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

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.'

MDPV and α-PVP use in humans: The twisted sisters

The new psychoactive substances phenomenon continues to represent a considerable public health challenge. Synthetic cathinones are β-keto amphetamine analogues, also known as legal highs, research chemicals, bath salts. These drugs have surfaced as a popular alternative to other illicit drugs of abuse, such as cocaine, MDMA, and methamphetamine, due to their potent psychostimulant and empathogenic effects. Pyrovalerone cathinones (a-pyrrolidinophenones) form a distinct group of designer cathinones, such as MDPV. After being listed as an illegal product, "second generation" compounds such as α-PVP, sharing a very similar chemical structure with MDPV, were developed. Clinical effects of these compounds are individual, dose- and route of administration-dependent. Both of them have been involved in an increased number of, not only acute intoxications but also fatalities over the past few years, raising concerns in the medical field. In this paper, we will review the available data regarding the use and effects of MDPV and α-PVP in humans in order to highlight their impact on public health. Health actors and general population need to be clearly informed of potential risks and consequences of these 2 novel psychoactive substances spread and use. The literature search conducted led to the identification of potentially 83 relevant articles. All articles were screened from their abstracts to determine their relevance in the framework of the current review. This article is part of the Special Issue entitled 'Designer Drugs and Legal Highs.'

The Cathinones MDPV and α-PVP Elicit Different Behavioral and Molecular Effects Following Acute Exposure

Since the mid-to-late 2000s, synthetic cathinones have gained popularity among drug users due to their psychostimulant effects greater than those produced by cocaine and amphetamine. Among them, 3,4-methylenedioxypyrovalerone (MDPV) and 1-phenyl-2-(pyrrolidin-1-yl)pentan-1-one (α-PVP) are ones of the most popular cathinones available in the clandestine market as "bath salts" or "fertilizers." Pre-clinical studies indicate that MDPV and α-PVP induced psychomotor stimulation, affected thermoregulation, and promoted reinforcing properties in rodents. However, a direct comparative analysis on the effects caused by MDPV and α-PVP on the behavior and neuronal activation in rodents is still lacking. Behavioral analyses revealed that both MDPV and α-PVP affect spontaneous and stimulated motor responses. In particular, MDPV showed a greater psychomotor effect than α-PVP in line with its higher potency in blocking the dopamine transporter (DAT). Notably, MDPV was found to be more effective than α-PVP in facilitating spontaneous locomotion and it displayed a biphasic effect in contrast to the monophasically stimulated locomotion induced by α-PVP. In addition to the behavioral results, we also found a different modulation of immediate early genes (IEGs) such as Arc/Arg3.1 and c-Fos in the frontal lobe, striatum, and hippocampus, indicating that these drugs do impact brain homeostasis with changes in neuronal activity that depend on the drug, the brain area analyzed, and the timing after the injection. These results provide the first discrimination between MDPV and α-PVP based on behavioral and molecular data that may contribute to explain, at least in part, their toxicity.

Conditioned taste avoidance, conditioned place preference and hyperthermia induced by the second generation 'bath salt' α-pyrrolidinopentiophenone (α-PVP)

BACKGROUND

α-Pyrrolidinopentiophenone (α-PVP) has been reported to be rewarding in a variety of pre-clinical models. Given that a number of drugs of abuse have both rewarding and aversive effects, the balance of which influences addiction potential, the present study examined the aversive properties of α-PVP by assessing its ability to induce taste avoidance. This assessment was made in a combined taste avoidance/place conditioning design that also allowed an evaluation of the relationship between α-PVP's aversive and rewarding effects.

METHODS

Male Sprague-Dawley rats were exposed to a novel saccharin solution, injected with one of four doses of α-PVP (0, 0.3, 1.0 and 3.0mg/kg) (IP) and placed on one side of a place conditioning apparatus. The next day, they were injected with vehicle, given access to water and placed on the other side. Following four conditioning cycles, saccharin avoidance and place preferences were then assessed. The effects of α-PVP on body temperature were also examined.

RESULTS

α-PVP induced dose-dependent taste avoidance as well as significant increases in time spent on the drug-paired side (although this effect was not dependent on dose). α-PVP also induced dose- and time-dependent hyperthermia.

