Neurobiology of 3,4-methylenedioxypyrovalerone (MDPV) and α-pyrrolidinovalerophenone (α-PVP)

The psychomotor, reinforcing, and discriminative stimulus effects of synthetic cathinone mexedrone in male mice and rats

The chronic use of the novel synthetic cathinone mexedrone, like other psychoactive drugs, can be considered addictive, with a high potential for abuse and the ability to cause psychological dependence in certain users. However, little is known about the neurobehavioral effects of mexedrone in association with its potential for abuse. We investigated the abuse potential for mexedrone abuse through multiple behavioral tests. In addition, serotonin transporter (SERT) levels were measured in the synaptosome of the dorsal striatum, and serotonin (5-HT) levels were measured in the dorsal striatum of acute mexedreone (50 mg/kg)-treated mice. To clarify the neuropharmacological mechanisms underlying the locomotor response of mexedrone, the 5-HT2A receptor antagonist M100907 (0.5 or 1.0 mg/kg) was administered prior to the acute injection of mexedrone in the locomotor activity experiment in mice. Mexedrone (10-50 mg/kg) produced a significant place preference in mice and mexedrone (0.1-0.5 mg/kg/infusion) maintained self-administration behavior in rats in a dose-dependent manner. In the drug discrimination experiment, mexedrone (5.6-32 mg/kg) was fully substituted for the discriminative stimulus effects of cocaine in rats. Mexedrone increased locomotor activity, and these effects were reversed by pretreatment with M100907. Acute mexedrone significantly increased c-Fos expression in the dorsal striatum and decreased SERT levels in the synaptosome of the dorsal striatum of mice, resulting in an elevation of 5-HT levels. Taken together, our results provide the possibility that mexedrone has abuse potential, which might be mediated, at least in part, by the activation of the serotonergic system in the dorsal striatum.

The pharmacology and neurotoxicology of synthetic cathinones

The synthetic cathinones are man-made compounds derived from the naturally occurring drug cathinone, which is found in the khat plant. The drugs in this pharmacological class that will be the focus of this chapter include mephedrone, MDPV, methcathinone and methylone. These drugs are colloquially known as "bath salts". This misnomer suggests that these drugs are used for health improvement or that they have legitimate medical uses. The synthetic cathinones are dangerous drugs with powerful pharmacological effects that include high abuse potential, hyperthermia and hyperlocomotion. These drugs also share many of the pharmacological effects of the amphetamine class of drugs including methamphetamine, amphetamine and MDMA and therefore have high potential to cause damage to the central nervous system. The synthetic cathinones are frequently taken in combination with other psychoactive drugs such as alcohol, marijuana and the amphetamine-like stimulants, creating a situation where heightened pharmacological and neurotoxicological effects are likely to occur. Despite the structural features shared by the synthetic cathinones and amphetamine-like stimulants, including their actions at monoamine transporters and receptors, the effects of the synthetic cathinones do not always match those of the amphetamines. In particular, the synthetic cathinones are far less neurotoxic than their amphetamine counterparts, they produce a weaker hyperthermia, and they cause less glial activation. This chapter will briefly review the pharmacology and neurotoxicology of selected synthetic cathinones with the aim of delineating key areas of agreement and disagreement in the literature particularly as it relates to neurotoxicological outcomes.

Structural and functional perspectives on interactions between synthetic cathinones and monoamine transporters

Synthetic cathinone derivatives comprise a family of psychoactive compounds structurally related to amphetamine. Over the last decade, clandestine chemists have synthesized a consistent stream of innovative cathinone derivatives to outpace governmental regulatory restrictions. Many of these unregulated substances are produced and distributed as designer drugs. Two of the principal chemical scaffolds exploited to expand the synthetic cathinone family are methcathinone and α-pyrrolidinopentiophenone (or α-pyrrolidinovalerophenone, α-PVP). These compounds' main physiological targets are monoamine transporters, where they promote addiction by potentiating dopaminergic neurotransmission. This chapter describes techniques used to study the pharmacodynamic properties of cathinones at monoamine transporters in vitro. Biochemical techniques described include uptake inhibition and release assays in rat brain synaptosomes and in mammalian expression systems. Electrophysiological techniques include current measurements using the voltage clamp technique. We describe a Ca2+ mobilization assay wherein voltage-gated Ca2+ channels function as reporters to study the action of synthetic cathinones at monoamine transporters. We discuss results from systematic structure-activity relationship studies on simple and complex cathinones at monoamine transporters with an emphasis on identifying structural moieties that modulate potency and selectivity at these transporters. Moreover, different profiles of selectivity at monoamine transporters directly predict compounds associated with behavioral and subjective effects within animals and humans. In conclusion, clarification of the structural aspects of compounds which modulate potency and selectivity at monoamine transporters is critical to identify and predict potential addictive drugs. This knowledge may allow prompt allocation of resources toward drugs that represent the greatest threats after drugs are identified by forensic laboratories.

Alpha pyrrolidinovalerophenone (α-PVP) administration impairs spatial learning and memory in rats through brain mitochondrial dysfunction

Novel psychoactive substances (NPS) consumption has increased in recent years, thus NPS-induced cognitive decline is a current source of concern. Alpha-pyrrolidinovalerophenone (α-PVP), as a member of NPS, is consumed throughout regions like Washington, D.C., Eastern Europe, and Central Asia. Mitochondrial dysfunction plays an essential role in NPS-induced cognitive impairment. Meanwhile, no investigations have been conducted regarding the α-PVP impact on spatial learning/memory and associated mechanisms. Consequently, our study investigated the α-PVP effect on spatial learning/memory and brain mitochondrial function. Wistar rats received different α-PVP doses (5, 10, and 20 mg/kg) intraperitoneally for 10 sequential days; 24 h after the last dose, spatial learning/memory was evaluated by the Morris Water Maze (MWM). Furthermore, brain mitochondrial protein yield and function variables (Mitochondrial swelling, succinate dehydrogenase (SDH) activity, lipid peroxidation, Mitochondrial Membrane Potential (MMP), Reactive oxygen species (ROS) level, brain ADP/ATP proportion, cytochrome c release, Mitochondrial Outer Membrane (MOM) damage) were examined. α-PVP higher dose (20 mg/kg) significantly impaired spatial learning/memory, mitochondrial protein yield, and brain mitochondrial function (caused reduced SDH activity, increased mitochondrial swelling, elevated ROS generation, increased lipid peroxidation, collapsed MMP, increased cytochrome c release, and brain ADP/ATP proportion, and MOM damage). Moreover, the lower dose of α-PVP (5 mg/kg) did not alter spatial learning/memory and brain mitochondrial function. These findings provide the first evidence regarding impaired spatial learning and memory following repeated administration of α-PVP and the possible role of brain mitochondrial dysfunction in these cognitive impairments.

Effects of Methylone Pre-Exposure on Fluoxetine-Induced Conditioned Taste Avoidance in Male and Female Sprague-Dawley Rats

Background: Prior work has reported that a drug’s aversive effects (as indexed by taste avoidance conditioning) are attenuated when the pre-exposure and conditioning drugs are the same or different. The latter, otherwise known as cross-drug pre-exposure, is especially interesting as it has been used as a tool to assess mechanisms underlying the aversive effects of drugs. We previously reported that methylone pre-exposure differentially impacted the aversive effects of MDPV and MDMA (MDPV > MDMA), a difference consistent with the dopaminergic mediation of methylone’s aversive effects. To examine the possible role of serotonin (5-HT) in methylone’s aversive effects, the present study assessed the effects of methylone pre-exposure on taste avoidance induced by the 5-HT reuptake inhibitor fluoxetine. Methods: Male and female Sprague-Dawley rats were exposed to 10 mg/kg of methylone every 4th day (for a total of 5 injections) prior to taste avoidance training with 10 mg/kg of fluoxetine. Results: Fluoxetine induced significant taste avoidance (each p < 0.05) that was independent of sex. Methylone pre-exposure had no impact on avoidance produced by fluoxetine in either males or females (each p > 0.05). Conclusions: Methylone pre-exposure had no impact on fluoxetine-induced avoidance. These findings suggest that it is unlikely that 5-HT mediates the aversive effects of methylone. The implications of the present results for the mechanisms mediating methylone’s aversive effects were discussed. Understanding such mechanisms is important in predictions relevant to drug history and abuse liability as a variety of subject and experiential factors known to affect (reduce) a drug’s aversive effects may increase its use and potential for abuse.

