Suchergebnisse

Social behavior plays a fundamental role in life of many animal species, allowing the interaction between individuals and sharing of experiences, needs, and goals across them. In humans, some neuropsychiatric diseases, including anxiety, posttraumatic stress disorder and autism spectrum disorders, are often characterized by impaired sociability. Here we report that N-Methyl-3,4-methylenedioxyamphetamine (MDMA, "Ecstasy") at low dose (3mg/kg) has differential effects on mouse social behavior. In some animals, MDMA promotes sociability without hyperlocomotion, whereas in other mice it elevates locomotor activity without affecting sociability. Both WAY-100635, a selective antagonist of 5-HT1A receptor, and L-368899, a selective oxytocin receptor antagonist, abolish prosocial effects of MDMA. Differential quantitative analysis of brain proteome by isobaric tag for relative and absolute quantification technology (iTRAQ) revealed 21 specific proteins that were highly correlated with sociability, and allowed to distinguish between entactogenic prosocial and hyperlocomotor effects of MDMA on proteome level. Our data suggest particular relevance of neurotransmission mediated by GABA B receptor, as well as proteins involved in energy maintenance for MDMA-induced sociability. Functional association network for differentially expressed proteins in cerebral cortex, hippocampus and amygdala were identified. These results provide new information for understanding the neurobiological substrate of sociability and may help to discover new therapeutic approaches to modulate social behavior in patients suffering from social fear and low sociability. ; This work was supported by the Spanish "Ministerio de Ciencia e Innovación" (SAF2011-29864); Spanish "Instituto de Salud Carlos III" (RETICS – Red de Trastornos Adictivos – Redes Temáticas de Investigación Cooperativa en Salud: #RD06/0001/0001, #RD06/0001/1004); Spanish "Plan Nacional sobre Drogas" (PNSD #2009/026); the Catalan Government (SGR2009-00131); and the ICREA Foundation (ICREA Academia-2008). KK-T was supported by a Marie Curie Intra-European Fellowship from the European Commission (MC-2010-274950)

The size of the Azotobacter vinelandii chromosome is approximately 4,700 kb, as calculated by pulsed-field electrophoretic separation of fragments digested with the rarely cutting endonucleases SpeI and SwaI. Surveys of DNA content per cell by flow cytometry indicated the existence of ploidy changes during the A. vinelandii growth cycle in rich medium. Early-exponential-phase cells have a ploidy level similar to that of Escherichia coli or Salmonella typhimurium (probably ca. four chromosomes per cell), but a continuous increase of DNA content per cell is observed during growth. Late-exponential-phase cells may contain > 40 chromosomes per cell, while cells in the early stationary stage may contain > 80 chromosomes per cell. In late-stationary-phase cultures, the DNA content per cell is even higher, probably over 100 chromosome equivalents per cell. A dramatic change is observed in old stationary-phase cultures, when the population of highly polyploid bacteria segregates cells with low ploidy. The DNA content of the latter cells resembles that of cysts, suggesting that the process may reflect the onset of cyst differentiation. Cells with low ploidy are also formed when old stationary-phase cultures are diluted into fresh medium. Addition of rifampin to exponential-phase cultures causes a rapid increase in DNA content, indicating that A. vinelandii initiates multiple rounds of chromosome replication per cell division. Growth in minimal medium does not result in the spectacular changes of ploidy observed during rapid growth; this observation suggests that the polyploidy of A. vinelandii may not exist outside the laboratory. ; This work was supported by grant PB89/0627 from the DGICYT of the Government of Spain. R.M. was a predoctoral fellow under the PFPI program of the Regional Government of Andalusia (Junta de Andalucía), Spain.

