[Show abstract][Hide abstract] ABSTRACT: We recently reported that a conditioned stimulus (CS) memory retrieval-extinction procedure decreases reinstatement of cocaine and heroin seeking in rats and heroin craving in humans. Here we show that non-contingent cocaine or methylphenidate injections (UCS retrieval) 1 h before the extinction sessions decreases cocaine-priming-induced reinstatement, spontaneous recovery, and renewal of cocaine seeking in rats. Unlike the CS-based memory retrieval-extinction procedure, the UCS memory retrieval manipulation decreases renewal and reinstatement of cocaine seeking in the presence of cocaine cues that were not present during extinction training and also decreases cocaine seeking when the procedure commences after 28 days of abstinence. The inhibitory effect of the UCS retrieval manipulation on cocaine-priming-induced reinstatement is mediated by regulation of AMPA-receptor endocytosis in the basolateral amygdala. The UCS memory retrieval-extinction procedure has superior relapse prevention characteristics than the CS memory retrieval-extinction procedure and could be a promising method for decreasing relapse in human addicts.
[Show abstract][Hide abstract] ABSTRACT: A conditioned stimulus (CS) is associated with a fearful unconditioned stimulus (US) in the traditional fear conditioning model. After fear conditioning, the CS-US association memory undergoes the consolidation process to become stable. Consolidated memory enters an unstable state after retrieval and requires the reconsolidation process to stabilize again. Evidence indicates the important role of Rac (Ras-related C3 botulinum toxin substrate) in the acquisition and extinction of fear memory. In the present study, we hypothesized that Rac in the amygdala is crucial for the reconsolidation of auditory and contextual Pavlovian fear memory.
Auditory and contextual fear conditioning and microinjections of the Rac inhibitor NSC23766 were used to explore the role of Rac in the reconsolidation of auditory and contextual Pavlovian fear memory in rats.
A microinjection of NSC23766 into the basolateral amygdala (BLA) but not central amygdala (CeA) or cornu ammonis 1 (CA1) immediately after memory retrieval disrupted the reconsolidation of auditory Pavlovian fear memory. A microinjection of NSC23766 into the CA1 but not BLA or CeA after memory retrieval disrupted the reconsolidation of contextual Pavlovian fear memory.
Our experiments demonstrate that Rac in the BLA is crucial for the reconsolidation of auditory Pavlovian fear memory, whereas Rac in the CA1 is critical for the reconsolidation of contextual Pavlovian fear memory.
No preview · Article · Feb 2014 · Psychopharmacology
[Show abstract][Hide abstract] ABSTRACT: Fear extinction has been extensively studied, but little is known about the molecular processes that underlie the persistence of extinction long-term memory (LTM). We found that microinfusion of norepinephrine (NE) into the CA1 area of the dorsal hippocampus during the early phase (0 h) post-extinction enhanced extinction LTM 2 and 14 days after extinction. Intra-CA1 infusion of NE during the late phase (12 h) post-extinction selectively promoted extinction LTM 14 days after extinction, which was blocked by the β-receptor antagonist propranolol, protein kinase A (PKA) inhibitor Rp-cAMPS, and protein synthesis inhibitors anisomycin and emetine. The phosphorylation levels of PKA, cyclic adenosine monophosphate response element binding protein (CREB) and GluR1, and the membrane GluR1 level was increased by NE during the late phase post-extinction, which was also blocked by propranolol and Rp-cAMPS. These results suggest that the enhancement of extinction LTM persistence induced by NE requires the activation of the β-receptor/PKA/CREB signaling pathway and membrane GluR1 trafficking. Moreover, extinction increased the phosphorylation levels of Erk1/2, CREB, and GluR1, and the membrane GluR1 level during the late phase, and anisomycin/ emetine alone disrupted the persistence of extinction LTM, indicating that the persistence of extinction LTM requires late-phase protein synthesis in the CA1. Propranolol and Rp-cAMPS did not completely disrupt the persistence of extinction LTM, suggesting that another β-receptor/ PKA-independent mechanism underlies the persistence of extinction LTM. Altogether, our results showed that enhancing hippocampal noradrenergic activity during the late phase after extinction selectively promotes the persistence of extinction LTM.Neuropsychopharmacology accepted article preview online, 19 February 2014; doi:10.1038/npp.2014.42.
