Impact of the COVID-19 Pandemic on Functions of Nursing Professionals in the Care of Opioid Use Disorder: Systematic Review.

BACKGROUND: Nursing professionals are vitally involved in the cascade of care for opioid use disorders (OUDs). The global spread of COVID-19 has had complex effects on public health aspects of major diseases, including OUDs. There are limited data on the major ways in which the COVID-19 pandemic has affected the functions of nursing professionals in the care of OUDs. METHOD: This systematic review followed Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines and examined published data for trends in OUD care during the first 2 years of the COVID-19 pandemic, focusing on nursing functions. The National Library of Medicine PubMed database and the EMBASE database were examined for peer-reviewed studies with primary data published between January 1, 2020, and December 31, 2021. REVIEW FINDINGS AND CONCLUSIONS: Rapid changes were observed in numerous aspects of OUDs during the early pandemic stage, as well as its care by nursing and other health professionals. These changes include increased overdoses (primarily from synthetic opioids such as fentanyl) and emergency department visits. These trends varied considerably across U.S. jurisdictions, underscoring the importance of region-specific examinations for public health policy and intervention. Out of necessity, healthcare systems and nursing professionals adapted to the challenges of OUD care in the pandemic. These adaptations included increases in telehealth services, increases in take-home doses of methadone or buprenorphine/naloxone, and expansion of layperson training in the use of naloxone for overdose reversal. It is likely that some of these adaptations will result in long-term changes in standards of care practices for OUDs by nursing professionals.

Serum cytokine and inflammatory markers in individuals with heroin use disorder: potential biomarkers for diagnosis and disease severity.

Opioid use disorders cause major morbidity and mortality, and there is a pressing need for novel mechanistic targets and biomarkers for diagnosis and prognosis. Exposure to mu-opioid receptor (MOR) agonists causes changes in cytokine and inflammatory protein networks in peripheral blood, and also in brain glia and neurons. Individuals with heroin use disorder (iHUD) show dysregulated levels of several cytokines in blood. However, there is limited data on a comprehensive panel of such markers in iHUD versus healthy controls (HC), especially as a multi-target biomarker. We used a validated proximity extension assay for relative quantification of 92 cytokines and inflammatory proteins in serum of iHUD on medication assisted therapy (MAT; n=21), versus HC (n=24). Twenty-nine targets showed significant group differences (primarily iHUD>HC), surviving multiple comparison correction (p=0.05). This included 19 members of canonical cytokine families, including specific chemokines, interleukins, growth factors, and tumor necrosis factor (TNF)-related proteins. For dimensionality reduction, data from these 19 cytokines were entered into a principal component (PC) analysis, and PC1 scores were iHUD>HC (p<0.0001). A receiver-operating characteristic (ROC) curve analysis yielded an AUROC=91.7% (p<0.0001). This PC1 score remained a positive predictor of being in the HUD group in a multivariable logistic regression, which included demographic/clinical variables. Overall, this study shows a panel of cytokines that differ significantly between iHUD and HC, and provides a multi-target "cytokine biomarker score" for potential diagnostic purposes, and examination of disease severity.

ScISOr-ATAC reveals convergent and divergent splicing and chromatin specificities between matched cell types across cortical regions, evolution, and in Alzheimer's Disease.

Multimodal measurements have become widespread in genomics, however measuring open chromatin accessibility and splicing simultaneously in frozen brain tissues remains unconquered. Hence, we devised Single-Cell-ISOform-RNA sequencing coupled with the Assay-for-Transposase-Accessible-Chromatin (ScISOr-ATAC). We utilized ScISOr-ATAC to assess whether chromatin and splicing alterations in the brain convergently affect the same cell types or divergently different ones. We applied ScISOr-ATAC to three major conditions: comparing (i) the Rhesus macaque (Macaca mulatta) prefrontal cortex (PFC) and visual cortex (VIS), (ii) cross species divergence of Rhesus macaque versus human PFC, as well as (iii) dysregulation in Alzheimer's disease in human PFC. We found that among cortical-layer biased excitatory neuron subtypes, splicing is highly brain-region specific for L3-5/L6 IT_RORB neurons, moderately specific in L2-3 IT_CUX2.RORB neurons and unspecific in L2-3 IT_CUX2 neurons. In contrast, at the chromatin level, L2-3 IT_CUX2.RORB neurons show the highest brain-region specificity compared to other subtypes. Likewise, when comparing human and macaque PFC, strong evolutionary divergence on one molecular modality does not necessarily imply strong such divergence on another molecular level in the same cell type. Finally, in Alzheimer's disease, oligodendrocytes show convergently high dysregulation in both chromatin and splicing. However, chromatin and splicing dysregulation most strongly affect distinct oligodendrocyte subtypes. Overall, these results indicate that chromatin and splicing can show convergent or divergent results depending on the performed comparison, justifying the need for their concurrent measurement to investigate complex systems. Taken together, ScISOr-ATAC allows for the characterization of single-cell splicing and chromatin patterns and the comparison of sample groups in frozen brain samples.

