Changes in CREB and deltaFosB are associated with the behavioural sensitization induced by methylenedioxypyrovalerone

Sex differences in the effects of N-ethylpentylone in young CD1 mice: Insights on behaviour, thermoregulation and early gene expression

BACKGROUND AND PURPOSE

New psychoactive substances such as N-ethylpentylone (NEP) are continuously emerging in the illicit drug market, and knowledge of their effects and risks, which may vary between sexes, is scarce. Our present study compares some key effects of NEP in male and female mice.

EXPERIMENTAL APPROACH

Psychostimulant, rewarding and reinforcing effects were investigated by tracking locomotor activity, conditioned place preference (CPP) paradigm and through a self-administration (SA) procedure, respectively, in CD1 mice. Moreover, the expression of early genes (C-fos, Arc, Csnk1e, Pdyn, Pp1r1b and Bdnf in addiction-related brain areas) was assessed by qPCR. Finally, serum and brain levels of NEP were determined by UHPLC-MS/MS.

KEY RESULTS

NEP-treated males experimented locomotor sensitisation and showed higher and longer increases in locomotion as well as higher hyperthermia after repeated administration than females. Moreover, while preference score in the CPP was similar in both sexes, extinction occurred later, and reinstatement was more easily established for males. Female mice self-administered more NEP than males at a higher dose. Differences in early gene expression (Arc, Bdnf, Csnk1e and Ppp1r1b) were found, but the serum and brain NEP levels did not differ between sexes.

CONCLUSION AND IMPLICATIONS

Our results suggest that male mice are more sensitive to NEP psychostimulant and rewarding effects. These differences may be attributed to different early gene expression but not to pharmacokinetic factors. Moreover, males appear to be more vulnerable to the hyperthermic effects of NEP, while females might be more prone to NEP abuse.

Perfluorononanoic Acid Induces Neurotoxicity via Synaptogenesis Signaling in Zebrafish

Perfluorononanoic acid (PFNA), commonly used as an alternative polyfluorinated compound (PFC) of perfluorooctanoic acid (PFOA), has been widely detected in the aquatic environment. Previous ecotoxicological and epidemiological results suggested that some neurobehavioral effects were associated with PFC exposure; however, the ecological impacts and underlying neurotoxicity mechanisms remain unclear, particularly in aquatic organisms during sensitive, early developmental stages. In this study, zebrafish embryos were exposed to environmentally relevant concentrations of PFNA for 120 h, and the neurological effects of PFNA were comprehensively assessed using transcriptional, biochemical, morphological, and behavioral assays. RNA sequencing and advanced bioinformatics analyses predicted and characterized the key biological processes and pathways affected by PFNA exposure, which included the synaptogenesis signaling pathway, neurotransmitter synapse, and CREB signaling in neurons. Neurotransmitter levels (acetylcholine, glutamate, 5-hydroxytryptamine, γ-aminobutyric acid, dopamine, and noradrenaline) were significantly decreased in zebrafish larvae, and the Tg(gad67:GFP) transgenic line revealed a decreased number of GABAergic neurons in PFNA-treated larvae. Moreover, the swimming distance, rotation frequency, and activity degree were also significantly affected by PFNA, linking molecular-level changes to behavioral consequences.

Repeated administration of N-ethyl-pentedrone induces increased aggression and impairs social exploration after withdrawal in mice

N-ethyl-pentedrone (NEPD, 2-(ethylamino)-1-phenyl-1-pentanone) is one of the latest synthetic cathinone derivatives that emerged into the illicit drug market. This drug has psychostimulant properties and has been related with several intoxications and even fatalities. However, information about the consequences of its acute and repeated consumption is lacking. Thus, the aim of our study was to investigate the behavioral effects after both acute and repeated NEPD exposure as well as the neurochemical changes. Male OF1 mice were treated with an acute dose (1, 3 or 10 mg/kg, i.p.) or received repeated injections of these doses (twice/day, 5 days) of NEPD. Shortly after drug-exposure or during drug-withdrawal, anxiety-like behavior, aggressiveness, social interaction, depressive-like symptoms, body weight and temperature were assessed. Also, monoamine synthesis enzymes, levels of neurotransmitters and their precursors and main metabolites, as well as ΔFosB, were determined in striatum and prefrontal cortex from post-mortem tissue. Acute administration of NEPD induced anxiolytic effects and reduced social exploration whereas during withdrawal after repeated administration the anxiolytic effect had vanished, and the reduced social exploration was still present and accompanied with increased aggressive behavior. Moreover, NEPD (10 mg/kg) induced slight hyperthermia and reduced weight gain during the repeated administration, whereas increased locomotor activity and lack of depressive symptoms were found during withdrawal. This was accompanied by increased plasma corticosterone and decrease in striatal dopamine. Finally, the long-lasting and robust increase in ΔFosB levels found in striatum after NEPD chronic exposure suggests a high risk of dependence. The increased aggressivity and locomotor activity, together with this potential of inducing dependence justify a warning about the risks of consumption of NEPD if translated to humans.

