Desoxypipradrol is more potent than cocaine on evoked dopamine efflux in the nucleus accumbens

Toxicological Analysis of Cases of Mixed Poisonings with Synthetic Cathinones and Other Drugs of Abuse

Some of the most commonly used new psychoactive substances (NPSs) are synthetic cathinones (SCs). The literature increasingly indicates that SCs have a significant addictive potential and pose a high risk to human health and life. The vast majority of SC users take a number of substances simultaneously. This article lists the detected concentrations in 26 fatal and 2 non-fatal real cases, in which SCs or an SC along with other substances were determined in blood and other biological materials. The following SCs were found most often: α-pyrrolidinohexiophenone, α-pyrrolidinopentiophenone, N-ethylpentedrone (NEP), 4-methyl-α-ethylaminopentiophenone and N-ethylhexedrone. In addition to detected SCs, the analyzed samples showed the presence of conventional drugs such as methamphetamine, 3,4-methylenedioxymethamphetamine, 3,4-methylenedioxyamphetamine, amphetamine and NPSs from groups other than SCs, such as synthetic cannabinoids (UR-144 and 5F-AMB), synthetic opioids (AH-7921, U-47700 and 4-fluorobutyrfentanyl) and others (desoxypipradrol and etizolam). The quantitative analyses were carried out by liquid chromatography with tandem mass spectrometry (LC-MS-MS). This study presents pioneering data on concentrations and effects of 4-ethylmethcathinone, NEP, N-ethylbuphedrone and mexedrone. Also noteworthy are the data on SCs that until now have rarely been described in the literature together with specified blood concentrations. The analyzed cases of taking SCs were associated with fatal intoxication (n = 26), driving under the influence of drugs (n = 2) and death caused by beating (n = 1). Taking SCs has serious side effects that can lead to multiple organ failure and death. The use of more than one psychoactive substance simultaneously (including at least one SC) contributes to increased SC toxicity. These data could be valuable for further interpretation of other results from toxicological analyses.

Molecular mechanisms of action of stimulant novel psychoactive substances that target the high-affinity transporter for dopamine

Drug misuse is a significant social and public health problem worldwide. Misused substances exert their neurobehavioural effects through changing neural signalling within the brain, many of them leading to substance dependence and addiction in the longer term. Among drugs with addictive liability, there are illicit classical stimulants such as cocaine and amphetamine, and their more recently available counterparts known as novel psychoactive substances (NPS). Stimulants normally increase dopamine availability in the brain, including the pathway implicated in reward-related behaviour. This pattern is observed in both animal and human brain. The main biological target of stimulants, both classical and NPS, is the dopamine transporter (DAT) implicated in the dopamine-enhancing effects of these drugs. This article aims at reviewing research on the molecular mechanisms underpinning the interactions between stimulant NPS, such as benzofurans, cathinones or piperidine derivatives and DAT, to achieve a greater understanding of the core phenomena that decide about the addictive potential of stimulant NPS. As the methodology is essential in the process of experimental research in this area, we review the applications of in vitro, in vivo and in silico approaches. The latter, including molecular dynamics, attracts the focus of the present review as the method of choice in molecular and atomistic investigations of the mechanisms of addiction of stimulant NPS. Research of this kind is of interest to not only scientists but also health professionals as updated knowledge of NPS, their modes of action and health risks, is needed to tackle the challenges posed by NPS misuse.

The Role of Dopamine in the Stimulant Characteristics of Novel Psychoactive Substances (NPS)-Neurobiological and Computational Assessment Using the Case of Desoxypipradrol (2-DPMP)

