Adolescent nicotine and tobacco smoke exposure enhances nicotine self-administration in female rats

Most people start experimenting with tobacco products or e-cigarettes in early adolescence and become habitual smokers in late adolescence or adulthood. These studies investigated if exposure to tobacco smoke or nicotine during early and mid-adolescence affects nicotine intake in late adolescence and early adulthood. Male and female rats were exposed to tobacco smoke from low- and high-nicotine SPECTRUM cigarettes or nicotine (0.3 mg/kg, twice a day) from postnatal day (P) 24-42. The self-administration sessions started at P55. The rats self-administered nicotine for 14-15 days under a fixed-ratio 1 schedule, and on the first day, the maximum number of infusions was twenty. Exposure to smoke from high, but not low, nicotine cigarettes during adolescence increased nicotine self-administration in female but not male rats. Adolescent treatment with nicotine facilitated nicotine self-administration. On the first day of nicotine self-administration, nicotine-treated rats reached the maximum number of infusions before the saline-treated control rats. Nicotine intake was also higher in the nicotine-treated female rats than in the saline-treated females. There was no sex difference in nicotine intake in controls when the data from the studies were combined. Smoke exposure led to a dose-dependent increase in plasma nicotine and cotinine levels in adolescent rats. Exposure to smoke from high-nicotine cigarettes and 0.3 mg/kg of nicotine led to plasma nicotine and cotinine levels that are similar to those in tobacco users. These findings indicate that in females, but not males, exposure to nicotine during adolescence may facilitate smoking and e-cigarette use later in life.

Nicotine pharmacokinetic profiles of the Tobacco Heating System 2.2, cigarettes and nicotine gum in Japanese smokers

Two open-label randomized cross-over studies in Japanese smokers investigated the single-use nicotine pharmacokinetic profile of the Tobacco Heating System (THS) 2.2, cigarettes (CC) and nicotine replacement therapy (Gum). In each study, one on the regular and one on the menthol variants of the THS and CC, both using Gum as reference, 62 subjects were randomized to four sequences: Sequence 1: THS - CC (n = 22); Sequence 2: CC - THS (n = 22); Sequence 3: THS - Gum (n = 9); Sequence 4: Gum - THS (n = 9). Plasma nicotine concentrations were measured in 16 blood samples collected over 24 h after single use. Maximal nicotine concentration (Cmax) and area under the curve from start of product use to time of last quantifiable concentration (AUC0-last) were similar between THS and CC in both studies, with ratios varying from 88 to 104% for Cmax and from 96 to 98% for AUC0-last. Urge-to-smoke total scores were comparable between THS and CC. The THS nicotine pharmacokinetic profile was close to CC, with similar levels of urge-to-smoke. This suggests that THS can satisfy smokers and be a viable alternative to cigarettes for adult smokers who want to continue using tobacco.

Pharmacokinetics of nicotine following the controlled use of a prototype novel tobacco vapor product

The objective of this clinical study was to investigate the pharmacokinetics of nicotine following the use of a prototype novel tobacco vapor (PNTV) product in comparison to a conventional cigarette (CC1). The study was conducted in Japanese healthy adult male smokers, using an open-label, randomized, two-period crossover design, to assess the pharmacokinetics of nicotine after controlled use of a PNTV product or CC1. During the study period, blood samples were drawn from subjects for the measurement of plasma nicotine concentrations and nicotine intake was estimated from the mouth level exposure (MLE). The Cmax and AUClast following the use of PNTV product were 45.7% and 68.3%, respectively, of those obtained with CC1 and there were no significant differences in the tmax and t1/2 between PNTV product and CC1. The estimated MLE following the use of PNTV product was approximately two-thirds of that obtained following the smoking of CC1, but the relative bioavailability of PNTV product to CC1 was approximately 104%. The differences in Cmax and AUClast between PNTV product and CC1 therefore are explained by differences in nicotine intake. These results suggest that the PNTV product shows a similar pharmacokinetic profile to CC1, while delivering less nicotine following controlled use.

Mu Opioid Receptor Binding Correlates with Nicotine Dependence and Reward in Smokers

The rewarding effects of nicotine are associated with activation of nicotine receptors. However, there is increasing evidence that the endogenous opioid system is involved in nicotine's rewarding effects. We employed PET imaging with [¹¹C]carfentanil to test the hypotheses that acute cigarette smoking increases release of endogenous opioids in the human brain and that smokers have an upregulation of mu opioid receptors (MORs) when compared to nonsmokers. We found no significant changes in binding potential (BP_ND) of [¹¹C]carfentanil between the placebo and the active cigarette sessions, nor did we observe differences in MOR binding between smokers and nonsmokers. Interestingly, we showed that in smokers MOR availability in bilateral superior temporal cortices during the placebo condition was negatively correlated with scores on the Fagerström Test for Nicotine Dependence (FTND). Also in smokers, smoking-induced decreases in [¹¹C]carfentanil binding in frontal cortical regions were associated with self-reports of cigarette liking and wanting. Although we did not show differences between smokers and nonsmokers, the negative correlation with FTND corroborates the role of MORs in superior temporal cortices in nicotine addiction and provides preliminary evidence of a role of endogenous opioid signaling in frontal cortex in nicotine reward.

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

RATIONALE

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Nicotine related brain activity: the influence of smoking history and blood nicotine levels, an exploratory study

OBJECTIVE

In this study, we sought to explore brain activity in nicotine-dependent men in response to acute intravenous nicotine using pharmacological magnetic resonance imaging (phMRI).

METHODS

phMRI was used to evaluate brain activity in response to 1.5 mg/70 kg intravenous nicotine or saline. The nicotine and saline were administered on different visits. The time courses of individual subjects' nicotine levels were used as regressors to assess neural activity relating to the infusions. The influence of smoking history and physiological measures on the response to nicotine were also investigated.

RESULTS

Greater lifetime exposure to cigarette smoking was significantly correlated with higher peak serum nicotine levels. PhMRI analysis of the differential response of nicotine compared to the saline condition showed distinctive activation patterns when analyzed with the (a) nicotine time course, (b) nicotine time course controlling for smoking history (pack years), and (c) pack years controlling for nicotine.

CONCLUSIONS

These results suggest that smoking exposure history influences serum nicotine levels and the brain's response to nicotine. Alterations in brain activity may be a result of vascular and neuro-adaptations involved in drug exposure and addiction.

Single-Dose Pharmacokinetics of Varenicline, a Selective Nicotinic Receptor Partial Agonist, in Healthy Smokers and Nonsmokers

Varenicline is a novel and selective alpha4beta2 nicotinic receptor partial agonist that is under development for smoking cessation. The primary objectives of this double-blind, placebo-controlled, single-dose, dose-escalation study were to determine the clinical pharmacology of single doses of varenicline in healthy smokers and nonsmokers under fed and fasted conditions and to determine the clinical pharmacology of varenicline administered in the morning and in the evening to smokers. Within each subject group, 4 subjects were randomized to varenicline and 2 subjects to placebo. Subjects received one single oral administration of varenicline or placebo: 6 doses (0.01, 0.03, 0.1, 0.3, 1.0, and 3.0 mg) were investigated in nonsmokers and 7 doses in smokers (0.01, 0.03, 0.1, 0.3, 1.0, 3.0, and 10.0 mg). Varenicline was well tolerated after single doses up to 3.0 mg in smokers and 1.0 mg in nonsmokers. Nausea and vomiting at doses above 3.0 mg in smokers and 1.0 mg in nonsmokers were dose limiting. Systemic exposure to varenicline and pharmacokinetic variability were similar between smokers and nonsmokers. Coadministration with food, smoking restriction, and time-of-day dosing did not affect the pharmacokinetics of varenicline.

Factors affecting exposure to nicotine and carbon monoxide in adult cigarette smokers

Exposure to cigarette smoke among smokers is highly variable. This variability has been attributed to differences in smoking behavior as measured by smoking topography, as well as other behavioral and subjective aspects of smoking. The objective of this study was to determine the factors affecting smoke exposure as estimated by biomarkers of exposure to nicotine and carbon monoxide (CO). In a multi-center cross-sectional study of 3585 adult smokers and 1077 adult nonsmokers, exposure to nicotine and CO was estimated by 24h urinary excretion of nicotine and five of its metabolites and by blood carboxyhemoglobin, respectively. Number of cigarettes smoked per day (CPD) was determined from cigarette butts returned. Puffing parameters were determined through a CreSS® micro device and a 182-item adult smoker questionnaire (ASQ) was administered. The relationship between exposure and demographic factors, smoking machine measured tar yield and CPD was examined in a statistical model (Model A). Topography parameters were added to this model (Model B) which was further expanded (Model C) by adding selected questions from the ASQ identified by a data reduction process. In all the models, CPD was the most important and highest ranking factor determining daily exposure. Other statistically significant factors were number of years smoked, questions related to morning smoking, topography and tar yield categories. In conclusion, the models investigated in this analysis, explain about 30-40% of variability in exposure to nicotine and CO.

