Recent trends in the use of "club drugs": an Australian review

Psychotic-Like Experiences in Young Recreational Users of Ketamine: A Case Study

This study explores the psychotic-like experiences (PLEs) associated with recreational ketamine use among young adults. Ketamine, initially introduced as an anesthetic, is now widely used recreationally for its dissociative effects, raising concerns about its impact on mental health. Ten participants aged 18-24, who used ketamine recreationally multiple times a week, were assessed using the Community Assessment of Psychic Experiences (CAPE-42). Results showed a significant positive correlation between the frequency of ketamine use and PLEs, with no significant impact from other substances like THC, MDMA, and alcohol. These findings confirm ketamine's potential to induce psychotic-like symptoms by antagonizing NMDA receptors, similar to schizophrenia. The study underscores the need for preventive measures and targeted interventions to address the mental health risks of frequent ketamine use, particularly among young adults. However, limitations such as the small sample size and reliance on self-reported data suggest that further research is needed to establish causality and examine long-term effects. Overall, this study highlights the significant association between recreational ketamine use and increased PLEs, emphasizing the importance of early detection and intervention strategies.

Ketamine in DUID cases in the greater Cologne area

INTRODUCTION

Ketamine is primarily used as an anaesthetic or for analgesics in medical treatment, but due to its dissociative and hallucinogenic effects, abuse has increased in the past years leading to several drug impaired driving cases.

METHODS

Eight DUID (driving under the influence of drugs) cases involving ketamine from two institutes of legal medicine over a period from January 2021 to January 2023 were evaluated. The cases were compared with regard to psychomotor impairments, adverse effects on driving performance and co-consumption of drugs. Analyses of ketamine were carried out by high performance liquid chromatography with diode array detection (HPLC-DAD). Other drugs of abuse were either detected via liquid chromatography with tandem mass spectromety (LC-MS/MS) and/or gas chromatography with (tandem) mass spectrometry (GC-MS(/MS)).

RESULTS

Ketamine plasma concentrations in a range of approx. 100-1200 ng/mL (mean: 510 ng/mL, median: 370 ng/mL) were detected. Co-consumption of at least one substance was ascertained in all cases. Besides driving impairments, recorded psychomotor impairments of the drivers comprised e.g. dilated pupils, missing or delayed pupil reactions, a slurred or decelerated speech, delayed reaction, lack of concentration, vertigo or agitation.

DISCUSSION

The observed peculiarities were in-line with literature data. However, the assessment and differentiation of ketamine-induced impairments was aggravated due to co-consumption of other drugs of abuse or pharmaceuticals in the herein investigated cases. Nevertheless, in two cases impairments can be attributed mainly to ketamine consumption since the co-consumed substances were only detected in low concentrations.

CONCLUSION

The presented cases provide additional data on psychomotor impairments observed in ketamine-related DUID cases. Limiting factors are co-consumption of substances, unknown habituation to drugs and the limited case number. Nevertheless, the results of this study are comparable with existing literature data. Since the abuse of ketamine has increased in the past years, these data will support forensic casework.

Drug users' awareness of and willingness to use HIV non-occupational post-exposure prophylaxis (nPEP) services in China: a mixed methods study

Background

Drug users are regarded as a high-risk population for HIV infection. Non-occupational post-exposure prophylaxis (nPEP) is internationally regarded as an effective biomedical prevention against HIV but still a small-scale pilot project in China at present. The aim of this study was to understand drug users’ awareness of and willingness to use nPEP service in China.

Methods

This mixed methods study consisting of a qualitative study and a cross-sectional survey was conducted in two cities of China from 2018 to 2019. The in-depth interviews were audio-taped, transcribed verbatim and analyzed using thematic framework analysis. Univariate and multivariate logistic regressions were used to examine factors associated with drug users’ awareness of and willingness to use nPEP.

Results

There were 401 and 19 participants included in quantitative and qualitative study respectively. Among participants in quantitative study, 30.2% had heard of nPEP and 56.7% reported willingness to use nPEP in future HIV exposure. In multivariate analyses, nPEP awareness was associated with age, sex, education level, AIDS knowledge score and HIV risk perception. nPEP willingness was associated with AIDS knowledge score, HIV risk perception, alcohol use, monthly income and awareness of nPEP. The qualitative results showed the barriers to nPEP willingness included the fatigue after taking drugs, high cost and side effects of nPEP medication, long nPEP course, and fear of privacy disclosure.

Conclusion

Drug users had low nPEP awareness and only about half participants reported willingness to use nPEP. It is essential to promote nPEP education campaigns among drug users, especially for elders, women and those with lower education level. Simultaneously, price regulation, side effect management, psychological support and privacy protection need to be managed well when nPEP is routinized.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07106-x.

The impact of Taiwan's implementation of a nationwide harm reduction program in 2006 on the use of various illicit drugs: trend analysis of first-time offenders from 2001 to 2017

Background

After implementing a nationwide harm reduction program in 2006, a dramatic decline in the incidence of human immunodeficiency virus (HIV) infection among people with injection drug use (IDU) was observed in Taiwan. The harm reduction program might have sent out the message discouraging the choice of IDU among illicit drug users in early stage. Based on the yearly first-time offense rates from 2001 to 2017, this study aimed to examine (1) whether the nationwide implementation of the harm reduction program in 2006 led to changes in first-time offenders’ use of heroin; (2) whether the intervention had a similar effect on the use of other illicit drugs; and (3) whether the effect of the intervention was limited to the first-time offenders of young age groups.

Methods

Yearly first-time illicit-drug offense rates from 2001 to 2017 in Taiwan were derived from two national databases for drug arrests that were verified using urine tests: the Criminal Record Processing System on Schedule I/II Drugs and the Administrative Penalty System for Schedule III/IV Substances. A hierarchy of mutually exclusive categories of drug uses was defined by the drug with the highest schedule level among those tested positive in an arrest. Segmented regression analyses of interrupted time series were used to test for the impact of the 2006 intervention.

Results

There was a decrease of 22.37 per 100,000 in the rate for heroin but no detectable level changes in that for methamphetamine or ecstasy after the 2006 intervention in Taiwan. There were baseline decreasing trends in the first-time offense rate from 2001 to 2017 for heroin and ecstasy and an increasing trend for methamphetamine, with the slopes not altered by the 2006 intervention. The postintervention decrease in the first-time offense rate for heroin was detectable among offenders less than 40 years old.

Conclusions

Our results indicate a diffusion effect of the 2006 intervention on decreasing heroin use among young offenders and have policy implications for better prevention and treatment for different age groups.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12954-021-00566-5.

