The effects of nicotine on the attentional modification of the acoustic startle response in nonsmokers

The influence of stimulus onset asynchrony, task order, sex and hormonal contraception on prepulse inhibition and prepulse facilitation: Methodological considerations for drug and imaging research

BACKGROUND

Prepulse-induced startle modulation occurs when a weak sensory stimulus ('prepulse') is presented before a startling sensory stimulus ('pulse'), producing an inhibited (Prepulse Inhibition, PPI) or facilitated (Prepulse Facilitation, PPF) startle response. We recently identified several gaps and outlined future lines of enquiry to enable a fuller understanding of the neurobiology of PPI and PPF in healthy and clinical populations. However, before embarking on these studies, it is important to consider how task and population characteristics affect these phenomena in healthy humans.

METHODS

We examined PPI and PPF in separate tasks, with counterbalanced task order across participants in one session, using a range of stimulus onset asynchronies (SOAs), in 48 healthy adults (23 men, 25 women; 10 hormonal contraceptive users) to determine which SOAs produce the strongest PPI and PPF and also explored how sex and hormonal contraception might influence PPI and PPF under these experimental conditions.

RESULTS

Both PPI and PPF were affected by SOA, with greatest PPI observed at 60 and 120 ms, and greatest PPF at 4500 and 6000 ms. PPI was influenced by sex (more PPI in men than women) and hormonal contraception, whereas PPF was affected by task order (greater PPF when the PPF task followed, rather than preceded, the PPI task).

CONCLUSIONS

Our findings indicate that studies of PPI and PPF need to consider, not only sex and hormonal status of study participants, but also task characteristics and presentation order to reduce variance and increase replicability across studies.

Comparative Analysis of Dopaminergic and Cholinergic Mechanisms of Sensory and Sensorimotor Gating in Healthy Individuals and in Patients With Schizophrenia

Sensory and sensorimotor gating provide the early processing of information under conditions of rapid presentation of multiple stimuli. Gating deficiency is observed in various psychopathologies, in particular, in schizophrenia. However, there is also a significant proportion of people in the general population with low filtration rates who do not show any noticeable cognitive decline. The review article presents a comparative analysis of existing data on the peculiarities of cholinergic and dopaminergic mechanisms associated with lowering gating in healthy individuals and in patients with schizophrenia. The differences in gating mechanisms in cohorts of healthy individuals and those with schizophrenia are discussed.

Baseline performance moderates stimulant effects on cognition in youth with ADHD

Attention-deficit/hyperactivity disorder is associated with impaired cognitive functioning and increased delay discounting (i.e., a stronger preference for immediate reward). At the group level, stimulant medication improves cognition and delay discounting, yet not all children exhibit problems in these domains, and previous work has not examined whether stimulant-induced improvements are moderated by baseline performance. To address this question in the current study, 82 children with attention-deficit/hyperactivity disorder (9-12 years old) attended a week-long research camp. On the baseline day (Monday), participants completed tasks of inhibitory control, visuospatial working memory, reaction time variability, and delay discounting. Children then completed a 3-day, randomized, double-blind, placebo-controlled trial of ∼1 mg/kg and 2 mg/kg long-acting methylphenidate (mean doses = 39.1 and 74.3 mg, respectively), during which they were readministered the battery of tasks. Cognitive composites (mean of inhibitory control, working memory, and reaction time variability performance) were created for the baseline and medication evaluation phases. As predicted, the extent to which cognition was improved with medication compared with placebo and with 2 mg/kg compared with 1 mg/kg was greatest among children with poorer baseline cognitive function. Children with stronger baseline cognition exhibited less improvement with methylphenidate compared with placebo and did not benefit from the 2 compared with the 1 mg/kg dose. In contrast, medication-related improvement in delay discounting was unrelated to baseline discounting. Given that improving cognitive function is one potential mechanisms by which stimulants exert their therapeutic effects, this study has significant implications for understanding how and for whom stimulant medication works. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Physiological parameters of mental health predict the emergence of post-traumatic stress symptoms in physicians treating COVID-19 patients

