Nicotine enhancement and reinforcer devaluation: Interaction with opioid receptors

Impact of the Ottawa model on opiate screening and smoking cessation in methadone-treated patients with opioid use disorder: A retrospective cohort analysis

INTRODUCTION

Approximately 60 million individuals worldwide used opioids in 2021, constituting 1.2% of the global adult population. This study aimed to evaluate the effectiveness of integrated treatment strategies for opioid use disorder and nicotine use disorder by assessing the impact of smoking cessation within a methadone treatment framework.

METHODS

In a retrospective cohort study, 53 methadone maintenance patients were divided into 16 treatment-seeking smokers (TSS) and 37 treatment-rejecting smokers (TRS) based on their participation in the Ottawa model for smoking cessation plus 16 weeks of varenicline treatment. Both groups received standard methadone treatment for 68 weeks. TSS were followed up for 44 weeks to assess smoking cessation outcomes, while TRS had none due to their lack of participation in smoking cessation treatment.

RESULTS

The median age of the TSS group was 48 years, while that of the TRS group was 45.5 years. Males comprised 75% of TSS and 94.6% of the TRS. TSS exhibited an 83% decrease in positive opioid screen results compared to TRS (p=0.023). In TSS, peak smoking cessation success was observed at week 20, with 57% of participants maintaining carbon monoxide levels <5 ppm.

CONCLUSIONS

The significant reduction in positive opioid screens and the high smoking cessation rate in the TSS group highlight the efficacy of combined treatment methods. This study underscores the advantages of integrating smoking cessation with methadone maintenance treatment, indicating that comprehensive approaches can substantially improve treatment outcomes.

Elucidating the reinforcing effects of nicotine: a tribute to Nadia Chaudhri

Nadia Chaudhri worked with us as a graduate student in the Center for Neuroscience at the University of Pittsburgh from 1999 until she earned her PhD in 2005, a time that coincided with the discovery in our lab of the dual reinforcing actions of nicotine, a concept that she played an important role in shaping. The research that was described in her doctoral thesis is among the foundational pillars of the now well-accepted notion that nicotine acts as both a primary reinforcer and an amplifier of other reinforcer stimuli. This reinforcement-enhancing action of nicotine is robust and likely to be a powerful driver of nicotine use. Below, we discuss the evidence that these two actions of nicotine - primary reinforcement and reinforcement enhancement - are distinct and dissociable, a finding that Nadia was closely associated with. We go on to address two other topics that greatly interested Nadia during that time, the generalizability of the reinforcement-enhancing action of nicotine to multiple classes of reinforcing stimuli and potential sex differences in the dual reinforcing actions of nicotine. The research has greatly expanded since Nadia's involvement, but the core ideas that she helped to develop remain central to the concept of the dual reinforcing actions of nicotine and its importance for understanding the drivers of nicotine use.

Reductions in tobacco use in naltrexone, relative to buprenorphine-maintained individuals with opioid use disorder: Secondary analysis from the National Drug Abuse Treatment Clinical Trials Network

BACKGROUND

Smoking prevalence in individuals with opioid use disorder (OUD) is over 80%. Research suggests that opioid use significantly increases smoking, which could account for the strikingly low smoking-cessation rates observed in both methadone- and buprenorphine-maintained patients, even with the use of first-line smoking-cessation interventions. If opioids present a barrier to smoking-cessation, then better smoking outcomes should be observed in OUD patients treated with extended-release naltrexone (XR-NTX, an opioid antagonist) compared to those receiving buprenorphine (BUP-NX, a partial opioid agonist).

METHODS

The current study is a secondary analysis of a 24-week, multi-site, open-label, randomized clinical trial conducted within the National Drug Abuse Treatment Clinical Trials Network comparing the effectiveness of XR-NTX vs. BUP-NX for adults with OUD. Longitudinal mixed effects models were used to determine if there was a significant reduction in cigarette use among daily smokers successfully inducted to treatment (n = 373) and a subset of those who completed treatment (n = 169).

RESULTS

Among daily smokers inducted onto OUD medication, those in the XR-NTX group smoked fewer cigarettes per day (M = 11.36, SE = 0.62) relative to smokers in the BUP-NX group (M = 13.33, SE = 0.58) across all study visits, (b (SE) = -1.97 (0.55), p < .01). Results were similar for the treatment completers.

CONCLUSIONS

OUD patients treated with XR-NTX reduced cigarette use more than those treated with BUP-NX, suggesting that XR-NTX in combination with other smoking cessation interventions might be a better choice for OUD smokers interested in reducing their tobacco use.

