Receptor Partial Agonist Varenicline Research Articles

The actions of varenicline on alkaloids from Conium maculatum (poison hemlock), Lupinus sulphureus (sulphur lupine) and Nicotiana glauca (tree tobacco).

Evidence-based therapies to manage the clinical signs of intoxication caused by toxic plants in livestock are lacking. For that reason, the aim of this work was to develop a drug-based intervention for the management of clinical signs of piperidine alkaloid intoxication in livestock. The actions of anabasine, coniine, γ-coniceine, and two total alkaloid extracts from Lupinus sulphureus were compared in the presence and absence of the nicotinic acetylcholine receptor partial agonist varenicline in RD cells, mice and goats. Pretreatment of RD cells with 10.0μM varenicline significantly shifted the anabasine fifty percent effective concentration (EC50) value to a greater concentration and blocked the response of the cells to coniine. γ-coniceine did not have any effect on RD cells as measured by membrane potential sensing dye. Swiss Webster mice median lethal dose (LD50) values for anabasine, coniine, γ-coniceine were 1.5, 5.5, and 3.7mg/kg respectively, and pretreatment with 10.0mg/kg i. p. dosed varenicline shifted the LD50 values to 4.2, 9.1, and 4.3mg/kg respectively. The rodent LD50 value of the Pendelton, WA L. sulphureus quinolizidine alkaloid extract was shifted to a lesser concentration by varenicline while the Ritzville, WA L. sulphureus piperidine alkaloid extract was shifted to a greater concentration by varenicline. The clinical signs of intoxication in goats orally dosed with Conium maculatum were exacerbated by 0.5, 1.0 and 10.0mg/kg i. v. dosed varenicline. These results suggest that varenicline was effective at shifting piperidine alkaloid EC50 values in RD cells and increasing piperidine but not quinolizidine alkaloid LD50 values in mice and was not useful at managing the clinical signs of poison hemlock intoxication in goats.

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.

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 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).

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.

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.

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.

Compromised neuroplasticity in cigarette smokers under nicotine withdrawal is restituted by the nicotinic \u03b14\u03b22-receptor partial agonist varenicline

Nicotine modulates neuroplasticity and improves cognitive functions in animals and humans. In the brain of smoking individuals, calcium-dependent plasticity induced by non-invasive brain stimulation methods such as transcranial direct current stimulation (tDCS) and paired associative stimulation (PAS) is impaired by nicotine withdrawal, but partially re-established after nicotine re-administration. In order to investigate the underlying mechanism further, we tested the impact of the α4β2-nicotinic receptor partial agonist varenicline on focal and non-focal plasticity in smokers during nicotine withdrawal, induced by PAS and tDCS, respectively. We administered low (0.3 mg) and high (1.0 mg) single doses of varenicline or placebo medication before stimulation over the left motor cortex of 20 healthy smokers under nicotine withdrawal. Motor cortex excitability was monitored by single-pulse transcranial magnetic stimulation-induced motor evoked potential amplitudes for 36 hours after plasticity induction. Stimulation-induced plasticity was absent under placebo medication, whereas it was present in all conditions under high dose. Low dose restituted only tDCS-induced non-focal plasticity, producing no significant impact on focal plasticity. High dose varenicline also prolonged inhibitory plasticity. These results are comparable to the impact of nicotine on withdrawal-related impaired plasticity in smokers and suggest that α4β2 nicotinic receptors are relevantly involved in plasticity deficits and restitution in smokers.

Pharmacodynamic and pharmacokinetic profiles of the α4β2 nicotinic acetylcholine receptor partial agonist varenicline, a smoking cessation aid

This review describes the role of α 4 β 2 containing nicotinic acetylcholine receptors in the mesolimbic reward pathway in the neurobiology of nicotine addiction and discusses the rationale for targeting this receptor with partial agonists as novel smoking cessation agents. Varenicline is a α 4 β 2 nicotinic acetylcholine receptor partial agonist that is a smoking cessation aid with a dual mechanism of action: relief of craving and withdrawal symptoms, as well as attenuation of nicotine reinforcement. The pharmacological profile of varenicline is consistent with that of a potent and selective partial agonist at the target receptor, both in in vitro and in vivo neurochemical and behavioral models. Varenicline was nominated for full clinical development in 1997, and later approved in the US and Europe as a smoking cessation aid in 2006. The recommended dose of varenicline is 1 mg BID for 12 weeks after an initial titration week in adult smokers motivated to stop smoking. The pharmacokinetics of varenicline is linear and consistent regardless of smoking status, age, gender or ethnic background. Varenicline is largely eliminated unchanged in the urine, and consequently a dose adjustment is warranted for patients with severe renal insufficiency. Although varenicline is currently not approved for use in smokers under age 18, its pharmacokinetic and tolerability profile in adolescents appeared generally similar to adults. Several large clinical trials have consistently shown the efficacy, tolerability and safety of varenicline in various ethnic smoking populations and in adult smokers with co-morbid chronic pulmonary or cardiovascular disease. Additional clinical studies in special patient populations are currently ongoing.

