Complex relationships of nicotinic receptor actions and cognitive functions

Cigarette smoking is linked to an increased risk of delirium following arthroplasty in patients suffering from osteoarthritic pain

AIMS

Postoperative delirium (POD) is a common postoperative complication, and the potential relationship between cigarette smoking and POD is still unclear. The current study evaluated the relationship between preoperative smoking status in patients suffering from osteoarthritic pain and POD after total knee arthroplasty (TKA).

METHODS

A total of 254 patients who had undergone unilateral TKA were enrolled between November 2021 and December 2022, with no gender limitation. Preoperatively, patients' visual analog scale (VAS) scores at rest and during movement, hospital anxiety and depression (HAD) scores, pain catastrophizing scale (PCS) scores and smoking status were collected. The primary outcome was the incidence of POD, which was evaluated by the confusion assessment method (CAM).

RESULTS

A total of 188 patients had complete datasets for final analysis. POD was diagnosed in 41 of 188 patients (21.8%) who had complete data for analysis. The incidence of smoking was significantly higher in Group POD than in Group Non-POD (22 of 41 patients [54%] vs. 47 of 147 patients [32%], p < 0.05). The postoperative hospital stays were also longer than those of Group Non-POD (p < 0.001). Multiple logistic regression analysis showed that preoperative smoking (OR: 4.018, 95% CI: 1.158-13.947, p = 0.028) was a risk factor for the occurrence of POD in patients with TKA. The length of hospital stay was correlated with the occurrence of POD.

CONCLUSIONS

Our findings suggest that patients who smoked preoperatively were at increased risk of developing POD following TKA.

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.

The Effect of High Nicotine Dose on Maximum Anaerobic Performance and Perceived Pain in Healthy Non-Smoking Athletes: Crossover Pilot Study

Background: In recent years, there has been intensive discussion about the positive effect of nicotine usage on enhancing sports performance. It is frequently applied through a non-burned tobacco form before physical activity. Nicotine is under the World Anti-Doping Agency (WADA) 2021 monitoring program. Therefore, study results that reveal either positive or negative effects are expected. This is the pilot study that reports the effect of 8 mg dose of nicotine on performance and perceived pain. Material and Methods: This research aimed to explore the oral intake effect of a high-nicotine dose (8 mg) on the maximum anaerobic performance and other selected physical performance parameters in healthy, well-trained adult athletes (n = 15, age 30.7 ± 3.6, BMI 25.3 ± 1.7). The cross-sectional study protocol included the oral administration of either sublingual nicotine or placebo tablets before the anaerobic load assessed by a standardized 30 s Wingate test of the lower limbs. Afterward, the Borg subjective perception of pain (CR 10) and Borg rating of perceived exertion (RPE) were evaluated. Wilcoxon signed-rank test was used for the analysis of data with a 0.05 level of significance. Results: The results revealed that oral administration of an 8 mg nicotine dose does not significantly improve any of the physical performance parameters monitored. We only reported the statistically significant positive effect in RPE (p = 0.03). Conclusion: Lower perception of pain intensity that we reported after nicotine application might be an important factor that affects performance. However, we did not report any improvement in physical performance parameters.

Differential roles of nucleus reuniens and perirhinal cortex in Pavlovian trace fear conditioning in rats

The nucleus reuniens (RE) and the perirhinal cortex (PRC) are two major relay stations that interconnect the hippocampus (HPC) and the medial prefrontal cortex (mPFC). Previous studies have shown that both the RE and the PRC are involved in the acquisition of trace fear conditioning. However, the respective contribution of the two regions is unclear. In this study, we used pharmacological approach to compare their roles. Our data suggested that inactivation of the RE or the PRC during conditioning partially impaired, whereas inactivation of both areas totally abolished, the encoding of trace fear. We next examined whether the impaired encoding of trace fear under RE inactivation can be rescued with enhanced cholinergic tone in the PRC, and vice versa. Against our hypothesis, regardless of whether the RE was on-line or not, animals failed to encode trace fear when further engaging cholinergic activities in the PRC. Conversely, depending on PRC activation level during conditioning, further recruiting cholinergic activities in the RE led to a down-shift of fear response during retrieval. Our results revealed that the RE and the PRC were necessary for the encoding of trace fear. Moreover, there was differential importance of cholinergic modulation during the process.

Impact of Nicotine on Cognition in Patients With Schizophrenia: A Narrative Review

Nicotine is the psychoactive component given tobacco has several main components and acts as an agonist for nicotinic acetylcholine receptors (nAChRs) in the nervous system. Although the ligand-gated cation channels known as nAChRs are found throughout the nervous system and body, this review focuses on neuronal nAChRs. Individuals with psychiatric diseases such as schizophrenia, comorbid substance use disorders, attention-deficit hyperactivity disorder, major depression, and bipolar disorder have increased rates of smoking. These psychiatric disorders are associated with various cognitive deficits, including working memory, deficits in attention, and response inhibition functions. The cognitive-enhancing effects of nicotine may be particularly relevant predictors of smoking initiation and continuation in this comorbid population. Individuals with schizophrenia make up a significant proportion of smokers. Literature suggests that patients smoke to alleviate cognitive deficiencies due to the stimulating effects of nicotine. This narrative review examines the role of nicotine on cognition in schizophrenia.

Brain Adaptation to Acute Stress: Effect of Time, Social Buffering, and Nicotinic Cholinergic System

Both social behavior and stress responses rely on the activity of the prefrontal cortex (PFC) and basolateral nucleus of the amygdala (BLA) and on cholinergic transmission. We previously showed in adult C57BL/6J (B6) mice that social interaction has a buffering effect on stress-related prefrontal activity, depending on the β2-/- cholinergic nicotinic receptors (nAChRs, β2-/- mice). The latency for this buffer to emerge being short, we question here whether the associated brain plasticity, as reflected by regional c-fos protein quantification and PFC-BLA functional connectivity, is modulated by time. Overall, we show that time normalized the stress-induced PFC hyperactivation in B6 mice and PFC hypo-activation in β2-/- mice, with no effect on BLA. It also triggered a multitude of functional links between PFC subareas, and between PFC and BLA in B6 mice but not β2-/- mice, showing a central role of nAChRs in this plasticity. Coupled with social interaction and time, stress led to novel and drastic diminution of functional connectivity within the PFC in both genotypes. Thus, time, emotional state, and social behavior induced dissociated effects on PFC and BLA activity and important cortico-cortical reorganizations. Both activity and plasticity were under the control of the β2-nAChRs.

