Rationale
Repeated social defeat (RSD) increases the rewarding effects of cocaine in adolescent and adult rodents.
Objective
The aim of the present study was to compare the long-term effects of RSD ...on the conditioned rewarding effects of cocaine and levels of the transcription factors Pitx3 and Nurr1 in the ventral tegmental area (VTA), the dopamine transporter (DAT), the D2 dopamine receptor (D2DR) and precursor of brain-derived neurotrophic factor (proBDNF) signaling pathways, and the tropomyosin-related kinase B (TrkB) receptor in the nucleus accumbens (NAc) in adult and adolescent mice.
Methods
Male adolescent and young adult OF1 mice were exposed to four episodes of social defeat and were conditioned 3 weeks later with 1 mg/kg of cocaine. In a second set of mice, the expressions of the abovementioned dopaminergic and proBDNF and TrkB receptor were measured in VTA and NAc, respectively.
Results
Adolescent mice experienced social defeats less intensely than their adult counterparts and produced lower levels of corticosterone. However, both adult and adolescent defeated mice developed conditioned place preference for the compartment associated with this low dose of cocaine. Furthermore, only adolescent defeated mice displayed diminished levels of the transcription factors Pitx3 in the VTA, without changes in the expression of DAT and D2DR in the NAc. In addition, stressed adult mice showed a decreased expression of proBDNF and the TrkB receptor, while stressed adolescent mice exhibited increased expression of latter without changes in the former.
Conclusion
Our findings suggest that dopaminergic pathways and proBDNF signaling and TrkB receptors play different roles in social defeat-stressed mice exposed to cocaine.
We previously demonstrated that morphine withdrawal induced hyperactivity of the hypothalamus‐pituitary‐adrenocortical axis by activation of noradrenergic pathways innervating the hypothalamic ...paraventricular nucleus (PVN), as evaluated by Fos expression and corticosterone release. The present study was designed to investigate the role of protein kinase C (PKC) in this process by estimating changes in PKCα and PKCγ immunoreactivity, and whether pharmacological inhibition of PKC would attenuate morphine withdrawal‐induced c‐Fos expression and changes in tyrosine hydroxylase (TH) immunoreactivity levels in the PVN and nucleus tractus solitarius/ ventrolateral medulla (NTS/VLM). Dependence on morphine was induced in rats by 7 day s.c. implantation of morphine pellets. Morphine withdrawal was induced on day 8 by an injection of naloxone. The protein levels of PKCα and γ were significantly down‐regulated in the PVN and NTS/VLM from the morphine‐withdrawn rats. Morphine withdrawal induced c‐Fos expression in the PVN and NTS/VLM, indicating an activation of neurons in those nuclei. TH immunoreactivity was increased in the NTS/VLM after induction of morphine withdrawal, whereas there was a decrease in TH levels in the PVN. Infusion of calphostin C, a selective protein kinase C inhibitor, produced a reduction in the morphine withdrawal‐induced c‐Fos expression. Additionally, the changes in TH levels in the PVN and NTS/VLM were significantly modified by calphostin C. The present results suggest that activated PKC in the PVN and catecholaminergic brainstem cell groups may be critical for the activation of the hypothalamic‐pituitary adrenocortical axis in response to morphine withdrawal.
Drug withdrawal-associated aversive memories trigger relapse to drug-seeking behavior. Corticotrophin-releasing factor (CRF) is an important mediator of the reinforcing properties of drugs of abuse. ...However, the involvement of CRF1 receptor (CRF1R) in aversive memory induced by opiate withdrawal has yet to be elucidated. We used the conditioned-place aversion (CPA) paradigm to evaluate the role of CRF1R on opiate withdrawal memory acquisition, along with plasticity-related processes that occur after CPA within the basolateral amygdala (BLA) and dentate gyrus (DG). Male mice were rendered dependent on morphine and injected acutely with naloxone before paired to confinement in a naloxone-associated compartment. The CPA scores as well as the number of TH-positive neurons (in the NTS-A2 noradrenergic cell group), and the expression of the transcription factors Arc and pCREB (in the BLA and DG) were measured with and without CRF1R blockade.
