r-bPiDI, an α6ß2* Nicotinic Receptor Antagonist, Decreases Nicotine-Evoked Dopamine Release and Nicotine Reinforcement.

α6ß2* nicotinic acetylcholine receptors (nAChRs) expressed by dopaminergic neurons mediate nicotine-evoked dopamine (DA) release and nicotine reinforcement. α6ß2* antagonists inhibit these effects of nicotine, such that α6ß2* receptors serve as therapeutic targets for nicotine addiction. The present research assessed the neuropharmacology of 1,10-bis(3-methyl-5,6-dihydropyridin-1(2H)-yl)decane (r-bPiDI), a novel small-molecule, tertiary amino analog of its parent compound, N,N-decane-1,10-diyl-bis-3-picolinium diiodide (bPiDI). bPiDI was previously shown to inhibit both nicotine-evoked DA release and the reinforcing effects of nicotine. In the current study, r-bPiDI inhibition of [(3)H]nicotine and [(3)H]methyllycaconitine binding sites was evaluated to assess interaction with the recognition binding sites on α4ß2* and α7* nAChRs, respectively. Further, r-bPiDI inhibition of nicotine-evoked DA release in vitro in the absence and presence of α-conotoxin MII and following chronic in vivo nicotine administration were determined. The ability of r-bPiDI to decrease nicotine self-administration and food-maintained responding was also assessed. Results show that r-bPiDI did not inhibit [(3)H]nicotine or [(3)H]methyllycaconitine binding, but potently (IC50 = 37.5 nM) inhibited nicotine-evoked DA release from superfused striatal slices obtained from either drug naïve rats or from those repeatedly treated with nicotine. r-bPiDI inhibition of nicotine-evoked DA release was not different in the absence or presence of α-conotoxin MII, indicating that r-bPiDI acts as a potent, selective α6ß2* nAChR antagonist. Acute systemic administration of r-bPiDI specifically decreased nicotine self-administration by 75 %, and did not alter food-maintained responding, demonstrating greater specificity relative to bPiDI and bPiDDB, as well as the tertiary amino analog r-bPiDDB. The current work describes the discovery of r-bPiDI, a tertiary amino, α-conotoxin MII-like small molecule that acts as a potent and selective antagonist at α6ß2* nAChRs to specifically decrease nicotine self-administration in rats, thus, establishing r-bPiDI as a lead compound for development as a treatment for nicotine addiction.

Effects of VMAT2 inhibitors lobeline and GZ-793A on methamphetamine-induced changes in dopamine release, metabolism and synthesis in vivo.

Vesicular monoamine transporter-2 (VMAT2) inhibitors reduce methamphetamine (METH) reward in rats. The current study determined the effects of VMAT2 inhibitors lobeline (LOB; 1 or 3 mg/kg) and N-(1,2R-dihydroxylpropyl)-2,6-cis-di(4-methoxyphenethyl)piperidine hydrochloride (GZ-793A; 15 or 30 mg/kg) on METH-induced (0.5 mg/kg, SC) changes in extracellular dopamine (DA) and its metabolite dihydroxyphenylacetic acid (DOPAC) in the reward-relevant nucleus accumbens (NAc) shell using in vivo microdialysis. The effect of GZ-793A (15 mg/kg) on DA synthesis in tissue also was investigated in NAc, striatum, medial prefrontal cortex and orbitofrontal cortex. In NAc shell, METH produced a time-dependent increase in extracellular DA and decrease in DOPAC. Neither LOB nor GZ-793A alone altered extracellular DA; however, both drugs increased extracellular DOPAC. In combination with METH, LOB did not alter the effects of METH on DA; however, GZ-793A, which has greater selectivity than LOB for inhibiting VMAT2, reduced the duration of the METH-induced increase in extracellular DA. Both LOB and GZ-793A enhanced the duration of the METH-induced decrease in extracellular DOPAC. METH also increased tissue DA synthesis in NAc and striatum, whereas GZ-793A decreased synthesis; no effect of METH or GZ-793A on DA synthesis was found in medial prefrontal cortex or orbitofrontal cortex. These results suggest that selective inhibition of VMAT2 produces a time-dependent decrease in DA release in NAc shell as a result of alterations in tyrosine hydroxylase activity, which may play a role in the ability of GZ-793A to decrease METH reward.

Promoting smoking abstinence among patients with chronic obstructive pulmonary disease: Initial feasibility.