Neuroprotective effect of combined use of nicotine and celecoxib by inhibiting neuroinflammation in ischemic rats

INTRODUCTION

The contribution of neuroinflammation in cognitive impairment is increasingly recognized. Non-steroidal anti-inflammatory drugs had been proven that it could improve cognitive impairment in large dose but with more side effect, which limited the application. The main objective of this study was to investigate whether the combined use of nicotine and celecoxib could obtain synergistic neuroprotective effect in ischemic rats.

METHODS

Twenty adult Sprague-Dawley (SD) rats underwent ischemic model surgery by injecting endothelin-1 into the left thalamus, which were classified into four groups with different interventions: nicotine (1.5 mg/kg/d), celecoxib (15 mg/kg/d), nicotine (1.5 mg/kg/d) +celecoxib (15 mg/kg/d), or saline after surgery. The other five SD rats also underwent same surgery by injecting saline instead of endothelin-1, as the control group. Morris water maze (MWM) test was adopted to assess the cognition. Micro PET/CT with 2-[¹⁸F]-A-85380 were performed for α₄β₂-nAChRs detection in vivo. Western blot, real-time PCR and immunohistochemical staining were adopted to detect the expression of α₄β₂-nAChRs and inflammatory factors which included TNF-α, IL-1β, IL-6 in brain tissue. Microglial activation in the brain was monitored by immunofluorescence with IBA1 staining.

RESULTS

The MWM test showed rats given with nicotine or celecoxib alone showed much better memory than rats with saline, no difference was observed between nicotine and celecoxib. The rat memory was recovered most significant when the nicotine and celecoxib were combined (p < 0.05). Micro-PET/CT showed much more tracer uptake in the left thalamus and whole brain in rats given with nicotine, or nicotine + celecoxib (nico + cele group) than saline treated rats, whereas the rats given celecoxib did not. Compared with saline treated rats, we found the proteins of α₄nAChR and β₂nAChR in rats given nicotine or nico + cele increased significantly, and mRNA/proteins of TNF-α, IL-1β and IL-6 decreased at the same time. The α ₄nAChR and β ₂nAChR proteins in rats given celecoxib is the same as saline treated rats, whereas the inflammatory factors decreased obviously compared with saline treated rats. Microglial activation was confirmed in saline treated rats, which was inhibited in rats give nicotine, celecoxib or both.

CONCLUSIONS

The study revealed the combined use of nicotine and celecoxib may improve the cognitive function in ischemic rats, with a better effect than either alone. Both nicotine and celecoxib can inhibit inflammation, but through different mechanisms: nicotine can activate α₄β₂-nAChRs while celecoxib is cyclooxygenase-2 inhibitor. Our findings suggest the combined application of two drugs with different anti-inflammation mechanism could attenuate cognitive impairment more effectively in ischemic rats, which may hold therapeutic potential in the clinical practice.

Relationships and Interactions between Ionotropic Glutamate Receptors and Nicotinic Receptors in the CNS

Although ionotropic glutamate receptors and nicotinic receptors for acetylcholine (ACh) have usually been studied separately, they are often co-localized and functionally inter-dependent. The objective of this review is to survey the evidence for interactions between the two receptor families and the mechanisms underlying them. These include the mutual regulation of subunit expression, which change the NMDA:AMPA response balance, and the existence of multi-functional receptor complexes which make it difficult to distinguish between individual receptor sites, especially in vivo. This is followed by analysis of the functional relationships between the receptors from work on transmitter release, cellular electrophysiology and aspects of behavior where these can contribute to understanding receptor interactions. It is clear that nicotinic receptors (nAChRs) on axonal terminals directly regulate the release of glutamate and other neurotransmitters, α7-nAChRs generally promoting release. Hence, α7-nAChR responses will be prevented not only by a nicotinic antagonist, but also by compounds blocking the indirectly activated glutamate receptors. This accounts for the apparent anticholinergic activity of some glutamate antagonists, including the endogenous antagonist kynurenic acid. The activation of presynaptic nAChRs is by the ambient levels of ACh released from pre-terminal synapses, varicosities and glial cells, acting as a 'volume neurotransmitter' on synaptic and extrasynaptic sites. In addition, ACh and glutamate are released as CNS co-transmitters, including 'cholinergic' synapses onto spinal Renshaw cells. It is concluded that ACh should be viewed primarily as a modulator of glutamatergic neurotransmission by regulating the release of glutamate presynaptically, and the location, subunit composition, subtype balance and sensitivity of glutamate receptors, and not primarily as a classical fast neurotransmitter. These conclusions and caveats should aid clarification of the sites of action of glutamate and nicotinic receptor ligands in the search for new centrally-acting drugs.

Is the Antidepressant Activity of Selective Serotonin Reuptake Inhibitors Mediated by Nicotinic Acetylcholine Receptors?

It is generally assumed that selective serotonin reuptake inhibitors (SSRIs) induce antidepressant activity by inhibiting serotonin (5-HT) reuptake transporters, thus elevating synaptic 5-HT levels and, finally, ameliorates depression symptoms. New evidence indicates that SSRIs may also modulate other neurotransmitter systems by inhibiting neuronal nicotinic acetylcholine receptors (nAChRs), which are recognized as important in mood regulation. There is a clear and strong association between major depression and smoking, where depressed patients smoke twice as much as the normal population. However, SSRIs are not efficient for smoking cessation therapy. In patients with major depressive disorder, there is a lower availability of functional nAChRs, although their amount is not altered, which is possibly caused by higher endogenous ACh levels, which consequently induce nAChR desensitization. Other neurotransmitter systems have also emerged as possible targets for SSRIs. Studies on dorsal raphe nucleus serotoninergic neurons support the concept that SSRI-induced nAChR inhibition decreases the glutamatergic hyperstimulation observed in stress conditions, which compensates the excessive 5-HT overflow in these neurons and, consequently, ameliorates depression symptoms. At the molecular level, SSRIs inhibit different nAChR subtypes by noncompetitive mechanisms, including ion channel blockade and induction of receptor desensitization, whereas α9α10 nAChRs, which are peripherally expressed and not directly involved in depression, are inhibited by competitive mechanisms. According to the functional and structural results, SSRIs bind within the nAChR ion channel at high-affinity sites that are spread out between serine and valine rings. In conclusion, SSRI-induced inhibition of a variety of nAChRs expressed in different neurotransmitter systems widens the complexity by which these antidepressants may act clinically.

