Individual variability in responses to nicotine

An α7 nAChR approach for the baseline-dependent modulation of deviance detection in schizophrenia: A pilot study assessing the combined effect of CDP-choline and galantamine

BACKGROUND

Cognitive operations including pre-attentive sensory processing are markedly impaired in patients with schizophrenia (SCZ) but evidence significant interindividual heterogeneity, which moderates treatment response with nicotinic acetylcholine receptor (nAChR) agonists. Previous studies in healthy volunteers have shown baseline-dependency effects of the α7 nAChR agonist cytidine 5'-diphosphocholine (CDP-choline) administered alone and in combination with a nicotinic allosteric modulator (galantamine) on auditory deviance detection measured with the mismatch negativity (MMN) event-related potential (ERP).

AIM

The objective of this pilot study was to assess the acute effect of this combined α7 nAChR-targeted treatment (CDP-choline/galantamine) on speech MMN in patients with SCZ (N = 24) stratified by baseline MMN responses into low, medium, and high baseline auditory deviance detection subgroups.

METHODS

Patients with a stable diagnosis of SCZ attended two randomized, double-blind, placebo-controlled and counter-balanced testing sessions where they received a placebo or a CDP-choline (500 mg) and galantamine (16 mg) treatment. MMN ERPs were recorded during the presentation of a fast multi-feature speech MMN paradigm including five speech deviants. Clinical measures were acquired before and after treatment administration.

RESULTS

While no main treatment effect was observed, CDP-choline/galantamine significantly increased MMN amplitudes to frequency, duration, and vowel speech deviants in low group individuals. Individuals with higher positive and negative symptom scale negative, general, and total scores expressed the greatest MMN amplitude improvement following CDP-choline/galantamine.

CONCLUSIONS

These baseline-dependent nicotinic effects on early auditory information processing warrant different dosage and repeated administration assessments in patients with low baseline deviance detection levels.

The modulating impact of cigarette smoking on brain structure in panic disorder: a voxel-based morphometry study

Cigarette smoking increases the likelihood of developing anxiety disorders, among them panic disorder (PD). While brain structures altered by smoking partly overlap with morphological changes identified in PD, the modulating impact of smoking as a potential confounder on structural alterations in PD has not yet been addressed. In total, 143 PD patients (71 smokers) and 178 healthy controls (62 smokers) participated in a multicenter magnetic resonance imaging (MRI) study. T1-weighted images were used to examine brain structural alterations using voxel-based morphometry in a priori defined regions of the defensive system network. PD was associated with gray matter volume reductions in the amygdala and hippocampus. This difference was driven by non-smokers and absent in smoking subjects. Bilateral amygdala volumes were reduced with increasing health burden (neither PD nor smoking > either PD or smoking > both PD and smoking). As smoking can narrow or diminish commonly observed structural abnormalities in PD, the effect of smoking should be considered in MRI studies focusing on patients with pathological forms of fear and anxiety. Future studies are needed to determine if smoking may increase the risk for subsequent psychopathology via brain functional or structural alterations.

CDP-choline and galantamine, a personalized α7 nicotinic acetylcholine receptor targeted treatment for the modulation of speech MMN indexed deviance detection in healthy volunteers: a pilot study

RATIONALE

The combination of CDP-choline, an α7 nicotinic acetylcholine receptor (α7 nAChR) agonist, with galantamine, a positive allosteric modulator of nAChRs, is believed to counter the fast desensitization rate of the α7 nAChRs and may be of interest for schizophrenia (SCZ) patients. Beyond the positive and negative clinical symptoms, deficits in early auditory prediction-error processes are also observed in SCZ. Regularity violations activate these mechanisms that are indexed by electroencephalography-derived mismatch negativity (MMN) event-related potentials (ERPs) in response to auditory deviance.

OBJECTIVES/METHODS

This pilot study in thirty-three healthy humans assessed the effects of an optimized α7 nAChR strategy combining CDP-choline (500 mg) with galantamine (16 mg) on speech-elicited MMN amplitude and latency measures. The randomized, double-blinded, placebo-controlled, and counterbalanced design with a baseline stratification method allowed for assessment of individual response differences.

RESULTS

Increases in MMN generation mediated by the acute CDP-choline/galantamine treatment in individuals with low baseline MMN amplitude for frequency, intensity, duration, and vowel deviants were revealed.

CONCLUSIONS

These results, observed primarily at temporal recording sites overlying the auditory cortex, implicate α7 nAChRs in the enhancement of speech deviance detection and warrant further examination with respect to dysfunctional auditory deviance processing in individuals with SCZ.

Sex differences in nicotine preference

Smoking is the major cause of preventable deaths worldwide, and although there is a decline in overall smoking prevalence in developed countries, the decline in women is less pronounced than in men. Women become dependent faster and experience greater difficulties in quitting. Similar trends have been observed in animal models of nicotine/tobacco addiction. Individual differences in vulnerability to drug abuse are also observed in nicotine/tobacco addiction and point to the importance of sex differences. This Review, summarizes findings from three experimental approaches used to depict nicotine preference in animal models, intravenous and oral nicotine self-administration and nicotine-induced conditioned place preference. Nicotine preference is considered to be reflected in the animal's motivation to administer the drug (intravenously or orally) or to prefer an environment paired with the presence of the drug (conditioned place preference). These approaches all point to the importance of sex and age of the subjects; the preference of females and adolescents appear to be more pronounced than that of males and adults, respectively. A closer look at these factors will help us understand the mechanisms that underlie nicotine addiction and develop strategies to cope. Ignoring sex differences and reaching conclusions based only on studies using male subjects has resulted in erroneous generalizations in the past. Sex differences in nicotine preference have been clearly documented, and awareness on this aspect of nicotine dependence will significantly impact our success in translational research. © 2016 Wiley Periodicals, Inc.

Intravenous Nicotine Self-Administration in Smokers: Dose-Response Function and Sex Differences

Sex differences in the sensitivity to nicotine may influence vulnerability to tobacco dependence. The goal of this study was to investigate the dose-response function for the reinforcing and subjective effects of intravenous nicotine in male and female smokers. Tobacco-dependent subjects (12 male and 14 female) participated in four experimental sessions in which they received sample infusions of saline and nicotine (0.1, 0.2, 0.3, or 0.4 mg doses) in a randomized double-blind crossover design. During each session, subjects first received the sample infusions, and heart rate (HR), blood pressure, and subjective stimulatory, pleasurable and aversive responses were monitored. Immediately following the sample infusions, subjects self-administered either nicotine or saline in six double-blind forced-choice trials. A sex by dose interaction was observed in the nicotine choice paradigm. Nicotine self-administration rate was negatively correlated with nicotine dose in males (males displayed choice preference for low doses of nicotine over high doses of nicotine), but no significant relationship between dose and choice preference was evident in females. Relative to placebo, sample doses of nicotine increased heart rate and blood pressure, and induced stimulatory, pleasurable, and aversive subjective effects. Diastolic blood pressure increased dose dependently in males, but not in females. These findings, which demonstrate sex differences in nicotine self-administration for doses that are near to the reinforcement threshold, suggest that male and female smokers may respond differently to the changes in nicotine doses available for self-administration.