Behavioural and neurochemical effects after repeated administration of N-ethylpentylone (ephylone) in mice

N-ethyl-pentylone (NEP), also known as 'ephylone' and N-ethylnorpentylone, has been identified as one of the most recent novel psychostimulants to emerge into the illicit drug market and it has been associated with some intoxications and even fatalities. However, little is known about the consequences of its repeated consumption as well as the role of the monoaminergic system in such consequences. Thus, the aim of our study was to investigate the neurochemical profile and the behavioural effects after both acute and repeated NEP exposure. Male OF1 mice were acutely (1, 3, 10 mg/kg, i.p.) or repeatedly (1, 3, 10 mg/kg, i.p., 5 days, twice/day) exposed to NEP, and anxiety-like behaviour, aggressiveness, social interaction, depressive-like symptoms, body temperature, changes in monoaminergic enzymes and neurotransmitters levels as well as ΔFosB in striatum and prefrontal cortex (PFC) from post-mortem tissue were analysed short after drug-exposure or during drug-withdrawal. Acute administration of NEP induced anxiolytic effects but also an aggressive behaviour and social exploration deficits in mice, which persist during NEP-withdrawal. Moreover, NEP induced hyperthermia as well as depressive-like symptoms after repeated administrations that may be related to the decrease in serotonin and noradrenaline levels observed in striatum and PFC. Finally, the long-term increase in ΔFosB levels in striatum after NEP chronic exposure points to a high risk of dependence. Altogether indicates that NEP consumption induces different neurological and neuropsychiatric disorders accompanied by changes in the monoaminergic system, posing a threat to public health.

The cognitive and behavioral effects of D-amphetamine and nicotine sensitization in adult zebrafish

BACKGROUND

Zebrafish are growing in use as a model for understanding drug dependence and addiction. Sensitization paradigms have been a useful tool in identifying mechanisms involved in drug-induced behavioral and neurological changes, but in zebrafish have tended to focus on locomotor, rather than cognitive, endpoints.

METHODS

Here, we used a novel method, the FMP Y-maze, which measures continuous performance through a series of repeated binary choices (L vs R), to establish a model for assessing parameters associated with psychostimulant-induced behavioral and cognitive sensitization in adult zebrafish.

RESULTS

Repeat, intermittent exposure to d-amphetamine (AMPH) for 14 days increased alternations (LRLR) in the maze, suggesting improved working memory, which was enhanced further following drug challenge after a short withdrawal period, suggesting behavioral sensitization. However, this cognitive enhancement coincided with a reduction in the use of other exploration strategies, hypolocomotion, and inhibition of cognitive flexibility. Like AMPH, exposure to nicotine (NIC) increased alternations following drug challenge after chronic treatment. Repeat NIC exposure appeared to induce both cognitive and psychomotor sensitization, as evidenced by increased working memory performance (alternations) and locomotor activity, without negatively impacting other search strategies or cognitive flexibility.

CONCLUSION

Chronic treatment with AMPH or NIC boosts cognitive performance in adult zebrafish. Cognitive sensitization occurred with both drugs, resulting in enhanced working memory; however, repeat AMPH exposure, following a withdrawal period, resulted in inhibited cognitive flexibility, an effect not evident with repeat NIC exposure. Cognitive and behavioral sensitization paradigms in zebrafish could serve as a useful tool for assessing cognitive states which result in cognitive enhancing or impairing effects of drugs.

