Preferences for Long-Acting PrEP Products Among Women and Girls: A Quantitative Survey and Discrete Choice Experiment in Eswatini, Kenya, and South Africa.

While oral pre-exposure prophylaxis (PrEP) can substantially reduce HIV risk, there are important barriers to uptake and adherence. We explored preferences for long-acting injectable and implantable PrEP among women and girls in Eswatini, Kenya, and South Africa. We conducted an online quantitative survey and discrete choice experiment (DCE) among adolescent girls (15-17), young women (18-29), and adult women (30-49). Participants completed a survey about their demographics and behavior and a DCE with 5 attributes (format, insertion location, number of insertions, dual-protection, and palpability). We recruited 1236 respondents (Eswatini = 420; Kenya = 350; South Africa = 493) in May 2022. Most participants were sexually active (72%), nearly 29% of whom reported recently engaging in transactional sex. 46% had heard of oral PrEP, but of those, only 16% reported having ever used it. Product format and dual-protection were significant predictors of product choice. Relative to a 2-month injection, participants had 1.76 times the odds (95% CI 1.08-2.04) of choosing a 6-month injectable, and 1.70 the odds (95% CI 1.06-1.92) of choosing a 12-month removable implant. Compared to a single-indication product, respondents had 2.46 times the odds (95% CI 1.04-2.68) of preferring a product also protecting against pregnancy, and 2.81 the odds (95% CI 1.04-3.05) of choosing a product that also protected against STIs. Adolescent girls and women in these countries showed strong preferences for longer-acting PrEP product formats, as well as those offering dual-protection. Introduction of long-acting options could improve PrEP uptake and reduce HIV burdens in east and southern African settings.

Single-Administration Long-Acting Microarray Patch with Ultrahigh Loading Capacity and Multiple Releases of Thermally Stable Antibodies.

Current antibody (Ab) therapies require development of stable formulations and an optimal delivery system. Here, we present a new strategy to create a single-administration long-lasting Ab-delivery microarray (MA) patch, which can carry high doses of thermally stabilized Abs. The MA fabricated by an additive three-dimensional manufacturing technology can be fully embedded into the skin via a single application to deliver doses of Abs at multiple programmable time points, thus sustaining Ab concentrations in systemic circulation. We developed an MA formulation that stabilized and delivered human immunoglobulins (hIg) in a time-controlled manner while maintaining their structure and functionality. As an example, the b12 Ab─a broadly neutralizing Ab against HIV-1─maintained antiviral activity in vitro after MA manufacturing and heat exposure. Pharmacokinetic studies of MA patch-delivered hIg in rats successfully provided a proof of concept for concurrent and time-delayed Ab delivery. These MA patches codeliver different Abs, providing a tool for expanded protection against viral infections or combination HIV therapy and prevention.

HIV Pre-exposure Prophylaxis Implant Stated Preferences and Priorities: Results of a Discrete Choice Experiment Among Women and Adolescent Girls in Gauteng Province, South Africa.

For adolescent girls (AG) and young women (YW), adherence barriers may limit the effectiveness of daily oral HIV pre-exposure prophylaxis (PrEP). Due to its low-burden and long-lasting product attributes, PrEP implants could remove some of the critical adherence barriers of oral PrEP products for individuals at risk of HIV. To explore stated preferences for a long-acting PrEP implant, we conducted a quantitative survey and discrete choice experiment with AG (ages 15-17), YW (18-34), and female sex workers (FSW; ≥ 18) in Gauteng Province, South Africa. We completed 600 quantitative surveys across the three subgroups of women. Respondents stated preference for an implant that provided longer HIV protection (24 months versus 6 months) and required a single insertion. They stated that they preferred a biodegradable implant that could be removed within 1 month of insertion. Respondents had no preference for a particular insertion location. Overall, 78% of respondents said they would be likely (33%) or very likely (45%) to use a PrEP implant were one available, with the majority (82%) stating preference for a product that would provide dual protection against HIV and unintended pregnancies. To reduce their risk of HIV, AG, YW, and FSW in our survey reported a strong willingness to use long-acting, highly-effective, dissolvable PrEP implants.