Development and Psychometric Properties of the Synthetic Drug Dependence Scale in a Chinese Sample

Objective: In contrast to the drug situation in the rest of the world, synthetic drugs, rather than traditional drugs, have been the dominant abused drugs in China since 2019. However, the public misconception that synthetic drugs are not as addictive as traditional drugs, such as opioids and the scarcity of specific measurement instruments, have hindered the clinical diagnosis and treatment of synthetic drug abusers, thus the development of a localized instrument to evaluate dependence on synthetic drugs is in urgently needed.

Method: Using a sample of 618 Chinese synthetic drug abusers (Mean age = 34.69 years; 44.17% female), the present study developed and examined the psychometric properties of a self-reporting instrument, the Synthetic Drug Dependence Scale (SDDS), which consists of four subscales: physical dependence, psychological dependence, health injury, and social function injury.

Results: The SDDS revealed a three-factor model structure (weighted root mean square residual (WRMR) = 0.876, comparative fit index (CFI) = 0.965, Tucker–Lewis index (TLI) = 0.953, and Root mean square error of approximation (RMSEA) = 0.070), with good internal consistency (composite reliability = 0.912, alfa = 0.801) and convergent validity. Elevated scores on the SDDS were associated with a higher level of reward sensitivity, punishment sensitivity, and stronger impulsivity. Interestingly, psychological dependence was the only significant predictor (p < 0.05) of criterion variables compared with the other three subscales, implying the important role of psychological factors in synthetic drugs dependence. Adequate measurement equivalence across sex, age (18–30 and 31–57 years old), and employment group (employed and unemployed) was also established.

Conclusion: The SDDS appears to be an effective and reliable instrument that could be used to further investigate the characteristics of synthetic and traditional drug dependence, promoting a deeper understanding of the physical and psychological roles in drug dependence.

Recreational ketamine-related deaths notified to the National Programme on Substance Abuse Deaths, England, 1997-2019

BACKGROUND

Ketamine is a phencyclidine derivative with dissociative anaesthetic properties. Increasing numbers of individuals in England take ketamine recreationally. Information on deaths arising from such use in England is presented.

METHODS

Cases were extracted on 31 January 2020 from the National Programme on Substance Abuse Deaths database, based on text searches of the cause of death, coroner's verdict and positive toxicology results for the terms 'ketamine' or 'norketamine'.

FINDINGS

During 1997-2005, there were <5 deaths p.a. in which ketamine was implicated. Numbers increased until 2009 (21), plateauing until 2016; thereafter, deaths have risen to about 30 p.a. Decedents' characteristics (N = 283): male 84.1%, mean age 31.2 (SD 10.0) years, employed 56.5%, drug use history 79.6% and living with others 60.3%. Ketamine was detected with other substances in most cases. Main (74.6%) underlying cause of death was accidental poisoning. Ketamine may have impaired judgement in other cases.

CONCLUSIONS

Although controlled, recreational ketamine use and related fatalities continue to increase. Consumers need to be more aware of the potentially fatal risks they face.

First-time offenders for recreational ketamine use under a new penalty system in Taiwan: incidence, recidivism and mortality in national cohorts from 2009 to 2017

BACKGROUND AND AIMS

Ketamine has become a new recreational drug of choice among young people in parts of Asia. Using national databases in Taiwan, this study aimed to (1) examine the yearly trend in the ketamine offence rate over time; (2) estimate the 3-year risk of drug-related re-offence and its correlates among the first-time offenders; and (3) estimate the 3-year standardized mortality ratio (SMR) among the first-time offenders.

DESIGN, SETTING AND PARTICIPANTS

Retrospective cohort studies of offenders for recreational ketamine use in a penalty system initiated in 2009. Offenders for recreational ketamine use were identified from the Administrative Penalty System for Schedule III/IV Substances database from 2009 to 2017, and the re-offence rate and mortality among first-time offenders were assessed via record-linkage within the database as well as with both the criminal drug offence database and the national mortality database. The cohort from 2009 to 2016 (n = 39 178) was used for the recidivism analysis and the cohort from 2009 to 2013 (n = 25 357) was used for the 3-year SMR analysis.

MEASUREMENTS

Recidivism was estimated using survival analysis of the event as re-arrest for using ketamine, more serious illicit drugs (Schedules I/II), or any illicit drugs (ketamine or Schedules I/II). SMRs were estimated for overall and cause-specific death within 3 years after the first offence for ketamine use.

FINDINGS

The age-standardized rates for both prevalent (1.38 per 1000) and first-time offenders (0.65 per 1000) peaked in 2013 and then decreased steadily. The 3-year risk of re-offence was 33.85% [95% confidence interval (CI) = 33.23-34.47%) for ketamine use and 39.52% (95% CI = 39.00-40.04%) for any illicit drug use. These first-time offenders had an SMR of 4.9 (95% CI = 4.3-5.4) for overall mortality, 2.1 (95% CI = 1.6-2.7) for natural deaths and 7.6 (95% CI = 6.7-8.6) for unnatural deaths.

CONCLUSIONS

Recreational ketamine use in Taiwan appears to lead not only to high risk for drug-related re-offence but also to excess mortality.

Prevalence and Correlates of Illicit Drug Use among Norwegian Nightlife Patrons

BACKGROUND

Nightclubs and bars are recreational settings with extensive availability and consumption of alcohol and recreational drugs.

OBJECTIVES

This study aims to determine the proportion of nightclub patrons in Norway that tested positive for illicit drugs, moreover, we examined the correlation between positive test results and demographic and substance use characteristics.

METHODS

Patrons were recruited outside nightclubs on Friday and Saturday nights between 10:00 pm and 04:00 am. Substance use was determined by breath testing and oral fluid testing for alcohol and drugs, respectively, using accurate and specific analytical methods. Questionnaires recorded demographic and substance use characteristics.

RESULTS

Of the 1988 included nightclub patrons, 90% tested positive for alcohol, 14% for illicit drug use, and 3% for two or more illicit drugs. The proportion of patrons who tested positive for illicit drugs was highest in the early hours of the morning. Nine out of ten who tested positive for illicit drugs also consumed alcohol. Testing positive for one or more illicit drugs was most strongly correlated with being male and unemployed, using tobacco or other nicotine products, and early on-set illicit drug use; further the correlations were strongest among those who tested positive for two or more illicit drugs.Conclusions/Importance: Patrons who used illicit drugs before or during nightclub visits most often combined drug use with alcohol consumption. Substituting alcohol with cannabis or other drugs was not common in this cohort. The study results provide evidence to introduce harm-reduction prevention programs to address illicit drug and excessive alcohol consumption.

