Papers by Marsida Kallupi
Nature Neuroscience, Oct 4, 2023
The amygdala processes positive and negative valence and contributes to addiction, but the cell-t... more The amygdala processes positive and negative valence and contributes to addiction, but the cell-type-specific gene regulatory programs involved are unknown. We generated an atlas of single-nucleus gene expression and chromatin accessibility in the amygdala of outbred rats with high and low cocaine addiction-like behaviors following prolonged abstinence. Differentially expressed genes between the high and low groups were enriched for energy metabolism across cell types. Rats with high addiction index (AI) showed increased relapse-like behaviors and GABAergic transmission in the amygdala. Both phenotypes were reversed b y p harm ac ol ogical inhibition of the glyoxalase 1 enzyme, which metabolizes methylglyoxal-a GABA A receptor agonist produced by glycolysis. Differences in chromatin accessibility between high and low AI rats implicated pioneer transcription factors in the basic helix-loop-helix, FOX, SOX and activator protein 1 families. We observed opposite regulation of chromatin accessibility across many cell types. Most notably, excitatory neurons had greater accessibility in high AI rats and inhibitory neurons had greater accessibility in low AI rats. The amygdala regulates numerous behaviors related to emotions, motivation and memory 1 and is implicated in various neuropsychiatric disorders including addiction 2,3. Repeated drug use engages the amygdala to form drug-associated memories and reinforces drug-seeking behavior 4. In addition, during withdrawal from addictive drugs, the amygdala mediates negative emotional states, such as anxiety, fear and irritability 4. Avoidance of these aversive emotions enhances the incentive value of the drug, leading to sustained drug-seeking behaviors
Chemical Communications, 2018
A nicotine-degrading enzyme termed NicA2 was altered (NicA2-J1) through fusion of an albumin bind... more A nicotine-degrading enzyme termed NicA2 was altered (NicA2-J1) through fusion of an albumin binding domain to increase its half-life. Examination of NicA2-J1 in vivo demonstrated a complete blockade of brain nicotine access, which in turn blunted nicotine's psychoactive effects. These data further support development of pharmacokinetic nicotine cessation therapeutics. Smoking is the leading cause of preventable illness in the world today with tobacco use killing 6 million people per year. 1 Effective cessation aids are essential to assist in reducing the prevalence of cigarette smoking and related illness. 2 Among the pharmacological treatments that are approved for nicotine cessation, Varenicline has shown the most success, however, such treatment only increases the odds of abstinence at 6 months approximately 3fold compared to placebo. 4 Due to a low success rate with "pharmacodynamic" treatment strategies, the past decade has seen what has been termed a "pharmacokinetic" approach emerge for treating drug addiction. Of these, immunopharmacotherapy is a methodology wherein vaccines are crafted to stimulate the production of antibodies specific to the drug of interest. 5 Many drugs of abuse have been targeted including, cocaine, methamphetamine, heroin and nicotine. 6 The overall premise of immunopharmacotherapy is that the composite size of antibody-drug union is too large to cross the blood-brain barrier, reducing the concentration/rate of drug entering the brain, ultimately blunting the reinforcing and addictive effects of the drug. Unfortunately, vaccine strategies for nicotine addiction that have been tested in clinical trials have failed to achieve their primary end-point of increased cessation rates compared to
Deep brain stimulation of the nucleus accumbens shell does not decrease cocaine selfadministratio... more Deep brain stimulation of the nucleus accumbens shell does not decrease cocaine selfadministration in cocaine-dependent rats but increases GluR1/GluA1 in the central nucleus of the amygdala
Psychopharmacology, Mar 24, 2017
Rationale-A major issue in the addiction field is the limited number of animal models of the volu... more Rationale-A major issue in the addiction field is the limited number of animal models of the voluntary induction and maintenance of alcohol dependence in outbred rats. Objectives-To address this issue, we developed a novel apparatus that vaporizes alcohol for 2-10 min after an active nosepoke response. Methods-Male Wistar rats were allowed to self-administer alcohol vapor for 8 h/day every other day for 24 sessions (escalated) or eight sessions (non-escalated). Escalated and non-escalated rats were then tested for progressive ratio responding. Anxiety-like behavior, somatic signs of withdrawal, and hyperalgesia were assessed during acute withdrawal. Results-The results showed that rats exhibited excellent discrimination between the active and inactive operanda (>85%), and the escalated rats quickly increased their blood alcohol levels from ~50 to >200 mg% in ~6 weeks. Compared with non-escalated rats, escalated rats exhibited severe addiction-like behavior, including somatic signs of withdrawal, anxiety-like behavior, hyperalgesia, and higher responding on a progressive ratio schedule of reinforcement. Conclusions-These results demonstrate that outbred rats will voluntarily self-administer alcohol vapor to the point of dependence without the use of forced alcohol administration, sweeteners, food/water restriction, operant pretraining, or behavioral/genetic selection. This novel animal model may be particularly useful for medication development to help unveil the neuronal circuitry that underlies the voluntary induction of alcohol addiction and identify novel molecular targets that are specifically recruited after the voluntary induction and maintenance of alcohol dependence.
