A subset of rats that self-administer 3,4-methylenedioxypyrovalerone (MDPV) develop unusually high levels of drug taking. A history of responding maintained by cocaine, but not food, prevents the ...development of this high-responder phenotype; however, it is unclear how histories of noncontingent cocaine exposure or self-administering drugs from other pharmacological classes would affect its development. In the current studies, 5 groups of male Sprague-Dawley rats were used to determine whether histories of responding maintained by drugs from different pharmacological classes (e.g., MDPV, cocaine, fentanyl, nicotine, or ketamine) would differentially impact the development of the high-responder phenotype when MDPV was available for self-administration. Two additional groups were used to determine whether noncontingent exposure to cocaine would prevent the development of the high-responder phenotype when MDPV was available for self-administration, and whether noncontingent exposure to MDPV would facilitate the development of the high-responder phenotype when cocaine was available for self-administration. Consistent with previous reports, a history of response-contingent cocaine, and to a lesser extent noncontingent cocaine, prevented the MDPV high-responder phenotype; however, when responding was initially maintained by fentanyl, nicotine, or ketamine, the MDPV high-responder phenotype developed in ∼45% of rats. By manipulating behavioral and pharmacological histories prior to evaluating MDPV self-administration, the current studies provide additional evidence that a history of response-contingent (or noncontingent) cocaine can prevent the transition from well regulated to aberrant drug-taking when responding is maintained by MDPV. Although the mechanism(s) that underlies this novel high-responder phenotype are unknown, elucidation may provide insight into individual differences relating to substance use disorder. SIGNIFICANCE STATEMENT: A subset of outbred Sprague-Dawley rats self-administer high levels of the synthetic cathinone 3,4-methylenedioxypyrovalerone (MDPV). Understanding the behavioral and/or pharmacological factors that can prevent the development of dysregulated MDPV self-administration may provide insight into individual differences in vulnerability to develop a substance use disorder.
A subset of rats that self‐administer synthetic cathinones, such as 3,4‐methylenedioxypyrovalerone (MDPV), develop high levels of drug intake and patterns of responding similar to the compulsive, ...binge‐like patterns of cathinone (e.g., “bath salts”) use reported in humans. Though high‐responder rats exhibit some behaviors thought to be related to substance use disorder, the effects of punished responding in these rats were unknown. These studies evaluated whether (1) high‐responder rats were less sensitive to footshock‐punished responding than low‐responder rats using both unsignaled and signaled footshock procedures; (2) whether sensitivity to footshock was dependent on the self‐administered dose of MDPV. Inhibition curves for unsignaled footshock (0.05‐0.9 mA, increasing across sessions) were evaluated in forty adult Sprague Dawley rats self‐administering 0.01, 0.032, and 0.1 mg/kg/infusion MDPV under a FR5 schedule of reinforcement; footshocks were paired with ~50% of drug infusions. Rats were then trained on a signaled footshock procedure, in which a change in stimulus conditions signaled that the next infusion would be paired with a footshock (intensities individualized to each rat’s IC50). Rats could avoid this footshock by withholding responding for 30‐sec. After rats learned the signaled shock procedure, inhibition curves were generated using a range of footshock intensities (0.05‐0.9 mA). High‐ and low‐responder rats were similarly sensitive to unsignaled punishment by footshock (mean IC50s‐ high‐responders: 0.30mA; low‐responders: 0.36mA). However, high‐responder rats (mean: 45mA) received significantly more total current than low‐responder rats (mean: 18mA). Compared to low‐responder rats, high‐responder rats respond more in the presence of the signal indicating impending shock and avoid a smaller proportion of shocks. This suggests high‐responder rats may be less able to adapt their behavior in response to a stimulus associated with punishment. These studies suggest that the high levels of drug‐taking observed in the high‐responder rats reflects a compulsive‐like pattern of responding, which may be related to continued use despite adverse consequence, a DSM symptom of substance use disorder.