Early sexual initiation and risky sexual practices among alcohol- and tobacco-using young adults in Taiwan: mediation analysis of preceding-sex use of illicit drugs

BACKGROUND

As early sexual initiation is increasingly common in East Asia, we examined its relations to risky sexual practices in alcohol- and tobacco-using individuals in Taiwan and evaluated whether the associations were mediated through preceding-sex use of illicit drugs.

METHODS

Participants, recruited from alcohol- and tobacco-using adults aged 18 to 50 in Taipei through respondent-driven sampling (N = 1115), completed a computer-assisted self-interview covering questions on substance use and sexual experiences. In a subsample of 916 participants who had had sexual experience (median age 27), we examined the relations of early sexual initiation (< 16 years) to multiple sexual partners, casual sex, group sex, and rare condom use. Causal mediation analyses were conducted to examine whether illicit drug use preceding sex mediated these associations.

RESULTS

Around 9.3% reported early sexual initiation and the prevalence of risky sexual practices ranged from 7% (group sex) to 47% (rare condom use). Early initiators had a higher prevalence of regular binge drinking, illicit drug use, and risky sexual practices. In the multivariable analyses, higher odds of multiple sexual partners, casual sex, and group sex were consistently associated with early sexual initiation, gender, and their interaction. Mediation through preceding-sex use of illicit drugs was found between early sexual initiation and the three risky sexual practices, with the proportions mediated ranging from 17 to 19%.

CONCLUSIONS

Early sexual initiators were more likely to engage in risky sexual practices and preceding-sex use of illicit drugs partially explained this relationship, calling for more attention to this population's sexual health.

Profiling of behavioral effects evoked by ketamine and the role of 5HT2 and D2 receptors in ketamine-induced locomotor sensitization in mice

Ketamine has addictive potential, a troublesome fact due to its promising use as a therapeutic drug. An important phenomenon associated with drug addiction is behavioral sensitization, usually characterized as augmented locomotion. However, other behaviors may also be susceptible to sensitization, and/or interfere with locomotor activity. Thus, this study drew a comprehensive behavioral 'profiling' in an animal model of repeated administration of ketamine. Adult Swiss mice received single daily ketamine injections (30 or 50 mg/Kg, i.p.), which were followed by open field testing for 7 days (acquisition period, ACQ). A ketamine challenge (sensitization test, ST) was carried out after a 5-day withdrawal. Locomotion, rearing, grooming, rotation and falling were assessed during ACQ and ST. All behaviors were affected from the first ACQ day onwards, with no indication of competition between locomotion and the other behaviors. Only locomotion in response to 30 mg/Kg of ketamine both escalated during ACQ and expressed increased levels at ST, evidencing development and expression of locomotor sensitization. Considering the involvement of serotonin 5HT₍₂₎ and dopamine D₍₂₎ receptors on addiction mechanisms, we further tested the involvement of these receptors in ketamine-induced sensitization. Ketanserin (5HT₂ antagonist, 3 mg/Kg, s.c.) prevented ketamine-evoked development of locomotor sensitization. However, ketanserin pretreatment during ACQ failed to inhibit its expression during ST. Raclopride (D₂ antagonist, 0.5 mg/Kg, s.c.) evoked less robust reductions in locomotion but prevented the development of ketamine-evoked sensitization. Pretreatment during ACQ further inhibited the expression of sensitization during ST. These results indicate that a partial overlap in serotonergic and dopaminergic mechanisms underlies ketamine-induced locomotor sensitization.

Of mice and men on MDMA: A translational comparison of the neuropsychobiological effects of 3,4-methylenedioxymethamphetamine ('Ecstasy')

MDMA (3,4-methylendioxymethamphetamine), also known as Ecstasy, is a stimulant drug recreationally used by young adults usually in dance clubs and raves. Acute MDMA administration increases serotonin, dopamine and noradrenaline by reversing the action of the monoamine transporters. In this work, we review the studies carried out over the last 30 years on the neuropsychobiological effects of MDMA in humans and mice and summarise the current knowledge. The two species differ with respect to the neurochemical consequences of chronic MDMA, since it preferentially induces serotonergic dysfunction in humans and dopaminergic neurotoxicity in mice. However, MDMA alters brain structure and function and induces hormonal, psychomotor, neurocognitive, psychosocial and psychiatric outcomes in both species, as well as physically damaging and teratogen effects. Pharmacological and genetic studies in mice have increased our knowledge of the neurochemical substrate of the multiple effects of MDMA. Future work in this area may contribute to developing pharmacological treatments for MDMA-related disorders.

Polysubstance use patterns and novel synthetics: A cluster analysis from three U.S. cities

The rapid emergence of novel psychoactive substances within the past decade has raised new concerns about the harms associated with unregulated drug use. Synthetic analogues-chemically related to established psychoactive substances like cannabis sativa and catha edulis-in particular have proliferated rapidly, allowing little opportunity for scientific research or the establishment of informal guidelines for safe use among consumers. To explore how synthetic substance use relates to other forms of use, this paper presents an analysis of polysubstance use among a sample of 676 people who use illicit substances in the United States. Participants were sampled from three greater metropolitan areas (Houston/Galveston, Texas; New York City; and New Orleans, Louisiana). Study researchers used cluster-type analyses to develop dendrogram visualizations of the interrelationships between substance types. Results suggest a considerable variation in substance and polysubstance use patterns across states in the U.S. Polysubstance use clustered around well-observed combinations like MDMA/cannabis and cocaine/heroin. Synthetic cannabinoids and cathinones showed no strong clustering with other substances. High rates of binge drinking among users of other substances further support the importance of interventions sensitive to the clinical challenges of polysubstance use.

