Role of dorsomedial striatum neuronal ensembles in incubation of methamphetamine craving after voluntary abstinence

Abstract We recently developed a rat model of incubation of methamphetamine craving after choice-based voluntary abstinence. Here, we studied the role of dorsolateral striatum (DLS) and dorsomedial striatum (DMS) in this incubation. We trained rats to self-administer palatable food pellets (6 d, 6 h/d) and methamphetamine (12 d, 6 h/d). We then assessed relapse to methamphetamine seeking under extinction conditions after 1 and 21 abstinence days. Between tests, the rats underwent voluntary abstinence (using a discrete choice procedure between methamphetamine and food; 20 trials/d) for 19 d. We used in situ hybridization to measure the colabeling of the activity marker Fos with Drd1 and Drd2 in DMS and DLS after the tests. Based on the in situ hybridization colabeling results, we tested the causal role of DMS D1 and D2 family receptors, and DMS neuronal ensembles in "incubated" methamphetamine seeking, using selective dopamine receptor antagonists (SCH39166 or raclopride) and the Daun02 chemogenetic inactivation procedure, respectively. Methamphetamine seeking was higher after 21 d of voluntary abstinence than after 1 d (incubation of methamphetamine craving). The incubated response was associated with increased Fos expression in DMS but not in DLS; Fos was colabeled with both Drd1 and Drd2 DMS injections of SCH39166 or raclopride selectively decreased methamphetamine seeking after 21 abstinence days. In Fos-lacZ transgenic rats, selective inactivation of relapse test-activated Fos neurons in DMS on abstinence day 18 decreased incubated methamphetamine seeking on day 21. Results demonstrate a role of DMS dopamine D1 and D2 receptors in the incubation of methamphetamine craving after voluntary abstinence and that DMS neuronal ensembles mediate this incubation. SIGNIFICANCE STATEMENT: In human addicts, abstinence is often self-imposed and relapse can be triggered by exposure to drug-associated cues that induce drug craving. We recently developed a rat model of incubation of methamphetamine craving after choice-based voluntary abstinence. Here, we used classical pharmacology, in situ hybridization, immunohistochemistry, and the Daun02 inactivation procedure to demonstrate a critical role of dorsomedial striatum neuronal ensembles in this new form of incubation of drug craving

Distinct fos-expressing neuronal ensembles in the ventromedial prefrontal cortex mediate food reward and extinction memories

In operant learning, initial reward-associated memories are thought to be distinct from subsequent extinction-associated memories. Memories formed during operant learning are thought to be stored in “neuronal ensembles.” Thus, we hypothesize that different neuronal ensembles encode reward- and extinction-associated memories. Here, we examined prefrontal cortex neuronal ensembles involved in the recall of reward and extinction memories of food self-administration.Wefirst trained rats to lever press for palatable food pellets for 7 d (1 h/d) and then exposed them to 0, 2, or 7 daily extinction sessions in which lever presses were not reinforced. Twenty-four hours after the last training or extinction session, we exposed the rats to either a short 15 min extinction test session or left them in their homecage (a control condition). We found maximal Fos (a neuronal activity marker) immunoreactivity in the ventral medial prefrontal cortex of rats that previously received 2 extinction sessions, suggesting that neuronal ensembles in this area encode extinction memories. We then used the Daun02 inactivation procedure to selectively disrupt ventral medial prefrontal cortex neuronal ensembles that were activated during the 15 min extinction session following 0 (no extinction) or 2 prior extinction sessions to determine the effects of inactivating the putative food reward and extinction ensembles, respectively, on subsequent nonreinforced food seeking 2 d later. Inactivation of the food reward ensembles decreased food seeking, whereas inactivation of the extinction ensembles increased food seeking. Our results indicate that distinct neuronal ensembles encoding operant reward and extinction memories intermingle within the same cortical area

Sex differences in the effect of chronic delivery of the buprenorphine analogue BU08028 on heroin relapse and choice in a rat model of opioid maintenance

