Is impulsivity related to attentional bias in cigarette smokers? An exploration across levels of nicotine dependency and deprivation.

Research has largely focused on how attentional bias to smoking-related cues and impulsivity independently influence the development and maintenance of cigarette smoking, with limited exploration of the relationship between these mechanisms. The current experiments systematically assessed relationships between multiple dimensions of impulsivity and attentional bias, at different stages of attention, in smokers varying in nicotine dependency and deprivation. Nonsmokers (NS; n  = 26), light-satiated smokers (LS; n  = 25), heavy-satiated smokers (HS; n  = 23) and heavy 12-hour nicotine-deprived smokers (HD; n  = 30) completed the Barratt Impulsivity Scale, delayed discounting task, stop-signal task, information sampling task and a visual dot-probe assessing initial orientation (200 ms) and sustained attention (2000 ms) toward smoking-related cues. Sustained attention to smoking-related cues was present in both HS and LS, while initial orientation bias was only evident in HS. HS and LS also had greater levels of trait motor and nonplanning impulsivity and heightened impulsive choice on the delay discounting task compared with NS, while heightened trait attentional impulsivity was only found in HS. In contrast, in HD, nicotine withdrawal was associated with no attentional bias but heightened reflection impulsivity, poorer inhibitory control and significantly lower levels of impulsive choice relative to satiated smokers. Trait and behavioral impulsivity were not related to the extent of attentional bias to smoking-related cues at any stage of attention, level of nicotine dependency or state of deprivation. Findings have both clinical and theoretical implications, highlighting the unique and independent roles impulsivity and attentional bias may play at different stages of the nicotine addiction cycle.

Attenuation of Nicotine Effects on A549 Lung Cancer Cells by Synthetic α7 nAChR Antagonists APS7-2 and APS8-2.

Nicotine binds to nicotinic acetylcholine receptors (nAChRs) that are overexpressed in different cancer cells, promoting tumor growth and resistance to chemotherapy. In this study, we aimed to investigate the potential of APS7-2 and APS8-2, synthetic analogs of a marine sponge toxin, to inhibit nicotine-mediated effects on A549 human lung cancer cells. Our electrophysiological measurements confirmed that APS7-2 and APS8-2 act as α7 nAChR antagonists. APS8-2 showed no cytotoxicity in A549 cells, while APS7-2 showed concentration-dependent cytotoxicity in A549 cells. The different cytotoxic responses of APS7-2 and APS8-2 emphasize the importance of the chemical structure in determining their cytotoxicity on cancer cells. Nicotine-mediated effects include increased cell viability and proliferation, elevated intracellular calcium levels, and reduced cisplatin-induced cytotoxicity and reactive oxygen species production (ROS) in A549 cells. These effects of nicotine were effectively attenuated by APS8-2, whereas APS7-2 was less effective. Our results suggest that APS8-2 is a promising new therapeutic agent in the chemotherapy of lung cancer.

Nicotine improves DSS-induced colitis by inhibiting NLRP3 and altering gut microbiota.

Ulcerative colitis (UC) is a chronic recurrent inflammatory disease affecting the rectum and colon. Numerous epidemiological studies have identified smoking as a protective factor for UC. Dysbiosis of intestinal microbiota and release of inflammatory factors are well-established characteristics associated with UC. Therefore, we have observed that nicotine exhibits the potential to ameliorate colitis symptoms in UC mice. Additionally, it exerts a regulatory effect on colonic microbiota dysbiosis by promoting the growth of beneficial bacteria while suppressing harmful bacteria. Combined in vivo and in vitro investigations demonstrate that nicotine primarily impedes the assembly of NLRP3, subsequently inhibiting downstream IL-1ß secretion.

Multifaceted Applications of Luminescent Metalloporphyrin Derivatives: Fluorescence Turn-On Sensing of Nicotine and Antimicrobial Activity.

