Role of the endocannabinoid system in the control of the cerebellar functions

The endocannabinoid system is an endogenous neuromodulatory system widely expressed in the central nervous system. It modulates synaptic plasticity and neuronal excitability, and fine-tunes several physiological functions such as, motor coordination, learning and memory, anxiety and nociception, among others. Exogenous or endogenous cannabinoid agonists exert their effects acting on specific cannabinoid receptors heavily expressed in the brain. Cannabinoids agonists are widely used and abused for recreational purposes, but more recently their therapeutic potential in different pathological states has been explored. Important limitations to their use are the possible central adverse effects on cognitive performance or motor coordination. This thesis mainly focuses on the effects of Δ9-tetrahydrocannabinol, the main psychoactive compound of marijuana plant, in the cerebellar functionality, paying special attention to the role of the microglial cells in the regulation of the fine motor coordination functions. The use of biochemical, pharmacological, genetic, and behavioral approaches allowed us to determine the sensitivity of the neuronal/glial circuitry in the regulation of the cerebellar functions and the molecular mechanisms they involved in it.El sistema endocannabinoid és un sistema endogen neuromodulador àmpliament expressat en el sistema nerviós central. Aquest sistema modula la plasticitat sinàptica i l’excitabilitat neuronal, regulant de manera fina funcions fisiològiques com la coordinació motora, l’aprenentatge, la memòria, l’ansietat i el dolor, entre d’altres. Agonistes cannabinoids exògens o endògens duen a terme els seus efectes actuant específicament sobre els receptors cannabinoids àmpliament expressats en el cervell. Els compostos cannabinoids són extensament utilitzats pel seu ús recreatiu com a drogues d’abús, encara que en els últims anys el seu potencial terapèutic està sent cada cop més estudiat. Una de les principals limitacions del seu ús són els possibles efectes adversos sobre el sistema nerviós central, a nivell cognitiu i sobre la coordinació motora. Aquesta tesis es centra principalment en els efectes del Δ9-tetrahidrocannabinol, el principal component psicoactiu de la planta de la marihuana, sobre la coordinació motora fina. La combinació d’aproximacions bioquímiques, farmacològiques, genètiques i comportamentals ha permès determinar la sensibilitat del circuit glial/neuronal en el control de les funcions cerebelars i els mecanismes i molècules involucrades en aquesta regulaci

Anatomical and molecular characterization of dopamine D1 receptor-expressing neurons of the mouse CA1 dorsal hippocampus

International audienceIn the hippocampus, a functional role of dopa-mine D1 receptors (D1R) in synaptic plasticity and memory processes has been suggested by electrophysiological and pharmacological studies. However, comprehension of their function remains elusive due to the lack of knowledge on the precise localization of D1R expression among the diversity of interneuron populations. Using BAC trans-genic mice expressing enhanced green fluorescent protein under the control of D1R promoter, we examined the molecular identity of D1R-containing neurons within the CA1 subfield of the dorsal hippocampus. In agreement with previous findings, our analysis revealed that these neurons are essentially GABAergic interneurons, which express several neurochemical markers, including calcium-binding proteins, neuropeptides, and receptors among others. Finally, by using different tools comprising cell type-specific isolation of mRNAs bound to tagged-ribosomes, we provide solid data indicating that D1R is present in a large proportion of interneurons expressing dopamine D2 receptors. Altogether, our study indicates that D1Rs are expressed by different classes of interneurons in all layers examined and not by pyramidal cells, suggesting that CA1 D1R mostly acts via modulation of GABAergic interneurons

Psychostimulant Drugs Activate Cell-type Specific and Topographic cFos Expression in the Lumbar Spinal Cord

International audiencePsychostimulant drugs, such as cocaine, d-amphetamine and methylphenidate, alter a wide range of behaviors including locomotor activity and somatosensory perception. These altered behaviors are accompanied by the activation of specific neuronal populations within reward-, emotion- and locomotion-related circuits. However, whether such regulation occurs at the level of the spinal cord, a key node for neural circuits integrating and coordinating sensory and motor functions has never been addressed. By evaluating the temporal and spatial expression pattern of the phosphorylated form of the immediate early gene cFos at Ser32 (pS32-cFos), used as a proxy of neuronal activation, we demonstrate that, in adult male mice, d-amphetamine increases pS32-cFos expression in both inhibitory and excitatory neurons in dorsal and ventral horns at the lumbar spinal cord level. Interestingly, a fraction of neurons activated by a first exposure to d-amphetamine can be re-activated following d-amphetamine re-exposure. Similar expression patterns were observed in response to cocaine and methylphenidate, but not following morphine and dozilcipine administration. Finally, the blockade of dopamine reuptake was sufficient to recapitulate the increase in pS32-cFos expression induced by psychostimulant drugs. Our work provides evidence that cFos expression can be activated in lumbar spinal cord in response to acute psychostimulants administration. Running title: Psychostimulant-evoked neuronal ensembles in spinal cord

