bluuebunny/crossref_metadata_2025_split huggingface dataset:
Changes in Ventral Tegmental Area Serum‐ and Glucocorticoid‐Inducible Kinase 1 (SGK1) Catalytic Activity and Phosphorylation Alter Drug‐Related Behaviors
Authors: Doyle Marie A. , Bali Vedrana , Kaska Sophia , Cooper Sarah E. , Mazei‐Robison Michelle S. 
Published: November 2023

Drugs of abuse are known to regulate activity of the mesolimbic dopamine system. Specifically, drug‐induced changes in ventral tegmental area (VTA) cellular activity and gene regulation contribute to behavioral outputs associated with addiction. Previous work from my lab has shown that serum‐ and glucocorticoid‐inducible kinase 1 (SGK1) phosphorylation and catalytic activity are increased by chronic, but not acute, administration of cocaine and morphine. However, the functional significance of these changes in drug‐related behaviors remains unclear. Thus, we have created novel viral constructs to overexpress SGK1 mutants in the VTA of adult mice, and I am assessing the impact of altered VTA SGK1 activity on drug reward via cocaine conditioned place preference (CPP) and voluntary morphine intake using a two‐bottle choice task. Intra‐VTA infusion of a catalytically inactive SGK1 mutant (K127Q) significantly decreased morphine intake and there was a similar non‐significant trend for decreased cocaine CPP, suggesting that decreasing VTA SGK1 activity is sufficient to decrease drug reward and intake. I am now extending these studies by investigating the role of SGK1 Ser78 in drug‐related behaviors, as phosphorylation of this site is increased by drugs of abuse. Intra‐VTA infusion SGK1 S78A, a mutant that prevents phosphorylation at S78, decreased morphine intake and preference. Conversely, mice with VTA overexpression of SGK1 S78D, a mutant that mimics phosphorylation, exhibited a trend for increased morphine intake and preference. These data suggest that alteration of VTA SGK S78 phosphorylation is sufficient to modulate drug reward and/or intake. To more fully understand the impact of VTA SGK1 activity on drug behaviors relevant to addiction, I am also now assessing effects on cocaine self‐administration. Additionally, future studies will employ cell type‐specific viral vectors to address if these behavioral changes are driven by SGK1 activity in VTA dopamine or GABA neurons. In summary, our goal is to characterize the role of VTA SGK1 activity in drug‐related behaviors in order to develop novel therapeutic strategies for addiction.Support or Funding InformationT32 NS044928‐13 (NINDS), PhRMA Foundation Research Starter Grant, R01 DA039895‐01A1 (NIDA)
RGS Protein Regulation of Opioid Antinociception
Authors: Tai Sherrica , Senese Nicolas , Ingram Susan , Traynor John R 
Published: November 2023

RGS proteins, or regulator of G protein signaling proteins, are negative modulators of G protein signaling downstream of G protein coupled receptors, including the mu‐opioid receptor (MOPR) and served to switch off signaling. We have previously shown that Gαo is the predominant Gα protein for mediating the effects of MOPR agonists‐mediated antinociception in the mouse. Consequently, male and female 129SvEv mice expressing a knock‐in RGS‐insensitive Gαo (RGSi‐Gαo) protein exhibit an increased antinociceptive response to MOPR agonists in the hot‐plate test. Here we show endogenous opioid peptide signaling is also enhanced in these RGSi‐Gαo mice. The enkephalinase inhibitor RB‐101, a compound that increases the life‐time of the endogenous opioid peptides, administered i.c.v. in wild type mice produced a naloxone‐reversible antinociception in the hot‐plate test, confirming a role for endogenous opioid peptides. This antinociceptive effect was significantly enhanced in the RGSi‐Gαo mice. Naloxone‐reversible antinociception is seen in rodent models following exposure to a stressor. A brief swim stress triggered antinociception in the RGSi‐Gαo mice but not in their wild‐type littermates, confirming RGS proteins are negatively regulating endogenous opioid signaling in the hot‐plate test. In contrast to the hot‐plate test there was a paradoxical inhibition, or no change, of opioid antinociception in the tail withdrawal test. The results show that the opioid peptide system is more active in mice expressing RGSi‐Gαo. However, the role of RGS proteins in negatively modulating MOPR signaling is not reflected as consistent inhibition of behavioral responses across models suggesting RGS proteins may be affecting other systems and/or acting on different intracellular substrates.Support or Funding InformationSupported by DA035316 and DA035316‐03S1.
Modulation of opioid and serotonergic systems by alpha‐terpineol complexed in beta‐cyclodextrin reduces hyperalgesia in a chronic muscle pain model
Authors: Guimarães Adriana Gibara , Oliveira Makson Gleydson Brito , Menezes Paula Passos , de Souza Araújo Adriano Antunes , Silva Juliane Cabral , da Silva Almeida Jackson Roberto Guedes , Santos Márcio Roberto Viana , Júnior Lucindo José Quintans 
Published: November 2023

