Mu Opioid Receptor from the Zebrafish Exhibits Functional Characteristics as Those of Mammalian Mu Opioid Receptor

Abstract

The functional characterization of the mu opioid receptor from the zebrafish (zfMOR) is reported here. After transfection in HEK-293 cell line, using both peptidergic and nonpeptidergic opioid ligands in the competition and saturation-binding experiments, in addition to the functional assays of (35)S-GTPgammaS-binding assays and intracellular 3'-5'-cyclic adenosine monophosphate (cAMP) level determinations, we demonstrate that zfMOR exhibits a pharmacological profile similar to that of the mammalian MOR. Besides, the internalization process of zfMOR after opiate agonist treatment (morphine, DAMGO, etorphine) resembles the pattern observed for its mammalian counterpart. These similarities suggest that the zebrafish is a good model for the study of the opioid effects in development.

Morphine Regulates Dopaminergic Neuron Differentiation via miR-133b

“…The antagonist naloxone did not significantly change the expression of this miR, but it could block the morphine effect. Although more selective agonists such as [D-Ala 2 ,N-Me-Phe 4 ,Gly 5 -ol]-enkephalin or antagonists such as Cys2-Tyr3-Orn5-Pen7-amide were not used to define the receptor involved because of the lack of affinity of such ligands for zfMOR (de Velasco et al, 2009), such morphine effect of miR-133b level was probably mediated by the activation of zfMOR.…”

“…The effects of morphine in the embryos are probably mediated by zfMOR, the opioid receptor that exhibits highest affinity toward morphine (de Velasco et al, 2009). To establish the role of zfMOR in regulating miR133b without the availability of a zfMOR-selective antagonist, we decided to silence zfMOR by morpholino oligonucleotide injection.…”

“…At 24 h after fertilization (hpf), the dopaminergic system begins its differentiation, and the first TH-positive neurons begin to be detected at this particular developmental stage (Filippi et al, 2007). Our previous studies also indicated that at 24 hfp, there is a robust expression of zfMOR, the putative target of morphine (de Velasco et al, 2009). Therefore, the use of 24 hpf zebrafish embryos not only will provide information on the implication of the opioid system in the maturation and differentiation of dopaminergic neurons compared with any other stages of development but also will demonstrate that the -opioid receptor is functional in the zebrafish and has a specific role in the development of the CNS and a possible pathway that leads to addiction.…”

Construction of an Affordable and Easy-to-Build Zebrafish Facility

“…The simple construction and maintenance of this system means that current protocols found in the literature are available to small research institutions 1,2,[10][11][12] . Maintenance is simple making this an ideal system for undergraduate student research.…”

“…Nonetheless, in vivo research can be performed using other animal species that require less elaborate logistics. Zebrafish (Danio rerio) have been successfully used as an in vivo model to study genetics, development, pathophysiology, and pharmacology 1, 2,10,11,12 . The facilities required to house zebrafish for experimentation are relatively simple and significantly less expensive when compared to rodent facilities.…”