Dopaminergic network differences in human impulsivity

Dopamine (DA) has long been implicated in impulsivity, but the precise mechanisms linking human variability in DA signaling to differences in impulsive traits remain largely unknown. By using a dual-scan positron emission tomography approach in healthy human volunteers with amphetamine and the D2/D3 ligand [18F]fallypride, we found that higher levels of trait impulsivity were predicted by diminished midbrain D2/D3 autoreceptor binding and greater amphetamine-induced DA release in the striatum, which was in turn associated with stimulant craving. Path analysis confirmed that the impact of decreased midbrain D2/D3 autoreceptor availability on trait impulsivity is mediated in part through its effect on stimulated striatal DA release.

Methamphetamine causes microglial activation in the brains of human abusers

Methamphetamine is a popular addictive drug whose use is associated with multiple neuropsychiatric adverse events and toxic to the dopaminergic and serotonergic systems of the brain. Methamphetamine-induced neuropathology is associated with increased expression of microglial cells that are thought to participate in either pro-toxic or protective mechanisms in the brain. Although reactive microgliosis has been observed in animal models of methamphetamine neurotoxicity, no study has reported on the status of microglial activation in human methamphetamine abusers. The present study reports on 12 abstinent methamphetamine abusers and 12 age-, gender-, and education-matched control subjects who underwent positron emission tomography using a radiotracer for activated microglia, [(11)C](R)-(1-[2-chlorophenyl]-N-methyl-N-[1-methylpropyl]-3-isoquinoline carboxamide) ([(11)C](R)-PK11195). Compartment analysis was used to estimate quantitative levels of binding potentials of [(11)C](R)-PK11195 in brain regions with dopaminergic and/or serotonergic innervation. The mean levels of [(11)C](R)-PK11195 binding were higher in methamphetamine abusers than those in control subjects in all brain regions (>250% higher; p < 0.01 for all). In addition, the binding levels in the midbrain, striatum, thalamus, and orbitofrontal and insular cortices (p < 0.05) correlated inversely with the duration of methamphetamine abstinence. These results suggest that chronic self-administration of methamphetamine can cause reactive microgliosis in the brains of human methamphetamine abusers, a level of activation that appears to subside over longer periods of abstinence.

Neuropsychological function and delay discounting in methamphetamine-dependent individuals

RATIONALE

Methamphetamine (MA) dependence accounts for substantial neuropsychiatric morbidity. Furthermore, there is evidence in the literature of psychiatric and cognitive impairment in chronic users.

OBJECTIVES

This report compares the general psychiatric and cognitive functioning, including impulsive decision-making, of individuals dependent on MA and normal controls.

MATERIALS AND METHODS

Forty-one currently abstinent individuals in treatment for MA dependence and 41 controls participated. Controls were selected to minimize group differences in age and gender. MA users met DSM-IV criteria for MA dependence, had average daily use of 0.5 g/day (0.5-6 g/day), had been abstinent at least 2 weeks (2-24 weeks), and did not currently meet criteria for other Axis I psychiatric disorders. Psychiatric symptoms were rated on standardized scales. Cognitive function was assessed with a battery of standardized neuropsychological tests. Impulsivity was assessed using a delay discounting task, which measured preference for small, immediate, and large delayed rewards.

RESULTS

The MA group reported more psychiatric symptoms than controls, and was impaired relative to controls on the Babcock Story Recall-Delayed and the Rey Auditory Verbal Learning Test. MA-dependent subjects discounted delayed rewards more than controls, and this measure of impulsivity was correlated with memory impairment in the MA group but not in the controls.

CONCLUSIONS

MA-dependent individuals are more impulsive than controls, and this may be causally related to memory deficits but was unrelated to any other measure of psychiatric or cognitive impairment or any drug use history variable.

