1. Actin rearrangements in the amygdala and the DH are required for the acquisition and consolidation of the aversive memories of drug withdrawal.
Aversive memories associated with drug withdrawal may contribute to persistent drug seeking. Molecular mechanisms that are critical for aversive memory formation have yet to be elucidated. We found that conditioned morphine withdrawal induced actin rearrangements in the amygdala and the dorsal hippocampus (DH) but not in the nucleus accumbens (NAc). We further found that inhibition of actin rearrangements by intra-amygdala or intra-DH injections of latrunculin A, an inhibitor of actin polymerization, significantly attenuated CPA. Furthermore, we found that manipulation of amygdala β-adrenoceptor activity by its antagonist propranolol and agonist clenbuterol differentially altered actin rearrangements in the DH. Therefore, our findings reveal that actin rearrangements in the amygdala and the DH are required for the acquisition and consolidation of the aversive memories of drug withdrawal and that the β-noradrenergic system within the amygdala modulates aversive memory consolidation by regulating actin rearrangements (Hou et al., JNS, 2009).
2. Actin polymerization-dependent increase in synaptic Arc/Arg3.1 expression in the amygdala is crucial for the expression of aversive memory associated with drug withdrawal.
We demonstrated that actin polymerization within the amygdala triggered transportation of activity-regulated cytoskeletal-associated protein (Arc/Arg3.1) into amygdalar synapses. Increased synaptic Arc/Arg3.1 expression contributed to aversive memory formation by regulating synaptic AMPA receptor (AMPAR) endocytosis, as in vivo knockdown of amygdalar Arc/Arg3.1 with Arc/Arg3.1-shRNA prevented both AMPAR endocytosis and CPA formation. We also demonstrated that conditioned morphine withdrawal led to induction of LTD in the amygdala through AMPAR endocytosis. We further demonstrated that Arc/Arg3.1-regulated AMPAR endocytosis was GluR2 dependent, as intra-amygdala injection of Tat-GluR23Y, a GluR2-derived peptide that has been shown to specifically block regulated, but not constitutive, AMPAR endocytosis, prevented AMPAR endocytosis, LTD induction, and aversive memory formation. Therefore, this study extends previous studies on the role of actin polymerization in synaptic plasticity and memory formation by revealing the critical molecular events involved in aversive memory formation as well as LTD induction, and by showing that Arc/Arg3.1 is a crucial mediator for actin polymerization functions, and, thus, underscores the unknown details of how actin polymerization mediates synaptic plasticity and memory (Liu et al., JNS, 2012).
3. Extinction of aversive memories associated with morphine withdrawal requires ERK-mediated epigenetic regulation of brain-derived neurotrophic factor transcription in the rat ventromedial prefrontal cortex.
Recent evidence suggests that histone deacetylase (HDAC) inhibitors facilitate extinction of rewarding memory of drug taking. However, little is known about the role of chromatin modification in the extinction of aversive memory of drug withdrawal. We found that CPA extinction training induced an increase in recruiting cAMP response element-binding protein (CREB) to and acetylation of histone H3 at the promoters of BDNF exon I transcript and increased BDNF mRNA and protein expression in the vmPFC of acute morphine-dependent rats and that such epigenetic regulation of BDNF gene transcription could be facilitated or diminished by intra-vmPFC infusion of HDAC inhibitor trichostatin A orERK inhibitor U0126 before extinction training. Correspondingly, disruption of the epigenetic regulation of BDNF gene transcription with U0126 or suppression of BDNF signaling with Trk receptor antagonist K252a or BDNF