Full-text · Article · Feb 2014 · Neuropsychopharmacology: official publication of the American College of Neuropsychopharmacology
[Show abstract][Hide abstract] ABSTRACT: Cocaine sensitization and reward are reported to be under the influence of diurnal rhythm. However, no previous studies have reported brain areas that play a role as modulators and underlie the mechanism of diurnal variations in cocaine reward. We examined (1) the diurnal rhythm of glycogen synthase kinase-3β (GSK-3β) activity in the suprachiasmatic nucleus (SCN) and reward-related brain areas in naive rats; (2) the effect of day and night on the acquisition of cocaine-induced conditioned place preference (CPP); (3) the influence of cocaine-induced CPP on GSK-3β activity in the SCN and reward-related brain areas; and (4) the effect of the GSK-3β inhibitor SB216763 microinjected bilaterally into the ventral tegmental area (VTA) on cocaine-induced CPP. A significant diurnal rhythm of GSK-3β activity was found in the SCN and reward-related brain areas, with diurnal variations in cocaine-induced CPP. GSK-3β activity in the SCN and reward-related brain areas exhibited marked diurnal variations in rats treated with saline. GSK-3β activity in rats treated with cocaine exhibited distinct diurnal variations only in the prefrontal cortex and VTA. Cocaine decreased the expression of phosphorylated GSK-3β (i.e. increased GSK-3β activity) only in the VTA in rats trained and tested at ZT4 and ZT16. SB216763 microinjected into the VTA bilaterally eliminated the diurnal variations in cocaine-induced CPP, but did not affect the acquisition of cocaine-induced CPP. These findings suggest that the VTA may be a critical area involved in the diurnal variations in cocaine-induced CPP, and GSK-3β may be a regulator of diurnal variations in cocaine-induced CPP.
Full-text · Article · Jun 2013 · Addiction Biology
[Show abstract][Hide abstract] ABSTRACT: Background: Glutamate N-methyl-D-aspartate (NMDA) receptor antagonists exert fast-acting antidepressant effects, providing a promising way to develop a new classification of antidepressant that targets the glutamatergic system. In the present study, we examined the potential antidepressant action of 7-chlorokynurenic acid (7-CTKA), a glycine recognition site NMDA receptor antagonist, in a series of behavioural models of depression and determined the molecular mechanisms that underlie the behavioural actions of 7-CTKA. Methods: We administered the forced swim test, novelty-suppressed feeding test, learned helplessness paradigm and chronic mild stress (CMS) paradigm in male rats to evaluate the possible rapid antidepressant-like actions of 7-CTKA. In addition, we assessed phospho-glycogen synthase kinase-3β (p-GSK3β) level, mammalian target of rapamycin (mTOR) function, and postsynaptic protein expression in the medial prefrontal cortex (mPFC) and hippocampus. Results: Acute 7-CTKA administration produced rapid antidepressant-like actions in several behavioural tests. It increased p-GSK3β, enhanced mTOR function and increased postsynaptic protein levels in the mPFC. Activation of GSK3β by LY294002 completely blocked the antidepressant-like effects of 7-CTKA. Moreover, 7-CTKA did not produce rewarding properties or abuse potential. Limitations: It is possible that 7-CTKA modulates glutamatergic transmission, thereby causing enduring alterations of GSK3β and mTOR signalling, although we did not provide direct evidence to support this possibility. Thus, the therapeutic involvement of synaptic adaptions engaged by 7-CTKA requires further study. Conclusion: Our findings demonstrate that acute 7-CTKA administration produced rapid antidepressant-like effects, indicating that the behavioural response to 7-CTKA is mediated by GSK3β and mTOR signalling function in the mPFC.