Frontiers in Pharmacology, Jun 15, 2023
bioRxiv (Cold Spring Harbor Laboratory), May 12, 2022
A major limitation of the most widely used current animal models of alcohol dependence is that th... more A major limitation of the most widely used current animal models of alcohol dependence is that they use forced exposure to ethanol including ethanol-containing liquid diet and chronic intermittent ethanol (CIE) vapor to produce clinically relevant blood alcohol levels (BAL) and addiction-like behaviors. We recently developed a novel animal model of voluntary induction of alcohol dependence using ethanol vapor self-administration (EVSA). In this model, naive outbred rats given intermittent access to alcohol vapor self-administration exhibit BAL in the 150-300 mg% range and develop somatic signs of withdrawal during acute abstinence. However, it is unknown whether EVSA leads to an escalation of alcohol drinking per se, and whether such escalation is associated with neuroadaptations in brain regions related to stress, reward, and habit. To address these issues, we compared the levels of alcohol drinking during withdrawal between rats passively exposed to alcohol (CIE) or voluntarily exposed to EVSA and measured the number of Fos+ neurons during acute withdrawal (16 h) in the central nucleus of the amygdala (CeA), dorsomedial striatum (DMS), dorsolateral striatum (DLS), nucleus accumbens core (Nacc), periaqueducal grey area (PAG), lateral Habenula (HbL), and the paraventricular nucleus of the thalamus (PVT). The rats were first trained to orally self-administer alcohol in standard operant chambers and then divided in 4 groups (CIE, CI-Air, EVSA and Air-SA) and exposed to intermittent ethanol vapor (passive or active) or intermittent air (passive or active) for 8 h/day, 3 days a week. CIE and EVSA rats exhibited similar BAL (150-300 mg% range) and similar escalation of alcohol drinking during withdrawal, while no changes in terms of drinking were observed in the air exposed rats. CIE and EVSA also increased the motivation for alcohol compared to their respective air control groups under a progressive ratio schedule of reinforcement. Acute withdrawal from EVSA and CIE recruited a similar number of Fos+ neurons in the CeA, however, acute withdrawal from EVSA recruited a higher number of Fos+ neurons in every other brain region analyzed compared to acute withdrawal from CIE. Moreover, acute withdrawal from EVSA specifically recruited the DMS and PVT, a pattern not observed in CIE rats. In summary, these results demonstrate that EVSA produces similar escalation of alcohol drinking, motivation to drink, and blood-alcohol levels than the CIE model, while letting animals voluntary initiate alcohol exposure and maintain alcohol dependence. Moreover, while the behavioral measures of alcohol dependence between the voluntary (EVSA) and passive (CIE) .
Addiction Biology, Jun 21, 2017
Buprenorphine's clinical use is approved for the treatment of heroin addiction; however, evidence... more Buprenorphine's clinical use is approved for the treatment of heroin addiction; however, evidence supporting its efficacy in cocaine abuse also exists. While for heroin it has been demonstrated that the effect of buprenorphine is mediated by its ability to activate μ-opioid peptide receptor (MOP) receptors, the mechanism through which it attenuates cocaine intake remains elusive. We explored this mechanism using operant models where rodents were trained to chronically self-administer cocaine for 2 hours daily. Buprenorphine (0.3, 1.0 and 3.0 mg/kg) given intraperitoneally 90 minutes before access to cocaine significantly and dose dependently reduced its intake. Pretreatment with naltrexone or with the selective nociceptin/orphanin FQ peptide (NOP) antagonist SB-612111 did not prevent buprenorphine-induced reduction of cocaine intake. However, when naltrexone and SB-612111 were combined, the effect of buprenorphine on cocaine was completely prevented. To confirm that co-activation of MOP and NOP receptors is the underlying mechanism through which buprenorphine reduces cocaine intake, three compounds, namely, AT-034, AT-201 and AT-202, with a range of affinity and intrinsic activity profiles for MOP and NOP receptors, but weak ability for kappa-opioid peptide receptor (KOP) transmission, were tested. Consistent with our hypothesis based on buprenorphine's effects, results demonstrated that AT-034 and AT-201, which co-activate MOP and NOP receptors, reduced cocaine self-administration like buprenorphine. AT-202, which selectively stimulates NOP receptors, was not effective. Together, these data demonstrate that for buprenorphine, co-activation of MOP and NOP receptors is essential to reduce cocaine consumption. These results open new vistas on the treatment of cocaine addiction by developing compounds with mixed MOP/NOP agonist properties.
