Chronic methamphetamine increases fighting in mice

Depression-Associated Negr1 Gene-Deficiency Induces Alterations in the Monoaminergic Neurotransmission Enhancing Time-Dependent Sensitization to Amphetamine in Male Mice

In GWAS studies, the neural adhesion molecule encoding the neuronal growth regulator 1 (NEGR1) gene has been consistently linked with both depression and obesity. Although the linkage between NEGR1 and depression is the strongest, evidence also suggests the involvement of NEGR1 in a wide spectrum of psychiatric conditions. Here we show the expression of NEGR1 both in tyrosine- and tryptophan hydroxylase-positive cells. Negr1-/- mice show a time-dependent increase in behavioral sensitization to amphetamine associated with increased dopamine release in both the dorsal and ventral striatum. Upregulation of transcripts encoding dopamine and serotonin transporters and higher levels of several monoamines and their metabolites was evident in distinct brain areas of Negr1-/- mice. Chronic (23 days) escitalopram-induced reduction of serotonin and dopamine turnover is enhanced in Negr1-/- mice, and escitalopram rescued reduced weight of hippocampi in Negr1-/- mice. The current study is the first to show alterations in the brain monoaminergic systems in Negr1-deficient mice, suggesting that monoaminergic neural circuits contribute to both depressive and obesity-related phenotypes linked to the human NEGR1 gene.

Correlates of Aggression in Men With Methamphetamine Use Disorder: Childhood Trauma and Methamphetamine-Use Characteristics

BACKGROUND

Aggression is common among individuals with methamphetamine use disorder (MAUD) and constitutes a serious public health issue. The current study aimed to examine associations of methamphetamine-use characteristics and childhood trauma with aggression in men with MAUD.

METHODS

This cross-sectional study was conducted from December 2017 to August 2018. MAUD patients recruited from a compulsory drug rehabilitation center (n = 360) and healthy comparison subjects (n = 604) completed a survey that measured aggression and childhood trauma, using the Chinese version of Buss-Perry Aggressive Questionnaire (AQ-CV), and the short form of Childhood Trauma Questionnaire (CTQ-SF), respectively. MAUD patients also provided information on methamphetamine-use characteristics such as the age of MAUD onset, MAUD severity, and co-occurring alcohol use disorder (AUD) and tobacco use disorder (TUD) using standard or self-designed questionnaires. Chi-square tests and t-tests were used to compare childhood trauma and aggression between the MAUD and comparison groups. Multiple linear regressions were conducted to determine correlates of overall aggression and its five sub-scales among the MAUD group.

RESULTS

The MAUD group had higher childhood trauma and aggression scores than the comparison group. Within the MAUD group, age of MAUD onset, having severe MAUD, co-occurring AUD, co-occurring TUD, and childhood trauma were associated with overall aggression, with slightly different correlates found for its five sub-scales.

CONCLUSIONS

Our study shows a high level of childhood trauma and aggression in the MAUD group. Both methamphetamine-use characteristics (age of MAUD onset, severe MAUD, co-occurring AUD/TUD) and childhood trauma were associated with aggression in MAUD. Our findings provide useful information on potential risk factors for aggression and inform future longitudinal research to establish causal relationships between these factors and aggression to guide further prevention and treatment programs.

Prescribed aggression of fishes: Pharmaceuticals modify aggression in environmentally relevant concentrations

