Rewarding Properties of 1-Benzylpiperazine, a New Drug of Abuse, in Rats

Impure but not inactive: Behavioral pharmacology of dibenzylpiperazine, a common by-product of benzylpiperazine synthesis

BACKGROUND

Substituted piperazines comprise a substantial proportion of the novel psychoactive substance market. Among the most widely abused piperazine compounds are meta-chlorophenylpiperazine (mCPP), tri-fluoromethylphenylpiperazine (TFMPP), and, especially, benzylpiperazine (BZP), which are commonly incorporated, either alone or in combination, in illicit "party pills" or "ecstasy" formulations. Illicit synthesis of BZP often results in production of an impure by-product dibenzylpiperazine (DBZP), which frequently appears alongside BZP in these formulations; however, despite its ubiquity, little information exists regarding the abuse liability of DBZP.

AIMS

The current study aimed to evaluate the abuse-related behavioral pharmacology of DBZP.

METHODS

DBZP, mCPP, and TFMPP were tested in parallel in mice in locomotor activity and conditioned place preference assays, and in a drug discrimination assay with rats trained to discriminate either methamphetamine, cocaine, (±)-3,4-methylenedioxymethamphetamine (MDMA), or -2,5-dimethoxy-4-methylamphetamine(DOM).

RESULTS

Each of the compounds tested produced dose-dependent decreases in locomotor activity. DBZP substituted fully for methamphetamine, produced subthreshold drug-appropriate responding for cocaine and MDMA, and failed to substitute for DOM. Conversely, TFMPP and mCPP only produced subthreshold drug-appropriate responding for methamphetamine and MDMA, respectively, and both compounds failed to substitute for cocaine or DOM. None of the compounds tested produced a place preference. DBZP produced convulsions in rats at the highest dose tested.

CONCLUSIONS

These data indicate that DBZP is more similar to BZP, albeit with lower potency and efficacy, than its serotonergic piperazine counterparts, and is a behaviorally-active compound with some abuse liability and potential for adverse health effects.

Benzylpiperazine: "A messy drug"

Designer drugs are synthetic structural analogues/congeners of controlled substances with slightly modified chemical structures intended to mimic the pharmacological effects of known drugs of abuse so as to evade drug classification. Benzylpiperazine (BZP), a piperazine derivative, elevates synaptic dopamine and serotonin levels producing stimulatory and hallucinogenic effects, respectively, similar to the well-known drug of abuse, methylenedioxymethamphetamine (MDMA). Furthermore, BZP augments the release of norepinephrine by inhibiting presynaptic autoreceptors, therefore, BZP is a "messy drug" due to its multifaceted regulation of synaptic monoamine neurotransmitters. Initially, pharmaceutical companies used BZP as a therapeutic drug for the treatment of various disease states, but due to its contraindications and abuse potential it was withdrawn from the market. BZP imparts predominately sympathomimetic effects accompanied by serious cardiovascular implications. Addictive properties of BZP include behavioral sensitization, cross sensitization, conditioned place preference and repeated self-administration. Additional testing of piperazine derived drugs is needed due to a scarcity of toxicological data and widely abuse worldwide.

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.

Acute effects of BZP, TFMPP and the combination of BZP and TFMPP in comparison to dexamphetamine on an auditory oddball task using electroencephalography: a single-dose study

RATIONALE

Piperazine-based designer drugs such as benzylpiperazine (BZP) and trifluoromethylphenylpiperazine (TFMPP) have been marketed and sold as legal alternatives to dexamphetamine and 3,4-methylenedioxymethamphetamine (MDMA) until 2008 in New Zealand. When administered in combination, BZP + TFMPP have been reported to produce drug-drug synergism in rodents by stimulating the release of dopamine and serotonin.

OBJECTIVES

This study was to evaluate the acute event-related potential effects of BZP, TFMPP or the combination of BZP + TFMPP compared with dexamphetamine in young healthy male adults.

METHODS

A double-blind, randomised, placebo-controlled study investigated the effects of BZP, TFMPP, the combination of BZP + TFMPP, and dexamphetamine on the event-related potentials during an auditory oddball task. Healthy, right-handed males were given a single oral dose of either BZP (200 mg), TFMPP (60 mg), a combination of BZP + TFMPP (100/30 mg), dexamphetamine (20 mg) or placebo (lactose) and tested both before and 120 min after drug administration.