scavenger tyrosine kinase receptor B (TrkB)-Fc blocked extinction of CPA behavior. We also found that extinction training-induced activation of ERK and CREB and extinction of CPA behavior could be potentiated or suppressed by intra-vmPFC infusion of D-cycloserine, a NMDA receptor partial agonist or aminophosphonopentanoic acid, a NMDA receptor antagonist. We conclude that extinction of aversive memory of morphine withdrawal requires epigenetic regulation of BDNF gene transcription in the vmPFC through activation of the ERK-CREB signaling pathway perhaps in a NMDA receptor-dependent manner (Wang et al., 2012).
4. Chronic morphine treatment impaired hippocampal long-term potentiation and spatial memory via accumulation of extracellular adenosine acting on adenosine A1 receptors.
Chronic exposure to opiates impairs LTP and spatial memory, but the underlying mechanisms remain to be elucidated. Given the well known effects of adenosine, an important neuromodulator, on hippocampal neuronal excitability and synaptic plasticity, we investigated the potential effect of changes in adenosine concentrations on chronic morphine treatment-induced impairment of hippocampal CA1 LTP and spatial memory. We found that chronic treatment in mice with either increasing doses of morphine for 7 d or equal daily dose of morphine for 12 d led to a significant increase of hippocampal extracellular adenosine concentrations. Importantly, we found that accumulated adenosine contributed to the inhibition of the hippocampal CA1 LTP and impairment of spatial memory retrieval measured in the Morris water maze. Adenosine A1 receptor antagonist significantly reversed chronic morphine-induced impairment of hippocampal CA1 LTP and spatial memory. Likewise, adenosine deaminase, which converts adenosine into the inactive metabolite inosine, restored impaired hippocampal CA1 LTP. We further found that adenosine accumulation was attributable to the alteration of adenosine uptake but not adenosine metabolisms. Bidirectional nucleoside transporters (ENT2) appeared to play a key role in the reduction of adenosine uptake. Changes in PKCα/β activity were correlated with the attenuation of the ENT2 function in the short-term (2 h) but not in the long-term (7 d) period after the termination of morphine treatment. This study reveals a potential mechanism by which chronic exposure to morphine leads to impairment of both hippocampal LTP and spatial memory (Lu et al., JNS, 2010).
5. Serine 363 of the δ-opioid receptor is crucial for adopting distinct pathways to activate ERK1/2 in response to stimulation with different ligands.
Distinct opioid receptor agonists have been proved to induce differential patterns of ERK activation, but the underlying mechanisms remain unclear. We report that Ser363 in the δ-opioid receptor (δOR) determines the different abilities of the δOR agonists DPDPE and TIPP to activate ERK by G-protein- or β-arrestin-dependent pathways. Although both DPDPE and TIPP activated ERK1/2, they showed different temporal, spatial and desensitization patterns of ERK activation. We show that that DPDPE employed G protein as the primary mediator to activate the ERK cascade in a Src-dependent manner, whereas TIPP mainly adopted a β-arrestin1/2- mediated pathway. Moreover, we found that DPDPE gained the capacity to adopt the β-arrestin1/2-mediated pathway upon Ser363 mutation, accompanied by the same pattern of ERK activation as that induced by TIPP. Additionally, we found that TIPP- but not DPDPE-activated ERK could phosphorylate G-protein-coupled receptor kinase-2 and β-arrestin1. However, such functional differences of ERK disappeared with the mutation of Ser363. Therefore, the present study reveals a crucial role for Ser363 in agonist-specific regulation of ERK activation patterns and functions (Xu et al., JCS, 2010).