A diet promoting sugar dependency causes behavioral cross-sensitization to a low dose of amphetamine

Previous research in this laboratory has shown that a diet of intermittent excessive sugar consumption produces a state with neurochemical and behavioral similarities to drug dependency. The present study examined whether female rats on various regimens of sugar access would show behavioral cross-sensitization to a low dose of amphetamine. After a 30-min baseline measure of locomotor activity (day 0), animals were maintained on a cyclic diet of 12-h deprivation followed by 12-h access to 10% sucrose solution and chow pellets (12 h access starting 4 h after onset of the dark period) for 21 days. Locomotor activity was measured again for 30 min at the beginning of days 1 and 21 of sugar access. Beginning on day 22, all rats were maintained on ad libitum chow. Nine days later locomotor activity was measured in response to a single low dose of amphetamine (0.5 mg/kg). The animals that had experienced cyclic sucrose and chow were hyperactive in response to amphetamine compared with four control groups (ad libitum 10% sucrose and chow followed by amphetamine injection, cyclic chow followed by amphetamine injection, ad libitum chow with amphetamine, or cyclic 10% sucrose and chow with a saline injection). These results suggest that a diet comprised of alternating deprivation and access to a sugar solution and chow produces bingeing on sugar that leads to a long lasting state of increased sensitivity to amphetamine, possibly due to a lasting alteration in the dopamine system.

Cognitive performance of current methamphetamine and cocaine abusers

Forty currently using methamphetamine (MA) abusers, 40 currently using cocaine (COC) abusers, and 80 comparison participants who did not use psychostimulants received a cognitive battery and questionnaires covering medical history and stimulant use patterns. Forty comparison participants were matched to the 40 MA users on age, education, ethnicity, and gender. The other 40 comparison participants were matched to the cocaine users on the same variables. This design was chosen because there were significant differences in age and ethnicity between COC and MA users that precluded a direct comparison between the groups. The COC group was older and predominantly African American compared to the predominantly Caucasian MA group. When compared to their matched non-using control groups, both MA and COC abusers were impaired on cognitive measures, but the type and degree of impairments were somewhat different.

Will the methamphetamine problem go away?

Methamphetamine use has clearly reached epidemic proportions in large parts of the western and midwestern US. Because of the regional specificity of methamphetamine use, there is speculation that it may be a temporary problem and not a long-term public health problem. Unfortunately there are a number of factors that suggest that significant methamphetamine problems may persist or even expand. For this reason, it is important that federal law enforcement, prevention, research and treatment agencies prepare strategies to address the likelihood of this persisting problem. This article reviews the issues concerning the future of the methamphetamine problem in the US and provides some recommendations for setting priorities to address the problem.

Elevated impulsivity and impaired decision-making cognition in heavy users of MDMA ("Ecstasy")

RATIONALE

In animal studies, the common club drug 3,4-methylendioxymethamphetamine (MDMA, "Ecstasy") consistently caused a prolonged loss of presynaptic serotonergic neurons, and evidence suggests that MDMA consumption may also affect the human serotonergic system. Serotonin (5-HT) has been implicated in the regulation of impulsivity and such executive functions as decision-making cognition. In fact, MDMA users have shown elevated impulsivity in two studies, but little is known about decision making in drug-free MDMA consumers.

OBJECTIVE

The aim of this study was to examine the cognitive neurotoxicity of MDMA with regard to behavioral impulsivity and decision-making cognition.

METHODS

Nineteen male, abstinent, heavy MDMA users; 19 male, abstinent cannabis users; and 19 male, drug-naïve controls were examined with the Matching Familiar Figures Test (MFFT) as well as with a Go/No-Go Task (GNG) for impulsivity and with a Gambling Task (GT) for executive functioning.

RESULTS

MDMA users showed significantly elevated impulsivity in the MFFT Impulsivity score (I-score), but not in commission errors of the GNG, compared with controls. Cannabis users did not yield altered impulsivity compared with controls. In the GT, MDMA users performed significantly worse than cannabis consumers and controls, whereas cannabis users exhibited the same decision-making capacity as controls. In addition, the I-score as well as the decision-making performance was correlated with measures of MDMA intake. The I-score and the decision-making performance were also correlated.

CONCLUSION

These results suggest that heavy use of MDMA may elevate behavioral impulsivity and impair decision-making cognition possibly mediated by a selective impairment of the 5-HT system.

MDMA use and neurocognition: a meta-analytic review

RATIONALE

To determine the association between MDMA misuse and neurocognition using meta-analysis.

