DAMGO-induced mu opioid receptor internalization and recycling restore morphine sensitivity in tolerant rat
DAMGO-induced mu opioid receptor internalization and recycling restore morphine sensitivity in tolerant rat
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DAMGO 诱导 mu 阿片受体内化和循环恢复耐受大鼠吗啡敏感性
DOI：
10.1016/j.ejphar.2020.173118
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发表时间：
2020
影响因子：
5
通讯作者：
Xu Tao
中科院分区：
文献类型：
--
作者：
Ma Xiaqing;Chen Rui;Huang Min;Wang Wenying;Luo Limin;Kim Dong Kwan;Jiang Wei;Xu Tao
本研究探讨了damgo诱导的μ阿片受体（MOR）内化对吗啡耐受的影响。6 ~ 8周龄雄性Sprague-Dawley大鼠（200 ~ 250 g）经鞘内注射吗啡（15 μg/10 μl，每日2次，连用6 d）诱导抗痛觉性耐受，并通过甩尾和脱爪试验评价其抗痛觉性耐受。响应延迟以最大可能效果的百分比（%MPE）计算。第6天静脉注射大剂量DAMGO， 24、48、72 h后进行甩尾和脱爪试验。western blotting检测膜和胞浆MOR的表达。用MOR- flag质粒转染HEK293细胞，在吗啡（10 μM）作用6 d后，用1 μM DAMGO处理细胞，30min和60min后用免疫荧光法检测MOR定位。5 d后重复吗啡治疗诱导耐受；在HEK293细胞中，DAMGO在30分钟后刺激了MOR的内化，1小时后刺激了MOR的再循环。注射DAMGO后24、48和72小时，体内MOR的膜和细胞质表达没有变化。吗啡不会引起明显的MOR内化或下调，并且很容易诱导耐受性。DAMGO通过增强受体内吞作用来对抗这种作用，从而逆转吗啡诱导的抗痛觉耐受性并恢复其镇痛功效。
This study investigated the effect of DAMGO-induced μ opioid receptor (MOR) internalization on morphine tolerance. Male Sprague-Dawley rats (200–250 g) aged 6–8 weeks were administered morphine via intrathecal (i.t.) injection (15 μg/10 μl twice daily for 6 days) to induce antinociceptive tolerance, which was evaluated using the tail-flick and paw-withdrawal tests. Response latency was calculated as the percentage of maximum possible effect (%MPE). A bolus of DAMGO was administered by i.t. injection on day 6, and the tail-flick and paw-withdrawal tests were carried out 24, 48, and 72 h later. Membrane and cytosolic MOR expression was assessed by western blotting. HEK293 cells were transfected with MOR-FLAG plasmid and after 6 days of morphine treatment (10 μM), the cells were treated with 1 μM DAMGO, and MOR localization was examined by immunofluorescence analysis 30 and 60 min later. Repeated morphine treatment induced tolerance after 5 days; however, i.t. DAMGO administration restored morphine sensitivity and enhanced acute morphine-induced antinociception after 24, 48, and 72 h. In HEK293 cells, DAMGO treatment stimulated MOR internalization after 30 min and MOR recycling to the membrane after 1 h. Membrane and cytoplasmic MOR expression in vivo was unchanged 24, 48, and 72 h after i.t. DAMGO injection. Morphine does not cause significant MOR internalization or downregulation, and can readily induce tolerance. DAMGO counters this effect by enhancing receptor endocytosis, thereby reversing morphine-induced antinociceptive tolerance and restoring its analgesic efficacy.