In this study, we designed and synthesized metalloporphyrin derivatives (with Ni and Zn) specifically intended for the fluorescence detection of nicotine in aqueous solutions. Our results showcased a notable selectivity for nicotine over other naturally occurring food toxins, exhibiting an exceptional sensitivity with a limit of detection as low as 7.2 nM. Through mechanistic investigations (1H NMR, FT-IR, etc.), we elucidated the binding mechanism, revealing the specific interaction between the pyridine ring of nicotine and the metal center, while the N atom pyrrolidine unit engaged in the hydrogen bonding with the side chain of the porphyrin ring. Notably, we observed that the nature of the metal center dictated the extent of interaction with nicotine; particularly, Zn-porphyrin demonstrated a superior response compared to Ni-porphyrin. Furthermore, we performed the quantitative estimation of nicotine in commercially available tobacco products. Additionally, we conducted the antibacterial (Staphylococcus aureus and Escherichia coli) and antifungal (Candida albicans) activities of the porphyrin derivatives.

Nicotine restores olfactory function by activation of prok2R/Akt/FoxO3a axis in Parkinson's disease.

BACKGROUND: Olfactory dysfunction occurs frequently in Parkinson's disease (PD). In this study, we aimed to explore the potential biomarkers and underlying molecular pathways of nicotine for the treatment of olfactory dysfunction in 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced PD mice. METHODS: MPTP was introduced into C57BL/6 male mice to generate a PD model. Regarding in vivo experiments, we performed behavioral tests to estimate the protective effects of nicotine in MPTP-induced PD mice. RNA sequencing and traditional molecular methods were used to identify molecules, pathways, and biological processes in the olfactory bulb of PD mouse models. Then, in vitro experiments were conducted to evaluate whether nicotine can activate the prok2R/Akt/FoxO3a signaling pathway in both HEK293T cell lines and primary olfactory neurons treated with 1-methyl-4-phenylpyridinium (MPP+). Next, prok2R overexpression (prok2R+) and knockdown (prok2R-) were introduced with lentivirus, and the Akt/FoxO3a signaling pathway was further explored. Finally, the damaging effects of MPP+ were evaluated in prok2R overexpression (prok2R+) HEK293T cell lines. RESULTS: Nicotine intervention significantly alleviated olfactory and motor dysfunctions in mice with PD. The prok2R/Akt/FoxO3a signaling pathway was activated after nicotine treatment. Consequently, apoptosis of olfactory sensory neurons was significantly reduced. Furthermore, prok2R+ and prok2R- HEK293T cell lines exhibited upregulation and downregulation of the Akt/FoxO3a signaling pathway, respectively. Additionally, prok2R+ HEK293T cells were resistant to MPP+-induced apoptosis. CONCLUSIONS: This study showed the effectiveness and underlying mechanisms of nicotine in improving hyposmia in PD mice. These improvements were correlated with reduced apoptosis of olfactory sensory neurons via activated prok2R/Akt/FoxO3a axis. These results explained the potential protective functions of nicotine in PD patients.

Preventive effects of crocin, a natural compound from saffron, against nicotine­induced oxidative stress and neurobehavioral disturbances.

Nicotine is a psychostimulant that induces neurochemical and behavioral changes upon chronic administration, leading to neurodegenerative conditions associated with smoking. As of now, no preventive or therapeutic strategies are known to counteract nicotine­induced neurodegeneration. In this study, we explore the neuroprotective effects of crocin, a bioactive agent commonly found in saffron - a spice derived from the flower of Crocus sativus - using a rat model. The dose­dependent effects of crocin were evaluated in nicotine­induced neurodegeneration and compared with a control group. Neurobehavioral changes, assessed through the elevated plus maze, the open field test, the forced swim test, and the Morris water maze, as well as oxidative stress in the hippocampus, were evaluated. Interestingly, nicotine administration resulted in depression, anxiety, and abnormal motor and cognitive functions, while crocin treatment protected the rat brain from these abnormalities. The beneficial effects of crocin were associated with reduced oxidative stress biomarkers such as malondialdehyde, along with increases in superoxide dismutase, glutathione peroxidase, and glutathione reductase activities. These results demonstrate that crocin can mitigate nicotine­induced neurodegeneration by reducing oxidative stress, potentially offering a protective measure against neurodegenerative effects in smokers.