Modeling naturalistic craving, withdrawal, and affect during early nicotine abstinence: A pilot ecological momentary assessment study

Despite the critical role of withdrawal, craving, and positive affect (PA) and negative affect (NA) in smoking relapse, relatively little is known about the temporal and predictive relationship between these constructs within the first day of abstinence. This pilot study aims to characterize dynamic changes in withdrawal, craving, and affect over the course of early abstinence using ecological momentary assessment. Beginning immediately after smoking, moderate and heavy smoking participants (n = 15 per group) responded to hourly surveys assessing craving, withdrawal, NA, and PA. Univariate and multivariate multilevel random coefficient modeling was used to describe the progression of craving, withdrawal/NA, and PA and to test correlations between these constructs at the subject level over the course of early abstinence. Heavy smokers reported greater craving from 1-4 hr of abstinence and greater withdrawal/NA after 3 or more hours as compared with moderate smokers. Level of withdrawal/NA was strongly positively associated with craving, and PA was negatively correlated with craving; however, the temporal dynamics of these correlations differed substantially. The association between withdrawal/NA and craving decreased over early abstinence, whereas the reverse was observed for PA. These findings can inform experimental studies of nicotine abstinence as well as their clinical applications to smoking cessation efforts. In particular, these results help to elucidate the role of PA in nicotine abstinence by demonstrating its independent association with nicotine craving over and above withdrawal/NA. If supported by future studies, these findings can refine experimental methods and clinical approaches for smoking cessation.

Dopamine receptor blockade modulates the rewarding and aversive properties of nicotine via dissociable neuronal activity patterns in the nucleus accumbens

The mesolimbic pathway comprising the ventral tegmental area (VTA) and projection terminals in the nucleus accumbens (NAc) has been identified as a critical neural system involved in processing both the rewarding and aversive behavioral effects of nicotine. Transmission through dopamine (DA) receptors functionally modulates these effects directly within the NAc. Nevertheless, the neuronal mechanisms within the NAc responsible for these bivalent behavioral effects are presently not known. Using an unbiased conditioned place preference procedure combined with in vivo neuronal recordings, we examined the effects of nicotine reward and aversion conditioning on intra-NAc neuronal sub-population activity patterns. We report that intra-VTA doses of nicotine that differentially produce rewarding or aversive behavioral effects produce opposite effects on sub-populations of fast-spiking interneurons (FSIs) or medium spiny neurons (MSNs) within the shell region of the NAc (NAshell). Thus, while the rewarding effects of intra-VTA nicotine were associated with inhibition of FSI and activation of MSNs, the aversive effects of nicotine produced the opposite pattern of NAshell neuronal population activity. Blockade of DA transmission with a broad-spectrum DA receptor antagonist, α-flupenthixol, strongly inhibited the spontaneous activity of NAshell FSIs, and reversed the conditioning properties of intra-VTA nicotine, switching nicotine-conditioned responses from aversive to rewarding. Remarkably, DA receptor blockade switched intra-NAshell neuronal population activity from an aversion to a reward pattern, concomitant with the observed switch in behavioral conditioning effects.

Modulation of auditory deviance detection by acute nicotine is baseline and deviant dependent in healthy nonsmokers: a mismatch negativity study

OBJECTIVE

Cognitive enhancement resulting from nicotinic acetylcholine receptor stimulation may be evidenced by increased efficiency of the auditory-frontal cortex network of auditory discrimination, which is impaired in schizophrenia, a cognitive disorder associated with excessive tobacco use. Investigating automatic (preattentive) detection of acoustic change with the mismatch negativity (MMN) brain event-related potential in response to nicotine in individuals with varying baseline levels of auditory discrimination may provide useful insight into the cholinergic regulation of this neural network and its potential amelioration with novel nicotinic agents.

METHODS

Sixty healthy, non-smoking male volunteers were presented with an 'optimal' multi-feature MMN paradigm in a randomized, placebo controlled double-blind design with 6 mg of nicotine gum.

RESULTS

Participants with low, medium, and high baseline amplitudes responded differently to nicotine (vs. placebo), and nicotine response was feature specific. Whereas MMN in individuals with high amplitudes was diminished by nicotine, MMN increased in those with low amplitudes. Nicotine effects were not shown in medium amplitude participants.

CONCLUSIONS

These findings provide preliminary support for the role of nicotinic neurotransmission in sensory memory processing of auditory change and suggest that nicotinic receptor modulation can both enhance and diminish change detection, depending on baseline MMN and its eliciting stimulus feature.

The impact of smoking in adolescence on early adult anxiety symptoms and the relationship between infant vulnerability factors for anxiety and early adult anxiety symptoms: the TOPP Study

Cigarette smoking is increased in people with trait anxiety and anxiety disorders, however no longitudinal data exist illuminating whether smoking in adolescence can influence the developmental trajectory of anxiety symptoms from early vulnerability in infancy to adult anxiety expression. Using The Tracing Opportunities and Problems in Childhood and Adolescence (TOPP) Study, a community-based cohort of children and adolescents from Norway who were observed from the age of 18 months to age 18-19 years, we explored the relationship between adolescent smoking, early vulnerability for anxiety in infancy (e.g. shyness, internalizing behaviors, emotional temperaments) and reported early adult anxiety. Structural equation modeling demonstrated that adolescent active smoking was positively associated with increased early adulthood anxiety (β = 0.17, p<0.05), after controlling for maternal education (proxy for socioeconomic status). Adolescent anxiety did not predict early adult smoking. Adolescent active smoking was a significant effect modifier in the relationship between some infant vulnerability factors and later anxiety; smoking during adolescence moderated the relationship between infant internalizing behaviors (total sample: active smokers: β = 0.85, p<0.01, non-active smokers: ns) and highly emotional temperament (total sample: active smokers: β = 0.55, p<0.01,non-active smokers: ns), but not shyness, and anxiety in early adulthood. The results support a model where smoking acts as an exogenous risk factor in the development of anxiety, and smoking may alter the developmental trajectory of anxiety from infant vulnerability to early adult anxiety symptom expression. Although alternative non-mutually exclusive models may explain these findings, the results suggest that adolescent smoking may be a risk factor for adult anxiety, potentially by influencing anxiety developmental trajectories. Given the known adverse health effects of cigarette smoking and significant health burden imposed by anxiety disorders, this study supports the importance of smoking prevention and cessation programs targeting children and adolescence.

Cigarette smoking, nicotine dependence and anxiety disorders: a systematic review of population-based, epidemiological studies

BACKGROUND

Multiple studies have demonstrated that rates of smoking and nicotine dependence are increased in individuals with anxiety disorders. However, significant variability exists in the epidemiological literature exploring this relationship, including study design (cross-sectional versus prospective), the population assessed (random sample versus clinical population) and diagnostic instrument utilized.

METHODS

We undertook a systematic review of population-based observational studies that utilized recognized structured clinical diagnostic criteria (Diagnostic and Statistical Manual of Mental Disorders (DSM) or International Classification of Diseases (ICD)) for anxiety disorder diagnosis to investigate the relationship between cigarette smoking, nicotine dependence and anxiety disorders.

