Nicotinic Receptor Partial Agonist Research Articles

Stimulus mediation, specificity and impact of menthol in rats trained to discriminate puffs of nicotine e-cigarette aerosol from nicotine-free aerosol.

It is unclear if e-cigarettes have reduced abuse liability relative to traditional cigarettes, especially when considering advanced devices which deliver nicotine more efficiently. Translatable and predictive animal models are needed to addresses this question. Our goal was to explore the subjective stimulus effects of e-cigarettes by training rats to discriminate puffs of nicotine aerosol from vehicle aerosol using an aerosol delivery system designed to model e-cigarette use patterns in humans. Rats were trained to discriminate between ten, 10s puffs of aerosol generated from 3mg/ml nicotine e-liquid and nicotine-free e-liquid using a food-reinforced operant procedure. Following acquisition, tests were conducted to determine the specificity of the nicotine aerosol stimulus as well as the impact to the stimulus effects of nicotine resulting from the addition of menthol to e-liquid. Rats learned the nicotine aerosol puff vs vehicle puff discrimination in a mean of 25 training sessions. Injected nicotine fully substituted for the stimulus effects of nicotine aerosol. The stimulus effects of nicotine aerosol were blocked by the nicotinic receptor antagonist mecamylamine. The nicotinic receptor partial agonist, varenicline as well as the stimulant d-amphetamine substituted more robustly for nicotine aerosol puffs than did the NMDA antagonist, ketamine. Menthol enhanced the stimulus effects of nicotine aerosol without altering nicotine blood plasma levels. Nicotine aerosol puffs can function as a training stimulus in rats. The stimulus effects were CNS-mediated and receptor specific. Menthol appears to enhance the stimulus effects of nicotine aerosol through a pharmacodynamic rather than pharmacokinetic mechanism.

Reduction of nicotine and ethanol intake in alcohol-preferring (UChB) female rats by the α4β2 nicotinic acetylcholine receptor partial agonists 5-bromocytisine and cytisine

RationaleNeuronal nicotinic acetylcholine receptors (nAChRs) are implicated in the reinforcing effects of nicotine and ethanol. Previous studies have shown that cytisine and its 5-bromo derivative are partial agonists at the α4β2 nAChRs and that the parent molecule cytisine is effective in reducing both nicotine- and ethanol-self-administration in rats. However, whether 5-bromocytisine affects nicotine or ethanol self-administration was unknown. ObjectivesThe present study compared the effects of 5-bromocytisine and cytisine on nicotine self-administration and further assessed the effect of daily drug injection on voluntary ethanol consumption in alcohol-preferring female rats. Animals were administered a 1.5mg/kg i.p. dose of 5-bromocytisine or cytisine every day for 15–16 days. ResultsThe initial efficacy of 5-bromocytisine and cytisine in reducing nicotine intake was similar (−80%) while for voluntary ethanol intake 5-bromocytisine was a superior inhibitor over cytisine (−78% and −40% respectively). The efficacy of cytisine began to diminish after 10 days of daily administration, which was attributed to tolerance development to its inhibitory effects both on nicotine and ethanol self-administration. Tolerance did not develop for 5-bromocytisine. Conclusion5-Bromocytisine, a weaker α4β2 nAChR partial agonist than cytisine, also produces a sustained inhibition of both nicotine and ethanol self-administration, and unlike cytisine, it does not develop tolerance.

Nicotine receptor partial agonists for smoking cessation

Nicotine receptor partial agonists for smoking cessation

Cholinergic system adaptations are associated with cognitive function in people recently abstinent from smoking: a (-)-[18F]flubatine PET study.