RESUMEN: Las niñas adolescentes (NA) y mujeres jóvenes (MJ), pueden enfrentar barreras de adherencia que limitan la eficacia de la profilaxis oral previa a la exposición al VIH (PrEP). Ya que el implante de PrEP es un producto que requiere de poca intervención de la usuaria y es de larga duración, podría eliminar algunas de las barreras de adherencia más importantes en el uso de los productos orales de PrEP para aquellas personas en riesgo de infección de VIH. Para explorar las preferencias declaradas en cuanto al implante de PrEP de acción prolongada, llevamos a cabo una encuesta cuantitativa y un experimento de elección discreta (DCE) con NA (de 15 a 17 años), MJ (de 18 a 34 años) y mujeres trabajadoras del sexo (MTS; ≥ 18 años) en la provincia de Gauteng, Sudáfrica. Administramos 600 encuestas cuantitativas en los tres subgrupos de mujeres. Los resultados indican la preferencia por un implante que proporciona una protección contra el VIH más prolongada (24 meses a comparación con 6 meses) y que requiere de una única inserción. Las participantes afirmaron que prefieren un implante biodegradable que puede retirarse un mes después de su inserción. Las participantes no tenían preferencia por un sitio específico de inserción. En general, el 78% de las participantes indicaron que probablemente (33%) o muy probablemente (45%) utilizarían un implante de PrEP si estuviera disponible, y la mayoría (82%) manifestó su preferencia por un producto que proporcionaba una doble protección contra el VIH y el embarazo no deseado. Para reducir el riesgo de contraer el VIH, las NA, MJ y MTS participantes se mostraron muy dispuestas a utilizar implantes de PrEP de larga duración, altamente eficaces y disolubles.

Seminal exosomes and HIV-1 transmission.

Exosomes are endosomal-derived membrane-confined nanovesicles secreted by many (if not all) cell types and isolated from every human bodily fluid examined up to now including plasma, semen, vaginal secretions and breast milk. Exosomes are thought to represent a new player in cell-to-cell communication pathways and immune regulation, and be involved in many physiological and pathological processes. Susceptibility to HIV-1 infection can be impacted by exosomes, while HIV-1 pathogenesis can alter exosomal function and composition. Exosomes isolated from semen and vaginal fluid of healthy individuals can inhibit HIV-1 infection and/or potently block viral transfer in vitro. However, the role of exosomes in HIV-1 transmission and progression is not fully understood yet and some studies show conflicting results, mainly for exosomes isolated from plasma and breast milk. Determining the composition of exosomes from infected donors and studying their interaction with HIV-1 in vitro compared to exosomes isolated from uninfected donors will provide insights into the role exosomes play in HIV-1 transmission during sexual intercourse and breastfeeding.

Characterization of diseased primary human hepatocytes in an all-human cell-based triculture system.

Liver diseases, including NAFLD, are a growing worldwide health concern. Currently, there is a lack of suitable in vitro models that sustain basic primary human hepatocyte (PHH) morphology and functionality while supporting presentation of disease-associated phenotypic characteristics such as lipid accumulation and inflammasome activation. In TruVivo, an all-human triculture system (hTCS), basic metabolic functions were characterized in PHHs isolated from normal or diseased livers during two-weeks of culture. Decreases in albumin and urea levels and CYP3A4 activity were seen in diseased-origin PHHs compared to normal PHHs along with higher CYP2E1 expression. Positive expression of the macrophage markers CD68 and CD163 were seen in the diseased PHH preparations. Elevated levels of the pro-inflammatory cytokines IL-6 and MCP-1 and the fibrotic markers CK-18 and TGF-ß were also measured. Gene expression of FASN, PCK1, and G6PC in the diseased PHHs was decreased compared to the normal PHHs. Further characterization revealed differences in lipogenesis and accumulation of intracellular lipids in normal and diseased PHHs when cultured with oleic acid and high glucose. TruVivo represents a promising new platform to study lipogenic mechanisms in normal and diseased populations due to the preservation of phenotypic differences over a prolonged culture period.

CaMKII: a biochemical bridge linking accumbens dopamine and glutamate systems in cocaine seeking.