Background and Purpose: Maintenance treatment with opioid agonists (buprenorphine, methadone) decreases opioid use and relapse. We recently modelled maintenance treatment in rats and found that chronic delivery of buprenorphine or the μ opioid receptor partial agonist TRV130 decreased relapse to oxycodone seeking and taking. Here, we tested the buprenorphine analogue BU08028 on different heroin relapse-related measures and heroin versus food choice. Experimental Approach: For relapse assessment, we trained male and female rats to self-administer heroin (6 h·day−1, 14 days) in Context A and then implanted osmotic minipumps containing BU08028 (0, 0.03 or 0.1 mg·kg−1·d−1). Effects of chronic BU08028 delivery were tested on (1) incubation of heroin-seeking in a non-drug Context B, (2) extinction responding reinforced by heroin-associated discrete cues in Context B, (3) reinstatement of heroin-seeking induced by re-exposure to Context A and (4) re-acquisition of heroin self-administration in Context A. For choice assessment, we tested the effect of chronic BU08028 delivery on heroin versus food choice. Key Results: Chronic BU08028 delivery decreased incubation of heroin seeking. Unexpectedly, BU08028 increased re-acquisition of heroin self-administration selectively in females. Chronic BU08028 had minimal effects on context-induced reinstatement and heroin versus food choice in both sexes. Finally, exploratory post hoc analyses suggest that BU08028 decreased extinction responding selectively in males. Conclusions and Implications: Chronic BU08028 delivery had both beneficial and detrimental, sex-dependent, effects on different triggers of heroin relapse and minimal effects on heroin choice in both sexes. Results suggest that BU08028 would not be an effective opioid maintenance treatment in humans.</p

Role of Ventral Subiculum in Context-Induced Relapse to Alcohol Seeking after Punishment-Imposed Abstinence

In many human alcoholics, abstinence is self-imposed because of the negative consequences of excessive alcohol use, and relapse is often triggered by exposure to environmental contexts associated with prior alcohol drinking. We recently developed a rat model of this human condition in which we train alcohol-preferring P rats to self-administer alcohol in one context (A), punish the alcohol-reinforced responding in a different context (B), and then test for relapse to alcohol seeking in Contexts A and B without alcohol or shock. Here, we studied the role of projections to nucleus accumbens (NAc) shell from ventral subiculum (vSub), basolateral amygdala, paraventricular thalamus, and ventral medial prefrontal cortex in context-induced relapse after punishment-imposed abstinence. First, we measured double-labeling of the neuronal activity marker Fos with the retrograde tracer cholera toxin subunit B (injected in NAc shell) and demonstrated that context-induced relapse is associated with selective activation of the vSub→NAc shell projection. Next, we reversibly inactivated the vSub with GABA receptor agonists (muscimol+baclofen) before the context-induced relapse tests and provided evidence for a causal role of vSub in this relapse. Finally, we used a dual-virus approach to restrict expression of the inhibitory κ opioid-receptor based DREADD (KORD) in vSub→NAc shell projection neurons. We found that systemic injections of the KORD agonist salvinorin B, which selectively inhibits KORD-expressing neurons, decreased context-induced relapse to alcohol seeking. Our results demonstrate a critical role of vSub in context-induced relapse after punishment-imposed abstinence and further suggest a role of the vSub→NAc projection in this relapse. SIGNIFICANCE STATEMENT In many human alcoholics, abstinence is self-imposed because of the negative consequences of excessive use, and relapse is often triggered by exposure to environmental contexts associated with prior alcohol use. Until recently, an animal model of this human condition did not exist. We developed a rat model of this human condition in which we train alcohol-preferring P rats to self-administer alcohol in one context (A), punish the alcohol-reinforced responding in a different context (B), and test for relapse to alcohol seeking in Contexts A and B. Here, we used neuroanatomical, neuropharmacological, and chemogenetic methods to demonstrate a role of ventral subiculum and potentially its projections to nucleus accumbens in context-induced relapse after punishment-imposed abstinence

Identification of Brain Nuclei Implicated in Cocaine-Primed Reinstatement of Conditioned Place Preference: A Behaviour Dissociable from Sensitization