Factors Correlating to the Development of Hepatitis C Virus Infection among Drug Users-Findings from a Systematic Review and Meta-Analysis

Hepatitis C remains a significant public health threat. However, the main routes of transmission have changed since the early 1990s. Currently, drug use is the main source of hepatitis C virus (HCV) infection, and some measures have been successively implemented and additional studies have been published. However, the factors correlating with HCV infection failed to clearly define. Our study pooled the odds ratios (ORs) with 95% confidence intervals (CIs) and analyzed sensitivity by searching data in the PubMed, Elsevier, Springer, Wiley, and EBSCO databases. Publication bias was determined by Egger's test. In our meta-analysis, HCV-infected and non-HCV-infected patients from 49 studies were analyzed. The pooled ORs with 95% CIs for study factors were as follows: Injecting drug use 10.11 (8.54, 11.97); sharing needles and syringes 2.24 (1.78, 2.83); duration of drug use >5 years 2.39 (1.54, 3.71); unemployment 1.50 (1.22, 1.85); commercial sexual behavior 1.00 (0.73, 1.38); married or cohabiting with a regular partner 0.88 (0.79, 0.98), and sexual behavior without a condom 1.72 (1.07, 2.78). This study found that drug users with histories of injecting drug use, sharing needles and syringes, drug use duration of >5 years, and unemployment, were at increased risk of HCV infection. Our findings indicate that sterile needles and syringes should be made available to ensure safe injection. In view of that, methadone maintenance treatment can reduce or put an end to risky drug-use behaviors, and should be scaled up further, thereby reducing HCV infection.

“Charging” and “Blowing Out”: Patterns and Cultures of GHB Use in Melbourne, Australia

Recent increases in the use of gamma hydroxybutyrate (GHB) in club and rave settings have been associated with a series of acute health problems including overdose. Drawing upon research recently completed in Melbourne, Australia among a sample of young club and rave patrons, this article explores the knowledge, attitudes and related “risk-behaviors” of individuals who use GHB, as well as the various cultures and contexts surrounding its use. A mixed quantitative and qualitative research design was utilized, comprising a detailed survey (N=923) and semistructured interviews (N=24). Almost all survey respondents reported to have consumed illicit drugs in the past, with around half reporting “lifetime” use of GHB. A quarter reported using GHB in the past year. GHB related harms were widely reported with 22% of GHB users reporting to have overdosed on the drug at least once. The article closes with recommendations for GHB specific prevention and harm reduction strategies.

Effects of Subanesthetic Ketamine Administration on Visual and Auditory Event-Related Potentials (ERP) in Humans: A Systematic Review

Ketamine is a non-competitive N-Methyl-D-Aspartate (NMDA) receptor antagonist whose effect in subanesthetic doses has been studied for chronic pain and mood disorders treatment. It has been proposed that ketamine could change the perception of nociceptive stimuli by modulating the cortical connectivity and altering the top-down mechanisms that control conscious pain perception. As this is a strictly central effect, it would be relevant to provide fresh insight into ketamine's effect on cortical response to external stimuli. Event-related potentials (ERPs) reflect the combined synchronic activity of postsynaptic potentials of many cortical pyramidal neurons similarly oriented, being a well-established technique to study cortical responses to sensory input. Therefore, the aim of this study was to examine the current evidence of subanesthetic ketamine doses on patterns of cortical activity based on ERPs in healthy subjects. To answer the question whether ERPs could be potential markers of the cortical effects of ketamine, we conducted a systematic review of ketamine's effect on ERPs after single and repeated doses. We have searched PubMed, EMBASE and Cochrane Databases and pre-selected 141 articles, 18 of which met the inclusion criteria. Our findings suggest that after ketamine administration some ERP parameters are reduced (reduced N2, P2, and P3 amplitudes, PN and MMN) while others remain stable or are even increased (P50 reduction, PPI, P1, and N1 amplitudes). The current understanding of these effects is that ketamine alters the perceived contrast between distinct visual and auditory stimuli. The analgesic effect of ketamine might also be influenced by a decreased affective discrimination of sensorial information, a finding from studies using ketamine as a model for schizophrenia, but that can give an important hint not only for the treatment of mood disorders, but also to treat pain and ketamine abuse.

Genuine sildenafil tablets sold in Brazil disguised as MDMA

MDMA and sildenafil are two examples among many substances consumed in "raves", as well as in other types of "recreative" social events nowadays. During the first six months of 2017, five cases of supposedly MDMA tablets seized by local law enforcement forces in the state of Minas Gerais, Brazil, and brought to our forensic laboratory for examination, attracted our attention among dozens of others, as the tablets apprehended in these cases were, in fact, colorfully painted versions of genuine, pentagon-shaped, sildenafil tablets, freely available for sale in local pharmacies and drugstores. Physical profiling, together with ATR-FTIR spectral matching, multi-component/deconvolution analysis and correlation were employed to prove that these tablets were genuine sildenafil tablets from a specific manufacturer, painted in a colorful way so that they could be marketed as MDMA tablets to unsuspecting buyers.

Intoxication with GHB/GBL: characteristics and trends from ambulance-attended overdoses

BACKGROUND

Overdoses from so-called "club drugs" (GHB/GBL) have become a more frequent cause of overdoses attended by ambulance services. Given its availability, affordability, and lack of awareness of risks, there is a common misconception among users that the drug is relatively safe.

METHODS

This study reviewed ambulance records in Bergen, Norway between 2009 and 2015 for cases of acute poisonings, particularly from suspected GHB/GBL intoxication.

RESULTS

In total, 1112 cases of GHB and GBL poisoning were identified. GHB was suspected for 995 (89%) of the patients. Men made up the majority of the cases (n = 752, 67.6%) with a median age of 27 years old. Temporal trends for GHB/GBL overdoses displayed a late-night, weekend pattern. The most frequent initial symptoms reported were unconsciousness, or reduced consciousness. Most of the patients required further treatment and transport. During the period from 2009 to 2015, there was a nearly 50% decrease in GHB/GBL overdoses from 2013 to 2014.

DISCUSSION

The characteristics of GHB/GBL overdose victims shed light on this patient group. The decrease in incidence over the years may be partly due to a legal ban on GBL in Norway, declared in 2010. It may also be due to an increase in the use of MDMA/ecstasy.

CONCLUSION

The review of ambulance records on the prehospital treatment of overdoses can be beneficial in monitoring, preparing, and prevention efforts aimed to benefit this vulnerable group.

Ketamine Increases the Function of γ-Aminobutyric Acid Type A Receptors in Hippocampal and Cortical Neurons

BACKGROUND

The "dissociative " general anesthetic ketamine is a well-known N-methyl-D-aspartate receptor antagonist. However, whether ketamine, at clinically relevant concentrations, increases the activity of inhibitory γ-aminobutyric acid (GABA) receptor type A (GABAA) receptors in different brain regions remains controversial. Here, the authors studied the effects of ketamine on synaptic and extrasynaptic GABAA receptors in hippocampal neurons. Ketamine modulation of extrasynaptic GABAA receptors in cortical neurons was also examined.

METHODS

Whole cell currents were recorded from cultured murine neurons. Current evoked by exogenous GABA, miniature inhibitory postsynaptic currents, and currents directly activated by ketamine were studied.