α4β2 neuronal nicotinic receptor positive allosteric modulation: an approach for improving the therapeutic index of α4β2 nAChR agonists in pain

Nicotinic acetylcholine receptors (nAChRs) function as ligand-gated ion channels activated by the neurotransmitter acetylcholine. Gene knockout and antisense studies coupled with pharmacological studies with nAChR agonists have documented a role of α4β2 nAChR activation in analgesia. ABT-594, for the first time, provided clinical validation to the nAChR agonist pharmacology as a novel mechanism for treatment of pain. However, ABT-594 was poorly tolerated at the efficacious doses, particularly with respect to the side effects of nausea and emesis, which is thought to be mediated by activation of the ganglionic-type (α3-containing) nAChRs. An alternate approach is to selectively modulate the α4β2 nAChR via positive allosteric modulation. Positive allosteric modulators (PAMs) are compounds that do not interact with the agonist binding sites or possess intrinsic activity at the receptor per se, but potentiate the effects of the agonist. NS9283 (also known as A-969933), the first oxadiazole analog, was found to selectively enhance the potency of a range of nAChR agonists at α4β2, but not α3β4, nAChRs. Studies reported here, along with the accompanying manuscript [1] collectively point to the conclusion, based on preclinical models, that the analgesic efficacy of clinically well-tolerated doses of ABT-594 in humans can be significantly enhanced by co-administration with the α4β2 PAM. Additionally, studies in ferrets demonstrate no exaggeration of emetic effect when ABT-594 is co-dosed with NS9283. Cardiovascular studies in anesthetized dogs achieve supra-therapeutic plasma concentrations of ABT-594 (>20-fold) without hemodynamic or electrophysiological effects using the co-administration paradigm.

Acute effects of waterpipe tobacco smoking: a double-blind, placebo-control study

BACKGROUND

Waterpipe tobacco smoking usually involves heating flavored tobacco with charcoal and inhaling the resulting smoke after it has passed through water. Waterpipe tobacco smoking increases heart rate and produces subjective effects similar to those reported by cigarette smokers. These responses are thought to be nicotine-mediated, though no placebo-control studies exist. Accordingly, this double-blind, placebo-control study compared the acute physiological and subjective effects of waterpipe tobacco smoking to those produced when participants used a waterpipe to smoke a flavor-matched, tobacco-free preparation.

METHODS

Occasional waterpipe tobacco smokers (n = 37; 2-5 monthly smoking episodes for ≥ 6 months) completed two double-blind, counterbalanced sessions that differed by product: preferred brand/flavor of waterpipe tobacco or flavor-matched, tobacco-free preparation. For each 45-min, ad lib smoking episode blood and expired air CO were sampled, cardiovascular and respiratory response were measured, and subjective response was assessed.

RESULTS

Waterpipe tobacco smoking significantly increased mean (± SEM) plasma nicotine concentration (3.6 ± 0.7 ng/ml) and heart rate (8.6 ± 1.4 bpm) while placebo did not (0.1 ± 0.0 ng/ml; 1.3 ± 0.9b pm). For carboxyhemoglobin (COHb) and expired air CO, significant increases were observed for tobacco (3.8 ± 0.4%; 27.9 ± 2.6 ppm) and for placebo (3.9 ± 0.4%; 27.7 ± 3.3 ppm) with no differences across condition. Independent of condition, symptoms of nicotine/tobacco abstinence (e.g., "urges to smoke", "anxious") were reduced and direct effects (e.g., "dizzy", "satisfy") increased.

DISCUSSION

These results from the first placebo-control study of waterpipe tobacco smoking demonstrate that waterpipe-induced heart rate increases are almost certainly mediated by nicotine though the subjective effects observed in these occasional smokers were not.

Multiple species metabolism of PHA-568487, a selective alpha 7 nicotinic acetylcholine receptor agonist

The quinuclidine PHA-0568487(1) is an agonist of the alpha 7 nicotinic acetylcholine receptor that was designed to mitigate the bioactivation associated with the core scaffold and subsequently remove associated liabilities with in vivo tolerability. The drug metabolites of 1 in nonclinical species were identified in plasma and urine of rats, dogs and monkeys receiving oral administrations of 1. The in vitro biotransformation of 1 was subsequently investigated in multiple species employing cryopreserved hepatocytes, hepatic subcellular fractions and recombinantly-expressed human P450 enzymes. In addition, in vitro metabolism of synthetically prepared metabolite precursors were instrumental in the elucidation of several secondary metabolites. The results indicated that the principal biotransformation of 1 was oxidation of the benzo[1,4]dioxane moiety (M8, M10) followed by subsequent oxidation to a range of secondary metabolites (M1-7, M9, M11, M13-15, and M17-18). The carboxylic acids M1 and M2 resulting from the oxidative cleavage of the dioxane ring were the principal metabolites observed in the plasma, urine and hepatocyte incubations across all species (M1 & M2). Quinuclidine oxidation was another pathway of importance, yielding an N-oxide (M12) which was also observed in all species.P450 2D6 and FMO1 catalyze the oxidation of the quinuclidine nitrogen. The N oxidation of the quinuclidine moiety is consistent with previously published accounts of this scaffold's metabolism and, interestingly, may implicate the uncommon quinuclidine moiety as an entity directing the metabolism of this scaffold (e.g., 1) via FMO1 and P450 2D6 oxidation.

The bioequivalent and effect of nicotine formulation gum on smoking cessation

OBJECTIVE

To compare the absorption rate of nicotine in volunteer blood, and determine the clinical trial on smoking cessation.

MATERIAL AND METHOD

This method using reverse phase C18 column and buffer pH 5.05 as the mobile phase, flow rate 0.9 ml/min. The UV-visible detector found the retention time of nicotine in gum and volunteer blood was 5.0756 min. The linear calibration curves of nicotine in human blood were obtained over the concentration range of 2.0-20.0 microg/ml. The coefficient variability for Nicotine gum 6.74% (2 mg/g). Extraction recovery was over 86% in blood, correlation coefficient of determination (r2) > 0.9999 and the detection limit 0.0060 microg/ml. The 24 healthy volunteer men, 27 to 55 years of age, were habitual cigarette smokers. They were randomized into two groups, 12 subjects chewed two 2 mg pieces, Nicomild-2 Sugar Free Gum (Millimed, Thailand), the other chewed two 2 mg, pieces, Nicorette Sugar Free (Pharmacia AB, Helsingborg, Sweden.) Volunteers' blood samples were withdrawn at 0, 15, 30, 40 min, concentration of nicotine in blood were measured by HPLC. The 199 subjects were openly recruited under the project of "The smoking cessation for Phor Laung" (5-December). All of them received Nicomild-2 (nicotine polyestex gum) between November 2007 and December 2007.

RESULTS

The absorption rate of nicotine in volunteers' blood Nicomild-2 and Nicorette at 0, 15, 30, 40 minutes were 0, 51.84, 26.73, 21.012 and 0, 56.603, 21.83, 15.183 (ng/min). Both of them were found to have maximum absorption rate at 15 minutes. When comparing the maximum absorption rate at 15 minute of Nicomild-2 (sugar free) with Nicorette (sugar free) didn't have significant differences detected. Treatment with nicotine polyestex gum were reported 65.3% (130/199) at 4 weeks compared with failure 30.15% (60/199)[ 65.3% vs 30.15%; p = 0.005]. The authors found 9 (4.5%) subjects successfully quit smoking free nicotine replacement therapy (NRT).

