Role of PICK1 in trafficking of GluR1- and GluR2-containing AMPA receptors in spinal cord in a rat model of remifentanil-induced hyperalgesia

Abstract

Objective To evaluate the role of protein interacting with Cα kinase 1(PICK1)in trafficking of GluR1- and GluR2-containing AMPA receptors in the spinal cord in a rat model of remifentanil-induced hyperalgesia. Methods Thirty-two male Sprague-Dawley rats, weighing 240-260 g, aged 42-49 days, in which IT catheters were successfully placed, were randomly divided into 4 groups(n=8 each)using a random number table: control group(group C), normal saline+ remifentanil group(group NS+ R), PICK1 antisense oligonucleotide+ normal saline group(group AS+ NS), and PICK1 antisense oligonucleotide+ remifentanil group(group AS+ R). Normal saline 10 μl was injected intrathecally in C and NS+ R groups, and thiolmodificated PICK1 antisense oligonucleotide 10 μg/10 μl was injected intrathecally in AS+ NS and AS+ R groups, once a day for 4 consecutive days.After the end of IT injection, remifentanil was infused intravenously at 1.2 μg·kg-1·min-1 for 60 min in NS+ R and AS+ R groups, while the equal volume of normal saline was given instead for 60 min in C and AS+ NS groups.The mechanical paw withdrawal threshold(MWT)and thermal paw withdrawal latency(TWL)were measured at 24 h before normal saline or remifentanil infusion, and at 2, 6, 24, and 48 h after the end of normal saline or remifentanil infusion.The rats were sacrificed after the last measurement of pain threshold.The lumbar segment L4-6 of the spinal cord was removed for detection of the expression of GluR1 and GluR2-containing AMPA receptors in cell membrane and in cytoplasm by Western blot.The ratio of protein expression in cell membrane to that in cytoplasm(m/c ratio)was calculated.The ratio of GluR1-containing AMPA receptor expression to GluR2-containing AMPA receptor expression in cell membrane was calculated(mGluR1/mGluR2). Results Compared with group C, the TWL was significantly shortened, and the MWT was decreased at T1-4, the expression of GluR1-containing AMPA receptors in cell membrane was up-regulated, and the m/c ratio was increased, the expression of GluR2-containing AMPA receptors in cell membrane was down-regulated, and the m/c ratio was decreased, and mGluR1/mGluR2 was increased in NS+ R and AS+ R groups.Compared with group NS+ R, the TWL was significantly prolonged, and the MWT was increased at T1-4, the expression of GluR2-containing AMPA receptors in cell membrane was up-regulated, and the m/c ratio was increased, and mGluR1/mGluR2 was decreased, and no significant change was found in the other parameters in group AS+ R. Conclusion PICK1 can promote GluR2-containing AMPA receptor internalization, and exerts no effect on trafficking of GluR1-containing AMPA receptors in the spinal cord, which may be involved in the mechanism of remifentanil-induced hyperalgesia in rats. Key words: Carrier proteins; Piperidines; Hyperalgesia; Receptors, AMPA