In vivo neuronal co-expression of mu and delta opioid receptors uncovers new therapeutic perspectives

Opioid receptors are G protein coupled receptors that modulate brain function at all levels of neural integration, including autonomous, sensory, emotional and cognitive processing. Mu and delta opioid receptors functionally interact in vivo, but whether interactions occur at circuitry, cellular or molecular level remains unsolved. Also, the notion of receptor crosstalk via mu-delta heteromers is well documented in vitro but in vivo evidence remains scarce. To identify neurons in which receptor interactions could take place, we designed a unique double mutant knock-in mouse line that expresses functional red-fluorescent mu receptors and green-fluorescent delta receptors. We mapped mu and delta receptor distribution and co-localization throughout the nervous system and created the first interactive brain atlas with concomitant mu-delta visualization at subcellular resolution (http://mordor.ics-mci.fr/). Mu and delta receptors co-localize in neurons from subcortical networks but are mainly detected in separate neurons in the forebrain. Also, co-immunoprecipitation experiments indicated physical proximity in the hippocampus, a prerequisite to mu-delta heteromerization. Altogether, data suggest that mu-delta functional interactions take place at systems level for high-order emotional and cognitive processing whereas mu-delta may interact at cellular level in brain networks essential for survival, which has potential implications for innovative drug design in pain control, drug addiction and eating disorders

Brain Struct Funct

Opioid receptors are G protein-coupled receptors (GPCRs) that modulate brain function at all levels of neural integration, including autonomic, sensory, emotional and cognitive processing. Mu (MOR) and delta (DOR) opioid receptors functionally interact in vivo, but whether interactions occur at circuitry, cellular or molecular levels remains unsolved. To challenge the hypothesis of MOR/DOR heteromerization in the brain, we generated redMOR/greenDOR double knock-in mice and report dual receptor mapping throughout the nervous system. Data are organized as an interactive database offering an opioid receptor atlas with concomitant MOR/DOR visualization at subcellular resolution, accessible online. We also provide co-immunoprecipitation-based evidence for receptor heteromerization in these mice. In the forebrain, MOR and DOR are mainly detected in separate neurons, suggesting system-level interactions in high-order processing. In contrast, neuronal co-localization is detected in subcortical networks essential for survival involved in eating and sexual behaviors or perception and response to aversive stimuli. In addition, potential MOR/DOR intracellular interactions within the nociceptive pathway offer novel therapeutic perspectives

Voie parabrachio-amygdaloïde (Implication du brain-derived neutrophic factor (BDNF) dans la réponse à la morphine)

La partie centrale de l amygdale étendue (AEc) est associée à la modulation des états émotionnels dans de nombreuses situations physiologiques et pathologiques telles que l anxiété, la peur, la dépendance aux drogues, ainsi qu à différentes manifestations des états douloureux. L AEc reçoit des afférences issues du noyau parabrachial (PB). Celui-ci est un centre intégrateur majeur des informations viscéro- et somato-sensorielles exprimant de nombreux neuropeptides et leurs récepteurs. Ainsi, la morphine exogène agit sur les récepteurs de type mu dont la présence en forte densité a été démontrée dans la région externe du PB latéral (PBel). Le PBel présente également une concentration importante de neurones exprimant le Brain Derived Neurotrophic Factor (BDNF). Cette neurotrophine joue un rôle majeur dans le développement et la régénération du système nerveux et est également connue pour intervenir dans les mécanismes de plasticité synaptique. Nous avons posé l'hypothèse que le BDNF pourrait être un élément important de la voie parabrachio-amygdaloïde, élargie à l ensemble de l AEc. Nous avons évalué son implication dans l analgésie morphinique et dans la dépendance aux opiacés. L injection d acide iboténique ou la délétion locale du BDNF dans le PBel diminue l expression des symptômes physiques de sevrage de la morphine et réduit significativement l analgésie morphinique. Par contre, les sensibilités nociceptives basales des animaux ne sont pas affectées, tout comme leur niveau d anxiété ou leurs capacités motrices. Enfin, l induction du facteur de transcription c-Fos par la morphine aiguë ou par le sevrage précipité de la morphine est réduite dans l AEc des animaux ayant subit une délétion du BDNF. L ensemble de nos résultats associés à ceux de la littérature suggèrent l'existence d'une interaction entre les récepteurs des opioïdes et le BDNF au sein de la voie parabrachio-AEc.Central part of extended amygdala (EAc) is associated to emotional states modulation in a number of physiological or pathological situations such as anxiety, fear, addiction or pain-related behaviors. EAc receives afferences from the parabrachial nucleus (PB) which is a major integrative center for viscero- and somato-sensory information. Numerous neuropeptides and associated receptors are expressed in the PB. In particular, exogenous morphine acts through mu opioid receptors found in high density in PB external lateral part (PBel). This region also displays a large concentration of Brain-Derived Neurotrophic Factor (BDNF) expressing neurons. This neurotrophine plays a critical role in development and nervous system regeneration but it is also known for its implication in synaptic plasticity mechanisms. We hypothesized that BDNF could be a critical element of the parabrachio-amygdaloid pathway, extended to the whole EAc pathway. We have thus assessed its implication in morphine analgesia and opiates addiction. Ibotenic acid injection or local specific BDNF gene deletion in the PBel reduces the expression of naloxone-precipitated morphine withdrawal-induced physical symptoms and significatively reduces morphine-induced analgesia without affecting tolerance phenomena associated with repetitive morphine injection. However, basal nociceptive sensibilities of animals were not affected and no influence on their anxiety level or motor capacities was observed. Moreover, the induction of transcription factor c-Fos by acute morphine or by naloxone-precipitated morphine withdrawal is reduced in EAc of BDNF-deleted mice. Our results, associated to the data from the literature, suggest an interaction between mu opioid receptors and BDNF in the parabrachio-EAc pathway.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