Lack of established knowledge and treatment strategies, and change in work environment, may altogether critically affect the mental health and functioning of physicians treating COVID-19 patients. Thus, we examined whether treating COVID-19 patients affect the physicians' mental health differently compared with physicians treating non-COVID-19 patients. In this cohort study, an association was blindly computed between physiologically measured anxiety and attention vigilance (collected from 1 May 2014 to 31 May 31 2016) and self-reports of anxiety, mental health aspects, and sleep quality (collected from 20 April to 30 June 2020, and analyzed from 1 July to 1 September 2020), of 91 physicians treating COVID-19 or non-COVID-19 patients. As a priori hypothesized, physicians treating COVID-19 patients showed a relative elevation in both physiological measures of anxiety (95% CI: 2317.69-2453.44 versus 1982.32-2068.46; P < 0.001) and attention vigilance (95% CI: 29.85-34.97 versus 22.84-26.61; P < 0.001), compared with their colleagues treating non-COVID-19 patients. At least 3 months into the pandemic, physicians treating COVID-19 patients reported high anxiety and low quality of sleep. Machine learning showed clustering to the COVID-19 and non-COVID-19 subgroups with a high correlation mainly between physiological and self-reported anxiety, and between physiologically measured anxiety and sleep duration. To conclude, the pattern of attention vigilance, heightened anxiety, and reduced sleep quality findings point the need for mental intervention aimed at those physicians susceptible to develop post-traumatic stress symptoms, owing to the consequences of fighting at the forefront of the COVID-19 pandemic.

Nicotine Enhances Amplitude and Consistency of Timing of Responses to Acoustic Trains in A1

Systemic nicotine enhances neural processing in primary auditory cortex (A1) as determined using tone-evoked, current-source density (CSD) measurements. For example, nicotine enhances the characteristic frequency (CF)-evoked current sink in layer 4 of A1, increasing amplitude and decreasing latency. However, since presenting auditory stimuli within a stream of stimuli increases the complexity of response dynamics, we sought to determine the effects of nicotine on CSD responses to trains of CF stimuli (one-second trains at 2–40 Hz; each train repeated 25 times). CSD recordings were obtained using a 16-channel multiprobe inserted in A1 of urethane/xylazine-anesthetized mice, and analysis focused on two current sinks in the middle (layer 4) and deep (layers 5/6) layers. CF trains produced adaptation of the layer 4 response that was weak at 2 Hz, stronger at 5–10 Hz and complete at 20–40 Hz. In contrast, the layer 5/6 current sink exhibited less adaptation at 2–10 Hz, and simultaneously recorded auditory brainstem responses (ABRs) showed no adaptation even at 40 Hz. Systemic nicotine (2.1 mg/kg) enhanced layer 4 responses throughout the one-second stimulus train at rates ≤10 Hz. Nicotine enhanced both response amplitude within each train and the consistency of response timing across 25 trials. Nicotine did not alter the degree of adaptation over one-second trials, but its effect to increase amplitudes revealed a novel, slower form of adaptation that developed over multiple trials. Nicotine did not affect responses that were fully adapted (20–40 Hz trains), nor did nicotine affect any aspect of the layer 5/6 current sink or ABRs. The overall effect of nicotine in layer 4 was to enhance all responses within each train, to emphasize earlier trials across multiple trials, and to improve the consistency of timing across all trials. These effects may improve processing of complex acoustic streams, including speech, that contain information in the 2–10 Hz range.

Nicotine enhances auditory processing in healthy and normal-hearing young adult nonsmokers

RATIONALE

Electrophysiological studies show that systemic nicotine narrows frequency receptive fields and increases gain in neural responses to characteristic frequency stimuli. We postulated that nicotine enhances related auditory processing in humans.

OBJECTIVES

The main hypothesis was that nicotine improves auditory performance. A secondary hypothesis was that the degree of nicotine-induced improvement depends on the individual's baseline performance.