RESULTS

In total, 47 studies met the predefined inclusion criteria, with 12 studies providing prospective information and 5 studies providing quasiprospective information. The available evidence suggests that some baseline anxiety disorders are a risk factor for initiation of smoking and nicotine dependence, although the evidence is heterogeneous and many studies did not control for the effect of comorbid substance use disorders. The identified evidence however appeared to more consistently support cigarette smoking and nicotine dependence as being a risk factor for development of some anxiety disorders (for example, panic disorder, generalized anxiety disorder), although these findings were not replicated in all studies. A number of inconsistencies in the literature were identified.

CONCLUSIONS

Although many studies have demonstrated increased rates of smoking and nicotine dependence in individuals with anxiety disorders, there is a limited and heterogeneous literature that has prospectively examined this relationship in population studies using validated diagnostic criteria. The most consistent evidence supports smoking and nicotine dependence as increasing the risk of panic disorder and generalized anxiety disorder. The literature assessing anxiety disorders increasing smoking and nicotine dependence is inconsistent. Potential issues with the current literature are discussed and directions for future research are suggested.

Individual differences in oral nicotine intake in rats

To study individual differences in nicotine preference and intake, male and female rats were given free access to a choice of oral nicotine (10 or 20 mg/L) or water for 24 h/day for periods of at least six weeks, starting at adolescence or adulthood. A total of 341 rats, were used in four different experiments; weight, nicotine intake and total liquid consumption were recorded weekly. Results show that rats can discriminate nicotine from water, can regulate their intake, and that there are readily detected individual differences in nicotine preference. Ward analyses indicated that the animals could be divided into minimum, median and maximum preferring subgroups in all experiments. The effect of saccharine on nicotine intake was also evaluated; although the addition of saccharine increased total intake, rats drank unsweetened nicotine solutions and those with higher preferences for nicotine, preferred nicotine over water with or without saccharine added. Nicotine reduced weight gain and the effect was more pronounced in females than males. The average nicotine consumption of adolescent rats was higher than adults and nicotine exposure during adolescence reduced nicotine intake in adult rats. About half of the rats which had access to nicotine as adolescents and also as adults had a persistent pattern of consumption; the behavior was very stable in the female minimum preferring groups and a much higher ratio of rats sustained their adolescent behavior as adults. The change in preference was more pronounced when there was an interval between adolescent and adult exposure; female rats showed a more stable behavior than males suggesting a greater role for environmental influences on males. In conclusion, marked individual differences were observed in oral nicotine intake as measured in a continuous access 2-bottle choice test. Age and sex of the subjects and previous exposure to nicotine are significant factors which affect preference in rats.

Subjective effects of transdermal nicotine among nonsmokers

The subjective experience of nicotine, which may be influenced by personality traits as well as environmental factors, may be important for understanding the factors associated with the initiation and maintenance of nicotine dependence. The present study examined the effects of 7 mg transdermal nicotine among a relatively large sample (n = 91; 44 women) of college-aged nonsmokers. Using a placebo controlled, double-blind, within-subjects design, nicotine's effects were examined at rest and again after participants completed a sustained attention task. Sex and personality factors (Behavioral Inhibition and Behavioral Approach; BIS/BAS Scales; Carver & White, 1994) were examined as potential moderators. Overall, the effects of nicotine were generally modest and unpleasant. In the context of the cognitive task, nicotine increased nausea and negative affect but reduced fatigue, relative to placebo. In contrast, effects of nicotine during the initial 4 hr of patch administration, in which participants were in their natural environments, were moderated by individual differences in behavioral approach. Neither behavioral inhibition nor gender reliably moderated any subjective effects of nicotine. The present work suggests transdermal nicotine exerts only modest, mostly negative effects among nonsmokers. Future work should examine both contextual and personality moderators in large samples of participants who are exposed to nicotine through multiple routes of administration.

Biological evidence for the acute health effects of secondhand smoke exposure

A vast number of studies on the unfavorable effects of secondhand smoke (SHS) exist within the international literature, the majority of which evaluate longitudinal epidemiological data. Although limited, the experimental studies that assess the acute and short-term effects of exposure to SHS are also increasing in number. They include cellular, animal, and human studies that indicate a number of pathophysiological mechanisms through which the deleterious effects of SHS may arise. This current review evaluates the existing biological evidence regarding the acute health effects of SHS exposure. Analyses on the inhaled toxicants and the carcinogenicity of SHS are included as well as in-depth discussions on the evidence for acute SHS-induced respiratory, cardiovascular, metabolic, endocrine and immune effects, and SHS-induced influences on oxygen delivery and exercise. The influence of the length of exposure and the duration of the observed effects is also described. Moreover, recent findings regarding the underlying pathophysiological mechanisms related to SHS are depicted so as to generate models that describe the SHS-induced effects on different systems within the human body. Based on the presented biological evidence, it is concluded that brief, acute, transient exposures to SHS may cause significant adverse effects on several systems of the human body and represent a significant and acute health hazard. Future research directions in this area include research on the concentrations of tobacco smoke constituents in the alveolar milieu following SHS exposure, individual susceptibility to SHS, as well as the effects of SHS on neurobehavioral activity, brain cell development, synaptic development, and function.

Abuse liability assessment of tobacco products including potential reduced exposure products

The harm produced by tobacco products is a result of frequent use of a highly toxic product. Reducing the adverse public health impact of tobacco products might be most effectively achieved by reducing the likelihood of their use and the toxicity of the products. Products that retain some characteristics of cigarettes but have been altered with the intention of reducing toxicity have been referred to as modified risk tobacco products or potential reduced exposure products (MRTP/PREP). Evaluation of their content, emission, and toxicity is discussed in other articles in this special issue. Here, we discuss the methodology that has been used to examine the likelihood of abuse or addiction. Abuse liability assessment (ALA) methodology has been used by the Food and Drug Administration (FDA) and other drug regulatory agencies world-wide for decades to assess the risks posed by a wide variety of pharmacologically active substances. ALA is routinely required among other evaluations of safety during the pre-market assessment of new drugs, and is continually adapted to meet the challenges posed by new drug classes and drug formulations. In the 2009 law giving FDA regulation over tobacco products, FDA is now required to evaluate new tobacco products including MRTP/PREPs to determine their risk for abuse and toxicity at the population level. This article describes the traditional tools and methods of ALA that can be used to evaluate new tobacco and nicotine products including MRTP/PREPs. Such ALA data could contribute to the scientific foundation on which future public policy decisions are based.