The cholinergic system is a critical mediator of cognition in animals. People who smoke cigarettes exhibit cognitive deficits, especially during quit attempts. Few studies jointly examine the cholinergic system and cognition in people while trying to quit smoking. We used positron emission tomography (PET) brain imaging with the β2-subunit containing nicotinic acetylcholine receptor (β2*-nAChR) partial agonist radioligand (-)-[18F]flubatine and the acetylcholinesterase inhibitor physostigmine to jointly examine the cholinergic system, smoking status, and cognition. (-)-[18F]Flubatine scans and cognitive data were acquired from twenty people who recently stopped smoking cigarettes (aged 38 ± 11 years; 6 female, 14 male; abstinent 7 ± 1 days) and 27 people who never smoked cigarettes (aged 29 ± 8 years; 11 female, 16 male). A subset of fifteen recently abstinent smokers and 21 never smokers received a mid-scan physostigmine challenge to increase acetylcholine levels. Regional volume of distribution (VT) was estimated with equilibrium analysis at "baseline" and post-physostigmine. Participants completed a cognitive battery prior to (-)-[18F]flubatine injection and physostigmine administration assessing executive function (Groton Maze Learning test), verbal learning (International Shopping List test), and working memory (One Back test). Physostigmine significantly decreased cortical (-)-[18F]flubatine VT, consistent with increased cortical acetylcholine levels reducing the number of β2*-nAChR sites available for (-)-[18F]flubatine binding, at comparable magnitudes across groups (p values < 0.05). A larger magnitude of physostigmine-induced decrease in (-)-[18F]flubatine VT was significantly associated with worse executive function in people who recently stopped smoking (p values < 0.05). These findings underscore the role of the cholinergic system in early smoking cessation and highlight the importance of neuroscience-informed treatment strategies.

More on varenicline

Murray et al have written a timely, thoughtful, and useful article (“Smoking cessation: Varenicline and the risk of neuropsychiatric adverse events,” Current Psychiatry, July 2022, p. 41-45) about the role of the nicotinic acetylcholine receptor partial agonist varenicline for helping patients stop smoking, which is still the main preventable cause of morbidity and premature death.

Effectiveness of Varenicline and Cytisine for Alcohol Use Reduction Among People With HIV and Substance Use

Cigarette smoking and risky alcohol consumption co-occur and are undertreated. Nicotine receptor partial agonists and nicotine replacement therapy (NRT) treat smoking but are unproven for alcohol, and clinical trials rarely include individuals with HIV, substance use, and mental health conditions. To compare the effects on drinking and smoking of nicotinic acetylcholine receptor partial agonists varenicline and cytisine with those of NRT. This 4-group randomized, double-blinded, placebo-controlled clinical trial was conducted from July 2017 to December 2020 in St Petersburg, Russia. Included participants were 400 individuals with HIV who engaged in risky drinking (≥5 prior-month heavy-drinking days [HDDs]) and daily smoking; they were followed up for 12 months after enrollment. Data were analyzed from May 2021 through June 2022. Participants received alcohol and tobacco counseling, 1 active medication, and 1 placebo in 1 of 4 groups: active varenicline and placebo NRT (group 1), placebo varenicline and active NRT (group 2), active cytisine and placebo NRT (group 3), or placebo cytisine and active NRT (group 4). The primary outcome was number of prior-month HDDs at 3 months. Secondary outcomes included biochemically validated abstinence from alcohol at 3 months and smoking at 6 months. Among 400 participants (263 [65.8%] men; mean [SD] age, 39 [6] years), 97 individuals (24.3%) used opioids and 156 individuals (39.1%) had depressive symptoms. These individuals had a mean (SD) CD4 count of 391 (257) cells/mm3, smoked a mean (SD) of 21 [8] cigarettes/d, and reported a mean (SD) of 9.3 (5.8) HDDs in the prior 30 days. At 3 months, the mean (SD) number of HDDs was decreased vs baseline across all groups (group 1: 2.0 [3.8] HDDs vs. 9.5 [6.1] HDDs; group 2: 2.1 [4.3] HDDs vs 9.3 [5.7] HDDs; group 3: 1.5 [3.3] HDDs vs 8.9 [5.0] HDDs; group 4: 2.4 [5.2] HDDs vs 9.6 [6.3] HDDs). There were no significant differences at 3 months between groups in mean (SD) HDDs, including group 1 vs 2 (incident rate ratio [IRR], 0.94; 95% CI, 0.49-1.79), 3 vs 4 (IRR, 0.60; 95% CI, 0.30-1.18), and 1 vs 3 (IRR, 1.29; 95% CI, 0.65-2.55). There were no significant differences at 6 months between groups in smoking abstinence, including group 1 vs 2 (15 of 100 individuals [15.0%] vs 17 of 99 individuals [17.2%]; odds ratio [OR],0.89; 95% CI, 0.38-2.08), 3 vs 4 (19 of 100 individuals [19.0%] vs 19 of 101 individuals [18.8%]; OR, 1.00; 95% CI, 0.46-2.17), and 1 vs 3 (OR, 0.79; 95% CI, 0.35-1.78). Post hoc analyses suggested lower mean (SD) HDDs (eg, at 3 months: 0.7 [1.8] HDDs vs 2.3 [4.6] HDDs) and higher alcohol abstinence (eg, at 3 months: 30 of 85 individuals [35.3%] vs 54 of 315 individuals [17.1%]) among those who quit vs continued smoking. This study found that among individuals with HIV who engaged in risky drinking and smoking, varenicline and cytisine were not more efficacious than NRT to treat risky drinking and smoking but that behavior change rates were high in all groups. ClinicalTrials.gov Identifier: NCT02797587.