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death in the U.S., with the majority of COPD deaths attributable to cigarette smoking. Despite this, individuals with COPD have a higher prevalence of smoking, poorer quit rates, and higher relapse rates compared to smokers without a COPD diagnosis. We examined the feasibility of an incentives-based intervention for producing an initial period of biochemically-verified smoking abstinence among daily smokers with COPD. Participants were randomly assigned to a Contingent (n = 13) or Noncontingent (n = 16) incentives condition and visited the clinic for 14 consecutive days. Contingent participants earned vouchers with monetary value contingent on breath carbon monoxide (CO) levels during Study Days 1-5 and urinary cotinine during Days 6-14. Voucher earnings began at $9.00 and increased by $1.50 with each subsequent negative sample for maximum possible of $362.50. Noncontingent participants received vouchers of comparable value independent of smoking status. Differences between conditions varied across study days for daily smoking abstinence (X2 = 45.27, p < 0.0001), CO (F(13, 280) = 1.95, p = 0.025), and cotinine (F(13, 279) = 2.20, p = 0.010), with generally higher rates of abstinence and lower CO and cotinine levels observed in the Contingent vs. Noncontingent conditions. Results from this randomized pilot study support the potential efficacy of an incentives-based intervention for reducing cigarette smoking among individuals with COPD. Further research efforts should seek to promote and evaluate longer-term abstinence and associated changes in respiratory function.

Opioid Overdose Experience, Risk Behaviors, and Knowledge in Drug Users from a Rural versus an Urban Setting.

BACKGROUND: Opioid use is highly prevalent in the United States and there has been an increased incidence in the rate of opioid-related overdose. While evidence suggests there are substantial differences in opioid use among rural versus urban settings, the rate of overdose and corresponding frequency of opioid overdose risk behaviors and overdose knowledge between rural and urban settings have not been examined. METHODS: Individuals with opioid use disorder from rural (N=98) and urban (N=247) settings completed a self-report survey regarding their lifetime history of overdose and overdose risk behaviors. Participants also completed the Brief Opioid Overdose Knowledge (BOOK) questionnaire, a 12-item self-report measure of opioid overdose knowledge. RESULTS: Overall, 35.6% of participants had experienced an overdose, and prevalence of overdose was significantly higher (p<.01) among rural (45.9%) vs. urban (31.6%) participants, though fewer rural participants reported past 30-day risk behaviors. There were few differences observed between the subset of rural and urban participants who had experienced an overdose, and fewer rural participants with a history of overdose reported past 30-day risk behaviors. Both rural and urban participants performed poorly on the BOOK, though the percent of correct responses was lowest among rural participants with a history of overdose. CONCLUSION: Results demonstrate higher rates of overdose among rural opioid users, though rural participants were less likely to report recent risk behaviors. Results also suggest that knowledge regarding key factors related to opioid overdose is severely lacking, particularly among rural opioid users, which could be a potential target for future intervention efforts.

Financial incentives to promote extended smoking abstinence in opioid-maintained patients: a randomized trial.

BACKGROUND AND AIMS: Prior studies by our group demonstrated the efficacy of a brief but intensive behavioral intervention for producing initial smoking abstinence among opioid-dependent patients. In the present study, our aim was to promote longer-duration abstinence in this population. Following an initial 2-week incentive intervention for smoking abstinence, we examined whether a 10-week maintenance arm involving continuation of contingent reinforcement will produce greater smoking abstinence than a similar duration of noncontingent reinforcement. DESIGN: Randomized, 12-week, parallel-group study. SETTING: Out-patient research clinic in Burlington, Vermont, USA. PARTICIPANTS: Opioid-maintained smokers (n = 88) who provided breath carbon monoxide and urinary cotinine specimens and received contingent reinforcement for smoking abstinence during weeks 1-2 (phase 1), with 63 randomized on day 14 to an extended contingent (EC; n = 31) or extended noncontingent (EN; n = 32) experimental condition for weeks 3-12 (phase 2). INTERVENTION AND CONTROL: The EC condition consisted of voucher values that escalated across consecutive negative samples until they reached $30, after which they remained at $30 per negative sample. A positive or a missing sample resulted in no vouchers for that day and reset the value of the next negative same to $9. Two consecutive negatives returned the schedule to the pre-reset value. The EN control condition consisted of vouchers delivered for providing scheduled samples, but independent of smoking status. MEASUREMENTS: The primary outcome was percentage of biochemically abstinent samples during phase 2. Secondary measures included abstinence status at final study visit, complete abstinence, participants' longest duration of continuous abstinence, cotinine and carbon monoxide (CO) levels and self-reported cigarettes per day. FINDINGS: EC participants achieved greater smoking abstinence during phase 2 than EN participants [46.7 versus 23.5% negative samples, respectively; odds ratio (OR) = 2.98, 95% confidence interval (CI) = 1.16-7.65, χ(2) 1  (=)  5.0, P = 0.02]. When longest duration of continuous abstinence was compared between experimental groups, EC participants achieved twice the mean duration of continuous abstinence compared with EN participants (3.31 versus 1.68 weeks; t61  = 1.83, P = 0.07). An effect of experimental condition was also seen on mean cotinine levels (42.5 versus 210.6 ng/ml, respectively; F1,61 =5.9, P = 0.02). CONCLUSIONS: Among opioid-maintained smokers receiving an initial period of daily contingent incentives, a contingent reinforcement intervention appears to be more effective at extending smoking abstinence than noncontingent reinforcement over 10 weeks.