RESULTS

Ketamine did not alter the amplitude, frequency, or kinetics of postsynaptic currents but increased a tonic inhibitory current generated by extrasynaptic GABAA receptors in hippocampal neurons. For example, ketamine (100 µM) increased the tonic current by 33.6 ± 6.5% (mean ± SEM; 95% CI, 18.2 to 48.9; n = 8, P < 0.001). Ketamine shifted the GABA concentration-response curve to the left, but only when GABAA receptors were activated by low concentrations of GABA (n = 6). The selective increase in tonic current was attributed to ketamine increasing the apparent potency of GABA at high-affinity extrasynaptic GABAA receptors. Ketamine also increased a tonic current in cortical neurons (n = 11). Ketamine directly gated the opening of GABAA receptors, but only at high concentrations that are unlikely to occur during clinical use.

CONCLUSIONS

Clinically relevant concentrations of ketamine increased the activity of high-affinity extrasynaptic GABAA receptors in the hippocampus and cortex, an effect that likely contributes to ketamine's neurodepressive properties.

Changes in hippocampal AMPA receptors and cognitive impairments in chronic ketamine addiction models: another understanding of ketamine CNS toxicity

Ketamine has been reported to impair human cognitive function as a recreational drug of abuse. However, chronic effects of ketamine on central nervous system need to be further explored. We set out to establish chronic ketamine addiction models by giving mice a three or six month course of daily intraperitoneal injections of ketamine, then examined whether long-term ketamine administration induced cognition deficits and changed hippocampal post-synaptic protein expression in adult mice. Behavior tests results showed that mice exhibited dose- and time-dependent learning and memory deficits after long-term ketamine administration. Western blot results showed levels of GluA1, p-S845 and p-S831 proteins demonstrated significant decline with ketamine 60 mg/kg until six months administration paradigm. But levels of p-S845 and p-S831 proteins exhibited obvious increase with ketamine 60 mg/kg three months administration paradigm. NR1 protein levels significantly decrease with ketamine 60 mg/kg three and six months administration paradigm. Our results indicate that reduced expression levels and decreased phosphorylation levels of hippocampal post-synaptic membrane GluA1- containing AMPA receptors maybe involved in cognition impairment after long-term ketamine administration. These findings provide further evidence for the cognitive damage of chronic ketamine addiction as a recreational drug.

The synthesis and characterisation of MDMA derived from a catalytic oxidation of material isolated from black pepper reveals potential route specific impurities

This work examines the chemical synthesis of 3,4-methylenedioxy-N-methylamphetamine (MDMA) from piperonal prepared via a catalytic ruthenium tetroxide oxidation of piperine extracted from black pepper. A variety of oxidation conditions were experimented with including different solvent systems and co-oxidants. A sample of prepared piperonal was successfully converted into MDMA via 3,4-methylenedioxyphenyl-2-nitropropene (MDP2NP) and 3,4-methylenedioxyphenyl-2-propanone (MDP2P) and the impurities within each product characterised by GC-MS to give a contaminant profile of the synthetic pathway. Interestingly, it was discovered that a chlorinated analogue of piperonal (6-chloropiperonal) was created during the oxidation process by an as yet unknown mechanism. This impurity reacted alongside piperonal to give chlorinated analogues of each precursor, ultimately yielding 2-chloro-4,5-methylenedioxymethamphetamine (6-Cl-MDMA) as an impurity within the MDMA sample. The methodology developed is a simple way to synthesise a substantial amount of precursor material with easy to obtain reagents. The results also show that chlorinated MDMA analogues, previously thought to be deliberately included adulterants, may in fact be route specific impurities with potential application in determining the origin and synthesis method of seized illicit drugs.

GABA(B) receptor-mediated activation of astrocytes by gamma-hydroxybutyric acid

The gamma-aminobutyric acid (GABA) metabolite gamma-hydroxybutyric acid (GHB) shows a variety of behavioural effects when administered to animals and humans, including reward/addiction properties and absence seizures. At the cellular level, these actions of GHB are mediated by activation of neuronal GABA_B receptors (GABA_BRs) where it acts as a weak agonist. Because astrocytes respond to endogenous and exogenously applied GABA by activation of both GABA_A and GABA_BRs, here we investigated the action of GHB on astrocytes on the ventral tegmental area (VTA) and the ventrobasal (VB) thalamic nucleus, two brain areas involved in the reward and proepileptic action of GHB, respectively, and compared it with that of the potent GABA_BR agonist baclofen. We found that GHB and baclofen elicited dose-dependent (ED₅₀: 1.6 mM and 1.3 µM, respectively) transient increases in intracellular Ca²⁺ in VTA and VB astrocytes of young mice and rats, which were accounted for by activation of their GABA_BRs and mediated by Ca²⁺ release from intracellular store release. In contrast, prolonged GHB and baclofen exposure caused a reduction in spontaneous astrocyte activity and glutamate release from VTA astrocytes. These findings have key (patho)physiological implications for our understanding of the addictive and proepileptic actions of GHB.

Nonproblematic Illegal Drug Use

Given the scant knowledge regarding illicit drug users who maintain an overall conventional lifestyle, we aimed to develop a conceptual framework to understand how they manage to keep their drug use nonproblematic. We were interested in the individual’s experiential component, so we interviewed nonproblematic, ex-problematic and problematic Portuguese drug users. The conceptual framework was developed through the first group’s data and then validated through a new consultation with these participants and a triangulation of sources and methodologies (observation). Findings show that some subjects managed to keep their drug use nonproblematic through ongoing self-regulation as a result of cost-benefit analysis and drug use management strategies. These strategies resulted mainly from the users’ characteristics, the quality of drug using experiences, and experiences with other users. The importance of this study is in recognizing that nonproblematic drug use exists and that therein may lie important clues on how to minimize problematic use.

Self-reported prevalence of dependence of MDMA compared to cocaine, mephedrone and ketamine among a sample of recreational poly-drug users

BACKGROUND

Evidence regarding MDMA (ecstasy) dependence and the most suitable criteria for its assessment are controversial. This study aimed to assess the prevalence of last year symptoms of dependence upon MDMA compared to cocaine, mephedrone and ketamine among a large global non-treatment seeking sample.

METHODS

A cross-sectional anonymous online survey was promoted by a UK-based dance music website between 15 November 2010 and 1 January 2011. Endorsement of DSM-IV (Diagnostic and Statistical Manual of Mental Disorders) dependence criteria was sought from all last year users of MDMA, cocaine, mephedrone and ketamine. Reporting ≥3 dependence symptoms was indicative of dependence. Logistic regression models with Generalized Estimating Equations were used to compare dependence symptoms between groups.