Cross-reinstatement between 3,4-methylenedioxypyrovalerone (MDPV) and cocaine using conditioned place preference

3,4-Methylenedioxypyrovalerone (MDPV) is a new psychoactive substance (NPS) considered to be a cocaine-like psychostimulant. The substitution of an established illicit drug as cocaine with an NPS is a pattern of use reported among drug users. The aim of this study was to investigate the relationship between cocaine and MDPV in the reinstatement of the conditioned place preference (CPP) paradigm, in order to establish whether there is cross-reinstatement between the two psychostimulants. Four experimental groups of male OF1 mice were subjected to the CPP paradigm: MDPV-MDPV, Cocaine-Cocaine, Cocaine-MDPV, and MDPV-Cocaine. The first drug refers to the substance with which the animals were conditioned (cocaine 10 mg/kg or MDPV 2 mg/kg) and the s to the substance with which preference was reinstated. In parallel, G9a, ΔFosB, CB1 receptor, CDK5, Arc and c-Fos were determined in ventral striatum. MDPV induced CPP at doses from 1 to 4 mg/kg. Although 2 mg/kg MDPV induced a stronger psychostimulant effect than 10 mg/kg cocaine, both doses seemed to be equivalent in their rewarding properties. However, memories associated with MDPV required more time to be extinguished. MDPV and cocaine restore drug-seeking behavior with respect to each other, although relapse into drug-taking is always more pronounced with the conditioning drug. The fact that MDPV-treated mice show increased ΔFosB protein levels correlates with its longer extinction time and points to the activation of neuroplasticity mechanisms that persist for at least 12 days. Moreover, in these animals, a priming-dose of cocaine can trigger significant neuroplasticity, implying a high vulnerability to cocaine abuse.

The effects of acute and repeated methylenedioxypyrovalerone (MDPV) administration on striatal transcriptome networks in male long evans rats

The psychoactive drug methylenedioxypyrovalerone (MDPV) elicits feelings of euphoria and hyperexcitability, but can also result in paranoia, agitation, and depression by unknown mechanisms. We identified molecular networks in the rat striatum that were affected by single or repeated exposure to MDPV. Male Long Evans rats were injected with either saline or MDPV (1 mg/kg) (single or repeated MDPV) over 5 days. To distinguish the effects of repeated MDPV from a single exposure, an additional group received saline over 4 days and then MDPV on the 5th day. Twenty-four hours after the final injection, the left dorsal striatum was processed for transcriptomics. The transcriptome response was subtle after 24 h, and a single gene passed an FDR correction (LOC103691845) following repeated MDPV treatment. Gene set and subnetwork enrichment analyses were conducted to improve data interpretation from a network perspective. Consistent with the mode of action of MDPV, networks related to the nigrostriatal dopaminergic system were altered in the rat striatum. Transcriptional networks related to cognition, short and long-term memory, and synaptic transmission were over-represented in the striatum of rats repeatedly injected with MDPV. This study identifies potential transcriptional networks altered by single or repeated MDPV exposure, which can be interrogated further to elucidate molecular mechanisms underlying cathinone abuse.

Pharmacological NOS-1 Inhibition Within the Hippocampus Prevented Expression of Cocaine Sensitization: Correlation with Reduced Synaptic Transmission

Behavioral sensitization to psychostimulants hyperlocomotor effect is a useful model of addiction and craving. Particularly, cocaine sensitization in rats enhanced synaptic plasticity within the hippocampus, an important brain region for the associative learning processes underlying drug addiction. Nitric oxide (NO) is a neurotransmitter involved in both, hippocampal synaptic plasticity and cocaine sensitization. It has been previously demonstrated a key role of NOS-1/NO/sGC/cGMP signaling pathway in the development of cocaine sensitization and in the associated enhancement of hippocampal synaptic plasticity. The aim of the present investigation was to determine whether NOS-1 inhibition after development of cocaine sensitization was able to reverse it, and to characterize the involvement of the hippocampus in this phenomenon. Male Wistar rats were administered only with cocaine (15 mg/kg/day i.p.) for 5 days. Then, animals received 7-nitroindazole (NOS-1 inhibitor) either systemically for the next 5 days or a single intra-hippocampal administration. Development of sensitization and its expression after withdrawal were tested, as well as threshold for long-term potentiation in hippocampus, NOS-1, and CREB protein levels and gene expression. The results showed that NOS-1 protein levels and gene expression were increased only in sensitized animals as well as CREB gene expression. NOS-1 inhibition after sensitization reversed behavioral expression and the highest level of hippocampal synaptic plasticity. In conclusion, NO signaling within the hippocampus is critical for the development and expression of cocaine sensitization. Therefore, NOS-1 inhibition or NO signaling pathways interferences during short-term withdrawal after repeated cocaine administration may represent plausible pharmacological targets to prevent or reduce susceptibility to relapse.

