RESUMO
Although α2 was the first neuronal nicotinic acetylcholine receptor (nAChR) receptor subunit to be cloned, due to its low level of expression in rodent brain, its study has largely been neglected. This study provides a comparison of the α2 and α4 structures and their functional similarities, especially in regard to the existence of low and high sensitivity forms based on subunit stoichiometry. We show that the pharmacological profiles of the low and high sensitivity forms of α2ß2 and α4ß2 receptors are very similar in their responses to nicotine, with high sensitivity receptors showing protracted responses. Sazetidine A, an agonist that is selective for the high sensitivity α4 receptors also selectively activates high sensitivity α2 receptors. Likewise, α2 receptors have similar responses as α4 receptors to the positive allosteric modulators (PAMs) desformylflustrabromine (dFBr) and NS9283. We show that the partial agonists for α4ß2 receptors, cytisine and varenicline are also partial agonists for α2ß2 receptors. Studies have shown that levels of α2 expression may be much higher in the brains of primates than those of rodents, suggesting a potential importance for human therapeutics. High-affinity nAChR have been studied in humans with PET ligands such as flubatine. We show that flubatine has similar activity with α2ß2 and α4ß2 receptors so that α2 receptors will also be detected in PET studies that have previously presumed to selectively detect α4ß2 receptors. Therefore, α2 receptors need more consideration in the development of therapeutics to manage nicotine addiction and declining cholinergic function in age and disease.
Assuntos
Agonistas Nicotínicos , Receptores Nicotínicos , Receptores Nicotínicos/metabolismo , Receptores Nicotínicos/genética , Animais , Agonistas Nicotínicos/farmacologia , Humanos , Nicotina/farmacologia , Nicotina/metabolismo , Xenopus laevis , Azetidinas/farmacologia , Quinolizinas/farmacologia , Vareniclina/farmacologia , Azocinas/farmacologia , Alcaloides Quinolizidínicos , PiridinasRESUMO
PURPOSE/BACKGROUND: People who smoke cigarettes and drink alcohol heavily are less likely to quit smoking compared with those who do not drink heavily. The current study examined the effects of a 12-week treatment phase of combination varenicline and nicotine patch compared with placebo and nicotine patch on smoking cessation (primary outcome) and alcohol consumption (secondary outcome) in heavy drinking smokers at 26-week follow-up. METHODS/PROCEDURES: Participants were daily smokers who met heavy drinking criteria. They were randomly assigned to receive either varenicline and nicotine patch (n = 61) or placebo and nicotine patch (n = 61) for 12 weeks. At week 26, self-reports of point prevalence cigarette abstinence were biochemically confirmed, and past-month alcohol drinking days and heavy drinking days were assessed. FINDINGS/RESULTS: At week 26, smoking quit rates did not differ by treatment group (25% varenicline and 26% placebo). Relative to week 12 outcomes, week 26 quit rates significantly dropped off in the varenicline group but not in the placebo group. Alcohol drinking reductions for the whole sample that were previously observed from baseline to week 12 were sustained at week 26, although they did not differ between treatment groups. IMPLICATIONS/CONCLUSIONS: In heavy drinking smokers, smoking cessation success was evident in a quarter of the total sample at 3 months postmedication discontinuation. At this time, quit rates were the same between those who received varenicline and nicotine patch and those who received nicotine patch alone. Future research is warranted to examine what may aid in longer-term smoking quit rates in heavy drinking smokers.