Interventions for preventing weight gain after smoking cessation.

Interventions for preventing weight gain after smoking cessation.

Linalool attenuates acquisition and reinstatement and accelerates the extinction of nicotine-induced conditioned place preference in male mice

ABSTRACT Background: Nicotine is the addictive agent in tobacco products. The monoterpene linalool is the main ingredient in the essential oils of various aromatic plants. It has previously been demonstrated that linalool has beneficial effects on some mechanisms that are important in drug addiction. Objectives: The goal of the current study was to investigate the effect of linalool on nicotine-induced conditioned place preference (CPP) in male mice. Methods: CPP was induced by administering intraperitoneal (i.p.) injection of nicotine (0.5 mg/kg) during the conditioning phase. The effects of nicotinic acetylcholine receptor partial agonist varenicline and linalool on the rewarding characteristics of nicotine were tested in mice with administration of linalool (12.5, 25, and 50 mg/kg, i.p.), varenicline (2 mg/kg, i.p.) or saline 30 minutes before nicotine injection. CPP was extinguished by repeated testing, during which conditioned mice were administered varenicline and linalool every day. One day after the last extinction trial, mice that received linalool, varenicline or saline 30 minutes before a priming injection of nicotine (0.1 mg/kg, i.p.) were immediately tested for reinstatement of CPP. Results: Linalool attenuated nicotine acquisition (50 mg/kg, p < .01) and reinstatement (25 and 50 mg/kg, respectively p < .05, p < .01) and accelerated the extinction of nicotine-induced CPP (50 mg/kg, p < .05). Linalool exhibited similar effects on the reference drug varenicline in the CPP phases. Conclusion: These results suggest that linalool may be helpful as an adjuvant for the treatment of nicotine use disorder.

A Multicenter, Double-Blind, Randomized, Placebo-Controlled Phase 2b Trial of Cytisinicline in Adult Smokers (The ORCA-1 Trial).

IntroductionCytisinicline (known as cytisine), a nicotinic acetylcholine receptor partial agonist, is a smoking cessation aid currently marketed in Central and Eastern Europe using a 1.5-mg/tablet 25-day downward titration schedule. No prior studies have evaluated other doses or administration schedules. This study evaluated the effects of a higher dosage and simplified dosing schedule on drug efficacy and tolerability.MethodsORCA-1 was a double-blind, randomized, placebo-controlled clinical trial that provided cytisinicline or placebo tablets plus behavioral support for 25 days. Adult smokers (>10 cigarettes daily) committed to quitting smoking were randomized to compare 2 cytisinicline doses (1.5 mg and 3 mg) versus placebo, and 2 administration schedules [downward titration versus 3 times daily (TID)]. Primary outcome was a reduction in expected cigarettes smoked at end of treatment; secondary outcomes were biochemically confirmed 7-day abstinence at Week 4 and continuous abstinence from Weeks 5 to 8.ResultsAmong 254 participants, those in cytisinicline arms (regardless of dose or schedule) had greater reductions in cigarettes smoked versus placebo, with differences observed in 3 cytisinicline arms statistically significant versus placebo. All cytisinicline arms had statistically significantly higher abstinence rates at Week 4 versus placebo. Both cytisinicline arms using TID schedules had statistically significantly higher continuous abstinence rates from Weeks 5 to 8 compared with placebo. Participants in the cytisinicline 3-mg TID arm had the highest abstinence rate. There were no safety concerns with either 1.5-mg or 3-mg cytisinicline.ConclusionBased on simpler dose scheduling, excellent tolerability, and best-continued abstinence rate, cytisinicline 3-mg TID was selected for future Phase 3 studies.ImplicationsAlthough the 1.5-mg 25-day titration schedule has been marketed in Central and Eastern Europe for decades, this study explored using a higher dosage and a simplified dosing schedule for impact on cytisinicline efficacy and tolerability. Based on these results, a Phase 3 program was initiated using cytisinicline 3-mg tablets on a TID schedule for potential market approval in the United States.