Pharmacodynamic and pharmacokinetic profiles of the α4β2 nicotinic acetylcholine receptor partial agonist varenicline, a smoking cessation aid

Pharmacodynamic and pharmacokinetic profiles of the α4β2 nicotinic acetylcholine receptor partial agonist varenicline, a smoking cessation aid

Concurrent access to nicotine and sucrose in rats.

Animal models that allow concurrent access to drug and nondrug reinforcers provide unique insight into the etiology, maintenance, and treatment of drug use. We sought to develop and utilize a concurrent access procedure with nicotine and sucrose in rats. Pressing one lever delivered intravenous nicotine, and pressing another lever delivered sucrose pellets, with both reinforcers freely available throughout daily sessions. Rats that had been pretrained with nicotine on some days and sucrose on other days responded on both levers when subsequently given concurrent access, but almost all responded at substantially higher rates on the sucrose lever. In contrast, rats pretrained exclusively with nicotine before being given concurrent access showed individual differences, with about half responding more on the nicotine lever. Treatment with the nicotinic receptor partial agonist varenicline selectively decreased nicotine self-administration. Food restriction and removal of the sucrose lever both increased nicotine self-administration. The finding that rats continue to take nicotine when sucrose is concurrently available-and in many cases take it more frequently than sucrose-demonstrates that nicotine self-administration does not only occur in the absence of alternative reinforcement options. As a model of human nicotine use, concurrent access is more naturalistic and has higher face validity than procedures in which only one reinforcer is available or choosing one reinforcer precludes access to other reinforcers. As such, this procedure could be useful for evaluating therapeutic agents and improving our understanding of environmental conditions that promote or discourage nicotine use.

Effect of the Nicotinic α4β2-receptor Partial Agonist Varenicline on Non-invasive Brain Stimulation-Induced Neuroplasticity in the Human Motor Cortex.

Nicotine alters cognitive functions in animals and humans most likely by modification of brain plasticity. In the human brain, it alters plasticity induced by transcranial direct current stimulation (tDCS) and paired associative stimulation (PAS), probably by interference with calcium-dependent modulation of the glutamatergic system. We aimed to test this hypothesis further by exploring the impact of the α4β2-nicotinic receptor partial agonist varenicline on focal and non-focal plasticity, induced by PAS and tDCS, respectively. We administered low (0.1 mg), medium (0.3 mg), and high (1.0 mg) single doses of varenicline or placebo medication before PAS or tDCS on the left motor cortex of 25 healthy non-smokers. Corticospinal excitability was monitored by single-pulse transcranial magnetic stimulation-induced motor evoked potential amplitudes up to 36 h after plasticity induction. Whereas low-dose varenicline had no impact on stimulation-induced neuroplasticity, medium-dose abolished tDCS-induced facilitatory after-effects, favoring focal excitatory plasticity. High-dose application preserved cathodal tDCS-induced excitability diminution and focal excitatory PAS-induced facilitatory plasticity. These results are comparable to the impact of nicotine receptor activation and might help to further explain the involvement of specific receptor subtypes in the nicotinic impact on neuroplasticity and cognitive functions in healthy subjects and patients with neuropsychiatric diseases.

Varenicline effects on drinking, craving and neural reward processing among non-treatment-seeking alcohol-dependent individuals

The α4β2 nicotinic acetylcholine receptor partial agonist varenicline has been reported to reduce drinking among both heavy-drinking smokers and primary alcoholics, and this effect may be related to varenicline-mediated reduction of alcohol craving. Among smokers, varenicline has been reported to modulate cigarette cue-elicited brain activation in several reward-related areas. This pilot study tested varenicline's effects on drinking, alcohol craving, and alcohol cue-elicited activation of reward-related brain areas among non-treatment-seeking alcohol-dependent individuals. Thirty-five such individuals (mean age = 30, 57 % male, 76 % heavy drinking days in the past month, 15 smokers) were randomized to either varenicline (titrated to 2 mg) or placebo for 14 days, and were administered an alcohol cue reactivity fMRI task on day 14. A priori regions of interest (ROIs) were bilateral and medial orbitofrontal cortex (OFC), right ventral striatum (VS), and medial prefrontal cortex (mPFC). Despite good medication adherence, varenicline did not reduce heavy drinking days or other drinking parameters. It did, however, increase self-reported control over alcohol-related thoughts and reduced cue-elicited activation bilaterally in the OFC, but not in other brain areas. These data indicate that varenicline reduces alcohol craving and some of the neural substrates of alcohol cue reactivity. However, varenicline effects on drinking mediated by cue-elicited brain activation and craving might be best observed among treatment-seekers motivated to reduce their alcohol consumption.