Debido a la inexistente recopilación bibliográfica sobre el tocino artesanal azuayo y su casi extinta utilización en la actualidad, la presente publicación tiene como objetivo realizar un estudio comparativo de las cualidades organolépticas entre el tocino tradicional y su contraste con el tocino industrial aplicado en elaboraciones típicas de la gastronomía de la provincia. Para el desarrollo de este trabajo se aplicaron encuestas y entrevistas estratificadas a personas de la ruralidad del Azuay, para conocer de primera mano el proceso de elaboración del tocino artesanal; posteriormente se realizó un análisis comparativo de las características organolépticas de los dos productos. Finalmente se validó la propuesta ante un grupo extenso conformado por vendedores de expendios de comida típica del mercado 27 de febrero y expertos en el área gastronómica. Como resultado se evidencia la diferencia significativa en la mayoría de los atributos y se concluye con la preferencia del producto artesanal.

The involvement of the endocannabinoid system in drug addiction was initially studied by the use of compounds with different affinities for each cannabinoid receptor or for the proteins involved in endocannabinoids inactivation. The generation of genetically modified mice with selective mutations in these endocannabinoid system components has now provided important advances in establishing their specific contribution to drug addiction. These genetic tools have identified the particular interest of CB1 cannabinoid receptor and endogenous anandamide as potential targets for drug addiction treatment. Novel genetic tools will allow determining if the modulation of CB2 cannabinoid receptor activity and 2-arachidonoylglycerol tone can also have an important therapeutic relevance for drug addiction. ; This work was supported by the Spanish "Ministerio de Ciencia e Innovación" (#SAF2007-64062 and SAF2011-29864), "Instituto de Salud Carlos III" (RETICS- Red de Trastornos Adictivos-Redes Temáticas de Investigación Cooperativa en Salud: #RD06/0001/0001, #RD06/0001/1004), grants #10/00316 and #10/01708, Plan Nacional sobre Drogas (PNSD #2009/026), the Catalan Government (SGR2009-00131) and the ICREA Foundation (ICREA Academia-2008)

Repeated administration of 3,4-methylenedioxymethamphetamine (MDMA) produces dopaminergic neurotoxicity in mice. However, it is still not clear whether this exposure induces deficits in cognitive processing related to specific subsets of executive functioning. We evaluated the effects of neurotoxic and non-neurotoxic doses of MDMA (0, 3 and 30 mg/kg, twice daily for 4 days) on working memory and attentional set-shifting in mice, and changes in extracellular levels of dopamine (DA) in the striatum. Treatment with MDMA (30 mg/kg) disrupted performance of acquired operant alternation, and this impairment was still apparent 5 days after the last drug administration. Decreased alternation was not related to anhedonia because no differences were observed between groups in the saccharin preference test under similar experimental conditions. Correct responding on delayed alternation was increased 1 day after repeated treatment with MDMA (30 mg/kg), probably because of general behavioural quiescence. Notably, the high dose regimen of MDMA impaired attentional set-shifting related to an increase in total perseveration errors. Finally, basal extracellular levels of DA in the striatum were not modified in mice repeatedly treated with MDMA with respect to controls. However, an acute challenge with MDMA (10 mg/kg) failed to increase DA outflow in mice receiving the highest MDMA dose (30 mg/kg), corroborating a decrease in the functionality of DA transporters. Seven days after this treatment, the effects of MDMA on DA outflow were recovered. These results suggest that repeated neurotoxic doses of MDMA produce lasting impairments in recall of alternation behaviour and reduce cognitive flexibility in mice. ; This work was supported by the DG Research of the European Commission (PHECOMP: LHSM-CT-2007-037669), the Spanish 'Instituto de Salud Carlos III' (RD06/001/001 and PI070709), FEDER funds, and 'Ministerio de Ciencia e Innovación' (SAF2007-64062), the Catalan government (SGR2009-00131) and the ICREA Foundation (ICREA Academia-2008)