Methods for quantification of exposure to cigarette smoking and environmental tobacco smoke: focus on developmental toxicology

Active and passive smoking have been associated with an array of adverse effects on health. The development of valid and accurate scales of measurement for exposures associated with health risks constitutes an active area of research. Tobacco smoke exposure still lacks an ideal method of measurement. A valid estimation of the risks associated with tobacco exposure depends on accurate measurement. However, some groups of people are more reluctant than others to disclose their smoking status and exposure to tobacco. This is particularly true for pregnant women and parents of young children, whose smoking is often regarded as socially unacceptable. For others, recall of tobacco exposure may also prove difficult. Because relying on self-report and the various biases it introduces may lead to inaccurate measures of nicotine exposure, more objective solutions have been suggested. Biomarkers constitute the most commonly used objective method of ascertaining nicotine exposure. Of those available, cotinine has gained supremacy as the biomarker of choice. Traditionally, cotinine has been measured in blood, saliva, and urine. Cotinine collection and analysis from these sources has posed some difficulties, which have motivated the search for a more consistent and reliable source of this biomarker. Hair analysis is a novel, noninvasive technique used to detect the presence of drugs and metabolites in the hair shaft. Because cotinine accumulates in hair during hair growth, it is a unique measure of long-term, cumulative exposure to tobacco smoke. Although hair analysis of cotinine holds great promise, a detailed evaluation of its potential as a biomarker of nicotine exposure, is needed. No studies have been published that address this issue. Because the levels of cotinine in the body are dependent on nicotine metabolism, which in turn is affected by factors such as age and pregnancy, the characterization of hair cotinine should be population specific. This review aims at defining the sensitivity, specificity, and clinical utilization of different methods used to estimate exposure to cigarette smoking and environmental tobacco smoke.

Influence of nicotine on blood perfusion and bone healing during distraction osteogenesis

Nicotine is the main chemical component in tobacco products and its effect on bone healing remains controversial. This study aims to evaluate the influence of nicotine on blood perfusion and bone healing using a rabbit model of mandibular distraction osteogenesis. The dose dependent effect of nicotine on bone regeneration, and the effect of nicotine on blood perfusion and angiogenesis were assessed by radiography, micro-computed tomography, histological and immunohistochemical analysis, real time PCR and Laser Doppler monitoring. Results showed that bone healing was compromised by high dose nicotine treatment. Nicotine exposure increased microvessel density, whereas inhibited blood flow and bone formation. The expression of bone morphogenetic protein (BMP)-2 in osteoblasts was also decreased. The present study supported that nicotine has a dose dependant influence on bone healing in distraction osteogenesis. Nicotine compromises bone regeneration possibly by causing ischemia and inhibiting BMP expression in osteoblasts. Nicotine exposure enhances angiogenesis but can not compensate for the adverse effect of vasoconstriction.

The influence of transdermal nicotine on tobacco/nicotine abstinence and the effects of a concurrently administered cigarette in women and men

Transdermal nicotine (TN) is an efficacious smoking cessation pharmacotherapy thought to work, in part, by attenuating the effects of tobacco/nicotine abstinence and the effects of concurrently smoked cigarettes. Clinical trials suggest that TN may be less efficacious for women. This study explored the possibility of TN-related gender differences in > or = 8 hour abstinent smokers (54 women, 70 men) who completed four within-subject, double-blind, placebo-controlled sessions corresponding to 0, 7, 14, and 21 mg TN. In each approximately 6.5-hr long session participants smoked an own-brand cigarette 4 hours after TN administration and physiological and subjective outcomes were examined throughout each session. Results revealed that TN suppressed some signs and symptoms of tobacco abstinence and attenuated some effects of smoking, and these effects were not dependent on gender. Women were more sensitive to the direct effects of nicotine (e.g., ratings of Nauseous) and, independent of TN dose, self-administered less nicotine when smoking and rated smoking as less rewarding. Thus, although this study does not shed light on clinical observations that TN is less effective for women, results suggest that TN might need to be combined with other interventions to supplement its effects on tobacco/nicotine abstinence and concurrent smoking.

Effects of smoking successive low- and high-nicotine cigarettes on hypothalamic-pituitary-adrenal axis hormones and mood in men

Smoking one cigarette produces rapid nicotine dose-related increases in hypothalamic-pituitary-adrenal (HPA) axis hormones, mood, and heart rate, but relatively little is known about the effects of smoking several cigarettes successively. Twenty-four healthy adult men who met Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV) criteria for nicotine dependence provided informed consent. After overnight abstinence from smoking, men smoked three low- or high-nicotine cigarettes for 4 min each at 60 min intervals. Samples for nicotine and hormone analysis, Visual Analog Scale (VAS) ratings of subjective effects and heart rate were collected at 4, 8, 12, 16, 20, 30, 40, and 50 min after each cigarette. After low-nicotine cigarettes, nicotine levels, adrenocorticotropin hormone, and heart rate did not increase significantly, cortisol and dehydroepiandrosterone decreased significantly, and positive VAS ratings were lower but parallel to ratings after high-nicotine cigarette smoking. After high-nicotine cigarettes, peak nicotine levels increased monotonically. HPA axis hormones increased after smoking, but peak levels did not differ significantly after successive high-nicotine cigarettes. Positive VAS ratings and heart rate increased after each high-nicotine cigarette, but peak levels were lower after smoking the second and third cigarette. 'Craving' decreased significantly after smoking both low- and high-nicotine cigarettes, then gradually increased during the 60 min interval between cigarettes. These data are consistent with clinical reports that the first cigarette after overnight nicotine abstinence is most salient. Tolerance to the subjective and cardiovascular effects of nicotine developed rapidly during repeated cigarette smoking, but nicotine-stimulated increases in HPA axis hormones did not change significantly.

Dose-related enhancement of mood and cognition in smokers administered nicotine nasal spray

The discovery of the role of nicotinic receptors in attention and memory has led to the testing of nicotinic analogs as cognitive enhancing agents in patient populations. Empirical information about nicotine's ability to enhance elements of attention and memory in normal individuals might guide development of therapeutic uses of nicotine in cognitively impaired populations. The purpose of this study was to determine the effect of nicotine on continuous attention, working memory, and computational processing in tobacco-deprived and nondeprived smokers. A total of 28 smokers (14 men, 14 women) participated in a double-blind, placebo-controlled, within-subject study, in which they were overnight (12 h) tobacco deprived at one session and smoked ad libitum before the other session. At each session, participants received 0, 1, and 2 mg nicotine via nasal spray in random order at 90 min intervals. Before and after each dose, a battery of cognitive, subjective, and physiological measures was administered, and blood samples were taken for plasma nicotine concentration. Overnight tobacco deprivation resulted in impaired functioning on all cognitive tests and increased self-reports of tobacco craving and negative mood; nicotine normalized these deficits. In the nondeprived condition, nicotine enhanced performance on the continuous performance test (CPT) and an arithmetic test in a dose-related manner, but had no effect on working memory. In general, women were more sensitive than men to the subjective effects of nicotine. These results provide an unequivocal determination that nicotine enhanced attentional and computational abilities in nondeprived smokers and suggest these cognitive domains as substrates for novel therapeutic indications.

CYP2A6 genotype, phenotype, and the use of nicotine metabolites as biomarkers during ad libitum smoking

CYP2A6 inactivates nicotine to cotinine and cotinine to 3-hydroxycotinine. We investigated which of plasma nicotine and metabolites were most related to CYP2A6 genotype and smoking levels. We assessed demographic and smoking histories in 152 Caucasian ad libitum smokers, measured breath carbon monoxide (CO) levels, and determined plasma nicotine, cotinine, and 3-hydroxycotinine by high-performance liquid chromatography and CYP2A6 genotypes by PCR. Cigarettes per day was most closely related to CO (r = 0.60, P < 0.001) followed by plasma cotinine (r = 0.53, P < 0.001), whereas plasma cotinine was most strongly correlated with CO levels (r = 0.74, P < 0.001), confirming that cotinine is a good indicator of smoking levels; this was not limited by CYP2A6 variants. 3-Hydroxycotinine/cotinine is reported to be a good marker of CYP2A6 activity, and we found that the 3-hydroxycotinine/(cotinine + nicotine) ratio was most correlated with CYP2A6 genotype (r = 0.38, P < 0.001). Inclusion of the CYP2A6*12A allele strengthened the correlation (r = 0.46, P < 0.001), suggesting that the identification of novel alleles will continue to improve this relationship. Nicotine metabolism is slower in smokers, and we have shown that CYP2A6 is reduced by nicotine treatment in monkeys. Here, we found that plasma nicotine levels were inversely correlated with CYP2A6 activity (3-hydroxycotinine/cotinine, r = -0.41, P < 0.001) among those without CYP2A6 variants, suggesting a reduction in metabolism with higher nicotine levels. Together, these findings (a) confirm the use of plasma cotinine and CO as indicators of Caucasians' smoking levels, and that this is not limited by CYP2A6 genetic variation; (b) indicate that 3-hydroxycotinine/cotinine and 3-hydroxycotinine/(cotinine + nicotine) are moderately good indicators of the CYP2A6 genotype; and (c) support that nicotine exposure may reduce its own metabolism.

