Effect of subcutaneous nicotine injections of EEG alpha frequency in non-smokers: a placebo-controlled pilot study

The effects of oral nicotine administration and abstinence on sleep in male C57BL/6J mice

BACKGROUND

Sleep disturbances are common in smoking cessation attempts and are predictive of relapse. Despite this knowledge, there is no established animal model to study the effect of nicotine abstinence on sleep and EEG parameters.

OBJECTIVES

The present study was conducted to characterize sleep and wakefulness in male C57BL/6J mice during periods of oral nicotine administration and abstinence.

METHODS

Male C57BL/6J mice were implanted with EEG/EMG recording devices. EEG/EMG data were recorded continuously for a period of 4 weeks. At the beginning of week 2, 200 μg/ml of nicotine was added to the 0.2% saccharin vehicle drinking solution. Following a 2-week period of oral nicotine administration, abstinence was initiated by excluding the nicotine from the 0.2% saccharin vehicle drinking solution. EEG/EMG were analyzed at pre-nicotine baseline, during nicotine administration, and on days 1, 2, and 5 of abstinence from nicotine.

RESULTS

Oral nicotine administration decreased total sleep time during the active phase, consistent with the stimulant actions of nicotine. In contrast, NREM sleep quantity was increased during the active phase on nicotine abstinence day 1 and REM sleep was decreased during days 2 and 5 of abstinence. Further, sleep fragmentation was increased during the inactive phase on all days of abstinence. Oral nicotine administration and abstinence from nicotine also altered EEG relative power frequencies during the inactive and active phase.

CONCLUSIONS

Both oral nicotine administration and abstinence lead to sleep disturbances in mice. Similarities between this model and human reports on the effect of nicotine/nicotine withdrawal on sleep support its utility in examining the molecular mechanisms that modulate the relationship between sleep, nicotine, and nicotine abstinence/withdrawal.

On the Physiological Modulation and Potential Mechanisms Underlying Parieto-Occipital Alpha Oscillations

The parieto-occipital alpha (8–13 Hz) rhythm is by far the strongest spectral fingerprint in the human brain. Almost 90 years later, its physiological origin is still far from clear. In this Research Topic I review human pharmacological studies using electroencephalography (EEG) and magnetoencephalography (MEG) that investigated the physiological mechanisms behind posterior alpha. Based on results from classical and recent experimental studies, I find a wide spectrum of drugs that modulate parieto-occipital alpha power. Alpha frequency is rarely affected, but this might be due to the range of drug dosages employed. Animal and human pharmacological findings suggest that both GABA enhancers and NMDA blockers systematically decrease posterior alpha power. Surprisingly, most of the theoretical frameworks do not seem to embrace these empirical findings and the debate on the functional role of alpha oscillations has been polarized between the inhibition vs. active poles hypotheses. Here, I speculate that the functional role of alpha might depend on physiological excitation as much as on physiological inhibition. This is supported by animal and human pharmacological work showing that GABAergic, glutamatergic, cholinergic, and serotonergic receptors in the thalamus and the cortex play a key role in the regulation of alpha power and frequency. This myriad of physiological modulations fit with the view that the alpha rhythm is a complex rhythm with multiple sources supported by both thalamo-cortical and cortico-cortical loops. Finally, I briefly discuss how future research combining experimental measurements derived from theoretical predictions based of biophysically realistic computational models will be crucial to the reconciliation of these disparate findings.

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.

Encephalography Connectivity on Sources in Male Nonsmokers after Nicotine Administration during the Resting State

We present an encephalography (EEG) connectivity study where 30 healthy male nonsmokers were randomly allocated either to a nicotine group (14 subjects, 7 mg of transdermal nicotine) or to a placebo group. EEG activity was recorded in an eyes-open (EO) and eyes-closed (EC) condition before and after drug administration. This is a reanalysis of a previous dataset. Through a source reconstruction procedure, we extracted 13 time series representing 13 sources belonging to a resting-state network. Here, we conducted connectivity analysis (renormalized partial directed coherence; rPDC) on sources, focusing on the frequency range of 8.5-18.4 Hz, subdivided into 3 frequency bands (α1, α2, and β1) with the hypothesis that an increase in vigilance would modulate connectivity. Furthermore, a phase-amplitude coupling (mean resultant vector length; VL) analysis, was performed investigating whether an increase of vigilance would modulate phase-amplitude coupling. In the VL analysis we estimated the coupling of the phases of 3 low frequencies (α1, α2, and β1), respectively, with the amplitude of high-frequency oscillations (30-40 Hz, low γ). With rPDC we found that during the EC condition, nicotine decreased feedback connectivity (from the precentral gyrus to precuneus, angular gyrus, cuneus and superior occipital gyrus) at 10.5-12.4 Hz. The VL analysis showed nicotine-induced increases in coupling at 10.5-18.4 Hz in the precuneus, cuneus and superior occipital gyrus during the EC condition. During the EO condition, no significant results were found in connectivity or phase-amplitude coupling measures at any frequency range. In conclusion, the results suggest that nicotine potentially increases the level of vigilance in the EC condition.