Impact of OPRM1 (Mu-opioid Receptor Gene) A112G Polymorphism on Dual Oxycodone and Cocaine Self-administration Behavior in a Mouse Model.

The use of mu-opioid receptor (MOP-r) agonists such as oxycodone together with cocaine is prevalent, and deaths attributed to using these combinations have increased. RATIONALE: It is unknown if functional single nucleotide polymorphisms (SNPs), such as the OPRM1 (MOP-r gene) SNP A118G, can predispose individuals to more dual opioid and psychostimulant intake. The dual self-administration (SA) of MOP-r agonists and cocaine has not been thoroughly examined, especially with regard to neurobiological changes. OBJECTIVES: We examined oxycodone SA and subsequent dual oxycodone and cocaine SA in male and female A112G (A/G and G/G, heterozygote and homozygote, respectively) mice, models of human A118G carriers, versus wild-type (A/A) mice. METHODS: Adult male and female A/G, G/G and A/A mice self-administered oxycodone (0.25 mg/kg/infusion, 4hr/session, FR 1.) for 10 consecutive days (sessions 1-10). Mice then self-administered cocaine (2 hr) following oxycodone SA (4 hr, as above) in each session for a further 10 consecutive days (sessions 11-20). Message RNA transcripts of 24 reward-related genes were examined in the dorsal striatum. RESULTS: Male and female A/G and G/G mice had greater oxycodone SA than A/A mice did in the initial 10 days and in the last 10 sessions. Further, A/G and G/G mice showed greater cocaine intake than A/A mice. Dorsal striatal mRNA levels of Pdyn, Fkbp5, Oprk1, and Oprm1 were altered following oxycodone and cocaine SA. CONCLUSIONS: These studies demonstrated that this functional genetic variation in Oprm1 affected dual opioid and cocaine SA and altered specific gene expression in the striatum.

Effect of prenatal and early post-natal oxycodone exposure on the reinforcing and antinociceptive effects of oxycodone in adult C57BL/6 J mice.

Abuse of opioids (mu-opioid agonists such as oxycodone) among parents during the gestation and early post-natal period is a concern for the long-term health of the offspring, beyond potential neonatal withdrawal symptoms. However, there is only limited information on such effects. OBJECTIVES: We examined how prenatal, and early-post natal oxycodone exposure affected opioid addiction behaviors. METHODS: Adult male and female C57BL/CJ mice housed separately were first injected with ascending doses of oxycodone 1 time/day (1 mg/kg × 10 days, 1.5 mg/kg × 10 days, 2 mg/kg × 10 days, s.c.) whereas control mice were injected with saline. Newly formed parental dyads were then housed together and continued to receive ascending doses of oxycodone (3 mg/kg × 10 days, 4 mg/kg × 10 days, 5 mg/kg × 10 days, 6 mg/kg × 10 days or saline, s.c.) or saline during mating and gestation until the birth of the litter. The dams continued to receive oxycodone or saline through lactation, until F1 offspring were weaned. Upon reaching adulthood (12 weeks of age), male and female F1 offspring were examined in intravenous self-administration (IVSA) of oxycodone, on oxycodone-induced conditioned place preference (CPP) and oxycodone-induced antinociception. RESULTS: Adult F1 male and female offspring of parental dyads exposed to oxycodone self-administered more oxycodone, compared to offspring of control parental dyads. Ventral and dorsal striatal mRNA levels of genes such as Fkbp5 and Oprm1 were altered following oxycodone self-administration. CONCLUSION: Prenatal and early post-natal oxycodone exposure enhanced oxycodone self-administration during adulthood in the C57BL/6 J mice.

Neuroimmune Mechanisms of Opioid Use Disorder and Recovery: Translatability to Human Studies, and Future Research Directions.