METHODS

Young (18-27 years old), normal-hearing nonsmokers received nicotine (Nicorette gum, 6mg) or placebo gum in a single-blind, randomized, crossover design. Subjects performed four experiments involving tone-in-noise detection, temporal gap detection, spectral ripple discrimination, and selective auditory attention before and after treatment. The perceptual differences between posttreatment nicotine and placebo conditions were measured and analyzed as a function of the pre-treatment baseline performance.

RESULTS

Nicotine significantly improved performance in the more difficult tasks of tone-in-noise detection and selective attention (effect size = - 0.3) but had no effect on relatively easier tasks of temporal gap detection and spectral ripple discrimination. The two tasks showing significant nicotine effects further showed no baseline-dependent improvement.

CONCLUSIONS

Nicotine improves auditory performance in difficult listening situations. The present results support future investigation of nicotine effects in clinical populations with auditory processing deficits or reduced cholinergic activation.

Hypothalamic-pituitary-adrenal axis responsiveness, startle response, and sensorimotor gating in late pregnancy

During pregnancy, the hypothalamic-pituitary-adrenal (HPA) axis, the main regulator of the stress response, undergoes dramatic changes. The acoustic startle response (ASR) and the prepulse inhibition (PPI) of the startle response are neurophysiological research tools and objective measures of an individual's response to an emotional context or stressor. The ASR and PPI are influenced by psychiatric diseases characterized by anxiety symptoms and are sensitive to cortisol. Hence, the ASR and the PPI can be used to investigate the effects of pregnancy-induced endocrine changes and their contribution to affective disorders. The present study sought to investigate the association between measures of HPA-axis responsiveness, startle reactivity and sensorimotor gating during pregnancy that to date remains unknown. The eye-blink component of the ASR, and its prepulse inhibition, were measured in 107 late third trimester pregnant women. Saliva samples were collected to assess the cortisol awakening response (CAR), a measure of HPA-axis activity. Blood was sampled to measure serum levels of cortisol, cortisone and the cortisone to cortisol ratio. Ongoing anxiety disorders, sleep duration, smoking, and age were considered as potential confounders in the statistical analyses. CAR reactivity, measured as area under the curve (AUC) increase and above baseline, was positively associated with baseline startle magnitude [Cohen's d = 0.27; F (1, 105) = 4.99; p = 0.028, and Cohen's d = 0.30; F (1, 105) = 6.25; p = 0.014, respectively] as well as PPI at 86 dB [Cohen's d = 0.29; F (1, 105) = 5.93; p = 0.017; and Cohen's d = 0.34; F (1, 105) = 8.38; p = 0.005, respectively]. The observed positive correlation between startle magnitude in pregnant women and greater increase in cortisol during the awakening response may be interpreted as heightened neurophysiological reactivity, likely associated with dysregulation of the stress system.

Association analysis of CHRNA3 polymorphisms with schizophrenia in a Chinese Han population: A case-control study

Schizophrenia (SCZ) is a highly heritable, chronic, severe psychiatric disorder associated with significant financial costs to families and societies. In this case-control study, we investigated the associations between seven SNPs in CHRNA3 gene and the risk of SCZ.A total of 1071 (384 cases and 687 controls) unrelated subjects were recruited for our association study. Seven candidate tagging SNPs in CHRNA3 gene (rs3743077, rs1317286, rs938682, rs12914385, rs2869546, rs3743075, rs8040868) selected in HapMap database were genotyped by Sequenom MassARRAY. Finally, association analysis was conducted under various models.According to our results, in genetic model analysis, rs12914385 and rs8040868 are associated with decreased risk of SCZ in female subgroup; rs3743075 is associated with decreased risk of SCZ in subgroup with age <45; while rs3743077 and rs2869546 are associated with increased risk of SCZ. Haplotype analysis suggested that the 3 variants comprised 1 block, and that the haplotype Ars938682Crs12914385Crs2869546 was significantly correlated with an increased risk of SCZ in the subgroup with age ≥45.Our data indicate potential associations between CHRNA3polymorphisms and SCZ susceptibility, and the significant variants identified in our study may be used as genetic biomarkers for SCZ susceptibility in Chinese Han population.