EEG Source Reconstruction in Male Nonsmokers after Nicotine Administration during the Resting State

Modern psychopharmacological research in humans focuses on how specific psychoactive molecules modulate oscillatory brain activity. We present state-of-the-art EEG methods applied in a resting-state drug study. Thirty healthy male nonsmokers were randomly allocated either to a nicotine group (14 subjects, 7 mg transdermal nicotine) or a placebo group (16 subjects). EEG activity was recorded in eyes-open (EO) and eyes-closed (EC) conditions before and after drug administration. A source reconstruction (minimum norm algorithm) analysis was conducted within a frequency range of 8.5-18.4 Hz subdivided into three different frequency bands. During EO, nicotine reduced the power of oscillatory activity in the 12.5- to 18.4-Hz frequency band in the left middle frontal gyrus. In contrast, in the EC condition, nicotine reduced the power in the 8.5- to 10.4-Hz frequency band in the superior frontal gyri and in the 10.5- to 12.4-Hz and 12.5- to 18.4-Hz frequency bands in the supplementary motor areas. In summary, nicotine reduced the power of the 12.5- to 18.4-Hz band in the left middle frontal gyrus during EO, and it reduced power from 8.5 to 18.4 Hz in a brain area spanning from the superior frontal gyri to the supplementary motor areas during EC. In conclusion, the results suggest that nicotine counteracts the phenomenon of anteriorization of α activity, hence potentially increasing the level of vigilance.

Nicotine-induced cortical activation among nonsmokers with moderation by trait cognitive control

RATIONALE

Considerable research suggests that nicotine enhances cognitive control-related processes (e.g., attention, memory) among nicotine-deprived smokers, both in terms of behavior and neural indices (e.g., ERP, slow-wave EEG). Nicotine may also increase cognitive control among nonsmokers, and this may vary as a function of trait cognitive control. It is important to examine the effects of nicotine on cognitive control-related processes among nonsmokers as these effects may provide a path for the initiation of smoking.

OBJECTIVES

The objectives of the study were to examine in nonsmokers (1) the effect of nicotine on resting cortical activity, an indirect measure of cognitive control, and (2) trait cognitive control as a moderator of nicotine-induced cortical activity changes.

METHOD

Eighty participants were given placebo and 7-mg nicotine patches in separate sessions for this counter-balanced, double-blind, within-subject study. Resting cortical activity was measured with EEG for a 3-min period with eyes opened.

RESULTS

Average alpha-1 band power density values in frontal and central regions were lower during the nicotine versus placebo condition, which provides evidence of nicotine-induced cortical activation. Furthermore, those with lower self-reported cognitive control exhibited greater nicotine-induced reductions in alpha-1 power density values.

CONCLUSIONS

These individual differences in nicotine-induced cortical activation are consistent with a model of nicotine self-medication whereby individuals with lower cognitive control may find smoking more reinforcing via amelioration of related cognitive deficits.

The separate and combined effects of monoamine oxidase A inhibition and nicotine on resting state EEG

While nicotine is often associated with the neuropsychological effects of tobacco smoke, the robust monoamine oxidase (MAO) inhibition observed in chronic smokers is also likely to play a role. Electroencephalographically-indexed alterations in baseline neural oscillations by nicotine have previously been reported in both smokers and non-smokers, however, little is known about the effects of MAO inhibition in combination with nicotine on resting state EEG. In a sample of 24 healthy non-smoking males, the effects of 6 mg nicotine gum, as well as MAO-A inhibition via 75 mg moclobemide, were investigated in separate and combined conditions over four separate test sessions. Drug effects were observed in the alpha2, beta2, and theta band frequencies. Nicotine increased alpha2 power, and moclobemide decreased beta2 power. Theta power was decreased most robustly by the combination of both drugs. Therefore, this study demonstrated that the nicotinic and MAO inhibiting properties of tobacco may differentially influence fast-wave oscillations (alpha2 and beta2), while acting in synergy to influence theta oscillations.

