Neuropharmacology of 3,4-Methylenedioxypyrovalerone (MDPV), Its Metabolites, and Related Analogs

The synthetic cathinones MDPHP and MDPV: Comparison of the acute effects in mice, in silico ADMET profiles and clinical reports

The 3,4-methylenedioxy-alpha-pyrrolidinohexanophenone (MDPHP) is a synthetic cathinone closely related to 3,4-methylenedioxypyrovalerone (MDPV), one of the most common synthetic cathinones present in the "bath salts". MDPHP has recently gained attention due to increasing seizures and involvement in human intoxications which occurred in Europe and Italy in the last years, but currently there is a lack of information about its pharmaco-toxicological effects. With the aim at filling this gap, the present study is endeavoured to (i) evaluate the effects of acute administration of MDPHP (0.01-20 mg/kg; i.p.) on behaviour, cardiorespiratory and cardiovascular parameters in CD-1 male mice, comparing them to those observed after administration of MDPV; (ii) predict the ADMET profile of the two analogues using the Plus ADMET Predictor®; (iii) present clinical data related to MDPHP and MDPV-induced intoxications recorded between 2011 and 2023 by the Pavia Poison Control Centre (PCC) - National Toxicology Information Centre (Istituti Clinici Scientifici Maugeri, IRCCS Pavia, Italy). Our results substantiated that MDPHP and MDPV similarly affect sensorimotor and behavioural responses in mice, importantly increased locomotion and induced aggressive behaviour, and, at higher dosage, increased heart rate and blood pressure. These findings are in line with those observed in humans, revealing severe toxidromes typically characterized by Central Nervous System (CNS) alterations (behavioural/neuropsychiatric symptoms), including psychomotor agitation and aggressiveness, cardiovascular and respiratory disorders (e.g. tachycardia, hypertension, dyspnoea), and other peripheral symptoms (e.g. hyperthermia, acidosis, rhabdomyolysis).

MDPV (3,4-methylenedioxypyrovalerone) administered to mice during development of the central nervous system produces persistent learning and memory impairments

BACKGROUND

Synthetic cathinones (SC) constitute the second most frequently abused class of new psychoactive substances. They serve as an alternative to classic psychostimulatory drugs of abuse, such as methamphetamine, cocaine, or 3,4-methylenedioxymethamphetamine (MDMA). Despite the worldwide prevalence of SC, little is known about their long-term impact on the central nervous system. Here, we examined the effects of repeated exposure of mice during infancy, to 3,4-methylenedioxypyrovalerone (MDPV), a SC potently enhancing dopaminergic neurotransmission, on learning and memory in young adult mice.

METHODS

All experiments were performed on C57BL/6J male and female mice. Animals were injected with MDPV (10 or 20 mg/kg) and BrdU (bromodeoxyuridine, 25 mg/kg) during postnatal days 11-20, which is a crucial period for the development of their hippocampus. At the age of 12 weeks, mice underwent an assessment of various types of memory using a battery of behavioral tests. Afterward, their brains were removed for detection of BrdU-positive cells in the dentate gyrus of the hippocampal formation with immunohistochemistry, and for measurement of the expression of synaptic proteins, such as synaptophysin and PSD95, in the hippocampus using Western blot.

RESULTS

Exposure to MDPV resulted in impairment of spatial working memory assessed with Y-maze spontaneous alternation test, and of object recognition memory. However, no deficits in hippocampus-dependent spatial learning and memory were found using the Morris water maze paradigm. Consistently, hippocampal neurogenesis and synaptogenesis were not interrupted. All observed MDPV effects were sex-independent.

CONCLUSIONS

MDPV administered repeatedly to mice during infancy causes learning and memory deficits that persist into adulthood but are not related to aberrant hippocampal development.

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.

First-Generation Synthetic Cathinones Produce Arrhythmia in Zebrafish Eleutheroembryos: A New Approach Methodology for New Psychoactive Substances Cardiotoxicity Evaluation

The increasing number of new psychoactive substances (NPS) entering the illicit drug market, especially synthetic cathinones, as well as the risk of cardiovascular complications, is intensifying the need to quickly assess their cardiotoxic potential. The present study aims to evaluate the cardiovascular toxicity and lethality induced by first-generation synthetic cathinones (mephedrone, methylone, and MDPV) and more classical psychostimulants (cocaine and MDMA) in zebrafish embryos using a new approach methodology (NAM). Zebrafish embryos at 4 dpf were exposed to the test drugs for 24 h to identify drug lethality. Drug-induced effects on ventricular and atrial heart rate after 2 h exposure were evaluated, and video recordings were properly analyzed. All illicit drugs displayed similar 24 h LC50 values. Our results indicate that all drugs are able to induce bradycardia, arrhythmia, and atrial-ventricular block (AV block), signs of QT interval prolongation. However, only MDPV induced a different rhythmicity change depending on the chamber and was the most potent bradycardia and AV block-inducing drug compared to the other tested compounds. In summary, our results strongly suggest that the NAM presented in this study can be used for screening NPS for their cardiotoxic effect and especially for their ability to prolong the QT intervals.

Persistent binding at dopamine transporters determines sustained psychostimulant effects

Psychostimulants interacting with the dopamine transporter (DAT) can be used illicitly or for the treatment of specific neuropsychiatric disorders. However, they can also produce severe and persistent adverse events. Often, their pharmacological properties in vitro do not fully correlate to their pharmacological profile in vivo. Here, we investigated the pharmacological effects of enantiomers of pyrovalerone, α-pyrrolidinovalerophenone, and 3,4-methylenedioxypyrovalerone as compared to the traditional psychostimulants cocaine and methylphenidate, using a variety of in vitro, computational, and in vivo approaches. We found that in vitro drug-binding kinetics at DAT correlate with the time-course of in vivo psychostimulant action in mice. In particular, a slow dissociation (i.e., slow koff) of S-enantiomers of pyrovalerone analogs from DAT predicts their more persistent in vivo effects when compared to cocaine and methylphenidate. Overall, our findings highlight the critical importance of drug-binding kinetics at DAT for determining the in vivo profile of effects produced by psychostimulant drugs.