Prenatal nicotine exposure transiently alters the lung mechanical response to hypoxia in young lambs

To test the hypothesis that fetal nicotine exposure alters the lung mechanical response to hypoxia (10% O(2)) 10 lambs were exposed during the last fetal trimester to a low dose nicotine (LN) and 10 to a moderate dose (MN) (maternal dose 0.5 and 1.5mg/(kgday) free base, respectively). There were 10 controls (C). At 12 days, minute ventilation increased significantly less in MN compared with LN but not with C. In contrast to C and LN, MN did not show anticipated increases in dynamic compliance, specific compliance and FRC or decrease in lung resistance but had signs of airway hyperreactivity during hypoxia. Nicotine exposure did not alter the cardiovascular response. These adverse effects decreased with advancing age. In summary, prenatal nicotine exposure alters the lung mechanical response to hypoxia. We speculate that prenatal nicotine-induced alterations of lung mechanics during hypoxia may contribute to an increased vulnerability to hypoxic stress during infancy.

Identification of novel CYP2A6*1B variants: the CYP2A6*1B allele is associated with faster in vivo nicotine metabolism

Cytochrome P450 2A6 (CYP2A6) is the human enzyme responsible for the majority of nicotine's metabolism. CYP2A6 genetic variants contribute to the interindividual and interethnic variation in nicotine metabolism. We examined the association between the CYP2A6*1B variant and nicotine's in vivo metabolism. Intravenous infusions of deuterium-labeled nicotine were administered to 292 volunteers, 163 of whom were White and did not have common CYP2A6 variants, other than CYP2A6*1B. We discovered three novel CYP2A6*1B variants in the 3'-flanking region of the gene that can confound genotyping assays. We found significant differences between CYP2A6*1A/*1A, CYP2A6*1A/*1B, and CYP2A6*1B/*1B groups in total nicotine clearance (17.2+/-5.2, 19.0+/-6.4, and 20.4+/-5.9, P<0.02), non-renal nicotine clearance (16.4+/-5.0, 18.5+/-6.2, and 19.8+/-5.7, P<0.01), and the plasma trans-3'-hydroxycotinine/cotinine ratio (0.26+/-0.1, 0.26+/-0.1, and 0.34+/-0.1, P<0.001). There were also differences in total nicotine (29.4+/-12.9, 25.8+/-0.12.9, and 22.4+/-12.4, P<0.01), cotinine (29.2+/-8.1, 32.2+/-9.1, and 33.0+/-6.6, P<0.01) and trans-3'-hydroxycotinine (32.4+/-9.1, 34.2+/-12.3, and 41.3+/-11.3, P<0.001) excreted in the urine. We report evidence that CYP2A6*1B genotype is associated with faster nicotine clearance in vivo, which will be important to future CYP2A6 genotype association studies.

Metabolism and Disposition of a Selective α7 Nicotinic Acetylcholine Receptor Agonist in Humans

The metabolism and disposition of N-(3R)-1-azabicyclo[2.2.2]oct-3-ylfuro[2,3-c]pyridine-5-carboxamide (1), an alpha(7) nicotinic acetylcholinergic receptor agonist, were elucidated in humans (4 female, 4 male; all white) after an oral dose of [(3)H]1. Overall, 1 was well tolerated, with >94% of administered radioactivity excreted renally by 48 h postdose; lyophilization of all urine and plasma samples confirmed (3)H stability within [(3)H]1. Across genders, 1 underwent low-to-moderate oral clearance comprising both renal (67%) and metabolic (33%) components, with the biotransformation of 1 occurring predominantly via oxidation of its furanopyridine moiety to carboxylic acid 2, and minimally by modification of its quinuclidine nitrogen to N-oxide 4 or N-glucuronide M5. Experiments using human in vitro systems were undertaken to better understand the enzyme(s) involved in the phase 1 biotransformation pathways. The formation of 2 was found to be mediated by CYP2D6, a polymorphically expressed enzyme absent in 5 to 10% of white people, whereas the generation of 4 was catalyzed by CYP2D6, FAD-containing monooxygenase 1 (FMO1), and FMO3. It is of interest that, although no overall gender-related differences in excretory routes, mass recoveries, pharmacokinetics, or metabolite profiles of 1 were evident, the observation of one of eight subjects (13%) showing disparate (relative to all other volunteers) systemic exposures to 1, and urinary and plasma quantitative profiles nearly devoid of 2 with the highest levels of 1, seem consistent with both the identification of CYP2D6 as the only major recombinant cytochrome P450 transforming 1 to 2 and the demographics of white CYP2D6 poor metabolizers. Data also reported herein suggest that 4 is generated predominantly by renal FMO1 in humans.

Population Pharmacokinetics of Nicotine and Its Metabolites I. Model Development

We present a mechanistic population model for the pharmacokinetics of nicotine (NIC), its primary (CYP2A6-generated) metabolite cotinine (COT), and COT's primary (CYP2A6-generated) metabolite, trans-3'-hydroxycotinine (3HC). Sixty-six subjects received oral deuterium-labeled NIC (NIC-d(2), 2 mg), and COT (COT-d(4), 10 mg) simultaneously. Frequent plasma/saliva samples were taken for measurement of concentrations of NIC-d(2), COT-d(2), 3HC-d(2), COT-d(4), and 3HC-d(4). A mechanistic population pharmacokinetic model was fitted to all data simultaneously. Most of the pharmacokinetic parameters found here agree with previous studies and with a previous model-independent analysis of these data. However, 3HC t(1/2) was found to be considerably shorter than a previously reported value, possibly because 3HC elimination was saturated with the larger doses used in the previous study. Additionally, the delay in the appearance of COT-d(2) in the blood was modeled as a time delay (t(1/2) = 12 min) in its release from the liver following NIC-d(2) administration. The most important result of the previous model-independent analysis of these data, confirmed here, is that NIC clearance to COT and the 3HC:COT saliva concentration ratio are highly correlated (r = 0.7-0.8). The correlation above support that idea that the 3HC:COT ratio can be used as a predictor of CYP2A6 activity and nicotine clearance. The model-based analysis extends and further justifies this conclusion.

Prediction methods for nicotine clearance using cotinine and 3-hydroxy-cotinine spot saliva samples II. Model application

To develop and compare methods that predict individual nicotine (NIC) clearance, which reflects CYP2A6 activity, using random saliva cotinine (COT) and trans 3'-hydroxycotinine (3HC) measurements. COT and 3HC saliva concentrations in smokers were simulated utilizing a mechanistic population pharmacokinetic model of NIC metabolism that was adapted from the one described in a companion paper. Four methods to predict NIC clearance using the metabolites concentrations were compared. The precision bias, and the fraction of predictions that are made with an absolute error below 25% were the performance measures evaluated. Four prediction methods were compared: (M1) reference method, an intercept slope model of the metabolite concentration ratios ([3HC]/[COT]) (M2) an intercept slope model of the natural logarithm of the metabolite ratios (M3) a spline of the logarithm of the metabolite ratios (M4) Maximal Posteriori Bayesian estimate of NIC clearance conditioned on the model, COT and 3HC concentrations. In addition, the effect of smoking patterns on the concentrations of COT and 3HC was evaluated. The precision, accuracy, and the fraction of predictions with an absolute error below 25%, were higher for methods M2-M4 compared to method M1. However, the differences between M2 and M4 were small. Additionally, smoking pattern did not affect the metabolite concentration profiles. Predicting NIC clearance using an intercept slope model of the natural logarithm of the ratio of 3HC to COT appears to be a relatively simple method that is better than using the metabolite ratio directly. This method has a bias of approximately -10%, precision of approximately 60%. The fraction of estimates below an absolute error of 25% is 43%. These results support use of M2 to estimate CYP2A6 activity in smokers in the clinical setting.

Effects of nicotine vary across two auditory evoked potentials in the mouse

BACKGROUND

Schizophrenia patients display sensory processing deficits, reduced alpha7-nicotine receptor expression, and increased incidence of smoking, prompting investigation of nicotine receptor agonists as possible treatments. We evaluated the effects of acute and chronic nicotine, using an animal model that incorporates genetic variation for sensory processing and nicotine sensitivity.