A double blind randomized controlled trial investigating efficacy and safety of varenicline for smoking cessation in patients with type 2 diabetes: study protocol

Reducing exposure to cigarette smoke is an imperative for public health and for diabetic patients. Patients with diabetes who continue to smoke face challenges at quitting and the delivery of effective smoking cessation interventions is a major unmet need. The high-affinity α4β2 nicotinic acetylcholine receptor partial agonist varenicline in combination with counseling is effective for smoking cessation, but evidence in patients with diabetes is limited. A clinical trial of varenicline targeted specifically at smokers with T2DM is warranted. This randomized, double blind, placebo-controlled trial will be the first study to test efficacy and safety of varenicline in smokers with type 2 diabetes mellitus (T2DM) over the course of 52 weeks. We hypothesize that varenicline treatment (1 mg BID, administered for 12 weeks) would increase quit rates, maintain smoking abstinence up to 1 year after treatment, and be well-tolerated in T2DM smokers intending to quit. Efficacy end points will include carbon monoxide–confirmed continuous abstinence rate (CAR) and 7-day point prevalence of abstinence. The results of this RCT will help inform medical/health authorities and physicians worldwide whether an optimally varenicline-treated cohort of T2DM patients who smoke will experience significant success rates, without significant side effects.Trial registration NCT01387425 (https://clinicaltrials.gov/ct2/show/NCT01387425).

Aged rhesus monkeys: Cognitive performance categorizations and preclinical drug testing

Rodent models have facilitated major discoveries in neurobiology, however, the low success rate of novel medications in clinical trials have led to questions about their translational value in neuropsychiatric drug development research. For age-related disorders of cognition such as Alzheimer’ disease (AD) there is interest in moving beyond transgenic amyloid-β and/or tau-expressing rodent models and focusing more on natural aging and dissociating “healthy” from “pathological” aging to identify new therapeutic targets and treatments. In complex disorders such as AD, it can also be argued that animals with closer neurobiology to humans (e.g., nonhuman primates) should be employed more often particularly in the later phases of drug development. The purpose of the work described here was to evaluate the cognitive capabilities of rhesus monkeys across a wide range of ages in different delayed response tasks, a computerized delayed match to sample (DMTS) task and a manual delayed match to position (DMTP) task. Based on specific performance criteria and comparisons to younger subjects, the older subjects were generally less proficient, however, some performed as well as young subjects, while other aged subjects were markedly impaired. Accordingly, the older subjects could be categorized as aged “cognitively-unimpaired” or aged “cognitively-impaired” with a third group (aged-other) falling in between. Finally, as a proof of principle, we demonstrated using the DMTP task that aged cognitively-impaired monkeys are sensitive to the pro-cognitive effects of a nicotinic acetylcholine receptor (nAChR) partial agonist, encenicline, suggesting that nAChR ligands remain viable as potential treatments for age-related disorders of cognition.

Enhancement of Opioid Antinociception by Nicotinic Ligands.