Hypocretins (also known as orexins) are hypothalamic neuropeptides involved in the regulation of sleep/wake states and feeding behavior. Recent studies have also demonstrated an important role for the hypocretin/orexin system in the addictive properties of drugs of abuse, consistent with the reciprocal innervations between hypocretin neurons and brain areas involved in reward processing. This system participates in the primary reinforcing effects of opioids, nicotine, and alcohol. Hypocretins are also involved in the neurobiological mechanisms underlying relapse to drug-seeking behavior induced by drug-related environmental stimuli and stress, as mainly described in the case of psychostimulants. Based on these preclinical studies, the use of selective ligands targeting hypocretin receptors could represent a new therapeutical strategy for the treatment of substance abuse disorders. In this review, we discuss and update the current knowledge about the participation of the hypocretin system in drug addiction and the possible neurobiological mechanisms involved in these processes regulated by hypocretin transmission. ; This work was supported by the Instituto de Salud Carlos III grants #PI07/0559,/n#PI10/00316, and #RD06/001/001 (RTA-RETICS), by the Spanish Ministry of Science/nand Technology (Consolider-C, #SAF2007-64062), the Catalan Government/n(SGR2009-00731), and by the Catalan Institution for Research and Advanced Studies/n(ICREA Academia program). A Plaza-Zabala is a recipient of a predoctoral fellowship/nfrom the Spanish Ministry of Education.

Injury to peripheral nerves often leads to abnormal pain states (hyperalgesia, allodynia and spontaneous pain), which can remain long after the injury heals. Although opioid agonists remain the gold standard for the treatment of moderate to severe pain, they show reduced efficacy against neuropathic pain. In addition to analgesia, opioid use is also associated with hyperalgesia and analgesia tolerance, whose underlying mechanisms share some commonalities with nerve injury-induced hypersensitivity. Here, we reviewed up-to-day research exploring the contribution of mu-opioid receptor (MOR) on the pathophysiology of neuropathic pain and on analgesic opioid actions under these conditions. We focused on the specific contributions of MOR populations at peripheral, spinal and supraspinal level. Moreover, evidences of neuroplastic changes that may underlie the low efficacy of MOR agonists under neuropathic pain conditions are reviewed and discussed. Sensitization processes leading to pain hypersensitivity, molecular changes in signalling pathways triggered by MOR and glial activation are some of these mechanisms elicited by both nerve injury and opioid exposure. Nerve injury-induced pain hypersensitivity might be masking the initial analgesic effects of opioid agonists, and alternatively, sustained opioid treatment to individuals already suffering from neuropathic pain could aggravate their pathophysiological state. Finally, some combined therapies that can increase opioid analgesic effectiveness in neuropathic pain treatment are highlighted. SIGNIFICANCE: This review provides evidence of the low benefit of opioid monotherapy in neuropathic pain and analyses the reasons of this reduced effectiveness. Opioid agonists along with drugs targeted to block the sensitization processes induced by MOR stimulation might result in a better management of neuropathic pain. ; We acknowledge the financial support of the European Commission FP7. Grant Number: #HEALTH‐F2‐2013‐602891; Spanish Ministry of Science, Innovation and Universities. Grant Number: #SAF2017‐84060‐R‐AEI/FEDER‐UE; Instituto de Salud Carlos III. Grant Number: RETICS/RTA #RD16/0017; Catalan Government AGAUR. Grant Numbers: #ICREA Acadèmia‐2015, #2017‐SGR‐669; Spanish MECD

The aim of the present study was to evaluate the possible involvement of GABAB receptors in nicotine-induced hypolocomotion and antinociceptive effects in mice. Animals were exposed to nicotine only once. Acute nicotine hydrogen tartrate salt (3mg/kg; subcutaneous, s.c.) administration induced hypolocomotion and antinociceptive responses in the tail-immersion and the hot-plate tests. The effects of pretreatment with either the GABAB receptor agonist baclofen (1, 2 and 3mg/kg; intraperitoneal, i.p.) or GABAB receptor antagonist 2-hydroxysaclofen (0.25, 0.5 and 1mg/kg; i.p.) were evaluated on these behavioral nicotine responses. The GABAB receptor agonist, baclofen (3mg/kg, i.p.) abolished nicotine-induced antinociceptive effects in the tail-immersion and the hot-plate tests, but did not modify nicotine-induced hypolocomotion. In addition, the GABAB receptor antagonist, 2-hydroxysaclofen (1mg/kg, i.p.) increased nicotine-induced antinociceptive effects in the tail-immersion and the hot-plate tests, and abolished nicotine-induced hypolocomotion. The present results shed light that the GABAB receptor has an important role in mediating specific acute nicotine responses such as hypolocomotion and antinociception in mice. ; This work has been supported by grants from University of Buenos Aires (UBACyT B016 and UBACyT 2013–2016 No. 20020120100244), CONICET (PIP 11420090100303), Spanish "Ministerio de Ciencia e Innovación" (#SAF2011-29864), "Instituto de Salud Carlos III" (RETICS: #RD06/0001/0001, #RD06/0001/1004), Plan Nacional sobre Drogas (PNSD #2009/026), the Catalan Government (SGR2009-00131) and the ICREA Foundation (ICREA Academia-2008)

