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PloS One 2016Excess sugar consumption has been shown to contribute directly to weight gain, thus contributing to the growing worldwide obesity epidemic. Interestingly, increased...
Excess sugar consumption has been shown to contribute directly to weight gain, thus contributing to the growing worldwide obesity epidemic. Interestingly, increased sugar consumption has been shown to repeatedly elevate dopamine levels in the nucleus accumbens (NAc), in the mesolimbic reward pathway of the brain similar to many drugs of abuse. We report that varenicline, an FDA-approved nicotinic acetylcholine receptor (nAChR) partial agonist that modulates dopamine in the mesolimbic reward pathway of the brain, significantly reduces sucrose consumption, especially in a long-term consumption paradigm. Similar results were observed with other nAChR drugs, namely mecamylamine and cytisine. Furthermore, we show that long-term sucrose consumption increases α4β2 * and decreases α6β2* nAChRs in the nucleus accumbens, a key brain region associated with reward. Taken together, our results suggest that nAChR drugs such as varenicline may represent a novel treatment strategy for reducing sugar consumption.
Topics: Alkaloids; Animals; Azocines; Drug Evaluation, Preclinical; Food Preferences; Male; Mecamylamine; Nicotinic Agonists; Nicotinic Antagonists; Nucleus Accumbens; Quinolizines; Rats, Wistar; Receptors, Nicotinic; Sucrose; Varenicline
PubMed: 27028298
DOI: 10.1371/journal.pone.0150270 -
Journal of Psychopharmacology (Oxford,... Mar 2024Addiction to tobacco and nicotine products has adverse health effects and afflicts more than a billion people worldwide. Therefore, there is an urgent need for new...
BACKGROUND
Addiction to tobacco and nicotine products has adverse health effects and afflicts more than a billion people worldwide. Therefore, there is an urgent need for new treatments to reduce tobacco and nicotine use. Glucocorticoid receptor blockade shows promise as a novel treatment for drug abuse and stress-related disorders.
AIM
These studies aim to investigate whether glucocorticoid receptor blockade with mifepristone diminishes the reinforcing properties of nicotine in rats with intermittent or daily long access to nicotine.
METHODS
The rats self-administered 0.06 mg/kg/inf of nicotine for 6 h per day, with either intermittent or daily access for 4 weeks before treatment with mifepristone. Daily nicotine self-administration models regular smoking, while intermittent nicotine self-administration models occasional smoking. To determine whether the rats were dependent, they were treated with the nicotinic acetylcholine receptor antagonist mecamylamine, and somatic signs were recorded.
RESULTS
The rats with intermittent access to nicotine had a higher level of nicotine intake per session than those with daily access but only the rats with daily access to nicotine showed signs of physical dependence. Furthermore, mecamylamine increased nicotine intake during the first hour of access in rats with daily access but not in those with intermittent access. Mifepristone decreased total nicotine intake in rats with intermittent and daily access to nicotine. Moreover, mifepristone decreased the distance traveled and rearing in the open field test and operant responding for food pellets.
CONCLUSION
These findings indicate that mifepristone decreases nicotine intake but this effect may be partially attributed to the sedative effects of mifepristone.
Topics: Humans; Rats; Animals; Nicotine; Mecamylamine; Mifepristone; Smoking; Receptors, Glucocorticoid; Tobacco Use Disorder; Substance Withdrawal Syndrome; Rats, Wistar; Self Administration; Dose-Response Relationship, Drug
PubMed: 38332661
DOI: 10.1177/02698811241230255 -
Neuropharmacology Nov 2019The medial habenula-interpeduncular nucleus (MHb-IPN) pathway modulates negative affective states produced by nicotine withdrawal. Sex differences in the contribution of...