Pharmaco-Toxicological Effects of Atypical Synthetic Cathinone Mephtetramine (MTTA) in Mice: Possible Reasons for Its Brief Appearance over NPSs Scene

Over the last year, NPSs have been steadily on the rise in the illicit drug market. Among these, synthetic cathinones seem to become increasingly popular among young adults, mainly because of their ability to replicate the effects of traditional psychostimulant drugs, such as cocaine, MDMA and amphetamines. However, scarce data are available about the in vivo pharmaco-toxicology of these new substances. To this end, this study focused on evaluation of effects induced by repeated administration of mephtetramine (MTTA 0.1-30 mg/kg i.p.) in mice. This atypical cathinone highlighted a sensorial (inhibition of visual and acoustic reflexes) and transient physiological parameter (decrease in breath rate and temperature) change in mice. Regarding motor activity, both a dose-dependent increase (accelerod test) and biphasic effect (drag and mobility time test) have been shown. In addition, blood and urine samples have been analysed to enrich the experimental featuring of the present study with reference to evaluation of potential toxicity related to consumption of MTTA. The latter analysis has particularly revealed important changes in blood cells count and blood and urine physicochemical profile after repeated treatment with this atypical cathinone. Moreover, MTTA induced histological changes in heart, kidney and liver samples, emphasizing its potential toxicity.

Psychedelic drug abuse potential assessment research for new drug applications and Controlled Substances Act scheduling

New medicines containing classic hallucinogenic and entactogenic psychedelic substance are under development for various psychiatric and neurological disorders. Many of these, including psilocybin, lysergic acid diethylamide (LSD), and 3,4-methylenedioxymethamphetamine (MDMA) are Schedule I controlled substances of the United States Controlled Substances Act (US CSA), and similarly controlled globally. The implications of the CSA for research and medicines development, the path to approval of medicines, and their subsequent removal from Schedule I in the US are discussed. This entire process occurs within the framework of the CSA in the US and its counterparts internationally in accordance with international drug control treaties. Abuse potential related research in the US informs the eight factors of the CSA which provide the basis for rescheduling actions that must occur upon approval of a drug that contains a Schedule I substance. Abuse-related research also informs drug product labeling and the risk evaluation and mitigation strategies (REMS) will likely be required for approved medicines. Human abuse potential studies typically employed in CNS drug development may be problematic for substances with strong hallucinogenic effects such as psilocybin, and alternative strategies are discussed. Implications for research, medicinal development, and controlled substance scheduling are presented in the context of the US CSA and FDA requirements with implications for global regulation. We also discuss how abuse-related research can contribute to understanding mechanisms of action and therapeutic effects as well as the totality of the effects of the drugs on the brain, behavior, mood, and the constructs of spirituality and consciousness.

Sex-dependent Effects of the Drugs of Abuse Amphetamine and the Smart Drug 3,4-Methylenedioxypyrovalerone on Fear Memory Generalization in Rats

In recent years there has been an increase in the development of new synthetic drugs, among which the "bath salt" 3,4-methylenedioxypyrovalerone (MDPV), a psychostimulant with a mechanism of action similar to those of cocaine and amphetamine, stands out. Drugs of abuse have been consistently shown to affect memory function in male rodents. We have recently shown that amphetamine and MDPV induce generalization of fear memory in an inhibitory avoidance discrimination task in male rats. Although abuse of illicit drugs is more prevalent in men than in women, several studies have demonstrated that females are more vulnerable to the effects of drugs of abuse than males and the effects caused by substance dependence on memory in females are still under-investigated. Thus, we examined the effects of subchronic amphetamine or MDPV administrations on memory in a contextual fear conditioning/generalization paradigm in adult male and female rats. Animals were given daily subchronic injections of the drugs, starting 6 days prior the beginning of the behavioral procedures until the end of the paradigm. On day 1 of the experimental protocol, all rats were exposed to a safe context and, the day after, to a slightly different chamber where they received an unsignaled footshock. Twenty-four and forty-eight hours later, freezing behavior and emission of 22 kHz-ultrasonic vocalizations (USVs) were measured in the two different contexts to assess fear memory retention and generalization. Our results indicate that MDPV treatment altered freezing in both sexes, USVs were affected by amphetamine in males while by MDPV in females.

Ethanol enhanced MDPV- and cocaine-induced aggressive behavior in mice: Forensic implications

BACKGROUND

Reports concerning the causal link between aggressive behavior and use and abuse of different substances (i.e., alcohol, MDPV) can be found in the literature. Nonetheless, the topic concerning the effects of acute ethanol administration on MDPV and cocaine induced aggressive behavior has yet to be thoroughly investigated. The aim of this study was to investigate such synergistic effects.

MATERIALS AND METHODS

A total of 360 male mice were employed in the study. Ethanol was diluted with saline solution and administered 10 min before MDPV or cocaine injection via oral gavage needles. Similarly, MDPV and cocaine were dissolved in saline solution and administered by intraperitoneal injection. Different associations of specific drug doses were then tested. To investigate the acute effects of MDPV and cocaine and their interaction with ethanol on aggression in mice, a resident-intruder test was used.

RESULTS

Ethanol alone was ineffective at dosages of 0.05 g/kg and 0.25 g/kg but increased the aggressiveness of the mice at 0.125 g/kg. Similarly, the injection of both cocaine alone and MDPV alone did not significantly increase the aggressiveness of the mice; conversely, the combination of ethanol and cocaine and ethanol and MDPV enhanced aggression at specific ethanol dosages (0.05 g/kg and 0.125 g/kg).

CONCLUSION

This study demonstrated that acute ethanol administration enhances MDPV- and cocaine-induced aggressive behavior in mice. This aggressive response is particularly enhanced when MDVP and cocaine are coupled with specific ethanol dosages, proving that psychostimulant drugs may act synergistically under certain conditions.