Ethanol pre-exposure differentially impacts the rewarding and aversive effects of α-pyrrolidinopentiophenone (α-PVP): Implications for drug use and abuse

RATIONALE

Exposure to a drug can subsequently impact its own reactivity as well as that of other drugs. Given that users of synthetic cathinones, i.e., "bath salts", typically have extensive and varied drug histories, an understanding of the effects of drug history on the behavioral and physiological consequences of synthetic cathiones may be important to their abuse liability.

OBJECTIVES

The goal of the current work was to assess the effects of an ethanol pre-exposure on the rewarding and aversive effects of α-PVP.

METHODS

Adult male Sprague Dawley rats were exposed to ethanol prior to combined conditioned taste avoidance/conditioned place preference training in which rats were injected with 1.5, 3 or 5 mg/kg of racemic α-PVP or vehicle. Following a 7-day washout period, rats were then tested for thermoregulatory effects of α-PVP using subcutaneous probes to measure body temperature changes over the course of 8 h. This was followed 10 days later by assessments for α-PVP-induced locomotor activity and stereotypies over a 1-h session.

RESULTS

α-PVP induced significant dose- and trial-dependent taste avoidance that was significantly attenuated by ethanol history and dose- and time-dependent increases in locomotor activity that were significantly increased by ethanol. α-PVP also induced place preferences and dose- and time-dependent increases in body temperature, but these measures were unaffected by ethanol history.

CONCLUSIONS

α-PVP's aversive effects (as measured by taste avoidance) were attenuated, while its rewarding effects (as indexed by place preference conditioning) were unaffected, by ethanol pre-exposure. Such a pattern may indicate increased α-PVP abuse liability, as changes in the balance of aversion and reward may impact overall drug effects and likelihood of drug intake. Future self-administration studies will be necessary to explore this possibility.

Worsening of the Toxic Effects of (±)Cis-4,4'-DMAR Following Its Co-Administration with (±)Trans-4,4'-DMAR: Neuro-Behavioural, Physiological, Immunohistochemical and Metabolic Studies in Mice

4,4’-Dimethylaminorex (4,4’-DMAR) is a new synthetic stimulant, and only a little information has been made available so far regarding its pharmaco-toxicological effects. The aim of this study was to investigate the effects of the systemic administration of both the single (±)cis (0.1–60 mg/kg) and (±)trans (30 and 60 mg/kg) stereoisomers and their co-administration (e.g., (±)cis at 1, 10 or 60 mg/kg + (±)trans at 30 mg/kg) in mice. Moreover, we investigated the effect of 4,4′-DMAR on the expression of markers of oxidative/nitrosative stress (8-OHdG, iNOS, NT and NOX2), apoptosis (Smac/DIABLO and NF-κB), and heat shock proteins (HSP27, HSP70, HSP90) in the cerebral cortex. Our study demonstrated that the (±)cis stereoisomer dose-dependently induced psychomotor agitation, sweating, salivation, hyperthermia, stimulated aggression, convulsions and death. Conversely, the (±)trans stereoisomer was ineffective whilst the stereoisomers’ co-administration resulted in a worsening of the toxic (±)cis stereoisomer effects. This trend of responses was confirmed by immunohistochemical analysis on the cortex. Finally, we investigated the potentially toxic effects of stereoisomer co-administration by studying urinary excretion. The excretion study showed that the (±)trans stereoisomer reduced the metabolism of the (±)cis form and increased its amount in the urine, possibly reflecting its increased plasma levels and, therefore, the worsening of its toxicity.

Single Exposure to the Cathinones MDPV and α-PVP Alters Molecular Markers of Neuroplasticity in the Adult Mouse Brain

Synthetic cathinones have gained popularity among young drug users and are widely used in the clandestine market. While the cathinone-induced behavioral profile has been extensively investigated, information on their neuroplastic effects is still rather fragmentary. Accordingly, we have exposed male mice to a single injection of MDPV and α-PVP and sacrificed the animals at different time points (i.e., 30 min, 2 h, and 24 h) to have a rapid readout of the effect of these psychostimulants on neuroplasticity in the frontal lobe and hippocampus, two reward-related brain regions. We found that a single, low dose of MDPV or α-PVP is sufficient to alter the expression of neuroplastic markers in the adult mouse brain. In particular, we found increased expression of the transcription factor Npas4, increased ratio between the vesicular GABA transporter and the vesicular glutamate transporter together with changes in the expression of the neurotrophin Bdnf, confirming the widespread impact of these cathinones on brain plasticity. To sum up, exposure to low dose of cathinones can impair cortical and hippocampal homeostasis, suggesting that abuse of these cathinones at much higher doses, as it occurs in humans, could have an even more profound impact on neuroplasticity.

Evaluation of Cytotoxic and Mutagenic Effects of the Synthetic Cathinones Mexedrone, α-PVP and α-PHP

Mexedrone, α-PVP and α-PHP are synthetic cathinones. They can be considered amphetamine-like substances with a stimulating effect. Actually, studies showing their impact on DNA are totally absent. Therefore, in order to fill this gap, aim of the present work was to evaluate their mutagenicity on TK6 cells. On the basis of cytotoxicity and cytostasis results, we selected the concentrations (35–100 µM) to be used in the further analysis. We used the micronucleus (MN) as indicator of genetic damage and analyzed the MNi frequency fold increase by flow cytometry. Mexedrone demonstrated its mutagenic potential contrary to the other two compounds; we then proceeded by repeating the analyzes in the presence of extrinsic metabolic activation in order to check if it was possible to totally exclude the mutagenic capacity for α-PVP and α-PHP. The results demonstrated instead the mutagenicity of their metabolites. We then evaluated reactive oxygen species (ROS) induction as a possible mechanism at the basis of the highlighted effects but the results did not show a statistically significant increase in ROS levels for any of the tested substances. Anyway, our outcomes emphasize the importance of mutagenicity evaluation for a complete assessment of the risk associated with synthetic cathinones exposure.

Molecular Mechanisms of Action of Novel Psychoactive Substances (NPS). A New Threat for Young Drug Users with Forensic-Toxicological Implications

Novel psychoactive substances (NPS) represent a severe health risk for drug users. Even though the phenomenon has been growing since the early 2000s, the mechanisms of action of NPS at the receptors and beyond them are still scarcely understood. The aim of the present study was to provide a systematic review of the updated knowledge regarding the molecular mechanisms underlying the toxicity of synthetic opioids, cannabinoids, cathinones, and stimulants. The study was conducted on the PubMed database. Study eligibility criteria included relevance to the topic, English language, and time of publication (2010–2020). A combined Mesh and free-text protocols search was performed. Study selection was performed on the title/abstract and, in doubtful cases, on the full texts of papers. Of the 580 records identified through PubMed searching and reference checking, 307 were excluded by title/abstract and 78 additional papers were excluded after full-text reading, leaving a total of 155 included papers. Molecular mechanisms of synthetic opioids, synthetic cannabinoids, stimulants, psychedelics, and hallucinogens were reviewed and mostly involved both a receptor-mediated and non-receptor mediated cellular modulation with multiple neurotransmitters interactions. The molecular mechanisms underlying the action of NPS are more complex than expected, with a wide range of overlap among activated receptors and neurotransmitter systems. The peculiar action profile of single compounds does not necessarily reflect that of the structural class to which they belong, accounting for possible unexpected toxic reactions.

Alpha-pyrrolidinopentiophenone and mephedrone self-administration produce differential neurochemical changes following short- or long-access conditions in rats

Stimulant-induced neurochemical changes may occur at different times for different brain regions or neurotransmitter systems. This study sought to examine the behavioral and neurochemical effects of extended access to α-pyrrolidinopentiophenone (α-PVP) and 4-methylmethcathinone (4MMC). Male and female Sprague-Dawley rats were trained to self-administer α-PVP (0.1 mg/kg/infusion) or 4MMC (0.5 mg/kg/infusion) through autoshaping, and then self-administered for 21 days during 1 h (short access; ShA) or 6 h (long access; LgA) sessions. Separate rats were assigned to a naïve control group. Amygdala, hippocampus, hypothalamus, prefrontal cortex (PFC), striatum, and thalamus were extracted, and tissue was analyzed with electrochemical detection and liquid chromatography mass spectrometry. Rats acquired self-administration of α-PVP and 4MMC, and LgA rats showed more escalation of self-administration than ShA rats. Synthetic cathinone administration produced several effects on neurotransmitters. LgA self-administration of α-PVP increased 5-HIAA levels in all brain regions, compared to control. In contrast, both LgA and ShA 4MMC self-administration decreased 5-HT and 5-HIAA levels in most brain regions. LgA exposure to both synthetic cathinones increased DOPAC levels in hypothalamus and striatum, and increased HVA levels in striatum compared to control. LgA self-administration of either synthetic cathinone produced region-specific increases in NE levels, whereas ShA self-administration lowered NE levels in select locations compared to control. These alterations in neurotransmitter levels indicate that synthetic cathinone use may produce differential neurochemical changes during the transition from use to abuse, and that 21 days of self-administration only models the beginning stages of dysregulated drug intake.