Increases in dopamine and glutamate transmission in the nucleus accumbens independently promote the reinstatement of cocaine seeking, an animal model of relapse. Here we have tested whether cocaine reinstatement in rats depends on interactions between accumbal dopamine and glutamate systems that are mediated by Ca(2+)/calmodulin-mediated kinase II (CaMKII). We show that stimulation of D1-like dopamine receptors in the nucleus accumbens shell reinstates cocaine seeking by activating L-type Ca(2+) channels and CaMKII. Cocaine reinstatement is associated with D1-like dopamine receptor-dependent increases in accumbens shell CaMKII phosphorylated on Thr286 and glutamate receptor 1 (GluR1) phosphorylated on Ser831 (a known CaMKII phosphorylation site), in addition to increases in cell-surface expression of GluR1-containing AMPA receptors in the shell. Consistent with these findings, cocaine reinstatement is attenuated by intra-shell administration of AAV10-GluR1-C99, a vector that impairs the transport of GluR1-containing AMPA receptors. Thus, CaMKII may be an essential link between accumbens shell dopamine and glutamate systems involved in the neuronal plasticity underlying cocaine craving and relapse.

Long-acting HIV pre-exposure prophylaxis (PrEP) approaches: recent advances, emerging technologies, and development challenges.

INTRODUCTION: Poor or inconsistent adherence to daily oral pre-exposure prophylaxis (PrEP) has emerged as a key barrier to effective HIV prevention. The advent of potent long-acting (LA) antiretrovirals (ARVs) in conjunction with advances in controlled release technologies has enabled LA ARV drug delivery systems (DDS) capable of providing extended dosing intervals and overcome the challenge of suboptimal drug adherence with daily oral dosing. AREAS COVERED: This review discusses the current state of the LA PrEP field, recent advances, and emerging technologies, including ARV prodrug modifications and new DDS. Technological challenges, knowledge gaps, preclinical testing considerations, and future directions important in the context of clinical translation and implementation of LA HIV PrEP are discussed. EXPERT OPINION: The HIV prevention field is evolving faster than ever and the bar for developing next-generation LA HIV prevention options continues to rise. The requirements for viable LA PrEP products to be implemented in resource-limited settings are challenging, necessitating proactive consideration and product modifications during the design and testing of promising new candidates. If successfully translated, next-generation LA PrEP that are safe, affordable, highly effective, and accepted by both end-users and key stakeholders will offer significant potential to curb the HIV pandemic.

Vitamin D Status Impacts Genital Mucosal Immunity and Markers of HIV-1 Susceptibility in Women.

While vitamin D insufficiency is known to impact a multitude of health outcomes, including HIV-1, little is known about the role of vitamin D-mediated immune regulation in the female reproductive tract (FRT). We performed a pilot clinical study of 20 women with circulating 25(OH)D levels <62.5 nmol/L. Participants were randomized into either weekly or daily high-dose oral vitamin D supplementation groups. In addition to serum vitamin D levels, genital mucosal endpoints, including soluble mediators, immune cell populations, gene expression, and ex vivo HIV-1 infection, were assessed. While systemic vitamin D levels showed a significant increase following supplementation, these changes translated into modest effects on the cervicovaginal factors studied. Paradoxically, post-supplementation vitamin D levels were decreased in cervicovaginal fluids. Given the strong correlation between vitamin D status and HIV-1 infection and the widespread nature of vitamin D deficiency, further understanding of the role of vitamin D immunoregulation in the female reproductive tract is important.

Vaginal microbiota and mucosal pharmacokinetics of tenofovir in healthy women using tenofovir and tenofovir/levonorgestrel vaginal rings.