OBJECTIVE

Separate analyses were conducted based on two sets of inclusion/exclusion criteria. A relatively stringent set required that the subjects be matched on important moderator variables, whereas the other did not. The study participants' performance in the following neurocognitive domains was reviewed: attention/concentration, verbal and nonverbal learning and memory, psychomotor speed and executive systems functioning.

RESULTS

In the 11 studies meeting the relatively stringent inclusion/exclusion criteria for this review, MDMA use was associated with neurocognitive deficits in each domain. Similarly, in the 23 studies meeting the relatively lenient inclusion/exclusion criteria for this review, MDMA use was associated with neurocognitive deficits in each domain. Small to medium effect sizes were generally observed. A comparison of the effect sizes across the two sets of analyses did not reveal significant differences.

CONCLUSIONS

The findings from this review reveal that MDMA use is associated with neurocognitive deficits. The implications of these findings are discussed.

Association analysis of the DRD4 and COMT genes in methamphetamine abuse

We analyzed two polymorphisms in genes encoding proteins of the dopamine system, the Val158Met polymorphism in the catechol-O-methyltransferase gene and the 120-bp VNTR polymorphism in the promoter of the dopamine D4 receptor gene for association with methamphetamine abuse. We used a case/control design with 416 methamphetamine abusing subjects and 435 normal controls. All subjects were Han Chinese from Taiwan. We found an excess of the high activity Val158 allele in the methamphetamine abuser group, consistent with several previous reports of association of this allele with drug abuse. The 120-bp VNTR polymorphism in the promoter of the dopamine D4 receptor gene itself did not show significant association with methamphetamine abuse. However, analysis of the 120-bp VNTR polymorphism and the exon 3 VNTR in the dopamine D4 receptor as a haplotype showed significant association with methamphetamine abuse, which gave an empirical P value 0.0034 for a heterogeneity model. Moreover, there were significant interactive effects between polymorphisms in the catechol-O-methyltransferase and dopamine D4 genes. The evidence of interaction between COMT 158 Val/Met and DRD4 48-bp VNTR polymorphisms (P = 0.0003, OR = 1.45, 95% CI: 1.148-1.77), and between COMT 158 Val/Met and DRD4 120 bp promoter polymorphisms (P = 0.01, OR = 1.10, 95% CI: 1.10-1.18) were significant but the latter was weak. We conclude that genetic variation in the dopamine system may encode an additive effect on risk of becoming a methamphetamine abuser.

Methamphetamine abuse and rhabdomyolysis in the ED: a 5-year study

Patients with methamphetamine toxicity are presenting in greater numbers each year to emergency departments (ED) in the US. These patients are frequently agitated, violent, and often require physical and chemical restraint. The incidence and risk of rhabdomyolysis in this subpopulation is unknown. We conducted a 5-year retrospective review of all ED patients who received the final diagnosis of rhabdomyolysis. Patients with toxicology screens positive for methamphetamine were identified, and demographics, laboratory results, resource utilization, disposition, and outcome were compared to the remaining patients. Of the total 367 patients identified, 166 (43%) were toxicology positive for methamphetamine. Methamphetamine patients differed significantly from nonmethamphetamine patients with regard to demographics and hospital utilization. Methamphetamine patients had significantly higher mean initial creatine phosphokinase (CK), 12,439 U/L versus 5,678 U/L (P = 0.02), and lower mean peak CK, 16,827 U/L versus 19,426 U/L (P = 0.03). The development of acute renal failure was not significantly different between the 2 groups. There were 16 total deaths in the study population, 11 from concomitant infection/sepsis. An association between methamphetamine abuse and rhabdomyolysis may exist, and CK should be measured in the ED as a screen for potential muscle injury in this subpopulation. Patients with rhabdomyolysis with an unclear cause should be screened for methamphetamine or other illicit drugs.

Neuroimaging research in human MDMA users: a review

RATIONALE

Determining whether, under what circumstances, and to what extent 3,4-methylenedioxymethamphetamine (MDMA) exposure produces chronic changes in human brain function is a critical public health issue. MDMA is a widely used recreational drug commonly sold as "Ecstasy". Because findings from the animal literature have indicated that specific dosage regimens of MDMA can produce long-lasting alterations in serotonergic function, existing studies of MDMA effects in humans have examined brain serotonin (5-HT) transporters (5-HTT) and receptors or have examined brain structures or functions potentially affected by MDMA.