Stimulant drugs, including novel psychoactive substances (NPS, formerly “legal highs”) have addictive potential which their users may not realize. Stimulants increase extracellular dopamine levels in the brain, including the reward and addiction pathways, through interacting with dopamine transporter (DAT). This work aimed to assess the molecular and atomistic mechanisms of stimulant NPS actions at DAT, which translate into biological outcomes such as dopamine release in the brain’s reward pathway. We applied combined in vitro, in vivo, and in silico methods and selected 2-diphenylmethylpiperidine (2-DPMP) as an example of stimulant NPS for this study. We measured in vitro binding of 2-DPMP to rat striatum and accumbens DAT by means of quantitative autoradiography with a selective DAT-radioligand [¹²⁵I]RTI-121. We evaluated the effects of intravenously administered 2-DPMP on extracellular dopamine in the accumbens-shell and striatum using in vivo microdialysis in freely moving rats. We used dynamic modeling to investigate the interactions of 2-DPMP within DAT, in comparison with cocaine and amphetamine. 2-DPMP potently displaced the radioligand in the accumbens and striatum showing dose-dependence from 0.3 to 30 μM. IC₅₀ values were: 5.65 × 10^-7M for accumbens shell and 6.21 × 10^-7M for dorsal striatum. Dose-dependent responses were also observed in accumbens-shell and striatum in vivo, with significant increases in extracellular dopamine levels. Molecular dynamics simulations identified contrasting conformational changes of DAT for inhibitors (cocaine) and releasers (amphetamine). 2-DPMP led to molecular rearrangements toward an outward-facing DAT conformation that suggested a cocaine-type effect. The present combination of molecular modeling with experimental neurobiological procedures allows for extensive characterization of the mechanisms of drug actions at DAT as the main molecular target of stimulants, and provides an insight into the role of dopamine in the molecular and neurobiological mechanisms of brain responses to stimulant NPS that have addictive potential. Such knowledge reveals the risk of addiction related to NPS use. The research presented here can be adapted for other psychostimulants that act at their membrane protein targets.

Mechanistic Insights into the Stimulant Properties of Novel Psychoactive Substances (NPS) and Their Discrimination by the Dopamine Transporter-In Silico and In Vitro Exploration of Dissociative Diarylethylamines

Novel psychoactive substances (NPS) may have unsuspected addiction potential through possessing stimulant properties. Stimulants normally act at the dopamine transporter (DAT) and thus increase dopamine (DA) availability in the brain, including nucleus accumbens, within the reward and addiction pathway. This paper aims to assess DAT responses to dissociative diarylethylamine NPS by means of in vitro and in silico approaches. We compared diphenidine (DPH) and 2-methoxydiphenidine (methoxphenidine, 2-MXP/MXP) for their binding to rat DAT, using autoradiography assessment of [¹²⁵I]RTI-121 displacement in rat striatal sections. The drugs' effects on electrically-evoked DA efflux were measured by means of fast cyclic voltammetry in rat accumbens slices. Computational modeling, molecular dynamics and alchemical free energy simulations were used to analyse the atomistic changes within DAT in response to each of the five dissociatives: DPH, 2-MXP, 3-MXP, 4-MXP and 2-Cl-DPH, and to calculate their relative binding free energy. DPH increased DA efflux as a result of its binding to DAT, whereas MXP had no significant effect on either DAT binding or evoked DA efflux. Our computational findings corroborate the above and explain the conformational responses and atomistic processes within DAT during its interactions with the dissociative NPS. We suggest DPH can have addictive liability, unlike MXP, despite the chemical similarities of these two NPS.

In Vitro Neurochemical Assessment of Methylphenidate and Its "Legal High" Analogs 3,4-CTMP and Ethylphenidate in Rat Nucleus Accumbens and Bed Nucleus of the Stria Terminalis

3,4-dichloromethylphenidate (3,4-CTMP) and ethylphenidate are new psychoactive substances and analogs of the attention deficit medication methylphenidate. Both drugs have been reported on online user fora to induce effects similar to cocaine. In the UK, 3,4-CTMP appeared on the drug market in 2013 and ethylphenidate has been sold since 2010. We aimed to explore the neurochemical effects of these drugs on brain dopamine and noradrenaline efflux. 3,4-CTMP and ethylphenidate, purchased from online vendors, were analyzed using gas chromatography and mass spectroscopy to confirm their identity. Drugs were then tested in adolescent male rat brain slices of the nucleus accumbens and stria terminalis for effects on dopamine and noradrenaline efflux respectively. Fast cyclic voltammetry was used to measure transmitter release. Methylphenidate (10 μM) increased evoked dopamine and noradrenaline efflux by 4- and 2-fold, respectively. 3,4-CTMP (0.1 and 1 μM) increased evoked dopamine and noradrenaline efflux by ~6-fold and 2-fold, respectively. Ethylphenidate (1 μM) doubled evoked dopamine and noradrenaline efflux in both cases. 3,4-CTMP's effect on dopamine efflux was greater than that of methylphenidate, but ethylphenidate appears to be a weaker dopamine transporter inhibitor. Experiments using the dopamine D₂ antagonist haloperidol, the noradrenaline α₂ receptor antagonist yohimbine, the dopamine transporter inhibitor GBR12909 and the noradrenaline transporter inhibitor desipramine confirmed that we were measuring dopamine in the accumbens and noradrenaline in the ventral BNST. All three psychostimulant drugs, through their effects on dopamine efflux, may have addictive liability although the effect of 3,4-CTMP on dopamine suggests that it might be most addictive and ethylphenidate least addictive.

