Search

Family and twin studies demonstrate that genetic factors determine 20-60% of the vulnerability to opioid use disorder. However, the genes/alleles that mediate the risk of developing addiction-related behaviors, including the sensitivity to the analgesic efficacy of opioids, the development of tolerance, dependence, and escalation of oxycodone taking and seeking, have been ill-defined, thus hindering efforts to design pharmacological interventions to enable precision medicine strategies. Here we characterized oxycodone addiction-like behaviors in heterogeneous stock (HS) rats, that show high genetic diversity that mimics the high genetic variability in humans. HS rats were allowed to self-administer oxycodone for two h/daily for four days (ShA) and then moved to 12h/daily (LgA) for 14 days. Animals were screened for motivation to self-administer oxycodone using a progressive-ratio (PR) schedule of reinforcement and for the development of withdrawal-induced hyperalgesia and tolerance to the analgesic effects of oxycodone using the von-Frey and tail immersion tests, respectively. To reduce cohort-specific effects, we used cohorts of 46-60 rats and normalized the response level within cohorts using a Z-score. To take advantage of the four opioid-related behaviors and further identify subjects that are consistently vulnerable vs. resilient to compulsive oxycodone use, we computed an Addiction Index by averaging normalized responding (Z-scores) for the four behavioral tests. Results showed high individual variability between vulnerable and resilient rats, likely to facilitate the detection of gene variants associated with vulnerable vs. resilient individuals. Such data will have considerable translational value for designing follow-up studies in humans.

RationaleCurrent medications for opioid use disorder include buprenorphine, methadone, and naltrexone. While these medications show significant efficacy in reducing craving and opioid use, there are substantial individual differences in response to these treatments in humans. The reason for such difference is poorly known.ObjectivesHere, we tested the hypothesis that similar individual differences may be observed in a large population of heterogenous stock rats, that have been bred to maximize genetic diversity, using a behavioral paradigm relevant to opioid use disorder.MethodsOver 500 rats were given intermittent (4d/week) and extended access (12h/day) to oxycodone self-administration for 14 sessions to establish oxycodone dependence and escalation of intake. We then measured the effect of buprenorphine (0.5mg/kg), methadone (3mg/kg) and naltrexone (3mg/kg) on the motivation to self-administer oxycodone by using a progressive ratio schedule of reinforcement.ResultsWe found that naltrexone and buprenorphine significantly decreased motivation to oxycodone rewards. While naltrexone reduced oxycodone intake in both males and females, systemic administration with buprenorphine reduced progressive ratio responses only in males. Methadone reduced motivation to oxycodone self-administration in nearly 25% of the population, without reaching statical significance. Our results showed that the efficacy of these medications depends on the severity of addiction like behaviors, indicated by the addiction index.ConclusionsThese results demonstrate individual differences in response to medications to treat opioid use disorder in a genetically diverse population of rats.

The gut brain axis is thought to play a role in behavior and physiological responses through chemical, immunological, and metabolite signaling. Antibiotics, diet, and drugs can alter the transit time of gut contents as well as the makeup of the microbiome. Heterogeneity in genetics and environment are also well-known factors involved in the initiation and perpetuation of substance use disorders. Few viable genetic or biological markers are available to identify individuals who are at risk of escalating opioid intake. Primarily, the addiction field has focused on the nervous system, limiting the discovery of peripheral factors that contribute to addiction. To address this gap, we characterized the microbiome before and after drug exposure, and after antibiotics depletion in male and female heterogenous stock rats to determine if microbiome constituents are protective of escalation. We hypothesized that individuals that are prone to escalation of opioid self-administration will have distinct microbial and metabolic profiles. The fecal microbiome and behavioral responses were measured over several weeks of oxycodone self-administration and after antibiotic treatment. Antibiotic treatment reduces circulating short-chain fatty acids (SCFA) by depleting microbes that ferment fiber into these essential signaling molecules for the gut-brain axis. Depletion of the microbiome increased oxycodone self-administration in a subpopulation of animals (Responders). Supplementation of SCFAs in antibiotic depleted animals decreased elevated oxycodone self-administration. Phylogenetic functional analysis reveals distinct metabolic differences in the subpopulations of animals that are sensitive to antibiotic depletion and animals rescued by SCFA supplementation. In conclusion, this study identifies pre-existing microbiome and metabolic vulnerabilities to escalation of oxycodone self-administration, demonstrates that escalation of oxycodone self-administration dysregulates the microbiome and metabolic landscape, and identifies a causal role of short-chain fatty acids in addiction-like behaviors.

