Nicotine as a factor in stress responsiveness among detoxified alcoholics

Stress System Response and Decision Making in Heavy Episodic Users of Alcohol and Online Video Games

Objective: Few empirical studies have addressed stress system response and subsequent decision making in problematic online video game players who also consume alcohol. Method: Participants were randomly assigned to either receive a psychosocial stressor, including evaluated public speaking and mental arithmetic, or control condition. Salivary cortisol, cardiovascular and subjective responses were collected. Following, decision making was assessed using the Iowa Gambling Task. Results: In this sample of moderate internet gamers (N = 71; 45 male, 16.9% meeting suggested DSM-5 criteria for internet gaming disorder), 53.52% met gender-specific cut-points for heavy episodic drinking. Overall, participants in the TSST condition demonstrated elevated systolic and diastolic blood pressure, self-reported anxiety, and negative affect (ps < .05). However, response to the TSST was varied, particularly in individuals reporting binge internet gaming (6 h or more consecutive use in the last 30 d) who did not display the expected decline in positive affect in response to the TSST (p = .02). Differences in greater advantageous decision making between heavy episodic internet gaming participants in the stress condition, versus those reading a travel magazine, were also noted. These differences were not significant in participants reporting an absence of heavy episodic gaming behavior. Conclusions: These findings support the continued study of individuals who engage in problematic internet gaming behavior, particularly those who engage in heavy episodic use of alcohol.

Continuous nicotine exposure does not affect resurgence of alcohol seeking in rats

Alcohol is the most commonly used drug in the United States and alcohol abuse can lead to alcohol use disorder. Alcohol use disorder is a persistent condition and relapse rates following successful remission are high. Many factors have been associated with relapse for alcohol use disorder, but identification of these factors has not been well translated into preventative utility. One potentially important factor, concurrent nicotine use, has not been well investigated as a causal factor in relapse for alcohol use disorder. Nicotine increases the value of other stimuli in the environment and may increase the value of alcohol. If nicotine increases the value of alcohol, then nicotine use during and after treatment may make relapse more probable. In the current study, we investigated the effect of continuous nicotine exposure (using osmotic minipumps to deliver nicotine or saline, depending on group, at a constant rate for 28 days) on resurgence of alcohol seeking in rats. Resurgence is a type of relapse preparation that consists of three phases: Baseline, Alternative Reinforcement, and Resurgence Testing. During Baseline, target responses produced a dipper of alcohol. During Alternative Reinforcement, target responses were extinguished and responses on a chain produced a chocolate pellet. During Resurgence Testing, responses on the chain were also extinguished and a return to responding on the target lever was indicative of resurgence. Multilevel modeling was used to analyze the effect of nicotine on resurgence. Both the nicotine and saline group showed resurgence of alcohol seeking, but there was no difference in the degree of resurgence across groups. Future directions could involve testing alternative drug delivery techniques.

Anger, anxiety, and depressive affect as predictors of stress-induced cortisol production in khat and tobacco users

INTRODUCTION

Glucocorticoid activity is disrupted in substance users including khat chewers who also use tobacco. Anger, dysphoria, and anxiety can mediate this relationship. The aim of this study was to contrast emotion dysregulation and substance use variables as predictors of post-stress cortisol output.

MATERIALS AND METHODS

Comparable numbers of males (n = 90) and females (n = 85) including controls, khat only, and concurrent khat and tobacco users participated in a stress study. Depressive affect, anxiety, anger, substance use patterns, and saliva samples were collected following a standardized laboratory stress manipulation.

RESULTS

Regression analysis showed that high depression and low anxiety was associated with high post-stress cortisol, but only in co-users of tobacco and khat. Males, but not females, showed a significant association between co-use of khat and tobacco and cortisol, which appears to be mediated by frequency of use. The link between anxiety and post-stress cortisol in the co-users remained significant after controlling for nicotine dependence and substance use frequency.

CONCLUSION

Anxiety predicted the neuroendocrine consequences of concurrent use of tobacco and khat above and beyond sex, nicotine dependence, anger, and substance use frequency. Sex differences, however, are related to differences in nicotine dependence.