Neuropharmacology of New Psychoactive Substances (NPS): Focus on the Rewarding and Reinforcing Properties of Cannabimimetics and Amphetamine-Like Stimulants

New psychoactive substances (NPS) are a heterogeneous and rapidly evolving class of molecules available on the global illicit drug market (e.g smart shops, internet, “dark net”) as a substitute for controlled substances. The use of NPS, mainly consumed along with other drugs of abuse and/or alcohol, has resulted in a significantly growing number of mortality and emergency admissions for overdoses, as reported by several poison centers from all over the world. The fact that the number of NPS have more than doubled over the last 10 years, is a critical challenge to governments, the scientific community, and civil society [EMCDDA (European Drug Report), 2014; UNODC, 2014b; Trends and developments]. The chemical structure (phenethylamines, piperazines, cathinones, tryptamines, synthetic cannabinoids) of NPS and their pharmacological and clinical effects (hallucinogenic, anesthetic, dissociative, depressant) help classify them into different categories. In the recent past, 50% of newly identified NPS have been classified as synthetic cannabinoids followed by new phenethylamines (17%) (UNODC, 2014b). Besides peripheral toxicological effects, many NPS seem to have addictive properties. Behavioral, neurochemical, and electrophysiological evidence can help in detecting them. This manuscript will review existing literature about the addictive and rewarding properties of the most popular NPS classes: cannabimimetics (JWH, HU, CP series) and amphetamine-like stimulants (amphetamine, methamphetamine, methcathinone, and MDMA analogs). Moreover, the review will include recent data from our lab which links JWH-018, a CB1 and CB2 agonist more potent than Δ⁹-THC, to other cannabinoids with known abuse potential, and to other classes of abused drugs that increase dopamine signaling in the Nucleus Accumbens (NAc) shell. Thus the neurochemical mechanisms that produce the rewarding properties of JWH-018, which most likely contributes to the greater incidence of dependence associated with “Spice” use, will be described (De Luca et al., 2015a). Considering the growing evidence of a widespread use of NPS, this review will be useful to understand the new trends in the field of drug reward and drug addiction by revealing the rewarding properties of NPS, and will be helpful to gather reliable data regarding the abuse potential of these compounds.

The potential utility of some legal highs in CNS disorders

Over the last decade there has been an explosion of new drugs of abuse, so called legal highs or novel psychoactive substances (NPS). Many of these abused drugs have unknown pharmacology, but their biological effects can be anticipated from their molecular structure and possibly also from online user reports. When considered with the findings that some prescription medications are increasingly abused and that some abused drugs have been tested clinically one could argue that there has been a blurring of the line between drugs of abuse and clinically used drugs. In this review we examine these legal highs/NPS and consider whether, based on their known or predicted pharmacology, some might have the potential to be clinically useful in CNS disorders.

Stimulant mechanisms of cathinones - effects of mephedrone and other cathinones on basal and electrically evoked dopamine efflux in rat accumbens brain slices