The aim of this study was to evaluate the effect of α‐terpineol, an alcohol monoterpene found in the essential oil of aromatic species, complexed in β‐cyclodextrin (TP‐βCD) in chronic muscle pain noninflammatory model and its mechanism of action. The model of chronic muscle pain was induced by two injections of pH 4.0 saline (20 μl) into the left gastrocnemius 5 days apart. After confirming hyperalgesia, male mice were treated with α‐terpineol (αTPN 100 mg/kg, p.o.), TP‐βCD (25, 50 or 100 mg/kg; p.o.) or vehicle (saline 0.9%, p.o.) daily for 10 days. The possible involvement of the opioid and serotonergic systems were evaluated using formalin test (1%; 20 μL; i.pl.), which animals were pretreated with αTPN‐βCD (p.o.) or vehicle (p.o.), naloxone (an opioid antagonist, 5 mg/kg; i.p.) or ondansetron (an 5HT3 antagonist, 0.5 mg/kg; i.p.). The experimental protocols were approved for the UFS Ethic Committee (CEPA: 08/11). TP‐βCD reduced significantively (p<0.001) the mechanical hyperalgesia when compared with vehicle. Besides, the complexation with βCD increased the effect time of TP of 3 hrs to 7 hrs. Naloxone and ondansetron were able to reverse this analgesic effect. These results demonstrate that TP‐βCD reduced the hyperalgesia followed by the chronic muscle pain model, probably evoked by the descending inhibitory pain system, specifically by opioid and serotoninergic receptors.Support or Funding InformationFAPITEC/SE, CAPES, CNPq (Brazil).
Characterization of the Ability of Diazepam to Reverse Prescription Opioid Tolerance
Authors: Gonek Maciej , Henderson Graeme , Dewey William L. 
Published: November 2023

We are experiencing an unprecedented opioid overdose epidemic with over 120 people dying every day. Most individuals who become tolerant and dependent on opioids, including the prescription opioids oxycodone and hydrocodone, co‐abuse other substances. The most widely co‐abused drug is ethanol but other CNS depressants such as diazepam and other benzodiazepines are also co‐abused. Several studies suggest that ethanol and benzodiazepines may play a role in as much as 80% of unintentional overdose deaths involving opioids. Postmortem examination of individuals who have died from chronic administration of opioids and ethanol had lower blood levels of opioids than individuals who overdosed on opioids alone. Similar results have not been reported in individuals co‐abusing diazepam. Following the hourly subcutaneous administration of the acute ED80 dose for a total of 7 injections, we observed a significant shift of the dose response curve indicating a 5‐fold tolerance to morphine, a 1.5‐fold tolerance to oxycodone, and a 2‐fold tolerance to hydrocodone in the mouse tail immersion assay. The intraperitoneal administration of 0.5 mg/kg diazepam, a dose that has no observable behavioral effect on its own, 50 minutes before testing fully reversed antinociceptive tolerance to morphine and oxycodone. Hydrocodone tolerance was not fully reversed at doses lower than 2 mg/kg diazepam. There was no potentiation of acute opioid effects. Conversely, opioid tolerance in the stretching assay, a measurement of visceral pain, was not reversed by diazepam. Further research into the differences of opioid tolerance mechanisms can lead to new insights for the development of drugs that decrease the risk of opioid overdosing and the development of drugs to relieve severe pain with limited tolerance.Support or Funding InformationSupported by USPHS Grants RO1 DA036975 and T32DA007027.
Abuse Liability and Anti‐Addiction Potential of the Atypical Mu Opioid Receptor Agonist IBNtxA
Authors: Keck Thomas M , Uddin Md. Main , Babenko Elvira , Wu Chun , Moura‐Letts Gustavo 
Published: November 2023