Tobacco smoke exposure enhances reward sensitivity in male and female rats

RATIONALE

Systemic administration of the tobacco smoke constituent nicotine stimulates brain reward function in rats. However, it is unknown if the inhalation of tobacco smoke affects brain reward function.

OBJECTIVES

These experiments investigated if exposure to smoke from high-nicotine SPECTRUM research cigarettes increases reward function and affects the rewarding effects of nicotine in adult male and female Wistar rats.

METHODS

Reward function after smoke or nicotine exposure was investigated using the intracranial self-stimulation (ICSS) procedure. A decrease in reward thresholds reflects an increase in reward function. In the first experiment, the rats were exposed to tobacco smoke for 40 min/day for 9 days, and the rewarding effects of nicotine (0.03-0.6 mg/kg) were investigated 3 weeks later. In the second experiment, the dose effects of tobacco smoke exposure (40-min sessions, 1-4 cigarettes burnt simultaneously) on reward function were investigated.

RESULTS

Tobacco smoke exposure did not affect the nicotine-induced decrease in reward thresholds or response latencies in male and female rats. Smoke exposure lowered the brain reward thresholds to a similar degree in males and females and caused a greater decrease in latencies in females. There was a positive relationship between plasma nicotine and cotinine levels and the nicotine content of the SPECTRUM research cigarettes. Similar smoke exposure conditions led to higher plasma nicotine and cotinine levels in female than male rats.

CONCLUSION

These findings indicate that tobacco smoke exposure enhances brain reward function but does not potentiate the rewarding effects of nicotine in male and female rats.

Electronic cigarette use and subjective cognitive complaints in adults

INTRODUCTION

Electronic cigarette use (vaping) has become popular in recent years. The number of Americans with a variety of cognitive deficits has been increasing dramatically. This study aimed to examine the potential association of vaping with subjective cognitive complaints in US adults.

METHODS

A combined 2016 and 2017 Behavioral Risk Factor Surveillance System (BRFSS) national survey dataset yielded 886,603 adults who indicated their smoking and vaping status, as well as whether they had subjective cognitive complaints. With this dataset, the cross-sectional association of electronic cigarette use with subjective cognitive complaints was examined using multivariable weighted logistic regression models.

RESULTS

Both dual users (adjusted Odds Ratio [aOR] = 2.07; 95% Confidence Interval [CI] = 1.66 to 2.60) and current vapers who were either ex-smokers (aOR = 1.94; 95% CI = 1.40 to 2.71) or never smoked (aOR = 1.96; 95% CI = 1.16 to 3.30) showed a significantly higher association with subjective cognitive complaints than never users. Current smokers (aOR = 1.49; 95% CI = 1.32 to 1.69) and ex-smokers (aOR = 1.25; 95% CI = 1.11 to 1.41) had a significantly higher association with subjective cognitive complaints compared to never users. Compared to current smokers, the ex-smokers showed a lower association with subjective cognitive complaints (aOR = 0.84; 95% CI = 0.73 to 0.96). Finally, the association of vaping with subjective cognitive complaints was not statistically significant in individual age group.

CONCLUSION

Similar to smoking, vaping is associated with subjective cognitive complaints in US adults. These results provide preliminary evidence for a cross-sectional association of vaping with potential cognitive health effects in adults.

Menthol Cigarettes, Tobacco Dependence, and Smoking Persistence: The Need to Examine Enhanced Cognitive Functioning as a Neuropsychological Mechanism

INTRODUCTION

Despite the overall decline in the prevalence of cigarette use in the United States, menthol cigarette use among smokers is rising, and evidence shows that it may lead to more detrimental effects on public health than regular cigarette use. One of the mechanisms by which nicotine sustains tobacco use and dependence is due to its cognitive enhancing properties, and basic science literature suggests that menthol may also enhance nicotine's acute effect on cognition.

AIMS AND METHODS

The purpose of this review is to suggest that the cognitive enhancing effects of menthol may be a potentially important neuropsychological mechanism that has yet to be examined. In this narrative review, we provide an overview of basic science studies examining neurobiological and cognitive effects of menthol and menthol cigarette smoking. We also review studies examining menthol essential oils among humans that indicate menthol alone has acute cognitive enhancing properties. Finally, we present factors influencing the rising prevalence of menthol cigarette use among smokers and the importance of this gap in the literature to improve public health and smoking cessation treatment.

CONCLUSIONS

Despite the compelling evidence for menthol's acute cognitive enhancing and reinforcing effects, this mechanism for sustaining tobacco dependence and cigarette use has yet to be examined and validated among humans. On the basis of the basic science evidence for menthol's neurobiological effects on nicotinic receptors and neurotransmitters, perhaps clarifying menthol's effect on cognitive performance can help to elucidate the complicated literature examining menthol and tobacco dependence.

IMPLICATIONS

Menthol cigarette use has continued to be a topic of debate among researchers and policy makers, because of its implications for understanding menthol's contribution to nicotine dependence and smoking persistence, as well as its continued use as a prevalent flavoring in tobacco and nicotine products in the United States and internationally. As international tobacco regulation policies have begun to target menthol cigarettes, research studies need to examine how flavoring additives, specifically menthol, may acutely influence neurobiological and cognitive functioning as a potential mechanism of sustained smoking behavior to develop more effective treatments.

Comparison of Effects of Spatial and Non-Spatial Memory Acquisition on the CaMKII Pathway During Hypothyroidism and Nicotine Treatment

Molecular, cellular, and behavioral studies have shown that hypothyroidism impairs hippocampus-dependent learning and memory in adult rats. In these studies, spatial learning and memory were tested in the radial arm water maze (RAWM), which involved locating a hidden platform. In the present study, we investigated the effects of nicotine and hypothyroidism on the CaMKII pathway during learning and memory processes in both spatial and non-spatial memory forms. We used nicotine as a neuroprotective agent. Hypothyroidism was induced by thyroidectomy in adult rats. Rats were trained on the hidden platform (the RAWM for spatial learning and memory) and compared with age-matched rats that were trained on a clearly visible platform system (2 cm above water with no radial arms for non-spatial learning and memory). Nicotine (1 mg/kg twice/day) was administered subcutaneously for 4 weeks. Immediately after training, the protein levels of memory-related signaling molecules were determined in hippocampal area CA1. Western blot analysis revealed a significant increase in calcineurin levels and decreases in P-CaMKII, PKCγ, and calmodulin protein levels in area CA1 of the hippocampi of hypothyroid rats trained on both the visible and hidden platforms. Nicotine treatment normalizes these levels in hypothyroid rats trained on both the visible and hidden platforms. The results suggest that chronic nicotine treatment prevents hypothyroidism-induced suppression of the CaMKII pathway after spatial and non-spatial learning and memory.

