Chronic ethanol or nicotine treatment results in partial cross-tolerance between these agents

Alcohol and the dopamine system

The mesolimbic dopamine pathway plays a major role in drug reinforcement and is likely involved also in the development of drug addiction. Ethanol, like most addictive drugs, acutely activates the mesolimbic dopamine system and releases dopamine, and ethanol-associated stimuli also appear to trigger dopamine release. In addition, chronic exposure to ethanol reduces the baseline function of the mesolimbic dopamine system. The molecular mechanisms underlying ethanol´s interaction with this system remain, however, to be unveiled. Here research on the actions of ethanol in the mesolimbic dopamine system, focusing on the involvement of cystein-loop ligand-gated ion channels, opiate receptors, gastric peptides and acetaldehyde is briefly reviewed. In summary, a great complexity as regards ethanol´s mechanism(s) of action along the mesolimbic dopamine system has been revealed. Consequently, several new targets and possibilities for pharmacotherapies for alcohol use disorder have emerged.

The impact of adolescent nicotine exposure on alcohol use during adulthood: The role of neuropeptides

Nicotine and alcohol abuse and co-dependence represent major public health crises. Indeed, previous research has shown that the prevalence of alcoholism is higher in smokers than in non-smokers. Adolescence is a susceptible period of life for the initiation of nicotine and alcohol use and the development of nicotine-alcohol codependence. However, there is a limited number of pharmacotherapeutic agents to treat addiction to nicotine or alcohol alone. Notably, there is no effective medication to treat this comorbid disorder. This chapter aims to review the early nicotine use and its impact on subsequent alcohol abuse during adolescence and adulthood as well as the role of neuropeptides in this comorbid disorder. The preclinical and clinical findings discussed in this chapter will advance our understanding of this comorbid disorder's neurobiology and lay a foundation for developing novel pharmacotherapies to treat nicotine and alcohol codependence.

Predictors of tobacco and alcohol co-use from ages 15 to 32: The Amsterdam Growth and Health Longitudinal Study

Tobacco and alcohol are often used in tandem over time, but specific predictors of course and patterns of course over time need explication. We examined differences in alcohol and tobacco course among an adolescent population as they transitioned into young adulthood across a 17-year period. Data came from participants (n = 303 for ages 15-21, n = 196 for ages 21 to 32; 52% female and 54% female, respectively) enrolled in the Amsterdam Growth and Health Longitudinal Study, an epidemiologic investigation examining disease across the life span. We utilized parallel latent growth modeling to assess the impact of sex, personality traits, cholesterol, blood pressure, and body mass index (BMI), on initial status and linear change over time in course of tobacco and alcohol. Females reported less alcohol use at adolescent baseline (β = -21.79), less increase during adolescence (β = -7.92, p < .05), slower decrease during young adulthood (β = 4.67, p < .05), and more rapid decline in tobacco use during young adulthood (β = -70.85, p < .05), relative to males. Alcohol and tobacco use baseline status' and change over time were all significantly associated with one another during both adolescence and young adulthood (p < .05; aside from alcohol baseline and slope during young adulthood). Effects of BMI, cholesterol, blood pressure, and personality traits were also observed on tobacco and alcohol course. In light of the strong, but sex dependent relationship between alcohol and tobacco course, particularly from ages 15 to 21, prevention efforts to curb heavy alcohol and tobacco use should consider targeting course taking into account biological sex and other notable covariates. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Lobeline attenuates ethanol abstinence-induced depression-like behavior in mice

Evidence indicates that the brain nicotinic acetylcholine receptor (nAChRs) ligand lobeline reduces depression-like behaviors, ethanol drinking, and nicotine withdrawal-induced depression-like behaviors. The purpose of the present study was to determine the effects of lobeline on ethanol abstinence-induced depression-like behavior and associated neuroadaptive changes in mice. Adult C57BL/6J male mice were allowed to drink 10% ethanol for 4 weeks using a two-bottle choice procedure. Mice were tested after 24 h and 14 days of ethanol abstinence in a forced swim test (FST), a measure for depression-like behavior. Acute lobeline treatment (1 mg/kg) significantly reduced immobility time compared to controls after 24 h and 14 days of abstinence. In addition, abstinence from chronic ethanol exposure reduced serotonin levels in the hippocampus, which was reversed by acute lobeline treatment. Repeated lobeline treatment (1 mg/kg, once daily) for 14 days during ethanol abstinence also significantly reduced FST immobility in mice exposed to ethanol. Chronic ethanol exposure significantly reduced the number of 5-bromo 2'-deoxyuridine (BrdU)-positive cells in the dentate gyrus of the hippocampus, indicating decreased hippocampal cell proliferation. Abstinence from chronic ethanol exposure also decreased brain-derived neurotrophic factor (BDNF) in the dentate gyrus and CA3 region of the hippocampus. In contrast, repeated lobeline treatment significantly increased both BrdU- and BDNF-positive cells. Taken together, our results indicate that lobeline produced antidepressant-like effects, likely by targeting brain β2-containing nAChRs, serotonergic neurotransmission, and/or hippocampal cell proliferation. Therefore, lobeline may have therapeutic utility to treat alcohol abstinence-induced depression.

Psychopharmacology of Tobacco and Alcohol Comorbidity: a Review of Current Evidence

Purpose of the Review

Comorbidity of alcohol and tobacco use is highly prevalent and may exacerbate the health effects of either substance alone. However, the mechanisms underlying this comorbidity are not well understood. This review will examine the evidence for shared neurobiological mechanisms of alcohol and nicotine comorbidity and experimental studies of the behavioural consequences of these interactions.

Recent Findings

Studies examining the shared neurobiology of alcohol and nicotine have identified two main mechanisms of comorbidity: (1) cross-reinforcement via the mesolimbic dopamine pathway and (2) cross-tolerance via shared genetic and nAChR interaction. Animal and human psychopharmacological studies demonstrate support for these two mechanisms of comorbidity.

Summary

Human behavioural studies indicate that (1) alcohol and tobacco potentiate each other’s rewarding effects and (2) nicotine reduces the sedative and intoxication effects of alcohol. Together, these findings provide a strong evidence base to support the role of the cross-reinforcement and cross-tolerance as mechanisms underlying the comorbidity of alcohol and tobacco use. Methodological concerns in the literature and recommendations for future studies are discussed alongside implications for treatment of comorbid alcohol and tobacco use.