The search for safe and efficient chronic pain treatments is dampened by the lack of reliable models that faithfully reproduce current pharmacological treatments for chronic spontaneous pain in humans. Preclinical models often assess the antinociceptive efficacy of non-contingent pharmacological treatments evaluated in the short-term. Here, we provide a protocol of contingent operant self-medication in mice, which allows the estimation of spontaneous pain relief and drug abuse liability in models of persistent pain. This paradigm requires preliminary habituation and animal handling, followed by training of mice in operant conditioning boxes, to allow subsequent analgesic drug self-administration. After the initial acquisition of food-maintained operant behavior, a chronic pain sensitization is induced. Posterior intravenous jugular catheterization and coupling of operant conditioning boxes to perfusion pumps allow quantification of operant responding for intravenous drug self-administration. All mice show an initial operant drug self-administration behavior associated with the previous food-maintained operant training. This initial operant responding is extinguished after administration of ineffective treatments, but continues when the compounds have analgesic efficacy or intrinsic reinforcing properties. The identification of a significant drug self-administration selectively expressed in mice exposed to the chronic pain condition is indicative of analgesic drug effects, whereas persistent self-administration in control mice is indicative of abuse liability. The present protocol provides the behavioral and surgical procedures needed to assess spontaneous pain relief and potential for abuse of pharmacological treatments, through contingent analgesic self-medication in mice. ; This work was supported by the European Comission [NeuroPain, FP7-602891-2], the European Union's Horizon 2020 research and innovation programme under grant agreement No 848068 [QSPainRelief, H2020-SC1-2019-2-RTD-848068], the Spanish Ministerio de Economía y Competitividad-MINECO (#SAF2017-84060-R- AEI/FEDER-UE), the Spanish Instituto de Salud Carlos III, RETICS-RTA (#RD12/0028/0023), the Generalitat de Catalunya, AGAUR (#2017 SGR-669), ICREA-Acadèmia (#2015) and the Spanish Ministerio de Sanidad, Servicios Sociales e Igualdad, Plan Nacional Sobre Drogas (#PNSD- 2017I068) to R.M., Fundació La Marató-TV3 (#2016/20-30) and Plan Nacional Sobre Drogas of the Spanish Ministry of Health (#PNSD-2019I006) to E.M-G. The methodology described was previously used in Bura et al. (2013, 2018) and Cabañero et al. (2020, doi:10.7554/eLife.55582). Authors also want to thank E. Senabre and R. Martín for their critics and technical support.

Emerging findings suggest the existence of a cross-talk between hypocretinergic and endocannabinoid systems. Although few studies have examined this relationship, the apparent overlap observed in the neuroanatomical distribution of both systems as well as their putative functions strongly point to the existence of such cross-modulation. In agreement, biochemical and functional studies have revealed the existence of heterodimers between CB1 cannabinoid receptor and hypocretin receptor-1, which modulates the cellular localization and downstream signaling of both receptors. Moreover, the activation of hypocretin receptor-1 stimulates the synthesis of 2-arachidonoyl glycerol culminating in the retrograde inhibition of neighboring cells and suggesting that endocannabinoids could contribute to some hypocretin effects. Pharmacological data indicate that endocannabinoids and hypocretins might have common physiological functions in the regulation of appetite, reward and analgesia. In contrast, these neuromodulatory systems seem to play antagonistic roles in the regulation of sleep/wake cycle and anxiety-like responses. The present review attempts to piece together what is known about this interesting interaction and describes its potential therapeutic implications. ; This work was supported by the Instituto de Salud CarlosIII grants, #PI07/0559, #PI10/00316 and #RD06/001/001 (RTA-RETICS), by the Spanish Ministry of Science and Technology, Consolider-C #SAF2007-64062 and #SAF2011-29864, the Catalan Government (SGR2009-00731), and by the Catalan Institution for Research and Advanced Studies (ICREA Academia program). África Flores is recipient of a predoctoral fellowship from the Spanish Ministry of Education