METHODS

C57BL/6J and DBA/2Hsd mice received 2 weeks of 4.2 mg/kg chronic nicotine or saline. Auditory evoked potentials were recorded before and after acute nicotine injection of 1.05 mg/kg on day 14, with a paired-click paradigm (S1/S2). Amplitude and gating of the P20 and N40 were compared between conditions.

RESULTS

Acute nicotine increased the amplitude and gating of the P20 and decreased the amplitude and gating of the N40 across all groups, primarily by acting on S1. Chronic nicotine attenuated the effects of acute nicotine on the N40.

CONCLUSIONS

Our data support the notion that the mouse P20 shares pharmacological response properties with the human P50. In addition, findings suggest that nicotine might increase the initial sensory response (S1), with a resulting improvement in gating of some components.

Monoamine oxidase A rather than monoamine oxidase B inhibition increases nicotine reinforcement in rats

Although nicotine is considered to be responsible for the addictive properties of tobacco, growing evidence underlines the importance of non-nicotine components in smoking reinforcement. It has been shown that tobacco smoke contains monoamine oxidase (MAO) A and B inhibitors and decreases MAO-A and MAO-B activity in smokers. Here, we investigated the effects of clorgyline hydrochloride (irreversible MAO-A inhibitor; 2 mg/kg/day), selegiline (irreversible MAO-B inhibitor; 4 mg/kg) and the beta-carboline norharmane hydrochloride (reversible MAO-B inhibitor; 5 mg/kg/day) treatments on nicotine self-administration (30 microg/kg/infusion, free base) in rats. Independent of the responsiveness to novelty and locomotor activity stimulation, only clorgyline hydrochloride treatment increased the intake of nicotine in a fixed-ratio schedule (FR5) of reinforcement. When a progressive-ratio schedule was implemented, both clorgyline hydrochloride and norharmane hydrochloride treatments potentiated the reinforcing effects of nicotine, whereas selegiline had no effect. Taken together, these results indicate that MAO-A inhibition interacts with nicotine to enhance its rewarding effects in rats and suggest that other compounds present in tobacco, such as beta-carboline, may also play an important role in sustaining smoking behavior in humans.

Nicotine dose-concentration relationship and pregnancy outcomes in rat: biologic plausibility and implications for future research

Cigarette smoke (CS) exposure during pregnancy can lead to profound adverse effects on fetal development. Although CS contains several thousand chemicals, nicotine has been widely used as its surrogate as well as in its own right as a neuroteratogen. The justification for the route and dose of nicotine administration is largely based on inferential data suggesting that nicotine 6 mg/kg/day infused continuously via osmotic mini pumps (OMP) would mimic maternal CS exposure. We provide evidence that 6 mg/kg/day nicotine dose as commonly administered to pregnant rats leads to plasma nicotine concentrations that are 3-10-fold higher than those observed in moderate to heavy smokers and pregnant mothers, respectively. Furthermore, the cumulative daily nicotine dose exceeds by several hundred fold the amount consumed by human heavy smokers. Our study does not support the widely accepted notion that regardless of the nicotine dose, a linear nicotine dose-concentration relationship exists in a steady-state OMP model. We also show that total nicotine clearance increases with advancing pregnancy but no significant change is observed between the 2nd and 3rd trimester. Furthermore, nicotine infusion even at this extremely high dose has little effect on a number of maternal and fetal biologic variables and pregnancy outcome suggesting that CS constituents other than nicotine mediate the fetal growth restriction in infants born to smoking mothers. Our current study has major implications for translational research in developmental toxicology and pharmacotherapy using nicotine replacement treatment as an aid to cessation of cigarette smoking in pregnant mothers.

Enamel matrix derivative versus guided tissue regeneration in the presence of nicotine: a histomorphometric study in dogs

AIM

The goal of this histometric study was to compare the healing process of dehiscence-type defects treated by enamel matrix derivative (EMD) or guided tissue regeneration (GTR) under the effect of nicotine in the dog model.

MATERIALS AND METHODS

Eight mongrel dogs were used. Buccal osseous dehiscences were surgically created on the mesial roots of the mandibular third and fourth pre-molars. The defects were exposed to plaque accumulation for 3 months. After this period, the defects were randomly assigned to one of the treatments: open flap debridement (OFD), EMD or GTR with a resorbable membrane. During 4 months, the dogs received subcutaneous administration of nicotine (2 mg/kg twice a day with a 12 h interval between the applications). After this period, the animals were killed and the blocks were processed. The histometric parameters evaluated included gingival recession, epithelial length, connective tissue adaptation, new cementum and new bone.

RESULTS

A superior length of new cementum was observed in the sites treated by EMD in comparison with OFD (p< or =0.05). No statistically significant differences were observed between GTR and the other groups.

CONCLUSIONS

In the presence of nicotine, EMD may promote more new cementum formation than OFD while GTR failed to provide a significant difference.

Development and in vitro/in vivo evaluations of bioadhesive buccal tablets for nicotine replacement therapy

Buccal bioadhesive tablet formulations of nicotine hydrogen tartrate (NHT) for nicotine replacement therapy (NRT) were developed using chitosan and carbomer at different ratios. Magnesium hydroxide was incorporated into the formulations as pH increasing agent. In vitro release and bioadhesion properties of the tablets were investigated. Release of NHT from the tablets was increased with the increasing amount of chitosan in formulations whilst the bioadhesion of the tablet was decreased. In vivo studies were carried out in healthy, non-smoker volunteers in comparison to a commercially available transdermal patch. Plasma nicotine and cotinine levels were determined using gas chromatography-mass spectrophotometry. No significant difference was found between the maximum plasma nicotine concentrations (Cmax) obtained with the buccal tablet and the transdermal patch (p > 0.05). Time to reach the Cmax was 2.9 +/- 0.2 h and 11.5 +/- 1.3 h, and AUC0-24 values were 59.3 +/- 5.1 ng x h x mL(-1) (0-12 h) and 204.1 +/- 31.2 ng x h x mL(-1) for buccal tablet and transdermal patch, respectively.

Comparison of Nicotine Pharmacokinetics in Healthy Japanese Male Smokers Following Application of the Transdermal Nicotine Patch and Cigarette Smoking

Transdermal nicotine patch (TNP) contains approximately 16.6 and 24.9 mg of nicotine per 20 and 30 cm2 (TNP-20 and TNP-30). The aims of the study are to investigate linearity of nicotine pharmacokinetics after single application of different strengths of TNP and to directly compare plasma nicotine concentrations with those during cigarette smoking. Twelve healthy Japanese male smokers were randomly allocated to 1 of 2 cohorts consisting of 6 subjects each. Cohort 1 subjects received 1 sheet of TNP-20 (TNP-20x1) in period 1, and 2 sheets of TNP-20 (TNP-20x2) in period 3. Cohort 2 subjects were received 1 sheet of TNP-30 (TNP-30x1) in period 2, and smoked a total of 12 cigarettes at 1 h intervals in period 4. Each TNP was applied to the upper arm for 16 h. After TNP-20x1 or TNP-20x2 treatment in cohort 1, the amount of nicotine delivered from TNP (Dose) was proportional to surface area of TNP. Cmax and AUC of nicotine increased with the surface area (Dose), and tmax, t(1/2), CL/F and percentage of dose excreted in urine were almost the same between both treatments. These suggest the linear pharmacokinetics of nicotine in proportion to the surface area and Dose following single application of TNP in identical subjects. In cohort 2, the plasma nicotine concentrations after TNP-30x1 treatment were approximately half those just before each smoking.

Effects of low- and high-nicotine cigarette smoking on mood states and the HPA axis in men

The acute effects of smoking a low- or high-nicotine cigarette on hypothalamic-pituitary-adrenal (HPA) hormones, subjective responses, and cardiovascular measures were studied in 20 healthy men who met American Psychiatric Association Diagnostic and Statistical Manual IV criteria for nicotine dependence. Within four puffs (or 2 min) after cigarette smoking began, plasma nicotine levels and heart rate increased significantly (P<0.01), and peak ratings of 'high' and 'rush' on a Visual Analogue Scale were reported. Reports of 'high', 'rush', and 'liking' and reduction of 'craving' were significantly greater after smoking a high-nicotine cigarette than a low-nicotine cigarette (P<0.05). Peak plasma nicotine levels after high-nicotine cigarette smoking (23.9+/-2.6 ng/ml) were significantly greater than after low-nicotine cigarette smoking (3.63+/-0.59 ng/ml) (P<0.001). After smoking a low-nicotine cigarette, adrenocorticotropin hormone (ACTH), cortisol, dehydroepiandrosterone (DHEA), and epinephrine did not change significantly from baseline. After high-nicotine cigarette smoking began, plasma ACTH levels increased significantly above baseline within 12 min and reached peak levels of 21.88+/-5.34 pmol/l within 20 min. ACTH increases were significantly correlated with increases in plasma nicotine (r=0.85; P<0.0001), DHEA (r=0.66; P=0.002), and epinephrine (r=0.86; P<0.0001). Cortisol and DHEA increased significantly within 20 min (P<0.05) and reached peak levels of 424+/-48 and 21.13+/-2.55 ng/ml within 60 and 30 min, respectively. Thus cigarette smoking produced nicotine dose-related effects on HPA hormones and subjective and cardiovascular measures. These data suggest that activation of the HPA axis may contribute to the abuse-related effects of cigarette smoking.