Relapse prevention represents the primary therapeutic challenge in the treatment of drug addiction. As with humans, drug-seeking behaviour can be precipitated in laboratory animals by exposure to a small dose of the drug (prime). The aim of this study was to identify brain nuclei implicated in the cocaine-primed reinstatement of a conditioned place preference (CPP). Thus, a group of mice were conditioned to cocaine, had this place preference extinguished and were then tested for primed reinstatement of the original place preference. There was no correlation between the extent of drug-seeking upon reinstatement and the extent of behavioural sensitization, the extent of original CPP or the extinction profile of mice, suggesting a dissociation of these components of addictive behaviour with a drug-primed reinstatement. Expression of the protein product of the neuronal activity marker c-fos was assessed in a number of brain regions of mice that exhibited reinstatement (R mice) versus those which did not (NR mice). Reinstatement generally conferred greater Fos expression in cortical and limbic structures previously implicated in drug-seeking behaviour, though a number of regions not typically associated with drug-seeking were also activated. In addition, positive correlations were found between neural activation of a number of brain regions and reinstatement behaviour. The most significant result was the activation of the lateral habenula and its positive correlation with reinstatement behaviour. The findings of this study question the relationship between primed reinstatement of a previously extinguished place preference for cocaine and behavioural sensitization. They also implicate activation patterns of discrete brain nuclei as differentiators between reinstating and non-reinstating mice

New technologies for examining neuronal ensembles in drug addiction and fear

Correlational data suggest that learned associations are encoded within neuronal ensembles. However, it has been difficult to prove that neuronal ensembles mediate learned behaviours because traditional pharmacological and lesion methods, and even newer cell type-specific methods, affect both activated and non-activated neurons. Additionally, previous studies on synaptic and molecular alterations induced by learning did not distinguish between behaviourally activated and non-activated neurons. Here, we describe three new approaches—Daun02 inactivation, FACS sorting of activated neurons and c-fos-GFP transgenic rats — that have been used to selectively target and study activated neuronal ensembles in models of conditioned drug effects and relapse. We also describe two new tools — c-fos-tTA mice and inactivation of CREB-overexpressing neurons — that have been used to study the role of neuronal ensembles in conditioned fear

Circumventing 'free care' and 'shouting louder':Using a health systems approach to study eye health system sustainability in government &amp; mission facilities of north-west Tanzania.

BACKGROUND: Little is known about the contributions of faith-based organisations (FBOs) to health systems in Africa. In the specialist area of eye health, international and domestic Christian FBOs have been important contributors as service providers and donors, but they are also commonly critiqued as having developed eye health systems parallel to government structures which are unsustainable. METHODS: In this study, we use a health systems approach (quarterly interviews, a participatory sustainability analysis exercise and a social network analysis) to describe the strategies used by eye care practitioners in four hospitals of north-west Tanzania to navigate the government, church mission and donor rules that govern eye services delivery there. RESULTS: Practitioners in this region felt eye care was systemically neglected by government and therefore was 'all under the NGOs', but support from international donors was also precarious. Practitioners therefore adopted four main strategies to improve the sustainability of their services: (1) maintain 'sustainability funds' to retain financial autonomy over income; (2) avoid granting government user fee exemptions to elderly patients who are the majority of service users; (3) expand or contract outreach services as financial circumstances change; and (4) access peer support for problem-solving and advocacy. Mission-based eye teams had greater freedom to increase their income from user fees by not implementing government policies for 'free care'. Teams in all hospitals, however, found similar strategies to manage their programmes even when their management structures were unique, suggesting the importance of informal rules shared through a peer network in governing eye care in this pluralistic health system. CONCLUSIONS: Health systems research can generate new evidence on the social dynamics that cross public and private sectors within a local health system. In this area of Tanzania, Christian FBOs' investments are important, not only in terms of the population health outcomes achieved by teams they support, but also in the diversity of organisational models they contribute to in the wider eye health system, which facilitates innovation

Advancing the application of systems thinking in health:analysing the contextual and social network factors influencing the use of sustainability indicators in a health system - a comparative study in Nepal and Somaliland