Traces of psychoactive substances have been found in freshwaters globally. Fish are chronically exposed to pollution at low concentrations. The changes of aggressive behaviour of chub (Squalius cephalus) were determined under the exposure to four psychoactive compounds (sertraline, citalopram, tramadol, methamphetamine) at environmentally relevant concentrations of 1 μg/L for 42 days. We tested whether (A) the behavioural effect of compounds varies within a single species; (B) there is a correlation between the individual brain concentration of the tested pollutants and fish aggression using the novel analysis of pollutants in brain; and (C) there is detectable threshold to effective pollutant concentration in brain. Behaviour and pollutant concentrations in brain were determined repeatedly (1st, 7th, 21st, 42nd and 56th days), including a two-week-long depuration period. The effect of particular compounds varied. Citalopram and methamphetamine generally increased the fish aggression, while no such effect was found after exposure to tramadol or sertraline. The longitudinal analysis showed an aggression increase after depuration, indicating the presence of withdrawal effects in methamphetamine- and tramadol-exposed fish. The analysis of pollutant concentration in brain revealed a positive linear relationship of citalopram concentration and aggression, while no such effect was detected for other compounds and/or their metabolites. Structural break analyses detected concentration thresholds of citalopram (1 and 3 ng/g) and sertraline (1000 ng/g) in brain tissue, from which a significant effect on behaviour was manifested. While the effect of sertraline was not detected using traditional approaches, there was a reduction in aggression after considering its threshold concentration in the brain. Our results suggest that pursuing the concentration threshold of psychoactive compounds can help to reduce false negative results and provide more realistic predictions on behavioural outcomes in freshwater environments, especially in the case of compounds with bioaccumulation potential such as sertraline.

Low-normal doses of methiopropamine induce aggressive behaviour in mice

Recreational use of illicit methiopropamine (MPA) is a public health concern because it produces neurochemical effects comparable with those induced by methamphetamine (METH). The present study investigated the effects of MPA on the expression of an aggressive behaviour. Eighty CD-1 male mice, after receiving intraperitoneal injection of saline, MPA (0.01-10 mg/kg), METH (0.01-10 mg/kg), or AMPH (0.01-10 mg/kg), once a week over a 5-week period, underwent the resident-intruder test and spontaneous locomotor activity measurement. Results showed that all psychostimulants induce aggressive behaviour even at low doses, with a dose-dependent increase and a time-dependent sensitisation. MPA potency was similar to METH and superior to AMPH. Therefore, MPA-induced aggressive behaviour may appear even at MPA dosages free of cardiovascular or other behavioural adverse effects and could become a non-intentional side effect that users experience after increasing and repeating MPA consumption.

Methamphetamine use and violence: Findings from a longitudinal birth cohort

AIMS

Evidence linking illicit methamphetamine use to violence perpetration and victimisation comes primarily from cross-sectional studies. These associations have not previously been studied in a longitudinal general population sample.

DESIGN

Longitudinal birth cohort.

SETTING AND PARTICIPANTS

General population sample (n = 1265) born in Christchurch, New Zealand in 1977.

MEASUREMENTS

Participants were asked at age 21, 25, 30 and 35 about their frequency of methamphetamine use, and violence perpetration or victimization since the last interview. Violence was measured both in general, and within intimate partner relationships in particular. Logistic generalised estimating equations modelled the association between methamphetamine exposure and violence outcomes within each age period, adjusting for confounding factors and time-dynamic covariate factors. The dose-response profiles were explored via associations between heaviest methamphetamine use frequency from age 18-35 and violence outcomes in that period.

FINDINGS

28 % of participants reported using methamphetamine at least once between age 18 and 35. Compared to no use, a history of any methamphetamine use in each age period was associated with an increased adjusted risk of violence perpetration (OR 1.60; 1.01-2.54), intimate partner violence perpetration (OR 1.55, 95 % CI 1.04-2.30), and violence victimization (OR 1.57, 1.00-2.47). Evidence for an association with intimate partner violence victimization was inconclusive (OR 1.09, 0.80-1.49). There was a dose response relationship whereby those who had used methamphetamine at least weekly at any time from age 18-35 had substantially elevated adjusted odds of violence involvement compared to people who used but less often, or had never used.

CONCLUSIONS

Methamphetamine use is an independent risk factor for violence perpetration and victimisation in the general population.