OBJECTIVES

The objectives of this review are to provide a background for interpreting human MDMA neuroimaging research, to examine existing neuroimaging data regarding the rationale for and limitations to human MDMA research, and to provide suggestions for improving the design and interpretation of future neuroimaging approaches.

RESULTS

Of the existing neuroimaging studies in human MDMA users, few experimental designs have been replicated across different research groups. Only investigations employing nuclear imaging methods to assay brain 5-HTT levels have been replicated across methods and research laboratories. These studies have found reduced levels of the 5-HTT in recently abstinent MDMA users with some evidence for normalization of 5-HTT levels with prolonged abstinence. However, the sensitivity of these methods is unknown.

CONCLUSIONS

The current state of neuroimaging in human MDMA users does not permit conclusions regarding the long-term effects of MDMA exposure. Future study designs might benefit from improved sample homogeneity, increased length of MDMA abstinence, longitudinal study design, test-retest measures, serotonergic specificity, and multimodal approaches.

Epidemiology and public health Consequences of methamphetamine use in California's Central Valley

Methamphetamine use is an increasingly serious public health problem in California and other parts of the country. Despite sensationalistic media attention, however, very little is known about users of this clandestinely consumed drug. Employing methods known as Rapid Assessment and Response, the authors describe the epidemiology and public health implications of methamphetamine use in California's Central Valley, with a focus on Sacramento, which many social indicators suggest has been more severely affected by methamphetamine than any city in the nation. Data sources for this report include interviews with drug users, statistical reports, epidemiologic studies, and local informed expert opinion. In their social demography, methamphetamine users in the Central Valley are in marked contrast to those of coastal cities such as Seattle and San Francisco, being largely heterosexual, and of mixed racial/ethnic heritage. Three-quarters or more initiate their use of the drug while still in their teens, with more than a quarter beginning use before the age of 15. Many of these rapidly gravitate to regular use, and continue using well into their thirties. Methamphetamine users are at much higher risk of infection with HIV than opiate users, particularly if they inject. Partly because methamphetamine enhances libido, users of the drug typically also have many more sexual partners. Not surprisingly, data indicate that methamphetamine users are more likely than heroin users to be HIV-infected. Methamphetamine appears to be less of a street drug than heroin, complicating efforts at street outreach. However, because it is typically used in social settings, a social or diffusion approach to HIV prevention might be particularly promising.

Use ecology and drug use motivations of methamphetamine users admitted to substance abuse treatment facilities in Los Angeles: an emerging profile

Who are methamphetamine (MA) users and what are the circumstances that surround their drug use? This article provides a foundation for future ethnographic studies and collaborative clinician-researcher assessments of MA use by describing use ecology and drug use motivation for 260 MA users admitted to treatment at public Los Angeles County facilities in 1996. Use ecology data include MA varieties and street names, first introductions to use, drug use histories, access, selling and manufacturing, routes of administration, unwanted results of use, and participants' use behavior in the year before the 1996 treatment. Use motivation data describe clients using MA as a substitute for other stimulants; to cope with mental distress; to stay awake; to enhance sexual experience; and to lose weight. Qualitative case studies illustrate the findings and demonstrate the complex inter-relations of society, culture, psyche and soma shaping MA use over time.

Association study between brain-derived neurotrophic factor gene polymorphisms and methamphetamine abusers in Japan