Tolerance to Ethanol or Nicotine Results in Increased Ethanol Self-Administration and Long-Term Depression in the Dorsolateral Striatum

Ethanol (EtOH) and nicotine are the most widely coabused drugs. Tolerance to EtOH intoxication, including motor impairment, results in greater EtOH consumption and may result in a greater likelihood of addiction. Previous studies suggest that cross-tolerance between EtOH and nicotine may contribute to the abuse potential of these drugs. Here we demonstrate that repeated intermittent administration of either EtOH or nicotine in adult male Sprague Dawley rats results in tolerance to EtOH-induced motor impairment and increased EtOH self-administration. These findings suggest that nicotine and EtOH cross-tolerance results in decreased aversive and enhanced rewarding effects of EtOH. Endocannabinoid signaling in the dorsolateral striatum (DLS) has been implicated in both EtOH tolerance and reward, so we investigated whether nicotine or EtOH pretreatment might modulate endocannabinoid signaling in this region. Using similar EtOH and nicotine pretreatment methods resulted in increased paired-pulse ratios of evoked EPSCs in enkephalin-positive medium spiny neurons in DLS slices. Thus, EtOH and nicotine pretreatment may modulate glutamatergic synapses in the DLS presynaptically. Bath application of the CB1 receptor agonist Win 55,2-212 increased the paired-pulse ratio of evoked EPSCs in control slices, while Win 55,2-212 had no effect on paired-pulse ratio in slices from either EtOH- or nicotine-pretreated rats. Consistent with these effects, nicotine pretreatment occluded LTD induction by high-frequency stimulation of the corticostriatal inputs to the dorsolateral striatum. These results suggest that nicotine and EtOH pretreatment modulates striatal synapses to induce tolerance to the motor-impairing effects of EtOH, which may contribute to nicotine and EtOH coabuse.

Pharmacological Options for Smoking Cessation in Heavy-Drinking Smokers

There is a high prevalence of comorbid tobacco use and alcohol use disorder (AUD), affecting more than 6 million people in the US. Globally, tobacco and alcohol use rank fourth and fifth, respectively, for disability-adjusted life-years lost. Levels of alcohol use are higher in smokers than nonsmokers, and the prevalence of smoking is higher in heavy drinkers compared with nondrinkers. This relationship is driven by many different factors, including genetics, neurobiological mechanisms, conditioning processes, and psychosocial influences. Although this unique population tends to experience more negative health consequences, more severe AUD, and poorer response to treatment than those with either AUD or tobacco use disorder alone, there are currently no available treatment protocols tailored to this comorbid condition. In this review, we provide a comprehensive review of ongoing clinical research into smoking cessation options for heavy-drinking smokers (HDS) through an evaluation of the effect of promising novel pharmacotherapies as well as combination therapies, including varenicline, naltrexone, the combination of varenicline and naltrexone, and the combination of naltrexone and nicotine replacement therapy (NRT). These treatments are considered in light of the standard of care for smoking cessation, and seek to improve upon the available guidelines for this sizeable subgroup of smokers, namely those smokers who drink heavily.

Varenicline and neuronal nicotinic acetylcholine receptors: a new approach to the treatment of co-occurring alcohol and nicotine addiction?

BACKGROUND AND OBJECTIVES

Alcohol and nicotine dependence are serious public health problems worldwide. They are associated with substantial morbidity and mortality, as well as adverse social effects and increased healthcare costs. Although efficacious treatments are available for these disorders, additional therapeutic options are required to ensure greater treatment utilization. In this paper, we describe the empirical basis on which varenicline, a nicotinic partial agonist approved for smoking cessation, may also have utility in the treatment of alcohol addiction.

METHODS

We sought to identify papers examining nicotine dependence, alcohol dependence, smoking, alcohol, and varenicline for possible inclusion in the present review. We identified over 600 papers through Pubmed/Medline, PsychINFO, and Google Scholar. We found 12 papers taking into consideration the following criteria: original language English, varenicline effect on alcohol consumption.

RESULTS

Animal studies have shown that varenicline reduces alcohol consumption. Two recent studies showed that varenicline also reduces alcohol consumption in humans. Both nicotine and alcohol interact with α4β2 and α3β4 nicotinic acetylcholine (ACh) receptors located in the ventral tegmental area of the brain, inducing dopamine (DA) release at the nucleus accumbens. Varenicline binds to nicotinic ACh receptors, where it has partial agonist effects, producing a moderate and constant level of DA release both in the mesolimbic pathway and in the prefrontal cortex.

CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE

Through these effects, varenicline may reduce alcohol craving, seeking, and consumption, in addition to promoting smoking cessation. Additional studies are needed to confirm the efficacy of varenicline in the treatment of alcohol dependence.

Neuronal nicotinic acetylcholine receptors: neuroplastic changes underlying alcohol and nicotine addictions

Addictive drugs can activate systems involved in normal reward-related learning, creating long-lasting memories of the drug's reinforcing effects and the environmental cues surrounding the experience. These memories significantly contribute to the maintenance of compulsive drug use as well as cue-induced relapse which can occur even after long periods of abstinence. Synaptic plasticity is thought to be a prominent molecular mechanism underlying drug-induced learning and memories. Ethanol and nicotine are both widely abused drugs that share a common molecular target in the brain, the neuronal nicotinic acetylcholine receptors (nAChRs). The nAChRs are ligand-gated ion channels that are vastly distributed throughout the brain and play a key role in synaptic neurotransmission. In this review, we will delineate the role of nAChRs in the development of ethanol and nicotine addiction. We will characterize both ethanol and nicotine's effects on nAChR-mediated synaptic transmission and plasticity in several key brain areas that are important for addiction. Finally, we will discuss some of the behavioral outcomes of drug-induced synaptic plasticity in animal models. An understanding of the molecular and cellular changes that occur following administration of ethanol and nicotine will lead to better therapeutic strategies.