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.

Cannabidiol Modulates the Motivational and Anxiety-Like Effects of 3,4-Methylenedioxypyrovalerone (MDPV) in Mice

3,4-Methylenedioxypyrovalerone (MDPV) is a new psychoactive substance (NPS) and the most widespread and life-threatening synthetic cathinone of the "bath salts". Preclinical research has proven the cocaine-like psychostimulant effects of MDPV and its potential for abuse. Cannabidiol (CBD) is a non-psychotropic phytocannabinoid that has emerged as a new potential treatment for drug addiction. Here, we tested the effects of CBD (20 mg/kg) on MDPV (2 mg/kg)-induced conditioned place preference and MDPV (0.05 and 0.075 mg/kg/infusion) self-administration paradigms. In addition, we assessed the effects of the co-administration of CBD and MDPV (3 and 4 mg/kg) on anxiety-like behaviour using the elevated plus maze (EPM). CBD mitigated the MDPV-induced conditioned place preference. On the contrary, CBD administration throughout the MDPV (0.075 mg/kg/infusion) self-administration increased drug-seeking and taking behaviours, but only in the high-responders group of mice. Furthermore, CBD exerted anxiolytic-like effects, exclusively in MDPV-treated mice. Taken together, our results indicate that CBD modulation of MDPV-induced motivational responses in mice varies depending on the requirements of the learning task, resulting in a complex response. Therefore, further research attempting to decipher the behavioural and molecular interactions between CBD and MDPV is needed.

An updated review on synthetic cathinones

Cathinone, the main psychoactive compound found in the plant Catha edulis Forsk. (khat), is a β-keto analogue of amphetamine, sharing not only the phenethylamine structure, but also the amphetamine-like stimulant effects. Synthetic cathinones are derivatives of the naturally occurring cathinone that largely entered the recreational drug market at the end of 2000s. The former "legal status", impressive marketing strategies and their commercial availability, either in the so-called "smartshops" or via the Internet, prompted their large spread, contributing to their increasing popularity in the following years. As their popularity increased, the risks posed for public health became clear, with several reports of intoxications and deaths involving these substances appearing both in the social media and scientific literature. The regulatory measures introduced thereafter to halt these trending drugs of abuse have proved to be of low impact, as a continuous emergence of new non-controlled derivatives keep appearing to replace those prohibited. Users resort to synthetic cathinones due to their psychostimulant properties but are often unaware of the dangers they may incur when using these substances. Therefore, studies aimed at unveiling the pharmacological and toxicological properties of these substances are imperative, as they will provide increased expertise to the clinicians that face this problem on a daily basis. The present work provides a comprehensive review on history and legal status, chemistry, pharmacokinetics, pharmacodynamics, adverse effects and lethality in humans, as well as on the current knowledge of the neurotoxic mechanisms of synthetic cathinones.

Discriminative-Stimulus Effects of Synthetic Cathinones in Squirrel Monkeys

BACKGROUND

Synthetic cathinones display overlapping behavioral effects with psychostimulants (e.g., methamphetamine [MA]) and/or entactogens (e.g., 3,4-methylenedioxymethaphetamine [MDMA])-presumably reflecting their dopaminergic and/or serotonergic activity. The discriminative stimulus effects of MDMA thought to be mediated by such activity have been well characterized in rodents but have not been fully examined in nonhuman primates.

METHODS

The present studies were conducted to systematically evaluate the discriminative stimulus effects of 5 abused synthetic cathinones (methylenedioxypyrovalerone [MDPV], α-pyrrolidinovalerophenone [α-PVP], methcathinone [MCAT], mephedrone, and methylone) in adult male squirrel monkeys trained to distinguish intramuscular injections of MA (0.1 mg/kg; n = 4) or MDMA (0.6 mg/kg; n = 4) from vehicle.

RESULTS

Each training drug produced dose-dependent effects and, at the highest dose, full substitution. MDMA produced predominantly vehicle-like responding in the MA-trained group, whereas the highest dose of MA (0.56 mg/kg) produced partial substitution (approximately 90% appropriate lever responding in one-half of the subjects) in the MDMA-trained group. MDPV, α-PVP, and MCAT produced full substitution in MA-trained subjects, but, at the same or higher doses, only substituted for MDMA in one-half of the subjects, consistent with primarily dopaminergically mediated interoceptive effects. In contrast, mephedrone and methylone fully substituted in MDMA-trained subjects but failed to fully substitute for the training drug in MA-trained subjects, suggesting a primary role for serotonergic actions in their interoceptive effects.

CONCLUSIONS

These findings suggest that differences in the interoceptive effects of synthetic cathinones in nonhuman primates reflect differing compositions of monoaminergic actions that also may mediate their subjective effects in humans.

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.

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.

Naphyrone (naphthylpyrovalerone): Pharmacokinetics, behavioural effects and thermoregulation in Wistar rats

Naphthylpyrovalerone (naphyrone) is a pyrovalerone cathinone that potently inhibits monoamine transporters and provides stimulatory-entactogenic effects. Little is known about the safety of naphyrone or its effects in vivo, and more research is needed to acquire knowledge about its fundamental effects on physiology and behaviour. Our objective was to investigate naphyrone's pharmacokinetics, acute toxicity, hyperthermic potential and stimulatory and psychotomimetic properties in vivo in male Wistar rats. Pharmacokinetics after 1 mg/kg subcutaneous (sc.) naphyrone were measured over 6 h in serum, the brain, liver and lungs. Rectal temperature (degree Celsius) was measured over 10 h in group-versus individually housed rats after 20 mg/kg sc. In the behavioural experiments, 5, 10 or 20 mg/kg of naphyrone was administered 15 or 60 min prior to testing. Stimulation was assessed in the open field, and sensorimotor processing in a prepulse inhibition (PPI) task. Peak concentrations of naphyrone in serum and tissue were reached at 30 min, with a long-lasting elevation in the brain/serum ratio, consistent with observations of lasting hyperlocomotion in the open field and modest increases in body temperature. Administration of 20 mg/kg transiently enhanced PPI. Naphyrone crosses the blood-brain barrier rapidly and is eliminated slowly, and its long-lasting effects correspond to its pharmacokinetics. No specific signs of acute toxicity were observed; therefore, clinical care and harm-reduction guidance should be in line with that available for other stimulants and cathinones.