Recent data support that the vaginal microbiota may alter mucosal pharmacokinetics (PK) of topically delivered microbicides. Our team developed an intravaginal ring (IVR) that delivers tenofovir (TFV) (8-10 mg/day) alone or with levonorgestrel (LNG) (20 ug/day). We evaluated the effect of IVRs on the vaginal microbiota, and describe how the vaginal microbiota impacts mucosal PK of TFV. CONRAD A13-128 was a randomized, placebo controlled phase I study. We randomized 51 women to TFV, TFV/LNG or placebo IVR. We assessed the vaginal microbiota by sequencing the V3-V4 regions of 16S rRNA genes prior to IVR insertion and after approximately 15 days of use. We measured the concentration of TFV in the cervicovaginal (CV) aspirate, and TFV and TFV-diphosphate (TFV-DP) in vaginal tissue at the end of IVR use. The change in relative or absolute abundance of vaginal bacterial phylotypes was similar among active and placebo IVR users (all q values >0.13). TFV concentrations in CV aspirate and vaginal tissue, and TFV-DP concentrations in vaginal tissue were not significantly different among users with community state type (CST) 4 versus those with Lactobacillus dominated microbiota (all p values >0.07). The proportions of participants with CV aspirate concentrations of TFV >200,000 ng/mL and those with tissue TFV-DP concentrations >1,000 fmol/mg were similar among women with anaerobe versus Lactobacillus dominated microbiota (p = 0.43, 0.95 respectively). There were no significant correlations between the CV aspirate concentration of TFV and the relative abundances of Gardnerella vaginalis or Prevotella species. Tissue concentrations of TFV-DP did not correlate with any the relative abundances of any species, including Gardnerella vaginalis. In conclusion, active IVRs did not differ from the placebo IVR on the effect on the vaginal microbiota. Local TFV and TFV-DP concentrations were high and similar among IVR users with Lactobacillus dominated microbiota versus CST IV vaginal microbiota. Trial registration: ClinicalTrials.gov NCT02235662.

Topical Inserts: A Versatile Delivery Form for HIV Prevention.

The development of topical inserts for the prevention of sexually transmitted infections (STIs), particularly human immunodeficiency virus (HIV), represents a promising alternative to oral and parenteral pre-exposure prophylaxis (PrEP) dosage forms. They may be used for vaginal and/or rectal administration of a variety of agents with antiviral activity. Topical inserts deliver drugs to the portal of viral entry, i.e., the genital or rectal mucosa, with low systemic exposure, and therefore are safer and have fewer side effects than systemic PrEP agents. They may dissolve fast, releasing the active drugs within minutes of insertion, or slowly for long-acting drug delivery. Furthermore, they are user-friendly being easy to administer, discreet and highly portable. They are also economical and easy to manufacture at scale and to distribute, with excellent stability and shelf-life. Altogether, topical inserts represent a particularly promising form of drug delivery for HIV and STI prevention. Highlighted within this review are end-user acceptability research dedicated to understanding preferred attributes for this form of drug delivery, advantages and disadvantages of the formulation platform options, considerations for their development, clinical assessment of select placebo prototypes, future directions, and the potential impact of this dosage form on the HIV prevention landscape.

Use of contraceptive depot medroxyprogesterone acetate is associated with impaired cervicovaginal mucosal integrity.

BACKGROUND: Injectable depot medroxyprogesterone acetate (DMPA) is one of the most popular contraception methods in areas of high HIV seroprevalence. Evidence is accumulating that use of DMPA might be associated with an increased risk of HIV-1 acquisition by women; however, mechanisms of this association are not completely understood. The goal of this study was to gain insight into mechanisms underlying the possible link between use of DMPA and risk of HIV-1 acquisition, exploring transcription profiling of ectocervical tissues. METHODS: Healthy women received either DMPA (n = 31) or combined oral contraceptive (COC), which has not been linked to an increased risk of HIV acquisition (n = 32). We conducted a comparative microarray-based whole-genome transcriptome profiling of human ectocervical tissues before and after 6 weeks of hormonal contraception use. RESULTS: The analysis identified that expression of 235 and 76 genes was significantly altered after DMPA and COC use, respectively. The most striking effect of DMPA, but not COC, was significantly altered expression (mostly downregulation) of many genes strategically involved in the maintenance of mucosal barrier function; the alterations, as indicated by Ingenuity Pathway Analysis (IPA), were most likely due to the DMPA-induced estrogen deficiency. Furthermore, IPA predicted that transcriptome alterations related to ectocervical immune responses were in general compatible with an immunosuppressive effect of DMPA, but, in some women, also with an inflammatory-like response. CONCLUSION: Our results suggest that impairment of cervicovaginal mucosal integrity in response to DMPA administration is an important mechanism contributing to the potential increased risk of HIV-1 acquisition in DMPA users. TRIAL REGISTRATION: ClinicalTrials.gov NCT01421368. FUNDING: This study was supported by the United States Agency for International Development (USAID) under Cooperative Agreement GPO-A-00-08-00005-00.

Differences in Local and Systemic TFV PK Among Premenopausal Versus Postmenopausal Women Exposed to TFV 1% Vaginal Gel.

