Dopamine D4 receptor counteracts morphine-induced changes in M opioid receptor signaling in the striosomes of the rat caudate putamen.

Morphine is one of the most potent analgesic drugs used to relieve moderate to severe pain. After long-term use of morphine, neuroadaptive changes in the brain promotes tolerance, which result in a reduced sensitivity to most of its effects with attenuation of analgesic efficacy, and dependence, revealed by drug craving and physical or psychological manifestations of drug withdrawal. The mu opioid receptor (MOR) is critical, not only in mediating morphine analgesia, but also in addictive behaviors by the induction of a strong rewarding effect. We have previously shown that dopamine D4 receptor (D4R) stimulation counteracts morphine-induced activation of dopaminergic nigrostriatal pathway and accumulation of Fos family transcription factors in the caudate putamen (CPu). In the present work, we have studied the effect of D4R activation on MOR changes induced by morphine in the rat CPu on a continuous drug treatment paradigm, by analyzing MOR protein level, pharmacological profile, and functional coupling to G proteins. Furthermore, using conditioned place preference and withdrawal syndrome test, we have investigated the role of D4R activation on morphine-related behavioural effects. MOR immunoreactivity, agonist binding density and its coupling to G proteins are up-regulated in the striosomes by continuous morphine treatment. Interestingly, co-treatment of morphine with the dopamine D4 receptor (D4R) agonist PD168,077 fully counteracts these adaptive changes in MOR, in spite of the fact that continuous PD168,077 treatment increases the [3H]DAMGO Bmax values to the same degree as seen after continuous morphine treatment. In addition, the administration of the D4R agonist counteracts the rewarding effects of morphine, as well as the development of physical dependence. The present results give support for the existence of antagonistic functional D4R-MOR receptor-receptor interactions in the adaptive changes occurring in MOR of striosomes on continuous administration of morphine and preventing morphine-related behaviour.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Dopamine D4 receptor activation counteracts nigrostriatal pathway activation by morphine: relevance in drug addiction.

Morphine induces dopamine release in the caudate putamen (CPu), which promotes stereotyped behavior and habit learning for drug-seeking and –taking. Nigrostriatal pathway stimulation by morphine is due to a removal of tonic inhibition arising from SNr GABA interneurons on SNc dopaminergic neurons through the mu opioid receptor (MOR). Long-term morphine exposure produces a series of adaptations in SNc dopamine neurons, which affect neuron excitability and dopamine output to CPu. We have previously shown that dopamine D4 receptor (D4R) stimulation counteracts acute and chronic morphine-induced accumulation of several transcription factors in the CPu (Gago et al., 2011 Brain Res.). Since D4R is expressed in the SNr (Rivera et al., Brain Res. 2003), we postulate that a functional D4R-MOR interaction at the midbrain level could exists. We have investigated the role of D4R in the morphine-induced nigroestriatal dopamine metabolism in the rat brain using biochemical and immunohistochemical techniques. We also have studied the influence of D4R on morphine-induced morphological changes in SNc dopamine neurons using both immunohistochemical and image analysis techniques. Finally, we examined a possible underlying mechanism of the D4R-MOR interaction at the SN level using in vitro quantitative receptor autoradiography. We have found that D4R activation restores dopamine metabolism in the nigroestriatal pathway after acute morphine treatment and prevents morphine-induced rise of tyroxine hydroxylase and dopamine transporter. Rats receiving a continuous treatment of morphine (6 days) showed SNc dopamine neurons with smaller size and higher circularity index compared with the controls animals. These morphine-induced morphological adaptatives changes were prevented when a D4R agonist (PD168,077) was administered at the same time with morphine. Autoradiographic studies demonstrated that the D4R agonist reduce the affinity of MOR. The present study provides evidence for the existence of a fully blocking effect of the D4R on the activation of dopaminergic nigroestriatal pathway by morphine.Financiación: P09-CVI- 4702 (Proyecto de Excelencia de la Junta de Andalucía

The G protein-coupled receptor heterodimer network (GPCR-HetNet) and its hub components