An emerging element in psychiatry is the gut-brain-axis, the bi-directional communication pathways between the gut microbiome and the brain. A prominent hypothesis, mostly based on preclinical studies, is that individual differences in the gut microbiome composition and drug-induced dysbiosis may be associated with vulnerability to psychiatric disorders including substance use disorder. However, most studies used small sample size, ignored individual differences, or used animal models with limited relevance to addiction. Here, we test the hypothesis that pre-existing microbiome composition and drug-induced changes in microbiome composition can predict addiction-like behaviors using an advanced animal model of extended access to cocaine self-administration in a large cohort of heterogenous stock (HS) rats. Adult male and female HS rats were allowed to self-administer cocaine under short (2h/day) and long access (6h/day) for ~7 weeks under various schedule of reinforcement to identify individuals that are resistant or vulnerable to addiction-like behaviors and fecal samples were collected before the first session and after the last session to assess differences in the microbiome composition. Linear discriminant analysis (LDA) identified sex-dependent and sex-independent differences at the phylum, order, and species level that are differentially abundant in resistant vs. vulnerable individuals, including high level of actinobacteria both before the first exposure to cocaine and after 7 weeks of cocaine self-administration in resistant animals. Predictions of functional gene content using PICRUSt revealed differential regulation of short-chain fatty acid processing in the vulnerable group after self-administration. These results identify microbiome constituents as well as metabolic pathways that are associated with resistance or vulnerability to addiction-like behaviors in rats. Identification of microbes and tangential metabolic pathways involved in cocaine resilience/vulnerability may represent an innovative strategy for the development of novel biomarkers and medication for the treatment of cocaine use disorder.

In addition to its pleasurable effects, weight control is a significant contributor to initiation, maintenance and relapse of cocaine use. This suggests that individual differences in bodyweight control and feeding hormones, such as leptin may contribute to the vulnerability to cocaine use disorder. While pre-clinical studies have shown a mutually inhibitory relationship between leptin and cocaine, they have used small sample sizes and did not investigate individual differences in a large heterogeneous population. Here, we tested if individual differences in bodyweight and blood leptin level is associated with high or low vulnerability to addiction-like behaviors using data from 500 heterogenous stock rats and 160 blood samples from the Cocaine Biobank, using a model of extended access to intravenous self-administration of cocaine. Finally, we tested a separate cohort to evaluate the causal effect of exogenous leptin administration on cocaine seeking. Bodyweight, while changing due to cocaine self-administration in males, was not related to the vulnerability to addiction-like behavior. Blood leptin levels after ~6 weeks of cocaine self-administration did not correlate with addiction-like behaviors, however, baseline blood leptin levels before any access to cocaine negatively predicted addiction-like behavior. Finally, administration of leptin reduced cocaine intake after acute withdrawal and cocaine seeking after 6 weeks of protracted abstinence. These results demonstrate that high blood leptin level before access to cocaine may be a protective factor against the development of cocaine addiction-like behavior, that exogenous leptin reduces the motivation to take and seek cocaine, but that blood leptin level and bodyweight changes in current users are not good biomarkers for addiction-like behaviors.

The gut-brain axis is a bi-directional communication system through which microbial communities in the gut interact with the nervous system, perhaps influencing neuropsychiatric disorders such as drug abuse. This study used behavioral data and biological samples from the Cocaine Biobank to test the hypothesis that the gut microbiota can predict and reflect susceptibility to cocaine reinforcement. Adult male heterogenous rats were catheterized and allowed to self-administer cocaine in short-access sessions (2 hr/day, 10 days, 0.5 mg/kg per intravenous infusion), followed by progressive ratio (PR) tests, long-access sessions (6 hr/day, 14 days), and alternating blocks of PR, long-access, and footshock testing. Fecal samples were collected at three time points and bacterial 16s rRNA genes were sequenced to profile the microbiota. As expected, cocaine-related behavior varied among subjects, such that a quartile split identified low and high responders on each measure, as well as an overall addiction index. Although beta diversity in the microbiota at baseline and after short access did not predict membership in high or low addiction quartiles, linear discriminant analysis (LDA) identified taxa that were more robustly represented in low or high responders. Beta diversity after long access was different among quartiles, as were several specific taxa. Investigation of baseline differences revealed that high relative abundance of Akkermansia muciniphila predicted future low response rates, whereas Ruminococcaceae predicted high response. This study is the first to report that microbiota variability reflects levels of cocaine intake and that microbial profiles might facilitate diagnosis and identify risk factors predictive of drug vulnerability.Significance StatementMicrobial organisms inhabiting the gut of animals appear to influence organismal function through various signaling pathways, ultimately affecting behavior and disease vulnerability. This experiment investigates links between gut bacteria and vulnerability to addiction-related behaviors in adult male rats. Not only did gut bacterial profiles change as a result of cocaine intake but also gut bacterial profiles before any exposure to cocaine predicted which animals would be high or low addiction-prone individuals. These results suggest that microbial profiles might facilitate diagnosis and identify risk factors predictive of drug addiction.