BACKGROUND: Cannabis is the most widely used illicit drug in the world. Although there is a high prevalence of users who seek treatment for cannabis dependence, no accepted pharmacologic treatment is available to facilitate and maintain abstinence. The hypocretin/orexin system plays a critical role in drug addiction, but the potential participation of this system in the addictive properties of cannabinoids is unknown. METHODS: We investigated the effects of hypocretins in the intravenous self-administration of the synthetic cannabinoid agonist WIN55,212-2 using hypocretin receptor-1 (Hcrtr-1) and hypocretin receptor-2 antagonists and Hcrtr-1 knockout mice. Additional groups of mice were trained to obtain water to rule out operant responding impairments. Activation of hypocretin neurons was analyzed by using double-label immunofluorescence of FosB/ΔFosB with hypocretin-1. Microdialysis studies were performed to evaluate dopamine extracellular levels in the nucleus accumbens after acute Δ(9)-tetrahydrocannabinol administration.RESULTS: Systemic administration of the Hcrtr-1 antagonist SB334867 reduced intravenous self-administration of WIN55,212-2, as well as the maximum effort to obtain a WIN55,212-2 infusion, as revealed under a progressive ratio schedule. This role of Hcrtr-1 in the reinforcing and motivational properties of WIN55,212-2 was confirmed in Hcrtr-1 knockout mice. Contingent, but not noncontingent, WIN55,212-2 self-administration increased the percentage of hypocretin cells expressing FosB/ΔFosB in the lateral hypothalamus. The enhancement in dopamine extracellular levels in the nucleus accumbens induced by Δ(9)-tetrahydrocannabinol was blocked in mice lacking the Hcrtr-1. CONCLUSIONS: /nThese findings demonstrate that Hcrtr-1 modulates the reinforcing properties of cannabinoids, which could have a clear therapeutic interest. ; This work was supported by the Instituto de Salud Carlos III grants, #PI07/0559, #PI10/00316 and #RD06/001/001 (RTA-RETICS), by the Spanish Ministry of Science and Technology, Consolider-C #SAF2007-64062 and #SAF2011-29864, the Catalan Government (SGR2009-00731), and by the Catalan Institution for Research and Advanced Studies (ICREA Academia program). África Flores is recipient of a predoctoral fellowship from the Spanish Ministry of Education

One aspect of the addictive process that has not been thoroughly investigated is the consequence of the frustrated state occurring when the drug is not available. The present study aimed to validate a novel operant model of frustrated expected reward in mice. C57BL/6J mice were trained in operant conditioning maintained by chocolate-flavoured pellets or cocaine. After the completion of high rates of responding on a progressive ratio schedule, the reward was unexpectedly withheld. The consequences of this frustrated behaviour on anxiety, aggressiveness, perseveration, extinction and reinstatement were investigated. Mice exposed to the frustrated event perseverated in the operant responses and showed increased aggressiveness in the resident-intruder test. These animals also showed higher rates of cue-induced reinstatement of drug seeking. The present study provides a reliable operant model in mice to evaluate a frustrated state following reward unavailability. This animal model could be useful to study the behavioural and neurochemical consequences related to the emotional states generated during the omission of a highly expected reward. ; This work was supported by the DG Research of the European Commission (PHECOMP, no. LHSM-CT-2007—037669 and GENADDICT, no. LSHM-CT-2004—05166), the Spanish 'Instituto de Salud Carlos III' (RTA, no. RD06/001/001), the Spanish 'Ministerio de Ciencia e Innovación' (no. SAF2007-64062), the Spanish 'Ministerio de Sanidad, Política Social e Igualdad' (Plan/nNacional Sobre Drogas, no. 2009/026), the Catalan Government (SGR2009-00131), the ICREA Foundation (ICREA Academia-2008). A.B. was supported by an FI pre-doctoral fellowship of the Catalan Government; J.G.-C. was supported by a 'Juan de la Cierva' postdoctoral fellowship from the Spanish 'Ministerio de Ciencia e Innovación'; and E.M.-G. was supported by a 'Sara Borrell' post-doctoral fellowship from the Spanish 'Instituto de Salud Carlos III'. Partial support from FEDER funds is also acknowledged