RESULTS

A single dose of either TMFPP (t = -2.29, p = 0.03) or dexamphetamine (t = -2.33, p = 0.02) significantly reduced the P300 amplitude. A similar trend was also found in BZP. In contrast, BZP and TFMPP in combination has no effect. Neither P300 latency nor the mean reaction time was affected by any of the drug treatments. In addition, neither the P100 nor the P200 component was significantly affected following any of the drug treatments.

CONCLUSIONS

A single oral dose of BZP or TFMPP, but not the combination of BZP/TFMPP, affected auditory sensory-evoked P300 potential in a manner similar to dexamphetamine.

Hepatotoxicity of piperazine designer drugs: Comparison of different in vitro models

Piperazine derived drugs emerged on the drug market in the last decade. The aim of this study was to investigate in vitro the potential hepatotoxicity of the designer drugs N-benzylpiperazine (BZP), 1-(3-trifluoromethylphenyl)piperazine (TFMPP), 1-(4-methoxyphenyl)piperazine (MeOPP) and 1-(3,4-methylenedioxybenzyl)piperazine (MDBP) in two human hepatic cell lines (HepaRG and HepG2) and in primary rat hepatocytes. Cell death was evaluated by the MTT assay, after 24 h-incubations. Among the tested drugs, TFMPP was the most cytotoxic. HepaRG cells and primary hepatocytes revealed to be the most and the least resistant cellular models, respectively. To ascertain whether the CYP450 metabolism could explain their higher susceptibility, primary hepatocytes were co-incubated with the piperazines and the CYP450 inhibitors metyrapone and quinidine, showing that CYP450-mediated metabolism contributes to the detoxification of these drugs. Additionally, the intracellular contents of reactive species, ATP, reduced (GSH) and oxidized (GSSG) glutathione, changes in mitochondrial membrane potential (Δψm) and caspase-3 activation were further evaluated in primary cells. Overall, an increase in reactive species formation, followed by intracellular GSH and ATP depletion, loss of Δψm and caspase-3 activation was observed for all piperazines, in a concentration-dependent manner. In conclusion, piperazine designer drugs produce hepatic detrimental effects that can vary in magnitude among the different analogues.

Benzylpiperazine-induced acute delirium in a patient with schizophrenia and an incidental temporal meningioma

Benzylpiperazine is a psychotropic compound that has been widely available until recently from licensed premises such as ‘head shops’. This report describes a case of a 48 year old man with schizophrenia who developed an acute delirium secondary to benzylpiperazine use, although he initially presented as a diagnostic conundrum. Investigation of his delirium unearthed a temporal meningioma which appears to be an incidental finding. This is the first documented case of delirium due to benzylpiperazine use. Benzylpiperazine has significant abuse potential and psychiatric complications. Its sale and possession have recently been made illegal in Ireland, which may limit its abuse in the future.

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.

Abuse liability of novel 'legal high' designer stimulants: evidence from animal models

In the last few years, the variety and recreational use of 'legal high' designer stimulants has increased to unprecedented levels. Since their rapid emergence in drug markets, numerous adverse physical and psychological effects have been extensively reported. However, less is understood about the potential for compulsive use of and addiction to these drugs. Recently, a small collection of scientific studies assessing the abuse liability of these drugs has emerged. This new knowledge has been derived primarily from animal studies using behaviorally based procedures which include intravenous self-administration, conditioned place preference, intracranial self-stimulation, and drug discrimination. In this review we present a brief history of the recent rise in designer stimulant use followed by a short methodological description of the aforementioned procedures. We then review neurochemical and abuse liability studies on designer stimulants that have been examined to date. Finally, we conclude with a discussion of these collective findings, our current understanding of the abuse liability of these drugs in relation to each other and the illicit drugs they are designed to mimic, and recommend future research directions.

Differential responses to anticipation of reward after an acute dose of the designer drugs benzylpiperazine (BZP) and trifluoromethylphenylpiperazine (TFMPP) alone and in combination using functional magnetic resonance imaging (fMRI)

RATIONALE

Functional magnetic resonance imaging (fMRI) studies have reported increased activation of the mesolimbic system in response to anticipation of rewarding stimuli. The anticipation of uncertain outcomes evokes activation in the amygdala, orbitofrontal cortex, inferior frontal gyrus and insula. Drugs known to effect dopaminergic and serotonergic neurons also alter regional activation.