Resting-state EEG, impulsiveness, and personality in daily and nondaily smokers

OBJECTIVES

Resting EEG is sensitive to transient, acute effects of nicotine administration and abstinence, but the chronic effects of smoking on EEG are poorly characterized. This study measures the resting EEG profile of chronic smokers in a non-deprived, non-peak state to test whether differences in smoking behavior and personality traits affect pharmaco-EEG response.

METHODS

Resting EEG, impulsiveness, and personality measures were collected from daily smokers (n=22), nondaily smokers (n=31), and non-smokers (n=30).

RESULTS

Daily smokers had reduced resting delta and alpha EEG power and higher impulsiveness (Barratt Impulsiveness Scale) compared to nondaily smokers and non-smokers. Both daily and nondaily smokers discounted delayed rewards more steeply, reported lower conscientiousness (NEO-FFI), and reported greater disinhibition and experience seeking (Sensation Seeking Scale) than non-smokers. Nondaily smokers reported greater sensory hedonia than nonsmokers.

CONCLUSIONS

Altered resting EEG power in daily smokers demonstrates differences in neural signaling that correlated with greater smoking behavior and dependence. Although nondaily smokers share some characteristics with daily smokers that may predict smoking initiation and maintenance, they differ on measures of impulsiveness and resting EEG power.

SIGNIFICANCE

Resting EEG in non-deprived chronic smokers provides a standard for comparison to peak and trough nicotine states and may serve as a biomarker for nicotine dependence, relapse risk, and recovery.

COMT polymorphism modulates the resting-state EEG alpha oscillatory response to acute nicotine in male non-smokers

Performance improvements in cognitive tasks requiring executive functions are evident with nicotinic acetylcholine receptor (nAChR) agonists, and activation of the underlying neural circuitry supporting these cognitive effects is thought to involve dopamine neurotransmission. As individual difference in response to nicotine may be related to a functional polymorphism in the gene encoding catechol-O-methyltransferase (COMT), an enzyme that strongly influences cortical dopamine metabolism, this study examined the modulatory effects of the COMT Val158Met polymorphism on the neural response to acute nicotine as measured with resting-state electroencephalographic (EEG) oscillations. In a sample of 62 healthy non-smoking adult males, a single dose (6 mg) of nicotine gum administered in a randomized, double-blind, placebo-controlled design was shown to affect α oscillatory activity, increasing power of upper α oscillations in frontocentral regions of Met/Met homozygotes and in parietal/occipital regions of Val/Met heterozygotes. Peak α frequency was also found to be faster with nicotine (vs. placebo) treatment in Val/Met heterozygotes, who exhibited a slower α frequency compared to Val/Val homozygotes. The data tentatively suggest that interindividual differences in brain α oscillations and their response to nicotinic agonist treatment are influenced by genetic mechanisms involving COMT.

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.

Nicotine facilitates memory consolidation in perceptual learning

Perceptual learning is a special type of non-declarative learning that involves experience-dependent plasticity in sensory cortices. The cholinergic system is known to modulate declarative learning. In particular, reduced levels or efficacy of the neurotransmitter acetylcholine were found to facilitate declarative memory consolidation. However, little is known about the role of the cholinergic system in memory consolidation of non-declarative learning. Here we compared two groups of non-smoking men who learned a visual texture discrimination task (TDT). One group received chewing tobacco containing nicotine for 1 h directly following the TDT training. The other group received a similar tasting control substance without nicotine. Electroencephalographic recordings during substance consumption showed reduced alpha activity and P300 latencies in the nicotine group compared to the control group. When re-tested on the TDT the following day, both groups responded more accurately and more rapidly than during training. These improvements were specific to the retinal location and orientation of the texture elements of the TDT suggesting that learning involved early visual cortex. A group comparison showed that learning effects were more pronounced in the nicotine group than in the control group. These findings suggest that oral consumption of nicotine enhances the efficacy of nicotinic acetylcholine receptors. Our findings further suggest that enhanced efficacy of the cholinergic system facilitates memory consolidation in perceptual learning (and possibly other types of non-declarative learning). In that regard acetylcholine seems to affect consolidation processes in perceptual learning in a different manner than in declarative learning. Alternatively, our findings might reflect dose-dependent cholinergic modulation of memory consolidation. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

Cholinergic receptor subtypes and their role in cognition, emotion, and vigilance control: an overview of preclinical and clinical findings

RATIONALE

The cholinergic system has long been linked to cognitive processes. Two main classes of acetylcholine (ACh) receptors exist in the human brain, namely muscarinic and nicotinic receptors, of which several subtypes occur.

