doi: 10.1016/j.baga.2011.04.001.
GPR88 - a putative signaling molecule predominantly expressed in the striatum: Cellular localization and developmental regulation
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- PMID:21804954
- PMCID: PMC3144573
- DOI: 10.1016/j.baga.2011.04.001
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GPR88 - a putative signaling molecule predominantly expressed in the striatum: Cellular localization and developmental regulation
Vincent Van Waes et al. Basal Ganglia..
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Abstract
GPR88 is a putative G-protein-coupled receptor that is highly and almost exclusively expressed in the striatum. Its function remains unknown. We investigated GPR88 cellular localization and expression levels across development in different functional domains of the striatum in juvenile (P25), adolescent (P40), and adult (P70) rats, by in situ hybridization histochemistry. At all ages, GPR88 mRNA expression was most robust in the sensorimotor (lateral) striatum and was detected in virtually every neuron. Expression was highest in juveniles and decreased thereafter with regionally distinct trajectories. Thus, in the dorsal striatum, there was a progressive decrease from juveniles to adolescents to adults. In contrast, in the nucleus accumbens, the only (modest) decrease occurred between juveniles and adolescents. These findings indicate that GPR88 is expressed in all striatal neurons, but is differentially regulated across development in different striatal regions.
Figures
Distribution of GPR88 expression in the striatum. Illustrations of film autoradiograms depict the distribution of GPR88 mRNA in coronal sections from the rostral, middle and caudal striatum in juvenile (P25) and adult (P70) rats. The maximal hybridization signal is black. CPu, caudate-putamen; Cx, cortex; GP, globus pallidus; NAc, nucleus accumbens; OT, olfactory tubercle.
Cellular localization of GPR88 mRNA in the striatum. Examples of neurons labeled for NeuN (neuronal marker; fluorescence immunohistochemistry, red) (left column) and for enkephalin (ENK) mRNA or GPR88 mRNA (fluorescence in situ hybridization histochemistry, green) (center column) in the caudal caudate-putamen and in the globus pallidus are shown for adult rats (P70). Double-labeled neurons (merge, yellow) are depicted in the right column. GPR88 mRNA is expressed in all striatal neurons (middle row), but is not expressed in the globus pallidus (bottom row). White arrowheads indicate examples of NeuN-positive/ENK-negative cells (top row). Scale bars = 25 μm.
Localization of GPR88 mRNA in medium-sized and large neurons of the striatum. Lower power photomicrographs (top row) depict neurons labeled for NeuN (red; left column), or GPR88 mRNA (green; center column), and double-labeled neurons (merge, yellow; right column) in the caudate-putamen in adults (P70). Higher power photomicrographs (middle and bottom rows) display the neurons in the boxed areas in the top images. Examples of neurons with a relatively low (middle row) or high (bottom row) GPR88 mRNA signal are shown. The white arrowhead indicates a large neuron, presumably a cholinergic interneuron. Scale bar = 10 μm.
Topography of GPR88 expression in the striatum at different postnatal ages (left) and differences in expression between P25 and P70 animals (boxed; right). Maps depict the distribution of GPR88 expression in the rostral, middle and caudal striatum in juvenile (P25), adolescent (P40) and adult (P70) rats. For P25, P40 and P70 groups, the data are expressed relative to the maximal value observed in the P25 group (% of max. P25). The differences in GPR88 expression between P25 and P70 rats (Δ P25-70) are expressed as the percentage of the maximal change (% of max. Δ). Sectors with significant differences (P<0.05) are coded as indicated. Sectors without a significant decrease are in white. Caudate-putamen: c, central; d, dorsal; dc, dorsal central; dl, dorsolateral; dm, dorsomedial; m, medial; v, ventral; vc, ventral central; vl, ventrolateral. Nucleus accumbens: mC, medial core; lC, lateral core; mS, medial shell; vS, ventral shell; lS, lateral shell.
Expression of GPR88 across development in select areas of the striatum and nucleus accumbens. Mean density values (mean±SEM) for GPR88 mRNA levels in juvenile (P25), adolescent (P40) and adult (P70) rats are depicted for 4 sectors from the middle striatum (top) and the 5 sectors of the nucleus accumbens (bottom). Caudate-putamen: d, dorsal; dl, dorsolateral; vl, ventrolateral; c, central. Nucleus accumbens: mC, medial core; lC, lateral core; mS, medial shell; vS, ventral shell; lS, lateral shell. * P<0.05, ** P<0.01, *** P<0.001, vs. preceding age group or as indicated.
Differential regulation of GPR88 expression in the caudate-putamen and nucleus accumbens across development. Normalized mean density values (relative to P25; mean±SEM) for GPR88 mRNA levels in the whole caudate-putamen (all sectors pooled, filled circles) and the whole nucleus accumbens (open circles) at P25, P40 and P70 are shown. *** P<0.001, vs. preceding age group;++ P<0.01, caudate-putamen vs. nucleus accumbens.
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