CONCLUSIONS

α-PVP induced significant taste avoidance whose strength relative to the psychostimulants methylenedioxypyrovalerone (MDPV) and cocaine paralleled their relative binding to the dopamine transporter. Similar to other drugs of abuse, α-PVP has both aversive and rewarding effects. It will be important to assess how various experiential and subject variables impact these effects and their balance to predict abuse liability.

Synthetic Cathinones: A Brief Overview of Overviews with Applications to the Forensic Sciences

Catha edulis, the fresh leaves of which (i.e., khat) are used for their central stimulant actions, has been known for many hundreds of years. S(-)Cathinone was identified as a centrally-active khat constituents >30 years ago. Although khat use was a problem long localized to certain Middle Eastern and certain Eastern African nations, 'synthetic cathinones' (synthetic analogs of cathinone) represent a "new" class of abused substances with growing worldwide appeal. To date, about 150 synthetic cathinones have been identified on the clandestine market, and only a dozen or so have been controlled (U.S. Schedule I). Because these agents do not represent a pharmacologically (i.e., behavioral) or mechanistically homogeneous class of agents, synthetic cathinones are being investigated one agent at a time to understand their actions, mechanisms of action, metabolism, toxicity, and abuse potential - the latter to identify possible modes of overdose treatment and for Scheduling purposes. The available agents might represent only the 'tip of the iceberg'; the potential for many more new synthetic cathinones is very real. Investigation of these agents on an agent-by-agent basis is a daunting task. Attempts are being made to understand these agents as a class, by examination of their structure-activity relationships. Here, we provide an overview of review articles that attempts to shed light on these agents as a class, rather than on an agent-by-agent basis. This article is meant to be a reference resource that might expedite the work of those in this field by directing them to where they can find useful information.

The 2014 Philip S. Portoghese Medicinal Chemistry Lectureship: The "Phenylalkylaminome" with a Focus on Selected Drugs of Abuse

The phenylalkylamine, particularly the phenylethylamine, moiety is a common structural feature found embedded in many clinically approved agents. Greater still is its occurrence in drugs of abuse. The simplest phenylethylamine, 2-phenylethylamine itself, is without significant central action when administered at moderate doses, but fairly simple structural modifications profoundly impact its pharmacology and result in large numbers of useful pharmacological tools, agents with therapeutic potential, and in drugs of abuse (e.g., hallucinogens, central stimulants, empathogens), the latter of which are the primary focus here. In vivo drug discrimination techniques and in vitro receptor/transporter methods have been applied to understand the actions of these phenylalkylamines and their mechanisms of action. Thus far, depending upon pendent substituents, certain receptors (e.g., serotonin receptors) and monoamine transporters (i.e., serotonin, dopamine, and norepinephrine transporters) have been implicated as playing major roles in the actions of these abused agents in a complex and, at times, interwoven manner.

Behavioral evidence for the abuse potential of the novel synthetic cathinone alpha-pyrrolidinopentiothiophenone (PVT) in rodents

RATIONALE

Synthetic cathinones are chemical derivatives of cathinone that are pharmacologically similar to cocaine and methamphetamine. Recently, abuse of synthetic cathinones among young people has increased.

OBJECTIVES

The present study aimed to characterize the behavioral effects of alpha-pyrrolidinopentiothiophenone (PVT), an analog of alpha-pyrrolidinovalerophenone and second-generation synthetic cathinone, as well as to evaluate its abuse potential, using conditioned place preference, intravenous self-administration (SA), and drug discrimination paradigms in rodent models.

RESULTS

Alpha-PVT produced a significant place preference in mice at doses of 10, 30, and 50 mg/kg. In the SA experiment, alpha-PVT (0.1, 0.3, and 1.0 mg/kg/infusion) produced an inverted U-shaped dose-effect curve in rats. Under a progressive ratio schedule of reinforcement, there appeared to be a positive relationship between alpha-PVT dose and the breakpoints for alpha-PVT reinforcement. Additionally, alpha-PVT fully substituted for the discriminative stimulus effects of both cocaine and methamphetamine in rats.

CONCLUSIONS

Our results indicate that alpha-PVT has rewarding and reinforcing effects and shares the interoceptive effects of cocaine and methamphetamine. To the best of our knowledge, the present study is the first to show that alpha-PVT has reinforcing properties when delivered on its own, which suggests possible abuse liability in humans.