RESULTS

MDMA users were more likely to report ≥3 DSM-IV dependence symptoms compared to users of cocaine (odds ratio OR 0.81, 95% confidence interval CI 0.71-0.93), mephedrone (OR 0.91, 95%CI 0.78-1.06) and ketamine (OR 0.52, 95%CI 0.44-0.62) (p<0.001). MDMA users were less likely to report desire to use less or get help compared to users of other substances (p<0.001). MDMA got the highest rating of pleasurable high (mean 8.2±1.7) and lowest rating for risk of harm (mean 2.7±2.4).

CONCLUSIONS

Our results highlight the self-reported dependence potential of MDMA but low desire to use less or get help. MDMA's pleasurable effects may compensate for drug-related problems and, therefore, DSM-IV criteria may not be suitable for assessing MDMA dependence. Further research is needed on the ability of DSM-V to assess MDMA dependence.

Risk factors of γ-hydroxybutyrate overdosing

The aim of this study was to identify in recreational drug users the factors which increase the risk of overdosing (OD) with γ-hydroxybutyrate (GHB). A purposive sample of 45 experienced GHB users was interviewed, equally divided into three groups (never OD, occasional OD, and repeat OD). The repeat OD group scored highest on many risk factors regarding GHB use, the occasional OD group scored intermediate, and the never OD group scored lowest. Participants, whether or not they had overdosed on GHB, most often perceived GHB use (e.g. using more GHB than usual, using GHB doses too closely together) as the main reason for GHB OD, and many participants who had overdosed on GHB reported that they had taken more GHB than usual at their most recent occasion of GHB OD. No significant differences in co-use of GHB with other substances were found between the three groups. Our findings indicate that using GHB in the company of groups of friends probably reduces, but does not eliminate, the risk of OD.

Sexual risk behaviors among club drug users in Shanghai, China: prevalence and correlates

We surveyed 276 club drug users in Shanghai, China. Overall, 43.8 % reported ≥2 sex partners in the past 30 days, and 48.9 % reported having sex with non-regular partners, 67.4 % of whom had unprotected sex. Having ≥2 recent sex partners was associated with being 35 years or older, male, living with friends or others, introduced to club drug use by non-regular sex partners, using methamphetamine recently, self-identified as gay/lesbian or bisexual, had sexual debut before 20 years old, and recently had sex under the influence of drugs. Having unprotected sex with non-regular partners in the past 30 days was associated with lower education levels, having sex to obtain drugs, and lower levels of HIV/AIDS knowledge. Club drug users should be targeted for intervention programs. Future research needs to identify other protective and risk factors for sexual risk behaviors and design interventions to reduce club drug use and associated sexual risk behaviors.

The clinical toxicology of γ-hydroxybutyrate, γ-butyrolactone and 1,4-butanediol

INTRODUCTION

Gamma-hydroxybutyrate (GHB) and its precursors, gamma-butyrolactone (GBL) and 1,4-butanediol (1,4-BD), are drugs of abuse which act primarily as central nervous system (CNS) depressants. In recent years, the rising recreational use of these drugs has led to an increasing burden upon health care providers. Understanding their toxicity is therefore essential for the successful management of intoxicated patients. We review the epidemiology, mechanisms of toxicity, toxicokinetics, clinical features, diagnosis, and management of poisoning due to GHB and its analogs and discuss the features and management of GHB withdrawal.

METHODS

OVID MEDLINE and ISI Web of Science databases were searched using the terms "GHB," "gamma-hydroxybutyrate," "gamma-hydroxybutyric acid," "4-hydroxybutanoic acid," "sodium oxybate," "gamma-butyrolactone," "GBL," "1,4-butanediol," and "1,4-BD" alone and in combination with the keywords "pharmacokinetics," "kinetics," "poisoning," "poison," "toxicity," "ingestion," "adverse effects," "overdose," and "intoxication." In addition, bibliographies of identified articles were screened for additional relevant studies including nonindexed reports. Non-peer-reviewed sources were also included: books, relevant newspaper reports, and applicable Internet resources. These searches produced 2059 nonduplicate citations of which 219 were considered relevant.

EPIDEMIOLOGY

There is limited information regarding statistical trends on world-wide use of GHB and its analogs. European data suggests that the use of GHB is generally low; however, there is some evidence of higher use among some sub-populations, settings, and geographical areas. In the United States of America, poison control center data have shown that enquiries regarding GHB have decreased between 2002 and 2010 suggesting a decline in use over this timeframe.

MECHANISMS OF ACTION

GHB is an endogenous neurotransmitter synthesized from glutamate with a high affinity for GHB-receptors, present on both on pre- and postsynaptic neurons, thereby inhibiting GABA release. In overdose, GHB acts both directly as a partial GABA(b) receptor agonist and indirectly through its metabolism to form GABA.

TOXICOKINETICS

GHB is rapidly absorbed by the oral route with peak blood concentrations typically occurring within 1 hour. It has a relatively small volume of distribution and is rapidly distributed across the blood-brain barrier. GHB is metabolized primarily in the liver and is eliminated rapidly with a reported 20-60 minute half-life. The majority of a dose is eliminated completely within 4-8 hours. The related chemicals, 1,4-butanediol and gamma butyrolactone, are metabolized endogenously to GHB. CLINICAL FEATURES OF POISONING: GHB produces CNS and respiratory depression of relatively short duration. Other commonly reported features include gastrointestinal upset, bradycardia, myoclonus, and hypothermia. Fatalities have been reported. MANAGEMENT OF POISONING: Supportive care is the mainstay of management with primary emphasis on respiratory and cardiovascular support. Airway protection, intubation, and/or assisted ventilation may be indicated for severe respiratory depression. Gastrointestinal decontamination is unlikely to be beneficial. Pharmacological intervention is rarely required for bradycardia; however, atropine administration may occasionally be warranted. WITHDRAWAL SYNDROME: Abstinence after chronic use may result in a withdrawal syndrome, which may persist for days in severe cases. Features include auditory and visual hallucinations, tremors, tachycardia, hypertension, sweating, anxiety, agitation, paranoia, insomnia, disorientation, confusion, and aggression/combativeness. Benzodiazepine administration appears to be the treatment of choice, with barbiturates, baclofen, or propofol as second line management options.

CONCLUSIONS

GHB poisoning can cause potentially life-threatening CNS and respiratory depression, requiring appropriate, symptom-directed supportive care to ensure complete recovery. Withdrawal from GHB may continue for up to 21 days and can be life-threatening, though treatment with benzodiazepines is usually effective.