Operant behavior to obtain palatable food modifies ERK activity in the brain reward circuit

Food palatability produces behavioral modifications that resemble those induced by drugs of abuse. Palatability-induced behavioral changes require both, the activation of the endogenous cannabinoid system, and changes in structural plasticity in neurons of the brain reward pathway. The ERK intracellular pathway is activated by CB1 receptors (CB1-R) and plays a crucial role in neuroplasticity. We investigated the activation of the ERK signaling cascade in the mesocorticolimbic system induced by operant training to obtain highly palatable isocaloric food and the involvement of the CB1-R in these responses. Using immunofluorescence techniques, we analyzed changes in ERK intracellular pathway activation in the mesocorticolimbic system of wild-type and CB1 knockout mice (CB1-/-) trained on an operant paradigm to obtain standard, highly caloric or highly palatable isocaloric food. Operant training for highly palatable isocaloric food, but not for standard or highly caloric food, produced a robust activation of the ERK signaling cascade in the same brain areas where this training modified structural plasticity. These changes induced by the operant training were absent in CB1-/-. We can conclude that the activation of the ERK pathway is associated to the neuroplasticity induced by operant training for highly palatable isocaloric food and might be involved in CB1-R mediated alterations in behavior and structural plasticity.This work was supported by the Spanish “Ministerio de Ciencia e Innovación” (#SAF2007-64062 and #SAF2008-00962), “Instituto de Salud Carlos III” (#RD06/001/001), “Plan Nacional sobre Drogas, the Catalan Government” (SGR2009-00131 and SGR 2009-224), the “ICREA Foundation” (ICREA Academia-2008), the “DG Research of the European Commission” (GENADDICT, #LSHM-CT-2004-05166; and PHECOMP, #LSHM-CT-2007-037669) the “FIS” (PI07/0715), “ATIP-Avenir” and “Sanofi-Aventis” grants. This work was also supported by the “Plan Nacional Sobre Drogas” (#2009/026) to R.

Cerebellar dopamine D2 receptors regulate social behaviors

International audienceThe cerebellum, a primary brain structure involved in the control of sensorimotor tasks, also contributes to higher cognitive functions including reward, emotion and social interaction. Although the regulation of these behaviors has been largely ascribed to the monoaminergic system in limbic regions, the contribution of cerebellar dopamine signaling in the modulation of these functions remains largely unknown. By combining cell-type-specific transcriptomics, histological analyses, three-dimensional imaging and patch-clamp recordings, we demonstrate that cerebellar dopamine D2 receptors (D2Rs) in mice are preferentially expressed in Purkinje cells (PCs) and regulate synaptic efficacy onto PCs. Moreover, we found that changes in D2R levels in PCs of male mice during adulthood alter sociability and preference for social novelty without affecting motor functions. Altogether, these findings demonstrate novel roles for D2R in PC function and causally link cerebellar D2R levels of expression to social behaviors

Operant behavior to obtain palatable food modifies neuronal plasticity in the brain reward circuit

Palatability enhances food intake by hedonic mechanisms that prevail over caloric necessities. Different studies have demonstrated the role of endogenous cannabinoids in the mesocorticolimbic system in controlling food hedonic value and consumption. We hypothesize that the endogenous cannabinoid system could also be involved in the development of food-induced behavioral alterations, such as food-seeking and binge-eating, by a mechanism that requires neuroplastic changes in the brain reward pathway. For this purpose, we evaluated the role of the CB1 cannabinoid receptor (CB1-R) in the behavioral and neuroplastic changes induced by operant training for standard, highly caloric or highly palatable isocaloric food using different genetics, viral and pharmacological approaches. Neuroplasticity was evaluated by measuring changes in dendritic spine density in neurons previously labeled with the dye DiI. Only operant training to obtain highly palatable isocaloric food induced neuroplastic changes in neurons of the nucleus accumbens shell and prefrontal cortex that were associated to changes in food-seeking behavior. These behavioral and neuroplastic modifications induced by highly palatable isocaloric food were dependent on the activity of the CB1-R. Neuroplastic changes induced by highly palatable isocaloric food are similar to those produced by some drugs of abuse and may be crucial in the alteration of food-seeking behavior leading to overweight and obesity.This work was supported by the Spanish Ministerio de Ciencia e Innovació (#SAF2007-64062 and #SAF2008-00962), the Instituto de Salud CarlosIII (#RD06/001/001), the Plan Nacional sobre Drogas, the Catalan Government (SGR2009-00131 and SGR2009-224), the ICREA Foundation (ICREA Academia-2008), the DG Research of the European Commission (GENADDICT,/n#LSHM-CT-2004-05166; and PHECOMP, #LSHM-CT-2007-037669) the FIS’’ (PI07/0715),ATIP-Avenir and Sanofi-Aventis grants.This work was also supported by the Plan Nacional Sobre Drogas (#2009/026) to R.M