Nicotine effects on exercise performance and physiological responses in nicotine-naïve individuals: a systematic review

The purpose of this systematic review was to evaluate the effects of smokeless forms of nicotine on physiological responses and exercise performance. Methodology and reporting were based on the PRISMA statement. The intervention was defined as any product containing nicotine that did not require smoking. Searches were conducted across two electronic databases with supplementary approaches utilized. Studies were selected following set inclusion and exclusion criteria and checked by two independent authors. A modified PEDro scale was utilized to rate study quality with studies averaging 9·3/13. Six studies assessed exercise performance with endurance-based parameters reported as significantly improved with nicotine in one study, while anaerobic parameters were unaffected or decreased compared to placebo except in one study which reported enhanced leg extensor torque but no effect on countermovement jump or Wingate anaerobic capacity. Sixteen of 28 studies investigating physiological responses reported that nicotine significantly increased heart rate compared to placebo or control. Blood pressure and blood flow were also reported as significantly increased in multiple studies. While there is strong evidence of nicotine-induced changes in physiological function that would benefit physical performance, beneficial effects have only been reported on leg extensor torque and endurance performance by one study each. Subsequently, there is need for more research with strong methodological quality to definitively evaluate nicotine's potential as an ergogenic aid.

Smoking-induced affect modulation in nonwithdrawn smokers with posttraumatic stress disorder, depression, and in those with no psychiatric disorder

This research sought to determine whether smoking influences affect by means other than withdrawal reduction. Little previous evidence suggests such an effect. We surmised that such an effect would be especially apparent in posttraumatic stress disorder (PTSD) and major depressive disorder (MDD), 2 disorders that are frequently comorbid with smoking and that involve dysregulated affect. Participants were U.S. veterans who were regular smokers (N = 159): 52 with PTSD (58% with comorbid MDD), 51 with MDD, and 56 controls with no psychiatric disorder. During 3 positive and 3 negative mood induction trials (scheduled over 2 sessions), nonwithdrawn participants smoked either a nicotine-containing cigarette (NIC+), a nicotine-free cigarette (NIC-), or held a pen. Positive and negative affect were each measured before and after mood induction. Results showed a significant 2-way interaction of Smoking Condition × Time on negative affect during the negative mood induction (F(6, 576) = 2.41, p = .03) in those with PTSD and controls. In these groups, both NIC+ and NIC-, relative to pen, produced lower negative affect ratings after the negative mood induction. There was also a 2-way interaction of Smoking Condition × Time on positive affect response to the positive mood induction among those with PTSD and controls (F(6, 564) = 3.17, p = .005) and among MDD and controls (F(6, 564) = 2.27, p = .036). Among all smokers, NIC+ enhanced the magnitude and duration of positive affect more than did NIC-. Results revealed affect modulation outside the context of withdrawal relief; such effects may motivate smoking among those with psychiatric diagnoses, and among smokers in general. (PsycINFO Database Record

The Return of Rate Dependence

Rate dependence, a well-known phenomenon in behavioral pharmacology, appears to have declined as a topic of interest, perhaps, as a result of being viewed pertinent to only the preclinical investigation of drugs on schedule-controlled performance. Obstacles to data interpretation due to conflation with regression to the mean also appear to have contributed to the topic's decline. Despite this reduction in exposure, rate dependence is a useful concept and tool that can be used to determine sources of variability, predict therapeutic outcomes, and identify individuals that are most likely to respond therapeutically. Armed with new statistical methods and an understanding of the broad range of conditions under which rate dependence can be observed, we urge researchers to revisit the concept, use the appropriate analysis methods, and to design empirical studies a priori to further explore rate dependence.