Visual Abstract, The rat oxycodone and cocaine biobanks contain samples that vary by genotypes (by using genetically diverse genotyped HS rats), phenotypes (by measuring addiction-like behaviors in an advanced SA model), timepoints (samples are collected longitudinally before, during, and after SA, and terminally at three different timepoints in the addiction cycle: intoxication, withdrawal, and abstinence or without exposure to drugs through age-matched naive rats), samples collected (organs, cells, biofluids, feces), preservation (paraformaldehyde-fixed, snap-frozen, or cryopreserved) and application (proteomics, transcriptomics, microbiomics, metabolomics, epigenetics, anatomy, circuitry analysis, biomarker discovery, etc. Substance use disorders (SUDs) are pervasive in our society and have substantial personal and socioeconomical costs. A critical hurdle in identifying biomarkers and novel targets for medication development is the lack of resources for obtaining biological samples with a detailed behavioral characterization of SUD. Moreover, it is nearly impossible to find longitudinal samples. As part of two ongoing large-scale behavioral genetic studies in heterogeneous stock (HS) rats, we have created two preclinical biobanks using well-validated long access (LgA) models of intravenous cocaine and oxycodone self-administration (SA) and comprehensive characterization of addiction-related behaviors. The genetic diversity in HS rats mimics diversity in the human population and includes individuals that are vulnerable or resilient to compulsive-like responding for cocaine or oxycodone. Longitudinal samples are collected throughout the experiment, before exposure to the drug, during intoxication, acute withdrawal, and protracted abstinence, and include naive, age-matched controls. Samples include, but are not limited to, blood plasma, feces and urine, whole brains, brain slices and punches, kidney, liver, spleen, ovary, testis, and adrenal glands. Three preservation methods (fixed in formaldehyde, snap-frozen, or cryopreserved) are used to facilitate diverse downstream applications such as proteomics, metabolomics, transcriptomics, epigenomics, microbiomics, neuroanatomy, biomarker discovery, and other cellular and molecular approaches. To date, >20,000 samples have been collected from over 1000 unique animals and made available free of charge to non-profit institutions through https://www.cocainebiobank.org/ and https://www.oxycodonebiobank.org/.

BackgroundAlcohol binge drinking in humans is thought to increase the risk for alcohol use disorder (AUD). Unclear is whether drinking patterns (e.g., bingelike or stable drinking) differentially affect the transition to compulsive-like drinking in dependent individuals. We examined whether chronic bingelike drinking facilitates the transition to compulsive-like drinking in rats.MethodsMale Wistar rats were given 5months of intermittent access to ethanol (EtOH) (IAE) or continuous access to EtOH (CAE) in a 2-bottle choice paradigm. Then, rats were given chronic intermittent EtOH (CIE) vapor exposure. Escalation of EtOH intake and compulsive-like responding for EtOH, using a progressive-ratio schedule of reinforcement and quinine-adulterated EtOH, were measured.ResultsIAE rats escalated EtOH drinking after 2weeks of 2-bottle choice, whereas CAE rats exhibited stable EtOH drinking for 5months. After 8weeks of CIE, both IAE+CIE and CAE+CIE rats escalated their EtOH intake. However, IAE rats escalated their EtOH intake weeks sooner than CAE rats and exhibited greater EtOH intake. No differences in compulsive-like responding were found between IAE+CIE and CAE+CIE rats. However, both IAE+CIE and CAE+CIE rats showed strong compulsive-like responding compared with rats without prior IAE or CAE.ConclusionsChronic EtOH drinking at stable or escalated levels for several months is associated with more compulsive-like responding for EtOH in rats that are exposed to CIE compared with rats without a prior history of EtOH drinking. Moreover, IAE facilitated the transition to compulsive-like responding for EtOH after CIE exposure, reflected by the escalation of EtOH intake. These results suggest that IAE may facilitate the transition to AUD. This study indicates that despite a moderate level of EtOH drinking, the IAE animal model is highly relevant to early stages of alcohol abuse and suggests that it may be associated with neuroadaptations that produce a faster transition to alcohol dependence.

