Immunohistochemical localization of mu opioid receptor in the marginal division with comparison to patches in the neostriatum of the rat brain

Abstract

BackgroundMu opioid receptor (MOR), which plays key roles in analgesia and also has effects on learning and memory, was reported to distribute abundantly in the patches of the neostriatum. The marginal division (MrD) of the neostriatum, which located at the caudomedial border of the neostriatum, was found to stain for enkephalin and substance P immunoreactivities and this region was found to be involved in learning and memory in our previous study. However, whether MOR also exists in the MrD has not yet been determined.MethodsIn this study, we used western blot analysis and immunoperoxidase histochemical methods with glucose oxidase-DAB-nickel staining to investigate the expression of MOR in the MrD by comparison to the patches in the neostriatum.ResultsThe results from western blot analyses revealed that the antibody to MOR detected a 53 kDa protein band, which corresponded directly to the molecular weight of MOR. Immunohistochemical results showed that punctate MOR-immunoreacted fibers were observed in the "patch" areas in the rostrodorsal part of the neostriatum but these previous studies showed neither labelled neuronal cell bodies, nor were they shown in the caudal part of the neostriatum. Dorsoventrally oriented dark MOR-immunoreactive nerve fibers with individual labelled fusiform cell bodies were firstly observed in the band at the caudomedial border, the MrD, of the neostriatum. The location of the MOR-immunoreactivity was in the caudomedial border of the neostriatum. The morphology of the labelled fusiform neuronal somatas and the dorsoventrally oriented MOR-immunoreacted fibers in the MrD was distinct from the punctate MOR-immunoreactive diffuse mosaic-patterned patches in the neostriatum.ConclusionsThe results indicated that MOR was expressed in the MrD as well as in patches in the neostriatum of the rat brain, but with different morphological characteristics. The punctate MOR-immunoreactive and diffuse mosaic-patterned patches were located in the rostrodorsal part of the neostriatum. By contrast, in the MrD, the dorsoventrally parallel oriented MOR-immunoreactive fibers with individual labelled fusiform neuronal somatas were densely packed in the caudomedial border of the neostriatum. The morphological difference in MOR immunoreactivity between the MrD and the patches indicated potential functional differences between them. The MOR most likely plays a role in learning and memory associated functions of the MrD.

Altered functional connectivity of the marginal division in migraine: a resting-state fMRI study

“…This may also be associated with the evident increased substance P in the ipsilateral spinal cord dorsal horn [ 13 ]. Mu opioid receptors (MORs) are localized in the MrD, and it is one member of the seven transmembrane family of G-protein coupled receptors, which may underlie pain and analgesia in the MrD of rat striatum [ 14 ]. To date, however, it has remained unknown whether and how MrD participates in pain modulation in the human brain in vivo.…”

Determination of μ-, δ- and κ-opioid receptors in forebrain cortex of rats exposed to morphine for 10 days: Comparison with animals after 20 days of morphine withdrawal

“…Content of μ-OR in the mammalian brain was determined by numerous methods, including Northern blot analysis, RNase protection assays, RT-PCR, immunohistochemistry and specific radioligands [ 22 , 42 – 44 ]. However, the number of reports using immunoblot analysis for determination of μ-OR protein content in FBC was rather limited and vastly heterogeneous values of M w of μ-OR-related proteins recognized by specific antibodies were described.…”

Characteristics of IL‐25 and allergen‐induced airway fibrosis in a murine model of asthma

“…The peroxidase anti‐peroxidase technique was used as previously described . Positive cells were detected with the glucose oxidase‐diaminobenzidine‐nickel method . The slides were analysed on a Leica DM6000B microscope (Leica, Wetzlar, Germany) connected with a Leica Application Suite version 3.6 .…”