Moderation of nicotine effects on covert orienting of attention tasks by poor placebo performance and cue validity

INTRODUCTION AND RATIONALE

Given baseline-dependent effects of nicotine on other forms of attention, there is reason to believe that inconsistent findings for the effects of nicotine on attentional orienting may be partly due to individual differences in baseline (abstinence state) functioning. Individuals with low baseline attention may benefit more from nicotine replacement.

METHOD

The effects of nicotine as a function of baseline performance (bottom, middle, and top third of mean reaction times during placebo) were assessed in 52 habitual abstinent smokers (26 females/26 males) utilizing an arrow-cued covert orienting of attention task.

RESULTS

Compared to a placebo patch, a 14mg nicotine patch produced faster overall reaction times (RTs). In addition, individuals with slower RTs during the placebo condition benefitted more from nicotine on cued trials than did those who had shorter (faster) RTs during placebo. Nicotine also enhanced the validity effect (shorter RTs to validly vs. invalidly cued targets), but this nicotine benefit did not differ as a function of overall placebo-baseline performance.

CONCLUSIONS

These findings support the view that nicotine enhances cued spatial attentional orienting in individuals who have slower RTs during placebo (nicotine-free) conditions; however, baseline-dependent effects may not generalize to all aspects of spatial attention. These findings are consistent with findings indicating that nicotine's effects vary as a function of task parameters rather than simple RT speeding or cognitive enhancement.

Order in the absence of an effect: Identifying rate-dependent relationships

The heterogeneity of group data can obscure a significant effect of an intervention due to differential baseline scores. Instead of discarding the seemingly heterogeneous response set, an orderly lawful relationship could be present. Rate dependence describes a pattern between a baseline and the change in that baseline following some intervention. To highlight the importance of analyzing data from a rate-dependent perspective, we (1) briefly review research illustrating that rate-dependent effects can be observed in response to both drug and non-drug interventions in varied schedules of reinforcement in clinical and preclinical populations; (2) observe that the process of rate-dependence likely requires multiple parts of a system operating simultaneously to evoke differential responding as a function of baseline; and (3) describe several statistical methods for consideration and posit that Oldham's correlation is the most appropriate for rate-dependent analyses. Finally, we propose future applications for these analyses in which the level of baseline behavior exhibited prior to an intervention may determine the magnitude and direction of behavior change and can lead to the identification of subpopulations that would be benefitted. In sum, rate dependence is an invaluable perspective to examine data following any intervention in order to identify previously overlooked results.

Effects of intravenous nicotine on prepulse inhibition in smokers and non-smokers: relationship with familial smoking

RATIONALE

The reinforcing properties of nicotine may be, in part, derived from its ability to enhance certain forms of cognitive processing. Several animal and human studies have shown that nicotine increases prepulse inhibition (PPI) of the startle reflex. However, it remains unclear whether these effects are related to smoking susceptibility.

OBJECTIVES

The current study examined the effects of intravenously delivered nicotine on PPI in smokers and non-smokers, as well as its association with a quantitative index of familial smoking.

METHODS

The sample consisted of 30 non-smokers and 16 smokers, who completed an initial assessment, followed on a separate day by a laboratory assessment of PPI prior to and following each of two intravenous nicotine infusions. Separate doses were used in smoker and non-smoker samples.

RESULTS

Analyses indicated that both nicotine infusions acutely enhanced PPI among non-smokers, and this enhancement was positively related to the degree of smoking among first and second-degree relatives. Smokers also displayed PPI enhancement after receiving the first infusion, but this effect was unrelated to familial smoking.

CONCLUSIONS

These data suggest that the PPI paradigm may have utility as an endophenotype for cognitive processes which contribute to smoking risk.

The effect of nicotine on sensorimotor gating is modulated by a CHRNA3 polymorphism

RATIONALE

Prepulse inhibition (PPI) of the acoustic startle response, a measure of sensorimotor gating, can be enhanced by nicotine. Moreover, the TT genotype of the nicotinic acetylcholine receptor (nAChR) α3-subunit (CHRNA3) rs1051730 polymorphism has previously been associated with diminished PPI and nicotine dependence.