2004   National Science Fund for Distinguished Young Scholars, NSFC
2007  “Shanghai leading talents”, STCS

1. Chen ZG; Wang YJ; Chen RS; Geng F; Gan CL; Wang WS; Liu X; Zhou H; He L; Hu G*; Liu JG* (2019) Ube2b-dependent degradation of DNMT3a relieves a transcriptional brake on opiate-induced synaptic and behavioral plasticity , Molecular Psychiatry, doi: 10.1038/s41380-019-0533-y. 

2. Xiao L; Wang YJ; Zhang MM; Wu WW; Kong LH; Ma Y; Xu XJ; Liu X; Qian He; Qian YY; Sun HJ; Wu HH; Lin C; HM; Ye RR; Jiang S; Ye RF; Yuan C; Fang SY; Xue DQ; Yang X; Chen H; Zheng YL; Yu LQ; Xie Q; Zheng L; Fu W; Li W*; Qiu Z; Liu JG*; Shao L* (2019) Discovery of a highly selective and potent kappa opioid receptor agonist from N-cyclopropylmethyl-7#-phenyl-6,14-endoethanotetrahydro-northebaines with reduced central nervous system. J Med Chem 62: 11054-11070. 

3. Lu YC, Wang YJ, Lu B, Chen M, Zheng P, Liu JG (2018) ACC to dorsal medial striatum inputs modulate histaminergic itch sensation. J Neurosci 38: 3466-3417. 

4. Wang W, Ju YY, Zhou QX, Tang JX, Li M, Zhang L, Kang S, Chen ZG, Wang YJ, Ji H, Ding YQ, Xu L,Liu JG*(2017) The Small GTPase Rac1 Contributes to Extinction of Aversive Memories of Drug Withdrawal by Facilitating GABAA Receptor Endocytosis in the vmPFC. J Neurosci 37: 7096-7110. 

5. Zhang L, Kibaly C, Wang YJ, Xu C, Song KY, W McGarrah P, Loh HH, Liu JG*, Law PY* (2017). Src-dependent phosphorylation of μ-opioid receptor at Tyr336 modulates opiate withdrawal. EMBO Mol Med. doi 9:1521-1536. 

6. Tao YM, Yu C, Wang WS, Hou YY, Xu XJ, Chi ZQ, Ding YQ, Wang YJ, Liu JG* (2017) Heteromers of μ opioid and dopamine D1 receptors modulate opioid-induced locomotor sensitization in a dopamine-independent manner. Br J Pharmacol 174:2842-2861. 

7. Chen ZG, Liu X, Wang W, Geng F, Gao J, Gan CL, Chai JR, He L, Hu G, Zhou H, Liu JG *(2016). Dissociative role for dorsal hippocampus in mediating heroin self-administration and relapse through CDK5 and RhoB signaling revealed by proteomic analysis. Addict Biol 22:1731-1742. 

8. Wang YJ, Hang A, Lu YC, Long Y, Zan GY, Li XP, Wang Q, Zhao ZX, He L, Chi ZQ, Liu JG* (2016) Kappa receptor activation in different brain regions differentially modulates anxiety-related behaviors in mice. Neuropharmacology 110: 92-101. 

9. Wang Q, Long Y, Hang A, Zan GY, Shu XH, Wang YJ, Liu JG* (2016) The anxiolytic- and anti-depressant-like effects of ATPM-ET, a novel k agonist and m partial agonist, in mice. Psychopharmacology 233:2411-2418. 

10. Zhang LS, Wang YJ, Ju YY, Zan GY, Xu C, Hong MH, Wang YH, Ch ZQ, Liu JG (2015) Role for engagement of β-arrestin2 by the transactivated EGFR in agonist-specific regulation of δ-opioid receptor activation of ERK1/2. Br J Pharmacol 172: 4847-4863. 

11. Wang WS, Chen ZG, Liu WT, Chi ZQ, He L, Liu JG (2014) Dorsal hippocampal NMDA receptor blockade impairs extinction of naloxone-precipitated conditioned place aversion in acute morphine-treated rats by suppressing ERK and CREB phosphorylation in the basolateral amygdala. Br J Pharmacol 172: 482-491. 

12. Kang S, Ling QL, Liu WT, Lu B, Liu Y, He L, Liu JG* (2013) Down-regulation of dorsal striatal RhoA activity and impairment of working memory in middle-aged rats. Neurobiol Learn Mem103:3-10. 

13. Liu Y, Zhou QX, Hou YY, Lu B, Yu C, Chen J, Ling QL, Cao J, Chi ZQ, Xu L*, Liu JG* (2012) Actin polymerization-dependent increase in synaptic Arc/Arg3.1 expression in the amygdala is crucial for the expression of aversive memory associated with drug withdrawal. J Neurosci 32: 12005-12017. 