Alpha-Pyrrolidinopentiothiophenone (α-PVT): A forensic case study including plasma concentrations

Alpha-Pyrrolidinopentiothiophenone (α-PVT) belongs to the drug class of pyrrolidinophenones, a subgroup of synthetic cathinones, which are among the most prevalent new psychoactive substances. The study describes a series of 44 authentic forensic cases with analytical confirmed intake of α-PVT. Plasma concentrations, determined by a validated LC-MS/MS method, ranged from ca. 0.9 to 306 µg/L (median 35.6; mean 66.6 µg/L). Comprehensive toxicological analysis proved excessive co-consumption in almost all cases, including other pyrovalerones and classic stimulants as well as central depressant drugs such as opiates/opioids, benzodiazepines, pregabalin and/or ethanol. Subjects were aged between 26 and 54 years (median 35 years, mean 36 years) and appeared to be mainly experienced intravenous drug consumers. A high incidence of aberrant behavior in terms of aggressive, combative behavior and psychotic changes could be observed, as also reflected in accused offences, which frequently presented violent crimes. In consideration of several confounding factors, the study suggests a relationship between frequency of such impairment and plasma concentrations of α-PVT, but individual cases without signs of behavioral changes and high plasma concentrations also occurred, which might be explained by developed tolerance and/or individual vulnerably for the psychotic effects of pyrovalerones.

A Review of Synthetic Cathinone-Related Fatalities From 2017 to 2020

BACKGROUND

Synthetic cathinones (SCs) are designer analogs of the natural active principle of khat. Since their appearance on the black market in 2003, their popularity has increased annually, and they have become the most seized class of new psychoactive substances reported to the UNODC Early Warning Advisory system. The constant introduction of newly synthesized molecules makes this issue difficult to monitor. The authors reviewed the most recent SC-related fatalities worldwide to highlight new trends of consumption, reporting acute pharmacological and toxicological symptoms, scene investigations, analytical methods, and reported SC concentrations in diverse biological matrices.

METHODS

A literature search was performed using scientific databases such as PubMed, Scopus, Science Direct, Web of Science, and Research Gate to identify relevant scientific publications from 2017 to 2020. In addition, a search was conducted through the EU EWS.

RESULTS

From 2017 to 2020, 31 different SCs were identified in 75 reported fatal intoxications in the literature, alone or in combination with other substances. The most abused SCs were N-ethylpentylone, N-ethylhexedrone, and 4-chloromethcathinone. The EU EWS included less detail on 72 additional SC-related fatalities from 2017 to 2020.

CONCLUSIONS

New SCs continuously replace older natural and synthetic stimulant drugs, making determining the cause of death difficult. Analytical methods and high-performance mass spectrometry instruments are essential to detect the low concentrations of these potent new SCs. Little data are available on the pharmacology of these new drugs; the evaluation of toxicological antemortem and postmortem findings provides critical data on the drug's pharmacology and toxicology and for the interpretation of new SC cases.

Pharmacotherapy of Patients Taking New Psychoactive Substances: A Systematic Review and Analysis of Case Reports

Background: In recent years, an increase in the frequency of hospitalizations of patients taking newer and newer psychoactive substances has been observed around the world. Each year, authors publish case reports of patients who consumed previously unknown NPS. Most publications of this type concern the period between 2014 and 2016. However, no publication systematically reviews the pharmacotherapy used in these cases. This study aims to review the case reports of patients taking NPS published between 2010 and 2019, as well as analyzing the pharmacotherapy used. Methods: We searched the Thomson (Web of Knowledge), PubMed/Medline, Science Direct, Scopus and Google Scholar databases. The search was performed using all possible combinations of the term "case report" describing the use of NPS, also referred to as designer medications, internet medications, research chemicals and herbal highs. Results: We analyzed 51 case reports on the intake of various types of NPS. Most of them (p < 0.001) concerned the use of synthetic cannabinoids (41.2%) and cathinones (31.4%). The pharmacotherapy applied primarily (p < 0.001) consisted of administering benzodiazepines to patients (62.7%), most of whom took only this group of medications (25.5%), followed by groups receiving benzodiazepines combined with neuroleptics (15.7%) and muscle relaxants (11.8%). Opioids were administered primarily to patients taking synthetic opioids (p < 0.001). Of the 5 cases of deaths from NPS reported in the literature, three relate specifically to the synthetic opioid MT-45. The later the time period, the more medications patients were administered (p = 0.02). Conclusion: In the pharmacotherapy for NPS poisoning, one should focus primarily on combating psychomotor agitation.

In vivo toxicometabolomics reveals multi-organ and urine metabolic changes in mice upon acute exposure to human-relevant doses of 3,4-methylenedioxypyrovalerone (MDPV)