Gut bacterium Burkholderia cepacia (BsNLG8) and immune gene Defensin A contribute to the resistance against Nicotine-induced stress in Nilaparvata lugens (Stål).

Nicotine, a naturally occurring alkaloid found in tobacco, is a potent neurotoxin extensively used to control Nilaparvata lugens (Stål), a destructive insect pest of rice crops. The insect gut harbors a wide array of resident microorganisms that profoundly influence several biological processes, including host immunity. Maintaining an optimal gut microbiota and immune homeostasis requires a complex network of reciprocal regulatory interactions. However, the underlying molecular mechanisms driving these symbiotic exchanges, particularly between specific gut microbe and immunity, remain largely unknown in insects. Our previous investigations identified and isolated a nicotine-degrading Burkholderia cepacia strain (BsNLG8) with antifungal properties. Building on those findings, we found that nicotine intake significantly increased the abundance of a symbiotic bacteria BsNLG8, induced a stronger bacteriostatic effect in hemolymph, and enhanced the nicotine tolerance of N. lugens. Additionally, nicotine-induced antimicrobial peptides (AMPs) exhibited significant antibacterial effects against Staphylococcus aureus. We adopted RNA-seq to explore the underlying immunological mechanisms in nicotine-stressed N. lugens. Bioinformatic analyses identified numerous differentially expressed immune genes, including recognition/immune activation (GRPs and Toll) and AMPs (i.e., Defensin, Lugensin, lysozyme). Temporal expression profiling (12, 24, and 48 hours) of immune genes revealed pattern recognition proteins and immune effectors as primary responders to nicotine-induced stress. Defensin A, a broad-spectrum immunomodulatory cationic peptide, exhibited significantly high expression. RNA interference-mediated silencing of Defensin A reduced the survival, enhanced nicotine sensitivity of N. lugens to nicotine, and decreased the abundance of BsNLG8. The reintroduction of BsNLG8 improved the expression of immune genes, aiding nicotine resistance of N. lugens. Our findings indicate a potential reciprocal immunomodulatory interaction between Defensin A and BsNLG8 under nicotine stress. Moreover, this study offers novel and valuable insights for future research into enhancing nicotine-based pest management programs and developing alternative biocontrol methods involving the implication of insect symbionts.

Nelotanserin, a selective 5-HT2A receptor inverse agonist, attenuates aspects of nicotine withdrawal but not reward in mice.

Nicotine smoking contributes to many preventable disabilities, diseases and deaths. Targeting nicotine reward and withdrawal is a basis for the majority of smoking cessation pharmacotherapies. Due to the emergence of interest in 5-HT2A receptor modulators for numerous psychiatric disorders, we investigated the effect of nelotanserin, a 5-HT2A receptor inverse agonist, on nicotine reward and withdrawal in ICR mice. In nicotine-dependent mice, nelotanserin dose-dependently reduced somatic signs of nicotine withdrawal and thermal hyperalgesia as measured in the hot plate test. However, nelotanserin had no effect on anxiety-like behavior and failed to reduce nicotine reward as measured in the conditioned place preference test. Our results suggest that inverse agonism of the 5-HT2A receptor may be a feasible novel mechanism for smoking cessation by reducing both physical withdrawal and thermal hyperalgesia associated with nicotine abstinence but may require complementary pharmacotherapies targeting affective and reward-associated decrements to improve cessation outcomes.

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.

Investigating the role of nicotinic acetylcholine receptors in menthol's effects in mice.