OBJECTIVEIBNtxA is a μ opioid receptor (MOR) agonist structurally related to the classical MOR antagonist naltrexone. Recent studies suggest IBNtxA preferentially signals through truncated MOR splice variants, producing a unique pharmacological profile resulting in potent analgesia with reduced side effects, including no conditioned place preference (CPP) when tested at a single dose. The purpose of this study is to 1) evaluate a range of IBNtxA doses to more fully assess its abuse liability and 2) determine the effects of IBNtxA on morphine CPP expression and reinstatement of morphine CPP.METHODSIBNtxA was synthesized and compared to morphine in standard CPP expression assays. Following morphine CPP training, IBNtxA was tested for its effects in inducing CPP reinstatement on its own or attenuating morphine‐primed reinstatement. Drug discrimination studies are also underway.RESULTS and CONCLUSIONSIBNtxA represents an intriguing lead compound for preclinical drug development specifically targeting MOR splice variants, potentially creating effective analgesics with reduced side effects. Furthermore, IBNtxA could have use as an adjunct therapy in agonist replacement strategies (e.g., methadone). Current collaborative efforts are aimed at developing novel analogues of IBNtxA for further analysis and understanding ligand‐receptor interactions across MOR splice variants using molecular modeling.Support or Funding InformationRowan University Seed Fund; travel support from Dean of Rowan University College of Science and Mathematics.
Preference for an Opioid/Benzodiazepine Mixture over an Opioid Alone using a Concurrent Choice Procedure in Rhesus Monkeys
Authors: Weed Peter Fletcher , France Charles , Gerak Lisa 
Published: November 2023

Opioid abuse has become an epidemic, leading to a dramatic increase in emergency room visits and overdose deaths. Opioids are frequently coabused with other drugs, and up to 70% of opioid abusers report concurrent benzodiazepine abuse. Coabuse of opioid/benzodiazepine mixtures might be due to benzodiazepines enhancing the positive‐reinforcing effects (increasing potency and/or effectiveness) of opioids. The current study examined whether monkeys choose to self‐administer a mixture of the opioid remifentanil and the benzodiazepine midazolam over remifentanil alone. Three monkeys responded under a concurrent choice procedure for intravenous drug infusions. Initially remifentanil or midazolam was available when the alternative was saline. After dose‐response curves for remifentanil and midazolam were established, monkeys could choose between a dose of remifentanil (0.32 μg/kg/infusion) that did not change during the study and a dose of remifentanil that varied across sessions; for some sessions, midazolam was combined with varying doses of remifentanil. When saline was the alternative, the rate at which monkeys responded for infusions of remifentanil (0.0032 – 0.32 μg/kg/infusion) increased dose‐dependently with all monkeys earning most or all of the available infusions at the largest dose whereas the rate at which monkeys responded for infusions of midazolam increased modestly in only one subject at one dose (10 μg/kg/infusion). When 0.32 μg/kg/infusion of remifentanil was available on one lever and a dose of remifentanil that varied across sessions (0.1 – 1 μg/kg/infusion) was available on the other lever, monkeys chose the larger dose. Combining a small dose of midazolam (3.2 μg/kg/infusion) with 0.32 μg/kg/infusion of remifentanil increased responding for the mixture over 0.32 μg/kg/infusion of remifentanil alone; however, when smaller doses of remifentanil were combined with 3.2 μg/kg/infusion of midazolam, monkeys chose the larger dose of remifentanil alone. In contrast, monkeys chose 0.1 μg/kg/infusion of remifentanil when combined with 10 μg/kg/infusion of midazolam over a larger dose (0.32 μg/kg/infusion) of remifentanil alone. Thus, monkeys prefer some opioid/benzodiazepine mixtures over an opioid alone, suggesting that coabuse of opioid/benzodiazepine mixtures might be due to increased potency (and possibly effectiveness) of the reinforcing effects of opioids.Support or Funding InformationSupported by USPHS grants R21DA039394 and T32DA031115 and the Welch Foundation Grant AQ‐0039.
Alterations in Nucleus Accumbens Dopamine Terminals Following Dopamine Tolerance‐ or Sensitization‐Inducing Cocaine Self‐Administration Protocols
Authors: Mauterer Madelyn I , Albertson Steven E , Jones Sara R 
Published: November 2023