La evolución del concepto de tabaquismo

El concepto de tabaquismo ha evolucionado mucho en las últimas décadas. De hábito en los años 60, el consumo pasó a ser considerado como dependencia psicológica en los años 70, después como adicción en los 80 y en los años 90 se instauró la clínica del fumador. Para entender el mecanismo del hábito de fumar debemos considerar que fumar representa mucho más que la dependencia física a la nicotina. Con el paso del tiempo el fumador pasa a recibir estímulos sociales, comportamentales o culturales que refuerzan su hábito y probablemente serán los elementos causantes del establecimiento de la dependencia psicológica. Tanto el componente psicológico como el físico de la dependencia al tabaco tienen un papel fundamental en el mantenimiento del hábito.

A fatal poisoning caused by methomyl and nicotine

A 35-year-old male was found lying in a prone position in his room. He was in cardiopulmonary arrest on arrival to hospital and was pronounced dead. There was no attempt at resuscitation. No miosis was observed on admission. At post-mortem his stomach contained 170 g greenish liquid with a small amount of shredded tobacco leaves. The serum cholinesterase activities were 47-90 IU (normal range for male: 200-440 IU). GC and GC-MS analyses showed nicotine (21.8 mg), methomyl (304 mg), and triazolam (1.69 mg) in his stomach. He had consumed tobacco leaves, Lannate containing water soluble methomyl (45%), and Halcion tablets containing 0.25 mg triazolam. Methomyl concentrations in blood were 3-8 ng/ml. Substantial amounts of methomyl (2260-2680 ng/ml) were detected in cerebrospinal fluid and vitreous humor. Nicotine concentrations in blood ranged from 222 to 733 ng/ml. A small amount of triazolam was detected only in bile (176 ng/ml) and liver (23 ng/g). The cause of death was respiratory paralysis produced by the additive effects of methomyl and nicotine shortly after consumption.

Brain Uptake Kinetics of Nicotine and Cotinine after Chronic Nicotine Exposure

Blood-brain barrier (BBB) nicotine transfer has been well documented in view of the fact that this alkaloid is a cerebral blood flow marker. However, limited data are available that describe BBB penetration of the major tobacco alkaloids after chronic nicotine exposure. This question needs to be addressed, given long-term nicotine exposure alters both BBB function and morphology. In contrast to nicotine, it has been reported that cotinine (the major nicotine metabolite) does not penetrate the BBB, yet cotinine brain distribution has been well documented after nicotine exposure. Surprisingly, therefore, the literature indirectly suggests that central nervous system cotinine distribution occurs secondarily to nicotine brain metabolism. The aims of the current report are to define BBB transfer of nicotine and cotinine in naive and nicotine-exposed animals. Using an in situ brain perfusion model, we assessed the BBB uptake of [3H]nicotine and [3H]cotinine in naive animals and in animals exposed chronically to S-(-)nicotine (4.5 mg/kg/day) through osmotic minipump infusion. Our data demonstrate that 1) [3H]nicotine BBB uptake is not altered in the in situ perfusion model after chronic nicotine exposure, 2) [3H]cotinine penetrates the BBB, and 3) similar to [3H]nicotine, [3H]cotinine BBB transfer is not altered by chronic nicotine exposure. To our knowledge, this is the first report detailing the uptake of nicotine and cotinine after chronic nicotine exposure and quantifying the rate of BBB penetration by cotinine.

Automated 96-well liquid–liquid back extraction liquid chromatography–tandem mass spectrometry method for the determination of ABT-202 in human plasma

A high-throughput bioanalytical method using automated sample transferring, automated liquid-liquid back extraction and liquid chromatography-tandem mass spectrometry was developed in a GLP regulated environment for the determination of ABT-202 in human plasma. Samples of 0.30 ml were transferred into 96-well plate using an automatic liquid handler. Automated liquid-liquid extraction (LLE) was carried out on a 96-channel programmable liquid handling workstation using methyl tert-butyl ether as the extraction solvent. A dual-HPLC with single mass spectrometer configuration was utilized to provide a reliable and routine means to increase sample throughput. The standard curve range was 0.38-95.02 ng/ml. There was no interference from endogenous components in the blank plasma tested. The accuracy (% bias) at the lower limit of quantitation (LLOQ) was 7.7% and the precision (% CV) for samples at the LLOQ was 4.7%. The inter-day % CV and % bias of the quality control samples were < or = 6.8 and < or = 7.6%, respectively. Coefficients of determination, a measure of linearity, ranged from 0.994 to 0.997. The method was accurate and reproducible and was successfully applied to generate plasma concentration-time profiles for human subjects after low oral doses of the compound.

Changes in craving for a cigarette and arterial nicotine plasma concentrations in abstinent smokers

Although the relationship between nicotine and changes in heart rate and blood pressure has been demonstrated, the relationship between nicotine and subjective effects such as decreased craving, relaxation, sickness, and decreased nervousness, is less well delineated. In this study, arterial nicotine levels were drawn in 21 smokers who smoked two average nicotine (AN) cigarettes and one low nicotine (LN) cigarette. Craving for a cigarette, relaxation, sickness, and decreased nervousness were rated on a visual analog scale (VAS) before and after smoking each cigarette. None of these subjective measures except craving for a cigarette was changed significantly by smoking. The change in craving was significantly correlated with the area under the plasma nicotine concentration versus time curve (r = -0.57, p = 0.01) calculated from the arterial nicotine samples drawn up to 20 min after the initiation of smoking the first AN cigarette. Although well-documented behavioral manipulations, such as smoking denicotinized cigarettes, reduce craving, increases in plasma arterial nicotine concentrations after smoking the first cigarette of the day also reduce craving. Both the psychology and pharmacology of nicotine/tobacco smoking are involved in craving reduction.

Effects of nicotine on cognitive deficits in schizophrenia

Several lines of evidence suggest a pathophysiological role for nicotinic receptors in schizophrenia. Activation by nicotine alters physiological dysfunctions, such as eye movement and sensory gating abnormalities, but effects on neuropsychological performance are just beginning to be investigated. Nicotine-induced desensitization and the well-known tachyphylaxis of nicotinic receptors may confound such efforts. In all, 20 schizophrenics, 10 smokers, and 10 nonsmokers were assessed following the administration of nicotine gum and placebo gum. The Repeatable Battery for the Assessment of Neuropsychological Status was administered. Nicotine affected only the Attention Index; there were no effects on learning and memory, language, or visuospatial/constructional abilities. Attentional function was increased in nonsmokers, but decreased in nicotine-abstinent smokers after nicotine administration. The effects of nicotine in schizophrenia do not extend to all areas of cognition. Effects on attention may be severely limited by tachyphylaxis, such that decremented performance occurs in smokers, while modest effects may be achieved in nonsmokers.

Nicotine effects on brain function and functional connectivity in schizophrenia

BACKGROUND

Nicotine in tobacco smoke can improve functioning in multiple cognitive domains. High rates of smoking among schizophrenic patients may reflect an effort to remediate cognitive dysfunction. Our primary aim was to determine whether nicotine improves cognitive function by facilitating activation of brain regions mediating task performance or by facilitating functional connectivity.

METHODS

Thirteen smokers with schizophrenia and 13 smokers with no mental illness were withdrawn from tobacco and underwent functional magnetic resonance imaging (fMRI) scanning twice, once after placement of a placebo patch and once after placement of a nicotine patch. During scanning, subjects performed an n-back task with two levels of working memory load and of selective attention load.

RESULTS

During the most difficult (dichotic 2-back) task condition, nicotine improved performance of schizophrenic subjects and worsened performance of control subjects. Nicotine also enhanced activation of a network of regions, including anterior cingulate cortex and bilateral thalamus, and modulated thalamocortical functional connectivity to a greater degree in schizophrenic than in control subjects during dichotic 2-back task performance.

