The Roles And Mechanisms Of SIRT1 In Morphine Addiction In The Ventrolateral Orbital Cortex

BackgroundDrug addiction is the most grave public health problems,the key pathological mechanism of which is the persistence of addictive memory.It is believed that the mesolimbic dopamine system is the main reward system in the brain,which participates in the formation and maintenance of addictive memory and mediates the reward effect.The brain regions associated with reward mainly included the ventral tegmental area,nucleus accumbens,amygdala,hippocampus and prefrontal cortex.The ventrolateral orbital cortex（VLO）is a major component of the prefrontal cortex,which has mutual fiber connection with brain regions related to drug addiction such as nucleus accumbens and hippocampus.Our previous study found that VLO is an important nuclear group in the regulation of morphine addiction.Silent information regulator transcript 1（SIRT1）is widely distributed in the brain.Studies had shown that,SIRT1 plays an significant role in learning,memory and drug reward,and SIRT1 is involved in the regulation of morphine addiction in VLO.However,the exact mechanism remains unclear.ObjectivesThis study will clarify the role and exact mechanism of SIRT1 in morphine addiction in VLO,and provide theoretical basis for finding new targets for the treatment of morphine addiction,which has important scientific value and potential applicative prospects.MethodsIn this study,the morphine-induced conditioned place preference（CPP）model was established to simulate the process of morphine addiction in rats.The microinjection of SIRT1 interfering and overexpressed adeno-associated virus（AAV）vectors into VLO was performed by brain stereolocalization surgery respectively,to establish the models of SIRT1 interference and overexpression in VLO,and the behavioral changes of CPP were observed.Finally,the effect of resveratrol on morphine addiction was verified in CPP model of rat by intraperitoneal injection of SIRT1 agonist resveratrol.The expression changes of SIRT1 and downstream addictive memory and synaptic plasticity related molecules PSD95,c-fos,ERK,CREB and BDNF in VLO were detected by western blot（WB）and immunohistochemistry（IHC）staining.Combined with the changes of CPP behavioral indicators,the role of SIRT1 and synaptic plasticity molecules in the formation of morphine addiction memory was comprehensively analyzed.Result1.After the formation of morphine-induced CPP in rats,WB results showed that protein expression levels of SIRT1 and PSD95,p-ERK,CREB,BDNF in VLO were significantly increased,and m RNA sequencing results showed that morphine induces changes in synaptic structure and function in rat VLO.2.WB,q PCR and IHC staining results showed that the model of interference and overexpression of SIRT1 in VLO were successfully constructed.The specific interference of SIRT1 in VLO promoted the formation of morphine-induced CPP.WB results showed that the interference of SIRT1 promoted the acetylation of H3K9 in VLO and inhibited the protein expression of BDNF,and the promoting effect of morphine administration on the expression of p-Ca MKIIα,p-ERK,CREB and c-fos was further increased.On the contrary,the specific overexpression of SIRT1 in VLO inhibited the formation of morphine-induced CPP in rat.WB results showed that the overexpression of SIRT1 inhibited the acetylation of H3K9 in VLO and promoted the expression of BDNF and PSD-95,and the promoting effect of morphine administration on the expression of p-Ca MKIIα,p-ERK,CREB and cfos was reversed.3.Intraperitoneal injection of SIRT1 agonist RSV inhibited morphine-induced CPP in rats.WB and IHC staining results showed that intraperitoneal injection of RSV promoted the expression of SIRT1 in VLO.WB results showed that intraperitoneal injection of RSV further promoted the expression of PSD95,c-fos and CREB proteins in morphine-induced VLO.The expression of p-Ca MKIIα and p-ERK protein in VLO was reversed,and BDNF expression in VLO was not significantly affected.Conclusion1.After the formation of morphine-induced CPP in rats,the expression of SIRT1 in VLO was was abnormally elevated by the activation of the downstream CREB/BDNF pathway,which caused the change of synaptic plasticity,and was involved in the process of morphine addiction.2.AAV-specific interference of SIRT1 in VLO promotes the formation of morphineinduced CPP,while the specific overexpression of SIRT1 in VLO inhibits the formation of morphine-induced CPP.SIRT1 can affect the expression of downstream addictive memory and synaptic plasticity related molecules through its deacetylation.3.Intraperitoneal injection of SIRT1 agonist RSV inhibited the formation of morphine-induced CPP,suggesting that RSV may play a potential therapeutic role in morphine addiction.