Over the past two decades, the escalating prescription of opioid medications for pain management has culminated in a widespread opioid epidemic, significantly impacting public health, social ...dynamics, and economic stability. The urgent need for improved treatments for opioid addiction necessitates a deeper understanding of its biological underpinnings, with genetic variations playing a crucial role in individual susceptibility to opioid use disorder (OUD) and influencing clinical practices.
In this study, we leverage the genetic diversity of four rat strains (ACI/N, BN/NHsd, WKY/N, and F344/N) to examine the contribution of genetic factors to oxycodone metabolism and addiction-like behaviors. We used the extended access to intravenous oxycodone self-administration procedure (12 h/day, 0.15 mg/kg/injection) to comprehensively characterize oxycodone-related behaviors and pharmacokinetics. We measured escalation of oxycodone self-administration, motivation for drug consumption, tolerance to the analgesic effects of oxycodone, withdrawal-induced hyperalgesia, and oxycodone-induced respiratory depression. Additionally, we examined oxycodone-seeking behavior after four weeks of withdrawal by reintroducing the animals to environmental and cue stimuli previously associated with oxycodone self-administration.
The findings revealed notable strain differences in several behavioral measures, including oxycodone metabolism. Intriguingly, BN/NHsd and WKY/N strains exhibited similar drug intake and escalation patterns but displayed significant disparities in oxycodone and oxymorphone metabolism. Minimal sex differences were observed within strains, primarily relating to oxycodone metabolism.
In conclusion, this study identifies strain differences in the behavioral responses and pharmacokinetics associated with oxycodone self-administration in rats, providing a robust foundation for identifying genetic and molecular variants associated with various facets of the opioid addiction process.
•Strain differences impact oxycodone metabolism and behavior, including cue seeking.•Sex influences oxycodone pharmacokinetics.•There are complex relationships between different oxycodone-related behaviors.•Development of tolerance can differ across behavioral assays.
Despite decades of research, there are no medications approved by the United States Food and Drug Administration to treat stimulant use disorders. Self-administration procedures are widely used to ...screen candidate medications for stimulant use disorder, although preclinical reductions in stimulant self-administration have not translated to meaningful reductions in stimulant use in humans. One possible reason for this discordance is that most preclinical studies evaluate candidate medications under conditions that promote predictable, and well-regulated patterns of drug-taking rather than the dysregulated and/or compulsive patterns of drug-taking characteristic of a stimulant use disorder. A subset of rats ("high-responders") that self-administer 3,4-methelyendioxypyrovalerone (MDPV), a monoamine uptake inhibitor, develop high levels of dysregulated drug-taking consistent with behaviors related to stimulant use disorders. Because MDPV acts on dopamine, serotonin (5-HT), and sigma receptor systems, the current studies compared the potency and effectiveness of a dopamine D
receptor partial agonist (VK4-40) or antagonist (VK4-116), a sigma receptor antagonist (BD1063), a dopamine D
/D
/sigma receptor antagonist (haloperidol), and a 5-HT
receptor agonist (CP-809,101) to reduce MDPV (0.0032-0.1 mg/kg/infusion) self-administration in high- and low-responding rats as well as rats self-administering cocaine (0.032-1 mg/kg/infusion). VK4-40, VK4-116, haloperidol, and CP-809,101 were equipotent and effective at reducing drug-taking in all three groups of rats, including the high-responders; however, VK4-116 and CP-809,101 were less potent at reducing drug-taking in female compared with male rats. Together, these studies suggest that drugs targeting dopamine D
or 5-HT
receptors can effectively reduce dysregulated patterns of stimulant use, highlighting their potential utility for treating stimulant use disorders. SIGNIFICANCE STATEMENT: There are no United States Food and Drug Administration-approved treatments for stimulant use disorder, perhaps in part because candidate medications are most often evaluated in preclinical models using male subjects with well-regulated drug-taking. In an attempt to better model aberrant drug taking, this study found compounds acting at dopamine D
or 5-HT
receptors can attenuate drug-taking in male and female rats that self-administered two different stimulants and exhibited either a high or low substance use disorder-like phenotype.