Repeated exposure of the posterior ventral tegmental area to nicotine increases the sensitivity of local dopamine neurons to the stimulating effects of ethanol

Clinical evidence indicates a frequent co-morbidity of nicotine and alcohol abuse and dependence. The posterior ventral tegmental area (pVTA) appears to support the reinforcing and dopamine-stimulating effects of both drugs. The current study tested the hypothesis that repeated exposure of the pVTA to one drug would increase the sensitivity of local dopamine neurons to the stimulating effects of the other drug. Female Wistar rats received repeated daily microinjections of either 100 μM nicotine or vehicle directly into the pVTA for 7 days. On the 8th day, rats received microinjections of either vehicle or ethanol (100 or 200 mg%) into the pVTA while extracellular dopamine samples were collected from the ipsilateral nucleus accumbens shell (NACsh) with microdialysis. Another experiment tested the effects of challenge microinjections of 200 μM nicotine in the pVTA on extracellular dopamine levels in the NACsh following 7 daily pretreatments with 200 mg% ethanol in the pVTA. Nicotine pretreatments increased the dopamine-stimulating effects of ethanol in the pVTA (100 mg% ethanol: 115% vs 160% of baseline in the vehicle and nicotine groups, respectively, p < 0.05; 200 mg% ethanol: 145% vs 190% of baseline in the vehicle and nicotine groups, respectively, p < 0.05). In contrast, ethanol pretreatments did not alter the stimulating effects of nicotine in the pVTA. The results suggest that repeated exposure of the pVTA to nicotine increased the response of local dopamine neurons to the stimulating effects of ethanol, whereas repeated exposure of the pVTA to ethanol did not alter the responses of pVTA dopamine neurons to nicotine.

Positive and negative effects of alcohol and nicotine and their interactions: a mechanistic review

Nicotine and alcohol are two of the most commonly abused legal substances. Heavy use of one drug can often lead to, or is predictive of, heavy use of the other drug in adolescents and adults. Heavy drinking and smoking alone are of significant health hazard. The combination of the two, however, can result in synergistic adverse effects particularly in incidences of various cancers (e.g., esophagus). Although detrimental consequences of smoking are well established, nicotine by itself might possess positive and even therapeutic potential. Similarly, alcohol at low or moderated doses may confer beneficial health effects. These opposing findings have generated considerable interest in how these drugs act. Here we will briefly review the negative impact of drinking-smoking co-morbidity followed by factors that appear to contribute to the high rate of co-use of alcohol and nicotine. Our main focus will be on what research is telling us about the central actions and interactions of these drugs, and what has been elucidated about the mechanisms of their positive and negative effects. We will conclude by making suggestions for future research in this area.

Neuronal nicotinic acetylcholine receptors as pharmacotherapeutic targets for the treatment of alcohol use disorders

Alcohol use disorders (AUDs) are complex, and developing effective treatments will require the combination of novel medications and cognitive behavioral therapy approaches. Epidemiological studies have shown there is a high correlation between alcohol consumption and tobacco use, and the prevalence of smoking in alcoholics is as high as 80% compared to about 30% for the general population. Both preclinical and clinical data provide evidence that nicotine administration increases alcohol intake and non-specific nicotinic receptor antagonists reduce alcohol-mediated behaviors. As nicotine interacts specifically with the neuronal nicotinic acetylcholine receptor (nAChR) system, this suggests that nAChRs play an important role in the behavioral effects of alcohol. In this review, we discuss the importance of nAChRs for the treatment of AUDs and argue that the use of FDA approved nAChR ligands, such as varenicline and mecamylamine, approved as smoking cessation aids may prove to be valuable treatments for AUDs. We also address the importance of combining effective medications with behavioral therapy for the treatment of alcohol dependent individuals.

Nicotine: alcohol reward interactions

It is well established that the continued intake of drugs of abuse is reinforcing-that is repeated consumption increases preference. This has been shown in some studies to extend to other drugs of abuse; use of one increases preference for another. In particular, the present review deals with the interaction of nicotine and alcohol as it has been shown that smoking is a risk factor for alcoholism and alcohol use is a risk factor to become a smoker. The review discusses changes in the brain caused by chronic nicotine and chronic alcohol intake to approach the possible mechanisms by which one drug increases the preference for another. Chronic nicotine administration was shown to affect nicotine receptors in the brain, affecting not only receptor levels and distribution, but also receptor subunit composition, thus affecting affinity to nicotine. Other receptor systems are also affected among others catecholamine, glutamate, GABA levels and opiate and cannabinoid receptors. In addition to receptor systems and transmitters, there are endocrine, metabolic and neuropeptide changes as well induced by nicotine. Similarly chronic alcohol intake results in changes in the brain, in multiple receptors, transmitters and peptides as discussed in this overview and also illustrated in the tables. The changes are sex and age-dependent-some changes in males are different from those in females and in general adolescents are more sensitive to drug effects than adults. Although nicotine and alcohol interact-not all the changes induced by the combined intake of both are additive-some are opposing. These opposing effects include those on locomotion, acetylcholine metabolism, nicotine binding, opiate peptides, glutamate transporters and endocannabinoid content among others. The two compounds lower the negative withdrawal symptoms of each other which may contribute to the increase in preference, but the mechanism by which preference increases-most likely consists of multiple components that are not clear at the present time. As the details of induced changes of nicotine and alcohol differ, it is likely that the mechanisms of increasing nicotine preference may not be identical to that of increasing alcohol preference. Stimulation of preference of yet other drugs may again be different -representing one aspect of drug specificity of reward mechanisms.

The genetic components of alcohol and nicotine co-addiction: from genes to behavior

Co-occurrence of alcohol and nicotine addiction in humans is well documented and there is good evidence that common genes may contribute to both disorders. Although genetic factors contributing to tobacco and alcohol problem use have been well established through adoption, twin and family studies, specific genes remain to be identified and their mode of action elucidated. Recent work from human genetics studies has provided evidence that neuronal nicotinic acetylcholine receptors (nAChR) genes may have a role in mediating early behaviors that are risk factors for alcohol and nicotine dependence, such as age of initiation and early subjective responses to the drugs. Converging evidence suggests that the dopaminergic system is likely to be important in mediating the pleasurable feelings of reward when activated by nicotine and/or alcohol consumption. The nAChRs are important components of the dopaminergic reward system because some of the receptors have been shown to activate the release of dopamine, and mice lacking genes for specific nAChR gene subunits show altered behavioral responses to nicotine and alcohol. Furthermore, complex interactions between other neurotransmitter circuits including GABA, glutamate and serotonin may be modulated by nAChRs, leading researchers to study genes involved in neurobiology shared by different drugs. Future studies aimed at understanding the variation among these genes, and their corresponding functional implications, will help elucidate how natural variants in nicotinic receptor genes contribute to these common co-morbid disorders.