Mice subjected to conditioned naloxone-induced morphine withdrawal robustly expressed CPA. Pre-treatment with the selective CRF1R antagonist CP-154,526 before naloxone conditioning session impaired morphine withdrawal-induced aversive memory acquisition. CP-154,526 also antagonized the enhanced number of TH-positive neurons in the NTS-A2 that was seen after CPA. Increased Arc expression and Arc-pCREB co-localization were seen in the BLA after CPA, which was not modified by CP-154,526. In the DG, CPA was accompanied by a decrease of Arc expression and no changes in Arc-pCREB co-localization, whereas pre-treatment with CP-154,526 induced an increase in both parameters. These results indicate that CRF-CRF1R pathway could be a critical factor governing opiate withdrawal memory storage and retrieval and might suggest a role for TH-NA pathway in the effects of withdrawal on memory. Our results might indicate that the blockade of CRF1R could represent a promising pharmacological treatment strategy approach for the attenuation of the relapse to drug-seeking/taking behavior triggered by opiate withdrawal-associated aversive memories.
•A role of CRF1R in conditioned place aversion in morphine-dependent mice is proposed.•CRF-CRF1R pathway is necessary for the effect of opiate withdrawal on memory retrieval.•TH-NA pathway role in the effects of withdrawal on memory would involve CRF1R.
Extinction period of positive affective memory of drug taking and negative affective memory of drug withdrawal, as well as the different response of men and women might be important for the clinical ...treatment of drug addiction. We investigate the role of corticotropin releasing factor receptor type one (CRF1R) and the different response of male and female mice in the expression and extinction of the aversive memory.
We used genetically engineered male and female mice lacking functional CRF1R. The animals were rendered dependent on morphine by intraperitoneally injection of increasing doses of morphine (10-60 mg/kg). Negative state associated with naloxone (1 mg/kg s.c.)-precipitated morphine withdrawal was examined by using conditioned place aversion (CPA) paradigm. No sex differences for CPA expression were found in wild-type (n = 29) or CRF1R knockout (KO) mice (n = 29). However, CRF1R KO mice presented less aversion score than wild-type mice, suggesting that CRF1R KO mice were less responsive than wild-type to continuous associations between drug administration and environmental stimuli. In addition, CPA extinction was delayed in wild-type and CRF1R KO male mice compared with females of both genotypes. The genetic disruption of the CRF1R pathway decreased the period of extinction in males and females suggesting that CRF/CRF1R is implicated in the duration of aversive memory. Our results also showed that the increase in adrenocorticotropic hormone (ACTH) levels observed in wild-type (n = 11) mice after CPA expression, were attenuated in CRF1R KO mice (n = 10). In addition, ACTH returned to the baseline levels in males and females once CPA extinction was finished.
These results suggest that, at least, CPA expression is partially due to an increase in plasma ACTH levels, through activation of CRF1R, which can return when CPA extinction is finished.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Accumulating evidence indicates that dopamine (DA) D3 receptor (DAD3R) antagonists appear highly promising in attenuating cocaine reward and relapse in preclinical models of addiction. In the present ...study, we investigated the effects of the selective DAD3R antagonist SB-277011-A on the reinstatement of cocaine-induced conditioned place preference (CPP) produced by a priming dose of cocaine, by social defeat stress and by two kinds of physiological stressors (restraint and tail pinch) in male adult mice. We also explored reinstatement-related plasma corticosterone levels (as marker of stress response) and the effects of blocking DAD3R. Administration of SB-277011-A (24 or 48 mg/kg i.p.) did not modify conditioned reinstatement of cocaine seeking triggered by cocaine prime. By contrast, we found that the vulnerability to reinstatement of the CPP of defeated animals that have undergone CPP extinction was abolished by the DAD3R antagonist (24 mg/kg) given 30 min before the test session. Reactivation of the CPP response produced by physiological stress stimuli was also attenuated by SB-277011-A (48 mg/kg i.p.). On the other hand, the blockade of DAD3R significantly prevented the increased corticosterone release during reinstatement of cocaine-induced CPP that was seen in social defeated animals, in mice suffering physiological stress and after cocaine prime. Present results demonstrate a modulation by DAD3R of the reactivation of the incentive value of cocaine-associated cues induced by social and physiological stress stimuli, which was associated to a glucocorticoid-dependent mechanism. Our results also point to a possible potential therapeutic use of selective DAD3R antagonists for the prevention of stress-induced cocaine-seeking and relapse.