The use of menthol in tobacco products has been linked to an increased likelihood of developing nicotine dependence. The widespread use of menthol can be attributed to its unique sensory characteristics; however, emerging evidence suggests that menthol also alters sensitivity to nicotine through modulation of nicotinic acetylcholine receptors (nAChRs). Nicotinic subunits, such as ß2 and α5, are of interest due to their implications in nicotine reward, reinforcement, intake regulation, and aversion. This study, therefore, examined the in vivo relevance of ß2 and α5 nicotinic subunits on the pharmacological and behavioral effects of menthol. Data suggests that the α5 nicotinic subunit modulates menthol intake in mice. Overall, deletion or a reduction in function of the α5 subunit lessened aversion to menthol. α5 KO mice and mice possessing the humanized α5 SNP, a variant that confers a nicotine dependence phenotype in humans, demonstrated increased menthol intake compared to their WT counterparts and in a sex-related fashion for α5 SNP mice. We further reported that the modulatory effects of the α5 subunit do not extend to other aversive tastants like quinine, suggesting that deficits in α5* nAChR signaling may not abolish general sensitivity to the aversive effects of other noxious chemicals. Further probing into the role of α5 in other pharmacological properties of menthol revealed that the α5 subunit does not modulate the antinociceptive properties of menthol in mice and suggests that the in vivo differences observed are likely not due to the direct effects of menthol on α5-containing nAChRs in vitro.

Different Influence Pattern of Conventional and Alternative Sources of Smoking on Adhesion Molecules and Cytokine Secretion in THP-1 Monocytes.

BACKGROUND/AIM: Tobacco is a carcinogen that is closely associated with the occurrence of lung cancer and head and neck squamous cell carcinoma (HNSCC). The consumption of tobacco is also leading to alterations in different immune cell subtypes. However, the impact of different conventional and alternative smoking sources on human monocytes remains elusive. MATERIALS AND METHODS: In this study, we investigated the influence of aqueous extracts of different sources of smoking (cigarettes; heated tobacco product IQOS; e-cigarettes with and without nicotine; nicotine pouches) on different monocytic adhesion molecules, chemokine receptors and checkpoint molecule PD-L1 by flow cytometry. Cytokine expression patterns were evaluated using human cytokine arrays and the human monocyte leukemia cell line THP-1 as a model. RESULTS: Data revealed differential effects of the analyzed conventional and alternative smoking devices on monocyte adhesion molecules and cytokine secretion. The examined smoking devices can be assigned to two differential monocyte activation patterns. Monocytes stimulated with aqueous extracts of cigarettes, e-cigarette without nicotine, and heat not burn product IQOS revealed distinct alterations of surface markers and cytokines compared to the monocyte activation pattern in response to aqueous extracts of nicotine, nicotine pouches, and e-cigarette with nicotine. CONCLUSION: Our data indicate differential immunological consequences of different conventional and alternative smoking sources with and without nicotine. Further comprehensive analysis as well as in vivo investigations on peripheral blood monocyte subsets from smoking individuals using different smoking sources are required to better understand the impact on monocyte characteristics, especially with regard to the development of cancer.

Effects of nicotine on microRNA-124 expression in bile duct ligation-induced liver fibrosis in rats.