Several lines of evidence suggest that genetic factors might contribute to drug abuse vulnerability. Recent genomic scans for association demonstrated that the brain-derived neurotrophic factor (BDNF) gene was associated with drug abuse vulnerability. In this study, we analyzed association of two BDNF gene single nucleotide polymorphisms (SNPs), 132C > T (C270T named formerly) in the noncoding region of exon V and 196G > A (val66met) in the coding region of exon XIIIA, with methamphetamine (MAP) abuse in Japan. No significant differences were found in the frequency of the genotype or allele in these two SNPs between MAP abusers and controls (132C > T in exon V: genotype, P = 0.586, allele, P = 0.594; 196G > A (val66met) in exon XIIIA: genotype, P = 0.889, allele, P = 0.713). Furthermore, there was no difference between clinical parameters (e.g., prognosis psychosis, spontaneous relapse, or poly-substance abuse) and the two SNPs of BDNF gene. These results suggest that the two SNPs (132C > T in exon V and 196G > A (val66met) in exon XIIIA) of the BDNF gene may not be associated with Japanese MAP abusers. This article contains supplementary material, which may be viewed at the American Journal of Medical Genetics website at http://www.interscience.wiley.com/jpages/0148-7299:1/suppmat/index.html.

Cognitive deficits among methamphetamine users with attention deficit hyperactivity disorder symptomatology

Understanding the association between attention deficit hyperactivity disorder (ADHD) and substance abuse, specifically methamphetamine (MA) abuse, is challenging, partly because little is known about the specific constellation of cognitive impairments produced by MA. The present investigation serves to address this relationship by comparing the cognitive performance of MA abusers with ADHD symptomatology (n = 28) and MA abusers without ADHD symptomatology (n = 41) on tests of attention, memory and general intellectual functioning, executive functioning, problem solving, verbal fluency, and abstract thinking. Both MA samples had deficiencies in measures of memory and learning function, psychomotor speed and abstract thinking when compared to a control group (n = 40). Additional deficits were noted on tasks involving executive functioning, attention, and general intellectual functioning in MA abusers with ADHD symptomatology. The preliminary data suggests that executive function deficits and some of the symptoms associated with long-term MA use may be due to the fact that a large proportion of MA addicts had ADHD symptomatology as children.

Methamphetamine-induced striatal dopamine release, behavior changes and neurotoxicity in BALB/c mice

The behaviors associated with the neurotoxic effects of methamphetamine were evaluated in BALB/c mice. Hyperthermia and behavioral observations were measured 60 min after each subcutaneous injection of methamphetamine (4x4 or 8 mg/kg) or saline, each given 2 h apart. The behavioral observations included stereotyped behaviors, incidence of hemorrhage in breast, salivation and self-injurious behavior (SIB). Repeated administration of methamphetamine produced these behavioral changes and hyperthermia, but resulted in hypothermia by the final injection (8 mg/kg). In addition, the methamphetamine treatment induced a long-lasting dopamine depletion of similar magnitude in the 4 and 8 mg/kg-treated animals. In a time course study striatal monoamine levels were measured 60 min after each injection of these doses. The first and second injections of methamphetamine (8 mg/kg) produced a drastic increase in striatal 3-methoxytyramine; this failed to occur after the third or fourth injection of the same dose. In contrast, 4 mg/kg of methamphetamine also produced an increase in 3-methoxytyramine after the second and third injections of the drug and, in this case, these were maintained for the duration of the treatment. Striatal 3, 4-dihydroxyphenylacetic acid levels also drastically decreased following both doses of methamphetamine, suggesting inhibition of monoamine oxidase in striatum. Moreover, a single injection of methamphetamine increased striatal 2,3-dihydroxybenzoic acid formation. These results suggest that the incidence of hyperthermia, SIB and striatal dopamine neurotoxicity are closely linked to striatal dopamine release and inhibition of monoamine oxidase produced by methamphetamine in BALB/c mice.

