole-cell patch clamp electrophysiology recordings in acute brain slices. In addition, we used whole-cell electrophysiology to assess the acute effects of EtOH on the sensitivity of LDTg α3ß4 nAChRs. RESULTS: Focal application of ACh onto LDTg neurons resulted in large α3ß4 nAChR-mediated inward currents, the magnitude of which showed a positive correlation with levels of EtOH self-administration. In addition, using brain slices taken from EtOH-naïve rats, bath application of EtOH resulted in a moderate potentiation of LDTg α3ß4 nAChR sensitivity. CONCLUSIONS: Using a rat model, increased α3ß4 nAChR function was associated with greater EtOH self-administration, with α3ß4 nAChR function also acutely potentiated by EtOH. Assuming that similar findings apply to humans, the α3ß4 nAChR could be a therapeutic target in the treatment of EtOH use disorder.

Physiological Effects of Neonicotinoid Insecticides on Non-Target Aquatic Animals-An Updated Review.

In this paper, we review the effects of large-scale neonicotinoid contaminations in the aquatic environment on non-target aquatic invertebrate and vertebrate species. These aquatic species are the fauna widely exposed to environmental changes and chemical accumulation in bodies of water. Neonicotinoids are insecticides that target the nicotinic type acetylcholine receptors (nAChRs) in the central nervous systems (CNS) and are considered selective neurotoxins for insects. However, studies on their physiologic impacts and interactions with non-target species are limited. In researches dedicated to exploring physiologic and toxic outcomes of neonicotinoids, studies relating to the effects on vertebrate species represent a minority case compared to invertebrate species. For aquatic species, the known effects of neonicotinoids are described in the level of organismal, behavioral, genetic and physiologic toxicities. Toxicological studies were reported based on the environment of bodies of water, temperature, salinity and several other factors. There exists a knowledge gap on the relationship between toxicity outcomes to regulatory risk valuation. It has been a general observation among studies that neonicotinoid insecticides demonstrate significant toxicity to an extensive variety of invertebrates. Comprehensive analysis of data points to a generalization that field-realistic and laboratory exposures could result in different or non-comparable results in some cases. Aquatic invertebrates perform important roles in balancing a healthy ecosystem, thus rapid screening strategies are necessary to verify physiologic and toxicological impacts. So far, much of the studies describing field tests on non-target species are inadequate and in many cases, obsolete. Considering the current literature, this review addresses important information gaps relating to the impacts of neonicotinoids on the environment and spring forward policies, avoiding adverse biological and ecological effects on a range of non-target aquatic species which might further impair the whole of the aquatic ecological web.

Nicotine inhibits the VTA-to-amygdala dopamine pathway to promote anxiety.

Nicotine stimulates dopamine (DA) neurons of the ventral tegmental area (VTA) to establish and maintain reinforcement. Nicotine also induces anxiety through an as yet unknown circuitry. We found that nicotine injection drives opposite functional responses of two distinct populations of VTA DA neurons with anatomically segregated projections: it activates neurons that project to the nucleus accumbens (NAc), whereas it inhibits neurons that project to the amygdala nuclei (Amg). We further show that nicotine mediates anxiety-like behavior by acting on ß2-subunit-containing nicotinic acetylcholine receptors of the VTA. Finally, using optogenetics, we bidirectionally manipulate the VTA-NAc and VTA-Amg pathways to dissociate their contributions to anxiety-like behavior. We show that inhibition of VTA-Amg DA neurons mediates anxiety-like behavior, while their activation prevents the anxiogenic effects of nicotine. These distinct subpopulations of VTA DA neurons with opposite responses to nicotine may differentially drive the anxiogenic and the reinforcing effects of nicotine.

Studies on the role of alpha 7 nicotinic acetylcholine receptors in K562 cell proliferation and signaling.

The results we obtained from this study gave information about the determination of alpha 7 nicotinic acetylcholine receptor (α7-nACh) expression in human erythroleukemia cells, as well as whether it has a role in calcium release and cell proliferation in the presence of nicotinic agonist, antagonists. Determining the roles of α7 nicotinic receptors in erythroleukemia cells will also contribute to leukemia-related signal transduction studies. This study is primarily to determine the role of nicotinic agonists and antagonists in cell proliferation, α7 nicotinic acetylcholine receptor expression, and calcium release. The aim of this study, which is a continuation and an important part of our previous studies on the cholinergic system, has contributed to the literature on the human erythroleukemia cell signaling mechanism. Cell viability was evaluated by the trypan blue exclusion test and Bromodeoxyuridine/5-Bromo-2'-deoxyuridine (BrdU) labeling. Acetylcholine, nicotinic alpha 7 receptor antagonist methyllycaconitine citrate, and cholinergic antagonist atropine were used to determine the role of α7-nACh in K562 cell proliferation. In our experiments, the fluorescence spectrophotometer was used in Ca2+ measurements. The expression of nicotinic alpha 7 receptor was evaluated by western blot. The stimulating effect of acetylcholine in K562 cell proliferation was reversed by both the α7 nicotinic antagonist methyllycaconitine citrate and the cholinergic antagonist, atropine. Methyllycaconitine citrate inhibited K562 cell proliferation partially explained the roles of nicotinic receptors in signal transduction. While ACh caused an increase in intracellular Ca2+, methyllycaconitine citrate decreased intracellular Ca2+ level in K562 cell. The effects of nicotinic agonists and/or antagonists on erythroleukemic cells on proliferation, calcium level contributed to the interaction of nicotinic receptors with different signaling pathways. Proliferation mechanisms in erythroleukemic cells are under the control of the α7 nicotinic acetylcholine receptor via calcium influx and different signalling pathway.

Task-dependent effects of nicotine treatment on auditory performance in young-adult and elderly human nonsmokers.

Electrophysiological studies show that nicotine enhances neural responses to characteristic frequency stimuli. Previous behavioral studies partially corroborate these findings in young adults, showing that nicotine selectively enhances auditory processing in difficult listening conditions. The present work extended previous work to include both young and older adults and assessed the nicotine effect on sound frequency and intensity discrimination. Hypotheses were that nicotine improves auditory performance and that the degree of improvement is inversely proportional to baseline performance. Young (19-23 years old) normal-hearing nonsmokers and elderly (61-80) nonsmokers with normal hearing between 500 and 2000 Hz received nicotine gum (6 mg) or placebo gum in a single-blind, randomized crossover design. Participants performed three experiments (frequency discrimination, frequency modulation identification, and intensity discrimination) before and after treatment. The perceptual differences were analyzed between pre- and post-treatment, as well as between post-treatment nicotine and placebo conditions as a function of pre-treatment baseline performance. Compared to pre-treatment performance, nicotine significantly improved frequency discrimination. Compared to placebo, nicotine significantly improved performance for intensity discrimination, and the improvement was more pronounced in the elderly with lower baseline performance. Nicotine had no effect on frequency modulation identification. Nicotine effects are task-dependent, reflecting possible interplays of subjects, tasks and neural mechanisms.