Assuntos
Consumo de Bebidas Alcoólicas , Agentes de Cessação do Hábito de Fumar , Abandono do Hábito de Fumar , Dispositivos para o Abandono do Uso de Tabaco , Vareniclina , Humanos , Vareniclina/administração & dosagem , Vareniclina/farmacologia , Abandono do Hábito de Fumar/métodos , Masculino , Feminino , Adulto , Pessoa de Meia-Idade , Seguimentos , Agentes de Cessação do Hábito de Fumar/administração & dosagem , Quimioterapia Combinada , Resultado do Tratamento , Agonistas Nicotínicos/administração & dosagem , Método Duplo-CegoRESUMO
BACKGROUND: Varenicline is considered one of the most effective treatment options for smoking cessation. Nonetheless, it is only modestly effective. A deeper comprehension of the effects of varenicline by means of the in-depth review of relevant fMRI studies may assist in paving the development of more targeted and effective treatments. METHODOLOGY: A search of PubMed and Google Scholar databases was conducted with the keywords "functional magnetic resonance imaging" or "fMRI", and "varenicline". All peer-reviewed articles regarding the assessment of smokers with fMRI while undergoing treatment with varenicline and meeting the predefined criteria were included. RESULTS: Several studies utilizing different methodologies and targeting different aspects of brain function were identified. During nicotine withdrawal, decreased mesocorticolimbic activity and increased amygdala activity, as well as elevated amygdala-insula and insula-default-mode-network functional connectivity are alleviated by varenicline under specific testing conditions. However, other nicotine withdrawal-induced changes, including the decreased reward responsivity of the ventral striatum, the bilateral dorsal striatum and the anterior cingulate cortex are not influenced by varenicline suggesting a task-dependent divergence in neurocircuitry activation. Under satiety, varenicline treatment is associated with diminished cue-induced activation of the ventral striatum and medial orbitofrontal cortex concomitant with reduced cravings; during the resting state, varenicline induces activation of the lateral orbitofrontal cortex and suppression of the right amygdala. CONCLUSIONS: The current review provides important clues with regard to the neurobiological mechanism of action of varenicline and highlights promising research opportunities regarding the development of more selective and effective treatments and predictive biomarkers for treatment efficacy.
Assuntos
Abandono do Hábito de Fumar , Síndrome de Abstinência a Substâncias , Humanos , Vareniclina/farmacologia , Vareniclina/uso terapêutico , Abandono do Hábito de Fumar/métodos , Nicotina , Imageamento por Ressonância Magnética , Agonistas Nicotínicos/uso terapêutico , Encéfalo/diagnóstico por imagemRESUMO
The cognitive impairments that are often observed in patients with alcohol use disorder (AUD) partially contribute to the extremely low rates of treatment initiation and adherence. Brain acetylcholine receptors (AChR) mediate and modulate cognitive and reward-related behavior, and their distribution can be altered by long-term heavy drinking. Therefore, AChRs are promising pharmacotherapeutic targets for treating the cognitive symptoms of AUD. In the present study, the procognitive efficacy of two AChR agonists, xanomeline and varenicline, were evaluated in group-housed monkeys who self-administered ethanol for more than 1 year. The muscarinic AChR antagonist scopolamine was used to disrupt performance of a serial stimulus discrimination and reversal (SDR) task designed to probe cognitive flexibility, defined as the ability to modify a previously learned behavior in response to a change in reinforcement contingencies. The ability of xanomeline and varenicline to remediate the disruptive effects of scopolamine was compared between socially dominant and subordinate monkeys, with lighter and heavier drinking histories, respectively. We hypothesized that subordinate monkeys would be more sensitive to all three drugs. Scopolamine dose-dependently impaired performance on the serial SDR task in all monkeys at doses lower than those that produced nonspecific impairments (e.g., sedation); its potency did not differ between dominant and subordinate monkeys. However, both AChR agonists were effective in remediating the scopolamine-induced deficit in subordinate monkeys but not in dominant monkeys. These findings suggest xanomeline and varenicline may be effective for enhancing cognitive flexibility in individuals with a history of heavy drinking. SIGNIFICANCE STATEMENT: Procognitive effects of two acetylcholine (ACh) receptor agonists were assessed in group-housed monkeys who had several years' experience drinking ethanol. The muscarinic ACh receptor agonist xanomeline and the nicotinic ACh receptor agonist varenicline reversed a cognitive deficit induced by the muscarinic ACh receptor antagonist scopolamine. However, this effect was observed only in lower-ranking (subordinate) monkeys and not higher-ranking (dominant monkeys). Results suggest that ACh agonists may effectively remediate alcohol-induced cognitive deficits in a subpopulation of those with alcohol use disorder.