GABAA-benzodiazepine receptor availability in smokers and nonsmokers: relationship to subsyndromal anxiety and depression

Many smokers experience subsyndromal anxiety symptoms while smoking and during acute abstinence, which may contribute to relapse. We hypothesized that cortical gamma aminobutyric acid(A)-benzodiazepine receptor (GABA(A)-BZR) availability in smokers and nonsmokers might be related to the expression of subsyndromal anxiety, depressive, and pain symptoms. Cortical GABA(A)-BZRs were imaged in 15 smokers (8 men and 7 women), and 15 healthy age and sex-matched nonsmokers, and 4 abstinent tobacco smokers (3 men; 1 woman) using [(123)I]iomazenil and single photon emission computed tomography (SPECT). Anxiety and depressive symptoms were measured using the Spielberger's State-Trait Anxiety Index (STAI) and the Center for Epidemiology Scale for Depressive Symptoms (CES-D). The cold pressor task was administered to assess pain tolerance and sensitivity. The relationship between cortical GABA(A)-BZR availability, smoking status, and subsyndromal depression and anxiety symptoms, as well as pain tolerance and sensitivity, were evaluated. Surprisingly, there were no statistically significant differences in overall GABA(A)-BZR availability between smokers and nonsmokers or between active and abstinent smokers; however, cortical GABA(A)-BZR availability negatively correlated with subsyndromal state anxiety symptoms in nonsmokers but not in smokers. In nonsmokers, the correlation was seen across many brain areas with state anxiety [parietal (r = -0.47, P = 0.03), frontal (r = -0.46, P = 0.03), anterior cingulate (r = -0.47, P = 0.04), temporal (r = -0.47, P = 0.03), occipital (r = -0.43, P = 0.05) cortices, and cerebellum (r = -0.46, P = 0.04)], trait anxiety [parietal (r = -0.72, P = 0.02), frontal (r = -0.72, P = 0.02), and occipital (r = -0.65, P = 0.04) cortices] and depressive symptoms [parietal (r = -0.68; P = 0.02), frontal (r = -0.65; P = 0.03), anterior cingulate (r = -0.61; P = 0.04), and temporal (r = -0.66; P = 0.02) cortices]. The finding that a similar relationship between GABA(A)-BZR availability and anxiety symptoms was not observed in smokers suggests that there is a difference in GABA(A)-BZR function, but not number, in smokers. Thus, while subsyndromal anxiety and depressive symptoms in nonsmokers may be determined in part by GABA(A)-BZR availability, smoking disrupts this relationship. Aberrant regulation of GABA(A)-BZR function in vulnerable smokers may explain why some smokers experience subsyndromal anxiety and depression.

Alcohol-induced increases in smoking behavior for nicotinized and denicotinized cigarettes in men and women

INTRODUCTION

Alcohol has been shown to increase smoking urges and smoking behavior. However, alcohol's effects on specific components of smoking behavior for nicotine versus non-nicotine factors and potential sex differences in this response have not been investigated.

METHODS

Forty-two young male and female non-dependent, heavy social drinking smokers participated in two double-blind laboratory sessions. They were randomized to either an alcohol (0.8 g/kg; n = 29) or placebo (n = 13) beverage pre-administration group. After beverage consumption, they were assessed for smoking urges and then given the opportunity to smoke cigarettes which were either all nicotinized (0.6 mg/cigarette) or denicotinized (< or =0.05 mg/cigarette) over a 3-h period; smoking behavior was quantified by a smoking topography device. Subjects took standardized puffs of the session's cigarette both before and after beverage administration to provide a reference when making future smoking choices.

RESULTS

Alcohol, compared with placebo beverage, increased both men's and women's smoking urge, as well as subjective ratings of smoking reference puffs for either nicotinized or denicotinized cigarettes. In terms of smoking choice behavior, regardless of cigarette type, alcohol (>placebo) increased men's smoking behavior, including puff count, volume, and duration. In contrast, for women, smoking topography measures did not differ between alcohol and placebo conditions.

DISCUSSION

In summary regardless of nicotine content, in men, alcohol increased smoking urge and behavior, whereas in women, alcohol increased smoking urge but did not increase smoking behavior. These results indicate that the mechanisms underlying co-use of alcohol and tobacco in women may be more complex than in men.

Subjective responses to intravenous nicotine: greater sensitivity in women than in men

Although approximately 45% of smokers in the United States are women, the influence of sex on nicotine dependence remains incompletely understood. Evidence from preclinical and clinical studies has indicated that there are significant sex differences in nicotine's effects. The authors' goal in this report was to determine whether men and women differ in their acute response to intravenous nicotine, which has not been examined in previous studies. Twelve male and 12 female smokers received saline followed by 0.5 mg/70 kg and 1.0 mg /70 kg nicotine intravenously. In response to nicotine, women, as compared with men, had enhanced ratings for drug strength, head rush, and bad effects. Women and men experienced similar suppression of smoking urges by nicotine as assessed by the Brief Questionnaire on Smoking Urges. Nicotine-induced heart rate and systolic and diastolic blood pressure increases were also similar in magnitude in men and women. The findings, consistent with those of several previous studies, support greater sensitivity of female smokers to some but not all of the subjective effects of nicotine. Further studies are warranted to examine the role of this differential nicotine sensitivity to development of nicotine dependence and response to nicotine replacement treatments in men and women.

Sex differences in nicotine action

Accumulating evidence suggests that the antecedents, consequences, and mechanisms of drug abuse and dependence are not identical in males and females and that gender may be an important variable in treatment and prevention. Although there has been a decline in smoking prevalence in developed countries, females are less successful in quitting. Tobacco use is accepted to be a form of addiction, which manifests sex differences. There is also evidence for sex differences in the central effects of nicotine in laboratory animals. Although social factors impact smoking substantially in humans, findings from nonhuman subjects in controlled experiments provide support that sex differences in nicotine/tobacco addiction have a biological basis. Differences in the pharmacokinetic properties of nicotine or the effect of gonadal hormones may underlie some but not all sex differences observed. Laboratory-based information is very important in developing treatment strategies. Literature findings suggest that including sex as a factor in nicotine/tobacco-related studies will improve our success rates in individually tailored smoking cessation programs.

Solution concentration influences voluntary consumption of nicotine under multiple bottle conditions

Female Sprague Dawley rats were given a choice between two concentrations of nicotine solution (5 microg/ml and 8 microg/ml) and water in a 5-bottle arrangement for 25 days. Rats developed clear bottle discrimination, drinking more of the 5 microg/ml nicotine solution than water or the higher concentration nicotine solution. Further, intake patterns were sensitive to exposure. Differences in consumption of the three solutions (5 microg/ml vs. 8 microg/ml vs. water) were minimal during initial exposure days but became clear and stable with chronic exposure. Control rats given 5 bottles of water drank equally from all bottles and showed no development of preference for bottle position. Results suggest that both environmental availability and post-ingestional effects of nicotine contribute to the voluntarily oral consumption of nicotine solutions by rats. The influence of these two factors, however, is modulated by exposure. Availability appears to drive consumption initially, but the impact of concentration exerts more control over consumption with continued exposure. These data support the utility of oral methods of nicotine self-administration in the laboratory rat and suggest the need for further investigations into the biological impact of nicotine consumed orally.

Sex differences in the relationship between alcohol-associated smoking urge and behavior: a pilot study

This study examined sex differences in alcohol-associated smoking urge and smoking patterns to elucidate factors contributing to the co-use of alcohol and cigarettes. Participants were 39 (22M, 17F) binge-drinking tobacco chippers. Although men and women showed similar alcohol-smoking patterns and similar alcohol-induced smoking urges, a positive association between these factors was observed only in men. The lack of relationship in women suggests that co-use of these substances may be due to exteroceptive factors beyond the pharmacological effects of alcohol potentiating smoking urge.