Opioid use disorder (OUD) is a major current cause of morbidity and mortality. Long-term exposure to short-acting opioids (MOP-r agonists such as heroin or fentanyl) results in complex pathophysiological changes to neuroimmune and neuroinflammatory functions, affected in part by peripheral mechanisms (e.g., cytokines in blood), and by neuroendocrine systems such as the hypothalamic-pituitary-adrenal (HPA) stress axis. There are important findings from preclinical models, but their role in the trajectory and outcomes of OUD in humans is not well understood. The goal of this narrative review is to examine available data on immune and inflammatory functions in persons with OUD, and to identify major areas for future research. Peripheral blood biomarker studies revealed a pro-inflammatory state in persons with OUD in withdrawal or early abstinence, consistent with available postmortem brain studies (which show glial activation) and diffusion tensor imaging studies (indicating white matter disruptions), with gradual abstinence-associated recovery. The mechanistic roles of these neuroimmune and neuroinflammatory changes in the trajectory of OUD (including recovery and medication management) cannot be examined practically with postmortem data. Collection of longitudinal data in larger-scale human cohorts would allow examination of these mechanisms associated with OUD stage and progression. Given the heterogeneity in presentation of OUD, a precision medicine approach integrating multi-omic peripheral biomarkers and comprehensive phenotyping, including neuroimaging, can be beneficial in risk stratification, and individually optimized selection of interventions for individuals who will benefit, and assessments under refractory therapy.

Overdose mortality rates for opioids and stimulant drugs are substantially higher in men than in women: state-level analysis.

Drug overdoses from opioids and stimulants are a major cause of mortality in the United States. It is unclear if there are stable sex differences in overdose mortality for these drugs across states, whether these differ across the lifespan, and if so, whether they can be accounted for by different levels of drug misuse. This was a state-level analysis of epidemiological data on overdose mortality, across 10-year age bins (age range: 15-74), using the CDC WONDER platform for decedents in the United States in 2020-1. The outcome measure was rate of overdose death (per 100,000) for: synthetic opioids (e.g., fentanyl), heroin, psychostimulants with potential for misuse (e.g., methamphetamine), and cocaine. Multiple linear regressions controlled for ethnic-cultural background, household net worth, and sex-specific rate of misuse (from NSDUH, 2018-9). For all these drug categories, males had greater overall overdose mortality than females, after controlling for rates of drug misuse. The mean male/female sex ratio of mortality rate was relatively stable across jurisdictions: synthetic opioids (2.5 [95% CI, 2.4-7]), heroin, (2.9 [95% CI, 2.7-3.1], psychostimulants (2.4 [95% CI, 2.3-5]), and cocaine (2.8 [95% CI, 2.6-9]). With data stratified in 10-year age bins, the sex difference generally survived adjustment (especially in the 25-64 age range). Results indicate that males are significantly more vulnerable than females to overdose deaths caused by opioid and stimulant drugs, taking into account differing state-level environmental conditions and drug misuse levels. These results call for research into diverse biological, behavioral, and social factors that underlie sex differences in human vulnerability to drug overdose.

The Kappa Opioid Receptor Agonist 16-Bromo Salvinorin A Has Anti-Cocaine Effects without Significant Effects on Locomotion, Food Reward, Learning and Memory, or Anxiety and Depressive-like Behaviors.

Kappa opioid receptor (KOR) agonists have preclinical antipsychostimulant effects; however, adverse side effects have limited their therapeutic development. In this preclinical study, conducted in Sprague Dawley rats, B6-SJL mice, and non-human primates (NHPs), we evaluated the G-protein-biased analogue of salvinorin A (SalA), 16-bromo salvinorin A (16-BrSalA), for its anticocaine effects, side effects, and activation of cellular signaling pathways. 16-BrSalA dose-dependently decreased the cocaine-primed reinstatement of drug-seeking behavior in a KOR-dependent manner. It also decreased cocaine-induced hyperactivity, but had no effect on responding for cocaine on a progressive ratio schedule. Compared to SalA, 16-BrSalA had an improved side effect profile, with no significant effects in the elevated plus maze, light-dark test, forced swim test, sucrose self-administration, or novel object recognition; however, it did exhibit conditioned aversive effects. 16-BrSalA increased dopamine transporter (DAT) activity in HEK-293 cells coexpressing DAT and KOR, as well as in rat nucleus accumbens and dorsal striatal tissue. 16-BrSalA also increased the early phase activation of extracellular-signal-regulated kinases 1 and 2, as well as p38 in a KOR-dependent manner. In NHPs, 16-BrSalA caused dose-dependent increases in the neuroendocrine biomarker prolactin, similar to other KOR agonists, at doses without robust sedative effects. These findings highlight that G-protein-biased structural analogues of SalA can have improved pharmacokinetic profiles and fewer side effects while maintaining their anticocaine effects.

Overdose mortality rates for opioids or stimulants are higher in males than females, controlling for rates of drug misuse: State-level data.