[Show abstract][Hide abstract] ABSTRACT: Rationale and objectives:
Drug reinforcement and the reinstatement of drug seeking are associated with the pathological processing of drug-associated cue memories that can be disrupted by manipulating memory consolidation and reconsolidation. Ras-related C3 botulinum toxin substrate (Rac) is involved in memory processing by regulating actin dynamics and neural structure plasticity. The nucleus accumbens (NAc) and amygdala have been implicated in the consolidation and reconsolidation of emotional memories. Therefore, we hypothesized that Rac in the NAc and amygdala plays a role in the consolidation and reconsolidation of cocaine-associated cue memory.
Conditioned place preference (CPP) and microinjection of Rac inhibitor NSC23766 were used to determine the role of Rac in the NAc and amygdala in the consolidation and reconsolidation of cocaine-associated cue memory in rats.
Microinjections of NSC23766 into the NAc core but not shell, basolateral (BLA), or central amygdala (CeA) after each cocaine-conditioning session inhibited the consolidation of cocaine-induced CPP. A microinjection of NSC23766 into the BLA but not CeA, NAc core, or NAc shell immediately after memory reactivation induced by exposure to a previously cocaine-paired context disrupted the reconsolidation of cocaine-induced CPP. The effect of memory disruption on cocaine reconsolidation was specific to reactivated memory, persisted at least 2 weeks, and was not reinstated by a cocaine-priming injection.
Our findings indicate that Rac in the NAc core and BLA are required for the consolidation and reconsolidation of cocaine-associated cue memory, respectively.
No preview · Article · Mar 2013 · Psychopharmacology
[Show abstract][Hide abstract] ABSTRACT: The intense associative memories that develop between cocaine-paired contexts and rewarding stimuli contribute to cocaine seeking and relapse. Previous studies have shown impairment in cocaine reward memories by manipulating a labile state induced by memory retrieval, but the mechanisms that underlie the destabilization of cocaine reward memory are unknown. In this study, using a Pavlovian cocaine-induced conditioned place preference (CPP) procedure in rats, we tested the contribution of ubiquitin-proteasome system-dependent protein degradation in destabilization of cocaine reward memory. Firstly, we found that polyubiquitinated protein expression levels and polyubiquitinated N-ethylmaleimide-sensitive fusion (NSF) markedly increased 15 min after retrieval while NSF protein levels decreased 1 h after retrieval in the synaptosomal membrane fraction in the nucleus accumbens (NAc) core. We then found that infusion of the proteasome inhibitor lactacystin into the NAc core prevented the impairment of memory reconsolidation induced by the protein synthesis inhibitor anisomycin and reversed the effects of anisomycin on NSF and glutamate receptor 2 (GluR2) protein levels in the synaptosomal membrane fraction in the NAc core. We also found that lactacystin infusion into the NAc core but not shell immediately after extinction training sessions inhibited CPP extinction and reversed the extinction training-induced decrease in NSF and GluR2 in the synaptosomal membrane fraction in the NAc core. Lastly, infusions of lactacystin by itself into the NAc core immediately after each training session or before the CPP retrieval test had no effect on the consolidation and retrieval of cocaine reward memory. These findings suggest that ubiquitin-proteasome system-dependent protein degradation is critical for retrieval-induced memory destabilization.Neuropsychopharmacology accepted article preview online, 29 November 2012; doi:10.1038/npp.2012.243.