Nicotine effects on affective response in depression-prone smokers

RATIONALE

Comorbidity between cigarette smoking and depression is thought to arise because depression-prone smokers self-administer nicotine to improve mood. Yet little evidence supports this view, and nicotine's effect on positive affect deficiency in depression remains largely unstudied.

OBJECTIVES

We hypothesized that (1) nicotine would dispel negative affect and enhance positive affect and (2) effects would be stronger for smokers vulnerable to depression, particularly during a depressed state.

MATERIALS AND METHODS

Regular smokers (N = 165) were recruited from the community: 63 with no history of major depressive disorder (MDD), 61 with recurrent past but no current MDD, and 41 with both current and past MDD. During four sessions, participants smoked either a nicotinized (NIC+) or denicotinized (NIC-) cigarette double blind after experiencing a negative mood induction or while undergoing a positive mood induction. Positive and negative affects were measured at baseline and at two time points after smoking.

RESULTS

Previously depressed smokers showed a heightened positive mood response to positive mood induction when smoking a nicotinized cigarette. Nicotine also increased the degree to which positive mood induction dispelled negative mood in depression-vulnerable smokers. Finally, nicotine worsened the negative affect response to negative mood induction for all groups.

CONCLUSION

Self-administering nicotine appears to improve depression-prone smokers' emotional response to a pleasant stimulus.

Sexual dimorphism in the acute effects of secondhand smoke on thyroid hormone secretion, inflammatory markers and vascular function

Experimental evidence for the physiological effects of secondhand smoke (SHS) is limited, although it affects millions of people globally and its prevalence is increasing, despite currently adopted antismoking measures. Also, scarce evidence suggests that the effects of SHS may be more pronounced in men. We conducted a randomized single-blind crossover study to investigate the sex-specific SHS effects in a controlled simulated bar/restaurant environment on gonadal and thyroid hormones, inflammatory cytokines, and vascular function. Twenty-eight (women = 14) nonsmoking adults underwent a 1-h exposure to moderate SHS and a 1-h control trial. Serum and urine cotinine, gonadal and thyroid hormones, inflammatory cytokines, heart rate, and arterial blood pressure were assessed before exposure and immediately after in both trials. Results showed that testosterone (P = 0.019) and progesterone (P < 0.001) in men and 17beta-estradiol (P = 0.001) and progesterone (P < 0.001) in women were significantly decreased after SHS. In men, SHS was accompanied by increased free thyroxine (P < 0.001), triiodothyronine (P = 0.020), and decreased the triiodothyronine-to-free thyroxine ratio (P = 0.033). In women, significant SHS-induced change was observed only in free thyroxine (P = 0.010), with considerable sex variation in free thyroxine and triiodothyronine and a decrease in luteinizing hormone (P = 0.026) and follicle-stimulating hormone (P < 0.001). After SHS, IL-1beta (P = 0.001) and systolic blood pressure (P = 0.040) were increased in men but not women. We concluded that a 1-h SHS exposure at bar/restaurant levels is accompanied by decrements in gonadal hormones in both sexes and marked increases in thyroid hormone secretion, IL-1beta production, and systolic blood pressure in men.

Availability influences initial and continued ingestion of nicotine by adolescent female rats

BACKGROUND

The availability of tobacco products is associated with the likelihood that adolescents will begin using tobacco. Yet the relationship between nicotine availability and voluntary consumption has not been tested experimentally in developing rats.

METHOD

The impact of environmental availability on adolescent female rats' initial reaction to and continued ingestion of a novel solution (nicotine or control) was compared using a standard 2-bottle free-choice method and a multiple-bottle method.

RESULTS

Manipulating the ratio of bottles containing novel solution to water directly influenced the amount of both nicotine and control solutions consumed. Although subtle differences emerged in intake patterns with prolonged exposure, overall intake patterns were remarkably similar for nicotine and control solutions.

CONCLUSION

The intake of oral nicotine was directly influenced by the availability of nicotine solution relative to water. The results indicate that simply providing the right environment is sufficient, and perhaps necessary, to increase rats' voluntary consumption of a nicotine solution without relying on deprivation or sweetening of the solution. That overall intake patterns were comparable for nicotine and control solutions suggests that this may be a general principle of rodent behavior rather than an effect specific to nicotine.

Toxicant exposure in cigarette reducers versus light smokers

BACKGROUND

The extent of exposure to tobacco toxicants in smokers who have reduced their cigarette intake compared with smokers who are light smokers is relatively unknown. The goal of this study is to investigate the occurrence of compensatory smoking in reducers compared with light smokers by measuring toxicant exposure.

METHODS

Participants in two smoking reduction intervention studies (N = 64) were selected for comparison with a group of light smokers (N = 62) who smoked the same number of cigarettes as the reducers. A compensatory smoking score was defined (biomarker level for reducer/biomarker level for light smoker) and calculated for urinary 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and its glucuronides (total NNAL), metabolites of the tobacco-specific lung carcinogen 4-(methylnitrosamino)-I-(3-pyridyl)-1-butanone, to measure the degree of smoking compensation in reducers when compared with the light smokers.

RESULTS

The mean level of creatinine-adjusted total NNAL for reducers was over twice that of light smokers even when they smoked about the same number of cigarettes per day. The difference of the mean total NNAL concentrations between light smokers and reducers was highly significant (P < 0.0001). Wide variability in total NNAL concentrations was also observed in reducers, with the extent of this variability between light smokers and reducers being significantly different (P = 0.0005). The level of individual reduction was shown to be a consistent predictor of compensatory smoking (r = 0.50; adjusted Ps = 0.002), with greater cigarette reduction associated with more compensation.

CONCLUSIONS

Compensatory smoking limits the harm reduction value of decreased smoking of cigarettes.

Transdermal nicotine-induced tobacco abstinence symptom suppression: nicotine dose and smokers' gender

An aversive tobacco abstinence syndrome, thought to reflect an underlying level of nicotine dependence, contributes to cigarette smokers' failed quit attempts. Nicotine replacement therapy (NRT) suppresses tobacco abstinence, but high relapse rates suggest room for improvement. Improving NRT's efficacy might begin with identifying factors that influence tobacco abstinence symptom suppression. Two such factors are smokers' gender and NRT dose. The purpose of this study was to determine the dose-related effects of transdermal nicotine (TN) on tobacco abstinence symptoms in 75 men and 53 women who regularly smoked cigarettes but who had abstained from smoking for at least 8-12 hr. Participants completed 4 double-blind, randomized 6.5-hr laboratory sessions that differed by TN dose (0, 7, 21, or 42 mg). Each session included blood sampling for plasma nicotine level, measurement of heart rate, participants' ratings of tobacco abstinence symptoms and effects of nicotine, and psychomotor performance. Increases in plasma nicotine level were related to TN dose and were independent of gender. TN-induced abstinence symptom suppression was dose-related for items assessing craving and urge to smoke and largely was independent of gender. TN increased heart rate and ratings of aversive side effects (e.g., nausea, lightheadedness) in a dose-related manner, and women were more sensitive at higher doses. Results from this laboratory study support the continued use of TN as a pharmacotherapy. Higher doses may ameliorate some abstinence symptoms, although the side effect profile, at least in the short term, may limit effectiveness, especially for women.