Importance: Drug overdoses from opioids like fentanyl and heroin and stimulant drugs such as methamphetamine and cocaine are a major cause of mortality in the United States, with potential sex differences across the lifespan. Objective: To determine overdose mortality for specific drug categories across the lifespan of males and females, using a nationally representative state-level sample. Design: State-level analyses of nationally representative epidemiological data on overdose mortality for specific drug categories, across 10-year age bins (age range: 15-74). Setting: Population-based study of Multiple Cause of Death 2020-2021 data from the Centers of Disease Control and Prevention (CDC WONDER platform). Participants: Decedents in the United States in 2020-2021. Main outcome measures: The main outcome measure was sex-specific rates of overdose death (per 100,000) for: synthetic opioids excluding methadone (ICD-10 code: T40.4; predominantly fentanyl), heroin (T40.1), psychostimulants with potential for misuse, excluding cocaine (T43.6, predominantly methamphetamine; labeled "psychostimulants" hereafter), and cocaine (T40.5). Multiple regression analyses were used to control for ethnic-cultural background, household net worth, and sex-specific rate of misuse of the relevant substances (from the National Survey on Drug Use and Health, 2018-2019). Results: For each of the drug categories assessed, males had greater overall overdose mortality than females, after controlling for rates of drug misuse. The mean male/female sex ratio of mortality rate for the separate drug categories was relatively stable across jurisdictions: synthetic opioids (2.5 [95%CI, 2.4-2.7]), heroin, (2.9 [95%CI, 2.7-3.1], psychostimulants (2.4 [95%CI, 2.3-2.5]), and cocaine (2.8 [95%CI, 2.6-2.9]). With data stratified in 10-year age bins, the sex difference generally survived adjustment for state-level ethnic-cultural and economic variables, and for sex-specific misuse of each drug type (especially for bins in the 25-64 age range). For synthetic opioids, the sex difference survived adjustment across the lifespan (i.e., 10-year age bins ranging from 15-74), including adolescence, adulthood and late adulthood. Conclusions and Relevance: The robustly greater overdose mortality in males versus females for synthetic opioids (predominantly fentanyl), heroin, and stimulant drugs including methamphetamine and cocaine indicate that males who misuse these drugs are significantly more vulnerable to overdose deaths. These results call for research into diverse biological, behavioral, and social factors that underlie sex differences in human vulnerability to drug overdose.

Has the United States Reached a Plateau in Overdoses Caused by Synthetic Opioids After the Onset of the COVID-19 Pandemic? Examination of Centers for Disease Control and Prevention Data to November 2021.

Background: Overdoses caused by synthetic mu-opioid receptor (MOR) agonists such as fentanyl are causing increasing mortality in the United States. The COVID-19 pandemic continues to have complex effects on public health, including opioid use disorders (OUD). It is unclear whether recent increases in mortality caused by synthetic opioids have reached a plateau (i.e., a stable period), after the onset of the COVID-19 pandemic. Method: This study examined provisional overdose mortality data from the Centers for Disease Control and Prevention, for synthetic opioids excluding methadone (code T40.4; monthly data available from 39 States, plus New York City and Washington DC), for June 2019-November 2021. Data were first examined as crude mortality rates. The presence of a maximum plateau was analyzed for the last 4 months of available data. For authorities in which a plateau in mortality was detected, sigmoidal Boltzmann equations were used to model parameters of this phenomenon (e.g., level of the plateau). Results: At the end of the study period, all but one authority (New Hampshire) reported increases in mortality rates for synthetic opioids, compared to the baseline month of June 2019 (range: 111-745% of baseline). A plateau was observed over the last 4 months of the study period (Aug 2021-Nov 2021) in 29 of the authorities. Ten other authorities had not reached a stable plateau at the end of the study period. For the authorities where a plateau was detected, a sigmoidal Boltzmann model revealed a fitted maximum of 262% rise in mortality over the study period, from the baseline month. The midpoint in the rise in mortality was fitted in September 2020. After separation of data into census regions, the highest plateau was observed in the West region, followed by South, Midwest, and Northeast (fitted plateau values were 409, 262, 204, and 149% of baseline, respectively). Discussion: There were increases in overdose mortality due to synthetic opioids across most states, ranging considerably in magnitude. A plateau in overdose mortality was detected at the end of the study period in most of these authorities. The reasons for these plateaus should be explored, in order to develop optimized public health interventions.

Characterization of Pyrrolidinyl-hexahydro-pyranopiperazines as a Novel Kappa Opioid Receptor Agonist Scaffold.