The medial habenula-interpeduncular nucleus (MHb-IPN) pathway modulates negative affective states produced by nicotine withdrawal. Sex differences in the contribution of acetylcholine (ACh) systems in this pathway have not been explored. Thus, this study assessed ACh levels and gene expression of α- and β-containing nicotinic acetylcholine receptor (nAChR) subunits in the IPN of female and male rats following nicotine treatment and withdrawal. Rats were prepared with a pump that delivered nicotine for 14 days, and naïve controls received a sham surgery. In Study 1, rats were prepared with a probe in the IPN, and ACh levels were measured following saline and then mecamylamine administration. In Study 2, separate groups of naïve control or nicotine-treated rats received saline or mecamylamine and physical signs and anxiety-like behavior were assessed using elevated plus maze (EPM) procedures. The IPN was then dissected and mRNA levels were assessed using RT-qPCR methods. Nicotine treatment increased ACh levels to a larger extent in females than males. Nicotine withdrawal produced a similar increase in physical signs; however, females displayed greater anxiety-like behavior than males. In females, gene expression of α5 increased following nicotine treatment and withdrawal. In males, α7 increased following nicotine treatment and α2 and α3 increased during nicotine withdrawal. Both females and males displayed an increase in β3 and β4 during nicotine withdrawal. In females, anxiety-like behavior was correlated with α4, α5, and β2 gene expression in the IPN. These results suggest that sex differences in withdrawal are modulated via cholinergic systems in the IPN.
Topics: Animals; Anxiety; Behavior, Animal; Female; Gene Expression; Interpeduncular Nucleus; Male; Mecamylamine; Nicotine; Nicotinic Agonists; Nicotinic Antagonists; RNA, Messenger; Rats; Receptors, Nicotinic; Sex Factors; Substance Withdrawal Syndrome; alpha7 Nicotinic Acetylcholine Receptor
PubMed: 31325431
DOI: 10.1016/j.neuropharm.2019.107714 -
Behavioural Pharmacology Aug 2014The extent to which chronic nicotine treatment can alter the effects of the nicotinic acetylcholine receptor antagonist mecamylamine, and whether those effects can be...
The extent to which chronic nicotine treatment can alter the effects of the nicotinic acetylcholine receptor antagonist mecamylamine, and whether those effects can be attenuated by nicotine have not been clearly established in the literature. Here, the discriminative stimulus effects of mecamylamine were compared between one group of rhesus monkeys receiving a continuous infusion of nicotine base (5.6 mg/kg/day subcutaneously) and another group of monkeys not receiving nicotine treatment. Both groups responded under a fixed ratio 5 schedule of stimulus-shock termination. Stimulus control was obtained at doses of 1.78 mg/kg mecamylamine in monkeys receiving continuous nicotine and 5.6 mg/kg mecamylamine in monkeys not receiving continuous nicotine treatment. Nicotine did not attenuate the discriminative stimulus effects of mecamylamine in either group. Discontinuation of continuous nicotine produced responding on the mecamylamine lever within 24 h in some but not all monkeys. This may indicate a qualitative difference in the discriminative stimulus effects of mecamylamine between groups, perhaps reflecting antagonism of nicotine and nicotine withdrawal in monkeys receiving continuous nicotine. The failure of nicotine to reverse the effects of mecamylamine is consistent with a noncompetitive interaction at nicotinic acetylcholine receptors and indicates that mecamylamine-induced withdrawal cannot be readily modified by nicotine.
Topics: Animals; Discrimination Learning; Female; Macaca mulatta; Male; Mecamylamine; Neuropsychological Tests; Nicotine; Nicotinic Agonists; Nicotinic Antagonists; Receptors, Nicotinic; Substance Withdrawal Syndrome
PubMed: 24978703
DOI: 10.1097/FBP.0000000000000054 -
Pharmacology 2009Alcohol and nicotine (in the form of tobacco) are 2 commonly used recreational drugs and studies show a high correlation between tobacco use and alcohol consumption. In...