OBJECTIVES

We tested whether this CHRNA3 polymorphism also modulates the nicotine-induced enhancement of PPI.

METHODS

We assessed the effect of nicotine on PPI, startle reactivity, and habituation in 52 healthy nonsmoking volunteers genotyped for CHRNA3 rs1051730 in a double-blind, placebo-controlled, counterbalanced, within-subjects design. Additionally, cotinine plasma levels were measured.

RESULTS

Nicotine significantly enhanced PPI in TT homozygotes only and tended to worsen PPI in TC and CC carriers. Additionally, nicotine significantly reduced startle habituation.

CONCLUSIONS

The present findings imply that the effect of nicotine on sensorimotor gating is modulated by nAChR α3-subunits. Thus, genetic variation in nicotinic receptor genes might be an important connecting link between early attentional processes and smoking behavior.

The effect of withdrawal and intake of nicotine on smokers' ability to ignore distractors in a number parity decision task

Nicotine's attention enhancing effects are often attributed to enhancement of stimulus filtering by the attention networks. We investigated distractibility in 20 abstinent cigarette smokers (9 hours overnight; phase 1) and tested them again after smoking one cigarette (phase 2). Their performance was compared to 20 nonsmokers (no nicotine intake). In an auditory number parity decision task, participants had to make a forced choice "odd" or "even" decision about centrally presented numbers between 2 and 9, while ignoring laterally presented preceding or simultaneous novel distractors. In phase 1, distractors that preceded goal stimuli slowed reaction times (RTs) more than simultaneously presented distractors in both groups. In phase 2, nicotine intake speeded RTs in smokers in all conditions and reduced RT variability for simple number decisions and simultaneous distractors. Overall, there was a nonsignificant trend for smokers to be less accurate than nonsmokers. Accuracy in the simultaneous distractor condition decreased in both groups in phase 2. We argue that the observed nicotine-induced improvements on behavioral performance primarily reflect enhancement of top-down control of attention.

Galantamine attenuates some of the subjective effects of intravenous nicotine and improves performance on a Go No-Go task in abstinent cigarette smokers: a preliminary report

RATIONALE

Galantamine (GAL), a reversible and competitive inhibitor of acetylcholinesterase, is used clinically in the treatment of Alzheimer's dementia. Some preclinical and clinical studies support the potential efficacy of cholinesterase inhibitors for smoking cessation, although their effects on the behavioral and physiological responses to nicotine have not been examined. The goal of this study was to characterize GAL's actions on multiple outcomes, including withdrawal severity and cognitive performance, as well as subjective and physiological responses to nicotine administered intravenously.

METHODS

A total of 12 smokers participated in a double-blind, placebo-controlled, crossover study. Smokers had two 4-day treatment periods, assigned in random sequence, to GAL (8 mg/day) or placebo treatment. On day 4 of each treatment phase, smokers had an experimental session in which they received an intravenous (IV) dose of saline or 1 mg/70 kg nicotine, 1 h apart, in a random order.

RESULTS

GAL attenuated the self-reported rating of "craving for cigarettes" and prevented decrements in performance in a Go/No-Go task. In response to IV nicotine, GAL treatment attenuated the self-report ratings of "like the drug effects," "good drug effects," "bad drug effects," and "stimulated."

CONCLUSIONS

These findings support the potential utility of GAL as a treatment for smoking cessation.

Effects of smoking abstinence on impulsive behavior among smokers high and low in ADHD-like symptoms

RATIONALE

Impulsivity, a multifaceted construct that includes inhibitory control and heightened preference for immediate reward, is central to models of drug use and abuse. Within a self-medication framework, abstinence from smoking may lead to an increase in impulsive behavior and the likelihood of relapse, particularly among persons with disorders (e.g., attention-deficit/hyperactivity disorder, ADHD) and personality traits (e.g., impulsivity) linked to impulsive behavior.