CONCLUSIONS

In tasks that tax working memory and selective attention, nicotine may improve performance in schizophrenia patients by enhancing activation of and functional connectivity between brain regions that mediate task performance.

Regional cerebral blood flow and plasma nicotine after smoking tobacco cigarettes

The hypothesis for this research is that only in some brain areas, regional cerebral blood flow (rCBF) after tobacco smoking is correlated with arterial plasma nicotine concentrations. Twenty-one healthy adult tobacco smokers of both genders were studied after overnight tobacco abstinence. H(2)15O water was used to measure rCBF. Six separate scans were taken about 12 min apart with the subjects' eyes closed and relaxed. Research tobacco cigarettes smoked were of average (1.0 mg) and low (0.08 mg) nicotine but similar tar yield (9.5 and 9.1 mg). Increases in normalized rCBF were obtained in the occipital cortex, cerebellum, and thalamus, and decreases in the anterior cingulate, nucleus accumbens, amygdala, and hippocampus immediately after smoking the first average nicotine yield cigarette of the morning. After smoking the second average nicotine yield cigarette, the effects were less than smoking the first. Low-nicotine cigarettes produced fewer changes in rCBF than those after the first average cigarette. As expected, statistically significant correlations were found between increases in arterial plasma nicotine and HR. Correlations with arterial nicotine on rCBF were statistically significant in brain areas with the greatest changes in relative blood flow such as the cerebellum and occipital cortex. Nicotine delivery by tobacco smoking is only one of the factors, which contribute to changes in rCBF.

Lack of efficacy of a nicotine transdermal treatment on motor and cognitive deficits in Parkinson's disease

Studies assessing the efficacy of nicotine in Parkinson's disease (PD) have generated contradictory results. The controversy seems to stem from uncontrolled factors including the lack of objective measures, the practice effect in a test-retest design, and the absence of plasmatic dosage. This study aimed at further controlling these factors using transdermal nicotine in PD.

METHODS

Twenty-two nonsmoking PD patients received a transdermal nicotine treatment over 25 days in increasing titrated doses. Motor and cognitive assessments were carried out on days 11 and 25 (low-dose and high-dose assessments, respectively) and after a 14-day washout period.

RESULTS

Patients tolerated nicotine poorly. Thirteen (59%) withdrew, mostly because of acute side effects. In the remaining nine patients, nicotine neither improved nor worsened motor or cognitive functioning in comparison with 10 age, gender and education matched controls.

CONCLUSIONS

Transdermal nicotine is not effective in treating motor and cognitive deficits in PD. The results obtained with our objective measures confirm a recent double-blind, placebo-controlled study that used clinical measures. It is possible that nicotine lacks specificity in targeting critical nicotinic receptors that might be involved in PD pathophysiology. The low tolerability may be related to such a lack of specificity of nicotine, which would directly stimulate the autonomic nervous system.

Effects of nicotine infusion on the metabolism of the tobacco carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in rats

The tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a lung carcinogen in the rat and believed to be a causative agent for lung cancer in smokers. To exert its carcinogenic potential NNK is metabolically activated by cytochrome P450-catalyzed alpha-hydroxylation. Nicotine and NNK share metabolic pathways. The purpose of this study was to determine whether nicotine alters the fraction of NNK undergoing activation to carcinogenic metabolites. Rats received acute (36 h) or chronic (2 week) s.c. infusions of nicotine at rates producing serum nicotine concentrations 2-3 times the usual venous nicotine concentrations measured in smokers. A single dose of [5-3H]-NNK was administered i.p. 24 h prior to the end of each infusion. Urine was collected for 24 h thereafter and NNK metabolites quantified by radioflow HPLC. Neither acute nor chronic nicotine infusion had any effect on the extent of NNK metabolism by alpha-hydroxylation. These data suggest that nicotine infusion, at rates simulating the higher doses of nicotine replacement therapy now being studied for smoking cessation, neither induces nor inhibits NNK metabolism appreciably and therefore should not alter the formation of carcinogenic NNK metabolites.

Use of nicotine patches in breast-feeding mothers: transfer of nicotine and cotinine into human milk

OBJECTIVE

Our objective was to assess the extent of exposure to nicotine and cotinine in breast-fed infants during maternal smoking and later during maternal use of the nicotine transdermal patch to achieve smoking cessation.

METHODS

Fifteen lactating women (mean age, 32 years; mean weight, 72 kg) who were smokers (mean of 17 cigarettes per day) participated in a trial of the nicotine patch to assist in smoking cessation. Serial milk samples were collected from the women over sequential 24-hour periods when they were smoking and when they were stabilized on the 21-mg/d, 14-mg/d, and 7-mg/d nicotine patches. Nicotine and cotinine in milk were quantified by HPLC, and infant dose was calculated. Plasma concentrations of nicotine in the breast-fed infants were assessed, and the infants were also clinically assessed.

RESULTS

Nicotine and cotinine concentrations in milk were not significantly different between smoking (mean of 17 cigarettes per day) and the 21-mg/d patch, but concentrations were significantly lower (P <.05) when patients were using the 14-mg/d and 7-mg/d patches than when smoking. There was also a downward trend in absolute infant dose (nicotine equivalents) from smoking or the 21-mg patch through to the 14-mg and 7-mg patches (P <.05 at both 14-mg and 7-mg doses, compared with smoking). Milk intake (shown as median and 25th to 75th percentile) by the breast-fed infants was similar while their mothers were smoking (585 mL/d [507-755 mL/d]) and subsequently when their mothers were using the 21-mg (717 mL/d [504-776 mL/d]), 14-mg (731 mL/d [535-864 mL/d]), and 7-mg (619 mL/d [520-706 mL/d]) patches (chi(2) = 3.19, P =.364).

CONCLUSIONS

We conclude that the absolute infant dose of nicotine and its metabolite cotinine decreases by about 70% from when subjects were smoking or using the 21-mg patch to when they were using the 7-mg patch. In addition, use of the nicotine patch had no significant influence on the milk intake by the breast-fed infant. Undertaking maternal smoking cessation with the nicotine patch is, therefore, a safer option than continued smoking.

In vivo pharmacological characterization of (+/-)-4-[2-(1-methyl-2-pyrrolidinyl)ethyl]thiophenol hydrochloride (SIB-1553A), a novel cholinergic ligand: microdialysis studies

SIB-1553A ((+/-)-4-[2-(1-methyl-2-pyrrolidinyl)ethyl]thiophenol HCl) is a neuronal nicotinic acetylcholine receptor (nAChR) ligand which is active in rodent and primate models of cognition. In functional assays, SIB-1553A exhibits marked subtype selectivity for nAChRs as compared to nicotine. In addition SIB-1553A also exhibits affinities to histaminergic (H3) and serotonergic (5-HT1 and 5HT2) receptors and sigma binding sites. In the present investigation, we characterized SIB-1553A-induced neurotransmitter release in vivo. Following subcutaneous injection (s.c., 10 mg/kg), SIB-1553A rapidly entered the brain achieving concentration of approximately 20 microM 15 min post-injection and was eliminated from plasma with a terminal half-life of approximately 32 min. In freely moving rats, SIB-1553A (1-40 mg/kg, s.c.), markedly increased ACh release in the hippocampus and prefrontal cortex. In both regions, the magnitude of SIB-1553A-induced ACh release was greater than that seen with the prototypical nAChR agonist, nicotine (0.4 mg/kg, s.c.). Both isomers of SIB-1553A induced similar levels of increase in hippocampal ACh release. Increased hippocampal ACh release was also observed following oral administration of SIB-1553A (40 mg/kg) or after local perfusion into the hippocampus (1 mM). SIB-1553A-induced hippocampal ACh release was significantly attenuated by two nAChR antagonists, mecamylamine (MEC) and dihydro-beta-erythroidine (DHbetaE), and by the dopamine (DA) (D1) antagonist, SCH-23390, arguing that ACh release, in part, involves activation of nAChRs and a permissive DA synapse. In contrast to its robust effects on ACh release, SIB-1553A (40 mg/kg, s.c.) modestly increased striatal DA release (approximately 180% of baseline). Due to the proposed role of cholinergic pathways in learning and memory, the neurochemical profile of SIB-1553A suggests a potential for it to treat cognitive dysfunction.

Effects of nicotine deprivation on urges to drink and smoke in alcoholic smokers

AIM

This study examined the effect of nicotine deprivation on alcohol and smoking urges in a sample of alcohol-dependent smokers in early recovery.