Alcohol and nicotine (in the form of tobacco) are 2 commonly used recreational drugs and studies show a high correlation between tobacco use and alcohol consumption. In the present study, using C57BL/6J mice, we investigated the ability of mecamylamine (a nicotinic antagonist) to reduce alcohol consumption and alcohol preference with free 24-hour access using a 2-bottle choice test drinking procedure. Male C57BL/6J mice were individually housed and acclimatized to 10% alcohol. Immediately following the last day of alcohol acclimatization, the mice (n = 5/group) received subcutaneous injections of mecamylamine (0.5, 1 and 2 mg/kg) or saline consisting of either intermittent (3 injections given every other day) or daily (injections on all 5 days) exposures. Fluid consumption (alcohol and water) was recorded daily. The results showed that mecamylamine significantly reduced alcohol consumption and alcohol preference in both phases of intermittent and daily drug exposures, while the total fluid consumption was unchanged. These results provide further support that mecamylamine is effective in reducing alcohol consumption and preference, and nicotinic-receptor-based drugs could further be explored as potential treatments for alcoholism.
Topics: Alcohol Drinking; Animals; Choice Behavior; Disease Models, Animal; Drinking; Drug Evaluation, Preclinical; Male; Mecamylamine; Mice; Mice, Inbred C57BL; Nicotinic Antagonists
PubMed: 19468256
DOI: 10.1159/000219488 -
Behavioural Brain Research Jan 2022The habenula is an epithalamic structure through which descending connections go from the telencephalon to the brainstem, putting it in a key location to provide...
The habenula is an epithalamic structure through which descending connections go from the telencephalon to the brainstem, putting it in a key location to provide feedback control over the ascending projections from the brainstem to the telencephalon. The medial habenula has a high concentration of nicotinic receptors. We assessed the role of medial habenular nicotinic receptors for nicotine self-administration (SA) in female young adult Sprague-Dawley rats. The rats had bilateral chronic infusion cannulae placed into the medial habenula nucleus. Each cannula was connected to a slow delivery osmotic minipump to chronically infuse mecamylamine (100 µg/side/day) or vehicle for four consecutive weeks. The rats were tested for nicotine SA for the first two weeks of mecamylamine infusion. Then, they had one week of enforced abstinence, during which they had no access to the nicotine SA. Finally, they had one week of resumed nicotine SA access. There was a significantly differential mecamylamine effects in animals with lower and higher pretreatment baseline nicotine SA. Rats with lower baseline nicotine SA levels showed a nearly significant mecamylamine-induced reduction in SA while those with higher baseline levels of SA showed a significant mecamylamine-induced increase in nicotine SA. This study determined that medial habenular nicotinic receptors are important for nicotine reinforcement. Baseline level of performance makes a crucial difference for the involvement of habenular mechanisms in nicotine reinforcement with nicotinic activation being important for maintaining nicotine self-administration for those with lower levels of baseline self-administration and the opposite effect with subjects with higher levels of baseline self-administration.
Topics: Animals; Female; Habenula; Infusions, Intraventricular; Mecamylamine; Nicotine; Rats; Rats, Sprague-Dawley; Receptors, Nicotinic; Reinforcement, Psychology; Self Administration
PubMed: 34499942
DOI: 10.1016/j.bbr.2021.113574 -
The International Journal of... Apr 2006Functional abnormalities in muscarinic and nicotinic receptors are associated with a number of disorders including Alzheimer's disease and schizophrenia. While the... (Comparative Study)
Comparative Study Randomized Controlled Trial
Functional abnormalities in muscarinic and nicotinic receptors are associated with a number of disorders including Alzheimer's disease and schizophrenia. While the contribution of muscarinic receptors in modulating cognition is well established in humans, the effects of nicotinic receptors and the interactions and possible synergistic effects between muscarinic and nicotinic receptors have not been well characterized in humans. The current study examined the effects of selective and simultaneous muscarinic and nicotinic receptor antagonism on a range of cognitive processes. The study was a double-blind, placebo-controlled, repeated measures design in which 12 healthy, young volunteers completed cognitive testing under four acute treatment conditions: placebo (P); mecamylamine (15 mg) (M); scopolamine (0.4 mg i.m.) (S); mecamylamine (15 mg)/scopolamine (0.4 mg i.m.) (MS). Muscarinic receptor antagonism with scopolamine resulted in deficits in working memory, declarative memory, sustained visual attention and psychomotor speed. Nicotinic antagonism with mecamylamine had no effect on any of the cognitive processes examined. Simultaneous antagonism of both muscarinic and nicotinic receptors with mecamylamine and scopolamine impaired all cognitive processes impaired by scopolamine and produced greater deficits than either muscarinic or nicotinic blockade alone, particularly on working memory, visual attention and psychomotor speed. These findings suggest that muscarinic and nicotinic receptors may interact functionally to have synergistic effects particularly on working memory and attention and suggests that therapeutic strategies targeting both receptor systems may be useful in improving selective cognitive processes in a number of disorders.