The kappa agonist structure-activity relationship around the novel, pyrrolidinyl substituted pyranopiperazine scaffold was developed. More specifically, the dichloroPhenylAcetamide-Pyrrolidinyl-PyranoPiperazine (PAPPP) core A was the focus of our work. The modulation of kappa receptor potency/G-protein activation and arrestin recruitment with respect to changes of the piperazine R group in A was demonstrated. Reduced ß2-arrestin recruitment and differential G-protein bias were observed for select analogues. To better understand the subtlety in receptor signaling, analogues were profiled as the resolved enantiomers. To determine in vivo target engagement, a subset of compounds was tested in mice for stimulation of serum prolactin, a neuroendocrine biomarker of KOR-agonist effects. Additional in vivo characterization included measurement of potential unwanted effects of kappa receptor activation such as sedation. These studies demonstrate a novel kappa receptor agonist scaffold with potential for G-protein signaling bias to probe in vivo pharmacology.

Analyses of polymorphisms of intron 2 of OPRK1 (kappa-opioid receptor gene) in association with opioid and cocaine dependence diagnoses in an African-American population.

RATIONALE: The dynorphin/kappa-opioid receptor (KOR) system (encoded by PDYN and OPRK1 genes respectively) is highly regulated by repeated exposure to drugs of abuse, including mu-opioid agonists and cocaine. These changes in the dynorphin/KOR system can then influence the rewarding effects of these drugs of abuse. Activation of the dynorphin/KOR system is also thought to have a role in the pro-addictive effects of stress. Recent in vitro assays showed that the OPRK1 intron 2 may function as a genomic enhancer in the regulation KOR expression, and contains a glucocorticiod-responsive sequence site. We hypothesize that SNPs in intron 2 of OPRK1 are associated with categorical opioid or cocaine dependence diagnoses, as well as with dimensional aspects of drug use (i.e., magnitude of drug exposure). METHODS: This study includes 577 subjects ≥ 18 years old, with African ancestry (AA) from the USA. They were divided into three groups: 152 control subjects, 142 persons with lifetime opioid dependence diagnosis (OD), and 283 subjects with lifetime cocaine dependence diagnosis (CD). Five SNPs (rs16918909, rs7016778, rs997917, rs6473797, rs10111937) that span 10 Kb nucleotides in intron 2 of OPRK1 were used for the association analyses. Genotyping was performed with the Smokescreen® array or sequencing of PCR-amplified DNA fragments. Association analyses for OD and CD diagnoses and the OPRK1 intron 2 alleles were carried out with Fisher's exact test. The Kreek-McHugh-Schluger-Kellogg (KMSK) scales were used for dimensional measure of maximum exposure to specific drugs, using Mann-Whitney tests. RESULTS: Two SNPs, rs997917 and rs10111937 showed point-wise significant allelic association (p < 0.05) with CD diagnosis, and rs10111937 showed a point-wise significance in association with OD. None of these single SNP associations with categorical diagnoses were significant after correction for multiple testing (pcorr > 0.05). However, significant associations of several genotype patterns (diplotypes) were found with cocaine dependence, but none for opioid dependence. The most significant genotype pattern with cocaine dependence diagnosis occurred for rs6473797 and rs10111937 (pcorr = 0.036, odds ratio = 1.92, FDR < 0.05), and survived correction for multiple testing. Dimensional analyses with KMSK scores show that persons with either rs997917 or rs10111937 variants had greater exposure to cocaine, compared to those with prototype allele (Mann-Whitney tests, point-wise). CONCLUSIONS: This study provides additional support of potential importance of regulatory regions of intron 2 of the OPRK1 gene in development of cocaine and opioid dependence diagnoses, in a population with African-American ancestry.

Bidirectional influence of heroin and cocaine escalation in persons with dual opioid and cocaine dependence diagnoses.