Acute and chronic neurobehavioral effects of the designer drug and bath salt constituent 3,4-methylenedioxypyrovalerone in the rat

BACKGROUND

The substantial increase in use of 3,4-methylenedioxypyrovalerone (MDPV), a popular recreational synthetic cathinone, has raised legitimate questions about its behavioral consequences and abuse liability.

AIMS

The aim of this study was to study MDPV-induced neurobehavioral effects in the rat, using different paradigms traditionally developed to study drug-attributed addictive properties.

METHODS

Different patterns of intraperitoneal 3 mg/kg MDPV administration were investigated. Consequences on rat horizontal locomotion and behavior of acute, intermittent (once daily dosing over 10 days), and binge (three-time daily dosing for 3 days) MDPV administration as well as challenge after 10 day MDPV withdrawal were studied. The dopamine receptor-D1 antagonist, SCH23390, was bilaterally infused in the nucleus accumbens to determine the role of D1-receptors in MDPV-related effects on the associative memory recall using the conditioned place preference paradigm. In addition, in a separate experience using western blot, we investigated the effects of chronic MDPV administration (four injections during 24 h) on ΔFosB expression in the nucleus accumbens, caudate putamen, and prefrontal cortex.

RESULTS

Acute MDPV administration increased stereotypies and open arm entries in the elevated plus maze while SCH23390 abolished MDPV-induced enhancing effects on memory consolidation. Intermittent MDPV administration resulted in sensitization of MDPV-induced locomotor effects and tolerance during the following challenge. With binge MDPV administration, locomotor activity was not altered despite tolerance onset after challenge. SCH23390 abolished MDPV-induced conditioned place preference. Chronic MDPV administration induced ΔFosB accumulation in the nucleus accumbens, caudate putamen, and prefrontal cortex.

CONCLUSIONS

Our findings clearly show that MDPV produces profound behavioral alterations mediated by the activation of the dopaminergic system similarly to other amphetamines.

Effects of MDPV on dopamine transporter regulation in male rats. Comparison with cocaine

RATIONALE

MDPV (3,4-methylenedioxypyrovalerone) is a synthetic cathinone present in bath salts. It is a powerful psychostimulant and blocker of the dopamine transporter (DAT), like cocaine. It is known that acute exposure to psychostimulants induces rapid changes in DAT function.

OBJECTIVES

To investigate the effects of MDPV on DAT function comparing with cocaine.

METHODS

Binding of [³H]WIN 35428 was performed on PC 12 cells treated with MDPV and washed. Rat striatal synaptosomes were incubated with MDPV or cocaine (1 μM) for 1 h and [³H]dopamine (DA) uptake was performed. Also, different treatments with MDPV or cocaine were performed in Sprague-Dawley rats to assess locomotor activity and ex vivo [³H]DA uptake.

RESULTS

MDPV increased surface [³H]WIN 35428 binding on PC 12 cells. In vitro incubation of synaptosomes with MDPV produced significant increases in V_max and K_M for [³H]DA uptake. In synaptosomes from MDPV- (1.5 mg/kg, s.c.) and cocaine- (30 mg/kg, i.p.) treated rats, there was a significantly higher and more persistent increase in [³H]DA uptake in the case of MDPV than cocaine. Repeated doses of MDPV developed tolerance to this DAT upregulation and 24 h after the 5-day treatment with MDPV, [³H]DA uptake was reduced. However, a challenge with the same drugs after withdrawal recovered the DAT upregulation by both drugs and showed an increased response to MDPV vs the first dose. At the same time, animals were sensitized to the stereotypies induced by both psychostimulants.

CONCLUSIONS

MDPV induces a rapid and reversible functional upregulation of DAT more powerfully and lasting than cocaine.