Brief Opioid Overdose Knowledge (BOOK): A Questionnaire to Assess Overdose Knowledge in Individuals Who Use Illicit or Prescribed Opioids.

BACKGROUND: Opioid overdose is a public health crisis. This study describes efforts to develop and validate the Brief Opioid Overdose Knowledge (BOOK) questionnaire to assess patient knowledge gaps related to opioid overdose risks. METHODS: Two samples of illicit opioid users and a third sample of patients receiving an opioid for the treatment of chronic pain (total N = 848) completed self-report items pertaining to opioid overdose risks. RESULTS: A 3-factor scale was established, representing Opioid Knowledge (4 items), Opioid Overdose Knowledge (4 items), and Opioid Overdose Response Knowledge (4 items). The scale had strong internal and face validity. Patients with chronic pain performed worse than illicit drug users in almost all items assessed, highlighting the need to increase knowledge of opioid overdose risk to this population. CONCLUSIONS: This study sought to develop a brief, internally valid method for quickly assessing deficits in opioid overdose risk areas within users of illicit and prescribed opioids, to provide an efficient metric for assessing and comparing educational interventions, facilitate conversations between physicians and patients about overdose risks, and help formally identify knowledge deficits in other patient populations.

Amphetamine self-administration and dopamine function: assessment of gene × environment interactions in Lewis and Fischer 344 rats.

RATIONALE: Previous research suggests both genetic and environmental influences on substance abuse vulnerability. OBJECTIVES: The current work sought to investigate the interaction of genes and environment on the acquisition of amphetamine self-administration as well as amphetamine-stimulated dopamine (DA) release in nucleus accumbens shell using in vivo microdialysis. METHODS: Inbred Lewis (LEW) and Fischer (F344) rat strains were raised in either an enriched condition (EC), social condition (SC), or isolated condition (IC). Acquisition of amphetamine self-administration (0.1 mg/kg/infusion) was determined across an incrementing daily fixed ratio (FR) schedule. In a separate cohort of rats, extracellular DA and the metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) were measured in the nucleus accumbens shell following an acute amphetamine injection (1 mg/kg). RESULTS: "Addiction-prone" LEW rats had greater acquisition of amphetamine self-administration on a FR1 schedule compared to "addiction-resistant" F344 rats when raised in the SC environment. These genetic differences were negated in both the EC and IC environments, with enrichment buffering against self-administration and isolation enhancing self-administration in both strains. On a FR5 schedule, the isolation-induced increase in amphetamine self-administration was greater in F344 than LEW rats. While no group differences were obtained in extracellular DA, gene × environment differences were obtained in extracellular levels of the metabolite DOPAC. In IC rats only, LEW rats showed attenuation in the amphetamine-induced decrease in DOPAC compared to F344 rats. IC LEW rats also had an attenuated DOPAC response to amphetamine compared to EC LEW rats. CONCLUSIONS: The current results demonstrate gene × environment interactions in amphetamine self-administration and amphetamine-induced changes in extracellular DOPAC in nucleus accumbens (NAc) shell. However, the behavioral and neurochemical differences were not related directly, indicating that mechanisms independent of DA metabolism in NAc shell likely mediate the gene × environment effects in amphetamine self-administration.

Lifetime history of heroin use is associated with greater drug severity among prescription opioid abusers.