Nicotine has previously been shown to augment the antinociceptive effects of μ-opioid agonists in squirrel monkeys without producing a concomitant increase in behavioral disruption. The present studies were conducted to extend these findings by determining the ability of the nicotinic acetylcholine receptor (nAChR) agonist epibatidine and partial α4β2 nAChR agonist varenicline to selectively augment the antinociceptive effects of the μ-opioid receptor (MOR) full agonist fentanyl, the MOR partial agonist nalbuphine, and the κ-opioid receptor (KOR) agonist U69,593 in male squirrel monkeys. Results indicate that both nAChR ligands selectively increased the antinociceptive effects of nalbuphine and that epibatidine increased the antinociceptive effects of U69,593 without altering effects on operant behavior. However, neither epibatidine nor varenicline enhanced the antinociceptive effects of fentanyl, perhaps due to its high efficacy. The enhancement of nalbuphine's antinociceptive effects by epibatidine, but not varenicline, could be antagonized by either mecamylamine or dihydro-β-erythroidine, consistent with α4β2 mediation of epibatidine's effects but suggesting the involvement of non-nAChR mechanisms in the effects of varenicline. The present results support previous findings showing that an nAChR agonist can serve as an adjuvant for MOR antinociception and, based on results with U69,593, further indicate that the adjuvant effects of nAChR drugs may also apply to antinociception produced by KOR. Our findings support the further evaluation of nAChR agonists as adjuvants of opioid pharmacotherapy for pain management and point out the need for further investigation into the mechanisms by which they produce opioid-adjuvant effects. SIGNIFICANCE STATEMENT: Nicotine has been shown to augment the antinociceptive effects of μ-opioid receptor analgesics without exacerbating their effects on operant performance. The present study demonstrates that the nicotinic acetylcholine receptor (nAChR) agonist epibatidine and partial α4β2 nAChR agonist varenicline can also augment the antinociceptive effects of nalbuphine, as well as those of a κ-opioid receptor agonist, without concomitantly exacerbating their behaviorally disruptive effects. These findings support the view that nAChR agonists and partial agonists may have potential as adjuvant therapies for opioid-based analgesics.

CE: The Effects of Smoking on Bone Health and Healing.

The number of orthopedic surgeries performed in the United States has increased substantially over the past several years. The most recent data available from the Agency for Healthcare Research and Quality indicate that five of the 10 operative procedures most commonly performed during inpatient stays involve the musculoskeletal system. Cigarette smoking is one of the most prevalent and preventable risk factors for musculoskeletal disorders and orthopedic surgery complications. This article discusses the effects of smoking on bone health, the importance of smoking cessation among patients scheduled for or recovering from orthopedic surgery, and the vital role nurses play in supporting patient efforts to lead a tobacco-free life.

Validation of a nicotine vapor self-administration model in rats with relevance to electronic cigarette use.

The debate about electronic cigarettes is dividing healthcare professionals, policymakers, manufacturers, and communities. A key limitation in our understanding of the cause and consequences of vaping is the lack of animal models of nicotine vapor self-administration. Here, we developed a novel model of voluntary electronic cigarette use in rats using operant behavior. We found that rats voluntarily exposed themselves to nicotine vapor to the point of reaching blood nicotine levels that are similar to humans. The level of responding on the active (nicotine) lever was similar to the inactive (air) lever and lower than the active lever that was associated with vehicle (polypropylene glycol/glycerol) vapor, suggesting low positive reinforcing effects and low nicotine vapor discrimination. Lever pressing behavior with nicotine vapor was pharmacologically prevented by the α4β2 nicotinic acetylcholine receptor partial agonist and α7 receptor full agonist varenicline in rats that self-administered nicotine but not vehicle vapor. Moreover, 3 weeks of daily (1 h) nicotine vapor self-administration produced addiction-like behaviors, including somatic signs of withdrawal, allodynia, anxiety-like behavior, and relapse-like behavior after 3 weeks of abstinence. Finally, 3 weeks of daily (1 h) nicotine vapor self-administration produced cardiopulmonary abnormalities and changes in α4, α3, and β2 nicotinic acetylcholine receptor subunit mRNA levels in the nucleus accumbens and medial prefrontal cortex. These findings validate a novel animal model of nicotine vapor self-administration in rodents with relevance to electronic cigarette use in humans and highlight the potential addictive properties and harmful effects of chronic nicotine vapor self-administration.

Cytyzyna w terapii zaprzestania palenia tytoniu

Tobacco smoking is one of the leading causes of death among people. Cytisine, a plant alkaloid considered to be the oldest medication for smoking cessation, has been used in Poland since the 1970s. The drug is a partial nicotinic receptor agonist, with pharmacological actions close to those of nicotine and varenicline (a synthetic cytisine derivative and most expensive smoking cessation medication currently available). Cytisine has several advantages compared to existing smoking cessation drugs, including: 1) it is more effective than placebo and nicotine replacement therapy, and at least as effective as varenicline, 2) its use is associated with a low frequency of adverse events, 3) it is available as over the counter medicine and is much cheaper than other smoking cessation drugs that are cost-prohibitive, 4) it derives from a natural plant and may be preferred by smokers who do not want to use other treatments, 5) it has shorter duration of treatment (i.e. 25 days) compared to other medicines for smoking cessation. This review describes the use of cytisine for nicotine addiction treatment, mechanism of anti-smoking action, pharmacokinetics, efficacy, tolerability and safety.

