Dripps Isaac J, Wang Qin, Neubig Richard R, Rice Kenner C, Traynor John R, Jutkiewicz Emily M
Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI, USA.
Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI, USA.
Psychopharmacology (Berl). 2017 Jan;234(1):29-39. doi: 10.1007/s00213-016-4432-5. Epub 2016 Sep 13.
Regulator of G protein signaling (RGS) proteins act as negative modulators of G protein signaling. RGS4 has been shown to negatively modulate G protein signaling mediated by the delta opioid receptor (DOPr) in vitro. However, the role of RGS4 in modulating DOPr-mediated behaviors in vivo has not been elucidated.
The aim of this study was to compare the ability of the DOPr agonist SNC80 to induce DOPr-mediated antinociception, antihyperalgesia, antidepressant-like effects, and convulsions in wild-type and RGS4 knockout mice.
Antinociception was assessed in the acetic acid stretch assay. Antihyperalgesia was measured in a nitroglycerin-induced thermal hyperalgesia assay. Antidepressant-like effects were evaluated in the forced swim and tail suspension tests. Mice were also observed for convulsive activity post-SNC80 treatment. SNC80-induced phosphorylation of MAP kinase in striatal tissue from RGS4 wild-type and knockout mice was quantified by Western blot. DOPr number from forebrain tissue was measured using [H]DPDPE saturation binding.
Elimination of RGS4 potentiated SNC80-induced antinociception and antihyperalgesia. SNC80-induced antidepressant-like effects were potentiated in RGS4 knockout mice in the forced swim test but not in the tail suspension test. Additionally, RGS4 knockout did not alter SNC80-induced convulsions. SNC80-induced phosphorylation of MAP kinase was potentiated in striatum from RGS4 knockout mice. Loss of RGS4 did not affect total DOPr number.
Overall, these findings demonstrate that reduction of RGS4 functionally may increase the therapeutic index of SNC80. These results provide the first evidence of differential regulation of DOPr-mediated behaviors by RGS proteins and G protein signaling pathways.
G蛋白信号调节（RGS）蛋白作为G蛋白信号的负调节剂。RGS4已被证明在体外对由δ阿片受体（DOPr）介导的G蛋白信号起负调节作用。然而，RGS4在体内调节DOPr介导的行为中的作用尚未阐明。
本研究的目的是比较DOPr激动剂SNC80在野生型和RGS4基因敲除小鼠中诱导DOPr介导的镇痛、抗痛觉过敏、抗抑郁样作用和惊厥的能力。
在醋酸伸展试验中评估镇痛作用。在硝酸甘油诱导的热痛觉过敏试验中测量抗痛觉过敏。在强迫游泳和悬尾试验中评估抗抑郁样作用。在SNC80治疗后还观察小鼠的惊厥活动。通过蛋白质免疫印迹法对来自RGS4野生型和基因敲除小鼠纹状体组织中SNC80诱导的丝裂原活化蛋白激酶磷酸化进行定量。使用[H]DPDPE饱和结合法测量前脑组织中的DOPr数量。
RGS4的缺失增强了SNC80诱导的镇痛和抗痛觉过敏作用。在强迫游泳试验中，RGS4基因敲除小鼠中SNC80诱导的抗抑郁样作用增强，但在悬尾试验中未增强。此外，RGS4基因敲除未改变SNC80诱导的惊厥。RGS4基因敲除小鼠纹状体中SNC80诱导的丝裂原活化蛋白激酶磷酸化增强。RGS4的缺失不影响DOPr总数。
总体而言，这些发现表明RGS4功能的降低可能会提高SNC80的治疗指数。这些结果首次证明了RGS蛋白和G蛋白信号通路对DOPr介导行为调控的差异。