Rationale
A subset of male rats that self-administer 3,4-methylenedioxypyrovalerone (MDPV) have unusually high levels of drug intake; however, factor(s) that influence this behavior (e.g., ...reinforcement history and sex) are unknown.
Objectives
Characterize the reinforcing potency and effectiveness of MDPV in female rats to determine whether (1) a subset of females also develop high levels of MDPV self-administration (i.e., a high-responder phenotype) and (2) the degree to which the high-responder phenotype is influenced by various reinforcement histories (i.e., responding for cocaine or food).
Methods
Female Sprague Dawley rats initially responded for MDPV (0.032 mg/kg/infusion), cocaine (0.32 mg/kg/infusion), or food (45-mg grain pellet) under fixed ratio (FR) 1 and FR5 schedules of reinforcement. After 20 sessions, the cocaine- and food-history rats responded for MDPV for 20 additional sessions. Dose-response curves for MDPV were generated under FR5 and progressive ratio (PR) schedules of reinforcement.
Results
A subset of rats responding for MDPV developed high levels of MDPV intake. A history of responding for cocaine, but not food, inhibited the development of high levels of MDPV intake. Large individual differences were observed in the level of self-administration when MDPV was available under an FR5, but not PR, schedule of reinforcement.
Conclusions
MDPV functions as a powerful reinforcer in female rats, as has been previously reported in male rats. The substantial variability in MDPV self-administration between subjects may be related to individual differences in human drug-taking behavior.
Nkx2.2 is a homeodomain transcription factor that is critical for pancreatic endocrine cell specification and differentiation in the developing mouse embryo. The purpose of this study was to ...determine whether Nkx2.2 is also required for the maintenance and function of the mature beta-cell in the postnatal islet. We have demonstrated previously that a repressor derivative of Nkx2.2 can functionally substitute for endogenous Nkx2.2 to fully restore alpha- and immature beta-cells in the embryonic islet; however, Nkx2.2 activator functions appear to be required to form a functional beta-cell. In this study, we have created transgenic mouse lines to express the Nkx2.2-repressor derivative in the mature beta-cell in the presence of endogenous Nkx2.2. The transgenic mice were assessed for beta-cell function, overall islet structure, and expression of beta-cell-specific markers. Using this transgenic approach, we have determined that the Nkx2.2-repressor derivative disrupts endogenous Nkx2.2 expression in adult mice and causes downregulation of the mature beta-cell factors, MafA and Glut2. Consistently, the Nkx2.2-repressor mice display reduced insulin gene expression and pancreatic insulin content and impaired insulin secretion. At weaning, the male Nkx2.2-repressor mice are overtly diabetic and all Nkx2.2-repressor transgenic mice exhibit glucose intolerance. Furthermore, the loss of beta-cell function in the Nkx2.2-repressor transgenic mice is associated with disrupted islet architecture. These studies indicate a previously undiscovered role for Nkx2.2 in the maintenance of mature beta-cell function and the formation of normal islet structure.
Many drugs of abuse are mixed with other psychoactive substances (e.g., caffeine) prior to their sale or use. Synthetic cathinones (e.g., 3,4‐methylenedioxypyrovalerone MDPV) are commonly mixed with ...caffeine or other cathinones (e.g., 3,4‐methylenedioxy‐N‐methylcathinone methylone), and these “bath salts” mixtures (e.g., MDPV + caffeine) can exhibit supra‐additive interactions with regard to their reinforcing and discriminative stimulus properties. However, little is known about relapse‐related effects of drug mixtures. In these studies, male Sprague–Dawley rats self‐administered 0.032 mg/kg/inf MDPV or a mixture of MDPV + caffeine (0.029 + 0.66 mg/kg/inf, respectively) and then underwent multiple rounds of extinction and reinstatement testing to evaluate the influence of reinforcement history and drug‐associated stimuli on the effectiveness of saline (drug‐paired stimuli alone), MDPV (0.032–1.0 mg/kg), caffeine (1.0–32 mg/kg), and mixtures of MDPV:caffeine (in 3:1, 1:1, and 1:3 ratios, relative to each drug's ED50) to reinstate responding. Dose‐addition analyses were used to determine the nature of the drug–drug interaction for each mixture. MDPV and caffeine dose‐dependently reinstated responding and were equally effective, regardless of reinforcement history. Most fixed ratio mixtures of MDPV + caffeine exhibited supra‐additive interactions, reinstating responding to levels greater than was observed with caffeine and/or MDPV alone. Drug‐associated stimuli also played a key role in reinstating responding, especially for caffeine. Together, these results demonstrate that the composition of drug mixtures can impact relapse‐related effects of drug mixtures, and “bath salts” mixtures (MDPV + caffeine) may be more effective at promoting relapse‐related behaviors than the constituents alone. Further research is needed to determine how other polysubstance reinforcement histories can impact relapse‐related behaviors.