7,8-Dihydroxyflavone blocks the development of behavioral sensitization to MDPV, but not to cocaine: Differential role of the BDNF-TrkB pathway

3,4-Methylenedioxypyrovalerone (MDPV) acts as a dopamine transporter blocker and exerts powerful psychostimulant effects. In this study we aimed to investigate the bidirectional cross-sensitization between MDPV and cocaine, as well as to evaluate the role of the BDNF-TrkB signaling pathway in the development of locomotor sensitization to both drugs. Mice were treated with MDPV (1.5 mg/kg) or cocaine (10 or 15 mg/kg) once daily for 5 days. After withdrawal (10 days), animals were challenged with cocaine (8 mg/kg) or MDPV (1 mg/kg). For biochemical determinations, MDPV (1.5 mg/kg) or cocaine (15 mg/kg) were administered acutely or repeatedly, and BDNF, D3R and G9a transcription levels as well as pro- and mature BDNF protein levels were determined. Our results demonstrate that repeated administration of MDPV or cocaine sensitizes to cocaine and MDPV locomotor effects. After an acute or a repeated exposure to MDPV, cortical mRNA BDNF levels were increased, while a decrease in mBDNF protein levels in the nucleus accumbens 2 h after repeated exposure was evidenced. Interestingly, such decline was involved in the development of locomotor sensitization, thus the pretreatment with 7,8-dihydroxyflavone (10 mg/kg), a TrkB agonist, blocked the development of sensitization to MDPV but not to cocaine, for which no changes in the BDNF-TrkB signaling pathway were observed at early withdrawal. In conclusion, a bidirectional cross-sensitization between MDPV and cocaine was evidenced. Our findings suggest that decreased BDNF-TrkB signaling has an important role in the behavioral sensitization to MDPV, pointing TrkB modulation as a target to prevent MDPV sensitization.

Behavioural, Pharmacokinetic, Metabolic, and Hyperthermic Profile of 3,4-Methylenedioxypyrovalerone (MDPV) in the Wistar Rat

3,4-methylenedioxypyrovalerone (MDPV) is a potent pyrovalerone cathinone that is substituted for amphetamines by recreational users. We report a comprehensive and detailed description of the effects of subcutaneous MDPV (1-4 mg/kg) on pharmacokinetics, biodistribution and metabolism, acute effects on thermoregulation under isolated and aggregated conditions, locomotion (open field) and sensory gating (prepulse inhibition, PPI). All studies used male Wistar rats. Pharmacokinetics after single dose of 2 mg/kg MDPV was measured over 6 h in serum, brain and lungs. The biotransformation study recorded 24 h urinary levels of MDPV and its metabolites after 4 mg/kg. The effect of 2 mg/kg and 4 mg/kg on body temperature (°C) was measured over 12 h in group- vs. individually-housed rats. In the open field, locomotion (cm) and its spatial distribution were assessed. In PPI, acoustic startle response (ASR), habituation, and PPI were measured (AVG amplitudes). In behavioural experiments, 1, 2, or 4 mg/kg MDPV was administered 15 or 60 min prior to testing. Thermoregulation and behavioural data were analysed using factorial analysis of variance (ANOVA). Peak concentrations of MDPV in sera, lung and brain tissue were reached in under 30 min. While negligible levels of metabolites were detected in tissues, the major metabolites in urine were demethylenyl-MDPV and demethylenyl-methyl-MDPV at levels three-four times higher than the parent drug. We also established a MDPV brain/serum ratio ~2 lasting for ~120 min, consistent with our behavioural observations of locomotor activation and disrupted spatial distribution of behaviour as well as moderate increases in body temperature (exacerbated in group-housed animals). Finally, 4 mg/kg induced stereotypy in the open field and transiently disrupted PPI. Our findings, along with previous research suggest that MDPV is rapidly absorbed, readily crosses the blood-brain barrier and is excreted primarily as metabolites. MDPV acts as a typical stimulant with modest hyperthermic and psychomimetic properties, consistent with a primarily dopaminergic mechanism of action. Since no specific signs of acute toxicity were observed, even at the highest doses used, clinical care and harm-reduction guidance should be in line with that available for other stimulants and cathinones.