OBJECTIVE: We describe and compare the local and systemic pharmacokinetics (PK) of tenofovir (TFV) and TFV-diphosphate (TFV-DP) in healthy premenopausal (PRE) and postmenopausal (POST) women using TFV 1% gel and correlate local PK with other mucosal end points. METHODS: PRE (n = 20) and POST (n = 17) women used 2 doses of TFV 1% vaginal gel, separated by 2 hours. Blood and cervicovaginal samples were obtained 3 and 23 hours after the second dose. PRE women used gel in the follicular and luteal phases of the menstrual cycle. POST women used gel at baseline and again after approximately 2 months of treatment with 0.01% vaginal estradiol (E2) cream. RESULTS: Median TFV concentrations in cervicovaginal aspirate (ng/mL) and vaginal tissue (ng/mg) were significantly higher in PRE (4.3E10, 49.8) versus POST women (2.6E10, 2.2). POST women had significantly higher median molecular ratios of TFV-DP to TFV (3.7%) compared with PRE (0.19%). After vaginal E2 treatment, the local and systemic PK end points in POST women were generally similar to PRE women (all P values > 0.05). Importantly, median vaginal tissue TFV-DP concentrations (fmol/mg) among PRE, POST, and POST women after E2 therapy were similar (292.5, 463.3, and 184.6, respectively). Vaginal tissue TFV concentrations were significantly positively correlated with vaginal epithelial thickness, whereas vaginal tissue TFV-DP concentrations were positively correlated with density of vaginal CD4 and CD8 immune cells. CONCLUSIONS: The state of the cervicovaginal mucosa has a significant impact on local and systemic PK of a topically applied microbicide.

Comparison of Mucosal Markers of Human Immunodeficiency Virus Susceptibility in Healthy Premenopausal Versus Postmenopausal Women.

The objective of this study was to characterize cervicovaginal (CV) mucosal factors modulating susceptibility to human immunodeficiency virus (HIV) acquisition in healthy premenopausal (PRE) and postmenopausal (POST) women before and after treatment with estradiol (E2). We compared CV mucosal epithelial histology and immune cells, vaginal microbiota, antimicrobial activity of and soluble mucosal protein concentrations in the CV fluid lavage (CVL), and p24 antigen production after ex vivo infection of ectocervical tissues with HIV-1BaL among PRE women (n = 20) in the follicular and luteal phases of the menstrual cycle and POST women (n = 17) at baseline and after ∼1 month of treatment with 0.01% vaginal E2 cream. Compared to PRE women, we measured higher levels of p24 antigen after ex vivo infection in tissues from POST women. POST women had a significantly thinner vaginal epithelium with decreased tight junction proteins and a higher density of mucosal immune T cells and lower levels of CD1a antigen-presenting cells, antimicrobial peptides, and inflammatory cytokines in the CVL (p values <.05). POST women had higher vaginal pH and lower vaginal Lactobacilli (p values <.05) than PRE women. After vaginal E2 therapy, CV endpoints and ex vivo HIV replication in POST tissues were similar to those observed in PRE tissues. The CV mucosa in POST women is thinned and compromised, with increased HIV-target immune cells and decreased antimicrobial factors, being more susceptible to HIV infection. After POST women receive topical E2 treatment, mucosal endpoints are similar to PRE levels.

Administration of the D2 dopamine receptor antagonist sulpiride into the shell, but not the core, of the nucleus accumbens attenuates cocaine priming-induced reinstatement of drug seeking.

Enhanced dopamine transmission in the nucleus accumbens plays an important role in cocaine priming-induced reinstatement of drug-seeking behavior. However, the contribution of each dopamine receptor subtype to this behavior remains unclear. The present experiments were designed to assess the role of D2-like dopamine receptors in the nucleus accumbens core and shell subregions in cocaine priming-induced reinstatement of drug seeking. Rats were trained to lever press for cocaine using a fixed ratio (FR) 5 schedule of reinforcement. After approximately 18 days of cocaine self-administration, the animals underwent an extinction phase during which cocaine was replaced with saline. Daily extinction sessions were conducted until responding was less than 10% of the response rate maintained by cocaine self-administration. Following the extinction phase, priming-induced reinstatement of cocaine-seeking behavior was assessed. A range of doses of antagonists selective for D2- (sulpiride, 0.2 or 2.0 microg), D3- (U99194A, 3.9 or 7.8 microg), or D4- (L-750,667, 5.5 or 11 microg) dopamine receptors were microinjected into either the nucleus accumbens core, shell or lateral septum prior to a priming injection of cocaine (10 mg/kg, i.p.). Following administration into the shell, but not core or lateral septum, sulpiride dose-dependently attenuated reinstatement induced by a cocaine priming injection. In contrast, U99194A and L-750,667 failed to influence cocaine seeking at any of the doses tested in either accumbal subregion. Collectively, these findings indicate that activation of D2 dopamine receptors mediates cocaine priming-induced reinstatement of cocaine seeking in a region-specific manner within the nucleus accumbens.