No preview · Article · Nov 2012 · Neuropsychopharmacology: official publication of the American College of Neuropsychopharmacology
[Show abstract][Hide abstract] ABSTRACT: Depression is one of the most common and debilitating psychiatric illnesses around the world, but the current antidepressants used to treat depression have many limitations. Progressively more studies have shown that neuropeptide systems are potential novel therapeutic targets for depression. However, whether the neuropeptide trefoil factor 3 (TFF3) participates in the development of depression has not been examined. In the current experiments, we assessed the antidepressant effects of TFF3 using the forced swim test (FST), tail suspension test (TST), and chronic mild stress (CMS) paradigm. Furthermore, we determined the mechanism that underlies the antidepressant-like effects of TFF3 in the rat FST. TFF3 dose-dependently reduced immobility time in both FST and TST. CMS elevated plasma TFF3 and decreased basolateral amygdala (BLA) TFF3 levels in rats, and acute TFF3 (0.1 mg/kg, i.p.) treatment reversed the depressive-like behaviors induced by CMS. Furthermore, TFF3 (0.1 mg/kg, i.p.) significantly increased Fos expression in the BLA, medial prefrontal cortex, and hypothalamus in rats subjected to the FST. Intra-BLA infusions of TFF3 (1 ng/side) exerted rapid antidepressant-like effects in the rat FST. Additionally, acute systemic TFF3 administration increased the level of phosphorylated-Akt (p-Akt) in the BLA. Finally, intra-BLA infusions of LY294002 (5 mM/side), a specific phosphatidylinositol 3-kinase (PI3K) inhibitor, significantly blocked the antidepressant-like effect of TFF3. Our results demonstrated that TFF3 exerts antidepressant-like effects that might be mediated by the PI3K/Akt signaling pathway in the BLA. These findings suggest a novel neuropeptide system target in the development of new antidepressants.
Full-text · Article · Jul 2012 · Neuropsychopharmacology: official publication of the American College of Neuropsychopharmacology
[Show abstract][Hide abstract] ABSTRACT: Drug use and relapse involve learned associations between drug-associated environmental cues and drug effects. Extinction
procedures in the clinic can suppress conditioned responses to drug cues, but the extinguished responses typically reemerge
after exposure to the drug itself (reinstatement), the drug-associated environment (renewal), or the passage of time (spontaneous
recovery). We describe a memory retrieval-extinction procedure that decreases conditioned drug effects and drug seeking in
rat models of relapse, and drug craving in abstinent heroin addicts. In rats, daily retrieval of drug-associated memories
10 minutes or 1 hour but not 6 hours before extinction sessions attenuated drug-induced reinstatement, spontaneous recovery,
and renewal of conditioned drug effects and drug seeking. In heroin addicts, retrieval of drug-associated memories 10 minutes
before extinction sessions attenuated cue-induced heroin craving 1, 30, and 180 days later. The memory retrieval-extinction
procedure is a promising nonpharmacological method for decreasing drug craving and relapse during abstinence.
[Show abstract][Hide abstract] ABSTRACT: Recent studies have shown that a higher consumption of green tea leads to a lower prevalence of depressive symptoms in elderly individuals. However, no studies have explored the antidepressant-like effect of green tea in preclinical models of depression. The aim of this study was to investigate the antidepressant-like effects and the possible mechanism of action of green tea in widely used mouse models of depression. Mice were orally administered green tea polyphenols (GTP; 5, 10 and 20mg/kg) for 7days and assessed in the forced swimming test (FST) and tail suspension test (TST) 60min after the last GTP administration. Serum corticosterone and adrenocorticotrophic hormone (ACTH) levels were also determined immediately after the FST. Green tea polyphenols significantly reduced immobility in both the FST and TST but did not alter locomotor activity in the open field test, suggesting that GTP has antidepressant-like effects, and this action did not induce nonspecific motor changes in mice. Green tea polyphenols also reduced serum corticosterone and ACTH levels in mice exposed to the FST. The present study demonstrated that GTP exerts antidepressant-like effects in a mouse behavioral models of depression, and the mechanism may involve inhibition of the hypothalamic-pituitary-adrenal axis.