Individual and Contextual Influences on Adolescent Smoking

Cigarette smoking among adolescents remains one of the most important public health challenges. Despite much attention to research on the etiology of smoking, notably the examination of factors that differentiate adolescent smokers from never smokers, much less is known about factors that predict the development of dependence once an adolescent tries smoking. This paper reviews individual and contextual influences on the progression of smoking among adolescents. Highlights include a consideration of multiple levels of influence, from intra-individual factors, such as genetics, demographics, temperament and comorbidities, to social influences, such as families and peers, to the more macro, societal/cultural levels of influence, including advertising and tobacco-related policies. More recent work examining microcontextual influences through the use of Ecological Momentary Assessments is also discussed. Finally, the need to consider both developmental and transdisciplinary approaches to understanding the development of nicotine dependence in adolescents is emphasized.

Prospective examination of effects of smoking abstinence on cortisol and withdrawal symptoms as predictors of early smoking relapse

This study addressed the hypothesis that exaggerated mood and cortisol changes during the first 24h of smoking abstinence are associated with early relapse. Salivary cortisol levels and mood reports were measured during 24-h ad libitum smoking and the first 24-h abstinence period of a quit attempt. Seventy-two habitual smokers (34 women and 38 men) who were interested in smoking cessation participated. Cotinine concentrations in saliva and expired carbon monoxide were measured before and after abstinence and 1 week after the quit date to verify smoking status. Abstinence produced significant withdrawal symptoms in all participants and reduced cotinine and carbon monoxide levels. While participants showed the expected diurnal changes in cortisol levels, those who relapsed within the first week post quitting exhibited a greater drop in morning cortisol concentrations during abstinence relative to their ad libitum smoking levels. Participants who relapsed reported greater withdrawal symptoms, craving for cigarettes, and distress, and they also reported greater reduction in positive affect during the first 24-h period of abstinence than those who maintained abstinence. These results support the hypothesis that early relapse is associated with exaggerated mood and adrenocortical perturbations observed during the first day of abstinence.

Naltrexone attenuates acute cigarette smoking behavior

This within-subjects, placebo-controlled laboratory study was designed to examine the effects of naltrexone on cigarette response in 44 chronic smokers (23 male, 21 female). Each participant received either 50-mg oral naltrexone or identical placebo during the morning of the session after maintaining overnight abstinence. Subsequently, the participant was administered a smoking cue (holding lit cigarette) to examine craving and associated features of smoking, and instructed to smoke a cigarette 1 h later. This was followed by a smoking interval in which participants could choose to smoke up to four more cigarettes over a 2-h period. Subjective measures (withdrawal, craving, affect, and side effects) and smoking behavior were assessed throughout the session. Naltrexone significantly reduced the total number of choice cigarettes smoked and expired carbon monoxide levels (Ps<.05). Naltrexone significantly increased total side effects, especially for sedation (P<.01). Further, naltrexone significantly increased overall negative affect, and decreased positive affect 1 h after smoking the first cigarette (Ps<.05). However, naltrexone did not affect acute withdrawal or smoking urges. Despite mixed findings, women reported more overall naltrexone-induced withdrawal (P<.05) and side effects (P<.08) compared to men. Although the exact mechanism is unknown, the findings support an opioid antagonist attenuation of smoking behavior.

Nicotine dependence: development, mechanisms, individual differences and links to possible neurophysiological correlates

There is now little doubt that the majority of people who smoke tobacco do so to experience the psychopharmacological properties of the nicotine present in the smoke and that a significant proportion of habitual tobacco users become addicted to the drug nicotine. In the US some 80% and in Europe (Germany) 39% of smokers have been classified as dependent according to the diagnostic guidelines of the American Psychiatric Association. As a result, direct nicotine replacement is used increasingly by many people who want to stop smoking. The objectives of this review are to outline the mechanisms involved in the development and maintenance of nicotine dependence and to link behavioural observations to possible neurophysiologic correlates.

Nicotinic acetylcholine receptors as targets for antidepressants

While the monoamine deficiency hypothesis of depression is still most commonly used to explain the actions of antidepressant drugs, a growing body of evidence has accumulated that is not adequately explained by the hypothesis. This article draws attention to contributions from another apparently common pharmacological property of antidepressant medications--the inhibition of nicotinic acetylcholine receptors (nAChR). Evidence is presented suggesting the hypercholinergic neurotransmission, which is associated with depressed mood states, may be mediated through excessive neuronal nicotinic receptor activation and that the therapeutic actions of many antidepressants may be, in part, mediated through inhibition of these receptors. In support of this hypothesis, preliminary evidence is presented suggesting that the potent, centrally acting nAChR antagonist, mecamylamine, which is devoid of monoamine reuptake inhibition, may reduce symptoms of depression and mood instability in patients with comorbid depression and bipolar disorder. If this hypothesis is supported by further preclinical and clinical research, nicotinic acetylcholine receptor antagonists may represent a novel class of therapeutic agents for treating mood disorders.

Nicotinic cholinergic receptor expression in the human nasal mucosa

Twenty-four nasal mucosa specimens were obtained from the inferior or middle turbinates of 6 normal subjects and 18 patients with chronic sinusitis, inflammatory polyp formation, or sinus allergies. Reverse transcription-polymerase chain reaction analysis was used to identify the non-neuronal nicotinic cholinergic receptor (nAChR) subunits that were expressed in the nasal mucosa. Collectively, transcripts for alpha (alpha1, alpha2, alpha3, alpha4, alpha6, alpha7) and beta (beta2, beta3, beta4) nAChR subunit genes were detected in the respiratory mucosa. The alpha3, alpha7, and beta2 subunits were expressed in 92%, 88%, and 75% of the subjects, respectively. There was a high degree of interindividual variation in nAChR subunit gene expression among subjects. A significant univariate association was found between tissue type and beta4 expression and between gender and beta3 expression. These data suggest that cells in the nasal mucosa express the necessary messenger RNAs (mRNAs) for numerous nAChR combinations. Moreover, our identification of nAChR subunit mRNAs in the nasal mucosa extends the findings of other functional studies of nAChRs in nasal epithelial cells and implies that nicotine from tobacco products such as cigarette smoke and nicotine nasal spray may have direct cellular effects on nasal mucosa cells through activation of homogeneous or heterogeneous nAChRs. A significant number of patients receiving nicotine nasal spray have reported nasal irritation, and there are reports of transient irritation of the throat and trachea with the use of smoke-free nicotine cigarettes. These adverse respiratory effects may be due to activation of nAChRs in epithelial cells of the nose and trachea.

Nicotine self-administration

Any research pertaining to smoking or nicotine must demonstrate that its findings relate to changes in smoking or nicotine self-administration in order to be potentially relevant to understanding nicotine dependence or to treating smoking cessation. Nicotine alone, isolated from tobacco smoke, is self-administered by animals and humans. Pharmacological factors such as speed of dosing, dose amount, and pre-treatment with nicotinic antagonists clearly influence onset or rate of nicotine self-administration. However, environmental cues associated with nicotine intake can also substantially influence rate of self-administration and must be considered in the development of any treatment for smoking cessation. The specific acute subjective and behavioral effects of nicotine responsible for maintaining self-administration need to be identified, along with the minimum nicotine dose necessary for these effects. Individual differences in these effects, such as between men and women, also need to be examined. Findings in neuroscience and other areas of research need to be directly related to nicotine self-administration in order to clearly understand how they influence nicotine dependence. Overlooked by researchers is the influence of environmental factors, including social facilitation, on smoking or nicotine self-administration; these factors must be the primary cause of smoking relapse that occurs more than a week or so after a quit attempt. Laboratory-based findings must be extended to the natural environment to determine the degree to which they relate to smoking and nicotine reinforcement among smokers in the community (the population and venue for future treatment efforts).