•DAD3R is involved in the reinstatement of cocaine-induced place preference provoked by social and physiological stressful stimuli•DAD3R does not participate in the reinstatement of cocaine-induced place preference provoked by a high dose of the drug•DAD3R blockade prevent the increased corticosterone release during reinstatement of cocaine-induced CPP during stress.•Corticosterone release after cocaine prime-induced reinstatement is not modulated by DAD3R
Corticotropin-releasing factor (CRF) acts as neuro-regulator of the behavioral and emotional integration of environmental and endogenous stimuli associated with drug dependence. Thioredoxin-1 (Trx-1) ...is a functional protein controlling the redox status of several proteins, which is involved in addictive processes. In the present study, we have evaluated the role of CRF1 receptor (CRF1R) in the rewarding properties of morphine by using the conditioned place preference (CPP) paradigm. We also investigate the effects of the CRF1R antagonist, CP-154,526, on the morphine CPP-induced activation of CRF neurons, CREB phosphorylation and Trx expression in paraventricular nucleus (PVN) and dentate gyrus (DG) of the mice brain. CP-154,526 abolished the acquisition of morphine CPP and the increase of CRF/pCREB positive neurons in PVN. Moreover, this CRF1R antagonist prevented morphine-induced CRF-immunoreactive fibers in DG, as well as the increase in pCREB expression in both the PVN and DG. In addition, morphine exposure induced an increase in Trx-1 expression in DG without any alterations in PVN. We also observed that the majority of pCREB positive neurons in DG co-expressed Trx-1, suggesting that Trx-1 could activate CREB in the DG, a brain region involved in memory consolidation. Altogether, these results support the idea that CRF1R antagonist blocked Trx-1 expression and pCREB/Trx-1 co-localization, indicating a critical role of CRF, through CRF1R, in molecular changes involved in morphine associated behaviors.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
BACKGROUND AND PURPOSE
Exposure to drugs of abuse or stress results in adaptation in the brain involving changes in gene expression and transcription factors. Morphine withdrawal modulates gene ...expression through various second‐messenger signal transduction systems. Here, we investigated changes in activation of the transcription factor, cAMP‐response element binding protein (CREB), in the hypothalamic paraventricular nucleus (PVN) and the kinases that may mediate the morphine withdrawal‐triggered activation of CREB and the response of the hypothalamic‐pituitary‐adrenocortical (HPA) axis after naloxone‐induced morphine withdrawal.
EXPERIMENTAL APPROACH
The effects of morphine dependence and withdrawal, phosphorylated CREB (pCREB), corticotrophin‐releasing factor (CRF) expression in the PVN and HPA axis activity were measured using immunoblotting, immunohistochemistry and radioimmunoassay in controls and in morphine‐dependent rats, withdrawn with naloxone and pretreated with vehicle, calphostin C, chelerythrine (inhibitors of protein kinase C (PKC) or SL‐327 inhibitor of extracellular signal regulated kinase (ERK) kinase. In addition, changes in PKCα and PKCγ immunoreactivity were measured after 60 min of withdrawal.
KEY RESULTS
In morphine‐withdrawn rats, pCREB immunoreactivity was increased within CRF immunoreactive neurons in the PVN and plasma corticosterone levels were raised. SL‐327, at doses that reduced the augmented pERK levels in the PVN, did not attenuate the rise in pCREB immunoreactivity or plasma corticosterone secretion. In contrast, PKC inhibition reduced the withdrawal‐triggered rise in pCREB, pERK1/2 and corticosterone secretion.
CONCLUSIONS AND IMPLICATIONS
PKC mediated, in part, both CREB activation and the HPA response to morphine withdrawal. The ERK kinase/ERK pathway might not be necessary for either activation of CREB or HPA axis hyperactivity.