Activation of nicotinic acetylcholine receptors induces potentiation and synchronization within in vitro hippocampal networks

Nicotinic acetylcholine receptors (nAChRs) are known to play a role in cognitive functions of the hippocampus, such as memory consolidation. Given that they conduct Ca²⁺ and are capable of regulating the release of glutamate and γ-aminobutyric acid (GABA) within the hippocampus, thereby shifting the excitatory-inhibitory ratio, we hypothesized that the activation of nAChRs will result in the potentiation of hippocampal networks and alter synchronization. We used nicotine as a tool to investigate the impact of activation of nAChRs on neuronal network dynamics in primary embryonic rat hippocampal cultures prepared from timed-pregnant Sprague-Dawley rats. We perturbed cultured hippocampal networks with increasing concentrations of bath-applied nicotine and performed network extracellular recordings of action potentials using a microelectrode array. We found that nicotine modulated network dynamics in a concentration-dependent manner; it enhanced firing of action potentials as well as facilitated bursting activity. In addition, we used pharmacological agents to determine the contributions of discrete nAChR subtypes to the observed network dynamics. We found that β4-containing nAChRs are necessary for the observed increases in spiking, bursting, and synchrony, while the activation of α7 nAChRs augments nicotine-mediated network potentiation but is not necessary for its manifestation. We also observed that antagonists of N-methyl-D-aspartate receptors (NMDARs) and group I metabotropic glutamate receptors (mGluRs) partially blocked the effects of nicotine. Furthermore, nicotine exposure promoted autophosphorylation of Ca²⁺ /calmodulin-dependent kinase II (CaMKII) and serine 831 phosphorylation of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) subunit GluA1. These results suggest that nicotinic receptors induce potentiation and synchronization of hippocampal networks and glutamatergic synaptic transmission. Findings from this work highlight the impact of cholinergic signaling in generating network-wide potentiation in the form of enhanced spiking and bursting dynamics that coincide with molecular correlates of memory such as increased phosphorylation of CaMKII and GluA1. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/.

Rapid Neuromodulation of Layer 1 Interneurons in Human Neocortex

Inhibitory interneurons govern virtually all computations in neocortical circuits and are in turn controlled by neuromodulation. While a detailed understanding of the distinct marker expression, physiology, and neuromodulator responses of different interneuron types exists for rodents and recent studies have highlighted the role of specific interneurons in converting rapid neuromodulatory signals into altered sensory processing during locomotion, attention, and associative learning, it remains little understood whether similar mechanisms exist in human neocortex. Here, we use whole-cell recordings combined with agonist application, transgenic mouse lines, in situ hybridization, and unbiased clustering to directly determine these features in human layer 1 interneurons (L1-INs). Our results indicate pronounced nicotinic recruitment of all L1-INs, whereas only a small subset co-expresses the ionotropic HTR3 receptor. In addition to human specializations, we observe two comparable physiologically and genetically distinct L1-IN types in both species, together indicating conserved rapid neuromodulation of human neocortical circuits through layer 1.

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Layer 1 interneurons in human and mouse neocortex respond strongly to acetylcholine

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These rapid responses are mediated by α7 and β2-containing nicotinic receptors

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Human layer 1 comprises neurogliaform cells expressing the conserved marker Ndnf

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Apart from conserved features, human L1 interneurons show a number of specializations

Methylpiperidinium Iodides as Novel Antagonists for α7 Nicotinic Acetylcholine Receptors

The α7 nicotinic acetylcholine receptor (nAChR) is expressed in neuronal and non-neuronal cells and is involved in several physiopathological processes, and is thus an important drug target. We have designed and synthesized novel piperidine derivatives as α7 nAChR antagonists. Thus, we describe here a new series of 1-[2-(4-alkoxy-phenoxy-ethyl)]piperidines and 1-[2-(4-alkyloxy-phenoxy-ethyl)]-1-methylpiperidinium iodides (compounds 11a-11c and 12a-12c), and their actions on α7 nAChRs. The pharmacological activity of these compounds was studied in rat CA1 hippocampal interneurons by using the whole-cell voltage-clamp technique. Inhibition of the choline-induced current was less for 11a-11c than for the methylpiperidinium iodides 12a-12c and depended on the length of the aliphatic chain. Those compounds showing strong effects were studied further using molecular docking and molecular dynamics simulations. The strongest and non-voltage dependent antagonism was shown by 12a, which could establish cation–π interactions with the principal (+)-side and van der Waals interactions with the complementary (-)-side in the α7 nAChRs. Furthermore, compound 11a forms hydrogen bonds with residue Q115 of the complementary (-)-side through water molecules without forming cation–π interactions. Our findings have led to the establishment of a new family of antagonists that interact with the agonist binding cavity of the α7 nAChR, which represent a promising new class of compounds for the treatment of pathologies where these receptors need to be negatively modulated, including neuropsychiatric disorders as well as different types of cancer.

Advances in Drug Discovery and Development in Geriatric Psychiatry

PURPOSE OF REVIEW

This article reviews recent advances in drug discovery and development for geriatric psychiatry. Drug discovery for disorders of the central nervous system is a long and challenging process, with a high attrition rate from the preclinical stages through to marketing a compound. Developing drugs for geriatric neuropsychiatric conditions presents additional challenges, due to the complexity of the symptoms, comorbid diagnoses, and the variability of the population. Despite there being limited success over the past two decades, a number of new approaches have identified potential targets for preclinical development and ultimately clinical testing.

RECENT FINDINGS

Recent approaches have tried to address specific mechanisms that relate to the disease progression. These approaches include combining a number of ligands into to multi-target compounds, or targeting specific types of cells such as protein kinases or myeloid cells. In addition, the increased use of induced pluripotent stem cell cultures has enabled new compounds to be tested on disease-specific tissues, increasing the success rate of the lead compounds going through the preclinical stages. New pharmacological agents designed with advanced screening techniques and the shift towards systems pharmacology is changing the landscape of drug discovery in geriatric psychiatry. There is potential for these new agents to produce targeted effects in the framework of disorders that have long been untreatable.