Abstinence from alcohol is associated with the recruitment of neurons in the central nucleus of the amygdala (CeA) in nondependent rats that binge drink alcohol and in alcohol-dependent rats. However, whether the recruitment of this neuronal ensemble in the CeA is causally related to excessive alcohol drinking or if it represents a consequence of excessive drinking remains unknown. We tested the hypothesis that the recruitment of a neuronal ensemble in the CeA during abstinence is required for excessive alcohol drinking in nondependent rats that binge drink alcohol and in alcohol-dependent rats. We found that inactivation of the CeA neuronal ensemble during abstinence significantly decreased alcohol drinking in both groups. In nondependent rats, the decrease in alcohol intake was transient and returned to normal the day after the injection. In dependent rats, inactivation of the neuronal ensemble with Daun02 produced a long-term decrease in alcohol drinking. Moreover, we observed a significant reduction of somatic withdrawal signs in dependent animals that were injected with Daun02 in the CeA. These results indicate that the recruitment of a neuronal ensemble in the CeA during abstinence from alcohol is causally related to excessive alcohol drinking in alcohol-dependent rats, whereas a similar neuronal ensemble only partially contributed to alcohol-binge-like drinking in nondependent rats. These results identify a critical neurobiological mechanism that may be required for the transition to alcohol dependence, suggesting that focusing on the neuronal ensemble in the CeA may lead to a better understanding of the etiology of alcohol use disorders and improve medication development.SIGNIFICANCE STATEMENTAlcohol dependence recruits neurons in the central nucleus of the amygdala (CeA). Here, we found that inactivation of a specific dependence-induced neuronal ensemble in the CeA reversed excessive alcohol drinking and somatic signs of alcohol dependence in rats. These results identify a critical neurobiological mechanism that is required for alcohol dependence, suggesting that targeting dependence neuronal ensembles may lead to a better understanding of the etiology of alcohol use disorders, with implications for diagnosis, prevention, and treatment.

This study explores a management education model to help integrate sustainable development ideas into university curricula and programs. This pedagogical model emphasizes a community-based approach along with other proven methods for university-community collaborations and course-based social impact analysis. The Laudato Si’ encyclical’s notion of integral ecology, along with the need to create community-benefit academic programs, inspired the establishment of a partnership between the University of San Francisco’s Master of Nonprofit Administration program and the Foundation for Sustainability Development. This partnership experience expanded into development practicum courses and solidified into strategies for integrating experiential learning and organizational development through community-based analysis. The graduate level pedagogical models discussed here are relevant to other academic institutions and programs who would like to educate students with a community-centered approach.

Background Animal models of alcohol dependence suggest that long-term alterations in brain corticotropin-releasing factor (CRF) systems, key mediators of the behavioral stress response, may be involved in the development and reinstatement of dependence on drugs of abuse. The objective of the present study was to investigate the role of CRF in the regulation of ethanol self-administration and to examine the behavioral stress response during acute withdrawal and protracted abstinence. Methods Male Wistar rats were made dependent on ethanol via chronic exposure to ethanol vapor. Ethanol self-administration and exploratory behavior in the elevated plus maze were measured at 2 hr and 3 to 5 weeks after exposure. The role of CRF in ethanol self-administration was examined via central injection of the CRF receptor antagonist D-Phe-CRF(12–41). Results Rats showed increased responding for ethanol 2 hr and 3 to 5 weeks after chronic ethanol exposure, which was attenuated by central injection of D-Phe-CRF(12–41). In addition, rats displayed a decrease in open-arm exploration in the elevated plus maze when tested 2 hr and 4 weeks after exposure. Conclusions These results indicate that chronic ethanol exposure leads to increased ethanol self-administration and decreased open-arm exploration in the elevated plus maze during acute withdrawal and protracted abstinence. Attenuation of ethanol self-administration via central injection of D-Phe-CRF(12–41) implicates CRF as an underlying mechanism regulating long-term motivational effects associated with alcohol dependence.

In the quickly changing world of acquisitions, librarians must adapt to dealing simultaneously with the traditional world of print resources and its players and the emerging world of electronic resources and its players. This workshop described the resultant changes in workflow in an acquisitions department, discussed the desirable qualities an acquisitions librarian should possess, and identified the diverse set of players in the e-resources game.