Teenage toxins: recreational poisoning in the adolescent

Adolescents are experimenting with recreational drugs on a regular basis, particularly at social gatherings such as parties, raves and mass events. A combination of reduced fluid intake, physical activity and drug-induced hyperthermia leads to complications such as heat stroke, delirium and potentially death. The clinician needs to be aware of the variety of pharmacologically active substances available in the recreational marketplace in order to diagnose and manage these patients. Recreational misadventure, because of incorrect dosage or mixing multiple substances, is a common reason for teenagers presenting to hospital with toxidromes. Death from club drug overdose is more likely to be associated with suicidal intent, related risky behaviour and trauma, as well as the inherent toxicity of the drug itself. Although many teenagers are concerned about 'drink spiking' with club drugs, the most common agent causing drink spiking incidents is ethanol.

Reasons for not using ecstasy: a qualitative study of non-users, ex-light users and ex-moderate users

Background

Although ecstasy is often consumed in the electronic music scene, not everyone with the opportunity to use it chooses to do so. The objective of this study was to understand the reasons for non-use or the cessation of use, which could provide information for public health interventions.

Methods

A qualitative reference method was used. Our “snowball” sample group consisted of 53 people who were split into three subgroups: non-users (NU, n = 23), ex-light users (EX-L, n = 12) and ex-moderate users (EX-M, n = 18). Individual, semi-structured interviews were conducted, transcribed and subjected to content analysis with the aid of NVivo8.

Results

Adverse health effects and personal values were given as reasons for non-use in the three groups. Non-users (NU) and ex-light users (EX-L) provided reasons that included fear of possible effects as well as moral, family and religious objections. Ex-moderate users (EX-M) cited reasons related to health complications and concomitant withdrawal from the electronic music scene. However, most of the ex-moderate users did not rule out the possibility of future use.

Conclusions

Potential effects and undesirable consequences appear to guide the decisions within the different groups. Prevention might target these motivations. Individuals who have used ecstasy indicate that social and environmental factors are the most important factors.

Illicit drug use in the flemish nightlife scene between 2003 and 2009

AIMS

Given the importance of party people as innovators and early adaptors in the diffusion of substance use, and given the lack of longitudinal scope in studies of the nightlife scene, we explored changes in illicit drug use among young people participating in the nightlife scene in Flanders.

METHODS

A survey among party people selected at dance events, rock festivals and clubs was held in the summer of 2003 and repeated in 2005, 2007 and 2009. In total, 2,812 respondents filled in a questionnaire on the use of cannabis, ecstasy, cocaine, amphetamines, GHB and ketamine.

RESULTS

The results of the multiple logistic regression analyses show that in the group of frequent pub visitors, the predicting probability of cannabis use increased over time, while the gap in drug use between dance music lovers and non-lovers of dance music narrowed. For cocaine use during the last year, an increase was found related to the housing situation (alone or with parents) of respondents. While the odds of using ecstasy decreased over the years, the odds of using GHB increased.

CONCLUSION

We can conclude that monitoring emerging trends, which can be quickly observed in the nightlife scene, provides meaningful information for anticipating possible trends.

Gene expression changes in GABA(A) receptors and cognition following chronic ketamine administration in mice

Ketamine is a well-known anesthetic agent and a drug of abuse. Despite its widespread use and abuse, little is known about its long-term effects on the central nervous system. The present study was designed to evaluate the effect of long-term (1- and 3-month) ketamine administration on learning and memory and associated gene expression levels in the brain. The Morris water maze was used to assess spatial memory and gene expression changes were assayed using Affymetrix Genechips; a focus on the expression of GABA(A) receptors that mediate a tonic inhibition in the brain, was confirmed by quantitative real-time PCR and western blot. Compared with saline controls, there was a decline in learning and memory performance in the ketamine-treated mice. Genechip results showed that 110 genes were up-regulated and 136 genes were down-regulated. An ontology analysis revealed the most significant effects of ketamine were on GABA(A) receptors. In particular, there was a significant up-regulation of both mRNA and protein levels of the alpha 5 subunit (Gabra5) of the GABA(A) receptors in the prefrontal cortex. In conclusion, chronic exposure to ketamine impairs working memory in mice, which may be explained at least partly by up-regulation of Gabra5 subunits in the prefrontal cortex.

To use or not to use: an update on licit and illicit ketamine use

Ketamine, a derivative of phencyclidine that was developed in the 1960s, is an anesthetic and analgesic with hallucinogenic effects. In this paper, the pharmacological and toxicological effects of ketamine are briefly reviewed. Ketamine possesses a wide safety margin but such a therapeutic benefit is somewhat offset by its emergence phenomenon (mind-body dissociation and delirium) and hallucinogenic effects. The increasing abuse of ketamine, initially predominantly in recreational scenes to experience a “k-hole” and other hallucinatory effects but more recently also as a drug abused during the workday or at home, has further pushed governments to confine its usage in many countries. Recently, urinary tract dysfunction has been associated with long-term ketamine use. In some long-term ketamine users, such damage can be irreversible and could result in renal failure and dialysis. Although ketamine has not yet been scheduled in the United Nations Conventions, previous studies using different assessment parameters to score the overall harms of drugs indicated that ketamine may cause more harm than some of the United Nations scheduled drugs. Some countries in Southeast and East Asia have reported an escalating situation of ketamine abuse. Dependence, lower urinary tract dysfunction, and sexual impulse or violence were the most notable among the ketamine-associated symptoms in these countries. These results implied that the danger of ketamine may have been underestimated previously. Therefore, the severity levels of the ketamine-associated problems should be scrutinized more carefully and objectively. To prevent ketamine from being improperly used and evolving into an epidemic, a thorough survey on the prevalence and characteristics of illicit ketamine use is imperative so that suitable policy and measures can be taken. On the other hand, recent findings that ketamine could be useful for treating major depressive disorder has given this old drug a new impetus. If ketamine is indeed a remedy for treating depression, more research on the risks and benefits of its clinical use will be indispensable.

Prevalence and factors associated with Ecstasy use among college undergraduates in north of Iran-2005

We conducted a cross sectional study of 3958 college students in north of Iran in 2005 with an anonymous questionnaire that was adapted from the questionnaires used in "Monitoring the future". Three thousand seven hundred students responded (93.5%). Lifetime prevalence use of ecstasy, opium and cannabis was 4.3%, 2.7% and 2.4% respectively. The prevalence of current cigarette smoking was 19.5%. After the logistic regression, the factors influencing ecstasy use were use of other illicit drugs, alcohol and cigarette smoking (P<0.000), widow or divorced (ρ=0.007) and higher educational background of mother (ρ=0.019).