Nicotine self-administration reverses cognitive deficits in a rat model for schizophrenia

High comorbidity between schizophrenia and tobacco addiction has been well established. Explanatory theories include nicotine as a cognitive enhancer ameliorating symptoms of schizophrenia and underlying shared substrates increasing susceptibility to addiction in these individuals. To test these non-mutually exclusive theories, the maternal immune activation (MIA) model was utilized. To this end, pregnant Sprague Dawley rats were subcutaneously injected with a bacterial endotoxin, lipopolysaccharide (0.5 mg/kg), on gestation days 10 and 11. Selective attention and working memory in adult male offspring were subsequently assessed using the latent inhibition and delayed non-matching to sample paradigms both before and after nicotine or saline self-administration. MIA led to deficits in both latent inhibition and delayed non-matching to sample in male offspring. Further, these animals showed a small but significantly increased responding for nicotine during self-administration acquisition, although there was no difference in dose-response effect or in progressive ratio testing. However, nicotine, but not saline self-administration, significantly ameliorated the cognitive deficits induced by MIA. While the male offspring of mothers prenatally exposed to lipopolysaccharide was only slightly more sensitive to the reinforcing effects of nicotine, after self-administration, the MIA-induced cognitive deficits significantly improved. These data lend support for the self-medication hypothesis of schizophrenia.

Cognitive Effects of Nicotine: Recent Progress

BACKGROUND

Cigarette smoking is the main cause of preventable death in developed countries. While the direct positive behavioral reinforcing effect of nicotine has historically been considered the primary mechanism driving the development of TUD, accumulating contemporary research suggests that the cognitive-enhancing effects of nicotine may also significantly contribute to the initiation and maintenance of TUD, especially in individuals with pre-existing cognitive deficits.

METHODS

We provide a selective overview of recent advances in understanding nicotine's effects on cognitive function, a discussion of the role of cognitive function in vulnerability to TUD, followed by an overview of the neurobiological mechanisms underlying the cognitive effects of nicotine.

RESULTS

Preclinical models and human studies have demonstrated that nicotine has cognitiveenhancing effects. Attention, working memory, fine motor skills and episodic memory functions are particularly sensitive to nicotine's effects. Recent studies have demonstrated that the α4, β2, and α7 subunits of the nicotinic acetylcholine receptor (nAChR) participate in the cognitive-enhancing effects of nicotine. Imaging studies have been instrumental in identifying brain regions where nicotine is active, and research on the dynamics of large-scale networks after activation by, or withdrawal from, nicotine hold promise for improved understanding of the complex actions of nicotine on human cognition.

CONCLUSION

Because poor cognitive performance at baseline predicts relapse among smokers who are attempting to quit smoking, studies examining the potential efficacy of cognitive-enhancement as strategy for the treatment of TUD may lead to the development of more efficacious interventions.

Nicotine and networks: Potential for enhancement of mood and cognition in late-life depression

Late-life depression is characterized by both lower mood and poor cognitive performance, symptoms that often do not fully respond to current antidepressant medications. Nicotinic acetylcholine receptor (nAChR) agonists such as nicotine may serve as a novel therapeutic approach for this population. Both preclinical and preliminary clinical studies suggest that nAChR agonists can improve depressive behavior in animal models and improve mood in depressed individuals. Substantial literature also supports that nAChR agonists benefit cognitive performance, particularly in older populations. These potential benefits may be mediated by the effects of nAChR stimulation on neural network function and connectivity. Functional neuroimaging studies detail effects of nAChR agonists on the default mode network, central-executive network, and salience network that may oppose or reverse network changes seen in depression. We propose that, given the existent literature and the clinical presentation of late-life depression, nicotine or other nAChR agonists may have unique therapeutic benefits in this population and that clinical trials examining nicotine effects on mood, cognition, and network dynamics in late-life depression are justified.

Nicotinic Receptor Intervention in Parkinson's Disease: Future Directions

Sufficient preclinical and epidemiological data are available to justify nicotinic intervention in Parkinson's disease (PD). Although use of nicotine patch has been suggested in some neurodegenerative disorders, including PD, the key for success with nicotinic intervention, particularly in PD, appears to rely not only on the dose but also on the mode of nicotine administration. Our aim in this short review is to provide justification for such contention. Thus, following a short introduction of nicotinic receptor pharmacology, the potential of nicotine in alleviating not only the motor symptoms, but also the mood disorders (e.g. depression) and mild cognitive impairments that are commonly co-morbid with PD will be presented. Moreover, since current PD therapy is associated with dyskinesia, the effectiveness of nicotine in ameliorating levodopa (L-Dopa)-induced dyskinesia will also be discussed. It is suggested that pulsatile nicotine administration (e.g. via inhalation or nasal spray) may be the optimal route in nicotinic intervention in PD.

Priming locus coeruleus noradrenergic modulation of medial perforant path-dentate gyrus synaptic plasticity

Priming phenomenon, in which an earlier exposure to a stimulus or condition alters synaptic plasticity in response to a subsequent stimulus or condition, known as a challenge, is an example of metaplasticity. In this review, we make the case that the locus coeruleus noradrenergic system-medial perforant path-dentate gyrus pathway is a neural ensemble amenable to studying priming-challenge effects on synaptic plasticity. Accumulating evidence points to a tyrosine hydroxylase-dependent priming effect achieved by pharmacological (nicotine and antipsychotics) or physiological (septal theta driving) manipulations of the locus coeruleus noradrenergic system that can facilitate noradrenaline-induced synaptic plasticity in the dentate gyrus of the hippocampus. The evidence suggests the hypothesis that behavioural experiences inducing tyrosine hydroxylase expression in the locus coeruleus may be sufficient to prime this form of metaplasticity. We propose exploring this phenomenon of priming and challenge physiologically, to determine whether behavioural experiences are sufficient to prime the locus coeruleus, enabling subsequent pharmacological or behavioural challenge conditions that increase locus coeruleus firing to release sufficient noradrenaline to induce long-lasting potentiation in the dentate gyrus. Such an approach may contribute to unravelling mechanisms underlying this form of metaplasticity and its importance in stress-related mnemonic processes.