OBJECTIVES

Benzylpiperazine (BZP) and/or trifluoromethylphenylpiperazine (TFMPP) have been recreationally used worldwide for more than a decade. BZP affects mainly dopaminergic neurons, while TFMPP has serotonergic effects.

METHODS

We investigated the effects of an acute dose of BZP, TFMPP or a combination of BZP and TFMPP on the anticipation of reward in a double-blind, placebo-controlled, crossover study using fMRI. An event-related gambling paradigm was completed by healthy controls 90 min after taking an oral dose of either BZP (200 mg), TFMPP (either 50 or 60 mg), BZP + TFMPP (100 + 30 mg) or placebo.

RESULTS

After giving BZP, the anticipation of a $4 reward decreased the activation of the inferior frontal gyrus, insula and occipital regions in comparison to placebo. TFMPP increased the activation of the putamen but decreased the activity in the insula relative to placebo. When BZP and TFMPP were given in combination, activation of the rolandic operculum occurred. The magnitude of reward also affected neural correlates.

CONCLUSION

We propose that the effects of BZP and TFMPP on dopaminergic and serotonergic circuitry, respectively, reflect regional changes. The dopaminergic effects of BZP appear to increase positive arousal and subsequently reduce the response to uncertainty, while TFMPP appears to alter the response to uncertainty by increasing emotional responses.

Estrogenic effects and their action mechanism of the major active components of party pill drugs

Benzylpiperazine (BZP) and trifluoromethylphenylpiperazine (TFMPP) are commonly used constituents of party pill drugs. They are reported to induce psychoactive effects such as euphoria and provide effects similar with other illicit drugs such as methylenedioxymethamphetamine (MDMA). A great deal of evidence has proven that party pills, as alternatives for MDMA, exert harmful effects on users. However, their toxicological effects have not been fully understood and endocrine disruptive effects are still unknown. In this study, we identified estrogenic effects of BZP and TFMPP by using in vitro and in vivo assays. BZP and TFMPP stimulated cell proliferation in a dose-dependent manner, while co-treatment with tamoxifen and BZP or TFMPP showed a decrease of E(2)-induced cell proliferation. In an estrogen sensitive reporter gene assay, BZP and TFMPP significantly increased transcriptional activities of party pill drugs. In addition, ER-related genes, PR and pS2, were significantly stimulated by BZP and TFMPP. These results indicated that BZP and TFMPP could have estrogenic activities related to the ER-mediated pathway. Unlike the in vitro assay results, BZP and TFMPP did not show significant effects on weight increase in a rodent uterotrophic assay. However, further studies would be necessary to verify the estrogenic activities of BZP and TFMPP by a chronic exposure animal study.

Piperazine compounds as drugs of abuse

Synthetic drugs are among the most commonly abused drugs in the world. This abuse is widespread among young people, especially in the dance club and rave scenes. Over the last several years, piperazine derived drugs have appeared, mainly available via the internet, and sold as ecstasy pills or under the names of "Frenzy", "Bliss", "Charge", "Herbal ecstasy", "A2", "Legal X" and "Legal E". Although in the market piperazine designer drugs have the reputation of being safe, several experimental and epidemiological studies indicate risks for humans. Piperazine designer drugs can be divided into two classes, the benzylpiperazines such as N-benzylpiperazine (BZP) and its methylenedioxy analogue 1-(3,4-methylenedioxybenzyl)piperazine (MDBP), and the phenylpiperazines such as 1-(3-chlorophenyl)piperazine (mCPP), 1-(3-trifluoromethylphenyl)piperazine (TFMPP), and 1-(4-methoxyphenyl)piperazine (MeOPP). Toxicokinetic properties, including metabolic pathways, actions and effects in animals and humans, with some hypothesis of mechanism of action, and analytical approaches for the identification of these drugs are summarized in this review.