Mephedrone, an erstwhile "legal high", and some non-abused cathinones (ethcathinone, diethylpropion and bupropion) were tested for stimulant effects in vitro, through assessing their abilities to increase basal and electrically evoked dopamine efflux in rat accumbens brain slices, and compared with cocaine and amphetamine. We also tested mephedrone against cocaine in a dopamine transporter binding study. Dopamine efflux was electrically evoked and recorded using voltammetry in the rat accumbens core. We constructed concentration response curves for these cathinones for effects on basal dopamine levels; peak efflux after local electrical stimulation and the time-constant of the dopamine decay phase, an index of dopamine reuptake. We also examined competition between mephedrone or cocaine and [(125)I]RTI121 at the dopamine transporter. Mephedrone was less potent than cocaine at displacing [(125)I]RTI121. Mephedrone and amphetamine increased basal levels of dopamine in the absence of electrical stimulation. Cocaine, bupropion, diethylpropion and ethcathinone all increased the peak dopamine efflux after electrical stimulation and slowed dopamine reuptake. Cocaine was more potent than bupropion and ethcathinone, while diethylpropion was least potent. Notably, cocaine had the fastest onset of action. These data suggest that, with respect to dopamine efflux, mephedrone is more similar to amphetamine than cocaine. These findings also show that cocaine was more potent than bupropion and ethcathinone while diethylpropion was least potent. Mephedrone's binding to the dopamine transporter is consistent with stimulant effects but its potency was lower than that of cocaine. These findings confirm and further characterize stimulant properties of mephedrone and other cathinones in adolescent rat brain.

Fully diastereoselective synthesis of polysubstituted, functionalized piperidines and decahydroquinolines based on multicomponent reactions catalyzed by cerium(IV) ammonium nitrate

The cerium(IV) ammonium nitrate (CAN)-catalyzed, three-component reaction between primary amines, β-dicarbonyl compounds, and α,β-unsaturated aldehydes in ethanol heated to reflux, constitutes a general, one-pot synthesis of 1,4-dihydropyridines. Their reduction with sodium triacetoxyborohydride furnished piperidine derivatives bearing up to five substituents with full diastereoselectivity in a hitherto inaccessible stereochemical arrangement. The reaction proceeded with no significant loss of enantiomeric purity under mild reduction conditions that are compatible with several functional groups that are normally sensitive to reduction. Octahydroquinolin-5-one derivatives, which were prepared by a modified version of the initial multicomponent reaction, were not suitable substrates for the sodium triacetoxyborohydride mediated reduction, but they were transformed into the corresponding decahydroquinolines, including a precursor of the amphibian alkaloid pumiliotoxin C, by catalytic hydrogenation under a variety of conditions.

Pharmacological profiles of aminoindanes, piperazines, and pipradrol derivatives

Aminoindanes, piperazines, and pipradrol derivatives are novel psychoactive substances found in "Ecstasy" tablets as replacements for 3,4-methylenedioxymethamphetamine (MDMA) or substances sold as "ivory wave." The pharmacology of these MDMA- and methylphenidate-like substances is poorly known. We characterized the pharmacology of the aminoindanes 5,6-methylenedioxy-2-aminoindane (MDAI), 5-iodoaminoindane (5-IAI), and 2-aminoindane (2-AI), the piperazines meta-chlorophenylpiperazine (m-CPP), trifluoromethylphenylpiperazine (TFMPP), and 1-benzylpiperazine (BZP), and the pipradrol derivatives desoxypipradrol (2-diphenylmethylpiperidine [2-DPMP]), diphenylprolinol (diphenyl-2-pyrrolidinemethanol [D2PM]), and methylphenidate. We investigated norepinephrine (NE), dopamine (DA), and serotonin (5-hydroxytryptamine [5-HT]) uptake inhibition using human embryonic kidney 293 (HEK 293) cells that express the respective human monoamine transporters (NET, DAT, and SERT). We also evaluated the drug-induced efflux of NE, DA, and 5-HT from monoamine-preloaded cells and the binding affinity to monoamine transporters and receptors, including trace amine-associated receptor 1 (TAAR1). 5-IAI and MDAI preferentially inhibited the SERT and NET and released 5-HT. 2-AI interacted with the NET. BZP blocked the NET and released DA. m-CPP and TFMPP interacted with the SERT and serotonergic receptors. The pipradrol derivatives were potent and selective catecholamine transporter blockers without substrate releasing properties. BZP, D2PM, and 2-DPMP lacked serotonergic activity and TAAR1 binding, in contrast to the aminoindanes and phenylpiperazines. In summary, all of the substances were monoamine transporter inhibitors, but marked differences were found in their DAT vs. SERT inhibition profiles, release properties, and receptor interactions. The pharmacological profiles of D2PM and 2-DPMP likely predict a high abuse liability.