Countering Opioid-induced Respiratory Depression in Male Rats with Nicotinic Acetylcholine Receptor Partial Agonists Varenicline and ABT 594.

Opioids can induce significant respiratory depression when administered as analgesics for the treatment of acute, postoperative, and chronic pain. There are currently no pharmacologic means of reversing opioid-induced respiratory depression without interfering with analgesia. Further, there is a growing epidemic of opioid overdose that could benefit from therapeutic advancements. The aim of this study was to test the ability of two partial agonists of α4β2 nicotinic acetylcholine receptors, varenicline (used clinically for smoking cessation) and ABT 594 (tebanicline, developed as an analgesic), to reduce respiratory depression induced by fentanyl, remifentanil, morphine, and a combination of fentanyl and diazepam. Whole body plethysmographic recordings, nociception testing, and righting reflex testing were used to examine ventilation, analgesia, and sedation in adult male Sprague-Dawley rats. Pre-, co-, or postadministration of varenicline or ABT 594 did not alter baseline breathing but markedly reduced opioid-induced respiratory depression. Varenicline had no effect on fentanyl-induced analgesia and ABT 594 potentiated fentanyl-induced analgesia. Specifically, 10-min administration of fentanyl induced a decrease in respiratory rate to 43 ± 32% of control in vehicle group, which was alleviated by preadministration of varenicline (85 ± 14% of control, n = 8, P < 0.001) or ABT 594 (81 ± 36% of control, n = 8, P = 0.001). ABT 594 or varenicline with a low dose of naloxone (1 µg/kg), but not varenicline alone, partially reversed fentanyl-induced lethal apnea, but neither compound provided the very rapid and complete reversal of apnea achieved with high doses of naloxone (0.03 to 1 mg/kg). Administration of varenicline (n = 4, P = 0.034) or ABT 594 (n = 4, P = 0.034) prevented lethal apneas induced by the combination of fentanyl and diazepam. Activation of α4β2 nicotinic acetylcholine receptors by varenicline and ABT 594 counters opioid-induced respiratory depression without interfering with analgesia.

The Relationship of Varenicline Agonism of α4β2 Nicotinic Acetylcholine Receptors and Nicotine-Induced Dopamine Release in Nicotine-Dependent Humans.

Cigarette smoking continues to be one of the most important behavioral causes of morbidity and mortality in the world. Varenicline, an α4β2 nicotinic acetylcholine receptor (nAChR) partial agonist, has been shown to increase smoking quit rates compared with nicotine-based products. This human laboratory, double-blind, placebo-controlled study examined varenicline and placebo effects on α4β2-nAChRs occupancy, nicotine-induced change in [11C]raclopride non-displaceable binding potential (BPND), and behavioral measures of cigarette smoking, nicotine craving, and withdrawal. Current nicotine dependent daily smokers (N = 17) were randomized to varenicline 1 mg twice daily or placebo for 13 days. Using positron emission tomography), we characterized α4β2-nAChRs occupancy using [18F]AZAN and dopamine receptor binding using [11C]raclopride as well as behavioral measures of cigarettes smoked, craving, and nicotine withdrawal. Varenicline compared with placebo resulted in significant reductions in [18F]AZAN BPND in multiple brain regions including thalamus, midbrain, putamen, and ventral striatum. Following administration of a controlled-dose nicotine cigarette, dopamine release was significantly suppressed in the ventral striatum in the varenicline-treated compared with the placebo group. There was a significant relationship between α4β2-nAChRs BPND measured in thalamus during the [18F]AZAN scan and nicotine-induced change in raclopride BPND in the ventral striatum. This is the first human study to demonstrate a direct relationship between the extent of varenicline occupancy of α4β2-nAChRs and the magnitude of dopamine release following nicotine use. It has remained unclear how nicotinic receptor blockade through partial agonist medications such as varenicline promotes smoking cessation. One hypothesized mechanism is downstream dampening of the mesolimbic reward dopamine system. For the first time in human smokers, we observed a direct relationship between the extent of varenicline blockade of α4β2-nACh nicotinic receptors and the magnitude of dopamine release following smoking. This has mechanistic and therapeutic implications for improving smoking cessation interventions.