Analysis of neuronal nicotinic acetylcholine receptor α4β2 activation at the single-channel level

The neuronal nicotinic acetylcholine receptor α4β2 forms pentameric proteins with two alternate stoichiometries. The high-sensitivity receptor is related to (α4)2(β2)3 stoichiometry while the low-sensitivity receptor to (α4)3(β2)2 stoichiometry. Both subtypes share two binding sites at the α4((+))/β2((-)) interface with high affinity for agonists. (α4)3(β2)2 has an additional binding site at the α4((+))/α4((-)) interface with low affinity for agonists. We investigated activation kinetics of both receptor subtypes by patch-clamp recordings of single-channel activity in the presence of several concentrations of acetylcholine (0.5 to 300μM). We used kinetic software to fit these data with kinetic models. We found that the high-sensitivity subtype correlates with the low-conductance channel (g-70=29pS) and does not activate with high efficacy. On the contrary, the low-sensitivity subtype correlated with a high-conductance channel (g-70=44pS) and exhibited higher activation efficacy. Opening events of individual nAChRs at high agonist concentrations occurred in clusters, which allowed us to determine kinetic constants for the activation of the triliganded receptor. Our kinetic modeling identified an intermediate state, between resting and open conformation of the receptor. Binding of the third molecule increases the efficacy of receptor activation by favoring the transition between resting and intermediate state around 18 times. The low rate for this transition in the diliganded receptor explains the action of acetylcholine as partial agonist when it binds to the high-affinity sites. The presence of the third binding site emerges as a potent modulator of nicotinic receptor α4β2 activation which may display different functions depending on agonist concentration.

Nicotine ameliorates schizophrenia-like cognitive deficits induced by maternal LPS exposure: a study in rats

Maternal exposure to infectious agents is a predisposing factor for schizophrenia with associated cognitive deficits in offspring. A high incidence of smoking in these individuals in adulthood might be, at least in part, due to the cognitive-enhancing effects of nicotine. Here, we have used prenatal exposure to maternal lipopolysaccharide (LPS, bacterial endotoxin) at different time points as a model for cognitive deficits in schizophrenia to determine whether nicotine reverses any associated impairments. Pregnant rats were treated subcutaneously with LPS (0.5 mg/kg) at one of three neurodevelopmental time periods [gestation days (GD) 10-11, 15-16, 18-19]. Cognitive assessment in male offspring commenced in early adulthood [postnatal day (PND) 60] and included: prepulse inhibition (PPI), latent inhibition (LI) and delayed non-matching to sample (DNMTS). Following PND 100, daily nicotine injections (0.6 mg/kg, subcutaneously) were administered, and animals were re-tested in the same tasks (PND 110). Only maternal LPS exposure early during fetal neurodevelopment (GD 10-11) resulted in deficits in all tests compared to animals that had been prenatally exposed to saline at the same gestational time point. Repeated nicotine treatment led to global (PPI) and selective (LI) improvements in performance. Early but not later prenatal LPS exposure induced consistent deficits in cognitive tests with relevance for schizophrenia. Nicotine reversed the LPS-induced deficits in selective attention (LI) and induced a global enhancement of sensorimotor gating (PPI).

Reduction of Aggressive Episodes After Repeated Transdermal Nicotine Administration in a Hospitalized Adolescent with Autism Spectrum Disorder

Aggression remains a major cause of morbidity in patients with autism spectrum disorder (ASD). Current pharmacotherapy for aggression is not always effective and is often associated with morbidity. Nicotinic acetylcholinergic neurotransmission may play a prominent role in ASD pathophysiology based on human and animal studies, and preclinical studies show nicotine administration can reduce aggression-related behaviors. Transdermal nicotine has been used to treat agitation in neuropsychiatric conditions with cholinergic dysfunction. Here we report the use of transdermal nicotine as an adjunctive medication to treat aggression in a hospitalized adolescent with ASD. Nicotine patch was recurrently well tolerated, and reduced the need for emergency medication and restraint. These findings suggest further study of transdermal nicotine for aggression comorbid with ASD is warranted.

Effects of varenicline on alpha4-containing nicotinic acetylcholine receptor expression and cognitive performance in mice

Nicotinic acetylcholine receptor (nAChR) subtypes containing the α4 subunit, particularly α4β2 nAChRs, play an important role in cognitive functioning. The impact of the smoking cessation aid varenicline, a selective partial α4β2 nAChR agonist, on (1) changes of central protein and mRNA expression of this receptor and (2) on memory deficits in a mouse model of cognitive impairment was investigated. Protein and mRNA expression of both the α4 and β2 receptor subunits in mouse brain endothelial and hippocampal cells as well as hippocampus and neocortex tissues were determined by western blot and realtime PCR, respectively. The β2 antibody showed low specificity, though. Tissues were examined following a 2-week oral treatment with various doses of varenicline (0.01, 0.1, 1, 3 mg/kg/day) or vehicle. In addition, episodic memory of mice was assessed following this treatment with an object recognition task using (1) normal mice and (2) animals with anticholinergic-induced memory impairment (i.p. injection of 0.5 mg/kg scopolamine). Varenicline dose-dependently increased protein expression of both the α4 and β2 subunit in cell cultures and brain tissues, respectively, but had no effect on mRNA expression of both subunits. Scopolamine injection induced a significant reduction of object memory in vehicle-treated mice. By contrast, cognitive performance was not altered by scopolamine in varenicline-treated mice. In conclusion, a 2-week oral treatment with varenicline prevented memory impairment in the scopolamine mouse model. In parallel, protein, but not mRNA expression was upregulated, suggesting a posttranscriptional mechanism. Our findings suggest a beneficial effect of varenicline on cognitive dysfunction.

Tobacco smoking: From 'glamour' to 'stigma'. A comprehensive review

In this narrative review, we explore the history of tobacco smoking, its associations and portrayal of its use with luxury and glamour in the past, and intriguingly, its subsequent transformation into a mass consumption industrialized product encouraged by advertising and film. Then, we describe the next phase where tobacco in parts of the world has become an unwanted product. However, the number of smokers is still increasing, especially in new markets, and increasingly younger individuals are being attracted to it, despite the well-known health consequences of tobacco use. We also explore current smoking behaviors, looking at trends in the prevalence of consumption throughout the world, discrimination against smokers, light and/or intermittent smokers, and the electronic cigarette (e-cigarette). We place these changes in the context of neuroscience, which may help explain why the cognitive effects of smoking can be important reinforcers for its consumption despite strong anti-smoking pressure in Western countries.

Modulation of social deficits and repetitive behaviors in a mouse model of autism: the role of the nicotinic cholinergic system

RATIONALE

Accumulating evidence implicates the nicotinic cholinergic system in autism spectrum disorder (ASD) pathobiology. Neuropathologic studies suggest that nicotinic acetylcholine (ACh) receptor (nAChR) subtypes are altered in brain of autistic individuals. In addition, strategies that increase ACh, the neurotransmitter for nicotinic and muscarinic receptors, appear to improve cognitive deficits in neuropsychiatric disorders and ASD.