A Case of Alpha-Pyrrolidinopentiophenone (Flakka)-Induced Ischemic Stroke

Alpha-pyrrolidinovalerophenone (α-PVP) is a designer drug, the mechanism of action of which resembles that of cocaine and amphetamine. New data about the side effects of α-PVP are emerging. We present a case report of an acute ischemic stroke following the recreational use of α-PVP. The ischemic lesions were located in the middle cerebral artery and deep watershed areas of the left cerebral hemisphere. Occupational therapy and physiotherapy were initiated, and the patient was discharged with only a mild right hemiparesis.

Acute MDPV Binge Paradigm on Mice Emotional Behavior and Glial Signature

3,4-Methylenedioxypyrovalerone (MDPV), a widely available synthetic cathinone, is a popular substitute for classical controlled drugs of abuse, such as methamphetamine (METH). Although MDPV poses public health risks, its neuropharmacological profile remains poorly explored. This study aimed to provide evidence on that direction. Accordingly, C57BL/6J mice were exposed to a binge MDPV or METH regimen (four intraperitoneal injections every 2 h, 10 mg/kg). Locomotor, exploratory, and emotional behavior, in addition to striatal neurotoxicity and glial signature, were assessed within 18–24 h, a known time-window encompassing classical amphetamine dopaminergic neurotoxicity. MDPV resulted in unchanged locomotor activity (open field test) and emotional behavior (elevated plus maze, splash test, tail suspension test). Additionally, striatal TH (METH neurotoxicity hallmark), Iba-1 (microglia), GFAP (astrocyte), RAGE, and TLR2/4/7 (immune modulators) protein densities remained unchanged after MDPV-exposure. Expectedly, and in sheer contrast with MDPV, METH resulted in decrease general locomotor activity paralleled by a significant striatal TH depletion, astrogliosis, and microglia arborization alterations (Sholl analysis). This comparative study newly highlights that binge MDPV-exposure comes without evident behavioral, neurochemical, and glial changes at a time-point where METH-induced striatal neurotoxicity is clearly evident. Nevertheless, neuropharmacological MDPV signature needs further profiling at different time-points, regimens, and brain regions.

Analysis for Alpha-Pyrrolidinovalerophenone and Its 2-Oxo-PVP Metabolite in Plasma by Liquid Chromatography-Tandem Mass Spectrometry

Alpha-pyrrolidinovalerophenone (alpha-PVP), a novel psychoactive substance, has widespread recreational use. This with interest in its pharmacological effects creates a need for methods that measure alpha-PVP concentrations. We therefore developed a LC-MS/MS method that can quantitate alpha-PVP and 2-oxo-PVP in rat plasma using a 0.1-mL sample volume. Addition of internal standards (2.5 ng/mL alpha-PVP-d8/2-oxo-PVP-d6) was followed by liquid-liquid extraction with 1-chlorobutane:acetonitrile (4:1), evaporation and reconstitution with 0.1% formic acid. Extracts were analyzed by LC-MS/MS using an Agilent 1100 HPLC and a Thermo Scientific TSQ Quantum Access MS/MS, with a YMC ODS-AQ, 50 mm × 2 mm, 3 μm column. The mobile phase was 0.1% formic acid:acetonitrile gradient at a 0.2-mL/minute flow rate with positive ion electrospray. SRM was used for the analysis with transitions: alpha-PVP, 232 → 91; alpha-PVP-d8, 240 → 91; 2-oxo-PVP, 246 → 91; 2-oxo-PVP-d6, 252 → 91. Alpha-PVP and 2-oxo-PVP eluted at 6.4 and 8.9 min. Calibrators range from 0.25 to 500 ng/mL. Accuracy and precision evaluated quality control samples prepared at 0.75, 10 and 400 ng/mL. The intra-assay evaluation also included the 0.25-ng/mL LOQs prepared in six different blank plasma sources. The intra-assay accuracy ranged from 88.9 to 117.8% of the target, and the intra-assay precision ranged from 0.9 to 16.0%. The inter-assay accuracy ranged from 98.7 to 110.7% of the target, and the inter-assay precision ranged from 4.5 to 12.0%. Extraction recovery was at least 52% for alpha-PVP and 67% for 2-oxo-PVP. Ionization recoveries were at least 64% for alpha-PVP and 82% for 2-oxo-PVP. These losses did not adversely affect assay performance. Alpha-PVP and 2-oxo-PVP controls were stable at room temperature for up to 24 h and frozen for at least 36 days. Alpha-PVP and 2-oxo-PVP were also stable in processed samples (extracts) stored at room temperature for at least 24 days. The procedure was used to analyze rat plasma samples from a pharmacokinetic study.

Role of amino terminal substitutions in the pharmacological, rewarding and psychostimulant profiles of novel synthetic cathinones

The emergence of new synthetic cathinones continues to be a matter of public health concern. In fact, they are quickly replaced by new structurally related alternatives. The main goal of the present study was to characterize the pharmacological profile, the psychostimulant and rewarding properties of novel cathinones (pentedrone, N-ethyl-pentedrone, α-PVP, N,N-diethyl-pentedrone and α-PpVP) which only differs in their amino terminal substitution. Rat synaptosomes were used for [³H]dopamine uptake experiments. HEK293 transfected cells (hDAT, hSERT, hOCT; human dopamine, serotonin and organic cation transporter) were also used for [³H]monoamine uptake and transporter binding assays. Molecular docking was used to investigate the effect of the amino substitutions on the biological activity. Hyperlocomotion and conditioned place preference paradigm were used in order to study the psychostimulant and rewarding effects in mice. All compounds tested are potent inhibitors of DAT with very low affinity for SERT, hOCT-2 and -3, and their potency for inhibiting DAT increased when the amino-substituent expanded from a methyl to either an ethyl-, a pyrrolidine- or a piperidine-ring. Regarding the in vivo results, all the compounds induced an increase in locomotor activity and possess rewarding properties. Results also showed a significant correlation between predicted binding affinities by molecular docking and affinity constants (Ki) for hDAT as well as the cLogP of their amino-substituent with their hDAT/hSERT ratios. Our study demonstrates the role of the amino-substituent in the pharmacological profile of novel synthetic cathinones as well as their potency inhibiting DA uptake and ability to induce psychostimulant and rewarding effects in mice.

Stereoselective neurochemical, behavioral, and cardiovascular effects of α-pyrrolidinovalerophenone enantiomers in male rats

The synthetic cathinone α-pyrrolidinovalerophenone (α-PVP) continues to be abused despite being banned by regulatory agencies. The abused formulation of α-PVP is a racemic mixture consisting of two enantiomers, S-α-PVP and R-α-PVP. In this study, we investigated the neurochemical, behavioral, and cardiovascular effects of racemic α-PVP and its enantiomers in male rats. Racemic α-PVP blocked the uptake of both dopamine and norepinephrine ex vivo, but did not block the uptake of serotonin (5-HT), at their respective transporters. S-α-PVP was slightly more potent than racemic α-PVP, while R-α-PVP was 10 to 20 times less potent at blocking dopamine and norepinephrine uptake. In microdialysis studies, racemic and S-α-PVP increased extracellular dopamine levels in the nucleus accumbens, but not levels of 5-HT. Racemic and S-α-PVP also increased locomotor activity. When tested at the same doses, S-α-PVP produced larger effects than racemic α-PVP. R-α-PVP also increased extracellular dopamine levels and locomotor activity, but only at 30 times higher doses than S-α-PVP. Racemic and S-α-PVP were self-administered by rats at 0.03 mg/kg/injection, whereas R-α-PVP was self-administered at a 10 times higher dose. Dose-effect determinations following acquisition suggested that R-α-PVP was at least 30 times less potent than S-α-PVP. Finally, racemic and S-α-PVP increased blood pressure and heart rate at doses approximately 30 times less than was required for R-α-PVP to produce similar effects. These results show that the neurochemical, behavioral, and cardiovascular effects of racemic α-PVP most likely reflect the actions of S isomer.