Psychopharmacology, Jan 21, 2018
RationaleThe ability of nicotine to suppress body weight is cited as a factor impacting smoking i... more RationaleThe ability of nicotine to suppress body weight is cited as a factor impacting smoking initiation and the failure to quit. Self-administered nicotine in male rats suppresses weight independent of food intake, suggesting that nicotine increases energy expenditure.ObjectiveThe current experiment evaluated the impact of self-administered nicotine on metabolism in rats using indirect calorimetry and body composition analysis.MethodsAdult male rats with ad libitum access to powdered standard rodent chow self-administered intravenous infusions of nicotine (60 μg/kg/infusion or saline control) in daily 1-h sessions in the last hour of the light cycle. Indirect calorimetry measured respiratory exchange ratio (RER), energy expenditure, motor activity, and food and water consumption for 22.5 h between select self-administration sessions.ResultsSelf-administered nicotine suppressed weight gain and reduced the percent of body fat without altering the percent of lean mass, as measured by Echo MRI. Nicotine reduced RER, indicating increased fat utilization; this effect was observed prior to weight suppression. Moreover, nicotine intake did not affect motor activity or energy expenditure. Daily food intake was not altered by nicotine self-administration; however, a trend in suppression of meal size, a transient suppression of water intake, and an increase in meal frequency was observed.ConclusionThese data provide evidence that self-administered nicotine suppresses body weight via increased fat metabolism, independent of significant changes in feeding, activity, or energy expenditure.
bioRxiv (Cold Spring Harbor Laboratory), Sep 12, 2022
The amygdala contributes to negative emotional states associated with relapse to drug seeking, bu... more The amygdala contributes to negative emotional states associated with relapse to drug seeking, but the cell type-specific gene regulatory programs that are involved in addiction are unknown. Here we generate an atlas of single nucleus gene expression and chromatin accessibility in the amygdala of outbred rats with low and high cocaine addiction-like behaviors following a prolonged period of abstinence. Between rats with different addiction indexes, there are thousands of cell type-specific differentially expressed genes and these are enriched for molecular pathways including GABAergic synapse in astrocytes, excitatory, and somatostatin neurons. We find that rats with higher addiction severity have excessive GABAergic inhibition in the amygdala, and that hyperpolarizing GABAergic transmission and relapse-like behavior are reversed by pharmacological manipulation of the metabolite methylglyoxal, a GABAA receptor agonist. By analyzing chromatin accessibility, we identify thousands of cell type-specific chromatin sites and transcription factor (TF) motifs where accessibility is associated with addiction-like behaviors, most notably at motifs for pioneer TFs in the FOX, SOX, and helixloop-helix families.
Frontiers in Behavioral Neuroscience, Jun 28, 2022
The debate about electronic cigarettes has divided healthcare professionals, policymakers, and co... more The debate about electronic cigarettes has divided healthcare professionals, policymakers, and communities. Central points of disagreement are whether vaping electronic cigarettes are addictive and whether they produce major pulmonary complications. We developed a novel model of nicotine vapor self-administration in rats and found that rats voluntarily exposed themselves to nicotine vapor to the point of reaching blood nicotine levels that are similar to humans, exhibiting both addiction-like behaviors and cardiopulmonary abnormalities. The smoking cessation drug varenicline decreased electronic cigarette selfadministration. These findings confirm the addictive properties and harmful effects of nicotine vapor and identify a potential medication for the treatment of electronic cigarette addiction.