Designer psychostimulants: pharmacology and differences

More than 200 novel psychoactive drugs have been reported in Europe, with 73 added in 2012 and additional compounds encountered every week in 2013. Many of these are "designer psychostimulants" which aim to mimic the subjective effects of amphetamines, cocaine or 3,4-methylenedioxymethylamphetamine (MDMA; "Ecstasy"). Several drugs are based on the beta-ketoamphetamine cathinone chemical structure, others include aminoindanes, aminotetralins, piperazines, amphetamine analogues and pipradrol derivatives. Although a detailed analysis of the pharmacology of these novel drugs is largely lacking, a number of scientific studies have been reported in 2011-2013 and these are reviewed. All of the novel psychostimulants activate monoamine systems in the brain - with differing dopamine (DA) v serotonin (5-HT) preferences. Those activating principally DA systems are amphetamine-like stimulants, such as naphyrone, desoxypipradrol, 3,4-methylenedioxypyrovalerone (MDPV), and benzylpiperazine while those preferentially activating 5-HT mechanisms are MDMA-like or cocaine-like stimulants, such as mephedrone, methylone and other substituted cathinones, aminoindanes, aminotetralins and piperazines. The ability of mephedrone and other novel psychostimulants to substitute for methylamphetamine or cocaine in drug discrimination tests in rats, and the ability of mephedrone to induce conditioned place preference and to sustain self-administration behaviour suggests that this and other cocaine/methylamphetamine-like drugs have dependence liability. This article is part of the Special Issue entitled 'CNS Stimulants'.

2-DPMP (desoxypipradrol, 2-benzhydrylpiperidine, 2-phenylmethylpiperidine) and D2PM (diphenyl-2-pyrrolidin-2-yl-methanol, diphenylprolinol): A preliminary review

2-DPMP (desoxypipradrol, 2-benzhydrylpiperidine, 2-phenylmethylpiperidine) and D2PM (diphenyl-2-pyrrolidin-2-yl-methanol, diphenylprolinol) are psychoactive substances, sold primarily over the Internet and in 'head' shops as 'legal highs', 'research chemicals' or 'plant food'. Originally developed in the 1950s for the treatment of narcolepsy and ADHD, 2-DPMP's use soon became very limited. Recreational use of 2-DPMP and D2PM appears to have started in March 2007, but only developed slowly. However, in the UK their popularity grew in 2009, increasing rapidly during summer 2010. At this time, there were many presentations to UK Emergency Departments by patients complaining of undesirable physical and psychiatric effects after taking 2-DPMP. In spring 2011 there were similar presentations for D2PM. Recreational use of these drugs has been reported only occasionally in on-line user fora. There is little scientifically-based literature on the pharmacological, physiological, psychopharmacological, toxicological and epidemiological characteristics of these drugs. Here we describe what is known about them, especially on their toxicity, including what we believe to be the first three deaths involving the use of 2-DPMP in August 2010. There are no international controls imposed on 2-DPMP or D2PM. However, a ban on their UK importation was imposed in November 2011 and they became Class C drugs on 13 June 2012. It is critical that any other cases, including non-fatal overdoses, are documented so that a scientific evidence-base can be established for them.

Cardiovascular toxicity of novel psychoactive drugs: lessons from the past

The long use of ephedrine, amphetamines, cocaine, LSD and more recently 3,4-methylenedioxy-N-methylamphetamine (MDMA; "Ecstasy") allows us to predict with some confidence what cardiovascular risks are likely to be associated with novel psychoactive substances (NPS). Once the probably multiple biological activities of a compound are known it is possible to define the likely risks of cardiovascular toxicity. Agonists of 5-HT(2A) receptors or alpha-adrenoceptors may cause vasoconstriction and tissue ischemia. Drugs which have agonist affinity for 5-HT(2B) receptors will probably promote heart valve fibrosis leading to heart failure. Compounds that interfere with uptake of dopamine or 5-hydroxytryptamine (5-HT) are likely to also have effects on noradrenergic neurotransmission and lead to sympathomimetic effects on the heart and vasculature. Drugs that cause dopamine release, or inhibit uptake are likely to be addictive and lead to chronic use. Other drugs (particularly the so-called empathogens) are associated with weekly usage in social settings; over time such use can lead to cardiovascular harm. Defining which of these effects NPS have is an important element of predicting the harm they may cause and informing those appointed to introduce regulations to control them.