Detrimental effects of the 'bath salt' methylenedioxypyrovalerone on social play behavior in male rats

Methylenedioxypyrovalerone (MDPV) is the most popular synthetic cathinone found in products marketed as 'bath salts', widely abused among teenagers and young adults. Synthetic cathinones have pharmacological effects resembling those of psychostimulants, which are known to disrupt a variety of social behaviors. However, despite the popular use of MDPV by young people in social contexts, information about its effects on social behavior is scarce. To investigate the impact of MDPV on social behavior at young age, and the underlying neurobehavioral mechanisms, we focused on social play behavior. Social play behavior is the most characteristic social behavior displayed by young mammals and it is crucial for neurobehavioral development. Treatment with MDPV reduced social play behavior in both juvenile and young adult male rats, and its play-suppressant effect was subject to tolerance but not sensitization. As the behavioral effects of MDPV have been ascribed to dopaminergic and noradrenergic neurotransmission, and given the role of these neurotransmitters in social play, we investigated the involvement of dopamine and noradrenaline in the play-suppressant effects of MDPV. The effects of MDPV on social play were blocked by either the α2 adrenoceptor antagonist RX821002 or the dopamine receptor antagonist flupenthixol, given alone or together at sub-effective doses. In sum, MDPV selectively suppresses the most vigorous social behavior of developing rats through both noradrenergic and dopaminergic mechanisms. This study provides important preclinical evidence of the deleterious effects of MDPV on social behavior, and as such increases our understanding of the neurobehavioral effects of this popular cathinone.

A Sensitive Nanosensor for the In Situ Detection of the Cannibal Drug

A bio-inspired nanodevice for the selective and sensitive fluorogenic detection of 3,4-methylenedioxypyrovalerone (MDPV), usually known as Cannibal drug, is reported. The sensing nanodevice is based on mesoporous silica nanoparticles (MSNs), loaded with a fluorescent reporter (rhodamine B), and functionalized on their external surface with a dopamine derivative (3), which specifically interacts with the recombinant human dopamine transporter (DAT), capping the pores. In the presence of MDPV, DAT detaches from the MSNs consequently, causing rhodamine B release and allowing drug detection. The nanosensor shows a detection limit of 5.2 μM, and it is able to detect the MDPV drug both in saliva and blood plasma samples.

Sex and Gender Differences in the Effects of Novel Psychoactive Substances

Sex and gender deeply affect the subjective effects and pharmaco-toxicological responses to drugs. Men are more likely than women to use almost all types of illicit drugs and to present to emergency departments for serious or fatal intoxications. However, women are just as likely as men to develop substance use disorders, and may be more susceptible to craving and relapse. Clinical and preclinical studies have shown important differences between males and females after administration of “classic” drugs of abuse (e.g., Δ9-tetrahydrocannabinol (THC), morphine, cocaine). This scenario has become enormously complicated in the last decade with the overbearing appearance of the new psychoactive substances (NPS) that have emerged as alternatives to regulated drugs. To date, more than 900 NPS have been identified, and can be catalogued in different pharmacological categories including synthetic cannabinoids, synthetic stimulants (cathinones and amphetamine-like), hallucinogenic phenethylamines, synthetic opioids (fentanyls and non-fentanyls), new benzodiazepines and dissociative anesthetics (i.e., methoxetamine and phencyclidine-derivatives). This work collects the little knowledge reached so far on the effects of NPS in male and female animal and human subjects, highlighting how much sex and gender differences in the effects of NPS has yet to be studied and understood.

Investigation of the Optical Isomers of Methcathinone, and Two Achiral Analogs, at Monoamine Transporters and in Intracranial Self-Stimulation Studies in Rats

Methcathinone (MCAT; 1), the progenitor of numerous and widely abused "synthetic cathinone" central stimulants, exists as a pair of optical isomers. Although S(-)MCAT is several-fold more potent than R(+)MCAT in rodent locomotor stimulation and in stimulus generalization studies in rat drug discrimination assays, the individual optical isomers of MCAT have never been directly compared for their actions at monoamine transporters that seem to underlie their actions and have never been examined for their relative abuse potential. Here, we found that the isomers of MCAT are nearly equieffective at dopamine and norepinephrine transporters (DAT and NET, respectively) as transporter substrates (i.e., as releasing agents) and are ≥63-fold less potent at the serotonin transporter (SERT). In intracranial self-stimulation (ICSS) studies to evaluate abuse-related drug effects in rats, S(-)MCAT was approximately twice as potent as its R-enantiomer. Achiral analogs, α-methyl MCAT (3) and α-des-methyl MCAT (4), also were DAT/NET substrates and also produced abuse-related ICSS effects, indicating that they retain abuse potential and that they might be useful for the further study of the stereochemistry of synthetic cathinone analogs with chiral β- (or other) substituents.

Designer Cathinones N-Ethylhexedrone and Buphedrone Show Different In Vitro Neurotoxicity and Mice Behaviour Impairment

N-Ethylhexedrone (NEH) and buphedrone (Buph) are emerging synthetic cathinones (SC) with limited information about their detrimental effects within central nervous system. Objectives: To distinguish mice behavioural changes by NEH and Buph and validate their differential harmful impact on human neurons and microglia. In vivo safety data showed the typical induced behaviour of excitation and stereotypies with 4-64 mg/kg, described for other SC. Buph additionally produced jumping and aggressiveness signs, while NEH caused retropulsion and circling. Transient reduction in body-weight gain was obtained with NEH at 16 mg/kg and induced anxiolytic-like behaviour mainly with Buph. Both drugs generated place preference shift in mice at 4 and 16 mg/kg, suggestive of abuse potential. In addition, mice withdrawn NEH displayed behaviour suggestive of depression, not seen with Buph. When tested at 50-400 μM in human nerve cell lines, NEH and Buph caused neuronal viability loss at 100 μM, but only NEH produced similar results in microglia, indicating different cell susceptibilities. NEH mainly induced microglial late apoptosis/necrosis, while Buph caused early apoptosis. NEH was unique in triggering microglia shorter/thicker branches indicative of cell activation, and more effective in increasing microglial lysosomal biogenesis (100 μM vs. 400 μM Buph), though both produced the same effect on neurons at 400 μM. These findings indicate that NEH and Buph exert neuro-microglia toxicities by distinct mechanisms and highlight NEH as a specific inducer of microglia activation. Buph and NEH showed in vivo/in vitro neurotoxicities but enhanced specific NEH-induced behavioural and neuro-microglia dysfunctionalities pose safety concerns over that of Buph.

Determination of synthetic cathinone α-pyrrolidinovalero-phenone and its metabolite in urine using solid-phase extraction and gas chromatography-mass spectrometry

RATIONALE

The presence of α-pyrrolidinovalerophenone (α-PVP) and its metabolites in urine is evidence of the administration of α-PVP. A toxicological challenge is that the metabolites of α-PVP exhibit amphoteric properties, which make them unsuitable for detection using gas chromatography-mass spectrometry (GC/MS). In the study reported, proper derivatization and sample extraction were essential for improving the sensitivity for GC/MS analysis.

METHODS

An automated solid-phase extraction (SPE) method has been developed and optimized. The derivatization efficiency was tested using longer reaction time and the addition of polar pyridine into a mixture of N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) with 1% trimethylchlorosilane. Method validation, including linearity, limit of detection, precision, accuracy, and recovery, was evaluated using automatic SPE and GC/MS.

RESULTS

The results suggested that adding pyridine to BSTFA (1:1, v/v) significantly improved derivatization efficiency and precision. After optimization, the linear range was from 25 to 1000 ng mL^-1 with R²  > 0.9950. The limit of detection was 5 ng mL^-1 for α-PVP and 25 ng mL^-1 for OH-α-PVP. The recovery for SPE was over 88%. The inter-day and intra-day precisions were less than 15%. A forensic sample has been found containing α-PVP (67.3 ng mL^-1 ) and OH-α-PVP (560.2 ng mL^-1 ).