OBJECTIVES

This review seeks to provide an overview of previous findings on the influence of cholinergic receptor manipulations on cognition in animals and humans, with particular emphasis on the role of selected cholinergic receptor subtypes. Furthermore, the involvement of these receptor subtypes in the regulation of emotion and brain electrical activity as measured by electroencephalography (EEG) shall be addressed since these domains are considered to be important modulators of cognitive functioning.

RESULTS

In regard to cognition, the muscarinic receptor subtypes have been implicated mainly in memory functions, but have also been linked to attentional processes. The nicotinic α7 receptor subtype is involved in working memory, whereas the α4β2* subtype has been linked to tests of attention. Both muscarinic and nicotinic cholinergic mechanisms play a role in modulating brain electrical activity. Nicotinic receptors have been strongly associated with the modulation of depression and anxiety.

CONCLUSIONS

Cholinergic receptor manipulations have an effect on cognition, emotion, and brain electrical activity as measured by EEG. Changes in cognition can result from direct cholinergic receptor manipulation or from cholinergically induced changes in vigilance or affective state.

Tobacco smoking produces widespread dominant brain wave alpha frequency increases

The major pharmacological ingredient in tobacco smoke is nicotine, a mild stimulant known to alter brain electrical activity. The objective of this study was to determine if tobacco smoking in humans produces localized or widespread neocortical dominant alpha electroencephalographic (EEG) frequency increases consistent with nicotine stimulation of the brainstem activating system in animals. Twenty-two male volunteer non-deprived tobacco smokers were studied. They were asked not to smoke for at least 1h before the experiment in mid-morning as part of their usual smoking schedule. In the laboratory, they sham smoked and then smoked their favorite tobacco cigarette. Two experimental sessions (#1 and #2) were conducted, separated by a one to two month interval. In both sessions, there were minor statistically significant increases in the dominant alpha frequencies after sham smoking. In both sessions, after the subjects smoked a favorite tobacco cigarette there was a significant generalized increase in dominant alpha EEG frequencies in most scalp recording sites. This study demonstrates that tobacco smoking produces widespread bilateral neocortical increases in dominant alpha EEG frequencies consistent with the stimulant effects of nicotine on the brainstem reticular activating system.

Effects of TC-1734 (AZD3480), a selective neuronal nicotinic receptor agonist, on cognitive performance and the EEG of young healthy male volunteers

OBJECTIVES

The aim of this study was to get insight into the central effects of TC-1734 (renamed AZD3480), a selective agonist at the neuronal nicotinic receptor of the alpha4beta2 subtype.

MATERIALS AND METHODS

Electroencephalography (EEG) techniques and computerized cognitive tests were performed in young, healthy male volunteers during two double-blind and placebo-controlled studies: a rising single dose crossover study (from 2 to 320 mg) and a rising repeated dose study with a parallel group design (50, 100, and 200 mg).

RESULTS

In contrast to acute administration, administration of AZD3480 over 10 days produced statistically significant enhancement of several cognitive measures (attention and episodic memory) compared to placebo. Regarding EEG data, AZD3480 showed acceleration of the alpha centroid and of the alpha peak in the single-dose study. This EEG profile of the acceleration type was confirmed in the repeated dose study on both day 1 and day 10, with the greatest effect observed with the highest dose. The EEG pattern shown for AZD3480 was consistent with that previously described with other drugs known to improve attention and vigilance (including nicotine). In addition, subjects dosed with AZD3480 showed a statistically significant increase in mismatch negativity (MMN) amplitude at 50 and 200 mg while reducing MMN latency (200 mg only), suggesting an improvement of pre-attentional mechanisms.

CONCLUSION

These early data in healthy subjects provide encouragement to consider development of AZD3480 as a novel agent for the treatment of cognitive decline in the elderly, including age-associated memory impairment and/or dementia of the Alzheimer's type.

