Pick1 Participate In The Regulation Of Fentanyl-induced Hyperalgesia In Rats

Clinically,patients who receive high doses of fentanyl during surgery will be hyperalgesia which is opposite to the analgesic effect of opioids.This phenomenon is called opioid-induced hyperalgesia(OIH).OIH is an urgent problem to be solved in clinical practice.As the mechanism of OIH is still unclear,there is no suitable treatment at present.The dorsal root ganglion is a primary neuron for feeling signaling.Meanwhile,DRG plays a crucial role in the research field of pain.Based on the previous work in the laboratory,the molecular mechanism of Opioid-induced hyperalgesia about Pick1(protein interacting with C kinase1)which is expressed in DRG was explored preliminarily.First,the OIH model was prepared by subcutaneous injection of fentanyl into the rat neck.Then,we found the significant difference of Pick1 in the DRG between the control group and the OIH group by methylation sequencing.Next,it was detected that the expression level of the Pick1 gene was significantly less in DRG of OIH rats by semi-quantitative PCR.So,we constructed the Pick1 over-expression vector and prepare the lentivirus for operating intrathecal injection on rats.After the expression of recombinant lentivirus,we found that the threshold current of the action potential of DRG cells decreased significantly after fentanyl incubation in the Control group after the injection of the empty vector lentivirus,indicating that the cells were sensitized.Finally,we measured the mechanical pain threshold of the rats injected with lentivirus.The pain threshold of the Control group did not change after the intrathecal injection of the empty vector lentivirus,which means the effect of the virus on the pain threshold was excluded,but the pain threshold significantly decreased after the fentanyl model.In the plv-pick1 group,the pain threshold increased after intrasheath injection of plv-egfp-n-Pick1 recombinant lentivirus,and returned to the initial value of normal rats after fentanyl injection.Meanwhile,according to statistics on the data of methylation sequencing,we found that among the genes with significant differences in OIH group,some of the genes such as Pick1 particularly were specifically expressed in the male reproductive system or had the highest expression in the male reproductive system.Therefore,we doubted whether there was gender difference in OIH.By constructing different gender’s OIH models and conducting corresponding behavioral measurement,we present that there is a gender difference in the occurrence time of OIH between female and male rats,that is,the occurrence time of OIH in female animals is delayed by about 1.5h on average compared with that of male rats,the recovery time was also slightly delayed than in male rats,and the difference may be caused by Pick1.The expression of Pick1 in DRG in male is muchhigher then which in female by semi-quantitative PCR.Next,the female rats were operated intrasheath injection with lentivirus containing Pick1 overexpression vector to explore whether Pick1 was involved in the regulation of the occurrence time of OIH.According to the results,it is suggested that Pick1 expression on DRG can alleviate Opioid-inducedhyperalgesia,and it is verified that Pick1 may participate in the regulation of hyperalgesia though the DRG,which helps us understand the mechanism of OIH and provides a new possible method for the treatment of OIH.In addition,according to the experimental results after interference of Pick1 at female DRG,it is reasonable to speculate that Pick1 may cause the gender difference in the occurrence time of OIH in rats,providing a possible target for exploring the molecular mechanism of gender difference in OIH.