Proceedings of the National Academy of Sciences of the United States of America, Jan 13, 2020
Approximately 25% of patients who are prescribed opioids for chronic pain misuse them, and 5-10% ... more Approximately 25% of patients who are prescribed opioids for chronic pain misuse them, and 5-10% develop an opioid use disorder. Although the neurobiological target of opioids is well known, the molecular mechanisms that are responsible for the development of addiction-like behaviors in some but not all individuals are poorly known. To address this issue, we used a unique outbred rat population (Heterogeneous Stock) that better models the behavioral and genetic diversity that is found in humans. We characterized individual differences in addiction-like behaviors using an Addiction Index that incorporates the key criteria of opioid use disorder: escalated intake, highly motivated responding, and hyperalgesia. Using in vitro electrophysiological recordings in the central nucleus of the amygdala (CeA), we found that rats with high addiction-like behaviors (HA) exhibited a significant increase in g-aminobutyric acid (GABA) transmission compared with rats with low addiction-like behaviors (LA) and naive rats. The superfusion of CeA slices with nociceptin/orphanin FQ peptide (N/OFQ; 500 nM), an endogenous opioid-like peptide, normalized GABA transmission in HA rats. Intra-CeA levels of N/OFQ were lower in HA rats than in LA rats. Intra-CeA infusions of N/OFQ (1 µg/site) reversed the escalation of oxycodone selfadministration in HA rats but not in LA rats. These results demonstrate that the downregulation of N/OFQ levels in the CeA may be responsible for hyper-GABAergic tone in the CeA that is observed in individuals who develop addiction-like behaviors. Based on these results, we hypothesize that small molecules that target the N/OFQ system might be useful for the treatment of opioid use disorder. Significance statement More than 2 million individuals in the United States currently have a substance use disorder that is related to prescription opioid pain relievers. We identified individual differences in oxycodone addiction-like behaviors in outbred heterogenous stock rats with high (HA) and low (LA) addiction like-behaviors. We found that the downregulation of nociceptin levels in the central nucleus of the amygdala (CeA) may be responsible for hyper-g-aminobutyric acid (GABA)ergic tone in the CeA that is observed in individuals who develop addiction-like behaviors. The development of small molecules that target the nociceptin system may have therapeutic efficacy for the treatment of opioid use disorder.
European Neuropsychopharmacology, Nov 1, 2019
Electronic cigarette use is particularly prevalent in adolescents, but the effects of secondhand ... more Electronic cigarette use is particularly prevalent in adolescents, but the effects of secondhand exposure to nicotine vapor in adolescents on the propensity to develop nicotine dependence and increase nicotine selfadministration in adulthood are poorly known. The present study explored the effects of nicotine vapor exposure on withdrawal-like states (hyperalgesia, spontaneous withdrawal signs, and locomotor activity) in adolescent rats and the vulnerability to acquire intravenous nicotine selfadministration in adulthood. Adolescent (postnatal day 38) rats were exposed to intermittent nicotine vapor (14 h/day) for 7 consecutive days in a range of doses (0, 0.4, and 7 mg/m 3). The rats were tested for somatic, emotional, and motivational withdrawal symptoms. When the animals reached adulthood, they were allowed to self-administer nicotine (0.03 mg/kg/0.1 ml) intravenously in operant chambers for 1 h/day for 12 consecutive days. Rats that were exposed to nicotine vapor presented moderate to severe signs of spontaneous withdrawal after the cessation of nicotine vapor. No effect on anxiety-like behavior was observed. Rats that were exposed to high levels of nicotine vapor in adolescence had lower pain thresholds and exhibited faster and higher acquisition of nicotine selfadministration in adulthood. Chronic exposure to nicotine vapor in adolescent rats produced a withdrawal-like state and facilitated the acquisition of intravenous nicotine self-administration in adulthood. These 3 results suggest that exposure of adolescents to nicotine vapor may confer higher risk of developing nicotine dependence when they become adults.
Biomedicines
Cocaine administration alters the microRNA (miRNA) landscape in the cortico-accumbal pathway. The... more Cocaine administration alters the microRNA (miRNA) landscape in the cortico-accumbal pathway. These changes in miRNA can play a major role in the posttranscriptional regulation of gene expression during withdrawal. This study aimed to investigate the changes in microRNA expression in the cortico-accumbal pathway during acute withdrawal and protracted abstinence following escalated cocaine intake. Small RNA sequencing (sRNA-seq) was used to profile miRNA transcriptomic changes in the cortico-accumbal pathway [infralimbic- and prelimbic-prefrontal cortex (IL and PL) and nucleus accumbens (NAc)] of rats with extended access to cocaine self-administration followed by an 18-h withdrawal or a 4-week abstinence. An 18-h withdrawal led to differential expression (fold-change > 1.5 and p < 0.05) of 21 miRNAs in the IL, 18 miRNAs in the PL, and two miRNAs in the NAc. The mRNAs potentially targeted by these miRNAs were enriched in the following pathways: gap junctions, neurotrophin signa...
Family and twin studies demonstrate that genetic factors determine 20-60% of the vulnerability to... more 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 ...
RationaleCurrent medications for opioid use disorder include buprenorphine, methadone, and naltre... more 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 na...
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Papers by Marsida Kallupi