Cocaine has diverse effects on the function of the mesolimbic dopamine system, depending on the schedule and timing of self‐administration behavior. In cocaine self‐administering rats, sensitization as well as tolerance are phenomena that are not only observable behaviorally, but also at the molecular level, specifically at the dopamine transporter (DAT). When rats are allowed long access to cocaine (LgA), in which they can receive an unlimited number of infusions (1.5 mg/kg, i.v.) over the course of six hours per day for 14 days, cocaine intake moderately escalates and the DAT shows robust tolerance to cocaine in vitro. In a short access paradigm (ShA), during which rats have unlimited access to cocaine but only for two hours per day for 14 days, cocaine intake is constant and the DAT is unchanged, showing cocaine responsiveness that is the same as their drug naïve counterparts. However, in contrast, when rats are allowed intermittent access to cocaine (IntA), during which rats are allowed unlimited access to cocaine with no time‐outs for 5 minutes out of every 30 minutes, six hours per day for 14 days, cocaine intake during the 5 min bout is drastically increased and the DAT shows sensitization to the effects of cocaine in vitro. DAT sensitization occurs even though the animals undergoing the IntA paradigm have the same levels of cocaine intake as animals on the ShA paradigm. While the consequences of these self‐administration paradigms have been well characterized at the DAT, because opposite DAT changes occur with two schedules that produce escalation in dopamine‐dependent cocaine self‐administration behaviors, it is clear that there are other neurobiological changes contributing to these behaviors. It is not known how LgA, ShA, and IntA affect other aspects of the dopamine terminal, and so the purpose of this study is to characterize additional regulatory mechanisms on dopamine terminals. Using voltammetry in brain slices, we found that after an LgA protocol, there are no differences in the sensitivity of D2 or D3 dopamine release‐inhibiting autoreceptors compared to control animals. This juxtaposes previous findings from our lab that showed that autoreceptors became subsensitive following a limited access 24 hour paradigm. We are interested in the effects of IntA cocaine self‐administration on autoreceptor function, and the regulation of the strongly inhibitory kappa opioid receptors that are on dopamine terminals. By studying how other dopamine‐regulating processes, other than the DAT, respond to different self‐administrations paradigms, we will be able to gain a better understanding of how cocaine affects the dopamine system as a whole.Support or Funding InformationR01DA014030R01DA011697T32AA007565
Assessment of the Specificity of the Effects of Rimcazole on the Reinforcing Effects of Cocaine Using a Behavioral Economic Approach
Authors: Job Martin O. , Katz Jonathan L. 
Published: November 2023

Previous research has shown that cocaine self‐administration is decreased by rimcazole, a sigma (σ) receptor antagonist that also binds to the dopamine transporter (DAT). However, it is uncertain if those decreases are due to an action of rimcazole on the reinforcing effect of cocaine. One way to assess reinforcing effects is with an analysis of demand curves that show the decreases in consumption of a reinforcer with increasing cost. From the demand curve, the fitted parameters for consumption at no cost (Q0) and the essential value of the reinforcer (EV, a measure derived from the sensitivity to price) can be derived. Because rimcazole has actions at both the DAT and σ receptors, its effects were compared to that of combinations of a σ receptor antagonist (BD 1008) and a standard DAT inhibitor (methylphenidate). Rimcazole (3.2, 10 and 32 mg/kg) or vehicle were administered (i.p.) to male Sprague‐Dawley rats 5 minutes before sessions in which the number of lever presses required per infusion for either of two doses of cocaine (0.1 or 0.32 mg/kg/infusion) or food (three 20 mg pellets) were increased within sessions. The effects of combinations of methylphenidate (1 mg/kg i.p.) and different doses of BD 1008 (0, 3.2, 10 mg/kg) on the demand curve for cocaine (0.1 or 0.32 mg/kg/infusion) or food were determined under similar conditions. Demand curves were fitted to the data using an exponential model (Hursh and Silberberg, Psyc Rev 115: 186, 2008). Rimcazole dose‐dependently decreased both Q0 and EV at doses that had no effect on food‐reinforced responding. The combination of methylphenidate and the highest dose of BD 1008 also decreased Q0, though only at the 0.1 mg/kg/infusion dose of cocaine. In contrast the combination had no effect on the behavioral economic parameters derived from food‐reinforced responding. The present results indicate that rimcazole specifically alters the reinforcing effects of cocaine, but not food. Further, the similarity in effects of the combinations of methylphenidate and BD 1008 to rimcazole suggests that dual inhibition of both the DAT and σ receptors shows specificity in decreasing the reinforcing effects of cocaine and may provide targets for discovery of a combination chemotherapy for cocaine abuse.Support or Funding InformationThis work was supported by NIDA/NIH.
PKCβ Inhibitors Decrease AMPH‐Stimulated Behaviors: More than One Mechanism?
Authors: Altshuler Rachel D , Carpenter Colleen A , Gnegy Margaret E , Jutkiewicz Emily M 
Published: November 2023