The content of corticotropin‐releasing factor (CRF) and arginine vasopressin (AVP) in the hypothalamic paraventricular nucleus (PVN) increases during chronic morphine treatment. Because these ...experiments cannot distinguish between increased synthesis or reduced release, the present study measured changes in CRF and AVP mRNAs in the PVN by in situ hybridization. Concomitantly, changes in noradrenaline turnover in the PVN and changes in plasma corticosterone release were determined. Male rats were implanted with placebo (naive) or morphine pellets for 7 days. On day 7, groups of rats received an acute injection of either saline i.p. or morphine (30 mg/kg, i.p.). Acute morphine injection did not change the total size of the labelled area for CRF mRNA in the PVN of naive or morphine‐pelleted rats, indicating that the number of CRF‐containing neurones was unchanged. On the other hand, in rats chronically treated with morphine, the intensity of labelling for CRF mRNA was significantly reduced, suggesting a decrease in the synthesis of CRF. In placebo rats, injection of saline or morphine did not affect the surface hybridized for AVP mRNA. By contrast, in the morphine‐group injected with saline, there was a significant reduction in the number of labelled neurones, measured by the size of labelled area. Similarly, there was a decrease in intensity of AVP mRNA expression in the parvocellular and magnocellular neurones of the PVN in the morphine‐group injected with saline, suggesting a decreased synthesis of AVP in these neurones. In parallel with the decrease in the expression of CRF and AVP mRNAs in the PVN, there was a pronounced decrease in noradrenaline turnover and in the release of corticosterone in the morphine‐pelleted rats. In conclusion, present results show that, in addition to modifications in corticosterone secretion and in noradrenaline turnover, chronic morphine administration produces a reduction in the synthesis of CRF and AVP.
Background and Purpose
Alterations in transcription factors that regulate the development and maintenance of dopamine (DA) neurons (such as Nurr1 and Pitx3) play an important role in the pathogenesis ...of addiction diseases. We have examined the effects of acute and chronic morphine and morphine withdrawal on TH expression and activity as well as expression of Nurr1, Pitx3 and Ago2 in the ventral tegmental area (VTA) and nucleus accumbens (NAc) of the rat.
Experimental Approach
Rats were injected acutely with morphine and decapitated 1 or 2 h later. Another set of rats were made dependent on morphine by implantation of two morphine pellets. Precipitated withdrawal was induced by injection of naloxone. Ago2, Pitx3, Nurr1, total TH (tTH), TH phosphorylated at Ser31 and at Ser40, and 3,4‐Dihydroxyphenylacetic acid, and DA determination in the VTA and/or NAc were measured using immunoblotting, HPLC and immunofluorescence.
Key Results
Acute morphine produced a marked increase in TH activity and DA turnover in the NAc, concomitantly with increased Nurr1 and Pitx3 expression in the VTA. In contrast, precipitated morphine withdrawal decreased TH activation, TH expression and did not increase DA turnover in the NAc. These effects paralleled decreases in Ago2 expression, which was accompanied by increased Nurr1 and Pitx3, TH activity and normalized TH protein levels in the VTA.
Conclusions and Implications
The combined decrease in Ago2 and increases in Nurr1 and Pitx3 might represent some of the mechanisms that served to protect against accumbal TH regulation observed in morphine withdrawn rats, which may be critical for DA bioavailability to influence behaviour.
This study examined the involvement of the brain stress system in the reinforcing effects of morphine. One group of mice was conditioned to morphine using the conditioned place preference (CPP) ...paradigm and the other group received morphine in a home-cage (non-conditioned). Adrenocorticotropic hormone and corticosterone levels were measured by radioimmunoassay; phospho (p) CREB expression and the number of corticotropin-releasing factor (CRF) neurons and fibres were measured by immunohistochemistry in different brain areas. We observed that the number of CRF neurons in the paraventricular nucleus (PVN) was increased after morphine-induced CPP, which was paralleled with enhanced CRF-immunoreactivity fibres in the nucleus tractus solitarius (NTS) and ventral tegmental area (VTA) vs. home-cage group injected with morphine. Morphine exposure induced an increase in CREB phosphorylated at Ser133 in the PVN and central amygdale (CeA), whereas mice exhibiting morphine CPP had higher levels of pCREB in the PVN, CeA and bed nucleus of the stria terminalis (BNST). We also found that most of the CRF-positive neurons in the PVN, CeA and BNST co-express pCREB after morphine CPP expression, suggesting that the drug-associated environmental contexts can elicit neuronal activity in the brain stress system. From the present results it is clear that exposure to a drug-associated context remains a potent activator of signalling pathways leading to CRF activation in the brain stress system.
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