Depletion of D3 dopamine receptor affects methamphetamine-induced expression patterns of Pde4b and Atf3

The role of the D3 dopamine receptor (D3R) and the specific molecular mechanisms underlying the regulation of D3R via the cAMP signaling pathway in methamphetamine (METH) addiction are still unclear. Here, we measured changes in Pde4b and Atf3 in the cAMP signaling pathway of dopaminergic system components, including the nucleus accumbens (NAc), caudate putamen (CPu) and hippocampus (Hip), in D3R knockout mice(D3R-/-) 1h and 24h after METH-induced behavioral sensitization. We found that knocking out D3R attenuated METH-induced behavioral sensitization, and Pde4b and Atf3 exhibited different expression patterns in brain regions in response to METH. Knocking out D3R suppressed the METH-induced increase in Pde4b in the Hip of mice 24h after the final METH injection and augmented the METH-induced increase in Atf3 in the CPu of mice 1h after the final METH injection. Our study suggests that D3R knockout controls METH-induced behavioral sensitization via regulation of Pde4b and Atf3 in different brain regions. Furthermore, the responses of Pde4b and Atf3 to METH exposure depend on the specific region of the brain involved.

The pharmacokinetics of racemic MDPV and its (R) and (S) enantiomers in female and male rats

BACKGROUND

These studies investigated the serum pharmacokinetic (PK) profile of racemic (3,4)-methylenedioxypyrovalerone [(R,S)-MDPV)] and its (R)- and (S)-enantiomers in female and male Sprague Dawley rats.

METHODS

Intravenous (R,S)-MDPV (3 and 5.6mg/kg) and single enantiomer of (R)- and (S)-MDPV (1.5mg/kg) were administered to both sexes for PK studies. Intraperitoneal (ip) bioavailability was determined at 3mg/kg (R,S)-MDPV. Locomotor activity studies were conducted after ip treatment with saline and 0.3-5.6mg/kg of (R,S)-MDPV.

RESULTS

PK values after iv (R,S)-MDPV showed a significant (p<0.05) sex-dependent differences in the volume of distribution at steady state (Vd_ss) for (R)- and (R,S)-MDPV at both (R,S)-MDPV doses. The female S/R enantiomeric ratios for area under the concentration time curve (AUC_inf) and clearance were significantly lower and higher, respectively, than values determined in males. Importantly, there was no evidence of in vivo inversion of (R)-MDPV or (S)-MDPV to its antipode. There were, however, significant sex-dependent differences in volume of distribution after administration of the (R)-enantiomer. Bioavailability studies of ip (R,S)-MDPV showed greater variability and significantly greater bioavailability in male rats. Accordingly, there was a significantly greater maximal distance traveled measurement in male rats at a 3.0mg/kg dose.

CONCLUSION

PK sex differences in (R,S)-MDPV and enantiomers were most apparent in volume of distribution, which could be caused by differences in drug blood and tissue protein binding. The increased magnitude and variance in ip bioavailability in male compared to female rats could lead to sex-dependent differences in the pharmacological action caused by active enantiomer (S)-MDPV.

Exposure of adolescent mice to 3,4-methylenedioxypyrovalerone increases the psychostimulant, rewarding and reinforcing effects of cocaine in adulthood

BACKGROUND AND PURPOSE

3,4-Methylenedioxypyrovalerone (MDPV) is a synthetic cathinone with powerful psychostimulant effects. It selectively inhibits the dopamine transporter (DAT) and is 10-50-fold more potent as a DAT blocker than cocaine, suggesting a high abuse liability. The main objective of the present study was to assess the consequences of an early (adolescence) MDPV exposure on the psychostimulant, rewarding and reinforcing effects induced by cocaine in adult mice.

EXPERIMENTAL APPROACH

Twenty-one days after MDPV pretreatment (1.5 mg·kg^-1 , s.c., twice daily for 7 days), adult mice were tested with cocaine, using locomotor activity, conditioned place preference and self-administration (SA) paradigms. In parallel, dopamine D₂ receptor density and the expression of c-Fos and ΔFosB in the striatum were determined.

KEY RESULTS

MDPV treatment enhanced the psychostimulant and conditioning effects of cocaine. Acquisition of cocaine SA was unchanged in mice pretreated with MDPV, whereas the breaking point achieved under a progressive ratio programme and reinstatement after extinction were higher in this group of mice. MDPV decreased D₂ receptor density but increased ΔFosB expression three-fold. As expected, acute cocaine increased c-Fos expression, but MDPV pretreatment negatively influenced its expression. ΔFosB accumulation declined during MDPV withdrawal, although it remained elevated in adult mice when tested for cocaine effects.

CONCLUSION AND IMPLICATIONS

MDPV exposure during adolescence induced long-lasting adaptive changes related to enhanced responsiveness to cocaine in the adult mice that seems to lead to a higher vulnerability to cocaine abuse. This particular behaviour correlated with increased expression of ΔFosB.