MDPV and caffeine were equally effective at reinstating responding in rats that previously self‐administered either the synthetic cathinone MDPV or a mixture of MDPV + caffeine. Mixtures of MDPV:caffeine (in 3:1, 1:1, and 1:3 ratios) were supra‐additive with respect to effectiveness in their ability to reinstate responding. These findings demonstrate that the composition of drug mixtures can impact relapse‐related effects, and “bath salts” mixtures (MDPV + caffeine) may be more effective at promoting relapse‐related behaviors than the constituents alone.
Children's Health Ireland (CHI), who govern and operate acute paediatric services for the greater Dublin area, are also the client for the new children's hospital project which will be Ireland's ...first fully digital hospital. Design, development and implementation of digital solutions has been prioritised by the National Strategy for Children's Nursing to transform and accelerate nurse-led services.
The aim of this phase of a larger study was to explore the perspectives and opinions of key stakeholders on the requirements, benefits, and challenges for a bespoke patient portal, with a specific focus on the ANP-led Neurosurgical Service and children and young people with hydrocephalus.
Interviews and focus groups were held online, and data were recorded and transcribed verbatim. Twenty-three participants across eight sites were interviewed including parents, healthcare professionals, experts and management/administrators. Data were analysed using Braun and Clarke's (2006) framework.
Four key findings and considerations were identified in relation to patient portals in general and their interoperability with Electronic Health Records, as well as a bespoke patient portal for children and young people with hydrocephalus
The availability of a patient portal for children and young people with hydrocephalus would be hugely advantageous to their parents, the ANP led nursing service, and healthcare professionals in both the neurosurgical service at CHI and at regional healthcare organisations as well as for administration, research, and reports. More timely access to health data as well as a consistent log of information and communications between patients and healthcare professionals, would be more efficient and effective than current practices.The augmented ANP-led Neurosurgical Nursing Service at CHI will act as a pilot project from which other nurse-led digital patient services can learn from.
This study was conducted between September 2022 and June 2023. It was registered in Trinity College Dublin, Ireland
A study exploring requirements, benefits, & challenges for an interoperable patient portal in an ANP led Service for children with hydrocephalus
During 2016-2017, we tested asymptomatic men who have sex with men (MSM) in Melbourne, Australia, for Mycoplasma genitalium and macrolide resistance mutations in urine and anorectal swab specimens by ...using PCR. We compared M. genitalium detection rates for those asymptomatic men to those for MSM with proctitis and nongonococcal urethritis (NGU) over the same period. Of 1,001 asymptomatic MSM, 95 had M. genitalium; 84.2% were macrolide resistant, and 17% were co-infected with Neisseria gonorrhoeae or Chlamydia trachomatis. Rectal positivity for M. genitalium was 7.0% and urine positivity was 2.7%. M. genitalium was not more commonly detected in the rectums of MSM (n = 355, 5.6%) with symptoms of proctitis over the same period but was more commonly detected in MSM (n = 1,019, 8.1%) with NGU. M. genitalium is common and predominantly macrolide-resistant in asymptomatic MSM. M. genitalium is not associated with proctitis in this population.
PDF