OBJECTIVE

The aim of this study is to examine the role of the nicotinic cholinergic system on social and repetitive behavior abnormalities and exploratory physical activity in a well-studied model of autism, the BTBR T(+) Itpr3 (tf) /J (BTBR) mouse.

METHODS

Using a protocol known to up-regulate expression of brain nAChR subtypes, we measured behavior outcomes before and after BTBR and C57BL/6J (B6) mice were treated (4 weeks) with vehicle or nicotine (50, 100, 200, or 400 μg/ml).

RESULTS

Increasing nicotine doses were associated with decreases in water intake, increases in plasma cotinine levels, and at the higher dose (400 μg/ml) with weight loss in BTBR mice. At lower (50, 100 μg/ml) but not higher (200, 400 μg/ml) doses, nicotine increased social interactions in BTBR and B6 mice and at higher, but not lower doses, it decreased repetitive behavior in BTBR. In the open-field test, nicotine at 200 and 400 μg/ml, but not 100 μg/ml compared with vehicle, decreased overall physical activity in BTBR mice.

CONCLUSIONS

These findings support the hypotheses that the nicotinic cholinergic system modulates social and repetitive behaviors and may be a therapeutic target to treat behavior deficits in ASD. Further, the BTBR mouse may be valuable for investigations of the role of nAChRs in social deficits and repetitive behavior.

Adult Behavior in Male Mice Exposed to E-Cigarette Nicotine Vapors during Late Prenatal and Early Postnatal Life

Nicotine exposure has been associated with an increased likelihood of developing attention deficit hyperactivity disorder (ADHD) in offspring of mothers who smoked during pregnancy. The goal of this study was to determine if exposure to E-cigarette nicotine vapors during late prenatal and early postnatal life altered behavior in adult mice.

The human CHRNA7 and CHRFAM7A genes: A review of the genetics, regulation, and function

The human α7 neuronal nicotinic acetylcholine receptor gene (CHRNA7) is ubiquitously expressed in both the central nervous system and in the periphery. CHRNA7 is genetically linked to multiple disorders with cognitive deficits, including schizophrenia, bipolar disorder, ADHD, epilepsy, Alzheimer's disease, and Rett syndrome. The regulation of CHRNA7 is complex; more than a dozen mechanisms are known, one of which is a partial duplication of the parent gene. Exons 5-10 of CHRNA7 on chromosome 15 were duplicated and inserted 1.6 Mb upstream of CHRNA7, interrupting an earlier partial duplication of two other genes. The chimeric CHRFAM7A gene product, dupα7, assembles with α7 subunits, resulting in a dominant negative regulation of function. The duplication is human specific, occurring neither in primates nor in rodents. The duplicated α7 sequence in exons 5-10 of CHRFAM7A is almost identical to CHRNA7, and thus is not completely queried in high throughput genetic studies (GWAS). Further, pre-clinical animal models of the α7nAChR utilized in drug development research do not have CHRFAM7A (dupα7) and cannot fully model human drug responses. The wide expression of CHRNA7, its multiple functions and modes of regulation present challenges for study of this gene in disease. This article is part of the Special Issue entitled 'The Nicotinic Acetylcholine Receptor: From Molecular Biology to Cognition'.

Interaction of basal forebrain cholinergic neurons with the glucocorticoid system in stress regulation and cognitive impairment

A substantial number of studies on basal forebrain (BF) cholinergic neurons (BFCN) have provided compelling evidence for their role in the etiology of stress, cognitive aging, Alzheimer’s disease (AD), and other neurodegenerative diseases. BFCN project to a broad range of cortical sites and limbic structures, including the hippocampus, and are involved in stress and cognition. In particular, the hippocampus, the primary target tissue of the glucocorticoid stress hormones, is associated with cognitive function in tandem with hypothalamic-pituitary-adrenal (HPA) axis modulation. The present review summarizes glucocorticoid and HPA axis research to date in an effort to establish the manner in which stress affects the release of acetylcholine (ACh), glucocorticoids, and their receptor in the context of cognitive processes. We attempt to provide the molecular interactive link between the glucocorticoids and cholinergic system that contributes to BFCN degeneration in stress-induced acceleration of cognitive decline in aging and AD. We also discuss the importance of animal models in facilitating such studies for pharmacological use, to which could help decipher disease states and propose leads for pharmacological intervention.

Pharmacological analyses of learning and memory in zebrafish (Danio rerio)

Over the last decade, zebrafish (Danio rerio) have become valuable as a complementary model in behavioral pharmacology, opening a new avenue for understanding the relationships between drug action and behavior. This species offers a useful intermediate approach bridging the gap between in vitro studies and traditional mammalian models. Zebrafish offer great advantages of economy compared to their rodent counterparts, their complex brains and behavioral repertoire offer great translational potential relative to in vitro models. The development and validation of a variety of tests to measure behavior, including cognition, in zebrafish have set the stage for the use of this animal for behavioral pharmacology studies. This has led to research into the basic mechanisms of cognitive function as well as screening for potential cognition-improving drug therapies, among other lines of research. As with all models, zebrafish have limitations, which span pharmacokinetic challenges to difficulties quantifying behavior. The use, efficacy and limitations associated with a zebrafish model of cognitive function are discussed in this review, within the context of behavioral pharmacology.

Effects of acute CDP-choline treatment on resting state brain oscillations in healthy volunteers

CDP-choline (cytidine-5'-diphosphocholine) is a phospholipid used to treat cognitive disorders, presumably repairing and maintaining brain cell membranes. Additional mechanisms may include enhanced cholinergic neurotransmission as the α7 nicotinic receptor actions of choline and increased acetylcholine synthesis accompanying CDP-choline administration may modulate brain oscillations underlying cognitive processes. This study utilizes electroencephalographic (EEG) recordings in healthy volunteers to evaluate CDP-choline induction of an oscillatory response profile associated with nicotinic stimulation. Resting state EEG was acquired in 24 male volunteers administered low (500mg) and moderate (1000mg) doses of CDP-choline in a randomized placebo-controlled, crossover trial. Consistent with nicotinic agonist treatment, spectral analysis showed dose-dependent reductions in delta and increases in alpha oscillations, which were also accompanied by decreases in beta and gamma oscillatory activity. These findings support the posit that CDP-choline cognitive enhancement involves multiple mechanisms including facilitated nicotinic cholinergic action.