Effects of acute topiramate dosing on methamphetamine-induced subjective mood

Clinical studies have shown that topiramate, a sulphamate-substituted fructopyranose derivative, might be an efficacious treatment for alcohol dependence, smoking cessation within an alcohol-dependent population, and cocaine dependence. Mechanistically, topiramate's therapeutic effects have been hypothesized to be due to inhibition of cortico-mesolimbic dopamine function, the primary substrate that governs the acquisition, maintenance, and reinstatement of goal-directed behaviour towards seeking abused drugs. Predicated on this hypothesis, we tested in 10 methamphetamine-dependent individuals (three females) whether low- or high-dose (15 or 30 mg i.v.) methamphetamine-induced positive subjective effects and reinforcement can be antagonized by low- or high-dose (100 or 200 mg orally) topiramate using a placebo-controlled, cross-over, factorial design. Methamphetamine administration was associated with orderly, prototypical, and significant increases on measures of stimulation, euphoria, craving, and reinforcement; however, some dysphoric symptoms also emerged. Topiramate alone showed a non-significant trend towards mild reductions in positive mood and reinforcement; yet topiramate appeared to accentuate the appreciation of methamphetamine-induced stimulation and euphoria significantly, but not craving or reinforcement. The experimental combination of topiramate and methamphetamine appeared to be safe and well tolerated, with few adverse events. Acute dosing with up to 200 mg topiramate appears to enhance, rather than attenuate, the positive subjective effects of methamphetamine. Perhaps this indicates a partial inhibition of methamphetamine's reinforcing effects. Thus, testing chronically administered or higher doses, or both, of topiramate would be necessary to determine conclusively whether or not it can attenuate the positive subjective and reinforcing effects of methamphetamine.

The availability and portrayal of stimulants over the Internet

PURPOSE

To quantify the online availability and portrayal of amphetamine-class prescription stimulants with a focus on those medications commonly prescribed to and abused by adolescents.

METHOD

The Google search engine was used in searches to assess the frequency of web sites offering to sell controlled stimulants (retail sites) or web sites that directly linked to retail sites (portal sites). In addition separate searches were used to evaluate the portrayal of controlled prescription stimulants by the initial 20 web sites returned by Google. Retail and portal web site frequency was collected for each search. For searches measuring the portrayal of stimulants, web pages were categorized as pro-use, anti-misuse, neutral or other, based on set criteria.

RESULTS

Sites offering to sell stimulants without a prescription were found for nearly all search terms. Across all searches, the Schedule III stimulants indicated for the treatment of obesity returned more sites offering to sell stimulants without a prescription than Schedule II stimulants indicated for the treatment of attention-deficit hyperactivity disorder (ADHD). Internet site portrayal of each stimulant varied; however sites that contained "methamphetamine" often included anti-misuse information.

CONCLUSIONS

The apparent availability of stimulants over the Internet without a prescription indicates the potential for a significant public health problem. The extent to which teens are obtaining these drugs via the Internet remains unclear, but clinicians must be aware of the potential for abuse, concomitant prescription use issues, illicit sources, and diversion of these medications, which can be highly addictive. Education of consumers and physicians as well as further governmental interventions are needed to limit the potential scope of this problem.

Dopamine receptor D3 genetic polymorphism (rs6280TC) is associated with rates of cognitive impairment in methamphetamine-dependent men with HIV: preliminary findings

Macrophages are one of HIV-1's principal targets and chiefly responsible for translocating HIV into the central nervous system (CNS). Previous research suggested an increase in macrophages being infected by HIV in the presence of methamphetamine (METH) or increased extracellular dopamine (DA). Experimental studies indicate that this is mediated by DA receptors, including DA receptor D3 (DRD3), which is expressed in macrophages. A single nucleotide polymorphism (SNP) of the DRD3 gene (rs6280TC) modulates its dopamine binding affinity, resulting in the possibility that inheriting a variant of this SNP increases macrophage susceptibility to HIV infection in the presence of METH and DA, particularly in the CNS where METH is sequestered, leading to cognitive impairment (CI). Thus, we conducted a retrospective clinical investigation to evaluate whether rs6280TC is associated with CI among HIV-positive METH users. We stratified 310 males by HIV serostatus (HIV-positive, -negative) and METH dependence (METH-positive, -negative) and then by rs6280TC genotype (CC, CT, and TT). Genotypic groups within each of four HIV/METH groups were compared for rates of CI. We hypothesized that only HIV-positive/METH-positive carriers of the C allele, which increases the DRD3's binding to DA, would be more likely to develop CI. Cochran-Armitage test for trends in proportions yielded significant (p < 0.05) association between three genotypes and impairment rates in the hypothesized order, but only among HIV-positive/METH-positive subjects. The results also confirmed that C allele carriers (CC and CT, 53.3%) in this group had higher impairment rates (p = 0.05) than TT carriers (33.3%). These findings support the theory that rs6280TC influences the frequency of CI in HIV-positive/METH-positive males.