Peripheral and central CB1 cannabinoid receptors control stress-induced impairment of memory consolidation

Stressful events can generate emotional memories linked to the traumatic incident, but they also can impair the formation of nonemotional memories. Although the impact of stress on emotional memories is well studied, much less is known about the influence of the emotional state on the formation of nonemotional memories. We used the novel object-recognition task as a model of nonemotional memory in mice to investigate the underlying mechanism of the deleterious effect of stress on memory consolidation. Systemic, hippocampal, and peripheral blockade of cannabinoid type-1 (CB1) receptors abolished the stress-induced memory impairment. Genetic deletion and rescue of CB1 receptors in specific cell types revealed that the CB1 receptor population specifically in dopamine β-hydroxylase (DBH)-expressing cells is both necessary and sufficient for stress-induced impairment of memory consolidation, but CB1 receptors present in other neuronal populations are not involved. Strikingly, pharmacological manipulations in mice expressing CB1 receptors exclusively in DBH(+) cells revealed that both hippocampal and peripheral receptors mediate the impact of stress on memory consolidation. Thus, CB1 receptors on adrenergic and noradrenergic cells provide previously unrecognized cross-talk between central and peripheral mechanisms in the stress-dependent regulation of nonemotional memory consolidation, suggesting new potential avenues for the treatment of cognitive aspects on stress-related disorders.We acknowledge a predoctoral fellowship from the Spanish Ministry of Education and a postdoctoral fellowship from the Investments for the Future Programme, Initiative of Excellence Bordeaux, ANR-10-IDEX-03-02 (to A.B.-G.); a postdoctoral fellowship from the Marie Curie action Seventh Framework Programme for Research and Technological Development, FP7-PEOPLE-2013 (to A.B.-G.); the partial support by FRAXA Research Foundation (M.G.-G.); a European Molecular Biology Organization postdoctoral fellowship (to L. Bellocchio); grants from Ministerio de Ciencia e Innovación [BFU2012-33500 and BFU2015-68568P (to A.O.), and SAF2014-59648-P (to R.M.) (MINECO/FEDER, UE)]; Instituto de Salud Carlos III Grant RD06/0001/0001 (to R.M.); Generalitat de Catalunya Grant SGR-2014-1547 (to R.M.); ICREA (Institució Catalana de Recerca i Estudis Avançats) Academia (R.M.); the German Research Council DFG Grants FOR926 (Core Unit Endocannabinoid Measurements) (to B.L.), CRC-TRR58 (to B.L.), and CRC1080 (to B.L.); EU-FP7 Grant REPROBESITY, HEALTH-F2-2008-223713 (to B.L. and G.M.); PainCage Grant HEALTH-2013-INNOVATION-1-603191 (to G.M.); INSERM (G.M.); European Research Council Grant ENDOFOOD, ERC–2010–StG–260515 (to G.M.); Fondation pour la Recherche Medicale (G.M.); Region Aquitaine (G.M.); and LABEX BRAIN Grant ANR-10-LABX-43 (to G.M.