Neurocognitive effects of acute choline supplementation in low, medium and high performer healthy volunteers

Novel pharmacological treatments targeting alpha 7 nicotinic acetylcholine receptor (α7 nAChR) hypofunction in schizophrenia have shown mixed success in ameliorating cognitive impairments associated with this disorder. Choline, a selective agonist at α7 receptors is increased with oral administration of cytidine 5'-diphosphocholine (CDP-choline), the cognitive effects of which were assessed in healthy volunteers. Using the CogState test battery, behavioral performance in schizophrenia-relevant cognitive domains was assessed in 24 male participants following a single low (500mg) and moderate (1000mg) dose of CDP-choline. Relative to placebo, CDP-choline improved processing speed, working memory, verbal learning, verbal memory, and executive function in low baseline performers, while exerting no effects in medium baseline performers, and diminishing cognition in high baseline performers. Dose effects varied with cognitive domain but were evident with both the 500mg and 1000mg doses. These preliminary findings of cognitive enhancement in relatively impaired performers are consistent with the α7 receptor mechanism and support further trials with CDP-choline as a potential pro-cognitive strategy for cognitive impairment in schizophrenia.

Nicotinic ACh receptors as therapeutic targets in CNS disorders

The neurotransmitter acetylcholine (ACh) can regulate neuronal excitability by acting on the cys-loop cation-conducting ligand-gated nicotinic ACh receptor (nAChR) channels. These receptors are widely distributed throughout the central nervous system (CNS), being expressed on neurons and non-neuronal cells, where they participate in a variety of physiological responses such as anxiety, the central processing of pain, food intake, nicotine seeking behavior, and cognitive functions. In the mammalian brain, nine different subunits have been found thus far, which assemble into pentameric complexes with much subunit diversity; however, the α7 and α4β2 subtypes predominate in the CNS. Neuronal nAChR dysfunction is involved in the pathophysiology of many neurological disorders. Here we will briefly discuss the functional makeup and expression of the nAChRs in mammalian brain, and their role as targets in neurodegenerative diseases (in particular Alzheimer's disease, AD), neurodevelopmental disorders (in particular autism and schizophrenia), and neuropathic pain.

Stochastic cortical neurodynamics underlying the memory and cognitive changes in aging

The relatively random spiking times of individual neurons provide a source of noise in the brain. We show how this noise interacting with altered depth in the basins of attraction of networks involved in short-term memory, attention, and episodic memory provide an approach to understanding some of the cognitive changes in normal aging. The effects of the neurobiological changes in aging that are considered include reduced synaptic modification and maintenance during learning produced in part through reduced acetylcholine in normal aging, reduced dopamine which reduces NMDA-receptor mediated effects, reduced noradrenaline which increases cAMP and thus shunts excitatory synaptic inputs, and the effects of a reduction in acetylcholine in increasing spike frequency adaptation. Using integrate-and-fire simulations of an attractor network implementing memory recall and short-term memory, it is shown that all these changes associated with aging reduce the firing rates of the excitatory neurons, which in turn reduce the depth of the basins of attraction, resulting in a much decreased probability in maintaining in short-term memory what has been recalled from the attractor network. This stochastic dynamics approach opens up new ways to understand and potentially treat the effects of normal aging on memory and cognitive functions.

Administration of the nicotinic acetylcholine receptor agonists ABT-089 and ABT-107 attenuates the reinstatement of nicotine-seeking behavior in rats

Current smoking cessation pharmacotherapies have modest efficacy, and most smokers relapse within the first few days after a quit attempt. Nicotine withdrawal-induced craving and cognitive impairments predict smoking relapse during abstinence and suggest that cognitive-enhancing drugs may prevent relapse. ABT-089 and ABT-107 are subtype-selective nAChR agonists that improve cognitive performance in laboratory animals. However, there are no studies examining the effects of ABT-089 and ABT-107 on nicotine self-administration and the reinstatement of nicotine-seeking behavior, an animal model of relapse in human smokers. The goal of the present study was to determine the effects of the α4β2*/α6β2* nAChR agonist ABT-089 and the α7 nAChR agonist ABT-107 on nicotine taking and seeking in rats. The effects of acute ABT-089 and ABT-107 pretreatment on nicotine self-administration and reinstatement were tested in male Sprague Dawley rats. Parallel studies of ABT-089 and ABT-107 on sucrose self-administration and reinstatement were tested in separate groups of rats to determine if the effects of these drug treatments generalized to other reinforced behaviors. Nicotine and sucrose self-administration behaviors were not altered following acute administration of ABT-089 (0, 0.12, 1.2 and 12.0mg/kg) or ABT-107 (0, 0.03 and 0.3mg/kg). In contrast, both ABT-089 and ABT-107 pretreatment dose-dependently attenuated nicotine reinstatement. These effects were reinforcer-specific as no effects of ABT-089 or ABT-107 pretreatment on sucrose seeking were noted. Taken together, these findings suggest that ABT-089 and ABT-107 do not affect nicotine consumption, but may reduce the likelihood that a smoking lapse will lead to relapse.

Effects of nicotine administration on spectral and temporal features of crystallized song in the adult male zebra finch

INTRODUCTION

The process through which the zebra finch (Taeniopygia guttata) acquires and produces crystallized song has long been thought of as highly analogous to the process through which humans acquire and produce speech. Nicotinic acetylcholine receptors are present in song nuclei that play important roles in song production and/or acquisition. We studied the effect of in vivo nicotine on temporal and spectral features of crystallized song.

METHODS

We used 16 adult male zebra finches that were exposed to an established 7-day nicotine or saline treatment. Song behavior was monitored for a 2-month period following the cessation of the nicotine/saline treatment. All animals served as their own control in order to determine whether any song characteristics changed over the observed time period compared to the baseline measurement.

RESULTS

Inter-syllable duration and Wiener entropy were significantly affected by the in vivo administration of nicotine. These observed changes persisted for a 2-month period following the cessation of nicotine exposure. Similar changes were not observed in the age-matching control group.

CONCLUSIONS

Nicotine significantly affected tempo and rhythm of the crystallized zebra finch song. We believe that this in vivo nicotine-exposed zebra finch model can not only provide a further understanding of the underlying behavioral mechanisms of the cognitive implications of nicotine dependence but also help in the development of therapeutics targeting cognitive deficits often observed during nicotine withdrawal.