CONCLUSIONS

This study is the first to validate an auto-SPE-GC/MS method for the quantification and qualification of α-PVP and OH-α-PVP in urine. We have successfully improved the derivatization efficiency and developed a sensitive and semi-automatic approach. This approach is desirable for the detection of synthetic cathinone at trace levels in biological samples.

The clinical challenges of synthetic cathinones

AIMS

Within the new psychoactive substances (NPS) scenario, several hundred different molecules, mostly including synthetic cannabinoids and cathinones, have been identified so far. The aims of the paper were to: (i) identify the number of synthetic cathinones mentioned in a range of psychonaut, NPS-related, online sources; and (ii) describe the associated acute/long term clinical scenario and the related treatment/management plan.

METHODS

After about 18 months of operation and exclusion of false positives/duplicates, some 4204 unique NPS molecules were included in the NPSfinder® crawling/navigating software database. Most popular NPS included: 1265 psychedelic phenethylamines (30.1%; confidence interval [CI] 95%: 28.7-31.5%); 1253 synthetic cannabinoids (29.8%; CI 95%: 28.4-31.2%); 429 synthetic opioids (10.2%; CI 95%: 9.3-10.2%); and 171 synthetic cathinones (4.1%; CI 95% 3.5-4.7%). Conversely, the United Nations Office on Drugs and Crime and the European Monitoring Centre for Drugs and Drug Addiction databases respectively included 169 and 140 cathinones. Overall, the 3 databases reported some 222 synthetic cathinones, and 41 were uniquely identified by the NPSfinder®.

RESULTS

In terms of clinical scenarios, synthetic cathinone ingestion is initially associated with stimulant effects; however, psychopathological disturbances, violence, suicidal behaviour, hyperthermia, coma and death have also been described.

CONCLUSION

The proportion of cathinones commented on by psychonaut fora appeared to be relatively small, and similar to those reported by both the United Nations Office on Drugs and Crime and European Monitoring Centre for Drugs and Drug Addiction. This may be associated with a recent significant decline in both cathinone-related consumption and acute medical presentation. Due to their complex behavioural and medical toxicity issues, healthcare professionals should be, however, be educated to recognise the signs and symptoms of NPS, including synthetic cathinone, ingestion.

Synthetic cathinone self-administration in female rats modulates neurotransmitter levels in addiction-related brain regions

Synthetic cathinones are used for their stimulant-like properties. Stimulant-induced neurochemical changes are thought to occur at different times in different brain regions and neurotransmitter systems. This study sought to examine the behavioral and neurochemical effects of α-pyrrolidinopentiophenone (α-PVP) and mephedrone (4MMC) in female rats. Methods probed the chronology of effects of synthetic cathinone exposure. Female rats were trained to self-administer α-PVP, 4MMC, or saline. Drug exposure ceased after 7 days of autoshaping for half of each drug group; the other half self-administered for another 21 days. Amygdala, hippocampus, hypothalamus, PFC, striatum, and thalamus were extracted, and tissue was analyzed with electrochemical detection and liquid chromatography mass spectrometry. Responding was minimal during autoshaping; thus, most infusions were delivered noncontingently in the autoshaping phase. Rats acquired self-administration of α-PVP and 4MMC. Synthetic cathinone administration, and duration of exposure produced several effects on neurotransmitters. α-PVP primarily increased serotonin, 5-hydroxy-3-acetic acid (5-HIAA), norepinephrine, and glutamate in hypothalamus. In contrast, 4MMC decreased serotonin and 5-HIAA in several brain regions. Longer durations of exposure to both synthetic cathinones increased 5-HIAA, norepinephrine, and glutamate in multiple brain regions compared to the short exposure during autoshaping. Notably, both α-PVP and 4MMC produced minimal changes in dopamine levels, suggesting that the dopaminergic effects of these synthetic cathinones are transient. These alterations in neurotransmitter levels indicate that synthetic cathinone use may produce differential neurochemical changes during the transition from use to abuse.

α-Pyrrolidinopentiophenone ("Flakka") Catalyzing Catatonia: A Case Report and Literature Review

: Synthetic cathinones are a class of novel psychoactive substances. α-Pyrrolidinopentiophenone (α-PVP), or "Flakka", is one of these substances. Users often present acutely psychotic or agitated. We present the case of a 20-year-old male without prior psychiatric history who was brought to the hospital by his family because of increasingly bizarre and erratic behavior after reported ingestion of Flakka. What ensued was a prolonged course of psychosis and severe catatonia. Synthetic cathinones are thought to cause catatonia in approximately 1% of cases. Awareness of the possible presentations associated with α-PVP intoxication is increasingly important and should be further explored, as they can have important implications in setting expectations for care. Additionally, providers should have a low threshold for asking patients about bath salt ingestion.

Synthetic Cathinone Analogues Structurally Related to the Central Stimulant Methylphenidate as Dopamine Reuptake Inhibitors

Synthetic cathinones are, primarily, stimulant drugs of abuse that act at monoamine transporters (e.g., the dopamine transporter or DAT) as releasing agents or as reuptake inhibitors. In the past few years, the emergence of >150 new synthetic cathinones has attracted considerable attention from medical and law enforcement communities. threo-Methylphenidate (tMP), used clinically for the treatment of ADHD and narcolepsy, is also a DAT reuptake inhibitor. tMP is somewhat structurally similar to abused cathinone stimulants, and the structure-activity relationships (SAR) of tMP have been well-defined. Hence, available tMP literature might assist in understanding the SAR of synthetic cathinones, about which less is known. In the present study, we synthesized and examined eight 2-benzoylpiperidine analogues (4, 6-12) to determine if tMP SAR might be applicable to cathinone SAR. The benzoylpiperidine analogues were evaluated in a competition assay using live-cell imaging against APP+ in HEK293 cells stably expressing hDAT and in cells coexpressing DAT and voltage-gated Ca2+ channels. All compounds were found to be DAT reuptake inhibitors, and a significant correlation was obtained between the potency of the benzoylpiperidines and tMP binding data (r = 0.91), suggesting that the SAR of tMP analogues might be directly applicable to certain synthetic cathinones as DAT reuptake inhibitors.

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.

Dopaminergic impact of cART and anti-depressants on HIV neuropathogenesis in older adults

The success of combination antiretroviral therapy (cART) has transformed HIV infection into a chronic condition, resulting in an increase in the number of older, cART-treated adults living with HIV. This has increased the incidence of age-related, non-AIDS comorbidities in this population. One of the most common comorbidities is depression, which is also associated with cognitive impairment and a number of neuropathologies. In older people living with HIV, treating these overlapping disorders is complex, often creating pill burden or adverse drug-drug interactions that can exacerbate these neurologic disorders. Depression, NeuroHIV and many of the neuropsychiatric therapeutics used to treat them impact the dopaminergic system, suggesting that dopaminergic dysfunction may be a common factor in the development of these disorders. Further, changes in dopamine can influence the development of inflammation and the regulation of immune function, which are also implicated in the progression of NeuroHIV and depression. Little is known about the optimal clinical management of drug-drug interactions between cART drugs and antidepressants, particularly in regard to dopamine in older people living with HIV. This review will discuss those interactions, first examining the etiology of NeuroHIV and depression in older adults, then discussing the interrelated effects of dopamine and inflammation on these disorders, and finally reviewing the activity and interactions of cART drugs and antidepressants on each of these factors. Developing better strategies to manage these comorbidities is critical to the health of the aging, HIV-infected population, as the older population may be particularly vulnerable to drug-drug interactions affecting dopamine.

Sex differences in α-pyrrolidinopentiophenone (α-PVP)-induced taste avoidance, place preference, hyperthermia and locomotor activity in rats

RATIONALE

The majority of synthetic cathinone research has used only male subjects, and as a result there are few studies assessing the impact of biological sex on their effects.

OBJECTIVES

The current work extends the characterization of the second-generation synthetic cathinone, α-PVP, by investigating how biological sex impacts α-PVP's aversive and rewarding effects important to its use and potential abuse.

METHODS

A combined conditioned taste avoidance/conditioned place preference preparation was utilized in which adult male and female Sprague Dawley rats were injected with 1.5, 3 or 6 mg/kg of racemic α-PVP or vehicle (saline) (IP). Following a 24-day washout period, rats were then tested for thermoregulatory effects of α-PVP using subcutaneous microchips to measure body temperature changes over the course of 8 h. This was followed 21 days later by assessments for α-PVP-induced locomotor activity and stereotypies over a 1-h session.