Amphetamines (AMPH) elicit their reinforcing effects by increasing dopamine (DA) release from neurons extending from the ventral tegmental area (VTA) to the nucleus accumbens (NAc). Protein kinase Cβ (PKCβ) has been shown to be important for AMPH's mechanism of action, such that inhibition of PKCβ reduces AMPH‐stimulated extracellular DA levels in vitro. While the effects of PKC inhibitors on AMPH‐stimulated DA efflux have been characterized, it is important to understand the effects of PKCβ inhibition in vivo. We previously showed that intraventricular (icv) injections of selective PKCβ inhibitors (ruboxistaurin or enzastaurin) decreases AMPH stimulated locomotor activity, AMPH self‐administration, and AMPH‐stimulated PKC activity but only when given 18 hours before AMPH. The goal of this study was to determine why PKCβ inhibitors given icv require a long pretreatment time before decreasing AMPH behaviors. Our hypothesis is that the site of action of a PKCβ inhibitor, the NAc (site of DA terminals) and VTA (site of DA cell bodies), determines the PKCβ inhibitors' time course. 10 pmols of ruboxistaurin were administered into the NAc or VTA of male Sprague‐Dawley rats 30 mins or 18 hrs prior to evaluating locomotor activity in response to 1 mg/kg AMPH (s.c.). Ruboxistaurin administered directly into the NAc with a 30 min, but not 18 hr, pretreatment decreased AMPH‐stimulated locomotor activity. Conversely, ruboxistaurin given directly into the VTA following an 18 hr, but not 30 min, pretreatment blocked AMPH‐stimulated locomotor activity. Therefore, acute inhibition of PKCβ in the NAc can decrease AMPH‐stimulated activity, but this effect is not observed following icv administration. This may suggest that following icv injections, the concentrations of the PKCβ inhibitor in the NAc are not large enough to affect locomotor activity acutely. The longer pretreatment time necessary for intra‐VTA PKCβ inhibitors to block AMPH‐stimulated behaviors suggests the involvement of a different mechanism that may be less reliant on direct PKC inhibition, such as alterations in transcription or protein synthesis. Overall, we conclude that PKC inhibition decreases AMPH‐stimulated behaviors through a direct and indirect mechanism. Future work will investigate the indirect mechanism, determining if PKCβ inhibitors given directly into the VTA alter PKCβ or DAT levels or function in the NAc.Support or Funding InformationFunded by DA11697 and T32‐GM007767.
Effects of Daily Oral Phendimetrazine on Cocaine‐Food Choice in Rhesus Monkeys
Authors: Stowe Taylor Ashley , Nader Michael , Czoty Paul 
Published: November 2023

Current treatments for cocaine abuse have not been efficacious in the majority of patients. One strategy examined in these studies is for pharmacotherapies to involve combination treatments in which one drug is a long‐acting “agonist” and a second drug administered in combination to perhaps enhance the effects of both drugs. Phendimetrazine is a clinically available anorectic agent that is a prodrug to phenmetrazine, an amphetamine‐like compound, and may have lower abuse liability in comparison to other agonist therapies. Research has shown phendimetrazine reduced cocaine choice by rhesus monkeys when given intravenously by continuous infusion (Banks et al., 2013). The present study examined the effects of oral phendimetrazine on cocaine choice in rhesus monkeys; this treatment route may better represent how the drug would be administered clinically. In this study, rhesus macaques (n=4) were trained to choose between banana‐flavored pellets and cocaine doses (0, 0.003–0.1 mg/kg/injection). Complete cocaine dose‐response curves were determined each session and cocaine choice increased as a function of cocaine dose. Once the monkeys' responding was stable, they were given phendimetrazine orally twice a day and tested once a week on the choice procedure. The dose of phendimetrazine always started at 4.0 mg/kg and increased depending on whether the monkey's choice changed. If the phendimetrazine dose lowered cocaine choice, the monkey would continue on this dose for another week. However, if cocaine choice remained at baseline or increased the dose of phendimetrazine would increase. Blood samples were taken weekly to ensure that the monkeys were taking the oral phendimetrazine. In preliminary findings, oral (6.0 mg/kg) phendimetrazine initially decreased cocaine choice in two monkeys, but tolerance developed to this effect. At present, it is unclear why these results vary from Banks et al. (2013), but could be due to a number of reasons such as the route and duration of administration of phendimetrazine or the availability of cocaine in which monkeys in the present study were tested weekly rather than daily in the Banks et al. study. Measures of plasma phendimetrazine and phenmetrazine will provide important information. Future directions include examining these methodological issues and to add a second drug to extend the initial effects of phendimetrazine in lowering cocaine choice.Support or Funding InformationDA06634