Assuntos
Etanol , Macaca fascicularis , Escopolamina , Animais , Masculino , Etanol/farmacologia , Escopolamina/farmacologia , Cognição/efeitos dos fármacos , Consumo de Bebidas Alcoólicas/tratamento farmacológico , Consumo de Bebidas Alcoólicas/psicologia , Vareniclina/farmacologia , Agonistas Colinérgicos/farmacologia , Nootrópicos/farmacologiaRESUMO
Smoking is the leading cause of preventable death worldwide, with <7 % of smoking cessation attempts being met with success. Nicotine, the main addictive agent in cigarettes, enhances the reinforcing value of other environmental rewards. Under some circumstances, this reward enhancement maintains nicotine consumption. Varenicline (i.e., cessation aid Chantix™) also has reward-enhancement effects via nicotinic acetylcholine receptor agonism (nAChRs) - albeit less robust than nicotine. Cotinine is the major metabolite of nicotine. Recent studies suggest that cotinine is a positive allosteric modulator (PAM) and/or a weak agonist at nAChRs. Thus, cotinine may enhance the behavioral effects of nAChR compounds such as varenicline and/or exert some behavioral effects alone. We used 20 (10M, 10F) Sprague-Dawley rats to assess reward-enhancement within-subjects by examining responding maintained by a reinforcing visual stimulus on a Variable Ratio 2 schedule of reinforcement. To assess the reward-enhancing effects of cotinine, rats received one injection of cotinine (saline, 0.1, 0.3, 1.0, 3.0, 6.0 mg/kg) before each 1 h session. To assess cotinine and varenicline interactions, rats received an injection of cotinine (saline, 0.1, 1.0, or 6.0 mg/kg) and of varenicline (saline, 0.1, 0.3, 1.0, or 3.0 mg/kg) before the session. While we replicated prior work identifying reward-enhancement by 0.1, 0.3, and 1.0 mg/kg varenicline, cotinine alone did not produce reward-enhancement nor augment the reward-enhancing effects of varenicline. Future studies may consider examining the reward-enhancing effects of cotinine with other reinforcers or co-administered with other smoking cessation aids such as bupropion.
Assuntos
Nicotina , Receptores Nicotínicos , Humanos , Ratos , Animais , Vareniclina/farmacologia , Nicotina/farmacologia , Cotinina/farmacologia , Ratos Sprague-Dawley , Agonistas Nicotínicos/farmacologia , Receptores Nicotínicos/metabolismo , Benzazepinas/farmacologia , Quinoxalinas/farmacologiaRESUMO
RESUMO Objetivo O objetivo deste estudo foi investigar os efeitos agudos e crônicos da vareniclina no tecido pulmonar em um estudo experimental. Métodos Um total de 34 ratos foi alocado aleatoriamente em grupos de estudo (vareniclina) e controle. Assim, os ratos foram divididos em dois grupos: (i) grupo controle e (ii) grupo vareniclina. A seguir, os ratos de cada grupo foram, por sua vez, subdivididos igualmente em agudos (C1; V1) e crônicos (C2; V2), e todos os ratos dos grupos agudos e crônicos foram sacrificados sob anestesia: no 45.º dia, para o grupo agudo [C1 (n=5) e V1 (n=12)], e no 90.º dia, para o grupo crônico [C2 (n=5) e V2 (n=12)], respectivamente. Em seguida, foram realizadas análises bioquímicas e histopatológicas. Resultados Trinta e quatro ratos completaram o estudo. Destes ratos, 24 estavam no grupo vareniclina e 10 no grupo controle. Na exposição crônica à vareniclina, os níveis de oxidante composto por malondialdeído (MDA) e mieloperoxidase (MPO) aumentaram, e os níveis de superóxido dismutase (SOD), catalase (CAT), glutationa (GSH) e glutationa peroxidase (GPx), nomeados como antioxidantes, diminuiram significativamente quando comparados com o grupo controle. Os níveis de MDA e MPO também foram significativamente mais elevados e os níveis de SOD, CAT, GPx e GSH foram significativamente mais baixos no grupo vareniclina crônico, quando comparado ao grupo vareniclina agudo. Estes achados também foram confirmados por observações histopatológicas. Conclusões Este é o primeiro estudo que avaliou os efeitos pulmonares da vareniclina experimentalmente em um modelo animal. Observamos que o tratamento crônico da vareniclina causa inflamação e lesão pulmonar.