G protein-coupled receptors (GPCRs) oligomerization has emerged as a vital characteristic of receptor structure. Substantial experimental evidence supports the existence of GPCR-GPCR interactions in a coordinated and cooperative manner. However, despite the current development of experimental techniques for large-scale detection of GPCR heteromers, in order to understand their connectivity it is necessary to develop novel tools to study the global heteroreceptor networks. To provide insight into the overall topology of the GPCR heteromers and identify key players, a collective interaction network was constructed. Experimental interaction data for each of the individual human GPCR protomers was obtained manually from the STRING and SCOPUS databases. The interaction data were used to build and analyze the network using Cytoscape software. The network was treated as undirected throughout the study. It is comprised of 156 nodes, 260 edges and has a scale-free topology. Connectivity analysis reveals a significant dominance of intrafamily versus interfamily connections. Most of the receptors within the network are linked to each other by a small number of edges. DRD2, OPRM, ADRB2, AA2AR, AA1R, OPRK, OPRD and GHSR are identified as hubs. In a network representation 10 modules/clusters also appear as a highly interconnected group of nodes. Information on this GPCR network can improve our understanding of molecular integration. GPCR-HetNet has been implemented in Java and is freely available at http://www.iiia.csic.es/similar to ismel/GPCR-Nets/index.html

Dopamine D-4 receptor counteracts morphine-induced changes in µ opioid receptor signaling in the striosomes of the rat caudate putamen

The mu opioid receptor (MOR) is critical in mediating morphine analgesia. However, prolonged exposure to morphine induces adaptive changes in this receptor leading to the development of tolerance and addiction. In the present work we have studied whether the continuous administration of morphine induces changes in MOR protein levels, its pharmacological profile, and MOR-mediated G-protein activation in the striosomal compartment of the rat CPu, by using immunohistochemistry and receptor and DAMGO-stimulated [S-35]GTP gamma S autoradiography. MOR immunoreactivity, agonist binding density and its coupling to G proteins are up-regulated in the striosomes by continuous morphine treatment in the absence of changes in enkephalin and dynorphin mRNA levels. In addition, co-treatment of morphine with the dopamine D-4 receptor (D4R) agonist PD168,077 fully counteracts these adaptive changes in MOR, in spite of the fact that continuous PD168,077 treatment increases the [H-3]DAMGO B-max values to the same degree as seen after continuous morphine treatment. Thus, in spite of the fact that both receptors can be coupled to G(i/0) protein, the present results give support for the existence of antagonistic functional D4R-MOR receptor-receptor interactions in the adaptive changes occurring in MOR of striosomes on continuous administration of morphine

Dopamine D4 Receptor Counteracts Morphine-Induced Changes in µ Opioid Receptor Signaling in the Striosomes of the Rat Caudate Putamen

The mu opioid receptor (MOR) is critical in mediating morphine analgesia. However, prolonged exposure to morphine induces adaptive changes in this receptor leading to the development of tolerance and addiction. In the present work we have studied whether the continuous administration of morphine induces changes in MOR protein levels, its pharmacological profile, and MOR-mediated G-protein activation in the striosomal compartment of the rat CPu, by using immunohistochemistry and receptor and DAMGO-stimulated [35S]GTPγS autoradiography. MOR immunoreactivity, agonist binding density and its coupling to G proteins are up-regulated in the striosomes by continuous morphine treatment in the absence of changes in enkephalin and dynorphin mRNA levels. In addition, co-treatment of morphine with the dopamine D4 receptor (D4R) agonist PD168,077 fully counteracts these adaptive changes in MOR, in spite of the fact that continuous PD168,077 treatment increases the [3H]DAMGO Bmax values to the same degree as seen after continuous morphine treatment. Thus, in spite of the fact that both receptors can be coupled to Gi/0 protein, the present results give support for the existence of antagonistic functional D4R-MOR receptor-receptor interactions in the adaptive changes occurring in MOR of striosomes on continuous administration of morphine

Finite element model simulations to assist the design of microdevices dedicated to the localized electroporation of mouse embryos

We have recently developed a microsystem to electroporate a few cells at the surface of early post-implantation mouse embryos. We could achieve the efficient, reproducible, and safe transfection of various genetic markers, which allowed single cell fate studies during morphogenesis. However, our single-use polymeric device necessitated to be fabricated in a clean room the day before each experiment. Thus, we here introduce an all-glass chip that any biologist can easily recycle in its laboratory. Most importantly, during the technological evolution process we could validate a comprehensive design strategy based on finite element model simulations. Indeed, both the embryo and the microsystem were represented as very simple electric objects and stationary computations enabled to properly predict the voltage pulse amplitude that would yield optimal device performances.SCOPUS: cp.pinfo:eu-repo/semantics/publishe