In vivo neuronal co-expression of mu and delta opioid receptors uncovers new therapeutic perspectives

Opioid receptors are G protein coupled receptors that modulate brain function at all levels of neural integration, including autonomous, sensory, emotional and cognitive processing. Mu and delta opioid receptors functionally interact in vivo, but whether interactions occur at circuitry, cellular or molecular level remains unsolved. Also, the notion of receptor crosstalk via mu-delta heteromers is well documented in vitro but in vivo evidence remains scarce. To identify neurons in which receptor interactions could take place, we designed a unique double mutant knock-in mouse line that expresses functional red-fluorescent mu receptors and green-fluorescent delta receptors. We mapped mu and delta receptor distribution and co-localization throughout the nervous system and created the first interactive brain atlas with concomitant mu-delta visualization at subcellular resolution (http://mordor.ics-mci.fr/). Mu and delta receptors co-localize in neurons from subcortical networks but are mainly detected in separate neurons in the forebrain. Also, co-immunoprecipitation experiments indicated physical proximity in the hippocampus, a prerequisite to mu-delta heteromerization. Altogether, data suggest that mu-delta functional interactions take place at systems level for high-order emotional and cognitive processing whereas mu-delta may interact at cellular level in brain networks essential for survival, which has potential implications for innovative drug design in pain control, drug addiction and eating disorders

Vasopressin and oxytocin excite distinct neuronal populations in the central amygdala

Vasopressin and oxytocin strongly modulate autonomic fear responses, through mechanisms that are still unclear. We describe how these neuropeptides excite distinct neuronal populations in the central amygdala, which provides the major output of the amygdaloid complex to the autonomic nervous system. We identified these two neuronal populations as part of an inhibitory network, through which vasopressin and oxytocin modulate the integration of excitatory information from the basolateral amygdala and cerebral cortex in opposite manners. Through this network, the expression and endogenous activation of vasopressin and oxytocin receptors may regulate the autonomic expression of fear

Efferents of anterior cingulate areas 24a and 24b and midcingulate areas 24aʹ and 24bʹ in the mouse

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In vivo neuronal co-expression of mu and delta opioid receptors uncovers new therapeutic perspectives.

Opioid receptors belong to the G protein coupled receptor family. They modulate brain function at all levels of neural integration and therefore impact on autonomous, sensory, emotional and cognitive processing. In vivo functional interaction between mu and delta opioid receptors are known to take place though it is still debated whether interactions occur at circuitry, cellular or molecular level. Also, the notion of receptor crosstalk via mu-delta heteromers is well documented in vitro but in vivo evidence remains scarce. To identify neurons in which receptor interactions could take place, we designed a unique double mutant knock-in mouse line that expresses functional red-fluorescent mu receptors and green-fluorescent delta receptors. We mapped mu and delta receptor distribution and co-localization throughout the nervous system and created the first interactive brain atlas with concomitant mu-delta visualization at subcellular resolution (http://mordor.ics-mci.fr/). Mu and delta receptors co-localize in neurons from subcortical networks but are mainly detected in separate neurons in the forebrain. Also, co-immunoprecipitation experiments indicated physical proximity in the hippocampus, a prerequisite to mu-delta heteromerization. Altogether, data suggest that mu-delta functional interactions take place at systems level for high-order emotional and cognitive processing whereas mu-delta may interact at cellular level in brain networks essential for survival, which has potential implications for innovative drug design in pain control, drug addiction and eating disorders

Neuronal circuits underlying acute morphine action on dopamine neurons.

International audienceMorphine is a highly potent analgesic with high addictive potential in specific contexts. Although dopamine neurons of the ventral tegmental area (VTA) are widely believed to play an essential role in the development of drug addiction, neuronal circuits underlying morphine action on dopamine neurons have not been fully elucidated. Here we combined in vivo electrophysiology, tract-tracing experiments, and targeted neuronal inactivation to dissect a neural circuit for acute morphine action on dopamine neurons in rats. We found that in vivo, morphine targets the GABAergic tail of the VTA, also called the rostromedial tegmental nucleus, to increase the firing of dopamine neurons through the activation of VTA μ opioid receptors expressed on tail of the VTA/rostromedial tegmental nucleus efferents. Our data also reveal that in the absence of VTA glutamatergic tone, there is no morphine-induced activation of dopamine neurons. These results define the anatomical organization and functional role of a neural circuit for acute morphine action on dopamine neurons