Smoking is a marker of risky behaviors independent of substance abuse in injured drivers

OBJECTIVE

Smoking has been linked to disease and injury. The purpose of this study is to investigate the smoking habits of motor vehicular driver trauma center patients and their association with previous injury history and risky behaviors.

METHODS

The studied population included 323 motor vehicular driver injury patients (123 smokers and 200 non-smokers) interviewed as part of a larger study of psychoactive substance use disorders at an adult Level I trauma center. Patients with head injuries, hospital stays of less than two days, and diminished cognition were excluded. Interviews included demographics (age, gender, race, marital status), socioeconomic status (SES; income, education, employment), risky behaviors (seatbelt non-use, drinking and driving, riding with drunk driver, binge drinking), and trauma history information (vehicular, assault, and other injuries). Substance abuse (alcohol and drug dependence) was evaluated in depth using DSM III-R criteria. Smokers and non-smokers were compared in relation to control and dependent variables using student's t test and chi-square (alpha = 0.05). Outcome variables included previous trauma history and risky behaviors. Multiple logistic regression models using step-down selection methods (alpha = 0.05) were constructed with risky behaviors and trauma history as dependent variables including demographics, SES and substance as independent variables.

RESULTS

Smokers represented 38 percent of the 323 patients studied. Smokers (n = 123) were younger (34 vs. 43 years), more likely to be male (72 percent vs. 50 percent), not married (72 percent vs. 56 percent), and had higher rates of alcohol (29 percent vs. 9 percent) and drug dependence (14 percent vs. 3 percent) than non-smokers (n = 200). Educational achievement (20 percent vs. 15 percent less than high school) and income level (24 percent vs. 23 percent with less than $15,000 of yearly income) were not different between smokers and non-smokers. Smokers were more likely than non-smokers to have a history of prior vehicular trauma (48 percent vs. 26 percent), assault (25 percent vs. 9 percent), or other injury (50 percent vs 37 percent). The following injury-prone behaviors were also more common among the smokers than non-smokers: seatbelt non-use (49 percent vs. 29 percent), drinking and driving (38 percent vs. 15 percent), riding with drunk driver (38 percent vs. 13 percent), and binge drinking (68 percent vs. 26 percent). In multiple logistic regression models adjusting for demographics, SES, and substance abuse, smoking revealed significantly higher odds ratios (OR) for the following dependent variables: seatbelt non-use (OR = 2.9), riding with drunk driver (OR = 2.2), binge drinking (OR = 2.4), previous vehicular (OR = 2.0), and assault injuries (OR = 2.5). Smoking did not reach significance for drinking and driving and other (non-vehicular and non-assault) injury.

CONCLUSION

Smoking is independently associated with risky behaviors and repeated history of vehicular or assault injury within the vehicular trauma population.

Chronic Ethanol Reduces Nicotine-Induced Dopamine Release in PC12 Cells

BACKGROUND

There is a high correlation between alcohol and nicotine use; that is, alcohol use is associated with high levels of smoking. One important aspect of nicotine addiction appears to be the activation of nicotinic acetylcholine receptors on dopaminergic neurons projecting from the ventral tegmental area to the nucleus accumbens. The release of dopamine from these neurons is thought to mediate, at least in part, the reward of nicotine consumption. If chronic alcohol consumption affects the amount of dopamine released in response to nicotine, it could contribute to the high level of smoking seen in alcoholics.

METHODS

We have used an in vitro model system to study the effects of chronic ethanol exposure on acute nicotine-induced dopamine release and the withdrawal from ethanol. A pheochromocytoma cell line (PC12 cells) was exposed to ethanol for periods of 3 to 96 hr, followed by a 5 min exposure to nicotine. Dopamine released in response to nicotinic stimulation was measured by high-pressure liquid chromatography.

RESULTS

Exposure of PC12 cells to chronic ethanol resulted in a time- and dose-dependent inhibition of nicotine-induced dopamine release. A moderate dose of ethanol (50 mM) resulted in a significant reduction in as little as 3 hr. The cells demonstrated a form of cross-tolerance in that they showed diminished response to nicotine even though they had never been exposed to nicotine. After ethanol was withdrawn from the cells after a chronic exposure (96 hr), dopamine release slowly returned to normal levels but demonstrated a significant period of "overshoot" or hyperresponsiveness between 24 and 48 hr after withdrawal.

CONCLUSIONS

These results show that chronic ethanol exposure decreases nicotine-induced dopamine release and demonstrate a period of hyperresponsiveness during withdrawal from ethanol. These studies suggest potential interactions between chronic ethanol and nicotine that may provide insight into such phenomena as cross-tolerance and increased use of nicotine by alcoholics.

Ethanol modulates nicotine-induced upregulation of nAChRs

The use of alcohol and nicotine are highly correlated, suggesting an underlying biochemical interaction. Chronic nicotine exposure results in a deactivation and subsequent upregulation of the expression of nicotinic acetylcholine receptors (nAChRs). Upregulation is thought to represent certain aspects of physical dependence on nicotine. If alcohol also alters nAChR expression or modulates the nicotine-induced upregulation, it could partially explain the high rate of co-abuse of these two drugs. We examined the effects of ethanol on the expression and nicotine-induced upregulation of nAChRs in two cell lines expressing different receptor subtypes. As measured by ligand binding, ethanol initially decreased nAChR expression in M10 cells but increased expression with a more chronic exposure. In the presence of nicotine, the effect of ethanol was similar; initially acting to blunt the upregulation of receptor expression caused by nicotine but enhancing the upregulation with 96 h of exposure. The upregulation of nAChRs was long lasting, remaining above control levels for as long as 7 days following removal of nicotine and ethanol. In PC12 cells, ethanol increased expression at all time points examined. A protein phosphatase inhibitor reduced nicotine-induced upregulation and a PKC inhibitor blocked the ethanol-induced decrease in nAChR expression. These data suggest that ethanol and nicotine interact at the level of the PKC pathway to regulate expression of nAChRs.