ABSTRACT Objective This study aimed to investigate acute and chronic effects of varenicline on lung tissue in an experimental study. Methods A total of 34 rats were randomly allocated into study (varenicline) and control groups. The rats were divided into two groups (i) control group, (ii) varenicline group. Then, the rats in the each group were sub-divided equally in turn as acute (C1; V1) and chronic (C2; V2) ; all rats of acute and chronic groups were sacrificed under the anesthesia on the 45th day for acute group [C1 (n=5) and V1 (n=12)] and the 90th day for chronic group [C2 (n=5) and V2 (n=12)], respectively. Thus, biochemical and histopathological analysis were carried out. Results Thirty four rats completed the study, 24 were in varenicline group and 10 were in control group. In chronic exposure to varenicline, oxidant levels comprising of malondialdehyde (MDA), and myeloperoxidase (MPO) increased and superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) and glutathione peroxidase (GPx) levels, named as antioxidants, decreased significantly when compared to the control group. MDA and MPO levels were also significantly higher and SOD, CAT, GPx, GSH levels were also significantly lower in chronic varenicline group when compared to acute varenicline group. These findings were also supported by histopathological observations. Conclusion This is the first study, which evaluated pulmonary effects of varenicline experimentally on an animal model. It was observed that chronic varenicline treatments cause inflammation and lung cell injury.
Assuntos
Animais , Ratos , Superóxido Dismutase/sangue , Vareniclina/farmacologia , Pulmão/efeitos dos fármacos , Catalase/sangue , Estresse Oxidativo , Glutationa , Glutationa Peroxidase , Malondialdeído/sangueRESUMO
En general, los diferentes tratados de farmacología se organizan en torno a una clasificación anatómica-terapéutica-química. Los tratados de «química farmacéutica» suelen organizarse, además, poniendo énfasis en la naturaleza química de los fármacos, así como en los procesos bioquímicos involucrados en su acción. En otras ocasiones, cuando se contempla la fitoterapia desde un punto de vista botánico, como hace la «botánica medicinal», la exposición se realiza mediante un viaje a través de los diferentes taxones que contienen especies con relevancia terapéutica. En cambio, en este artículo de revisión se va a hablar de un grupo de fármacos que, desde los enfoques expositivos anteriores, no tienen mucho que ver pero que, sin embargo, poseen mecanismos farmacodinámicos muy similares, a pesar de que actúen sobre diferentes receptores. Se trata de los agonistas (y antagonistas) parciales. Lógicamente no se revisarán todos en este artículo, sino aquellos que al autor le han parecido más curiosos e interesantes para ilustrar su relación mutua en cuanto al funcionamiento farmacodinámico: vareniclina, buprenorfina, diazepinonas, aripiprazol, memantina. Este es el objetivo de este artículo: la revisión de un grupo de fármacos desde un punto de vista novedoso, como es su mecanismo de acción farmacodinámico común. Entre las conclusiones, está la indicación de este tipo de fármacos cuando se va a intervenir en sistemas bioquímicos y fisiológicos tan complicados que las funciones a tratar no deben ni inhibirse ni potenciarse desmedidamente, sino simplemente modularse. Este es el caso de muchas dolencias que afectan al sistema nervioso (AU)
In general the different treatises of pharmacology are organised around an anatomical-therapeutic-chemical classification. Treatises about «medicinal chemistry» are organised, not only around this, but also emphasise the chemical nature of the drugs, as well as the biochemical processes involved in their action. Furthermore, when herbal medicine is contemplated from a botanical point of view, as does the «medical botany», exposure is performed by a journey through the different taxa containing species with therapeutic relevance. Nevertheless, in this review article a group of drugs is discussed that, from the previous points of view, do not have anything to do with each other. However, they have very similar pharmacodynamic mechanisms, despite acting on different receptors. These are partial agonists (and antagonists). Obviously not all of these will be reviewed in this article, but those more interesting to illustrate their relationship in terms of pharmacodynamic performance: varenicline, buprenorphine, diazepinones, aripiprazole, memantine. This is the purpose of this article: A review of a group of drugs from a novel point of view, such as their common pharmacodynamic mechanism of action. Among the conclusions, is the indication of these drugs to intervene in such complicated biochemical and physiological systems that functions to be treated should neither be inhibited nor enhanced, but simply modulated. This is the case of many diseases that affect the nervous system (AU)