Operant behavior to obtain palatable food modifies ERK activity in the brain reward circuit

Food palatability produces behavioral modifications that resemble those induced by drugs of abuse. Palatability-induced behavioral changes require both, the activation of the endogenous cannabinoid system, and changes in structural plasticity in neurons of the brain reward pathway. The ERK intracellular pathway is activated by CB1 receptors (CB1-R) and plays a crucial role in neuroplasticity. We investigated the activation of the ERK signaling cascade in the mesocorticolimbic system induced by operant training to obtain highly palatable isocaloric food and the involvement of the CB1-R in these responses. Using immunofluorescence techniques, we analyzed changes in ERK intracellular pathway activation in the mesocorticolimbic system of wild-type and CB1 knockout mice (CB1-/-) trained on an operant paradigm to obtain standard, highly caloric or highly palatable isocaloric food. Operant training for highly palatable isocaloric food, but not for standard or highly caloric food, produced a robust activation of the ERK signaling cascade in the same brain areas where this training modified structural plasticity. These changes induced by the operant training were absent in CB1-/-. We can conclude that the activation of the ERK pathway is associated to the neuroplasticity induced by operant training for highly palatable isocaloric food and might be involved in CB1-R mediated alterations in behavior and structural plasticity.This work was supported by the Spanish “Ministerio de Ciencia e Innovación” (#SAF2007-64062 and #SAF2008-00962), “Instituto de Salud Carlos III” (#RD06/001/001), “Plan Nacional sobre Drogas, the Catalan Government” (SGR2009-00131 and SGR 2009-224), the “ICREA Foundation” (ICREA Academia-2008), the “DG Research of the European Commission” (GENADDICT, #LSHM-CT-2004-05166; and PHECOMP, #LSHM-CT-2007-037669) the “FIS” (PI07/0715), “ATIP-Avenir” and “Sanofi-Aventis” grants. This work was also supported by the “Plan Nacional Sobre Drogas” (#2009/026) to R.

Operant behavior to obtain palatable food modifies neuronal plasticity in the brain reward circuit

Palatability enhances food intake by hedonic mechanisms that prevail over caloric necessities. Different studies have demonstrated the role of endogenous cannabinoids in the mesocorticolimbic system in controlling food hedonic value and consumption. We hypothesize that the endogenous cannabinoid system could also be involved in the development of food-induced behavioral alterations, such as food-seeking and binge-eating, by a mechanism that requires neuroplastic changes in the brain reward pathway. For this purpose, we evaluated the role of the CB1 cannabinoid receptor (CB1-R) in the behavioral and neuroplastic changes induced by operant training for standard, highly caloric or highly palatable isocaloric food using different genetics, viral and pharmacological approaches. Neuroplasticity was evaluated by measuring changes in dendritic spine density in neurons previously labeled with the dye DiI. Only operant training to obtain highly palatable isocaloric food induced neuroplastic changes in neurons of the nucleus accumbens shell and prefrontal cortex that were associated to changes in food-seeking behavior. These behavioral and neuroplastic modifications induced by highly palatable isocaloric food were dependent on the activity of the CB1-R. Neuroplastic changes induced by highly palatable isocaloric food are similar to those produced by some drugs of abuse and may be crucial in the alteration of food-seeking behavior leading to overweight and obesity.This work was supported by the Spanish Ministerio de Ciencia e Innovació (#SAF2007-64062 and #SAF2008-00962), the Instituto de Salud CarlosIII (#RD06/001/001), the Plan Nacional sobre Drogas, the Catalan Government (SGR2009-00131 and SGR2009-224), the ICREA Foundation (ICREA Academia-2008), the DG Research of the European Commission (GENADDICT,/n#LSHM-CT-2004-05166; and PHECOMP, #LSHM-CT-2007-037669) the FIS’’ (PI07/0715),ATIP-Avenir and Sanofi-Aventis grants.This work was also supported by the Plan Nacional Sobre Drogas (#2009/026) to R.M

Ribosomal Protein S6 Phosphorylation Is Involved in Novelty-Induced Locomotion, Synaptic Plasticity and mRNA Translation

The phosphorylation of the ribosomal protein S6 (rpS6) is widely used to track neuronal activity. Although it is generally assumed that rpS6 phosphorylation has a stimulatory effect on global protein synthesis in neurons, its exact biological function remains unknown. By using a phospho-deficient rpS6 knockin mouse model, we directly tested the role of phospho-rpS6 in mRNA translation, plasticity and behavior. The analysis of multiple brain areas shows for the first time that, in neurons, phospho-rpS6 is dispensable for overall protein synthesis. Instead, we found that phospho-rpS6 controls the translation of a subset of mRNAs in a specific brain region, the nucleus accumbens (Acb), but not in the dorsal striatum. We further show that rpS6 phospho-mutant mice display altered long-term potentiation (LTP) in the Acb and enhanced novelty-induced locomotion. Collectively, our findings suggest a previously unappreciated role of phospho-rpS6 in the physiology of the Acb, through the translation of a selective subclass of mRNAs, rather than the regulation of general protein synthesis