Maternal separation fails to render animals more susceptible to methamphetamine-induced conditioned place preference

The maternal separation (MS) paradigm is an animal model that has been successfully used to study the long term effects of child abuse and neglect. Experiments showed that animals subjected to trauma and stress early in life display behavioural, endocrinological and growth factor abnormalities at a later stage in life, results that mirrored clinical conditions. It is apparent that adverse events early in life may affect the development and maturation of the brain negatively. The purpose of the present study was to investigate whether the abnormal brain development occurring in separated animals would also enhance the development of a preference for psychostimulant drug usage. Rats were subjected to maternal deprivation and further exposed to methamphetamine-induced conditioned place preference (CPP) which primarily measures drug reward (ventral striatum) learning and memory. Apomorphine-induced locomotor activity was also assessed to investigate the effects of methamphetamine on the dorsal (primarily locomotor activity) striatal dopaminergic system. We found that four consecutive injections of methamphetamine resulted in CPP behaviour 24 h after the 4th injection. A further four injections yielded similar CPP results and this effect lasted for at least 7 days until the third CPP assessment. These animals also had decreased ACTH and corticosterone secretions, but the prolactin levels were increased. Prior exposure to maternal separation did not have any effect on the CPP test. The ACTH and corticosterone secretions were also similarly reduced. However maternal separation decreased the release of prolactin and this reduction was not evident in the separated group that received methamphetamine. There was no significant difference in the apomorphine-induced locomotor activity of normally reared animals whether they received methamphetamine or saline. Interestingly there was a significant difference in locomotor activity between the two groups of animals that were subjected to maternal deprivation. The separated animals that received methamphetamine displayed markedly reduced locomotor activity upon apomorphine administration when compared to those that were treated with saline. Taken together, we conclude that maternal deprivation differentially influences dorsal and ventral striatal regions implicating dopaminergic mechanisms.

Club drug use in Germany

In this paper the epidemiology of club drug use in Germany, including the use of 3,4-methylendioxy-N-methamphetamine (MDMA) known as 'ecstasy' and related substances such as speed, amphetamines, hallucinogens, and cannabis is described on the basis of five different surveys. Two of them are representative household surveys to monitor the licit and illicit drug use behavior of the German population. The third one is a longitudinal study aimed at exploring comorbidity and posited risk and protective factors in adolescents and young adults with specific emphasis on substance use-related disorders. Since ecstasy seemed to be associated with a new music culture of the '90s called "techno," two studies investigating the relationship of using ecstasy and related substances in the techno party scene are additionally presented. The question of the clinical impact of using ecstasy and related substances is raised in terms of substance use-related and mental disorders associated with the use of ecstasy. Finally, the motivation for using and stopping the use of ecstasy is addressed. It is shown that ecstasy has reached the second place (after cannabis) in illegal drug preferences of adolescents and young adults in Germany. Evidence is found that ecstasy use as well as ecstasy use-related disorders such as "abuse" and "dependence" are of a transient, "youth-limited" nature.

The relationship between impulsivity and methamphetamine use severity in a community sample

BACKGROUND

Abuse of psychostimulants, including methamphetamine (MA), has been linked to heightened impulsivity. While previous research has demonstrated differences in impulsivity between MA users and non-substance users, less is known about variability in impulsivity within MA users and whether the severity of MA use related problems predicts impulsivity within individuals who regularly use MA. This study aims to elucidate the relationship between impulsivity and MA use severity.

METHOD

Non-treatment seeking individuals who reported regular MA use (n = 177) completed an impulsivity battery comprising self-report and behavioral measures. A structural equation modeling (SEM) approach was used to test the relationship between the MA use related problem severity and measures of impulsivity.

RESULTS

The final SEM model of impulsivity and MA use related problems (CFI = 0.897, RMSEA = 0.059, S-B scaled χ2 [260,n = 103] = 406.86) revealed that greater MA use severity was associated with greater self-reported impulsiveness, but no relationship was found between MA use severity and behavioral measures of impulsivity.

CONCLUSIONS

The current findings extend previous research by providing additional evidence that MA use is associated with increased self-reported impulsivity and highlights the importance of evaluating impulsivity as a multidimensional construct.