Induction of nicotine-metabolizing CYP2B1 by ethanol and ethanol-metabolizing CYP2E1 by nicotine: summary and implications

Alcohol and tobacco are frequently co-abused. Increased alcohol use and alcoholism are associated with smoking, and vice versa. Functional and/or metabolic cross-tolerance may contribute to this occurrence. This review summarizes recent studies published from our laboratory focusing on metabolic aspects of tolerance, which demonstrate that in rat, subchronic, behaviourally relevant doses of ethanol induce hepatic nicotine-metabolizing cytochrome P450 (CYP) 2B1, and that subchronically administered nicotine, at behaviourally relevant doses, induces hepatic ethanol-metabolizing CYP2E1. Increased CYP2B1 protein, mRNA and CYP2B1-mediated nicotine metabolism was observed following ethanol treatments. CYP2E1 protein and activity were induced by nicotine, but no changes were seen in levels of CYP2E1 mRNA. These data indicate that metabolic cross-tolerance may occur between nicotine and ethanol, suggesting that nicotine use may increase the elimination of ethanol, and ethanol use may increase the elimination of nicotine. Other implications, such as altered pharmacology and toxicology of drugs metabolized by these enzymes, as well as changes in pro-carcinogen and pro-toxin activation are also discussed.

Immediate antecedents of cigarette smoking: an analysis from ecological momentary assessment

The authors assessed the association between smoking and situational cues, including affect, in real-world contexts. Using ecological momentary assessment, 304 smokers monitored ad-lib smoking for 1 week, recording each cigarette on palm-top computers. Generalized estimating equations contrasted 10,084 smoking and 11,155 nonsmoking situations. After controlling for smoking restrictions, smoking was strongly related to smoking urges and modestly related to consumption of coffee and food, the presence of other smokers, and several activities. Smoking was unrelated to negative or positive affect or to arousal, although it was associated with restlessness. Thus, in daily life, affect appears to exert little influence over ad-lib smoking in heavy smoking adults.

Screening for health behaviors in ambulatory clinical settings: does smoking status predict hazardous drinking?

Although a link between alcohol consumption and smoking behavior is well documented, the majority of studies have focused on individuals dependent on both alcohol and nicotine. The present study examined the likelihood of hazardous drinking as a function of smoking status, gender, age, ethnicity, and education in a sample of 676 medical and dental patients whose drinking covered the spectrum from abstinence to high levels. We hypothesized that hazardous drinking would be more common among young, male respondents who were current smokers and that past smokers would show a risk of hazardous drinking that was intermediate between that of current smokers and nonsmokers. Results showed that younger age, fewer years of education, male gender, and current smoking status were significant predictors of hazardous drinking. However, there was no relationship between a past history of smoking and current risk of hazardous drinking. Evaluation of the Fagerstrom Tolerance Questionnaire (FTQ) showed that it was no more useful as a screening instrument than a single question that elicited current smoking status. These findings suggest that patients who report current smoking should routinely be asked about their current alcohol consumption. Interventions should then be tailored to address smoking and, if appropriate, hazardous drinking as well.

Prospective analysis of comorbidity: tobacco and alcohol use disorders

Alcohol use disorders (AUD) and tobacco use disorders (TD) frequently co-occur. The authors examined AUD-TD comorbidity over time using a state-trait (ST) model. The ST model represents variance in AUD/TD as a traitlike factor that spans measurement occasion and identifies distinct sources of variance in AUD-TD comorbidity. The ST model was evaluated on 450 young adults (baseline age = 18.5 years; 51% with family history of alcoholism) assessed 5 times over 7 years. The ST model demonstrated superior fit over a first-order autoregressive model. The tendency to diagnose with AUD and TD was partially explained by family history of alcoholism; this relationship was mediated by childhood stressors, alcohol expectancies, and behavioral undercontrol. Results supported a common third-variable influence (vs. directional) model of comorbidity. The ST model is an important conceptual and methodological approach to the prospective study of comorbidity in general.

Nicotinic mechanisms involved in the dopamine activating and reinforcing properties of ethanol

Ethanol shares with all major dependence producing drugs the ability to activate brain mesocorticolimbic dopamine neurons, an important part of the brain reward systems. This dopamine activation may be involved in mediating the positive reinforcing effects of ethanol. The mechanisms of action of ethanol in its activation of this dopamine system remain, however, to be elucidated. A selective pharmacological interference with these mechanisms may offer a possibility to reduce the reinforcing properties of ethanol without simultaneously interfering with the reinforcing properties of natural rewards. Ethanol has been shown to directly influence the function of various ligand-gated ion-channels. Several of these are located on or nearby mesocorticolimbic dopamine neurons. One such receptor is the nicotinic acetylcholine receptor (nAChR). The present article reviews a series of investigations aimed at investigating whether nAChRs are involved in the dopamine activating and reinforcing properties of ethanol. To this end acute and chronic behavioral and neurochemical experiments were performed in mice and rats. The results obtained indicate that central nAChRs in the ventral tegmental area are involved in mediating the mesolimbic dopamine activating and reinforcing effects of ethanol. Furthermore, the ethanol-induced activation of these receptors is probably indirect, subsequent to a primary interference of ethanol in the nucleus accumbens. Moreover, subchronic nicotine treatment enhances the reinforcing and dopamine activating properties of ethanol. This long-term effect may, however, derive from autonomic adaptations in response to intermittent blockade of peripheral nAChRs (rather than from intermittent stimulation of central receptors), and appears to be associated with development of a disinhibitory behavior that could involve also other neurotransmitters, e.g. serotonin. Taken together, these findings could provide a neurobiological explanation to the often observed co-abuse of nicotine and ethanol in man. Furthermore, since the behavioral models applied previously have predicted therapeutic drug effects in the clinic, the results suggest that selective blockade of the ventral tegmental nAChRs that are involved in the above effects may provide a new pharmacological alternative in the treatment of alcoholism.

Preexposure effects of nicotine and acetaldehyde on conditioned taste aversion induced by both drugs

Previous assessments have demonstrated an interaction between ethanol and nicotine in the conditioned taste-aversion (CTA) paradigm. The present study assessed whether acetaldehyde, the primary reinforcing metabolite of ethanol, would interact with nicotine as well. In six experiments, water-deprived male Wistar rats were preexposed to either acetaldehyde (0.2 or 0.3 g/kg, IP) or nicotine (0.8, 1.2, or 2 mg/kg, SC) for 3 consecutive days and then subsequently conditioned, 24 h later, with either nicotine (0.8, 1.2, or 2 mg/kg, SC) or acetaldehyde (0.2 or 0.3 g/kg, IP), respectively. There were 4 conditioning days and 4 drug-free test days, each spaced 72 h apart. On test days, animals were offered a free choice between water and saccharin. The results of the following set of experiments demonstrated a dose-related interaction between nicotine and acetaldehyde, where lower doses of each drug failed to attenuate CTA induced by one another, but a higher nicotine dose (2 mg/kg) attenuated the formation of a CTA induced by acetaldehyde (0.3 g/kg). It was argued that the primary metabolite of ethanol may play a role in the interaction between nicotine and ethanol previously observed.