OBJECTIVES

This study aimed to examine the effects of smoking abstinence on multiple measures of impulsivity among a non-clinical sample of adult smokers selected for high and low levels of ADHD symptoms.

METHODS

In a within-subjects design, participants selected for high or low levels of self-reported ADHD symptoms (N = 56) completed sessions following overnight abstinence and when smoking as usual (order counterbalanced). Measures of impulsive behavior included response inhibition (i.e., stop signal task), interference control (i.e., attentional modification of prepulse inhibition (PPI) of startle), and impulsive choice (i.e., hypothetical delay discounting).

RESULTS

As hypothesized, abstinence decreased response inhibition and PPI. Although ADHD symptoms moderated abstinence effects on impulsive choice and response inhibition, the pattern was opposite to our predictions: the low-ADHD group responded more impulsively when abstinent, whereas the high-ADHD group was relatively unaffected by abstinence.

CONCLUSIONS

These findings highlight the importance of utilizing multiple laboratory measures to examine a multifactorial construct such as impulsive behavior and raise questions about how best to assess symptoms of ADHD and impulsivity among non-abstinent smokers.

Effects of nicotine on attention and inhibitory control in healthy nonsmokers

Nicotine improves cognitive functioning in smokers and psychiatric populations, but its cognitive-enhancing effects in healthy nonsmokers are less well understood. Nicotine appears to enhance certain forms of cognition in nonsmokers, but its specificity to subtypes of cognition is not known. This study sought to replicate and extend previous findings on the effects of nicotine on cognitive performance in healthy nonsmokers. Healthy young adults (N = 40, 50% women) participated in a placebo-controlled, double-blind, repeated measures experiment examining the effects of 7 mg transdermal nicotine or placebo. Participants completed tests of attention (Attention Network Test), behavioral inhibition (stop signal task, Stroop test), reward responsiveness (signal detection task), and risk-taking behavior (Balloon Analogue Risk Task). Physiological (heart rate, blood pressure) and subjective (Profile of Mood States, Drug Effects Questionnaire) measures were also obtained. Nicotine significantly improved performance only on the Stroop test, but it impaired performance on one aspect of the Attention Network Test, the orienting effect. Nicotine produced its expected effects on physiologic and subjective measures within the intended time course. The findings of this study contribute to a growing literature indicating that nicotine differentially affects specific subtypes of cognitive performance in healthy nonsmokers.

Cognitive effects of nicotine: genetic moderators

Cigarette smoking is the main preventable cause of death in developed countries, and the development of more effective treatments is necessary. Cumulating evidence suggests that cognitive enhancement may contribute to the addictive actions of nicotine. Several studies have demonstrated that nicotine enhances cognitive performance in both smokers and non-smokers. Genetic studies support the role of both dopamine (DA) and nicotinic acetylcholine receptors (nAChRs) associated with nicotine-induced cognitive enhancement. Based on knockout mice studies, beta2 nAChRs are thought to be essential in mediating the cognitive effects of nicotine. alpha7nAChRs are associated with attentional and sensory filtering response, especially in schizophrenic individuals. Genetic variation in D2 type DA receptors and the catechol-O-methyltransferase enzyme appears to moderate cognitive deficits induced by smoking abstinence. Serotonin transporter (5-HTT) gene variation also moderates nicotine-induced improvement in spatial working memory. Less is known about the contribution of genetic variation in DA transporter and D4 type DA receptor genetic variation on the cognitive effects of nicotine. Future research will provide a clearer understanding of the mechanism underlying the cognitive-enhancing actions of nicotine.