Nicotine-induced enhancement of a sensory reinforcer in adult rats: antagonist pretreatment effects

RATIONALE AND OBJECTIVES

The reinforcement-enhancing effect (REE) of nicotine refers to the drug's ability to enhance the strength of other primary and conditioned reinforcers. The main aim was to investigate neuropharmacological mechanisms underlying nicotine's strengthening of a primary visual reinforcer (i.e., a light cue), using a subcutaneous (SC) dose previously shown to provide plasma nicotine levels associated with habitual smoking.

METHODS

Adult male rats pressed an "active" lever to illuminate a brief cue light during daily 60-min sessions. Rats that showed a clear REE were tested with systemically administered pretreatment drugs followed by nicotine (0.1 mg/kg SC) or saline challenge, in within-subject counterbalanced designs. Pretreatments were mecamylamine (nicotinic, 0.1-1 mg/kg SC), SCH 39166 (D1-like dopaminergic, 0.003-0.2 mg/kg SC), naloxone (opioid, 1 and 5 mg/kg SC), prazosin (alpha1-adrenergic antagonist, 1 and 2 mg/kg IP), rimonabant (CB1 cannabinoid inverse agonist, 3 mg/kg IP), sulpiride (D2-like dopaminergic antagonist, 40 mg/kg SC), or propranolol (beta-adrenergic antagonist, 10 mg/kg IP).

RESULTS

The nicotine REE was abolished by three antagonists at doses that did not impact motor output, i.e., mecamylamine (1 mg/kg), SCH 39166 (0.01 and 0.03 mg/kg), and naloxone (5 mg/kg). Prazosin and rimonabant both attenuated the nicotine REE, but rimonabant also suppressed responding more generally. The nicotine REE was not significantly altered by sulpiride or propranolol.

CONCLUSIONS

In adult male rats, the reinforcement-enhancing effect of low-dose nicotine depends on nicotinic receptor stimulation and on neurotransmission via D1/D5 dopaminergic, opioid, alpha1-adrenergic, and CB1 cannabinoid receptors.

Independent association of tobacco use with opioid use disorder in patients of European ancestry with chronic non-cancer pain

BACKGROUND

The harms associated with prescription opioid abuse have become a public health crisis. There is a need for evidence-based objective markers of the risk of opioid use disorder (OUD) in patients with pain receiving opioid treatment. The objective of this study was to evaluate the independent association of tobacco use and OUD in patients with chronic non-cancer pain.

METHODS

This cross-sectional naturalistic study evaluated 798 adults ≥ 18 years with chronic non-cancer pain treated with long-term opioid therapy (≥ 6 months) who either developed an OUD (cases, n = 216) or displayed no evidence of an OUD (controls, n = 582). The primary outcome was presence of OUD. In addition to current self-reported tobacco use (primary predictor), covariates included demographics, pain severity, and psychiatric history. Data were collected between November 2012 and September 2018.

RESULTS

Current tobacco use independently was strongly associated with OUD [odds ratio (OR) 14.0, 95 % confidence interval (CI) 9.5-20.6, p < 0.001], and this association remained significant after adjusting for other risk factors [adjusted odds ratio (aOR) 7.6, 95 % CI 4.8-12.2, p < 0.001]. Other factors associated independently with development of OUD included age, marital status, financial status, education and pain severity.

CONCLUSIONS AND RELEVANCE

Current tobacco use is significantly associated with OUD in patients with chronic pain receiving long-term opioid therapy.

Caenorhabditis elegans Show Preference for Stimulants and Potential as a Model Organism for Medications Screening

The nematode Caenorhabditis elegans (C. elegans) is a popular invertebrate model organism to study neurobiological disease states. This is due in part to the intricate mapping of all neurons and synapses of the entire animal, the wide availability of mutant strains, and the genetic and molecular tools that can be used to manipulate the genome and gene expression. We have shown that, C. elegans develops a conditioned preference for cues that had previously been paired with either cocaine or methamphetamine exposure that is dependent on dopamine neurotransmission, similar to findings using place conditioning with rats and mice. In the current study, we show C. elegans also display a preference for, and self-exposure to, cocaine and nicotine. This substance of abuse (SOA) preference response can be selectively blocked by pretreatment with naltrexone and is consistent with the recent discovery of an opioid receptor system in C. elegans. In addition, pre-exposure to the smoking cessation treatment varenicline also inhibits self-exposure to nicotine. Exposure to concentrations of treatments that inhibit SOA preference/self-exposure did not induce any significant inhibition of locomotor activity or affect food or benzaldehyde chemotaxis. These data provide predictive validity for the development of high-throughput C. elegans behavioral medication screens. These screens could enable fast and accurate generation of data to identify compounds that may be effective in treating human addiction. The successful development and validation of such models would introduce powerful and novel tools in the search for new pharmacological treatments for substance use disorders, and provide a platform to study the mechanisms that underlie addictions.

Endogenous Opiates and Behavior: 2016

This paper is the thirty-ninth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2016 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.