3,4-Methylenedioxypyrovalerone (MDPV) is consumed worldwide, despite its potential to cause toxicity in several organs and even death. There is a recognized need to clarify the biological pathways through which MDPV elicits general and target-organ toxicity. In this work, a comprehensive untargeted GC-MS-based metabolomics analysis was performed, aiming to detect metabolic changes in putative target organs (brain, heart, kidneys and liver) but also in urine of mice after acute exposure to human-relevant doses of MDPV. Male CD-1 mice received binge intraperitoneal administrations of saline or MDPV (2.5 mg/kg or 5 mg/kg) every 2 h, for a total of three injections. Twenty-four hours after the first administration, target organs, urine and blood samples were collected for metabolomics, biochemical and histological analysis. Hepatic and renal tissues of MDPV-treated mice showed moderate histopathological changes but no significant differences were found in plasma and tissue biochemical markers of organ injury. In contrast, the multivariate analysis significantly discriminated the organs and urine of MDPV-treated mice from the control (except for the lowest dose in the brain), allowing the identification of a panoply of metabolites. Those levels were significantly deviated in relation to physiological conditions and showed an organ specific response towards the drug. Kidneys and liver showed the greatest metabolic changes. Metabolites related with energetic metabolism, antioxidant defenses and inflammatory response were significantly changed in the liver of MDPV-dosed animals, while the kidneys seem to have developed an adaptive response against oxidative stress caused by MDPV. On the other hand, the dysregulation of metabolites that contribute to metabolic acidosis was also observed in this organ. The heart showed an increase of fatty acid biosynthesis, possibly as an adaptation to maintain the cardiac energy homeostasis. In the brain, changes in 3-hydroxybutyric acid levels may reflect the activation of a neurotoxic pathway. However, the increase in metabolites with neuroprotective properties seems to counteract this change. Metabolic profiling of urine from MDPV-treated mice suggested that glutathione-dependent antioxidant pathways may be particularly involved in the compensatory mechanism to counteract oxidative stress induced by MDPV. Overall, this study reports, for the first time, the metabolic profile of liver, kidneys, heart, brain, and urine of MDPV-dosed mice, providing unique insights into the biological pathways of toxicity. Our findings also underline the value of toxicometabolomics as a robust and sensitive tool for detecting adaptive/toxic cellular responses upon exposure to a physiologically relevant dose of a toxic agent, earlier than conventional toxicity tests.

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.

Active vaccination reduces reinforcing effects of MDPV in male Sprague-Dawley rats trained to self-administer cocaine

RATIONALE

3,4-Methylenedioxypyrovalerone (MDPV) is a synthetic cathinone abused for its cocaine-like psychostimulant effects in "bath salts" products. While there are currently no pharmacotherapies for MDPV abuse, rodent studies suggest immunotherapy may offer a feasible treatment option.

OBJECTIVES

These studies tested the capacity of active vaccination to reduce the reinforcing effects of MDPV in Sprague-Dawley rats.

METHODS

Rats acquired cocaine self-administration (0.32 mg/kg/inf) on an FR1 schedule. Dose-effect functions for cocaine (0.032-1.0 mg/kg/inf) and MDPV (0.001-0.32 mg/kg/inf) were determined under an FR5 schedule. Rats in the vaccine group were immunized during cocaine self-administration. All rats transitioned to a progressive-ratio (PR) schedule to establish breakpoints for cocaine (0.1-1.0 mg/kg/inf) and MDPV (0.01-0.32 mg/kg/inf). Responding was extinguished, and cue-induced and MDPV-primed reinstatement (0.56 mg/kg, IP) were evaluated.

RESULTS

No endpoints of cocaine self-administration differed between groups, but the ED₅₀ for MDPV self-administration was significantly lower in control relative to vaccinated rats. Under the PR schedule, MDPV was ~ 2.5-fold more potent in maintaining responding in control than vaccinated rats, but E_max was not different between groups. Vaccination did not reduce MDPV-primed reinstatement, perhaps due to a decrease in antibody titer.

CONCLUSIONS

Vaccination did not alter acquisition of cocaine self-administration, demonstrating pharmacological selectivity and suggesting that the vaccine did not affect learning or motivation, while effectively reducing the potency of MDPV as a reinforcer. The protective effects of the vaccine were surmounted by large unit doses of MDPV, suggesting maximal efficacy of drug-conjugate vaccines in substance abuse disorders will likely require concurrent behavior modification therapy.

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.

3,4-Methylenedioxypyrovalerone: Neuropharmacological Impact of a Designer Stimulant of Abuse on Monoamine Transporters

Methylenedioxypyrovalerone (MDPV) is an abused synthetic cathinone, commonly referred to as a "bath salt." Because the dopamine (DA) transporter (DAT) and vesicular monoamine transporter-2 (VMAT-2) are key regulators of both the abuse and neurotoxic potential of structurally and behaviorally related agents, the impact of MDPV on these transporters was investigated. Results revealed that a single in vivo MDPV administration rapidly (within 1 hour) and reversibly increased both rat striatal DAT and VMAT-2 activity, as assessed via [³H]DA uptake in synaptosomes and synaptic vesicles, respectively, prepared from treated rats. There was no evidence of an MDPV-induced increase in plasmalemmal membrane DAT surface expression. Plasma concentrations of MDPV increased dose-dependently as assessed 1 hour after 2.5 and 5.0 mg/kg (s.c.) administration and returned to levels less than 10 ng/ml by 18 hours after 2.5 mg/kg (s.c.). Neither pretreatment with a D1 receptor (SCH23390), a D2 receptor (eticlopride), nor a nicotinic receptor (mecamylamine) antagonist attenuated the MDPV-induced increase in DAT activity. In contrast, eticlopride pretreatment attenuated both the MDPV-induced increase in VMAT-2-mediated DA uptake and an associated increase in cytoplasmic-associated vesicle VMAT-2 immunoreactivity. SCH23390 did not attenuate the MDPV-induced increase in VMAT-2 activity. Repeated MDPV injections did not cause persistent DAergic deficits, as assessed 7 to 8 days later. The impact of MDPV on striatal and hippocampal serotonergic assessments was minimal. Taken together, these data contribute to a growing pharmacological rubric for evaluating the ever-growing list of designer cathinone-related stimulants. The profile of MDPV compared with related psychostimulants is discussed. SIGNIFICANCE STATEMENT: Pharmacological characterization of the synthetic cathinone, 3,4-methylenedioxypyrovalerone (MDPV; commonly referred to as a "bath salt"), is critical for understanding the abuse liability and neurotoxic potential of this and related agents. Accordingly, the impact of MDPV on monoaminergic neurons is described and compared with that of related psychostimulants.

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.