Comparison of Follicular and Luteal Phase Mucosal Markers of HIV Susceptibility in Healthy Women.

The purpose of this study was to evaluate differences in vaginal immune cell populations, vaginal tissue gene expression, antimicrobial activity of the cervicovaginal (CV) lavage (CVL), vaginal flora, and p24 antigen production from CV tissues after ex vivo human immunodeficiency virus (HIV) infection between follicular (FOL) and luteal (LUT) phases of the menstrual cycle. CV tissue biopsies, CV secretions, and blood samples were obtained as part of two longitudinal clinical trials of healthy women (CONRAD D11-119 and A12-124 studies). Participants (n = 39) were HIV-seronegative women not using exogenous hormone supplementation, with normal menstrual cycles, who were screened to exclude sexually transmitted and reproductive tract infections. Serum levels of estradiol and progesterone were significantly higher in the LUT versus the FOL phase of the menstrual cycle. Controlling for race, reported contraceptive use/sexual practices, and clinical trial, we found no differences in vaginal tissue immune cell populations and activation status, transcriptomes, inhibition of HIV, herpes simplex virus type 2 and Escherichia coli by the CVL, vaginal pH or Nugent score, or production of p24 antigen after ex vivo infection by HIV-1BaL between CV samples obtained in the FOL phase versus the LUT phase of the menstrual cycle. There were no significant correlations between serum estradiol and progesterone levels and CV endpoints. The hypothesis that the LUT phase of the menstrual cycle represents a more vulnerable stage for mucosal infection with HIV was not supported by data from samples obtained from the lower genital tract (ectocervix and vagina) from these two clinical trials.

Anatomy and pharmacology of cocaine priming-induced reinstatement of drug seeking.

Cocaine addiction in human addicts is characterized by a high rate of relapse following successful detoxification. Relapse to drug taking/seeking can be precipitated by several stimuli including, but not limited to, re-exposure to cocaine itself. In order to understand the mechanisms underlying cocaine craving, a substantial effort has been devoted to elucidating the anatomical and neurochemical bases underlying cocaine priming-induced reinstatement, an animal model of relapse. Here, we review evidence that changes in dopaminergic and glutamatergic transmission in limbic/basal ganglia circuits of interconnected nuclei including the medial prefrontal cortex, nucleus accumbens, ventral pallidum, amygdala, hippocampus, orbitofrontal cortex, neostriatum and thalamus underlie cocaine priming-induced reinstatement of cocaine seeking. Maladaptive changes in the processing of motivationally relevant stimuli by these circuits following cocaine self-administration result in drug craving and compulsive drug seeking upon re-exposure to cocaine.

Administration of the D1-like dopamine receptor antagonist SCH-23390 into the medial nucleus accumbens shell attenuates cocaine priming-induced reinstatement of drug-seeking behavior in rats.

RATIONALE: A growing literature indicates that increased dopamine transmission in the nucleus accumbens contributes to priming-induced reinstatement of cocaine-seeking behavior. OBJECTIVES: The present experiments were designed to assess the role of D(1)-like dopamine receptors in the nucleus accumbens core and shell subregions in cocaine priming-induced reinstatement of drug seeking. METHODS: Rats were trained to lever press for cocaine using a fixed ratio (FR) 5 schedule of reinforcement. Drug-seeking was measured by active lever presses during daily 2-h sessions. After approximately 30 days of cocaine self-administration, the animals underwent an extinction phase during which cocaine was replaced with saline. Daily extinction sessions were conducted until responding was consistently less than 10% of the response rate maintained by cocaine self-administration. After the extinction phase, priming-induced reinstatement of cocaine-seeking behavior was assessed. RESULTS: Cocaine dose-dependently reinstated cocaine seeking, with robust drug seeking at 10 mg/kg cocaine. Administration of the D(1)-like dopamine receptor antagonist, SCH-23390 (0.1-1.0 micro g), directly into the medial nucleus accumbens shell dose-dependently attenuated drug seeking induced by 10 mg/kg cocaine. Microinjection of 1.0 micro g SCH-23390 into either the nucleus accumbens core or lateral septum had no influence on cocaine-seeking behavior. CONCLUSIONS: These results indicate that stimulation of D(1)-like dopamine receptors in the medial nucleus accumbens shell contributes to drug-induced reinstatement of cocaine-seeking behavior.