RESULTS

Dose-dependent conditioned taste avoidance was evident in both males and females, although females displayed weaker avoidance at 3 mg/kg compared to males. Males displayed a dose-dependent conditioned place preference, while females did not form a place preference at any dose. α-PVP elicited dose- and time-dependent hyperthermia, with males displaying a faster on-set and delayed off-set compared to females. α-PVP also produced dose- and time-dependent increases in locomotor activity (F > M) and stereotypies (M > F).

CONCLUSIONS

As described, males displayed greater rewarding (as indexed by place preference conditioning) and aversive (as indexed by taste avoidance, hyperthermia and stereotypies) effects of α-PVP. Although comparisons between males and females in α-PVP self-administration have not been reported, these data suggest that males may be more likely to use the drug. The implications for sex differences in human use of α-PVP were discussed.

Methylenedioxypyrovalerone (MDPV) impairs working memory and alters patterns of dopamine signaling in mesocorticolimbic substrates

Knowledge remains limited about how chronic cathinone exposure impacts dopamine systems in brain reward circuits. In the present study, a binge-like MDPV exposure that impaired novel object recognition (NOR) dysregulated dopamine markers in mesocorticolimbic substrates of rats, with especially profound effects on D1 and D2 receptor's and VMAT gene expression. Our data suggested that dopamine receptivity was reduced in the NAc but increased in the PFC and dopamine-producing VTA. The MDPV-induced impairment of NOR was prevented by a D1 receptor antagonist, suggesting that chronic MDPV exposure produces site-specific dysregulation of dopamine markers in the mesocorticolimbic circuit and memory deficits in the NOR test that are influenced by D1 receptors.

Analysis of neurotransmitter levels in addiction-related brain regions during synthetic cathinone self-administration in male Sprague-Dawley rats

RATIONALE

Synthetic cathinones are used as stimulants of abuse. Different stimulants may induce distinct rates of disease progression, yielding neurochemical changes that may vary across brain regions or neurotransmitter systems.

OBJECTIVES

This research sought to behaviorally and chemically differentiate stages of synthetic cathinone abuse through rodent self-administration and measurement of the neurotransmitter profile in multiple brain regions.

METHODS

Male rats were trained to self-administer α-PVP, mephedrone (4MMC), or saline. Half of each drug group stopped self-administering after autoshaping; the other half self-administered for another 21 days. Brain tissue from amygdala, hippocampus, hypothalamus, PFC, striatum, and thalamus was profiled with electrochemical detection to assess neurotransmitter levels.

RESULTS

During autoshaping, the majority of infusions were delivered noncontingently. In the self-administration phase, rats responded more for α-PVP and 4MMC than for saline, demonstrating that both synthetic cathinones were reinforcing. Longer durations of exposure elevated 5-HIAA in hypothalamus, PFC, and hippocampus, indicating that learning may produce changes in addiction-related brain regions. Both synthetic cathinones decreased norepinephrine in hippocampus, while α-PVP decreased glutamate in hippocampus and PFC, and 4MMC decreased glutamate in thalamus. Furthermore, α-PVP increased dopaminergic metabolites in striatum, whereas 4MMC decreased serotonin in the amygdala, hippocampus, and PFC. Interestingly, neither synthetic cathinone affected dopamine levels despite their functional effects on the dopaminergic system.

CONCLUSIONS

In summary, the neurotransmitter changes observed here suggest that synthetic cathinone use likely produces sequential neurochemical changes during the transition from use to abuse. Consequently, treatment need may differ depending on the progression of synthetic cathinone abuse.

Cognitive deficits and neurotoxicity induced by synthetic cathinones: is there a role for neuroinflammation?

RATIONALE

The number of synthetic derivatives of cathinone, the primary psychoactive alkaloid found in Catha edulis (khat), has risen exponentially in the past decade. Synthetic cathinones (frequently referred to as "bath salts") produce adverse cognitive and behavioral sequelae, share similar pharmacological mechanisms of action with traditional psychostimulants, and may therefore trigger similar cellular events that give rise to neuroinflammation and neurotoxicity.

OBJECTIVES

In this review, we provide a brief overview of synthetic cathinones, followed by a summary of cognitive deficits in animals and humans that have been documented following acute or repeated exposure. We also summarize growing evidence from in vitro and in vivo studies for synthetic cathinone-induced neurotoxicity, and provide a working hypothetic model of potential cellular mechanisms.

RESULTS

Synthetic cathinones produce varying effects on markers of monoaminergic terminal function and can increase the formation of reactive oxygen and nitrogen species, induce apoptotic signaling, and cause neurodegeneration and cytotoxicity. We hypothesize that these effects result from biochemical events similar to those induced by traditional psychostimulants. However, empirical evidence for the ability of synthetic cathinones to induce neuroinflammatory processes is currently lacking.

CONCLUSIONS

Like their traditional psychostimulant counterparts, synthetic cathinones appear to induce neurocognitive dysfunction and cytotoxicity, which are dependent on drug type, dose, frequency, and time following exposure. However, additional studies on synthetic cathinone-induced neuroinflammation are clearly needed, as are investigations into the neurochemical and neuroimmune mechanisms underlying their neurotoxic effects. Such endeavors may lead to novel therapeutic avenues to promote recovery in habitual synthetic cathinone users.

Stereoselective effects of the second-generation synthetic cathinone α-pyrrolidinopentiophenone (α-PVP): assessments of conditioned taste avoidance in rats

RATIONALE

Work with α-pyrrolidinopentiophenone (α-PVP), a second-generation synthetic cathinone, has been generally limited to the racemate. Given that with other synthetic cathinones, there are behavioral and neurochemical differences between their enantiomers, differences may also be seen with α-PVP.

OBJECTIVES

The present study assessed the relative contribution of each enantiomer to the aversive effects of racemic-α-PVP by comparing their ability to induce a conditioned taste avoidance.

METHODS

Adult male Sprague-Dawley rats were exposed every other day for four exposures to a novel saccharin solution followed immediately by an injection of 0 (saline vehicle) or 1.5, 3, or 6 mg/kg of S-, R-, or racemic-α-PVP (IP). On alternating days, all subjects were given access to water to assess any unconditioned effects of α-PVP on general fluid consumption.

RESULTS

Rats injected with the racemate and S-isomer of α-PVP displayed avoidance of the drug-associated saccharin solution, although this avoidance was dose-dependent only for the subjects injected with the racemate. There was no evidence of taste avoidance in animals injected with the R-enantiomer at any dose tested. Animals injected with 3 mg/kg racemic-α-PVP did not differ in avoidance from those treated with 1.5 mg/kg of the S-enantiomer, but subjects treated with 6 mg/kg racemic-α-PVP displayed a significantly stronger avoidance than those treated with 3 mg/kg S-α-PVP.

CONCLUSIONS

The present work suggests that the aversive effects of racemic α-PVP are mediated primarily by its S-isomer. The fact that at the highest dose tested (6 mg/kg), the racemate induces an avoidance greater than the simple additive effects of the S- and R-isomers (at 3 mg/kg) suggests that while the R-isomer may not induce taste avoidance at this dose, it may interact synergistically with the S-isomer in mediating the effects of the racemic mixture. These results were discussed in terms of similar effects with other behavioral and physiological endpoints reported with a number of psychostimulants and suggest that the enantiomers of α-PVP are an important variable in characterizing its behavioral effects.

DARK Classics in Chemical Neuroscience: α-Pyrrolidinovalerophenone ("Flakka")

Flakka (alpha-pyrrolidinovalerophenone, α-PVP) is a new psychoactive substance, chemically close to cathinone, the primary psychoactive alkaloid of khat ( Catha edulis). Like other synthetic cathinones, α-PVP is a potent inhibitor of the dopamine and norepinephrine transporters. Its robust clinical effects include hallucinations, arousal, aggression/violence, and euphoria. In animal models, α-PVP evokes hyperlocomotion and aberrant/stereotypic behaviors. Here, we discuss the history, synthesis, pharmacological mechanisms, metabolism, abuse potential, and societal impact of α-PVP. Today, α-PVP is a tightly controlled substance, currently banned in the United States and other countries worldwide. However, the growing abuse and complex central nervous system (CNS) effects of α-PVP remain poorly understood, necessitating further pharmacological and pharmacogenetic studies of this drug. Its interesting pharmacological profile (co-inhibition of dopamine and norepinephrine, but not serotonin, transporters) also calls for further studies of α-PVP in animal models, to dissect serotonergic from other monoaminergic mechanisms of action of drugs of abuse. Finally, screening α-PVP and related compounds in vivo may foster discovery of new CNS drugs, including developing novel CNS drugs and identifying their molecular targets.