Reinforcing Effects of the Synthetic Cathinone α-Pyrrolidinopropiophenone (α-PPP) in a Repeated Extended Access Binge Paradigm

Synthetic cathinones are designer psychostimulants that are derivatives of the natural alkaloid cathinone, and produce effects similar to more traditional illicit stimulants such as cocaine and methamphetamine. The pyrovalerone cathinones methylenedioxypyrovalerone (MDPV) and α-pyrrolidinopropiophenone (α-PPP) exert their effects via inhibition of presynaptic dopamine and norepinephrine reuptake transporters. While the reinforcing effects of MDPV in rodents are well-established, very few studies have examined self-administration patterns of α-PPP. Users of synthetic cathinones often engage in repeated binge episodes of drug intake that last several days. We therefore sought to determine the reinforcing effects of three doses of α-PPP (0.05, 0.1 and 0.32 mg/kg/infusion) under conditions of prolonged binge-like access conditions, with three 96-h periods of drug access interspersed with 72 h of abstinence. MDPV (0.05 mg/kg/infusion) was used as a comparison drug. Our results show that both MDPV and the high (0.32 mg/kg/infusion) dose of α-PPP are readily self-administered at high levels across all three extended access periods, whereas lower doses of α-PPP produce variable and less robust levels of self-administration. These results indicate that higher doses of α-PPP have reinforcing effects under conditions of extended access, suggesting the potential for abuse and a need for consideration in drug control policies.

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.

Amphetamine and the Smart Drug 3,4-Methylenedioxypyrovalerone (MDPV) Induce Generalization of Fear Memory in Rats

Human studies have consistently shown that drugs of abuse affect memory function. The psychostimulants amphetamine and the "bath salt" 3,4-methylenedioxypyrovalerone (MDPV) increase brain monoamine levels through a similar, yet not identical, mechanism of action. Findings indicate that amphetamine enhances the consolidation of memory for emotional experiences, but still MDPV effects on memory function are underinvestigated. Here, we tested the effects induced by these two drugs on generalization of fear memory and their relative neurobiological underpinnings. To this aim, we used a modified version of the classical inhibitory avoidance task, termed inhibitory avoidance discrimination task. According to such procedure, adult male Sprague-Dawley rats were first exposed to one inhibitory avoidance apparatus and, with a 1-min delay, to a second apparatus where they received an inescapable footshock. Forty-eight hours later, retention latencies were tested, in a randomized order, in the two training apparatuses as well as in a novel contextually modified apparatus to assess both strength and generalization of memory. Our results indicated that both amphetamine and MDPV induced generalization of fear memory, whereas only amphetamine enhanced memory strength. Co-administration of the β-adrenoceptor antagonist propranolol prevented the effects of both amphetamine and MDPV on the strength and generalization of memory. The dopaminergic receptor blocker cis-flupenthixol selectively reversed the amphetamine effect on memory generalization. These findings indicate that amphetamine and MDPV induce generalization of fear memory through different modulations of noradrenergic and dopaminergic neurotransmission.

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.

Simultaneous determination of N-ethylpentylone, dopamine, 5-hydroxytryptamine and their metabolites in rat brain microdialysis by liquid chromatography tandem mass spectrometry

N-Ethylpentylone (NEP) is a popular synthetic cathinone abused worldwide. To obtain more information about its pharmacokinetics and pharmacodynamics, a rapid, simple and sensitive liquid chromatography-tandem mass spectrometry method was developed for the determination of NEP, two important neurotransmitters, dopamine and serotonin, and their metabolites, including 3,4-dihydroxyphenylacetic acid, 3-methoxytyramine and 5-hydroxyindole-3-acetic acid, in rat brain microdialysate. The analytes were separated on a Phnomenex Polar C₁₈ column, with a mobile phase of 0.1% formic acid in water (A) and 0.1% formic acid in acetonitrile (B) under gradient elution to shorten the total chromatographic run time. A triple quadruple mass spectrometer coupled with an electrospray ionization source in both positive and negative ion mode was used to detect the analytes. This method showed excellent accuracy (87.4-113.5%) and precision (relative standard deviation <15%) at three quality control levels. The limits of detection were 0.2 ng/mL for NEP and 0.2-50 nm for the others and good linearity was obtained. This study pioneered a method to integrate exogenous drugs and endogenous neurotransmitters as the drugs act on the same determination system, which means that this innovation can provide support for further study of the addictive effects of NEP or other synthetic cathinones on extracellular levels of dopamine and 5-hydroxytryptamine.

Metabolites of the ring-substituted stimulants MDMA, methylone and MDPV differentially affect human monoaminergic systems

BACKGROUND

Amphetamine analogs with a 3,4-methylenedioxy ring-substitution are among the most popular illicit drugs of abuse, exerting stimulant and entactogenic effects. Enzymatic N-demethylation or opening of the 3,4-methylenedioxy ring via O-demethylenation gives rise to metabolites that may be pharmacologically active. Indeed, previous studies in rats show that specific metabolites of 3,4-methylenedioxymethamphetamine (MDMA), 3,4-methylenedioxymethcathinone (methylone) and 3,4-methylenedioxypyrovalerone (MDPV) can interact with monoaminergic systems.

AIM

Interactions of metabolites of MDMA, methylone and MDPV with human monoaminergic systems were assessed.

METHODS

The ability of parent drugs and their metabolites to inhibit uptake of tritiated norepinephrine, dopamine and serotonin (5-HT) was assessed in human embryonic kidney 293 cells transfected with human monoamine transporters. Binding affinities and functional activity at monoamine transporters and various receptor subtypes were also determined.

RESULTS

MDMA and methylone displayed greater potency to inhibit norepinephrine uptake as compared to their effects on dopamine and 5-HT uptake. N-demethylation of MDMA failed to alter uptake inhibition profiles, whereas N-demethylation of methylone decreased overall transporter inhibition potencies. O-demethylenation of MDMA, methylone and MDPV resulted in catechol metabolites that maintained norepinephrine and dopamine uptake inhibition potencies, but markedly reduced activity at 5-HT uptake. O-methylation of the catechol metabolites significantly decreased norepinephrine uptake inhibition, resulting in metabolites lacking significant stimulant properties.