Current awareness of piperazines: pharmacology and toxicology

Although many piperazine derivatives exist, only a limited number have been studied, whereby they have been found to be generally stimulant in nature resulting from dopaminergic, noradrenergic, and predominantly serotoninergic effects in the brain. Reported toxic effects include agitation, anxiety, cardiac symptoms (e.g. tachycardia) and sometimes seizures. As for many drugs, they are primarily metabolized by cytochrome P450 with subsequent possible glucuronidation and/or sulfation. Their abuse has been relatively recently observed in the last decade with only a few identified in biological fluid (primarily 1-benzylpiperazine (BZP) and 1-(3-trifluoromethylphenyl)piperazine (3-TFMPP)) despite publications of a number of analytical methods. Even when detected, however, the toxicological significance of their presence is often difficult to ascertain as many cases involve other drugs as well as a wide and overlapping range of concentrations found in blood (both in life and after death). This paper reviews the current pharmacological and toxicological information for piperazine derivatives and also includes new ante-mortem and post-mortem blood data.

The clinical toxicology of the designer "party pills" benzylpiperazine and trifluoromethylphenylpiperazine

INTRODUCTION

Benzylpiperazine (BZP) and trifluoromethylphenylpiperazine (TFMPP) are synthetic phenylpiperazine analogues. BZP was investigated as a potential antidepressant in the early 1970s but was found unsuitable for this purpose. More recently, BZP and TFMPP have been used as substitutes for amfetamine-derived designer drugs. They were legally available in a number of countries, particularly in New Zealand, and were marketed as party pills, but are now more heavily regulated. This article will review the mechanisms of toxicity, toxicokinetics, clinical features, diagnosis, and management of poisoning due to BZP and TFMPP.

METHODS

OVID MEDLINE and ISI Web of Science were searched systematically for studies on BZP and TFMPP and the bibliographies of identified articles were screened for additional relevant studies including nonindexed reports. Nonpeer-reviewed sources were also accessed. In all, 179 papers excluding duplicates were identified and 74 were considered relevant.

MECHANISMS OF ACTION

BZP and TFMPP have stimulant and amfetamine-like properties. They enhance the release of catecholamines, particularly of dopamine, from sympathetic nerve terminals, increasing intra-synaptic concentrations. The resulting elevated intra-synaptic monoamine concentrations cause increased activation of both central and peripheral α- and β-adrenergic postsynaptic receptors. BZP has primarily dopaminergic and noradrenergic action while TFMPP has a more direct serotonin agonist activity.

TOXICOKINETICS

There is limited information on the kinetics of these drugs. Following ingestion, peak plasma concentrations are reached after 60 to 90 min. Both drugs would be expected to cross the blood brain barrier and they are metabolized mainly by hydroxylation and N-dealkylation catalyzed by cytochrome P450 and catechol-o-methyl transferase enzymes. In humans, only small amounts of both BZP and TFMPP are excreted in the urine, suggesting a low bioavailability. The serum half-lives of BZP and TFMPP are relatively short with elimination being essentially complete in 44 h for BZP and 24 h for TFMPP.

CLINICAL FEATURES

These compounds can cause harmful effects when taken recreationally. Commonly reported features include palpitations, agitation, anxiety, confusion, dizziness, headache, tremor, mydriasis, insomnia, urine retention, and vomiting. Seizures are induced in some patients even at low doses. Severe multiorgan toxicity has been reported, though fatalities have not been recorded conclusively.

MANAGEMENT

Supportive care including the termination of seizures is paramount, with relief of symptoms usually being provided by benzodiazepines alone.

CONCLUSIONS

BZP and TFMP can cause sympathomimetic effects in the intoxicated patient. Appropriate, symptom-directed supportive care should ensure a good recovery.

Determining the subjective and physiological effects of BZP combined with TFMPP in human males

RATIONALE

‘Party Pills’ containing benzylpiperazine (BZP) and trifluoromethylphenylpiperazine (TFMPP) have been used in a recreational context since the 1990s and, prior to April 2008, were legally available in New Zealand. Taken together, they have been reported to produce a ‘high’ similar to that produced by 3,4-methylenedioxymethamphetamine (MDMA).

OBJECTIVES

There has been little research on the subjective effects of piperazines in humans. The purpose of this study is to further investigate the subjective and physiological responses following an oral dose of BZP combined with TFMPP in males.