The abuse-related effects of pyrrolidine-containing cathinones are related to their potency and selectivity to inhibit the dopamine transporter

Synthetic cathinones are common constituents of abused "bath salts" preparations and represent a large family of structurally related compounds that function as cocaine-like inhibitors or amphetamine-like substrates of dopamine (DAT), norepinephrine (NET), and serotonin (SERT) transporters. Preclinical evidence suggests that some cathinones (e.g., MDPV and α-PVP) are more effective reinforcers than prototypical stimulant drugs of abuse, such as cocaine or methamphetamine. Although the reinforcing potency of these cathinones is related to their potency to inhibit DAT, less is known about the pharmacological determinants of their unusually high reinforcing effectiveness. To this end, we tested the hypothesis that reinforcing effectiveness of cathinone stimulants is positively correlated with their selectivity for DAT relative to SERT. Uptake inhibition assays in rat brain synaptosomes were used to directly compare the potency of MDPV, MDPBP, MDPPP, α-PVP, α-PPP, and cocaine at DAT, NET, and SERT, whereas intravenous self-administration in rats was used to quantify relative reinforcing effectiveness of the drugs using progressive ratio (PR) and behavioral economic procedures. All cathinones were more potent at DAT than NET or SERT, with a rank order for selectivity at DAT over SERT of α-PVP > α-PPP > MDPV > MDPBP > MDPPP > cocaine. These synthetic cathinones were more effective reinforcers than cocaine, and the measures of reinforcing effectiveness determined by PR and demand curve analyses were highly correlated with selectivity for DAT over SERT. Together, these studies provide strong and convergent evidence that the abuse potential of stimulant drugs is mediated by uptake inhibition at DAT, with activity at SERT serving as a negative modulator of reinforcing effectiveness.

Quantification of endogenous neurotransmitters and related compounds by liquid chromatography coupled to tandem mass spectrometry

Neurotransmitters are signaling molecules, playing key roles in neuronal communications in the brain. Drug induced changes in neurotransmitters and other brain metabolite concentration may be used to characterize drugs according to their targeted metabolomics profile. Here, we report the development and validation of a straightforward liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the simultaneous quantification of 16 endogenous small polar compounds in rat plasma and brain homogenates. The method enables the quantification of the neurotransmitters γ-aminobutyric acid, glutamate, acetylcholine and adenosine, as well as choline, glutamine, acetylcarnitine, carnitine, creatine, creatinine, valine, leucine, isoleucine, phenylalanine, tyrosine and tryptophan. After optimizing the sample preparation, chromatographic and spectrometric conditions, the method was successfully validated using the standard addition approach and a hydrophilic interaction chromatography (HILIC) with an amide column. The method was shown to be linear (r > 0.99) as all the compounds were within the ±25% values of intra and inter-day precision and accuracy acceptance. A matrix effect was corrected with the use of 10 isotopically labelled internal standards and the compound stability was evaluated for all compounds. Relevant exaltation of choline (in plasma) and creatinine (in brain) were solved with -20 °C conditions. The applicability of the method was tested by evaluating brain alterations in the concentrations of neurotransmitters and related compounds after the administration of two psychostimulant drugs of abuse (cocaine and methylenedioxypyrovalerone) to rats. A neuro-metabolic fingerprint of each drug was obtained that reflected their pharmacological profile. Altogether, this methodology presents a valuable targeted metabolomics tool for basic and clinical research studies.

Dopamine D1-Like Receptor Agonist and D2-Like Receptor Antagonist (-)-Stepholidine Reduces Reinstatement of Drug-Seeking Behavior for 3,4-Methylenedioxypyrovalerone (MDPV) in Rats

Psychostimulant reinforcement is mediated by stimulation of both dopamine (DA) D1-like and D2-like receptors, suggesting that pharmacotherapy agents with a dual DA receptor mechanism may be useful for managing psychostimulant abuse. (-)-Stepholidine (L-SPD) is a Chinese herbal extract that functions as a D1-like receptor agonist and D2-like receptor antagonist. L-SPD has been shown to attenuate the reinforcing effects of heroin; however, its effects on the synthetic cathinone 3,4-methylenedioxypyrovalerone (MDPV) have not been examined. The current study determined the effects of L-SPD on reinstatement of MDPV-seeking behavior in the drug intravenous self-administration (IVSA) and conditioned place preference (CPP) paradigms. To determine whether the effects of L-SPD were specific to psychostimulant reinforcement, we also examined its effects on sucrose-seeking behavior. Using a locomotor activity assay, we tested the locomotor effects of L-SPD, as well as its effects on MDPV-induced hyperactivity. The results of a battery of in vitro binding and functional assays confirmed that L-SPD functioned as a D1-like receptor agonist and D2-like receptor antagonist. In behavioral experiments, L-SPD dose-dependently attenuated cue plus MDPV-primed reinstatement of MDPV-seeking behavior in the IVSA model. The highest dose of L-SPD also attenuated MDPV-primed reinstatement of MDPV CPP, as well as cue-induced reinstatement of sucrose-seeking. L-SPD had no significant locomotor effects, and did not modulate the robust hyperactivity induced by MDPV. The current findings show for the first time a robust reinstatement effect with MDPV, which can be reduced by L-SPD. These results establish a role for DA receptors in drug-seeking behavior for MDPV.

Acute Intoxications Involving α-Pyrrolidinobutiophenone (α-PBP): Results from the Swedish STRIDA Project

Introduction

Many new psychoactive substances (NPS) introduced as recreational drugs have been associated with severe intoxication and death.

Methods

Blood and/or urine samples were collected from intoxicated patients treated at Swedish hospitals that participated in the STRIDA project, a nationawide effort to address the growing problem of NPS. In patients undergoing evaluation for drug overdose, α-PBP was identified using liquid chromatography-mass spectrometry. Demographic and clinical data were collected during Poisons Information Centre consultations and retrieved from medical records.

Results

From April 2013 to November 2015, 43 patients tested positive for α-PBP. However, α-PBP was never specifically mentioned during consultation but only confirmed analytically. The α-PBP concentrations ranged 2.0–13,200 ng/mL in urine and 2.0–440 ng/mL in serum. The patients were aged 19–57 (mean 34) years, 81% were men, and 73% were known drug addicts. All cases except 1 also involved other NPS and/or classical drugs. MDPV, α-PVP, and other pyrovalerone analogues were the most common other NPS (31 cases; 72%). CNS depressants were detected in 28 cases (65%), with benzodiazepines (16 cases) being most frequent. Main clinical characteristics were agitation/anxiety (59%), tachycardia (54%), and hypertension (37%), and 14 patients (33%) required monitoring in the intensive care unit of which 8 were graded as severe intoxications. No fatalities were reported.

Conclusion

Patients with intoxication from α-PBP resembled those by NPS cathinones MDPV and α-PVP. As patients never specifically declared α-PBP intake and poly-drug intoxication was common, they may have been unaware of the actual substance taken.

The undead in culture and science

The undead have a significant role in mythology, religion, folklore, and literature. In the 1800s, the word zombie was used to describe reanimated corpses in the Caribbean who often worked on plantations doing long, arduous field work. The movie White Zombie was released in 1932 and exploited this folklore, but it ignored the fact that zombies represent one outcome in Vodou religious beliefs regarding death and the migration of spirits following death. The interest in zombies eventually led to sociological and medical investigations into zombification. Wade Davis reported that powders used by malevolent priests (bokors) contained tetrodotoxin, which could cause the neurologic changes underlying the zombie phenotype. Recent clinical studies have indicated that synthetic cannabinoids and synthetic cathinones can cause bizarre zombie-like behavior. According to Haitian folklore, zombies can develop when bokors reanimate someone who suddenly died from an acute illness or who was purposely poisoned. Recent studies in molecular biology suggest that the sequence of programmed cell death can be reversed when the stressor is removed and that cells, tissues, and bodies (at least in Drosophila flies) can recover. These scientific studies would support the remote possibility that the near dead might recover under certain circumstances but have residual neuropsychological dysfunction. Alternatively, the bokors could maintain control of their victims using drugs with properties similar to those of synthetic cannabinoids. The concept of zombification needs to be considered in the context of culture, religion, and science.