Circulating levels of the cytokine interleukin 18 (IL-18) are elevated in obesity. Here, we show that administration of IL-18 suppresses appetite, feed efficiency, and weight regain in food-deprived male and female C57BL/6J mice. Intraperitoneal vs. intracerebroventricular routes of IL-18 administration had similar potency and did not promote formation of a conditioned taste aversion (malaise-like behavior). Mice partially ( Il18 +/− ) or totally ( Il18 −/− ) deficient in IL-18 were hyperphagic by young adulthood, with null mutants then becoming overweight by the fifth month of life. Adult Il18 −/− mice gained 2- to 3-fold more weight than WT mice per unit energy consumed of low- or high-fat diet. Indirect calorimetry revealed reduced energy expenditure in female Il18 −/− mice and increased respiratory exchange ratios [volume of carbon dioxide production (VCO 2 )/volume of oxygen consumption (VO 2 )] in mutants of both sexes. Hyperphagia continued in maturity, with overeating greatest during the mid- to late-dark cycle. Relative white fat-pad mass of Il18 −/− mice was ≈2- to 3-fold greater than that of WT, with gonadal, mesenteric, and inguinal depots growing most. The data suggest that endogenous IL-18 signaling modulates food intake, metabolism, and adiposity during adulthood and might be a central or peripheral pharmacological target for controlling energy homeostasis.

Galanin type 1 receptor knockout mice show altered responses to high-fat diet and glucose challenge. PHYSIOL BEHAV 00(0) 000-000, 200X. Galanin, a brain and pancreatic peptide with three receptor subtypes (GALR1,GALR2,GALR3), is hypothesized to participate in energy homeostasis and glucoregulation. Hypothalamic galanin expression is induced by dietary fat, and intra-hypothalamic galanin administration has orexigenic/anabolic properties. Systemic galanin infusion alters glucoregulation in non-human species, partly through direct actions on pancreatic islets. However, the physiologic significance of endogenous galanin-GALR signaling is unclear. The present studies tested the hypotheses that GALR1 deficiency alters food intake and feed efficiency following switches to high-fat diet and that GALR1 deficiency alters whole-body glucose homeostasis. Adult, male GALR1 knockout (−/−), heterozygote (+/−), and C57BL/6J control (+/+) mice were studied. GALR1 deficiency impaired adaptation to a 3-day high-fat diet challenge, leading to increased food intake, feed efficiency and weight gain. However, during the following 2 weeks, GALR1 knockout mice decreased intake, consuming less daily energy than while maintained on low-fat diet and also than heterozygote littermates. Chow-maintained GALR1 knockout mice showed relative hyperglycemia in fed and d-glucose (i.p. 1.5 g/kg)-challenged states. GALR1 knockout mice showed normal food intake, feed efficiency and weight accrual on low-fat diets, normal fasted glucose levels, and normal glucose sensitivity to porcine insulin (i.p. 1 IU/kg) in vivo. The results support the hypotheses that galanin-GALR1 systems help adapt food intake and metabolism to changes in dietary fat and modulate glucose disposition in mice.

Animal models of alcohol dependence suggest that long-term alterations in brain corticotropin-releasing factor (CRF) systems, key mediators of the behavioral stress response, may be involved in the development and reinstatement of dependence on drugs of abuse. The objective of the present study was to investigate the role of CRF in the regulation of ethanol self-administration and to examine the behavioral stress response during acute withdrawal and protracted abstinence.Male Wistar rats were made dependent on ethanol via chronic exposure to ethanol vapor. Ethanol self-administration and exploratory behavior in the elevated plus maze were measured at 2 hr and 3 to 5 weeks after exposure. The role of CRF in ethanol self-administration was examined via central injection of the CRF receptor antagonist D-Phe-CRF(12-41).Rats showed increased responding for ethanol 2 hr and 3 to 5 weeks after chronic ethanol exposure, which was attenuated by central injection of D-Phe-CRF(12-41). In addition, rats displayed a decrease in open-arm exploration in the elevated plus maze when tested 2 hr and 4 weeks after exposure.These results indicate that chronic ethanol exposure leads to increased ethanol self-administration and decreased open-arm exploration in the elevated plus maze during acute withdrawal and protracted abstinence. Attenuation of ethanol self-administration via central injection of D-Phe-CRF(12-41) implicates CRF as an underlying mechanism regulating long-term motivational effects associated with alcohol dependence.