Neonatal nicotine administration influences ethanol-induced behaviors

Neonatal mice were administered nicotine (66 microg (-)-nicotine base/kg body weight (bw) s.c. twice daily at 0800 and 1700 h on postnatal days 10 and 14) and control mice received saline (10 ml 0. 9% NaCl/kg bw s.c.) on the same occasions. Behavioral testing was initiated 3 months after birth. In Experiment 1, neonatal nicotine administration did not affect spontaneous motor activity but altered the peak dose stimulatory effect of ethanol upon locomotion and rearing activity from 3.0 mg/kg, in the control mice, to 1.5 mg/kg. Administration of the nicotine antagonist, mecamylamine (MEC, 2.0 mg/kg), had no effect upon the peak dose stimulatory effect (i.e., 1. 5 mg/kg) evidenced in the nicotine-treated mice, but attenuated the stimulatory effect of the 3.0 mg/kg dose of ethanol in the control mice. In Experiment 2, the effects of neonatal nicotine administration upon ethanol intake and preference were assessed. In the single fluid access (one-bottle) test, nicotine-treated mice consumed both more ethanol (2%, 4%, or 6% concentrations) and more tap water than control mice. In the two-bottle ethanol preference test, nicotine-treated mice consumed more ethanol and tap water. Further analysis of the high-preferring (HP) ethanol mice indicated higher ethanol intake and preference in the nicotine-treated mice but no differences in tap water or total fluid intake. The present findings are considered together with prevailing notions of nicotine receptor alterations and possible cross-sensitization effects modulating substance abuse.

Drinking as a risk factor for sustained smoking

Data from a nationally representative sample of US adults (n=42862) were used to explore the associations between drinking and smoking, on a lifetime and past-year basis, and between drinking and smoking cessation for a subsample of past-year smokers (n=12586). Smoking cessation was defined as current nonsmoking (as of the time of interview) that had lasted at least 3 months. The proportions of both lifetime and past-year smokers increased with volume of alcohol intake and frequency of heavy drinking and were greater for individuals with DSM-IV alcohol abuse or dependence than for individuals without these disorders. For example, the proportion of past-year smokers rose from 22.5% of lifetime abstainers to 53.0% of heavy drinkers, from 23.8% of those who never drank 5+ drinks on any drinking day to 61.8% of those who drank 5+ drinks weekly or more often and from 27.6% of individuals without past-year DSM-IV alcohol abuse or dependence to 55.5% of those with either of these disorders. The proportion of past-year smokers who had stopped smoking decreased from 7.8% of former drinkers to 4.6% of heavy drinkers, from 7.3% of those who never drank 5+ drinks to 3.4% of those who did so weekly or more often and from 6.7% among individuals without past-year abuse or dependence compared to 4.4% among those with either disorder. In a multivariate analysis that adjusted for background variables and smoking history, average daily ethanol intake was not significantly associated with the odds of smoking cessation, but drinking 5+ drinks at least once a month reduced the odds of cessation by 42%. Having an alcohol use disorder increased the odds of smoking cessation below the age of 30 (an effect that disappeared after adjusting for the interaction between age group and having children in the home), but had an increasingly negative effect on smoking cessation at older ages.

Nicotine induces disinhibitory behavior in the rat after subchronic peripheral nicotinic acetylcholine receptor blockade

The present study investigated the effects of subchronic nicotine, mecamylamine and hexamethonium, alone or in combinations, on locomotor activity and behavioral inhibition. Rats were divided into groups and tested for locomotor activity after acute nicotine. The different groups received vehicle, nicotine, mecamylamine, mecamylamine+nicotine, hexamethonium (two different concentrations) and hexamethonium+nicotine injections once a day for 15 days after which they were tested for nicotine-induced locomotor activity again. Acutely, nicotine stimulated locomotor activity, and repeated daily nicotine or hexamethonium+nicotine administration sensitized the animals to this nicotine-induced locomotor stimulation (locomotor sensitization). Mecamylamine administered subchronically in combination with nicotine was able to block the induction to locomotor sensitization to nicotine. None of the nicotinic receptor antagonists induced locomotor sensitization to nicotine by themselves. In the elevated plus-maze, subchronic nicotine treatment demonstrated a nicotine-induced behavioral disinhibition, measured as an increase of time spent in and entries made into open arms. In contrast to the findings regarding locomotor sensitization, none of the antagonists counteracted the induction of this nicotine-induced behavioral disinhibition after subchronic co-treatment with nicotine. In addition, both antagonists by themselves produced a similar effect as subchronic nicotine, i.e. promoted the development of nicotine-induced disinhibitory behavior. It was concluded that the induction of locomotor sensitization to nicotine involves stimulation of central nicotinic acetylcholine receptors, whereas the development of nicotine-induced behavioral disinhibition involves blockade of peripheral nicotinic acetylcholine receptors, and that the latter, but not the former, phenomenon from a pharmacological point of view appears to be related to the increased ethanol consummatory behavior observed after subchronic nicotine administration.

Nicotine and ethanol interaction on conditioned taste aversions induced by both drugs

The present study was designed to explore the interactive effects of nicotine and ethanol in the pretreatment and preexposure conditioned taste aversion (CTA) paradigm. The first experiment examined the effects of ethanol pretreatment on a nicotine induced CTA. The second experiment examined the effects of nicotine pretreatment on an ethanol CTA. The results of these two experiments revealed an asymmetrical interaction between ethanol and nicotine. Although nicotine pretreatment blocked an ethanol induced CTA, ethanol pretreatment merely attenuated a nicotine-induced CTA. These findings demonstrated that ethanol and nicotine interact pharmacologically in a unidirectional fashion, suggesting some unique and unshared pharmacological properties of each agent. The third experiment of this study examined the effects of preexposure with ethanol on a nicotine-induced CTA, while the fourth experiment examined the effects of preexposure with nicotine on an ethanol-induced CTA. These results revealed a symmetrical interaction between ethanol and nicotine in that both agents equally blocked CTA to one and the other. In contrast to the pretreatment CTA paradigm, these results suggested that both ethanol and nicotine appear to be functionally related and share common stimulus properties. Taken together, the present study demonstrates that while ethanol and nicotine are functionally related, they may also be endowed with unique unshared properties.