Journal Club-Electronic Cigarettes and Vaping as a Harm Reduction Alternative: Really?

Journal Club-Electronic Cigarettes and Vaping as a Harm Reduction Alternative: Really?

Network meta-analysis: a comparison of effectiveness and safety of partial agonists of nicotinic acetylcholine receptors varenicline and cytisine for smoking cessation

Background. Partial agonists of α4b2 nicotinic acetylcholine receptors are the most effective treatment strategy for tobacco smoking cessation. They are able to alleviate withdrawal symptoms and to reduce smoking satisfaction.&#x0D; The aim of this study was to review the efficacy and safety of nicotinic receptor partial agonists varenicline and cytisine, for smoking cessation.&#x0D; Methods. A search for randomized controlled trials was done using the terms (“cytisine”, “tabex”, “varenicline” or 'partial agonists of nicotinic receptors’) in MEDLINE, EMBASE, eLibrary in May 2018. Types of participants, the doses and duration of the treatments, efficacy and safety parameters, quality of randomization and blinding procedures were evaluated. Bayesian network meta-analysis was performed.&#x0D; Results. Cytisine overcame placebo in the 12, 24 and 52 weeks of therapy with the following odds ratios (ORs) for abstinence: 3.3 (95% CrI 1.8–5.8), 3.9 (2.4–6.7), 3.8 (CrI 1.3–11,9) accordingly. Varenicline in 2 mg/day dose overcame placebo in the 12, 24 and 52 weeks of therapy with the ORs: 4.0 (3.3–4.7), 3.1 (2.5–3.7), 2.9 (2.2–4.1) accor dingly. Varenicline in 1 mg/day dose overcame placebo in 12 and 52 weeks of therapy, the ORs were 3.0 (2.0–4.7) and 2.3 (1.3–4.4) accordingly. Varenicline in 0.5 mg/day dose overcame placebo in 12 weeks of therapy only with the OR 2.4 (1.3–4.4). Cytisine and varenicline 2 mg/day were associated with more gastrointestinal disturbances than placebo with the ORs 6.2 (2.1–22.8) and 2.4 (2.0–2.8) accordingly. Cytisine and varenicline 2 mg/day were associated with more psychiatric problems than placebo with ORs 5.2 (1.9–15.1) and 1.6 (1.3–1.9) accordingly. There was no difference in serious adverse events between the investigated drugs and placebo: OR for cytisine was 2.4 (0.8–6.8), varenicline 0.5 mg/day – 2.0 (0.5–6.6), varenicline 1.0 mg/day – 1.0 (0.3–2.7), varenicline 2 mg/day – 1.0 (0.7–1.4).&#x0D; Conclusion. Cytisine was proved to be as effective and safe aid for smoking cessation as varenicline.

Dyskinesia and brain-derived neurotrophic factor levels after long-term levodopa and nicotinic receptor agonist treatments in female mice with near-total unilateral dopaminergic denervation

BackgroundThe treatment of Parkinson’s disease is often complicated by levodopa-induced dyskinesia (LID). Nicotinic acetylcholine receptor agonists can alleviate LID in animal models but may be less effective in conditions of severe dopaminergic denervation. While the mechanisms of LID remain incompletely understood, elevated corticostriatal levels of the brain-derived neurotrophic factor (BDNF) have been suggested to play a role. Here, female mice with near-total unilateral 6-hydroxydopamine-induced nigrostriatal lesions were chronically treated with levodopa, and the effects of the α7 nicotinic receptor partial agonist AZD0328 and nicotine on LID were assessed. At the end of the experiment, BDNF protein levels in the prefrontal cortex and striatum were measured.ResultsFive-day treatments with three escalating doses of AZD0328 and a 10-week treatment with nicotine failed to alleviate LID. BDNF levels in the lesioned striatum correlated positively with LID severity, but no evidence was found for a levodopa-induced elevation of corticostriatal BDNF in the lesioned hemisphere. The nicotine treatment decreased BDNF levels in the prefrontal cortex but had no effect on striatal BDNF.ConclusionsThe findings suggest that treatment of LID with nicotinic agonists may lose its effectiveness as the disease progresses, represent further evidence for a role for BDNF in LID, and expand previous knowledge on the effects of long-term nicotine treatment on BDNF.