CONCLUSIONS

Several metabolites of MDMA, methylone and MDPV interact with human transporters and receptors at pharmacologically relevant concentrations. In particular, N-demethylated metabolites of MDMA and methylone circulate in unconjugated form and could contribute to the in vivo activity of the parent compounds in human users.

Acute and repeated administration of MDPV increases aggressive behavior in mice: forensic implications

MDPV is a synthetic cathinone illegally marketed and consumed for its psychostimulant effects, which are similar to those produced by cocaine, amphetamines, and MDMA. Clinical reports indicate that MDPV produces euphoria, increases alertness, and at high doses causes agitation, psychosis, tachycardia and hypertension, hallucinations, delirium, hyperthermia, rhabdomyolysis, and even death. In rodents, MDPV reproduces the typical physiological effects of psychostimulant drugs, demonstrating greater potency than cocaine. Nevertheless, its role in aggressive behavior has been reported but not yet experimentally confirmed. Therefore, the aim of this study was to evaluate the effects of acute and repeated MDPV (0.01-10 mg/kg i.p.) administration on aggressive behavior in mice and to compare them with those of cocaine (0.01-10 mg/kg i.p.) administration. To this purpose, the resident-intruder test in isolated mice and the spontaneous and stimulated aggressiveness tests for group-housed mice were employed. The present study shows for the first time that MDPV enhances aggressive behavior and locomotion in mice with greater potency and efficacy than cocaine treatment. Moreover, the aggressive and locomotor responses are enhanced after repeated administration, indicating that a sensitization mechanism comes into play. These results, although from preclinical investigation, are suggestive that human MDPV intake could be a problem for public health and the criminal justice system. Thus, investigation by police officers and medical staff is needed to prevent interpersonal violence induced by the consumption of synthetic cathinones.

Hallucinogen-Like Action of the Novel Designer Drug 25I-NBOMe and Its Effect on Cortical Neurotransmitters in Rats

NBOMes are N-benzylmethoxy derivatives of the 2C family hallucinogens. 4-Iodo-2,5-dimethoxy-N-(2-methoxybenzyl)phenethylamine (25I-NBOMe) is one of the commonly used illicit drugs. It exhibits high binding affinity for 5-HT_2A/C and 5-HT_1A serotonin receptors. Activation of 5-HT_2A receptor induces head-twitch response (HTR) in rodents, a behavioral marker of hallucinogen effect in humans. There is not much data on neurochemical properties of NBOMes. Therefore, we aimed to investigate the effect of 25I-NBOMe on extracellular level of dopamine (DA), serotonin (5-HT), and glutamate (GLU) in the rat frontal cortex, tissue contents of monoamines, and hallucinogenic activity in rats. The extracellular levels of DA, 5-HT, and GLU were studied using microdialysis in freely moving animals. The tissue contents of DA, 5-HT and their metabolites 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA) were determined in the rat frontal cortex. We also tested a drug-elicited HTR. 25I-NBOMe at doses 1, 3, and 10 mg/kg (sc) increased extracellular DA, 5-HT, and GLU levels, enhanced tissue content of 5-HT and 5-HIAA, but did not affect tissue level of DA and its metabolites. The compound exhibited an inverted U-shaped dose-response curve with respect to the effect on extracellular DA and 5-HT levels, but a U-shaped dose-response curve was observed for its effect on GLU release and HTR. The data from our study suggest that hallucinogenic activity of 25I-NBOMe seems to be related with the increase in extracellular GLU level-mediated via cortical 5-HT_2A receptors. The influence of 25I-NBOMe on 5-HT_2C and 5-HT_1A receptors may modulate its effect on neurotransmitters and HTR.

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.

Analytical quantification, intoxication case series, and pharmacological mechanism of action for N-ethylnorpentylone (N-ethylpentylone or ephylone)

Synthetic cathinones continue to proliferate in clandestine drug markets worldwide. N-ethylnorpentylone (also known as N-ethylpentylone or ephylone) is a popular emergent cathinone, yet little information is available about its toxicology and pharmacology. Here we characterize the analytical quantification, clinical presentation, and pharmacological mechanism of action for N-ethylnorpentylone. Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was used to quantify N-ethylnorpentylone in blood obtained from human cases. Clinical features exhibited by the intoxicated individuals are described. The activity of N-ethylnorpentylone at plasma membrane transporters for dopamine (DAT), norepinephrine (NET) and 5-HT (SERT) was assessed using in vitro assays measuring uptake inhibition and evoked release of [3 H] neurotransmitters in rat brain synaptosomes. Our LC-MS/MS method assayed N-ethylnorpentylone concentrations with limits of detection and quantification of 1 and 5 ng/mL, respectively. Quantitation was linear from 5 to 500 ng/mL, and the method displayed specificity and reproducibility. Circulating concentrations of N-ethylnorpentylone ranged from 7 to 170 ng/mL in clinical cases, and the associated symptoms included palpitations, tachycardia, agitation, hallucinations, coma and death. N-Ethylnorpentylone was a potent inhibitor at DAT (IC50  = 37 nM), NET (IC50  = 105 nM) and SERT (IC50  = 383 nM) but displayed no transporter releasing activity. We present a validated method for quantifying N-ethylnorpentylone in human case work. The drug is a psychomotor stimulant capable of inducing serious cardiovascular and neurological side-effects which can be fatal. In vitro findings indicate that N-ethylnorpentylone exerts its effects by potent blockade of DAT and NET, thereby elevating extracellular levels of dopamine and norepinephrine in the brain and periphery.

A review of the influence of functional group modifications to the core scaffold of synthetic cathinones on drug pharmacokinetics

RATIONALE

The synthetic cathinones are a class of designer drugs of abuse that share a common core scaffold. The pharmacokinetic profiles of the synthetic cathinones vary based on the substitutions to the core scaffold.