DESIGN

Using a within-subjects design, participants underwent two cue-reactivity laboratory sessions in which they rated their urges for alcohol and cigarettes during the following three trials: baseline, neutral cue and mood induction combined with alcohol beverage cue exposure. One session was completed after 34 hours of nicotine deprivation and another in a non-deprived state.

PARTICIPANTS

Forty alcohol-dependent heavy smokers recruited from a substance abuse day treatment program.

MEASUREMENTS

Self-reported urge to drink, urge to smoke and salivation.

FINDINGS

Results showed that during the non-deprived session, alcohol cue presentations were associated with significant increases in urges to drink and urges to smoke. Acute nicotine deprivation led to increased smoking urges, but was not associated with increased urges to drink alcohol.

CONCLUSIONS

Findings suggest that the acute effects of smoking cessation are unlikely to increase risk of relapse to alcohol in alcoholic patients who are undergoing treatment.

Two week nicotine treatment selectively increases bone vascular constriction in response to norepinephrine

This study was designed to determine if nicotine treatment alters the constrictor and/or dilator function of the vessels which regulate blood flow to intact bone. Nicotine (1.7 mg/kg/day) or nicotine-free, phosphate-buffered saline was administered subcutaneously to mature male rats for 2 weeks via osmotic mini-pumps. On the 14th day, the rats were anesthetized and in vivo experiments were performed to quantitate the changes in arterial blood pressure and perfusion of the intact tibia (measured by laser Doppler flowmetry) in response to two constrictor agonists (norepinephrine, NE and arginine vasopressin, AVP) and two vasodilator agents (acetylcholine, ACh and sodium nitroprusside, SNP). Dose-response curves were generated by plotting the change in the bone vascular resistance index (mmHg/bone perfusion units) evoked by each dose of agonist. In addition, bone arteriolar expression of endothelial nitric oxide synthase protein was quantitated by Western blot analysis. Nicotine treatment significantly enhanced the constriction of the bone vasculature in response to NE, but not to AVP. Vascular dilation in response to ACh and SNP was not changed by nicotine. These results indicate that nicotine selectively accentuates the constrictor response of the bone vasculature to exogenous NE. This enhanced constriction to NE is not due to impaired endothelial cell release of nitric oxide or diminished smooth muscle response to nitric oxide. Since NE and AVP activate similar cell signaling mechanisms to induce constriction, the selective enhancement of NE-induced constriction suggests that nicotine alters a mechanism unique to NE signaling; possibly the number or binding affinity of alpha adrenergic receptors. Since endogenous NE regulates basal blood flow to bone, the effect of nicotine to augment NE-induced constriction could lead to a chronic reduction in blood flow to bone.

Adrenal-mediated rather than direct effects of nicotine as a basis of altered sex steroid synthesis in fetal and neonatal rat

Prenatal nicotine interferes with rat sexual brain differentiation and may influence human puberty. We studied effects of nicotine and cotinine on perinatal steroid synthesis in offspring of time-pregnant rats. In vitro, cotinine inhibited testosterone synthesis in neonatal rat testis. Both compounds inhibited the brain aromatase of gestational day (GD) 19 male fetuses. Effective concentrations were higher than levels in maternal plasma and fetal tissue at GD 19 after nicotine treatment from GD 12, even though nicotine accumulated in fetal brain. In view of a dual effect of nicotine in male GD 18 fetuses, decreasing plasma testosterone and increasing corticosterone [Dev Brain Res 1991;62:23-31], we administered metyrapone on GD 17 to nicotine-treated dams. 11beta-Hydroxylase inhibition completely reversed the nicotine-induced reduction of plasma testosterone at GD 18. POMC mRNA in anterior pituitary of nicotine-exposed GD 18 fetuses was reduced, probably as a result of corticosterone feedback. These data reveal a novel type of interaction of nicotine with the fetal gonadal axis involving the adrenal.

Acute effects of Advance: a potential reduced exposure product for smokers

OBJECTIVE

To examine the acute effects of Advance, a potential reduced exposure product (PREP) for smokers marketed as a means to reduce exposure to toxic gases and tobacco specific nitrosamines.

DESIGN, SETTING, PARTICIPANTS

Latin square ordered, three condition, laboratory based, crossover design with 20 smokers of light or ultra-light cigarettes (15 or more cigarettes/day). In each 2.5 hour condition, participants completed an 8-puff smoking bout from their own brand, Advance, or an unlit cigarette (that is, sham smoking) every 30 minutes for a total of four bouts.

MAIN OUTCOME MEASURES

Subject rated measures of tobacco/nicotine withdrawal; carbon monoxide (CO), and heart rate; plasma nicotine concentrations.

RESULTS

Relative to own brand, Advance produced similar withdrawal suppression and heart rate increase, lower CO boost, and higher plasma nicotine concentrations.

CONCLUSIONS

PREPs for smokers need to be evaluated using a comprehensive strategy that includes empirical examination of acute and long term effects. Adequate withdrawal suppression and potentially lower concentrations of CO associated with Advance use are positive factors, although higher nicotine concentrations do not constitute "reduced exposure". Overall, longer exposure periods are necessary to determine carcinogen delivery. PREP evaluation is complex and should be completed objectively.

Correlation and predictive performances of saliva and plasma nicotine concentration on tobacco withdrawal-induced craving

AIMS

To investigate whether saliva is a useful alternative to plasma for routine monitoring of nicotine and evaluate the predictive performances of saliva and plasma concentration on craving estimated by a Tiffany Questionnaire on Smoking Urge-Brief Form.

METHODS

Thirteen healthy smokers were enrolled in a randomized, two period, crossover trial. Linear and power models were evaluated to predict the plasma nicotine concentrations from the saliva measurements, whereas a population PK/PD indirect response model was used to predict craving using either saliva or plasma nicotine concentration as the independent variable.

RESULTS

The results of the analysis revealed that the power model was preferred over the linear one. The bias on the predicted plasma concentrations was of 0.47 ng ml-1 with a 95% confidence interval of [-0.57, 1.52] and a precision of 5.68 ng ml-1. The placebo effect model was initially fitted to data, then the indirect response approach (with inhibition in k(in)) was used to model the craving scores using plasma and saliva nicotine concentrations as independent variables. The two indirect response PK/PD models based on saliva and plasma nicotine concentrations, adequately described the onset, extent, and duration of craving. The maximal inhibition I(max) was 0.722 and 1 for saliva and plasma concentrations while the estimated nicotine concentrations giving 50% of the maximal inhibition were 269 ng ml-1 and 24.3 ng ml-1 for saliva and plasma, respectively.

CONCLUSIONS

A good correlation between plasma and saliva nicotine concentrations has been found using a power model. Comparable values of bias and precision on the model-predicted craving indicate that plasma and saliva concentration can equally well be used to predict the onset of tobacco withdrawal induced craving. Analysis of saliva definitely offers a potentially more attractive way to assess nicotine concentration values, as samples can be collected easily and noninvasively. In addition, saliva sampling avoids the pain and discomfort involved in venepuncture. In studies that assess psychological measures, such as subjective mood, blood collection could present a possible confounding factor because of the anxiety and pain that accompanies it. For these reasons saliva can reasonably be considered as the ideal sampling site for all clinical studies conducted for the evaluation of the potential activity of drugs on nicotine deprivation symptoms.

Acute effects of cigarettes in non-deprived smokers on memory, calculation and executive functions

To determine whether smoking one or two cigarettes daily has effects on cognitive functions and the blood nicotine level, we examined 20 smokers and 20 nonsmokers as part of a normal daily smoking regimen using psychological tests for memory, calculation and association. Subjects underwent Buschke's selective reminding test, a mental arithmetic task (multiplication between two digits and one digit) and an association task (letter fluency); the duration of each task being 2 min under the condition of pre-smoking, one cigarette smoking and two cigarette smoking sessions, with an inter-session interval of 50 min. The total recall or correct responses were evaluated. The results showed that performance deteriorated in the later sessions in the memory task, whereas it improved in the later sessions in the calculation and association tasks, with no group (smoker-nonsmoker) difference, nor interaction between tasks and groups in each task. Plasma nicotine increased by 10 ng/ml immediately after smoking a cigarette, and 14 ng/ml immediately after smoking two cigarettes, but decreased to the pre-smoking level or slightly higher 10 min after smoking. These findings suggested that a daily dose of nicotine had little effect on the performance related to memory, calculation and mental association.