New Perspectives in the Studies on Endocannabinoid and Cannabis: A Role for the Endocannabinoid-Arachidonic Acid Pathway in Drug Reward and Long-Lasting Relapse to Drug Taking

Growing evidence on the involvement of cannabinoids in the rewarding effects of various kinds of drugs of abuse has suggested that not only the classical dopaminergic and opioidergic, but also the most recently established endocannabinoid system is implicated in the brain reward system. Furthermore, the interplay between the three systems has been shown to be an essential neural substrate underlying many aspects of drug addiction including craving and relapse. Relapse, the resumption of drug taking following a period of drug abstinence, is considered the main hurdle in treating drug addiction. Yet, little is known about its underlying mechanisms. The link between the endocannabinoid system and the arachidonic cascade is currently being clarified. While several findings have, indeed, shown the essential role of the endocannabinoid system in the reinstatement model, the endocannabinoid-arachidonic acid pathway may also be an important part in the neural machinery underlying relapse. This evidence may provide an alternative approach that will open a novel strategy in combating drug addiction.

School-Aged Outcomes following Prenatal Methamphetamine Exposure: 7.5-Year Follow-Up from the Infant Development, Environment, and Lifestyle Study

OBJECTIVE

To assess the relationship between prenatal methamphetamine exposure (PME) and behavior problems at age 7.5 years and the extent to which early adversity mediated this relationship.

STUDY DESIGN

The multicenter, longitudinal Infant Development, Environment, and Lifestyle study enrolled 412 mother-infant pairs at 4 sites. Methamphetamine-exposed participants (n = 204) were identified by self-report and/or gas chromatography/mass spectrometry confirmation of amphetamine and metabolites in infant meconium. Matched participants (n = 208) denied methamphetamine use and had a negative meconium screen. At the 7.5-year follow-up, 290 children with complete Child Behavior Checklist data and an early adversity index score were available for analysis (n = 146 exposed).

RESULTS

PME was significantly associated with an increased early adversity index score (P < .001) and with increased externalizing, rule-breaking behavior, and aggressive behavior (P < .05). Early adversity was also associated with higher externalizing behavior scores. Early adversity significantly mediated the relationship between PME and behavioral problems. After adjusting the mediation model for sex, prenatal tobacco, alcohol, and marijuana exposures, and study site, the association of PME with early adversity remained significant.

CONCLUSIONS

Though PME is associated with behavioral problems, early adversity may be a strong determinant of behavioral outcome for children exposed to methamphetamine in utero. Early adversity significantly mediated the relationship between PME and behavioral problems.

Neuropsychological function in ecstasy users: a study controlling for polydrug use

RATIONALE

A number of studies have compared ecstasy users to control groups on various measures of neuropsychological function in order to determine whether ecstasy use results in lasting cognitive deficits. However, few of those studies controlled adequately for non-ecstasy illicit drug use.

OBJECTIVE

The aim of this study was to investigate neuropsychological function in chronic ecstasy users while controlling for polydrug use.

METHODS

Neuropsychological function was assessed in four groups-30 current 3,4-methylenedioxymethamphetamine (MDMA) users with a little history of illicit drug use other than ecstasy and cannabis, 30 polydrug controls, 30 drug-naïve controls and 20 ex-MDMA users-using a battery of well-validated, computerized neuropsychological tests. The battery focused on memory, executive function, impulsivity and risk-taking.

RESULTS

Few differences were apparent between the groups, and on no measure were the current MDMA users impaired significantly relative to the polydrug controls. However, within the current MDMA users, questionnaire-measured impulsivity correlated with performance on a number of tests-a relationship that was not apparent in the controls.

CONCLUSIONS

These data highlight the complexity in understanding the current ecstasy literature and suggest that some individuals may be particularly vulnerable to cognitive impairment following chronic use. Although no differences were identified between the current MDMA users and the controls, trait impulsiveness was significantly correlated with impairment on a number of neuropsychological outcome measures in the MDMA users, but not in the controls. These data suggest that impulsive individuals may be those most at risk for the development of cognitive impairment following chronic ecstasy use.