Smoking cessation treatment for substance misusers in early recovery: a review of the literature and recommendations for practice

Recent surveys have documented the very high incidence of smoking among treatment populations of alcohol and other drug misusers. While the health risks of smoking are well-documented in the literature, addictions professionals have traditionally been reluctant to address the problem of nicotine dependence with their clients. Recently, researchers have begun to investigate the impact of smoking cessation treatment on substance misusers who are also nicotine dependent. The purpose of this paper is to provide addictions treatment professionals with an overview of the research in this area and to highlight gaps in the knowledge base. In addition, this paper will review recent developments in the treatment of nicotine dependence and discuss their applicability to nicotine-dependent persons who are in treatment for the misuse of alcohol or another drug.

Combined effects of alcohol and nicotine on cardiovascular performance in a canine model

Alcohol and tobacco consumption are correlated. Smokers consume more alcohol than do nonsmokers, and alcohol consumers smoke more than do teetotalers. The independent effects of alcohol and nicotine on the cardiovascular system are well documented, but combined effects of short-term administration are unknown. This experimental work was designed to study the effects due to short-term administration of alcohol and nicotine on cardiovascular system. In phase I, 30 experiments were performed to study the dose-response curve of both the drugs. In phases II and III, 15 dogs were subjected to 30 experiments. In phase II, ethanol, 400 mg/kg, was given i.v., followed by nicotine 50 microg/kg, i.v., and in phase III, sequence of drug administration was reversed to study the effects on hemodynamics and coronary artery blood flow. The dose-response curve established the i.v. dose of ethanol, 400 mg/kg, and nicotine, 50 microg/kg. Ethanol administration caused a nonsignificant increase in heart rate (HR), mean arterial pressure (MAP), left ventricular systolic pressure (LVS), and left ventricular mechanical work (LVMW), and a decrease in maximal rate of increase of LV pressure per second (dP/dt), stroke volume (SV), and systemic vascular resistance (SVR). Left ventricular end-diastolic pressure (LVEDP), pulmonary artery mean pressure (PAM), right atrial pressure (RAP), pulmonary vascular resistance (PVR), myocardial oxygen consumption (MVO2), and average peak velocity of coronary blood flow (APV) had mild significant increases as compared with controls. Nicotine significantly increased heart rate, mean arterial pressures, LVEDP, and pulmonary artery, pulmonary capillary wedge, and right atrial pressures. Nicotine increased dP/dt (2,062-3,188; p < 0.006) and decreased APV (9 to 8; p < 0.03). Combined ethanol followed by nicotine had synergistic increase in HR, SD, MAP, LVS, LVEDP, pulmonary pressures, CO, SV, dP/dt (2,184 > 5,206; p < 0.005), MVO2, and LVMW. However, the excitatory effects of nicotine were attenuated when ethanol was administered after nicotine (dP/dt, reduced from 2,058 to 1,653; p < 0.04, and APV increased from 10 to 12; p < 0.02). We conclude that ethanol increased APV but had nonsignificant effects on the hemodynamics, whereas nicotine reduced the APV and had significant excitatory responses. In combination (i.v.), ethanol + nicotine produced significant synergistic excitatory effects. On the other hand, the nicotine + ethanol combination increased APV and caused attenuation of the excitatory effects of nicotine in dogs.

Long-term ethanol treatment elicits changes in nicotinic receptor binding in only a few brain regions

Chronic nicotine treatment will produce an upregulation of brain nicotinic receptors, and rats treated for 5 months with ethanol had increased [3H]nicotine binding in two of the three brain regions that were studied. However, studies using short-term treatment did not detect an effect of ethanol on mouse brain nicotinic receptor numbers. Therefore, LS and SS mice were force-fed ethanol (15%, v/v) in the drinking water for 6 months. The LS mice developed tolerance to ethanol as measured by Y-maze crossing and rearing activity, body temperature, and sleep time. No evidence for tolerance to ethanol was seen in the SS mice. However, the SS mice showed increases in [3H] nicotine binding in thalamus and an increase in [125I]alpha-bungarotoxin binding in the cerebellum and superior colliculus. LS mice had reduced levels of hippocampal [125I]alpha-bungarotoxin binding. Thus, long-term ethanol treatment may affect brain nicotinic receptor binding but the effect is limited to only a few brain regions and may be influenced by genetic factors.

Long-term ethanol and nicotine treatment elicit tolerance to ethanol

Several previous studies have shown that 1 to 2 weeks of treatment with ethanol elicits tolerance to several effects produced by ethanol and cross-tolerance to nicotine-induced hypothermia. Similarly, short-term, high-dose nicotine treatment produces tolerance to nicotine and cross-tolerance to ethanol-induced hypothermia. In the studies reported here, C57BL/6 mice were force-fed ethanol, nicotine, or an ethanol/nicotine combination in the drinking water for 6 months. All of the chronic drug-treated mice developed tolerance to ethanol as measured by open-field activity, body temperature, and sleep-time tests. Ethanol tolerance is due, in part, to enhanced metabolism and reduced CNS sensitivity in the two ethanol-treated groups but only to reduced CNS sensitivity in the nicotine-treated group. Similar levels of tolerance to nicotine developed in those two groups that were nicotine-treated, but no tolerance to nicotine was seen in those animals treated with ethanol alone. The tolerance to nicotine may be related to an upregulation of brain (cortex, hippocampus, and hypothalamus) [3H]-nicotine binding, but ethanol tolerance is not readily explained by changes in the number of the brain high affinity nicotine binding sites.

Individual variability in responses to nicotine

Individual variability in acute responses to nicotine, which may be defined as variable magnitude of effects following controlled dosing, is generally attributed to stable characteristics of tobacco users such as genetic/constitutional factors or to chronic behavioral factors (e.g., long-term use of other drugs). Often overlooked, however, is that such variability may also be due to the transient influence of the situational factors in which people consume nicotine, such as acute stress or physical activity. Results of selected studies from the author's laboratory provide examples of each of these sources of variability in nicotine responding on subjective, behavioral, and physiological measures. All studies used a nasal spray method of nicotine dosing or controlled smoking (paced puffing) to control acute nicotine exposure, an essential methodological feature of any research on individual differences in acute responses to nicotine. As an example of genetic/constitutional factors, gender differences in nicotine responding have begun to receive some attention, with few differences emerging. However, females may be more responsive than males to nonnicotine stimuli associated with smoking (e.g., sight and taste of smoke). In terms of chronic behavioral factors, long-term use of nicotine produces attenuation of most subjective and some behavioral effects of nicotine, reflecting chronic tolerance, and the possibility that chronic use of other drugs may alter responses to nicotine (i.e., cross-tolerance or cross-sensitization) deserves greater study. Of particular emphasis in this review is the modulating influence of acute situational factors on nicotine responding. Human studies have shown that magnitude of nicotine's subjective effects may depend on the predrug subjective state, level of physical activity vs. rest, and concurrent acute intake of other drugs, among other situational factors. Proper consideration of these situational factors may reveal the greatest source of individual variability in responding to nicotine and clarify the impact of more stable genetic/constitutional or chronic environmental factors.