BACKGROUND: Nicotine, the main compound of smoking may exert its effects by changing the expression of microRNAs (miRNAs). This study was conducted to further investigate the molecular mechanisms of miRNA-dependent effects of nicotine in an animal model of liver fibrosis. METHODS: The bile duct ligation (BDL) approach was used to create a model of liver fibrosis. Twenty-four male Wistar rats were used in the study. The effects of nicotine administration on miRNA-124 expression, as well as alpha-smooth muscle actin (liver fibrosis marker) and chemokine ligand 2 (an inflammatory chemokine), were investigated using RT-qPCR. In addition, the mRNA and protein expression of signal transducer and activator of transcription 3 (STAT-3; as a potential target for miRNA-124) were investigated by RT-qPCR and immunofluorescence, respectively. Liver enzyme activity levels were measured using a colorimetric assay. In addition, the effects of nicotine on the process of liver fibrosis were investigated with histological studies. RESULTS: The development of liver fibrosis in BDL rats and nicotine administration led to a decrease in miRNA-124 expression. The decrease in the expression is accompanied by the increase in the expression of fibrotic and proinflammatory genes. Also, an increase in STAT-3 mRNA and protein expression was observed in the fibrotic rats that received nicotine. In addition, the significant increase in bilirubin and liver enzymes in fibrotic rats worsens with nicotine administration. The results of histological studies also confirm these results. CONCLUSION: Considering that miRNA-124 is an anti-inflammatory miRNA, it can be concluded that the decrease in its expression due to nicotine exposure leads to an increase in inflammatory processes and subsequently to an increase in liver fibrosis.

Autophagy and UPS pathway contribute to nicotine-induced protection effect in Parkinson's disease.

The gradual nature of age-related neurodegeneration causes Parkinson's disease (PD) and impairs movement, memory, intellectual ability, and social interaction. One of the most prevalent neurodegenerative conditions affecting the central nervous system (CNS) among the elderly is PD. PD affects both motor and cognitive functions. Degeneration of dopaminergic (DA) neurons and buildup of the protein α-synuclein (α-Syn) in the substantia nigra pars compacta (SNpc) are two major causes of this disorder. Both UPS and ALS systems serve to eliminate α-Syn. Autophagy and UPS deficits, shortened life duration, and lipofuscin buildup accelerate PD. This sickness has no cure. Innovative therapies are halting PD progression. Bioactive phytochemicals may provide older individuals with a natural substitute to help delay the onset of neurodegenerative illnesses. This study examines whether nicotine helps transgenic C. elegans PD models. According to numerous studies, nicotine enhances synaptic plasticity and dopaminergic neuronal survival. Upgrades UPS pathways, increases autophagy, and decreases oxidative stress and mitochondrial dysfunction. At 100, 150, and 200 µM nicotine levels, worms showed reduced α-Syn aggregation, repaired DA neurotoxicity after 6-OHDA intoxication, increased lifetime, and reduced lipofuscin accumulation. Furthermore, nicotine triggered autophagy and UPS. We revealed nicotine's potential as a UPS and autophagy activator to prevent PD and other neurodegenerative diseases.

Cisplatin-resistance induces lung squamous carcinoma cell growth by nicotine-mediated α7nAchR/HDAC1/Cyclin D1/pRb cell cycle activation.

The majority of adenocarcinoma lung cancer is found in nonsmokers. A history of tobacco use is more common in squamous cell carcinoma of the lung. The aim of this study is to identify the cisplatin (CDDP)-resistance that promotes lung squamous carcinoma cell growth through nicotine-mediated HDAC1/7nAchR/E2F/pRb cell cycle activation. Squamous cell carcinoma (NCI-H520 and NCI-H157) cells were examined after cisplatin and nicotine treatment by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assay, cell migration assay, immunofluorescence staining, western blot analysis, and immunoprecipitation analysis. Consequently, CDDP is released from DNA and Rb phosphorylated pRb as a result of nicotine-induced cancer cell proliferation through 7nAchR, which then triggers the opening of the HDAC1 cell cycle. The cell cycle is stopped when CDDP adducts are present. Nicotine exerts cancer cytoprotective effects by allowing HDAC1 repair mechanisms to re-establish E2F promoting DNA stimulation cell cycle integrity in the cytosol and preventing potential CDDP and HDAC1 suppressed in the nuclear. Concentration expression of nicotine causes squamous carcinoma cell carcinogens to emerge from inflammation. COX2, NF-KB, and NOS2 increase as a result of nicotine-induced squamous carcinoma cell inflammation. Nicotine enhanced the cell growth-related proteins such as α7nAchR, EGFR, HDAC1, Cyclin D, Cyclin E, E2F, Rb, and pRb by western blot analysis. It also induced cancer cell inflammation and growth. As a result, we suggest that nicotine will increase the therapeutic resistance effects of CDDP. This has the potential to interact with nicotine through α7nAchR receptors and HDAC1/Cyclin D/E2F/pRb potentially resulting in CDDP therapy resistance, as well as cell cycle-induced cancer cell growth.