Sex differences in brain and behavior: emphasis on nicotine, nitric oxide and place learning

Although males and females are unmistakably different, the recognition of sex as a key variable in science and medicine is considered a revolution in some circles. Sex differences transcend reproductive functions, are evident in the structural and functional organization of the brain, and are reflected in group differences in cognitive abilities and behavior. Males and females have different neural organizational patterns for information processing and different strategies in problem solving. Research on sex differences not only provides descriptive data, but also allows us to elucidate mechanisms that underlie our behavior. In this review, sex differences in the central actions of nicotine (an addictive substance) and nitric oxide, and performance on active avoidance and place learning tasks are discussed as examples, and biobehavioral approaches relating to these topics are presented.

Nicotine as an Addictive Substance: A Critical Examination of the Basic Concepts and Empirical Evidence

The present review is a critical analysis of the concepts behind and the empirical data supporting the view that tobacco use represents an addiction to nicotine. It deals with general aspects of the notion of addiction, while concentrating on specific problems associated with incorporating nicotine into current frameworks. The notion of addiction suffers from unprecedented definitional difficulties. The definitions offered by various authorities are very different, even contradictory. Definitions that reasonably include nicotine are so broad and vague that they allow many trivial things, such as salt, sugar, and watching television, to be considered addictive. Definitions that exclude the trivia also exclude nicotine. The addiction hypothesis, in general, is strongly shaped by views that certain drugs bring about a molecular level subversion of rationality. The main human evidence for this is verbal reports of smokers who say that they can't quit. On the other hand, the existence of many millions of successful quitters suggests that most people can quit. Some smokers don't quit, but whether they can't is another matter. The addiction hypothesis would be greatly strengthened by the demonstration that any drug of abuse produces special changes in the brain. It has yet to be shown that any drug produces changes in the brain different from those produced by many innocuous substances and events. The effects of nicotine on the brain are similar to those of sugar, salt, exercise, and other harmless substances and events. Apart from numerous conceptual and definitional inadequacies with the addiction concept in general, the notion that nicotine is addictive lacks reasonable empirical support. Nicotine does not have the properties of reference drugs of abuse. There are so many findings that conflict so starkly with the view that nicotine is addictive that it increasingly appears that adhering to the nicotine addiction thesis is only defensible on extra-scientific grounds.

Individual differences in rat locomotor activity are diminished by nicotine through stimulation of central nicotinic acetylcholine receptors

An increasing body of research has focused on isolating factors that predict or alter individual differences in the behavioral and neural processes mediating the effects of abused drugs. Within this framework, the current report assessed individual differences and the locomotor effect of nicotine. Rats were screened for activity induced by a novel environment. Rats, which were more active to initial environment exposure, remained more active even after seven additional 30-min exposures to the same environment. Treatment with nicotine-di-D tartrate (1 mg/kg, sc) disrupted this effect. This nicotine disruption of individual differences occurred whether nicotine suppressed locomotor activity (initial administration) or stimulated locomotor activity (seventh and eighth administration). Mecamylamine (1 mg/kg), but not hexamethonium (10 mg/kg), completely blocked the suppressant and stimulant effects of nicotine. Further, mecamylamine restored the nicotine-induced disruption of individual differences; hexamethonium had no effect. This data pattern suggests that the disruptive effects of acute and chronic nicotine on individual differences were mediated by neural nicotinic acetylcholine (nACh) receptors.

Nicotine-induced locomotor activity is increased by preexposure of rats to prenatal stress

Genetic factors are believed to play a predominant role in the individual differences observed in behavioral and pharmacological responses to drugs of abuse. An increasing literature indicates, however, that epigenetic factors can be involved as well. In this report we examined whether developmental changes induced by prenatal stress could alter the way animals respond to the psychostimulant effect of nicotine when adults. The results show that nicotine induces a dose-dependent increase of locomotor activity in both groups, and that prenatally-stressed animals exhibit a higher behavioral response at all doses. This study emphasizes the importance of early environment in the later development of drug-related behavior.

Smoking, anxiety, and attention: support for the role of nicotine in attentionally mediated anxiolysis

Based on J.D. Kassel and S. Shiffman's (1997) study, the hypothesis was tested that cigarette smoking's anxiolytic effects are attentionally mediated and depend on the presence of benign distraction. This study explored whether the attentionally mediated anxiolytic effects of smoking observed in the J. D. Kassel and S. Shiffman (1997) study could be replicated and are attributable to nicotine. The study examined the effect on anxiety of smoking a high- or low-yield nicotine cigarette with or without a current distraction in 67 smokers. As predicted, only those who smoked a high-yield cigarette paired with participation in a distracting activity experienced a significant reduction in anxiety. Those who smoked a high-yield cigarette in the absence of distraction experienced a slight exacerbation of anxiety. These findings suggest that nicotine--not the behavioral or sensory aspects of smoking--interacts with distraction and leads to alleviation of anxiety.

Nicotine discrimination in men and women

Nicotine is the primary compound that maintains tobacco smoking behavior, and nicotine reinforcement may be related to its discriminative stimulus effects. Nicotine in novel form, isolated from tobacco smoke, is often reinforcing in men but not in women, and clinical trials with nicotine replacement via gum or patch have often shown less efficacy in women vs. men trying to quit smoking. We hypothesize that this sex difference in nicotine reinforcement or clinical efficacy may be related to reduced intensity of nicotine's discriminative stimulus effects in women. Using formal drug discrimination procedures, we have found in several studies that discrimination responding across nasal spray nicotine doses tends to be flatter for women than men (i.e., sex x dose interaction), suggesting reduced sensitivity to changes in dose. Results from the field of psychophysiology, involving detection of physiological changes, are generally consistent with our findings, and suggest that the environmental context accompanying physiological change is important in understanding this sex difference. The implications of this sex difference for smoking cessation treatment and future research directions are presented.

Effects of chronic nicotine administration on locomotion depend on rat sex and housing condition

Nicotine's behavioral actions in the human smoker by self-report depend, in part, on the individual's gender and environment. The purpose of the present experiment was to determine whether effects of nicotine on unconditioned behaviors of rats also depend on sex and environmental conditions. Long-Evans rats (96 males and 96 females) living in individual or grouped housing were administered saline or 12 mg/kg/day nicotine via osmotic minipump for 14 days. Horizontal activity (a measure of overall activity and arousal), vertical activity (a measure of exploratory behavior), and center time (a possible index of anxiety) were measured on Day 10 of drug administration and on Day 2 of nicotine cessation. Group housing decreased horizontal and vertical activity and center time, with effects occurring sooner in females. Nicotine's effects depended on housing and sex. For males, nicotine altered indices of arousal and exploration, increasing these variables for group-housed males but decreasing them for individually housed males. For females, nicotine altered possible indices of anxiety, reducing anxiety for group-housed females. In cessation, housing effects continued in females and appeared more robustly in males. Results indicate that nicotine's chronic effects depend on subjects' sex and living environment.