Sex Specific Alterations in α4*Nicotinic Receptor Expression in the Nucleus Accumbens

Background: The mechanisms leading from traumatic stress to social, emotional and cognitive impairment and the development of mental illnesses are still undetermined and consequently there remains a critical need to develop therapies for preventing the adverse consequences of traumatic stress. Research indicates nicotinic acetylcholine receptors containing α4 subunits (α4*nAChRs) are both impacted by stress and capable of modulating the stress response. In this study, we investigated whether varenicline, a partial α4β2*nAChR agonist which reduces nicotine, alcohol and sucrose consumption, can reduce stress, a driving factor in substance use disorders. We also examined the effect of stress on nucleus accumbens (NAc) α4*nAChR expression. Methods: Transgenic mice with fluorescent tags attached to α4*nAChRs were administered varenicline and/or yohimbine (a pharmacological stressor) and plasma corticosterone and NAc α4*nAChR expression were measured. A separated group of mice were exposed to maternal separation (MS) during post-natal day (P) 2–14, then restraint stressed (30 min) at six weeks of age. Body weight, anxiety-like behaviours (elevated plus maze), plasma corticosterone and NAc α4*nAChR levels were measured. Results: Varenicline attenuated yohimbine-induced plasma corticosterone increases with no effect on NAc α4*nAChR expression. MS reduced unrestrained plasma corticosterone levels in both sexes. In females, MS increased body weight and NAc α4*nAChR expression, whereas, in males, MS and restraint caused a greater change in anxiety-like behaviours and plasma corticosterone levels. Restraint altered NAc α4*nAChR expression in both male and female MS mice. Conclusions: The effects of stress on NAc α4*nAChR are sex-dependent. While varenicline attenuated acute stress-induced rises in corticosterone levels, future studies are required to determine whether varenicline is effective for relieving the effects of stress.

Cigarette Smoking and Tryptophan Hydroxylase 2 mRNA in the Dorsal Raphe Nucleus in Suicides

Cigarette smoking is associated with suicide and mood disorders and stimulates serotonin release. Tryptophan hydroxylase (TPH2) synthesizes serotonin and is over-expressed in suicides. We determined whether smoking is associated with TPH2 mRNA in suicides and controls. TPH2 mRNA was measured postmortem in the dorsal raphe nucleus (DRN) of controls (N = 26, 17 nonsmokers and nine smokers) and suicides (N = 23, 5 nonsmokers and 18 smokers). Psychiatric history was obtained by psychological autopsy. TPH2 mRNA was greater in suicide nonsmokers than suicide smokers, control smokers and control nonsmokers (p = 0.006). There was more TPH2 mRNA throughout the DRN. Smoking interferes with the TPH2 mRNA increase observed in suicide nonsmokers. The absence of altered TPH2 expression in non-suicide smokers suggests no pharmacological effect of smoking.

Ethanol and nicotine interaction within the posterior ventral tegmental area in male and female alcohol-preferring rats: evidence of synergy and differential gene activation in the nucleus accumbens shell

RATIONALE

Ethanol and nicotine are frequently co-abused. The biological basis for the high co-morbidity rate is not known. Alcohol-preferring (P) rats will self-administer EtOH or nicotine directly into the posterior ventral tegmental area (pVTA).

OBJECTIVE

The current experiments examined whether sub-threshold concentrations of EtOH and nicotine would support the development of self-administration behaviors if the drugs were combined.

METHODS

Rats were implanted with a guide cannula aimed at the pVTA. Rats were randomly assigned to groups that self-administered sub-threshold concentrations of EtOH (50 mg%) or nicotine (1 μM) or combinations of ethanol (25 or 50 mg%) and nicotine (0.5 or 1.0 μM). Alterations in gene expression downstream projections areas (nucleus accumbens shell, AcbSh) were assessed following a single, acute exposure to EtOH (50 mg%), nicotine (1 μM), or ethanol and nicotine (50 mg% + 1 μM) directly into the pVTA.

RESULTS

The results indicated that P rats would co-administer EtOH and nicotine directly into the pVTA at concentrations that did not support individual self-administration. EtOH and nicotine directly administered into the pVTA resulted in alterations in gene expression in the AcbSh (50.8-fold increase in brain-derived neurotrophic factor (BDNF), 2.4-fold decrease in glial cell line-derived neurotrophic factor (GDNF), 10.3-fold increase in vesicular glutamate transporter 1 (Vglut1)) that were not observed following microinjections of equivalent concentrations/doses of ethanol or nicotine.

CONCLUSION

The data indicate that ethanol and nicotine act synergistically to produce reinforcement and alter gene expression within the mesolimbic dopamine system. The high rate of co-morbidity of alcoholism and nicotine dependence could be the result of the interactions of EtOH and nicotine within the mesolimbic dopamine system.