Sensorimotor gating is associated with CHRNA3 polymorphisms in schizophrenia and healthy volunteers

Attentional gating deficits, commonly measured by prepulse inhibition (PPI) of the acoustic startle response (ASR), have been established as an endophenotype of schizophrenia. Prepulse inhibition is heritable and has been associated with polymorphisms in serotonin and dopamine system genes. Prepulse inhibition can be enhanced by nicotine, and therefore it has been proposed that schizophrenia patients smoke to ameliorate their early attentional deficits. The PPI-enhancing effects of nicotine in rodents are strain dependent, suggesting a genetic contribution to PPI within the nicotinic acetylcholine receptor (nAChR) system. Recent human genetic studies also imply that tobacco dependence is affected by polymorphisms in the alpha3/alpha5 subunits of the nAChR (CHRNA3/CHRNA5) gene cluster. We, therefore, investigated the impact of two common CHRNA3 polymorphisms (rs1051730/rs1317286) on PPI, startle reactivity, and habituation of the ASR in two independent samples of 107 healthy British volunteers and 73 schizophrenia patients hailing from Germany. In both samples, PPI was influenced by both CHRNA3 polymorphisms (combined p-value=0.0027), which were strongly linked. Moreover, CHRNA3 genotype was associated with chronicity, treatment, and negative symptoms in the schizophrenia sample. These results suggest that sensorimotor gating is influenced by variations of the CHRNA3 gene, which might also have an impact on the course and severity of schizophrenia.

Methylphenidate enhances prepulse inhibition during processing of task-relevant stimuli in attention-deficit/hyperactivity disorder

ADHD is characterized by inattention, hyperactivity, and disinhibition, including the inability to screen out distracting stimuli. Prepulse inhibition (PPI) of startle indexes a related gating process and is enhanced during attended compared to ignored stimuli. We predicted that PPI during attended stimuli would be enhanced by the stimulant methylphenidate (MPH) and that this effect would be moderated by baseline PPI. Children with ADHD (n=36) completed a baseline day and a randomized, double-blind medication trial (placebo vs. sustained release MPH). Bilateral startle eyeblink EMG was measured during a tone discrimination task. MPH enhanced PPI during attended, but not during ignored stimuli. Extending findings that pretreatment functioning moderates stimulant effects on PPI, this effect tended to be inversely related to baseline PPI. These data fit with the clinical literature on ADHD and the hypothesis that MPH enhances interference control for important environmental stimuli.

Smoking and depression: Is smoking cessation effective?

Patients with depression tend to have a higher rate of smoking and an increased severity of nicotine dependence. It seems that common genetic and environmental factors may influence the bimodal relationship between smoking and depression. Nicotine has some positive reinforcing/rewarding effects that may affect people with mood disorders and smoking is also used as a ;relief medication' in order to ameliorate symptoms of depression, as it is already known that nicotine, which is the major psychoactive ingredient in tobacco, may act as an antidepressant. To date, the data regarding the difficulty in smoking cessation in depressed smokers are conflicting. Low confidence and self-esteem among this group of smokers are significant predictors of failure during smoking cessation attempt. In the most recently published guidelines for smokers with psychiatric comorbidities the suggestion is for combination treatment (counseling and pharmaceutical treatment) and prolongation of a therapeutic approach.

Preclinical pharmacology of the alpha4beta2 nAChR partial agonist varenicline related to effects on reward, mood and cognition

The pharmacological properties and pharmacokinetic profile of the alpha4beta2 nicotinic acetylcholine receptor (nAChR) partial agonist varenicline provide an advantageous combination of free brain levels and functional potencies at the target receptor that for a large part explain its efficacy as a smoking cessation aid. Since alpha4beta2 and other nAChR subtypes play important roles in mediating central processes that control reward, mood, cognition and attention, there is interest in examining the effects of selective nAChR ligands such as varenicline in preclinical animal models that assess these behaviors. Here we describe results from studies on varenicline's effects in animal models of addiction, depression, cognition and attention and discuss these in the context of recently published preclinical and preliminary clinical studies that collected data on varenicline's effects on mood, cognition and alcohol abuse disorder. Taken together, the preclinical and the limited clinical data show beneficial effects of varenicline, but further clinical studies are needed to evaluate whether the preclinical effects observed in animal models are translatable to the clinic.