The discriminative stimulus properties of an ethanol-nicotine mixture in rats

Sprague-Dawley rats were trained to discriminate between saline (SAL) and an ethanol-nicotine mixture (0.5 g/kg ethanol plus 0.5 mg/kg nicotine) administered 15 min prior to a 15-min drug discrimination training session under a FR-10 schedule of reinforcement. The mixture dose ratio was adjusted after training to obtain a drug mixture with which both individual drugs contributed about equally to the stimulus control (1.0 g/kg ethanol plus 0.3 mg/kg nicotine). The animals were then retrained for 32 sessions using this new mixture. After training, neither nicotine nor ethanol, when tested singly, engendered > 90% mixture-appropriate responding up to test doses that suppressed responding. Complete generalization occurred when the training doses of either nicotine or ethanol were administered in combination with various doses of the alternate drug element. (+)Nicotine, amphetamine and caffeine engendered dose-dependent increases in responses emitted on the mixture-appropriate lever. Pentobarbital and chloral hydrate only partially generalized to the training mixture. However, depressant/stimulant combinations of chloral hydrate+caffeine and pentobarbital+amphetamine produced complete generalization. The data suggest: (1) drug mixtures are not normally perceived as new entities distinct from their component elements; (2) training dose ratio may influence the characteristics of mixture discriminations; (3) stimulus element saliency may be a factor determining the nature of discriminative control by drug mixture cues; and (4) the ethanol-nicotine cue was most likely based on non-specific depressant/stimulant effects of these drugs.

A prospective study of the effects of cigarette smoking and alcohol abuse on mortality

OBJECTIVE

To compare the relative risks of alcohol abuse and cigarette smoking.

DESIGN

Cohort studies utilizing a 12-to-16-year follow-up of 47-to-52-year old men.

PARTICIPANTS AND SETTING

237 Caucasian college sophomores (COLLEGE sample) and 366 socially disadvantaged junior high school students (CORE-CITY sample) selected in 1940-43 for relative mental health and for interdisciplinary study.

MAIN RESULTS

The presence of many risk factors for death, including alcohol abuse and smoking, had been assessed prior to age 47 (CORE-CITY sample) and age 52 (COLLEGE sample). Over the next 12 years (CORE-CITY sample) and the next 16 years (COLLEGE sample), the men's mortality was monitored. Heavy use of cigarettes and alcohol abuse were highly correlated. When the effect of alcohol abuse was controlled, heavy smoking was associated with elevated mortality risks in both samples, although this was not statistically significant in the CORE-CITY sample. When smoking was controlled, the odds ratios for mortality from alcohol abuse were substantial in both samples.

CONCLUSIONS

These results and a literature review suggest that insufficient alcohol abuse histories may lead clinicians to underestimate the mortality risk of alcohol abuse.

Ethanol-nicotine interactions in long-sleep and short-sleep mice

The possibility that common genetic factors regulate initial sensitivities to ethanol and nicotine as well as the development of cross-tolerance between these agents was explored using the long-sleep (LS) and short-sleep (SS) mice. The LS mice proved to be more sensitive to an acute challenge with nicotine than were the SS mice. Segregation analysis (F1, F2, backcross) indicated that ethanol sensitivity and nicotine sensitivity segregate together. Acute pretreatment with nicotine did not significantly affect sensitivity to ethanol, but ethanol pretreatment altered nicotine responsiveness. The LS mice develop more tolerance to nicotine and ethanol than do the SS and they also develop more cross-tolerance. These genetically determined differences in initial sensitivities, and tolerance and cross-tolerance development are not readily explained by differences in brain nicotinic receptor numbers.

Desensitization of central cholinergic mechanisms and neuroadaptation to nicotine

This review focuses on neuroadaptation to nicotine. The first part of the paper delineates some possible general mechanisms subserving neuroadaptation to commonly abused drugs. The postulated role of the mesocorticolimbic neuroanatomical pathway and drug-receptor desensitization mechanisms in the establishment of tolerance to, dependence on, and withdrawal from psychoactive drugs are discussed. The second part of the review deals with the pharmacological effects of nicotine at both pre- and postsynaptic locations within the central nervous system, and the still-perplexing upregulation of brain nicotine-binding sites seen after chronic nicotine administration. A special emphasis has been put on desensitization of presynaptic cholinergic mechanisms, and postsynaptic neuronal nicotinic-receptor function and its modulation by endogenous substances. A comparison with the inactivation process occurring at peripheral nicotinic receptors is also included. Finally, a hypothesis on the possible connections between desensitization of central cholinergic mechanisms and neuroadaptation to nicotine is advanced. A brief comment on the necessity of fully understanding the effects of nicotine on the developing nervous system closes this work.

The actions of nicotine and cocaine in a mouse model of anxiety

The acute administration of nicotine (0.01-1.0 mg/kg IP) to the mouse increased the time spent and rearings and line crossings in the aversive brightly illuminated white area of a two compartment white/black test box, with a corresponding decrease in the black. This profile of change was maintained during twice daily administration (0.1 mg/kg IP) for 14 days. Eight to 96 hr following withdrawal of nicotine (14-day treatment), the behavioural profile was reversed to a preference for the black area: by 240 hr values had returned to control levels. In contrast to the effects of nicotine, an acute injection of cocaine (0.1-10 mg/kg IP) exacerbated the aversive response to the white area. However, similarly to nicotine, the administration of cocaine (1.0 mg/kg IP) twice daily for 14 days reduced the aversion to the white area and exacerbated the response following cocaine withdrawal. The effects of nicotine and cocaine to reduce and enhance responsiveness to the aversive properties of the white area are discussed in terms of an anxiolytic and anxiogenic response and the possibility of a serotonergic involvement.