Persons with dual severe opioid and cocaine use disorders are at risk of considerable morbidity, and the bidirectional relationship of escalation of mu-opioid agonists and cocaine use is not well understood. The aim of this study was to examine the bidirectional relationship between escalation of heroin and cocaine use in volunteers dually diagnosed with opioid and cocaine dependence (OD + CD). Volunteers from New York with OD + CD (total n = 295; male = 182, female = 113; age ≥ 18 years) were interviewed with the Structured Clinical Interview for the DSM-IV Axis I Disorders and Kreek-McHugh-Schluger-Kellogg scales for dimensional measures of drug exposure, which also collect ages of 1st use and onset of heaviest use. Time of escalation was defined as age of onset of heaviest use minus age of 1st use in whole years. Times of escalation of heroin and cocaine were positively correlated in both men (Spearman r = .34, 95% confidence interval [CI: .17, .48], p < .0001) and women (Spearman r = .51, [.27, .50], p < .0001) volunteers. After we adjusted for demographic variables, a Cox regression showed that time of cocaine escalation was a predictor of time of heroin escalation (hazard ratio [HR] = 0.97, 95% CI [0.95, 0.99], p = .003). Another Cox regression showed that this relationship is bidirectional, because time of heroin escalation was also a predictor of time of cocaine escalation (HR = 0.98, [0.96-0.99], p = .016). In these adjusted models, gender was not a significant predictor of time of escalation of either heroin or cocaine. Therefore, escalation did not differ robustly by gender when adjusting for demographics and other major variables. Overall, rapid escalation of cocaine use was a predictor of rapid escalation of heroin use, and vice versa, in persons with dual severe opioid and cocaine use disorders. These findings suggest a shared vulnerability to rapid escalation of these 2 drugs in persons with dual severe opioid and cocaine use disorders. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Kappa Opioid Receptor Antagonists as Potential Therapeutics for Mood and Substance Use Disorders.

The kappa opioid receptor (KOR) and its primary cognate ligands, the dynorphin peptides, are involved in diverse physiological processes. Disruptions to the KOR/dynorphin system have been found to likely play a role in multiple neuropsychological disorders, and hence KOR has emerged as a potential therapeutic target. Targeting KOR is complicated by close homology to the mu and delta opioid receptors (MOR and DOR), and many KOR ligands have at least moderate affinity to MOR and/or DOR. Animal models utilizing primarily very long-lasting selective KOR antagonists (>3 weeks following a single dose) have demonstrated that KOR antagonism attenuates certain anxiety-like and depression-like behaviors and blocks stress- and cue-induced reinstatement to drug seeking. Recently, relatively selective KOR antagonists with medication-like pharmacokinetic and pharmacodynamic properties and durations of action have been developed. One of these, JNJ-67953964 (also referred to as CERC-501, LY2456302, OpraKappa or Aticaprant) has been studied in humans, and shown to be safe, relatively KOR selective, and able to substantially attenuate binding of a KOR PET tracer to CNS localized KOR for greater than 24 h. While animal studies have indicated that compounds of this structural class are capable of normalizing withdrawal signs in animal models of cocaine and alcohol dependence and reducing cocaine and alcohol intake/seeking, additional studies are needed to determine the value of these second generation KOR antagonists in treating mood disorders and substance use disorders in humans.

Rapid-Onset Anti-Stress Effects of a Kappa-Opioid Receptor Antagonist, LY2795050, Against Immobility in an Open Space Swim Paradigm in Male and Female Mice.

The kappa-opioid receptor (KOR) / dynorphin system is implicated with behavioral and neurobiological effects of stress exposure (including heavy exposure to drugs of abuse) in translational animal models. Thus some KOR-antagonists can decrease the aversive, depressant-like and anxiety-like effects caused by stress exposure. The first generation of selective KOR-antagonists have slow onsets (hours) and extremely long durations of action (days-weeks), in vivo. A new generation of KOR antagonists with rapid onset and shorter duration of action can potentially decrease the effects of stress exposure in translational models, and may be of interest for medication development. This study examined the rapid onset anti-stress effects of one of the shorter acting novel KOR-antagonists (LY2795050, (3-chloro-4-(4-(((2S)-2-pyridin-3-ylpyrrolidin-1-yl)methyl) phenoxy)benzamide)) in a single-session open space swim (OSS) stress paradigm (15 min duration), in adult male and female C57BL/6 J mice. LY2795050 (0.32 mg/kg, i.p.) had rapid onset (within 15 min) and short duration (<3 h) of KOR-antagonist effects, based on its blockade of the locomotor depressant effects of the KOR-agonist U50,488 (10 mg/kg). LY2795050 (0.32 mg/kg), when administered only 1 min prior to the OSS stress paradigm, decreased immobility in males, but not females. With a slightly longer pretreatment time (15 min), this dose of LY2795050 decreased immobility in both males and females. A 10-fold smaller dose of LY2795050 (0.032 mg/kg) was inactive in the OSS, showing dose-dependence of this anti-stress effect. Overall, these studies show that a novel KOR-antagonist can produce very rapid onset anti-immobility effects in this model of acute stress exposure.

Design, synthesis, and preliminary evaluation of a potential synthetic opioid rescue agent.