Topics: Adult; Analysis of Variance; Attention; Double-Blind Method; Drug Interactions; Female; Flicker Fusion; Humans; Male; Mecamylamine; Memory, Short-Term; Muscarinic Antagonists; Neuropsychological Tests; Nicotinic Antagonists; Pain Measurement; Psychomotor Performance; Reaction Time; Receptors, Muscarinic; Receptors, Nicotinic; Recognition, Psychology; Scopolamine; Time Factors
PubMed: 15877932
DOI: 10.1017/S1461145705005407 -
The Journal of Investigative Dermatology Nov 2006The aim of this study was to analyze the influence of cholinergic and anticholinergic drugs on epidermal physiology using organotypic cocultures (OTCs). Blocking of all...
The aim of this study was to analyze the influence of cholinergic and anticholinergic drugs on epidermal physiology using organotypic cocultures (OTCs). Blocking of all acetylcholine receptors (AChRs) by combined treatment with mecamylamine and atropine or treatment with strychnine (blocking alpha9nAChR) for 7-14 days resulted in a complete inhibition of epidermal differentiation and proliferation. Blockage of nicotinic (n)AChR with mecamylamine led to a less pronounced delay in epidermal differentiation and proliferation than blockage of muscarinic (m)AChR with atropine, evidenced by reduced epithelial thickness and expression of terminal differentiation markers like cytokeratin 2e or filaggrin. In OTCs treated with atropine, mecamylamine, or strychnine, we could demonstrate intracellular lipid accumulation in the lower epidermal layers, indicating a severely disturbed epidermal barrier. In addition, we observed prominent acantholysis in the basal and lower suprabasal layers in mecamylamine-, atropine-, and strychnine-treated cultures, accompanied by a decreased expression of cell adhesion proteins. This globally reduced cell adhesion led to cell death via intrinsic activation of apoptosis. In contrast, stimulation of nAChR and mAChR with cholinergic drugs resulted in a significantly thickened epithelium, accompanied by an improved epithelial maturation. In summary, we show that epidermal AChR are crucially involved in the regulation of epidermal homeostasis.
Topics: Acetylcholine; Apoptosis; Atropine; Biomarkers; Cell Adhesion; Cell Differentiation; Cell Proliferation; Cholinergic Agonists; Cholinergic Antagonists; Cytoskeletal Proteins; Desmosomal Cadherins; Epidermal Cells; Epidermis; Filaggrin Proteins; Homeostasis; Humans; Intermediate Filament Proteins; Keratin-2; Lipid Metabolism; Lipids; Mecamylamine; Organ Culture Techniques; Receptors, Muscarinic; Receptors, Nicotinic; Strychnine; Tight Junctions
PubMed: 16810300
DOI: 10.1038/sj.jid.5700443 -
The Journal of Pharmacology and... Jun 2023The rapid increase in e-cigarette use highlights the importance of developing relevant, predictive animal models exploring their potential health implications. The goal...