BACKGROUND: While research suggests primary prescription opioid (PO) abusers may exhibit less severe demographic and drug use characteristics than primary heroin abusers, less is known about whether a lifetime history of heroin use confers greater severity among PO abusers. OBJECTIVE: In this secondary analysis, we examined demographic and drug use characteristics as a function of lifetime heroin use among 89 PO-dependent adults screened for a trial evaluating the relative efficacy of buprenorphine taper durations. Exploratory analyses also examined contribution of lifetime heroin use to treatment response among a subset of participants who received a uniform set of study procedures. METHODS: Baseline characteristics were compared between participants reporting lifetime heroin use ≥5 (H(+); n=41) vs. <5 (H(-); n=48) times. Treatment response (i.e., illicit opioid abstinence and treatment retention at end of study) was examined in the subset of H(+) and H(-) participants randomized to receive the 4-week taper condition (N=22). RESULTS: H(+) participants were significantly older and more likely to be male. They reported longer durations of illicit opioid use, greater alcohol-related problems, more past-month cocaine use, greater lifetime IV drug use, and greater lifetime use of cigarettes, amphetamines and hallucinogens. H(+) participants also had lower scores on the Positive Symptom Distress and Depression subscales of the Brief Symptom Inventory. Finally, there was a trend toward poorer treatment outcomes among H(+) participants. CONCLUSION: A lifetime history of heroin use may be associated with elevated drug severity and unique treatment needs among treatment-seeking PO abusers.

Role of medial prefrontal and orbitofrontal monoamine transporters and receptors in performance in an adjusting delay discounting procedure.

Performance in an adjusting delay discounting procedure is predictive of drug abuse vulnerability; however, the shared underlying specific prefrontal neural systems linking delay discounting and increased addiction-like behaviors are unclear. Rats received direct infusions of methylphenidate (MPH; 6.25, 25.0, or 100µg), amphetamine (AMPH; 0.25, 1.0, or 4.0µg), or atomoxetine (ATO; 1.0, 4.0, or 16.0µg) into either medial prefrontal cortex (mPFC) or orbitofrontal cortex (OFC) immediately prior to performance in an adjusting delay task. These drugs were examined because they are efficacious in treating impulse control disorders. Because dopamine (DA) and serotonin (5-HT) receptors are implicated in impulsive behavior, separate groups of rats received microinfusions of the DA receptor-selective drugs SKF 81297 (0.1 or 0.4µg), SCH 23390 (0.25 or 1.0µg), quinpirole (1.25 or 5.0µg), and eticlopride (0.25 or 1.0µg), or received microinfusions of the 5-HT receptor-selective drugs 8-OH-DPAT (0.025 or 0.1µg), WAY 100635 (0.01 or 0.04µg), DOI (2.5 or 10.0µg), and ketanserin (0.1 or 0.4µg). Impulsive choice was not altered significantly by MPH, AMPH, or ATO into either mPFC or OFC, indicating that neither of these prefrontal regions alone may mediate the systemic effect of ADHD medications on impulsive choice. However, quinpriole (1.25µg) and eticlopride infused into mPFC increased impulsive choice, whereas 8-OH-DPAT infused into OFC decreased impulsive choice. These latter results demonstrate that blockade of DA D2 receptors in mPFC or activation of 5-HT1A receptors in OFC increases impulsive choice in the adjusting delay procedure.

Concurrent choice for social interaction and amphetamine using conditioned place preference in rats: effects of age and housing condition.

BACKGROUND: Social interaction can serve as a natural reward that attenuates drug reward in rats; however, it is unknown if age or housing conditions alter the choice between social interaction and drug. METHODS: Individually- and pair-housed adolescent and adult male rats were tested using conditioned place preference (CPP) in separate experiments in which: (1) social interaction was conditioned against no social interaction; (2) amphetamine (AMPH; 1mg/kg, s.c.) was conditioned against saline; or (3) social interaction was conditioned against AMPH. RESULTS: Social interaction CPP was obtained only in individually-housed adolescents, whereas AMPH CPP was obtained in both individually-housed adolescents and adults; however, the effect of AMPH was not statistically significant in pair-housed adults. When allowed to choose concurrently between compartments paired with either social interaction or AMPH, individually-housed adolescents preferred the compartment paired with social interaction, whereas pair-housed adolescents preferred the compartment paired with AMPH. Regardless of housing condition, adults showed a similar preference for the compartments paired with either social interaction or AMPH. CONCLUSIONS: Although some caution is needed in interpreting cross-experiment comparisons, the overall results suggest that individually-housed adolescents were most sensitive to the rewarding effect of social interaction, and this hypersensitivity to social reward effectively competed with AMPH reward.