No preview · Article · Sep 2011 · Pharmacological Research
[Show abstract][Hide abstract] ABSTRACT: J. Neurochem. (2011) 10.1111/j.1471-4159.2011.07277.x
Exposure to cocaine-associated conditioned stimuli elicits craving and increases the probability of cocaine relapse in cocaine users even after extended periods of abstinence. Recent evidence indicates that cocaine seeking can be inhibited by disrupting the reconsolidation of the cocaine cue memories and that basolateral amygdala (BLA) neuronal activity plays a role in this effect. Previous studies demonstrated that glycogen synthase kinase 3β (GSK-3β) plays a role in the reconsolidation of fear memory. Here, we used a conditioned place preference procedure to examine the role of GSK-3β in the BLA in the reconsolidation of cocaine cue memories. GSK-3β activity in the BLA, but not central amygdala (CeA), in rats that acquired cocaine (10 mg/kg)-induced conditioned place preference increased after re-exposure to a previously cocaine-paired chamber (i.e., a memory reactivation procedure). Systemic injections of the GSK-3β inhibitor lithium chloride after memory reactivation impaired the reconsolidation of cocaine cue memories and inhibited subsequent cue-induced GSK-3β activity in the BLA. Basolateral amygdala, but not central amygdala, injections of SB216763, a selective inhibitor of GSK-3β, immediately after the reactivation of cocaine cue memories also disrupted cocaine cue memory reconsolidation and prevented cue-induced increases in GSK-3β activity in the BLA. The effect of SB216763 on the reconsolidation of cocaine cue memories lasted at least 2 weeks and was not recovered by a cocaine priming injection. These results indicate that GSK-3β activity in the BLA mediates the reconsolidation of cocaine cue memories.
Full-text · Article · Jul 2011 · Journal of Neurochemistry
[Show abstract][Hide abstract] ABSTRACT: Depression is one of the most pervasive and debilitating psychiatric diseases, and the molecular mechanisms underlying the pathophysiology of depression have not been elucidated. Cyclin-dependent kinase 5 (Cdk5) has been implicated in synaptic plasticity underlying learning, memory, and neuropsychiatric disorders. However, whether Cdk5 participates in the development of depressive diseases has not been examined. Using the chronic mild stress (CMS) procedure, we examined the effects of Cdk5/p35 activity in the hippocampus on depressive-like behaviour in rats. We found that CMS increased Cdk5 activity in the hippocampus, accompanied by translocation of neuronal-specific activator p35 from the cytosol to the membrane in the dentate gyrus (DG) subregion. Inhibition of Cdk5 in DG but not in the cornu ammonis 1 (CA1) or CA3 hippocampal subregions inhibited the development of depressive-like symptoms. Overexpression of p35 in DG blocked the antidepressant-like effect of venlafaxine in the CMS model. Moreover, the antidepressants venlafaxine and mirtazapine, but not the antipsychotic aripiprazole, reduced Cdk5 activity through the redistribution of p35 from the membrane to the cytosol in DG. Our results showed that the development of depressive-like behaviour is associated with increased Cdk5 activity in the hippocampus and that the Cdk5/p35 complex plays a key role in the regulation of depressive-like behaviour and antidepressant actions.