Gender differences in the pharmacology of nicotine addiction

Smoking rates have declined in recent years less rapidly in women than in men. More adolescent girls than boys are currently smoking. Quitting smoking is reported in many studies to be more difficult in women than in men. These observations suggest that there may be gender differences in the nature of nicotine addiction. Gender differences in various pharmacological processes involved in nicotine addiction are reviewed. Women take in less nicotine from smoking per cigarette than men but, because of slower metabolism, nicotine levels in the body for a given number of cigarettes per day are similar in male and female smokers. Women tend to be less sensitive to the discriminative effects of nicotine and tend to regulate nicotine intake less precisely than men. On the other hand, women appear to be more sensitive to the effects of nicotine in reducing negative affect and reducing body weight. There is a strong association between depression and smoking, and this association appears to be stronger in women than in men. Women tend to respond more to environmental cues associated with smoking than do men. Thus, several lines of evidence suggest that nicotine addiction is different in women than in men. Understanding the basis for gender differences may be of utility in individualizing and optimizing smoking cessation therapy.

The effects of nicotine on the immune system

Although considerable work has been done on the potential health effects of smoking, little is known about the contribution of nicotine to those effects. This paper presents an overview of the immune system, and a discussion of the existing literature on the effects of tobacco smoke and nicotine on immunity. Treatment with nicotine has been shown to influence all aspects of the immune system, including alterations in humoral and cellular immunity. In addition, preliminary data suggest that gender and genetic factors impact on the immunological effects of nicotine. Finally, the possible mechanisms that might mediate the effects of nicotine are discussed.

Combined effects of nicotine and alcohol on subjective, behavioral and physiological responses in humans

Nicotine and alcohol have each been widely studied in humans, but there has been relatively little attention paid to their combined effects. This is surprising, given the high frequency with which they are consumed together. The limited literature on these combined effects is murky, partly because of failure to recognize that alcohol can have contrasting subjective mood effects depending on whether blood alcohol level is ascending or descending. However, in general, nicotine and alcohol (when blood alcohol level is descending) tend to have contrasting effects on mood ("stimulating" vs. "sedating", respectively), behavioral performance (slightly improving vs. impairing, respectively), and selected physiological responses (e.g. increased beta EEG vs. increased α EEG, respectively), but similar effects on other physiological responses (e.g. heart rate). Thus, when consumed together, mood, performance, and EEG responses are often intermediate between those due to alcohol alone or nicotine alone. Responses influenced in the same direction by either, such as cardiovascular effects, are exacerbated beyond effects due to either alone. Since mood and behavioral effects are likely to reinforce drug use, the attenuating influence of nicotine on alcohol's sedative effects could explain the frequently observed increase in smoking after alcohol consumption. At the same time, nicotine plus alcohol may exacerbate some physiological responses (e.g. cardiovascular) that can impact negatively on health. Limitations of this research and possible mechanisms of interaction between nicotine and alcohol are briefly noted. The need to consider the modulating influences of environmental and baseline-relevant factors is also emphasized.

Influence of training dose on nicotine discrimination in humans

Non-human research indicates that drug discrimination results may depend largely on the specific training conditions, including initial training dose. It has recently been shown that humans can discriminate among different doses of nicotine delivered by nasal spray. In this study, we examined the influence of training dose on subsequent behavioral discrimination of a range of nicotine doses. Male (n = 17) and female smokers (n = 16) were randomly assigned to "low" (10 micrograms/kg) versus "high" (30 micrograms/kg) nicotine training dose groups and trained reliably to discriminate this dose from placebo (0) on day 1 (> or = 80% correct identification). All but six subjects (four in low, two in high) learned this discrimination and continued on to day 2, in which both groups received 0, 5, 10, 20, and 30 micrograms/kg in ascending order (30 min between dosings) and were tested for generalization with their training dose using quantal and quantitative behavioral discrimination tasks. Subjective responses via traditional self-report measures were also assessed. Nicotine-appropriate responding on day 2 was significantly greater in low- versus high-dose groups, especially at 5 micrograms/kg. However, this difference due to training dose was seen more in women than in men. Discrimination behavior was associated with subjective effects of head rush in males, and with head rush and decline in urge to smoke in females. These results show that discriminative stimulus effects of nicotine are not fixed properties of the drug, but can be influenced by training conditions, and that effects associated with this discrimination may differ between men and women.

Acute thermogenic effects of nicotine and alcohol in healthy male and female smokers

Nicotine intake is associated with lower body weight in both women and men. Despite its energy content, alcohol consumption is also associated with lower body weight in women but not in men. Each drug may reduce weight by acutely increasing thermogenesis. During four sessions, nicotine (20 micrograms/kg per dosing) or placebo was given to male and female smokers (n = 9 each) via measured-dose nasal spray every 30 min for 2 h after consumption of diet tonic water with or without alcohol (0.5 g/kg). Each nicotine/placebo dosing was followed by assessment of energy expenditure by indirect calorimetry. Alcohol alone induced no significant effect in men or women, whereas nicotine alone and combined with alcohol induced a significant thermogenic effect in men but not women. These results are consistent with other research suggesting a reduced thermogenic responsiveness to drugs in women and indicate that nicotine must act via appetite suppression to reduce body weight in women. Similarly, these findings do not support the notion that alcohol is inversely related to body weight in women because of excessive acute thermogenesis.

Subjective and cardiovascular responses to nicotine combined with alcohol in male and female smokers

Nicotine and alcohol are often consumed concurrently by smokers. Each drug alone produces significant subjective and cardiovascular responses, but the effects of the two drugs in combination have rarely been examined. Smokers who were moderate alcohol drinkers (n = 18, 9 males and 9 females) participated in four sessions, involving acute administration of nicotine/placebo and alcohol/no alcohol. Subjects abstained overnight from tobacco and alcohol prior to each session. Nicotine (20 micrograms/kg per presentation) or placebo was administered by measured-dose nasal spray every 30 min for 2 h following consumption of diet tonic water with or without alcohol (0.5 g/kg). Subjective (visual analog scales, Profile of Mood States, Addiction Research Center Inventory) and cardiovascular (heart rate, systolic and diastolic blood pressure) responses were assessed after each nicotine/placebo administration. Nicotine increased head rush, dizzy, and most stimulant effects (i.e. jittery, tension, and arousal and decreased fatigue and relaxed), while alcohol increased intoxication, head rush, dizzy, and jittery, with no other stimulant effects. Nicotine and alcohol generally produced additive subjective and cardiovascular effects when consumed together, although nicotine attenuated sedating and intoxicating effects of alcohol alone. Furthermore, there were several interaction effects on subjective measures involving gender. Nicotine plus alcohol tended to attenuate some subjective effects due to one drug or the other alone in men but enhanced the effects of either alone in women. These findings indicate that nicotine and alcohol generally have additive subjective and cardiovascular effects, but that men and women differentially respond on some subjective measures to the combination of alcohol and nicotine.