Contextual profiles of young adult ecstasy users: A multisite study

These analyses assess contextual profiles of 612 young adult ecstasy users, 18-30 years of age, from St. Louis (USA), Miami (USA) and Sydney (Australia). Bivariate analyses revealed different contextual factors influencing ecstasy use. Friends were the most common sources of ecstasy at all sites and most used with friends. St. Louis and Miami use mostly occurred in residences, whereas in Sydney use was mostly at clubs, bars or restaurants. Ecstasy consumption at public places and in cars, trains or ferries was significantly higher in Miami (89% and 77%) than in St. Louis (67% and 65%) and Sydney (67% and 61%). At all sites, simultaneous use of LSD/mushroom and nitrous oxide with ecstasy was common; concurrent amphetamines predominated in Sydney and heroin/opiates in St. Louis Contextual factors influencing ecstasy use among young adults vary by geographic region. Their inclusion may help tailor effective prevention programs to reduce or ameliorate ecstasy use.

Illicit ketamine induced frequency of micturition in a young Malay woman

ISSUES

The growing use of illicit ketamine among young adults poses a public health concern in Malaysia. In contrast to medical use of ketamine, illicit use has been reported to produce adverse effects on the urinary tract and, in particular the bladder. APPROACH AND KEY FINDINGS: This case report describes a young Malay woman who developed severe bladder symptoms (urinary frequency) after consuming illicit ketamine. A history of illicit ketamine use was initially missed, and she was consequently diagnosed and treated for a urinary tract infection. Her symptoms persisted despite several courses of antibiotics. The patient was subsequently referred to an urologist where cystoscopic examination and biopsy of the bladder found changes consistent with interstitial cystitis. This was despite the absence of haematuria. Renal function was normal.

IMPLICATION

The patient's ketamine use was the most likely cause for the urinary symptoms and bladder changes.

CONCLUSION

Illicit ketamine use may lead to severe urinary tract problems that can be irreversible even after ketamine has ceased. Early diagnosis is critical although difficult when ketamine use is not divulged during the consultation with the physician. Physician consideration of this new clinical entity is important, particularly in cases where the symptoms do not resolve with usual treatment.

Consistency and change in club drug use by sexual minority men in New York City, 2002 to 2007

We used repeated cross-sectional data from intercept surveys conducted annually at lesbian, gay, and bisexual community events to investigate trends in club drug use in sexual minority men (N = 6489) in New York City from 2002 to 2007. Recent use of ecstasy, ketamine, and γ-hydroxybutyrate decreased significantly. Crystal methamphetamine use initially increased but then decreased. Use of cocaine and amyl nitrates remained consistent. A greater number of HIV-positive (vs HIV-negative) men reported recent drug use across years. Downward trends in drug use in this population mirror trends in other groups.

The involvement of gamma-hydroxybutyrate in reported sexual assaults: a systematic review

Over the past few years gamma-hydroxybutyrate (GHB) has generated widespread media interest as a possible 'date rape drug'. Our goal was to examine the extent to which GHB is associated with drug-facilitated sexual assaults. Literature was searched systematically and 11 studies, published between 1961 and June 30, 2009, were identified dealing specifically with the role of GHB in sexual assaults. GHB was detected in 0.2-4.4% of reported sexual assaults. The results demonstrate that a wide range of drugs may be present in cases of sexual assault, and many of them are much more frequent than GHB. Our results do not support the widespread labelling of GHB as a date rape drug as the prevalence of GHB is much lower than of other substances used in sexual assaults. On the other hand, however, the possible risk of GHB in this regard should not be neglected. Nevertheless, over-sensitive and sensation seeking media reports focusing on the association of sex crime and GHB might be counterproductive and misleading as they turn the attention away from other substances that are often used in sexual assaults.

Behavioral effects of gamma-hydroxybutyrate in humans

Despite the therapeutic use and abuse potential of gamma-hydroxybutyrate (GHB or Xyrem), relatively few studies have examined the behavioral effects of GHB in humans under controlled laboratory conditions. Thus, this eight-session study examined in 10 non-substance-abusing volunteers the behavioral effects of GHB at each of the following doses: 0, 0.32, 0.56, 0.75, 1.0, 1.8, 2.4, 3.2 g/70 kg, orally. Order of dose testing was random, except that the first two participants received active doses in ascending order and 2.4 g/70 kg was always tested before 3.2 g/70 kg. Before drug administration and at several postdrug time points, self-report, observer report, physiological, and psychomotor performance measures were obtained. Analyses based on area under the curve showed that GHB produced dose-related increases in subjective ratings of sedative-like, stimulant-like, positive mood, and dissociative effects, but no changes in psychomotor performance measures or blood pressure. Analyses based on peak effects generally showed dose-related increases in ratings indicating sedative-like, dissociative, and drug liking, although some measures showed U-shaped dose-related changes. These initial findings suggest that GHB at doses of 0.32-3.2 g/70 kg produces dissociative, sedating and some stimulant-like effects in humans without a history of sedative abuse.

Gamma-hydroxybutyrate does not maintain self-administration but induces conditioned place preference when injected in the ventral tegmental area

Gamma-hydroxybutyric acid (GHB) is an endogenous brain substance that has diverse neuropharmacological actions, including rewarding properties in different animal species and in humans. As other drugs of abuse, GHB affects the firing of ventral tegmental neurons (VTA) in anaesthetized animals and hyperpolarizes dopaminergic neurons in VTA slices. However, no direct behavioural data on the effects of GHB applied in the VTA or in the target regions of its dopaminergic neurons, e.g. the nucleus accumbens (NAc), are available. Here, we investigated the effects of various doses of intravenous GHB in maintaining self-administration (from 0.001 to 10 mg/kg per infusion), and its ability to induce conditioned place preference (CPP) in rats when given orally (175-350 mg/kg) or injected directly either in the VTA or NAc (from 10 to 300 microg/0.5 microl per side). Our results indicate that while only 0.01 mg/kg per infusion GHB maintained self-administration, although not on every test day, 350 mg/kg GHB given orally induced CPP. CPP was also observed when GHB was injected in the VTA (30-100 microg/0.5 microl per side) but not in the NAc. Together with recent in-vitro findings, these results suggest that the rewarding properties of GHB mainly occur via disinhibition of VTA dopaminergic neurons.