BACKGROUND: One of the most prominent opioid analgesics in the United States is the high potency agonist fentanyl. It is used in the treatment of acute and chronic pain and as an anesthetic adjuvant. When used inappropriately, however, ingestion of just a few milligrams of fentanyl or other synthetic opioid can cause opioid-induced respiratory depression (OIRD), often leading to death. Currently, the treatment of choice for OIRD is the opioid receptor antagonist naloxone. Recent reports, however, suggest that higher doses or repeated dosing of naloxone (due to recurrence of respiratory depression) may be required to reverse fully fentanyl-induced respiratory depression, rendering this treatment inadequate. To combat this synthetic opioid overdose crisis, this research aims at identifying a novel opioid reversal agent with enhanced efficacy towards fentanyl and other synthetic opioids. METHODS: A series of naltrexone analogues were characterized for their ability to antagonize the effects of fentanyl in vitro utilizing a modified forskolin-induced cAMP accumulation assay. Lead analogue 29 was chosen to undergo further PK studies, followed by in vivo pharmacological analysis to determine its ability to antagonize opioid-induced antinociception in the hot plate assay. RESULTS: A series of potent MOR antagonists were identified, including the highly potent analogue 29 (IC50 = 2.06 nM). Follow-up PK studies revealed 29 to possess near 100% bioavailability following IP administration. Brain concentrations of 29 surpassed plasma concentrations, with an apparent terminal half-life of ~ 80 min in mice. In the hot plate assay, 29 dose-dependently (0.01-0.1 mg/kg; IP) and fully antagonized the antinociception induced by oxycodone (5.6 mg/kg; IP). Furthermore, the dose of 29 that is fully effective in preventing oxycodone-induced antinociception (0.1 mg/kg) was ineffective against locomotor deficits caused by the KOR agonist U50,488. CONCLUSIONS: Methods have been developed that have utility to identify enhanced rescue agents for the treatment of OIRD. Analogue 29, possessing potent MOR antagonist activity in vitro and in vivo, provides a promising lead in our search for an enhanced synthetic opioid rescue agent.

Age of onset of heaviest use of cannabis or alcohol in persons with severe opioid or cocaine use disorders.

BACKGROUND: Persons with severe opioid or cocaine use disorders are particularly vulnerable to morbidity and mortality. Heaviest use of mu-opioid receptor agonists and cocaine typically commences in early adulthood and is preceded by substantial adolescent exposure to cannabis and/or alcohol. Little information exists on the age trajectories of exposure to cannabis or alcohol in persons diagnosed with severe opioid or cocaine use disorders, compared to persons diagnosed with other substance use disorders (unrelated to opioids or cocaine). METHOD: This observational study had n = 854 volunteers (male = 581, female = 273; ≥18 years of age at the time of interview) and examined the ages of onset of heaviest use of cannabis and alcohol in persons diagnosed by DSM-IV criteria with opioid dependence (OD), both opioid and cocaine dependence (OD + CD) and cocaine dependence (CD). These age trajectory measures were compared to persons with other substance use disorders (primarily cannabis and alcohol use disorders, termed "Any Other Diagnoses"). RESULTS: Unadjusted survival analyses showed persons diagnosed with either OD + CD or CD had earlier onset of heaviest use of cannabis (mean ages of 16.2 and 17.8, respectively) compared to the "Any Other Diagnoses" reference group (mean age = 19.5). A multivariate logistic regression showed that later onset of heaviest use of cannabis was associated with lower odds of being in the OD + CD or CD groups, when compared to the reference group. CONCLUSIONS: Persons diagnosed with severe cocaine use disorders or dual opioid and cocaine use disorders exhibit a pattern of heavy and especially early adolescent exposure to cannabis, compared to persons with other substance use disorders.

Profile of a short-acting κ-antagonist, LY2795050, on self-grooming behaviors, forced swim test and locomotor activity: sex comparison in mice.