METHODS

In a randomised, double-blind, placebo-controlled study the subjective and physiological effects of BZP/TFMPP were investigated in 36 healthy, non-smoking males (mean age 22 ± 4 years). Participants were tested before and approximately 120 min after administration of a single dose of placebo (n = 16) or 100/30 mg BZP/TFMPP (n = 20). Participants were required to comment on the subjective effects using three rating scales—the Addiction Research Centre Inventory (ARCI), the Visual Analogue Scale (VAS) and the Profile of Mood States (POMS). Participants' blood pressure, heart rate and body temperature were also measured.

RESULTS

Statistical analysis using repeated-measures analysis of variance (ANOVA) and planned comparisons revealed that BZP/TFMPP significantly increases blood pressure and heart rate (p < 0.05). Likewise, the subjective rating scales revealed that BZP/TFMPP has significant dexamphetamine-like effects, increases dysphoria and feelings of self-confidence (p < 0.05).

CONCLUSION

These physiological and subjective data reflect clear similarities between the effects of BZP/TFMPP and commonly known stimulants such as dexamphetamine and MDMA.

Pharmacokinetics of 'party pill' drug N-benzylpiperazine (BZP) in healthy human participants

There have been many reports of benzylpiperazine (BZP) and trifluoromethylphenylpiperazine (TFMPP) being used as recreational drugs which have been widely marketed in the form of 'party pills' since the late 1990's. However, there is no information currently available describing the pharmacokinetics of these drugs in humans. Human plasma concentrations of BZP were measured in blood and urine samples taken from healthy adults (n=7) over 24h following a 200mg oral dose of BZP. Plasma concentrations of BZP were found to peak at 262 ng/mL (C(max)) and 75min (T(max)). Plasma concentrations of the major metabolites of BZP, 4-OH BZP and 3-OH BZP, were found to peak at 7 ng/mL (at 60 min) and 13 ng/mL (at 75 min) respectively. The elimination half-life (t(1/2)) for BZP was found to be 5.5h. Clearance (Cl/F) was found to be 99L/h. The results of this study indicate that BZP may be detectable in plasma for up to 30 h following an oral dose. Additionally, several urinary metabolites can be detected.

The role of 5-HT3 receptors in drug abuse and as a target for pharmacotherapy

Alcohol and drug abuse continue to be a major public health problem in the United States and other industrialized nations. Extensive preclinical research indicates the mesolimbic dopamine (DA) pathway and associated regions mediate the rewarding and reinforcing effects of drugs of abuse and natural rewards, such as food and sex. The serotonergic (5-HT) system, in concert with others neurotransmitter systems, plays a key role in modulating neuronal systems within the mesolimbic pathway. A substantial portion of this modulation is mediated by activity at the 5-HT3 receptor. The 5-HT3 receptor is unique among the 5-HT receptors in that it directly gates an ion channel inducing rapid depolarization that, in turn, causes the release of neurotransmitters and/or peptides. Preclinical findings indicate that antagonism of the 5-HT3 receptor in the ventral tegmental area, nucleus accumbens or amygdala reduces alcohol self-administration and/or alcohol-associated effects. Less is known about the effects of 5-HT3 receptor activity on the self-administration of other drugs of abuse or their associated effects. Clinical findings parallel the preclinical findings such that antagonism of the 5-HT3 receptor reduces alcohol consumption and some of its subjective effects. This review provides an overview of the structure, function, and pharmacology of 5-HT3 receptors, the role of these receptors in regulating DA neurotransmission in mesolimbic brain areas, and discusses data from animal and human studies implicating 5-HT3 receptors as targets for the development of new pharmacological agents to treat addictions.

[1-benzylpiperazine (BZP) and 1-(3-trifluorométhylphényl)pipérazine (TFMPP): emergence of two agents which lead to misuse]

1-benzylpiperazine (BZP) and 1-(3-trifluoromethylphenyl)piperazine (TFMPP) are psychoactive agents which have become available on the illicit drug market in France since 2006. These compounds are employed for their stimulating, enacting, and "recreational" properties. The combination of BZP and TFMPP enables drug users to reproduce the domaminergic and serotoninergic components of amphetamine derivatives. Intoxication can be life threatening for BZP. This compound has been detected, in association with other psychoactive agents with similar action, in several fatal cases. In addition, there is a potential risk of addiction, confirmed in animal models. The toxicity of TFMPP appears to be weaker with no apparent risk of addiction. There is however a risk of serious psychiatric manifestations and serotoninergic syndrome. There are certain national regulations, but to date no international regulations have been developed for BZP and TFMPP. In the European Union, BZP is now being monitored in compliance with the 10 May 2005 decision of the Commision on information sharing, risk evaluation, and control relative to new psychoactive agents.