Auditory brainstem responses are resistant to pharmacological modulation in Sprague Dawley wild-type and Neurexin1α knockout rats.

Sensory processing in the auditory brainstem can be studied with auditory brainstem responses (ABRs) across species. There is, however, a limited understanding of ABRs as tools to assess the effect of pharmacological interventions. Therefore, we set out to understand how pharmacological agents that target key transmitter systems of the auditory brainstem circuitry affect ABRs in rats. Given previous studies, demonstrating that Nrxn1α KO Sprague Dawley rats show substantial auditory processing deficits and altered sensitivity to GABAergic modulators, we used both Nrxn1α KO and wild-type littermates in our study. First, we probed how different commonly used anesthetics (isoflurane, ketamine/xylazine, medetomidine) affect ABRs. In the next step, we assessed the effects of different pharmacological compounds (diazepam, gaboxadol, retigabine, nicotine, baclofen, and bitopertin) either under isoflurane or medetomidine anesthesia. We found that under our experimental conditions, ABRs are largely unaffected by diverse pharmacological modulation. Significant modulation was observed with (i) nicotine, affecting the late ABRs components at 90 dB stimulus intensity under isoflurane anesthesia in both genotypes and (ii) retigabine, showing a slight decrease in late ABRs deflections at 80 dB stimulus intensity, mainly in isoflurane anesthetized Nrxn1α KO rats. Our study suggests that ABRs in anesthetized rats are resistant to a wide range of pharmacological modulators, which has important implications for the applicability of ABRs to study auditory brainstem physiology.

Influence of age on nicotinic cholinergic regulation of blood flow in rat's olfactory bulb and neocortex.

The olfactory bulb receives cholinergic basal forebrain inputs as does the neocortex. With a focus on nicotinic acetylcholine receptors (nAChRs), this review article provides an overview and discussion of the following findings: (1) the nAChRs-mediated regulation of regional blood flow in the neocortex and olfactory bulb, (2) the nAChR subtypes that mediate their responses, and (3) their activity in old rats. The activation of the α4ß2-like subtype of nAChRs produces vasodilation in the neocortex, and potentiates olfactory bulb vasodilation induced by olfactory stimulation. The nAChR activity producing neocortical vasodilation was similarly maintained in 2-year-old rats as in adult rats, but was clearly reduced in 3-year-old rats. In contrast, nAChR activity in the olfactory bulb was reduced already in 2-year-old rats. Thus, age-related impairment of α4ß2-like nAChR function may occur earlier in the olfactory bulb than in the neocortex. Given the findings, the vasodilation induced by α4ß2-like nAChR activation may be beneficial for neuroprotection in the neocortex and the olfactory bulb.

The many enigmas of nicotine.

This review discusses the diverse effects of nicotine on the various nicotinic acetylcholine receptors of the central and peripheral nervous system and how those effects may promote the usage and addiction to tobacco products.

Modulators of nicotine reward and reinforcement.

Nicotine has been well-characterized for its ability to alter neurophysiology to promote rewarding and reinforcing properties. However, several exogenous chemicals possess properties that modulate or enhance nicotine's ability to alter neurophysiology. This chapter focuses on nicotine's impact on behavior through changes in neurophysiology and several chemical entities that in-turn modulate nicotine's ability to act as a neuromodulator.

Neuronal nicotinic acetylcholine receptor of the central amygdala modulates the ethanol-induced tolerance to anxiolysis and withdrawal-induced anxiety in male rats.