BACKGROUND: Novel short-acting κ(kappa)-opioid receptor selective antagonists are translational tools to examine the impact of the κ-receptor/dynorphin system in assays related to central nervous system dysfunction (e.g., substance use disorders, anhedonia and depression). The effects of such compounds have been compared in males and females under very limited conditions. AIMS: The goal of this study was to examine potential sex differences in the effects of a κ-agonist and a short-acting κ-antagonist in an ethologically relevant test of anhedonia, the "splash test" of self-grooming, and also in the forced swim test and in locomotor activity. METHODS: We examined the dose-dependence of grooming deficits caused by the κ-agonist U50,488 (0.1-3.2 mg/kg intraperitoneal (i.p.)) in gonadally intact adult male and female C57BL/6J mice. We then compared the effects of the short-acting κ-antagonist LY2795050 ((3-chloro-4-(4-(((2S)-2-pyridin-3-ylpyrrolidin-1-yl)methyl) phenoxy)benzamide)); 0.032-0.1 mg/kg i.p.) in blocking grooming deficits caused by U50,488 (3.2 mg/kg). The effects of LY2795050 were also studied in the forced swim test (FST). The effects of LY2795050 in blocking the locomotor depressant effects of U50,488 (10 mg/kg) were also studied. RESULTS: U50,488 produced dose-dependent grooming deficits in male and female mice, and LY2795050 prevented these effects. In contrast, LY2795050 decreased immobility in the FST in males at a dose of 0.1 mg/kg, but not in females, up to a dose of 0.32 mg/kg. Also, LY2795050 (0.32 mg/kg) prevented and also reversed the locomotor-depressant effects of U50,488 (10 mg/kg), in males and females. CONCLUSIONS: This study further implicates the κ-receptor system in ethologically relevant aspects of anhedonia, and confirms sexual dimorphism in some behavioral effects of novel κ-antagonists.

Association of Serotonin Transporter (SERT) Polymorphisms with Opioid Dependence and Dimensional Aspects of Cocaine Use in a Caucasian Cohort of Opioid Users.

INTRODUCTION: A functional tandem repeat polymorphism in the promoter of the serotonin transporter (SERT) gene (SLC6A4) has been studied for association to neuropsychiatric conditions, including substance use disorders. Short (S) forms of this repeat result in reduced transcription, and presumably greater synaptic levels of serotonin, which are involved in opioid and cocaine-induced reward. Dual exposure to heroin and cocaine is a common pattern of poly-drug use and is associated with considerable morbidity. We hypothesize that SLC6A4 variants are associated with cocaine exposure in subjects with an opioid dependence diagnosis (OD), and also in non-dependent opioid users (NOD). Other single nucleotide polymorphisms (SNPs) of SLC6A4 may also be likewise associated. MATERIALS AND METHODS: This study determined whether variants of the SLC6A4 promoter repeats and two intronic SNPs, rs16965628 and rs2066713, are associated with categorical diagnoses of opioid dependence (DSM-IV criteria) and with dimensional aspects of cocaine use, in a Caucasian cohort (n=591). Three groups of subjects were examined: (1) 276 subjects with opioid dependence diagnosis (OD); (2) 163 subjects who had used opioids for non-medical reasons but never had an opioid dependence diagnosis (NOD); (3) 152 healthy controls (HC). RESULTS: Aside from high exposure to heroin in the OD group, relatively high exposure to cocaine was detected in both OD and NOD groups. The SERT repeat genotype (classified as "long-long" [LL] versus "short-long" plus "short-short" [SL+SS]) was not associated with categorical opioid dependence diagnoses. A nominally significant association was identified with the [SL+SS] genotype of SLC6A4 and cocaine KMSK scores ≥"cutpoint" for a cocaine dependence diagnosis (p=0.026). The [SL+SS] genotype was associated with more rapid cocaine escalation than the LL genotype. No significant associations of rs16965628 and rs2066713 SNPs were found overall. CONCLUSION: The functional SERT promoter tandem repeat genotype may be associated to heavy cocaine exposure and more rapid escalation of cocaine use, in persons with and without opioid dependence diagnosis.

Relapse-like behavior in a mouse model of the OPRM1 (mu-opioid receptor) A118G polymorphism: Examination with intravenous oxycodone self-administration.

The widely abused prescription opioid oxycodone is a mu-opioid receptor (MOP-r) agonist and addiction to such opioids is a relapsing disorder. The human MOP-r gene (OPRM1) has an important functional single nucleotide polymorphism (SNP), A118G, which affects risk of severe opioid use disorders. A112G (G/G) knock-in mice are models of human A118G carriers. We examined oxycodone self-administration (SA) in male and female G/G versus wild type (A/A) mice in SA sessions and in relapse-like behavior. Adult male and female G/G and A/A mice self-administered oxycodone (0.25 mg/kg/infusion, FR1) for 10 consecutive days. Following 10-day home cage drug free withdrawal, the mice were re-exposed to oxycodone SA for a further 10 days. MOP-r receptor mRNA in various brain regions were examined immediately after the last re-exposure session. We found that G/G mice had greater oxycodone SA than A/A mice in the initial and in re-exposure sessions. Mice of both genotypes had greater oxycodone intake during the re-exposure period than during the initial exposure. We also detected differences in MOP-r gene expression due to genotype, sex and oxycodone SA history in the dorsal striatum, hippocampus, and prefrontal cortex. These studies may improve our understanding of MOP-r-agonist self-exposure and relapse in human carriers of the A118G SNP.