BACKGROUND: Health systems strengthening is becoming a key component of development agendas for low-income countries worldwide. Systems thinking emphasizes the role of diverse stakeholders in designing solutions to system problems, including sustainability. The objective of this paper is to compare the definition and use of sustainability indicators developed through the Sustainability Analysis Process in two rehabilitation sectors, one in Nepal and one in Somaliland, and analyse the contextual factors (including the characteristics of system stakeholder networks) influencing the use of sustainability data. METHODS: Using the Sustainability Analysis Process, participants collectively clarified the boundaries of their respective systems, defined sustainability, and identified sustainability indicators. Baseline indicator data was gathered, where possible, and then researched again 2 years later. As part of the exercise, system stakeholder networks were mapped at baseline and at the 2-year follow-up. We compared stakeholder networks and interrelationships with baseline and 2-year progress toward self-defined sustainability goals. Using in-depth interviews and observations, additional contextual factors affecting the use of sustainability data were identified. RESULTS: Differences in the selection of sustainability indicators selected by local stakeholders from Nepal and Somaliland reflected differences in the governance and structure of the present rehabilitation system. At 2 years, differences in the structure of social networks were more marked. In Nepal, the system stakeholder network had become more dense and decentralized. Financial support by an international organization facilitated advancement toward self-identified sustainability goals. In Somaliland, the small, centralised stakeholder network suffered a critical rupture between the system's two main information brokers due to competing priorities and withdrawal of international support to one of these. Progress toward self-defined sustainability was nil. CONCLUSIONS: The structure of the rehabilitation system stakeholder network characteristics in Nepal and Somaliland evolved over time and helped understand the changing nature of relationships between actors and their capacity to work as a system rather than a sum of actors. Creating consensus on a common vision of sustainability requires additional system-level interventions such as identification of and support to stakeholders who promote systems thinking above individual interests

Role of corticostriatal circuits in context-induced reinstatement of drug seeking

Drug addiction is characterized by persistent relapse vulnerability during abstinence. In abstinent drug users, relapse is often precipitated by re-exposure to environmental contexts that were previously associated with drug use. This clinical scenario is modeled in preclinical studies using the context-induced reinstatement procedure, which is based on the ABA renewal procedure. In these studies, context-induced reinstatement of drug seeking is reliably observed in laboratory animals that were trained to self-administer drugs abused by humans. In this review, we summarize neurobiological findings from preclinical studies that have focused on the role of corticostriatal circuits in context-induced reinstatement of heroin, cocaine, and alcohol seeking. We also discuss neurobiological similarities and differences in the corticostriatal mechanisms of context-induced reinstatement across these drug classes. We conclude by briefly discussing future directions in the study of context-induced relapse to drug seeking in rat models. Our main conclusion from the studies reviewed is that there are both similarities (accumbens shell, ventral hippocampus, and basolateral amygdala) and differences (medial prefrontal cortex and its projections to accumbens) in the neural mechanisms of context-induced reinstatement of cocaine, heroin, and alcohol seeking. This article is part of a Special Issue entitled SI:Addiction circuits

The reinstatement model of drug relapse: Recent neurobiological findings, emerging research topics, and translational research

Background and rationale: Results from many clinical studies suggest that drug relapse and craving are often provoked by acute exposure to the self-administered drug or related drugs, drug-associated cues or contexts, or certain stressors. During the last two decades, this clinical scenario has been studied in laboratory animals by using the reinstatement model. In this model, reinstatement of drug seeking by drug priming, drug cues or contexts, or certain stressors is assessed following drug self-administration training and subsequent extinction of the drug-reinforced responding. Objective: In this review, we first summarize recent (2009-present) neurobiological findings from studies using the reinstatement model. We then discuss emerging research topics, including the impact of interfering with putative reconsolidation processes on cue- and context-induced reinstatement of drug seeking, and similarities and differences in mechanisms of reinstatement across drug classes. We conclude by discussing results from recent human studies that were inspired by results from rat studies using the reinstatement model. Conclusions: Main conclusions from the studies reviewed highlight: (1) the ventral subiculum and lateral hypothalamus as emerging brain areas important for reinstatement of drug seeking, (2) the existence of differences in brain mechanisms controlling reinstatement of drug seeking across drug classes, (3) the utility of the reinstatement model for assessing the effect of reconsolidation-related manipulations on cue-induced drug seeking, and (4) the encouraging pharmacological concordance between results from rat studies using the reinstatement model and human laboratory studies on cue- and stress-induced drug craving