The nicotine acetylcholinergic receptor (nAchR) in the central nucleus of the amygdala (CeA) is known to modulate anxiety traits as well as ethanol-induced behavioral effects. Therefore, the present study investigated the role of CeA nAChR in the tolerance to ethanol anxiolysis and withdrawal-induced anxiety-related effects in rats on elevated plus maze (EPM). To develop ethanol dependence, rats were given free access to an ethanol-containing liquid diet for 10 days. To assess the development of tolerance, separate groups of rats were challenged with ethanol (2 g/kg, i.p.) on days 1, 3, 5, 7 and 10 during the period of ethanol exposure, followed by an EPM assessment. Moreover, expression of ethanol withdrawal was induced after switching ethanol-dependent rats to a liquid diet on day 11, and withdrawal-induced anxiety-like behavior was noted at different post-withdrawal time points using the EPM test. The ethanol-dependent rats were pretreated with intra-CeA (i.CeA) (bilateral) injections of nicotine (0.25 µg/rat) or mecamylamine (MEC) (5 ng/rat) before the challenge dose of ethanol on subthreshold tolerance on the 5th day or on peak tolerance day, that is, 7th or 10th, and before assessment of postwithdrawal anxiety on the 11th day on EPM. Bilateral i.CeA preadministration of nicotine before the challenge dose of ethanol on days 5, 7 and 10 exhibited enhanced tolerance, while injection of MEC, completely mitigated the tolerance to the ethanol-induced antianxiety effect. On the other hand, ethanol-withdrawn rats pretreated i.CeA with nicotine exacerbated while pretreatment with MEC, alleviated the ethanol withdrawal-induced anxiety on all time points. Thus, the present investigation indicates that stimulation of nAChR in CeA negatively modulates the ethanol-induced chronic behavioral effects on anxiety in rats. It is proposed that nAChR antagonists might be useful in the treatment of alcohol use disorder and ethanol withdrawal-related anxiety-like behavior.

Modulation of mGlu5 reduces rewarding associative properties of nicotine via changes in mesolimbic plasticity: Relevance to comorbid cigarette smoking in psychosis.

RATIONALE: Antipsychotic medications that are used to treat psychosis are often limited in their efficacy by high rates of severe side effects. Treatment success in schizophrenia is further complicated by high rates of comorbid nicotine use. Dopamine D2 heteroreceptor complexes have recently emerged as targets for the development of more efficacious pharmaceutical treatments for schizophrenia. OBJECTIVE: The current study sought to explore the use of the positive allosteric modulator of the mGlu5 receptor 3-Cyano-N-(1,3-diphenyl-1H-pyrazol-5-yl)benzamide (CDPPB) as a treatment to reduce symptoms related to psychosis and comorbid nicotine use. METHODS: Neonatal treatment of animals with the dopamine D2-like receptor agonist quinpirole (NQ) from postnatal day (P)1-21 produces a lifelong increase in D2 receptor sensitivity, showing relevance to psychosis and comorbid tobacco use disorder. Following an 8-day conditioning paradigm, brain tissue in the mesolimbic pathway was analyzed for several plasticity markers, including brain derived neurotrophic factor (BDNF), phosphorylated p70 ribosomal S6 kinase (phospho-p70S6K), and cadherin-13 (Cdh13). RESULTS: Pretreatment with CDPPB was effective to block enhanced nicotine conditioned place preference observed in NQ-treated animals. Pretreatment was additionally effective to block the nicotine-induced increase in BDNF and sex-dependent increases in cadherin-13 in the ventral tegmental area (VTA), as well as increased phospho-p70S6K in the nucleus accumbens (NAcc) shell found in NQ-treated animals. CONCLUSION: In conjunction with prior work, the current study suggests positive allosteric modulation of the mGlu5 receptor, an emerging target for schizophrenia therapeutics, may be effective for the treatment of comorbid nicotine abuse in psychosis.