Nicotinic modulation of neuronal networks: from receptors to cognition

RATIONALE

Nicotine affects many aspects of human cognition, including attention and memory. Activation of nicotinic acetylcholine receptors (nAChRs) in neuronal networks modulates activity and information processing during cognitive tasks, which can be observed in electroencephalograms (EEGs) and functional magnetic resonance imaging studies.

OBJECTIVES

In this review, we will address aspects of nAChR functioning as well as synaptic and cellular modulation important for nicotinic impact on neuronal networks that ultimately underlie its effects on cognition. Although we will focus on general mechanisms, an emphasis will be put on attention behavior and nicotinic modulation of prefrontal cortex. In addition, we will discuss how nicotinic effects at the neuronal level could be related to its effects on the cognitive level through the study of electrical oscillations as observed in EEGs and brain slices.

RESULTS/CONCLUSIONS

Very little is known about mechanisms of how nAChR activation leads to a modification of electrical oscillation frequencies in EEGs. The results of studies using pharmacological interventions and transgenic animals implicate some nAChR types in aspects of cognition, but neuronal mechanisms are only poorly understood. We are only beginning to understand how nAChR distribution in neuronal networks impacts network functioning. Unveiling receptor and neuronal mechanisms important for nicotinic modulation of cognition will be instrumental for treatments of human disorders in which cholinergic signaling have been implicated, such as schizophrenia, attention deficit/hyperactivity disorder, and addiction.

Psychobiological Theories of Smoking and Smoking Motivation

Abstract. Theories of smoking have been developed about the conditions and causes of smoking as well as for explaining its maintenance. Moreover, factors of smoking motivation have been identified, which describe incentives to smoke and types of smoking behavior. The most frequently reported motives are psychosocial smoking, sensorimotor smoking, indulgent smoking, stimulation smoking, sedation smoking, dependent smoking, and automatic smoking. In the first phase after the start of smoking, psychosocial smoking is the dominating motive, which is best represented by theories of social psychology. Sensorimotor smoking may be best explained by theories of classical and operant conditioning. Indulgent smoking (= smoking for pleasure) may be explained by neurochemical theories and by the neurobiological theories of dependence emphasizing nicotine-induced activation of mesolimbic dopaminergic reinforcement. Stimulation smoking and sedation smoking are related to arousal models. Moreover, sedation smoking is also explained by aspects of reducing negative affect (as claimed by theories of affect regulation) and by biochemical theories emphasizing serotonergic mechanisms in modulating anxiety as well as by theories of dependence. Dependent smoking, which is mostly based on negative reinforcement (suppression of withdrawal symptoms) may be explained by neurochemical theories as well as by neurobiological theories of psychological and physical dependence explaining blunted dopaminergic and serotonergic responsivity as due to desensitization of respective receptors. Also automatic smoking may be explained by processes of habit learning and neurobiological theories of dependence. Finally, personality theories have been applied to all of these smoking motives.

EEG power spectra and auditory P300 during free smoking and enforced smoking abstinence

We investigated resting EEG and auditory P300 during free smoking and 36 h of enforced smoking abstinence in 12 healthy volunteers. Resting EEG was recorded on 19 scalp leads and auditory P300 was obtained by an oddball paradigm task. Spectral analysis of EEG (absolute and relative power, mean frequency), latency and amplitude of auditory P300 were considered for statistical analysis. EEG changes were not significant during free smoking but were significant during smoking abstinence. Theta absolute power increased by +57% (P<.001), whereas alpha and delta absolute power increased by +26% (P<.01) and +19% (P<.01), respectively; theta absolute power change was delayed and prolonged. Alpha mean frequency reduced by -0.31 Hz (P<.001), whereas delta, theta and beta1 mean frequency increased by +0.13 Hz (P<.05), +0.09 Hz (P<.05) and +0.23 Hz (P<.01), respectively. Auditory P300 amplitude and latency were unaffected by smoking abstinence. Resting EEG, but not auditory P300, was sufficiently sensitive to detect changes during enforced smoking abstinence, and EEG bands had different temporal changes.

The effects of nicotine on the 13 Hz steady-state visually evoked potential

OBJECTIVES

The high alpha/low beta range of the spontaneous EEG appears to be particularly sensitive to the effects of nicotine. The present study examined the acute effects of nicotine on the topography of the 13 Hz steady-state visually evoked potential (SSVEP).