The pathophysiological mechanisms underlying depression are still poorly understood. An initial hypothesis postulated to explain the substrates of depression was based on the involvement of monoaminergic systems. This early theory was proposed from different findings obtained using pharmacological tools and can explain the mechanism of action of the drugs currently used to treat depression. However, more recent studies have revealed that other neurobiological processes different from monoamines also participate in the substrates of depression. These mechanisms include the participation of several neuromodulatory systems, stress-related circuits and neuroplastic changes that could represent a direct substrate for these pathophysiological processes. The lack of selective pharmacological tools for several of these potential targets of depression represents an important limitation to study their potential involvement. In the last two decades, different lines of genetically modified mice have been generated with selective deletions in specific genes related to the control of emotional responses. This review summarizes the main findings that have been obtained with these novel genetic tools to clarify the neurobiological substrates of depression. A particular focus has been devoted to the advances obtained with mice deficient in specific components of the monoaminergic, opioid and cannabinoid system and those with mutations in elements of the hypothalamic-pituitary-adrenal axis. ; This work was supported by the Spanish "Ministerio de Ciencia e Innovación" (#SAF2007-64062 and SAF2011-29864), "Instituto de Salud Carlos III" (RETICS-Red de Trastornos Adictivos-Redes Temáticas de Investigación Cooperativa en Salud: #RD06/0001/0001, #RD06/0001/1004), grants #10/00316 and #10/01708 to PR. Plan Nacional sobre Drogas (PNSD #2009/026), the Marató of TV3, the Catalan Government (SGR2009-00131) and the ICREA Foundation (ICREA Academia-2008)

Several lines of evidence support that food overconsumption may be related to the role of the endogenous opioid system in the control of food palatability. The opioid system, and particularly the delta opioid receptor (DOR), plays a crucial role in the regulation of food rewarding properties. In our study, we used operant conditioning maintained by chocolate-flavoured pellets to investigate the role of DOR in the motivation for palatable food and the structural plasticity changes promoted by this behaviour. For this purpose, we evaluated the specific role of this receptor in the behavioural and neuroplastic changes induced by palatable food in the prefrontal cortex (PFC), hippocampus (HCP) and nucleus accumbens (NAc) in constitutive knockout (KO) mice deficient in DOR. Mutant mice and their wild-type littermates were trained to obtain chocolate-flavoured pellets on fixed ratio 1 (FR1), FR5 and progressive ratio (PR) schedule of reinforcement. No significant differences between genotypes were revealed on operant behaviour acquisition in FR1. DOR knockout mice displayed lower number of active lever-presses than wild-type mice on FR5, and a similar decrease was revealed in DOR KO mice in the breaking point during the PR. This operant training to obtain palatable food increased dendritic spine density in the PFC, HCP and NAc shell of wild-type, but these plasticity changes were abolished in DOR KO mice. Our results support the hypothesis that DOR regulates the reinforcing effects and motivation for palatable food through neuroplastic changes in specific brain reward areas. ; This work was supported by the DG Research of the European Commission FP7 (#HEALTH-F2 2013-602891), the Spanish 'RETICS-Instituto de Salud Carlos III' (#RD12/0028/0023), the Spanish 'Ministerio de Ciencia e Innovación' (#SAF2011-29864), the Spanish 'Ministerio de Economia y Competitividad' (#SAF-2014-59648P), the 'Plan nacional sobre drogas' (#PNSD-2013-5068) and the Catalan Government 'AGAUR-Generalitat de Catalunya' (#2009SGR00731 and #2014-SGR-1547). The FEDER funds support is also acknowledged. S.M. was supported by FI predoctoral fellowship of the Catalan Government; S.M-N. was supported by CAPES fellowship of the Brazilian Government (Programa Ciência Sem Froteiras). We thank Elysia James for invaluable technical assistance in the structural plasticity study

