Discriminative Stimulus Effects of Abused Inhalants

Assessment of Abuse-Related Discriminative Stimulus Effects of Nicotine Aerosol in Rodents

The rapid increase in e-cigarette use highlights the importance of developing relevant, predictive animal models exploring their potential health implications. The goal of the present study was to examine the abuse-related effects of brief, repeated e-cigarette aerosol exposures in rodents modeling human e-cigarette user behavior. We evaluated the discriminative stimulus effects of brief, repeated puffs of inhaled nicotine in rats that had been trained to discriminate injected nicotine from saline. Locomotor activity measurement following exposure to injected and aerosolized nicotine was also assessed as an additional behavioral outcome. We hypothesized that the stimulus effects of nicotine aerosol were central nervous system (CNS)-mediated and comparable to that produced by an injected nicotine training stimulus. We further hypothesized that number of aerosol puffs and the e-liquid nicotine concentration which was aerosolized would impact the substitution of nicotine aerosol for injected nicotine. Both nicotine injections and exposures to nicotine aerosol produced a dose-dependent effect on locomotor activity. Nicotine aerosol under our puffing conditions produced e-liquid nicotine concentration-dependent and puff-number-dependent complete substitution for the injected nicotine training condition. The nicotinic antagonist, mecamylamine, completely blocked nicotine-appropriate responding produce by the training dose of 0.3 mg/kg injected nicotine as well as that resulting from exposure to aerosol puffs generated by e-liquid containing 3 mg/ml nicotine, demonstrating that the stimulus of inhaled nicotine was most likely CNS-mediated and not due to olfactory stimulus properties. Overall, the results support the hypothesis that an aerosol exposure drug discrimination model in rodents has applicability to studying the abuse-related effects of e-cigarettes. SIGNIFICANCE STATEMENT: Animal models of nicotine aerosol exposure using testing conditions resembling human e-cigarette use are lacking. In this study, we test a novel preclinical model of nicotine vaping in rodents which allows for the exploration of the abuse-related effects of e-cigarettes. This model has the potential to contribute both to our understanding of the abuse-related pharmacological effects of e-cigarettes as well as aid in the development of rationale, evidence-based e-cigarette regulatory policies.

The last two decades on preclinical and clinical research on inhalant effects

This paper reviews the scientific evidence generated in the last two decades on the effects and mechanisms of action of most commonly misused inhalants. In the first section, we define what inhalants are, how they are used, and their prevalence worldwide. The second section presents specific characteristics that define the main groups of inhalants: (a) organic solvents; (b) aerosols, gases, and volatile anesthetics; and (c) alkyl nitrites. We include a table with the molecular formula, structure, synonyms, uses, physicochemical properties and exposure limits of representative compounds within each group. The third and fourth sections review the direct acute and chronic effects of common inhalants on health and behavior with a summary of mechanisms of action, respectively. In the fifth section, we address inhalant intoxication signs and available treatment. The sixth section examines the health effects, intoxication, and treatment of nitrites. The seventh section reviews current intervention strategies. Finally, we propose a research agenda to promote the study of (a) solvents other than toluene; (b) inhalant mixtures; (c) effects in combination with other drugs of abuse; (d) age and (e) sex differences in inhalant effects; (f) the long-lasting behavioral effects of animals exposed in utero to inhalants; (g) abstinence signs and neurochemical changes after interrupting inhalant exposure; (h) brain networks involved in inhalant effects; and finally (i) strategies to promote recovery of inhalant users.

Differences in use of inhalants among sexual minorities in the USA in 2015-2018

OBJECTIVES

Inhalants are substances with underestimated abuse potential associated with cardiac problems, dizziness, seizures, and decreased level of consciousness. Inhalants are commonly used by the LGB population, who are vulnerable to their harms. US epidemiologic inhalants data are scarce. The aims of this study are to: i) investigate associations between inhalant use and sexual identity groups; ii) examine associations with use of other drugs among lesbian/gays who use inhalants.

METHODS

Data came from the 2015-2018 NSDUH (n = 168,560). Participants ages 18 or older were asked if they had used any inhalants in their lifetime and past-year. We investigated the associations between inhalant use with sexual identity categories heterosexual, lesbian/gay, and bisexual using logistic regression models with complex survey design.

RESULTS

Total prevalences of lifetime and past-year use of inhalants were 9.4% and 0.5%, respectively. Lesbian/gay population (L/G) and bisexuals (B) reported higher odds of lifetime (L/G: aOR = 3.71, 95%CI = [3.19,4.30], B: aOR = 1.82, 95%CI = [1.64,2.03) and past-year (L/G: aOR = 11.57, 95%CI = [8.95,14.96], B: aOR = 2.81, 95%CI = [2.02,3.92]) inhalant use compared to heterosexuals. Among L/G, men had higher odds of lifetime (aOR = 4.11, 95%CI = [3.06,5.52]) and past-year (aOR = 15.67, 95%CI = [7.27,33.76]) inhalant use versus women. Use of marijuana (aOR = 2.76, 95%CI = [1.48,5.16]), other illegal drugs (aOR = 2.70, 95%CI = [1.60,4.56]), and non-medical use of psychotherapeutics (aOR = 2.67, 95%CI = 1.77,4.05) were associated with past-year use of inhalants among L/G.

CONCLUSION

LGB population is at elevated risk of inhalant use and of concurrent use with other drugs. Gay men had significantly higher odds of inhalant use compared to lesbians and bisexuals. Informative and in-site harm reduction measures are warranted to prevent harms from inhalant use.

A Prospective Evaluation of Drug Discrimination in Pharmacology

As investigators, we use many methodologies to answer both practical and theoretical questions in our field. Occasionally, we must stop and collect the latest findings or trends and then look forward to where our ideas, findings, and hypotheses may take us. Similar to volumes that were published in previous years on drug discrimination (Glennon and Young, Drug discrimination applications to medicinal chemistry and drug studies. Wiley, Hoboken, 2011; Ho et al., Drug discrimination and state dependent learning. Academic Press, New York, 1978), this collection in Current Topics in Behavioral Neurosciences serves as a current analysis of the continued value of the drug discrimination procedure to the fields of pharmacology, neuroscience, and psychology and as a stepping stone to where drug discrimination methodology can be applied next, in both a practical and theoretical sense. This final chapter represents one investigator's perspective on the utility and possibilities for a methodology that she fell in love with over 30 years ago.