The rapid increase in e-cigarette use highlights the importance of developing relevant, predictive animal models exploring their potential health implications. The goal of the present study was to examine the abuse-related effects of brief, repeated e-cigarette aerosol exposures in rodents modeling human e-cigarette user behavior. We evaluated the discriminative stimulus effects of brief, repeated puffs of inhaled nicotine in rats that had been trained to discriminate injected nicotine from saline. Locomotor activity measurement following exposure to injected and aerosolized nicotine was also assessed as an additional behavioral outcome. We hypothesized that the stimulus effects of nicotine aerosol were central nervous system (CNS)-mediated and comparable to that produced by an injected nicotine training stimulus. We further hypothesized that number of aerosol puffs and the e-liquid nicotine concentration which was aerosolized would impact the substitution of nicotine aerosol for injected nicotine. Both nicotine injections and exposures to nicotine aerosol produced a dose-dependent effect on locomotor activity. Nicotine aerosol under our puffing conditions produced e-liquid nicotine concentration-dependent and puff-number-dependent complete substitution for the injected nicotine training condition. The nicotinic antagonist, mecamylamine, completely blocked nicotine-appropriate responding produce by the training dose of 0.3 mg/kg injected nicotine as well as that resulting from exposure to aerosol puffs generated by e-liquid containing 3 mg/ml nicotine, demonstrating that the stimulus of inhaled nicotine was most likely CNS-mediated and not due to olfactory stimulus properties. Overall, the results support the hypothesis that an aerosol exposure drug discrimination model in rodents has applicability to studying the abuse-related effects of e-cigarettes. SIGNIFICANCE STATEMENT: Animal models of nicotine aerosol exposure using testing conditions resembling human e-cigarette use are lacking. In this study, we test a novel preclinical model of nicotine vaping in rodents which allows for the exploration of the abuse-related effects of e-cigarettes. This model has the potential to contribute both to our understanding of the abuse-related pharmacological effects of e-cigarettes as well as aid in the development of rationale, evidence-based e-cigarette regulatory policies.
Topics: Humans; Rats; Animals; Nicotine; Electronic Nicotine Delivery Systems; Rodentia; Aerosols; Mecamylamine
PubMed: 36918277
DOI: 10.1124/jpet.122.001520 -
Neuroscience Mar 2014Activation of the dopaminergic mesolimbic reward circuit that originates in the ventral tegmental area (VTA) is postulated to preferentially suppress emotional responses...
Activation of the dopaminergic mesolimbic reward circuit that originates in the ventral tegmental area (VTA) is postulated to preferentially suppress emotional responses to noxious stimuli, and presumably contributes to the addictive liability of strong analgesics. VTA dopamine neurons are activated via cholinergic afferents and microinjection of carbachol (cholinergic agonist) into VTA is rewarding. Here, we evaluated regional differences within VTA in the capacity of carbachol to suppress rats' affective response to pain (vocalization afterdischarges, VADs) and to support conditioned place preference (CPP) learning. As carbachol is a non-specific agonist, muscarinic and nicotinic receptor involvement was assessed by administering atropine (muscarinic antagonist) and mecamylamine (nicotinic antagonist) into VTA prior to carbachol treatment. Unilateral injections of carbachol (4μg) into anterior VTA (aVTA) and posterior VTA (pVTA) suppressed VADs and supported CPP; whereas, injections into midVTA failed to effect either VADs or CPP. These findings corroborate the hypothesis that the neural substrates underlying affective analgesia and reward overlap. However, the extent of the overlap was only partial. Whereas both nicotinic and muscarinic receptors contributed to carbachol-induced affective analgesia in aVTA, only muscarinic receptors mediated the analgesic action of carbachol in pVTA. The rewarding effects of carbachol are mediated by the activation of both nicotinic and muscarinic receptors in both aVTA and pVTA. The results indicate that analgesia and reward are mediated by separate cholinergic mechanisms within pVTA. Nicotinic receptor antagonism within pVTA failed to attenuate carbachol-induced analgesia, but prevented carbachol-induced reward. As addictive liability of analgesics stem from their rewarding properties, the present findings suggest that these processes can be neuropharmacologically separated within pVTA.
Topics: Analgesia; Animals; Atropine; Carbachol; Cholinergic Agonists; Male; Mecamylamine; Muscarinic Antagonists; Nicotinic Antagonists; Pain Threshold; Rats; Rats, Long-Evans; Reward; Ventral Tegmental Area
PubMed: 24434773
DOI: 10.1016/j.neuroscience.2014.01.009