BACKGROUND: Mu opioid receptors (MORs) are central to pain control, drug reward, and addictive behaviors, but underlying circuit mechanisms have been poorly explored by genetic approaches. Here we investigate the contribution of MORs expressed in gamma-aminobutyric acidergic forebrain neurons to major biological effects of opiates, and also challenge the canonical disinhibition model of opiate reward. METHODS: We used Dlx5/6-mediated recombination to create conditional Oprm1 mice in gamma-aminobutyric acidergic forebrain neurons. We characterized the genetic deletion by histology, electrophysiology, and microdialysis; probed neuronal activation by c-Fos immunohistochemistry and resting-state functional magnetic resonance imaging; and investigated main behavioral responses to opiates, including motivation to obtain heroin and palatable food. RESULTS: Mutant mice showed MOR transcript deletion mainly in the striatum. In the ventral tegmental area, local MOR activity was intact, and reduced activity was only observed at the level of striatonigral afferents. Heroin-induced neuronal activation was modified at both sites, and whole-brain functional networks were altered in live animals. Morphine analgesia was not altered, and neither was physical dependence to chronic morphine. In contrast, locomotor effects of heroin were abolished, and heroin-induced catalepsy was increased. Place preference to heroin was not modified, but remarkably, motivation to obtain heroin and palatable food was enhanced in operant self-administration procedures. CONCLUSIONS: Our study reveals dissociable MOR functions across mesocorticolimbic networks. Thus, beyond a well-established role in reward processing, operating at the level of local ventral tegmental area neurons, MORs also moderate motivation for appetitive stimuli within forebrain circuits that drive motivated behaviors. ; This work was supported by the Centre National de la Recherche Scientifique (BLK), Institut National de la Santé et de la Recherche Médicale (BK), Université de Strasbourg (BLK), Medical Research Council/Economic and Social Research Council interdisciplinary studentship (to HLK), the British Pharmacological Society (IK), the European Commission (Genaddict Grant No. LSHMCT2004-005166 to BLK), the U.S. National Institutes of Health (National Institute of Drug Addiction, Grant No. 05010 to BLK and National Institute on Alcohol Abuse and Alcoholism, Grant No. 16658 to BLK), the Canada Fund for Innovation, and the Canada Research Chairs (to BLK). Electrophysiological experiments were funded by the Intramural Programs of National Institute on Alcohol Abuse and Alcoholism and National Institute of Neurological Disorders and Stroke (Grant No. ZIA-AA000421 to VAA) and Japan Society for Promotion of Science (to AMats). Self-administration studies were supported by the Intramural Programs of National Institute on Alcohol Abuse and Alcoholism and National Institute of Neurological Disorders and Stroke (Grant No. ZIA-AA000421 to RM), the Directorate-General for Research of the European Commission Framework Programme 7 (Grant No. HEALTH-2013-602891 to RM), the Spanish Redes Temáticas de Investigación Cooperativa en Salud-Instituto de Salud Carlos III (Grant No. RD12/0028/0023 to RM), the Spanish Ministerio de Economia y Competitividad (Grant No. SAF-2014-59648P to RM), the Plan Nacional Sobre Drogas (Grant No. PNSD-2013-5068 to RM), and the Catalan Government Agència de Gestió d'Ajuts Universitaris i de Recerca (Grant No. 2014-SGR-1547 to RM) and Institució Catalana de Recerca i Estudis Avançats-Acadèmia (Grant No. 2015 to RM). Part of the work was supported by German Research Foundation Excellence Cluster EXC-1086 BrainLinks-BrainTools (to JH).