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

3,4-Methylenedioxypyrovalerone (MDPV) is a psychoactive component of so-called bath salts products that has caused serious medical consequences in humans. In this chapter, we review the neuropharmacology of MDPV and related analogs, and supplement the discussion with new results from our preclinical experiments. MDPV acts as a potent uptake inhibitor at plasma membrane transporters for dopamine (DAT) and norepinephrine (NET) in nervous tissue. The MDPV formulation in bath salts is a racemic mixture, and the S isomer is much more potent than the R isomer at blocking DAT and producing abuse-related effects. Elevations in brain extracellular dopamine produced by MDPV are likely to underlie its locomotor stimulant and addictive properties. MDPV displays rapid pharmacokinetics when injected into rats (0.5-2.0 mg/kg), with peak plasma concentrations achieved by 10-20 min and declining quickly thereafter. MDPV is metabolized to 3,4-dihydroxypyrovalerone (3,4-catechol-PV) and 4-hydroxy-3-methoxypyrovalerone (4-OH-3-MeO-PV) in vivo, but motor activation produced by the drug is positively correlated with plasma concentrations of parent drug and not its metabolites. 3,4-Catechol-PV is a potent uptake blocker at DAT in vitro but has little activity after administration in vivo. 4-OH-3-MeO-PV is the main MDPV metabolite but is weak at DAT and NET. MDPV analogs, such as α-pyrrolidinovalerophenone (α-PVP), display similar ability to inhibit DAT and increase extracellular dopamine concentrations. Taken together, these findings demonstrate that MDPV and its analogs represent a unique class of transporter inhibitors with a high propensity for abuse and addiction.

Effects of 3,4-methylenedioxypyrovalerone (MDPV) pre-exposure on the aversive effects of MDPV, cocaine and lithium chloride: Implications for abuse vulnerability

BACKGROUND

Drug use is thought to be a balance of the rewarding and aversive effects of drugs. Understanding how various factors impact these properties and their relative balance may provide insight into their abuse potential. In this context, the present study attempted to evaluate the effects of drug history on the aversive effects of 3,4-methylenedioxypyrovalerone (MDPV), one of a variety of synthetic cathinones (collectively known as "bath salts").

METHODS

Different groups of male Sprague-Dawley rats were exposed to either vehicle or MDPV (1.8mg/kg) once every fourth day for five total injections prior to taste avoidance conditioning in which a novel saccharin solution was repeatedly paired with either vehicle, MDPV (1.8mg/kg), the related psychostimulant cocaine (18mg/kg) or the emetic lithium chloride (LiCl) (13.65mg/kg).

RESULTS

In animals pre-exposed to vehicle, all three drugs induced significant and comparable taste avoidance relative to animals injected with vehicle during conditioning. MDPV pre-exposure attenuated the avoidance induced by both MDPV and cocaine (greater attenuation for MDPV than cocaine), but had no effect on that induced by LiCl.

CONCLUSIONS

These findings suggest that a history of MDPV use may reduce or attenuate MDPV and cocaine's (but not LiCl's) aversive effects. The implications for such changes in MDPV's aversive effects to its potential use and abuse were discussed.

New psychoactive substances: an overview on recent publications on their toxicodynamics and toxicokinetics

This review article covers English-written and PubMed-listed review articles and original studies published between January 2015 and April 2016 dealing with the toxicodynamics and toxicokinetics of new psychoactive substances. Compounds covered include stimulants and entactogens, synthetic cannabinoids, tryptamines, NBOMes, phencyclidine-like drugs, benzodiazepines, and opioids. First, an overview and discussion is provided on timely review articles followed by an overview and discussion on recent original studies. Both sections are then concluded by an opinion on these latest developments. This review shows that the NPS market is still highly dynamic and that the data published on their toxicodynamics and toxicokinetics can hardly keep pace with the appearance of new entities. However, data available are very helpful to understand and predict how NPS may behave in severe intoxication. The currently best-documented parameter is the in vitro metabolism of NPS, a prerequisite to allow detection of NPS in biological matrices in cases of acute intoxications or chronic consumption. However, additional data such as their chronic toxicity are still lacking.