OBJECTIVES

To provide a summary of the literature regarding the pharmacokinetic characteristics of the synthetic cathinones, with a focus on the impact of the structural modifications to the pharmacokinetics.

RESULTS

In many, but not all, instances the pharmacokinetic characteristics of the synthetic cathinones can be reasonably predicted based on the substitutions to the core scaffold. Mephedrone and methylone are chemically alike and have similar T_max and t_1/2 in male rats. MDPV, a structurally distinct synthetic cathinone from mephedrone and methylone, has a lower T_max and t_1/2. Increasing the length of the alkyl chain on the α position of methylone, to produce pentylone, results in increased plasma concentrations and longer t_1/2. Metabolism of the synthetic cathinones is reasonably predictable based on the chemical structure, and several phase I metabolites retain pharmacodynamic activity. CYP2D6 is implicated in the metabolism of all of the synthetic cathinones, and other P450s (CYP1A2, CYP2B6, and CYP2C19) are known to contribute variably to the metabolism of specific synthetic cathinones.

CONCLUSIONS

Continued research will lead to a better understanding of the pharmacokinetic changes associated with structural modifications to the cathinone scaffold, and potentially in the long range, enhanced overdose and addiction therapy. Additionally, the areas of polydrug use and pharmacogenetics have been largely overlooked with regard to synthetic cathinones.

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.

Cardiovascular effects of 3,4-methylenedioxypyrovalerone (MDPV) in male and female Sprague-Dawley rats

BACKGROUND

3,4-methylenedioxypyrovalerone (MDPV) toxicity includes intense neurological and cardiovascular events. We examined MDPV-induced cardiovascular, temperature, and locomotor effects following escalating and repeated MDPV administration in adult male and female Sprague-Dawley rats and compared these effects to cocaine in male rats.

METHODS

Telemetry devices were surgically implanted to allow continuous measurement of cardiovascular, temperature, and locomotor activity over a 22 h period after dosing. Rats were administered increasing intraperitoneal (IP) MDPV doses (1-5.6 mg/kg) every other day, followed two days later by a binge regimen of four injections of 3 mg/kg MDPV at 2 h intervals. MDPV serum concentrations were measured by LC-MS/MS. Cocaine (3-30 mg/kg) and four injections of 30 mg/kg IP were administered to male rats for comparison with male MDPV data.

RESULTS

The duration of MDPV cardiovascular effects was significantly greater (p < 0.05) in male rats than female rats at 3-5.6 mg/kg. The ED₅₀ for MDPV-induced locomotor was significantly lower in males (2.4 ± 0.3) than females (3.4 ± 0.2). Males showed significantly greater variability in MDPV serum concentrations than females after binge dosing. MDPV produced five-fold more potent cardiovascular effects than cocaine in male rats. MDPV did not alter thermoregulation in either sex, but cocaine binge administration decreased temperature.

CONCLUSION

Effects of MDPV on temperature were not significantly different between sexes. MDPV-induced cardiovascular and locomotor effects in males lasted significantly longer and were more potent than in females. These differences appeared to be related to pharmacokinetic factors leading to greater variance in MDPV serum concentrations in males.

Neuroadaptive changes and behavioral effects after a sensitization regime of MDPV

3,4-methylenedioxypyrovalerone (MDPV) is a synthetic cathinone with cocaine-like properties. In a previous work, we exposed adolescent mice to MDPV, finding sensitization to cocaine effects, and a higher vulnerability to cocaine abuse in adulthood. Here we sought to determine if such MDPV schedule induces additional behavioral-neuronal changes that could explain such results. After MDPV treatment (1.5 mg kg^-1, twice daily, 7 days), mice were behaviorally tested. Also, we investigated protein changes in various brain regions. MDPV induced aggressiveness and anxiety, but also contributed to a faster habituation to the open field. This feature co-occurred with an induction of ΔFosB in the orbitofrontal cortex that was higher than its expression in the ventral striatum. Early after treatment, D2R:D1R ratio pointed to a preponderance of D1R but, upon withdrawal, the ratio recovered. Increased expression of Arc, CDK5 and TH, and decrease in DAT protein levels persisted longer after withdrawal, pointing to a neuroplastic lasting effect similar to that involved in cocaine addiction. The implication of the hyperdopaminergic condition in the MDPV-induced aggressiveness cannot be ruled out. We also found an initial oxidative effect of MDPV, without glial activation. Moreover, although initially the dopaminergic signal induced by MDPV resulted in increased ΔFosB, we did not observe any change in NFκB or GluA2 expression. Finally, the changes observed after MDPV treatment could not be explained according to the autoregulatory loop between ΔFosB and the epigenetic repressor G9a described for cocaine. This provides new knowledge about the neuroadaptive changes involved in the vulnerability to psychostimulant addiction.

Sales and Advertising Channels of New Psychoactive Substances (NPS): Internet, Social Networks, and Smartphone Apps

In the last decade, the trend of drug consumption has completely changed, and several new psychoactive substances (NPS) have appeared on the drug market as legal alternatives to common drugs of abuse. Designed to reproduce the effects of illegal substances like cannabis, ecstasy, cocaine, or ketamine, NPS are only in part controlled by UN conventions and represent an emerging threat to global public health. The effects of NPS greatly differ from drug to drug and relatively scarce information is available at present about their pharmacology and potential toxic effects. Yet, compared to more traditional drugs, more dangerous short- and long-term effects have been associated with their use, and hospitalizations and fatal intoxications have also been reported after NPS use. In the era of cyberculture, the Internet acts as an ideal platform to promote and market these compounds, leading to a global phenomenon. Hidden by several aliases, these substances are sold across the web, and information about consumption is shared by online communities through drug fora, YouTube channels, social networks, and smartphone applications (apps). This review intends to provide an overview and analysis of social media that contribute to the popularity of NPS especially among young people. The possibility of using the same channels responsible for their growing diffusion to make users aware of the risks associated with NPS use is proposed.