METHODS

Thirteen moderate smokers participated in a repeated-measures design. The amplitude and latency of the SSVEP elicited by an unstructured sinusoidal 13 Hz flicker following a <0. 05 mg nicotine cigarette were compared to those following a 0.8 mg nicotine cigarette.

RESULTS

The nicotine condition was associated with an increase in the amplitude of the SSVEP, when compared to the placebo condition, and this increase was greatest in central and right parietal regions. The latency of the SSVEP was reduced in the nicotine condition in bilateral frontal and right parietal regions.

CONCLUSIONS

These results are similar to the effects of nicotine seen in studies examining spontaneous EEG, and are consistent with other studies indicating that the 13 Hz SSVEP indexes brain electrical activity in the high alpha/low beta range. The findings are discussed in terms of possible functional significance of nicotine-induced cortical activation in this frequency range.

Direct and indirect effects of nicotine/smoking on cognition in humans

Acute nicotine administration and acute nicotine withdrawal have been shown to have effects on mood, arousal, and cognition in humans. However, given what is known about the interrelationships between mood, arousal, and cognition in the psychology literature, it is unclear to what extent these effects on a given response are direct, or mediated through other responses (indirect). This article discusses this issue with particular emphasis on the question of whether nicotine has direct effects on cognition. Five ways are suggested as to how this question can be resolved, the relevant literature is reviewed, and some research ideas are proposed.

Effect of haloperidol on nicotine-induced enhancement of vigilance in human subjects

We posed the question whether the cognitive enhancement caused by nicotine in human subjects is mediated by dopamine (DA) release. This issue was addressed by testing performance in the Wesnes and Warburton vigilance task after s.c. nicotine with or without concomitant oral haloperidol. The subjects were moderate (10-14 cigarettes/day) smokers after overnight deprivation of smoking. After an initial practice session, each subject participated in four further sessions spread over 2 weeks, after: placebo/placebo, placebo/haloperidol (5 mg), placebo/nicotine (0.8 mg) or nicotine/haloperidol, double-blind with a balanced ordering of drug combinations. On each occasion, performance was measured on the vigilance task, a finger tapping test, and digit span forward and backward. Nicotine improved detection sensitivity on the vigilance task, and this effect was unchanged by haloperidol; the latter compound reduced forward digit span. Thus, the improved vigilance caused by nicotine does not appear to be mediated by DA systems.

Cognitive performance effects of subcutaneous nicotine in smokers and never-smokers

In a double-blind placebo-controlled crossover study the effects of two doses of subcutaneous nicotine and saline were compared on a range of performance measures in 18 abstaining smokers and 18 never-smokers. Each subject received two injections (40 min apart) of saline, 0.3 mg nicotine, or 0.6 mg nicotine in a balanced order over three sessions. Performance was assessed before and after the injections on nine tests [news recall, Sternberg memory task, finger tapping, logical reasoning, rapid visual information processing (RVIP), long-term word recognition, digit recall, Stroop test, and critical flicker fusion threshold]. In the abstinent smokers, nicotine produced significantly faster correct responses on the logical reasoning test, more target hits, faster reaction times and improved sensitivity on the RVIP task, and more correct responses on word recognition. In never-smokers, nicotine produced faster reaction times on the RVIP and digit-recall tasks, although in the latter case this was at the expense of fewer correct responses. There were no significant differences between the two groups' responses to nicotine but smokers performed worse than never-smokers prior to injections, even controlling for background characteristics. These results are consistent with other recent research suggesting a primary effect of nicotine in enhancing cognitive performance.

The role of nicotine in tobacco smoking: implications for tobacco control policy

This paper outlines some of the evidence that tobacco smoking is maintained by addiction to nicotine. Smokers often perceive that tobacco helps them cope with stress and aids their mental alertness. Nicotine withdrawal symptoms are one important factor preventing many smoker from quitting (only about 3% succeed with each unaided quit attempt). A number of policies are suggested to reduce the health consequences of smoking more quickly than at present. These include (a) banning all tobacco advertising and prosecuting retailers who sell illegally to children, in order to reduce the number of young people becoming addicted, (b) increasing the real price of tobacco in order to encourage more people to try to stop smoking, (c) providing specialist smokers' clinics in every large general hospital in order to assist highly motivated but addicted smokers to quit and (d) increasing the rate at which tobacco manufacturers must reduce permissible tar and carbon monoxide yields, such that in 20 years time only nicotine delivery products which are free of tar and carbon monoxide will be allowed.