Preview · Article · Jun 2011 · The International Journal of Neuropsychopharmacology
[Show abstract][Hide abstract] ABSTRACT: Calcineurin is a serine/threonine protein phosphatase that regulates neurotransmission, neuronal structure and plasticity, and neuronal excitability in mood disorders, including depression. Increasing evidence has suggested that calcineurin is involved in the regulation of depressive-like behavior. However, little is known about the neurobiological mechanisms that underlie the mood-regulating effects of calcineurin. We investigated the potential mechanism by which calcineurin mediates the development of depressive-like behavior and the involvement of calcineurin in the action of antidepressant medication in the chronic mild stress (CMS) model. The results showed that rats exposed to CMS had decreased calcineurin activity, measured by increased phospho-synapsin I S62/67 (pSynapsin) and decreased calcineurin-Aα levels, specifically in the CA3 but not CA1 or dentate gyrus (DG) subfields of the hippocampus. Calcineurin inhibition in the CA3 but not DG by microinfusion of cyclosporine-A (2 μg) induced depressive-like behavior in normal rats and exacerbated depressive-like performance in CMS-treated rats. Additionally, calcineurin inhibition in the CA3 but not DG reversed the antidepressant-like activity of venlafaxine. Calcineurin inhibition in the CA3 also reduced metabotropic glutamate 2/3 receptor (mGluR2/3) expression levels. mGluR2/3 activation by its agonist LY354740 (100 ng) in the CA3 reversed the depressive-like behavior induced by cyclosporine-A administration. Finally, chronic venlafaxine (40 mg/kg) treatment increased calcineurin activity, reflected by decreased pSynapsin and increased calcineurin-Aα protein levels in the CA3 but not CA1 or DG. These findings indicate that CA3 calcineurin signaling probably mediated through mGluR2/3 participates in the development of depression and the behavioral responses to antidepressant treatment.
Full-text · Article · Jun 2011 · Journal of Neurochemistry
[Show abstract][Hide abstract] ABSTRACT: Relapse induced by exposure to cues associated with drugs of abuse is a major challenge to the treatment of drug addiction. Drug seeking can be inhibited by manipulation of the reconsolidation of drug-related memory. Sleep has been proposed to be involved in various memory processes. However, the role of sleep in drug reward memory is not clear. The present study used conditioned place preference to examine the effects of total sleep deprivation on retrieval and reconsolidation of morphine reward memory in rats. Six-hour total sleep deprivation had no effect on the retrieval of morphine reward memory. However, sleep deprivation from 0-6 h, but not 6-12 h, after re-exposure disrupted the reconsolidation of morphine reward memory. This impairment was not attributable to the formation of an aversive associative memory between the drug-paired context and sleep deprivation. Our findings suggest that sleep plays a critical role in morphine reward memory reconsolidation, and sleep deprivation may be a potential non-pharmacotherapy for the management of relapse associated with drug-related memory.
No preview · Article · Apr 2011 · Pharmacology Biochemistry and Behavior
[Show abstract][Hide abstract] ABSTRACT: Protracted cocaine withdrawal can extend for months and contribute to cocaine seeking and relapse. However, no previous studies have reported the manifestation of protracted withdrawal from chronic cocaine in rats. Glycogen synthase kinase 3β (GSK-3β) can phosphorylate PER2, CRY2, Rev-erbα, and BMAL1 in mammals. The circadian rhythmic expression of GSK-3β in reward-related brain areas is unclear. We examined rodent behaviors and circadian disturbances of GSK-3β expression during 30 days of protracted cocaine withdrawal. The behavioral tests included open field, elevated plus maze, weight gain, and sucrose preference tests performed 3, 10, and 30 days after stopping cocaine. At these three assessment points, we collected brain samples every 4h for 24h to examine the circadian rhythmic expression of GSK-3β. Decreased locomotor activity, weight loss, decreased sucrose consumption on day 3, and increased time spent in the open arms of the elevated plus maze on day 10 after cocaine administration were found. Blunted circadian rhythms of phosphorylated GFK-3β (pGSK-3β) persisted for at least 30 days in all examined brain areas, with the exception of 10 days in the suprachiasmatic nucleus (SCN) and nucleus accumbens (NAc). The expression of pGSK-3β decreased in the SCN and increased in the NAc and ventral tegmental area persisted for at least 30 days, whereas in the prefrontal cortex decreased during withdrawal for 10 days but then reversed to abnormally high levels with protracted withdrawal. These long-lasting changes disrupted circadian rhythms and produced abnormal levels of phosphorylated GSK-3β protein in reward-related brain circuits, which may play a role in protracted cocaine withdrawal and contribute to relapse.
Full-text · Article · Mar 2011 · Behavioural brain research