Metabotropic glutamate receptor 5 (mGluR5) antagonists attenuate cocaine priming- and cue-induced reinstatement of cocaine seeking.

Accumulating evidence suggests that metabotropic glutamate receptors (mGluRs) are involved in both cocaine reinforcement and the reinstatement of cocaine-seeking behavior. In the present experiments, rats were trained to self-administer cocaine under fixed ratio (for cocaine priming-induced reinstatement) or second-order (for cocaine cue-induced reinstatement) schedules of reinforcement. Lever pressing was then extinguished followed by a reinstatement phase where operant responding was promoted by either cocaine itself or cocaine-associated light cues. Results indicated that systemic administration of the mGluR5 antagonists 2-methyl-6-(phenylethynyl)pyridine (MPEP: 1 and 3mg/kg i.p.) or 3-((2-methyl-1,3-thiazol-4-yl)ethynyl)pyridine (MTEP: 0.1 and 1mg/kg i.p.) dose-dependently attenuated reinstatement of drug seeking induced by a systemic priming injection of 10mg/kg cocaine. Systemic administration of MTEP (0.1 and 1mg/kg i.p.) also dose-dependently attenuated cocaine cue-induced reinstatement of drug seeking. Systemic administration of neither MPEP nor MTEP influenced the reinstatement of sucrose seeking, which indicates that the effects of these compounds on cocaine seeking were reinforcer specific. Additionally, administration of MPEP (1microg/0.5microl) into the nucleus accumbens shell, a brain region that plays a critical role in cocaine seeking, attenuated cocaine priming-induced reinstatement of drug seeking. These results add to a growing literature indicating that mGluR antagonists attenuate the reinstatement of cocaine seeking. Importantly, the current findings also suggest that activation of mGluR5s specifically in the nucleus accumbens shell may promote the reinstatement of cocaine seeking.

Stimulation of D1-like or D2 dopamine receptors in the shell, but not the core, of the nucleus accumbens reinstates cocaine-seeking behaviour in the rat.

Although increases in dopamine transmission in the brain are clearly involved in the reinstatement of cocaine seeking, the role of nucleus accumbens dopamine in cocaine priming-induced reinstatement remains controversial. The goal of these experiments was to evaluate the relative contributions of D1-like and D2-like dopamine receptors in the nucleus accumbens core and shell in the reinstatement of cocaine-seeking behaviour. Initially, rats were trained to press a lever for cocaine (0.25 mg, i.v.) using a fixed-ratio 5 (FR5) schedule of reinforcement. Responding was then extinguished by substituting saline for cocaine. During the reinstatement phase, subtype-specific dopamine receptor agonists were microinjected into the nucleus accumbens core or medial shell in order to assess their ability to induce cocaine seeking. Administration of the D1/D5 dopamine receptor agonist SKF-81297 (1.0 microg) into the nucleus accumbens shell, but not core, reinstated drug-seeking behaviour. Similarly, microinjection of quinpirole (3.0 microg), a D2/D3 dopamine receptor agonist, into the nucleus accumbens shell and not core reinstated drug-seeking behaviour. In contrast, administration of the D3- or D4-preferring dopamine receptor agonists PD 128,907 (1.5 and 3.0 microg) and PD 168,077 (0.3 and 3.0 microg), respectively, did not promote reinstatement when administered into either the core or the shell. Taken together, these results indicate that activation of D1/D5 or D2 dopamine receptors, in the limbic shell subregion of the nucleus accumbens but not the basal ganglia-orientated accumbens core, promotes the reinstatement of cocaine-seeking behaviour.