The Smoking Cessation Aid Varenicline (Chantix, Champix): Drug Discovery Inspired by Natural Products

Tobacco use remains the single largest preventable cause of morbidity in the United States, with approximately 440,000 premature deaths each year from smoking-related illnesses, such as cardiovascular disease, multiple types of cancer and pulmonary disease. The search for medications to assist people with their quit attempts has led to the introduction of three FDA approved first-line medications: 'safe' nicotine (Nicotine Replacement Therapy) in 1984, the antidepressant bupropion (Zyban) in 1997, and the α4β2 nicotinic acetylcholine receptor (nAChR) partial agonist varenicline (Chantix, Champix) in 2006.

P4‐313: A placebo‐controlled crossover trial of the ±4β2 nicotinic acetylcholine receptor partial agonist varenicline in Alzheimer's disease

P4‐313: A placebo‐controlled crossover trial of the ±4β2 nicotinic acetylcholine receptor partial agonist varenicline in Alzheimer's disease

Neuronal Nicotinic Acetylcholine Receptors (nAChRs) Are Involved in Nicotine‐Mediated Reversal of Ataxia in an Animal Model

Clinical data indicate that the neuronal nicotinic acetylcholine receptor (nAChR) partial agonist varenicline ameliorates abnormalities in gait and balance in patients with spinocerebellar ataxia type 3, but the mechanisms involved have not been investigated. The goal of this study was to determine whether nicotine (Nic) could improve gait in an animal model of ataxia and whether this effect was mediated by an action at nAChRs. Following baseline assessment of locomotor activity and gait, male Sprague‐Dawley rats received injections of the neurotoxin 3‐acetylpyridine (3‐AP) to preferentially destroy the olivocerebellar pathway, and behaviors were reassessed one week later. Subsequently, animals received daily injections of either saline or mecamylamine (Mec, 1 mg/kg), followed 30 minutes later by either saline or Nic (1 mg/kg) for 1 week. The administration of 3‐ AP led to a 21–23% decrease in distance moved and velocity of movement, an 8% decrease in hindpaw stride length and a 25% increase stride width. Nic administration for 1 week did not alter locomotor activity or velocity, but did improve hindpaw stride length and width, effects that were prevented by prior Mec administration. Results indicate that activation of nAChRs is of benefit in an animal model of olivocerebellar degeneration. Current experiments are determining the specific nAChRs involved and the cellular mechanism mediating this effect. Supported by NIH #NS072114‐01

The nicotinic acetylcholine receptor partial agonist varenicline increases the ataxic and sedative-hypnotic effects of acute ethanol administration in C57BL/6J mice.

The costs associated with alcohol abuse are staggering, therefore much effort has been put into developing new pharmacologic strategies to decrease alcohol abuse. Recently, the nicotinic acetylcholine receptor (nAChR) partial agonist varenicline has been shown to decrease ethanol consumption in both humans and animal models. We examined the effects of varenicline on the ataxic and sedative-hypnotic effects of ethanol. First, varenicline was administered prior to placement in a locomotor activity chamber to determine whether varenicline influenced baseline locomotor activity. To determine the effect of nicotinic modulation on ethanol-induced motor incoordination, varenicline was administered 30 minutes prior to an acute ethanol injection and then mice were tested on the balance beam, dowel test, or fixed-speed rotarod. To examine ethanol's sedative-hypnotic effects, varenicline was administered 30 minutes prior to 4 g/kg ethanol and the duration of loss of righting reflex (LORR) was measured. Varenicline markedly reduced baseline locomotor activity in C57BL/6J mice. Varenicline increased ethanol-induced ataxia when measured on the balance beam and dowel test but had no effect when measured on the fixed-speed rotarod. Pretreatment with varenicline increased the duration of LORR. These data provide evidence that nAChRs may be involved in the ataxic and sedative effects of ethanol. It is possible that one mechanism that could contribute to the ability of varenicline to decrease ethanol consumption may be through increasing negative behavioral effects of alcohol.