The synthetic cathinone α-pyrrolidinovalerophenone (α-PVP): pharmacokinetic and pharmacodynamic clinical and forensic aspects

New psychoactive substances (NPS), often referred as 'legal highs' or 'designer drugs', are derivatives and analogs of existing psychoactive drugs that are introduced in the recreational market to circumvent existing legislation on drugs of abuse. This work aims to review the state-of-the-art regarding chemical, molecular pharmacology, and in vitro and in vivo data on toxicokinetics of the potent synthetic cathinone α-pyrrolidinovalerophenone (α-PVP or flakka or zombie drug). Chemical, pharmacological, toxicological, and clinical effects of α-PVP were searched in PubMed (U.S. National Library of Medicine) and governmental websites without limitation of the period. α-PVP is a wide spread and easy to get special type of synthetic cathinone with seemingly powerful cocaine-like stimulant effects, high brain penetration, high liability for abuse and with increased risk of adverse effects such as tachycardia, agitation, hypertension, hallucinations, delirium, mydriasis, self-injury, aggressive behavior, and suicidal ideations. α-PVP undergoes extensive metabolism via different pathways and the α-PVP itself or its metabolites β-hydroxy-α-PVP and α-PVP lactam represent the main targets for toxicological analysis in urine. There is a limited knowledge regarding the short- and long-term effects of α-PVP and metabolites, and pharmacogenetic influence, hence further clinical and forensic toxicological studies are required. Moreover, since α-PVP cannot be detected with classic routine analysis procedures, statements on the frequency of their consumption cannot be made.

Gestational Exposure to the Synthetic Cathinone Methylenedioxypyrovalerone Results in Reduced Maternal Care and Behavioral Alterations in Mouse Pups

The member of synthetic cathinone family, methylenedioxypyrovalerone (MDPV), is a frequently used psychoactive drug of abuse. The objective of our study was to determine the effect of MDPV (administered from the 8th to the 14th day of gestation) on the behavior of neonatal and adolescent mice, as well as its effect on maternal care. We measured maternal care (pup retrieval test, nest building), locomotor activity (open field test), and motor coordination (grip strength test) of dams, whereas on pups we examined locomotor activity at postnatal day 7 and day 21 (open field test) and motor coordination on day 21 (grip strength test). On fresh-frozen brain samples of the dams we examined the expression of two important peptides implicated in the regulation of maternal behavior and lactation: tuberoinfundibular peptide 39 (TIP39) mRNA in the thalamic posterior intralaminar complex, and amylin mRNA in the medial preoptic nucleus. We detected decreased birth rate and survival of offspring, and reduced maternal care in the drug-treated animals, whereas there was no difference between the motility of treated and control mothers. Locomotor activity of the pups was increased in the MDPV treated group both at 7 and 21 days of age, while motor coordination was unaffected by MDPV treatment. TIP39 and amylin were detected in their typical location but failed to show a significant difference of expression between the drug-treated and control groups. The results suggest that chronic systemic administration of the cathinone agent MDPV to pregnant mice can reduce birth rate and maternal care, and it also enhances motility (without impairment of motor coordination) of the offspring.

Comparing rewarding and reinforcing properties between 'bath salt' 3,4-methylenedioxypyrovalerone (MDPV) and cocaine using ultrasonic vocalizations in rats

Abuse of synthetic psychostimulants like synthetic cathinones has risen in recent years. 3,4-Methylenedioxypyrovalerone (MDPV) is one such synthetic cathinone that demonstrates a mechanism of action similar to cocaine. Compared to cocaine, MDPV is more potent at blocking dopamine and norepinephrine reuptake and is readily self-administered by rodents. The present study compared the rewarding and reinforcing properties of MDPV and cocaine using systemic injection dose-response and self-administration models. Fifty kilohertz ultrasonic vocalizations (USVs) were recorded as an index of positive affect throughout experiments. In Experiment 1, MDPV and cocaine dose-dependently elicited 50-kHz USVs upon systemic injection, but MDPV increased USVs at greater rates and with greater persistence relative to cocaine. In Experiment 2, latency to begin MDPV self-administration was shorter than latency to begin cocaine self-administration, and self-administered MDPV elicited greater and more persistent rates of 50-kHz USVs versus cocaine. MDPV-elicited 50-kHz USVs were sustained over the course of drug load-up whereas cocaine-elicited USVs waned following initial infusions. Notably, we observed a robust presence of context-elicited 50-kHz USVs from both MDPV and cocaine self-administering rats. Collectively, these data suggest that MDPV has powerfully rewarding and reinforcing effects relative to cocaine at one-tenth doses. Consistent with prior work, we additionally interpret these data in supporting that MDPV has significant abuse risk based on its potency and subjectively positive effects. Future studies will be needed to better refine therapeutic strategies targeted at reducing the rewarding effects of cathinone analogs in efforts to ultimately reduce abuse liability.

MDPV in forensic routine cases: Psychotic and aggressive behavior in relation to plasma concentrations

The new psychoactive substance 3,4-methylenedioxypyrovalerone (MDPV) belongs to the group of synthetic cathinones and is purchased mainly as "research chemical" or "bath salt" on the illegal drug market, also in South Bavaria. MDPV was detected in blood and urine samples from 2010 on in 50 authentic routine cases in a forensic setting. Plasma concentrations in 46 cases with available blood specimens ranged from approximately 1.0 to 301μg/L (median 23.7; mean 47.9μg/L), detected by a fully validated LC-MS/MS method. Subjects aged between 16 and 54 years (median 36; mean 35 years) and reflected experienced chronic drug users. Accused offences were mainly violent crimes such as bodily harm, robberies, homicides and acts of resistance. A lot of subjects showed highly aggressive and violent behavior with endangerment of self and others and/or psychotic symptoms as confusion, hallucinations or paranoia. The risk for such behavior rises with MDPV plasma concentrations above as low as 30μg/L, whereby a time interval of 1.5h on average between incident and/or observation of impairment and blood sampling has to be taken into account. Comprehensive toxicological analysis proved poly-drug use in almost all cases including opiates/opioids, benzodiazepines and other sedatives, antidepressants and other stimulants, also other new psychoactive substances. Alcohol was detected only in three cases. Co-consumed benzodiazepines seem not be able to completely prevent psychotic effects despite their use as first-line treatment for patients with synthetic cathinone poisonings. The study demonstrates that relatively low plasma concentrations of MDPV could be associated with mental impairment which is relevant in the assessment of forensic cases.

Repeated exposure to 3,4-methylenedioxypyrovalerone and cocaine produces locomotor sensitization with minimal effects on brain monoamines

Synthetic cathinones, known as "bath salts" on the illicit drug market, pose a significant public health concern. 3,4-Methylenedioxypyrovalerone (MDPV), one of several popular constituents of illicit bath salts, produces similar pharmacological actions to cocaine, albeit with greater potency and efficacy. The present study sought to characterize behavioral and neurochemical effects of repeated exposure to MDPV alone and in combination with cocaine. Male Sprague-Dawley rats were randomly assigned to one the following four treatments, administered once daily for seven days: 1 mg/kg MDPV, 5 mg/kg cocaine, 1 mg/kg MDPV +5 mg/kg cocaine, or saline. Locomotor activity was assessed for 1 h immediately before and 1 h immediately after injections on days 1 and 6. Brains were harvested 20 min after the final injection on day 7 and brain tissue punches were obtained to determine monoamine content within the anterior striatum, medial prefrontal cortex, and nucleus accumbens using High-Performance Liquid Chromatography (HPLC). Drug-induced increases in horizontal activity were significantly greater on treatment day 6 compared to treatment day 1 in all three drug treatment groups in comparison to the saline control group. MDPV produced significantly higher increases in activity compared to either saline or cocaine, although concurrent treatment with MDPV and cocaine produced sub-additive effects. Neurochemical analyses provided no evidence of alterations in total monoamine content following repeated administration of MDPV, cocaine, or the MDPV + COC mixture. Further investigations targeting possible changes in DA receptor sensitivity following repeated exposure to MDPV may help elucidate the mechanistic changes responsible for MDPV-induced behavioral sensitization. This article is part of the Special Issue entitled 'Designer Drugs and Legal Highs.'