14. Wang WS, Kang S, Liu WT, Li M, Liu Y, Yu C, Chen J, Zhi-Qiang Ch ZQ, He L, and Jing-Gen Liu JG* (2012) Extinction of aversive memories associated with morphine withdrawal requires ERK-mediated epigenetic regulation of brain-derived neurotrophic factor transcription in the rat ventromedial prefrontal cortex. J Neurosci 32: 13763-13775. 

15. Lu G, Zhou QX, Kang S, Li QL, Zhao LC, Chen JD, Sun JF, Cao J, Wang YJ, Chen J, Chen XY, Zhong DF, Chi ZQ, Xu L*, Liu JG* (2010) Chronic morphine treatment impaired hippocampal LTP and spatial memory via accumulation of extracellular adenosine acting on adenosine A1 receptors. J Neurosci 30: 5058-5070. 

16. Xu C, Hong MH, Zhang LS, Hou YY, Wang FF, Chen YJ, Xu XJ, Chen J, Xie X, Ma L, Chi ZQ, Liu JG* (2010) Serine 363 Residue of δ-Opioid Receptor is Crucial for Adopting Distinct Pathways to Activate ERK1/2. J Cell Sci 123: 4259-4270. 

17. Hou YY, Lu B, Li M, Liu Y, Chen J, Chi ZQ, and Liu JG* (2009) Involvement of actin rearrangements within the amygdala and the dorsal hippocampus in aversive memories of drug withdrawal in acute morphine dependent rats. J Neurosci 29: 12244-12254. 

18. Hong MH, Xu C, Wang YJ, Ji JL, Tao YM, Xu XJ, Chen J, Xie X, Zhi-Qiang Chi ZQ, Liu JG* (2009) Role of Src in Ligand-specific Regulation of δ-opioid Receptor Desensitization and Internalization. J Neurochem 108: 102-114. 

19. Wang YJ, Tao YM, Xu XJ, Chen J, Cao YL, Chi ZQ, Liu JG* (2009) Pharmacological Characterization of ATPM-AZ, a Novel Mixed κ Agonist and μ Agonist/Antagonist That Attenuates Morphine Antinociceptive Tolerance and Heroin Self-Administration Behavior. J Pharmacol Exp Ther 329: 306-313. 

20. Lin X, Wang YJ, Huo YY, Li Q, Chi ZQ, Liu JG* (2009) Morphine promotes SH-SY5Y cell apoptosis through c-Jun N-terminal kinase-mediated activation of mitochondria-dependent apoptosis pathway. FEBS J 276: 2022-2036. 

21. Chen XL, Lu G, Gonh YX, Zhao LC, Chen J, Chi ZQ, Yang YM, Chen Z, Li QL, Chi ZQ, Liu JG* (2007) Involvement of changes in protein expression of hippocampal energy metabolism enzymes in behavioral abnormalities during chronic morphine treatments. Cell Research 17: 689-700. 

22. Lin X, Li Q, Wang YJ, Ju YW, Chi ZQ, Wang MW, Liu JG* (2007) Morphine Inhibits Doxorubicin-induced Reactive Oxygen Species Generation and Nuclear Factor-κB Transcriptional Activation in Neuroblastoma SH-SY5Y Cells. Biochem J 406: 215-221. 

23. Wu ZQ, Chen J, Chi ZQ and Liu JG* (2007) Involvement of Dopamine System in Regulation of Na+,K+-ATPase in the Striatum upon Activation of Opioid Receptors by Morphine. Mol Pharmacol 71: 519-530. 

24. Wu ZQ, Li M, Chen J, Chi ZQ and Liu JG* (2006) Involvement of cAMP/cAMP-Dependent Protein Kinase Signaling Pathway in Regulation of Na+, K+-ATPase upon Activation of Opioid Receptors by Morphine. Mol Pharmacol 69: 866-876.