Benzylpiperazine: a drug of abuse?

N-benzylpiperazine (BZP) is the active ingredient in recreational 'party' or 'p.e.p.' pills, which are used to provide a stimulant, euphoric effect akin to that of methylenedioxymethamphetamine (MDMA, 'ecstasy'). BZP predominantly affects dopamine neurotransmission in a similar fashion to known 'drugs of abuse', such as methamphetamine and cocaine, which strongly suggests BZP has abuse liability. BZP is illegal in many countries including the United States of America and Australia, yet it remains legal in the United Kingdom, Canada and New Zealand. There has been little research, to date, on the neurological consequences of high dose or chronic exposure of BZP. Here we provide a comprehensive review of the information currently available on BZP and suggest a need for further research into the mechanisms of action, long-term effects and potentially addictive properties of BZP.

Measuring reward with the conditioned place preference (CPP) paradigm: update of the last decade

Conditioned place preference (CPP) continues to be one of the most popular models to study the motivational effects of drugs and non-drug treatments in experimental animals. This is obvious from a steady year-to-year increase in the number of publications reporting the use this model. Since the compilation of the preceding review in 1998, more than 1000 new studies using place conditioning have been published, and the aim of the present review is to provide an overview of these recent publications. There are a number of trends and developments that are obvious in the literature of the last decade. First, as more and more knockout and transgenic animals become available, place conditioning is increasingly used to assess the motivational effects of drugs or non-drug rewards in genetically modified animals. Second, there is a still small but growing literature on the use of place conditioning to study the motivational aspects of pain, a field of pre-clinical research that has so far received little attention, because of the lack of appropriate animal models. Third, place conditioning continues to be widely used to study tolerance and sensitization to the rewarding effects of drugs induced by pre-treatment regimens. Fourth, extinction/reinstatement procedures in place conditioning are becoming increasingly popular. This interesting approach is thought to model certain aspects of relapse to addictive behavior and has previously almost exclusively been studied in drug self-administration paradigms. It has now also become established in the place conditioning literature and provides an additional and technically easy approach to this important phenomenon. The enormous number of studies to be covered in this review prevented in-depth discussion of many methodological, pharmacological or neurobiological aspects; to a large extent, the presentation of data had to be limited to a short and condensed summary of the most relevant findings.

Chronic benzylpiperazine (BZP) exposure produces behavioral sensitization and cross-sensitization to methamphetamine (MA)

BACKGROUND

Like other psychostimulant drugs, acute exposure to benzylpiperazine (BZP) increases dopaminergic neurotransmission, producing hyperactivity and stereotypy. The consequences of repeated BZP exposure have not however been investigated. The effects of acute and repeated BZP and methamphetamine (MA) exposure on locomotor activity and stereotypy were measured in order to determine whether there was sensitization and cross-sensitization between these two psychostimulant drugs.

METHODS

The effects of acute treatment with MA (0.0, 0.5, 1.0 and 2.0 mg/kg, intraperitoneal (IP)) or BZP (0.0, 5.0, 10.0, 20.0 and 40.0 mg/kg, IP) on locomotor activity and stereotypy were determined. Effects of repeated exposure were determined in other groups that received five daily injections of 2.0 mg/kg MA, 20.0 mg/kg BZP or vehicle. Following a 2-day withdrawal period, rats from each treatment group received either a low dose MA (0.5 mg/kg) or BZP (10.0 mg/kg).

RESULTS

MA and BZP produced dose-dependent hyperactivity and stereotypy. Repeated MA and BZP resulted in a potentiated locomotor but not stereotypy response. Following the withdrawal period, MA pretreated rats exhibited a sensitized locomotor and stereotypy response to the low dose MA and a conditioned response to saline. BZP pretreated rats also demonstrated a sensitized locomotor response to the low dose of BZP and MA.

CONCLUSIONS

The present findings indicate that repeated exposure to BZP results in sensitization and cross-sensitization to MA.