Melatonin pretreatment attenuates acute methamphetamine-induced aggression in male ICR mice

Aggression is one of the symptoms of methamphetamine (MA) use and withdrawal, which can exacerbate MA addiction and relapse. Many studies have demonstrated that poor sleep is significantly associated with aggression. Melatonin has been indicated to be effective in treating sleep disorders induced by MA, and it can also protect neuronal cells against MA-induced neurotoxicity. However, the underlying effects of melatonin on MA-reduced aggression remain unclarified. This study was designed to evaluate the effects of melatonin on acute MA-induced aggressive behavior in male ICR mice and the effects on neurotransmitters related to aggression. Fifty male ICR mice were randomly assigned to control and treatment groups pretreated with MA (3 mg/kg) or melatonin (2.5, 5, 10 mg/kg) plus MA. Aggressive behaviors were observed through isolation-induced aggression in the resident-intruder model. High-performance liquid chromatography combined with electrochemical detection (HPLC-ECD) was used to anatomize the levels of dopamine (DA) and its metabolites, 3,4-dihydroxyphenyl acetic acid (DOPAC) and homovanillic acid (HVA), and the concentrations of serotonin (5-HT) and its metabolite, 5-hydroxyindoleacetic acid (5-HIAA), in the hippocampus involved in behavior processing. The results showed that acute MA administration decreased latency to initial attacks and thereby increased the number and total duration of attacks. Furthermore, HVA level as well as 5-HIAA and 5-HT turnover estimated by 5-HIAA/5-HT ratios declined compared to those in the vehicle group. The medium melatonin pretreatment dose (5 mg/kg) could significantly reverse acute MA-induced aggressive behavior in the form of prolonging latency to initial attacks and thereby attenuating the number of attacks and total duration of attacks. HVA and 5-HIAA levels, 5-HT turnover estimated by 5-HIAA/5-HT ratios, and DA turnover estimated by HVA/DA ratios and (DOPAC + HVA)/DA ratios were elevated compared to those in the MA group. These results indicate that the DA and 5-HT systems are involved in the processes of MA-induced aggressive behaviors and that melatonin has the capacity to reverse MA-induced aggressive behaviors.

The Effect of Chronic Methamphetamine Exposure on the Hippocampal and Olfactory Bulb Neuroproteomes of Rats

Nowadays, drug abuse and addiction are serious public health problems in the USA. Methamphetamine (METH) is one of the most abused drugs and is known to cause brain damage after repeated exposure. In this paper, we conducted a neuroproteomic study to evaluate METH-induced brain protein dynamics, following a two-week chronic regimen of an escalating dose of METH exposure. Proteins were extracted from rat brain hippocampal and olfactory bulb tissues and subjected to liquid chromatography-mass spectrometry (LC-MS/MS) analysis. Both shotgun and targeted proteomic analysis were performed. Protein quantification was initially based on comparing the spectral counts between METH exposed animals and their control counterparts. Quantitative differences were further confirmed through multiple reaction monitoring (MRM) LC-MS/MS experiments. According to the quantitative results, the expression of 18 proteins (11 in the hippocampus and 7 in the olfactory bulb) underwent a significant alteration as a result of exposing rats to METH. 13 of these proteins were up-regulated after METH exposure while 5 were down-regulated. The altered proteins belonging to different structural and functional families were involved in processes such as cell death, inflammation, oxidation, and apoptosis.

Frontal white matter changes and aggression in methamphetamine dependence

Chronic methamphetamine (MA) use can lead to white matter (WM) changes and increased levels of aggression. While previous studies have examined WM abnormalities relating to cognitive impairment, associations between WM integrity and aggression in MA dependence remain unclear. Diffusion Tensor Imaging (DTI) was used to investigate WM changes in 40 individuals with MA dependence and 40 matched healthy controls. A region of interest (ROI) approach using tract based spatial statistics (TBSS) in FSL was performed. We compared fractional anisotropy (FA), mean diffusivity (MD), parallel diffusivity (λ║) and perpendicular diffusivity (λ┴) in WM tracts of the frontal brain. A relationship of WM with aggression scores from the Buss & Perry Questionnaire was investigated. Mean scores for anger (p < 0.001), physical aggression (p = 0.032) and total aggression (p = 0.021) were significantly higher in the MA group relative to controls. ROI analysis showed increased MD (U = 439.5, p = 0.001) and λ┴ (U = 561.5, p = 0.021) values in the genu of the corpus callosum, and increased MD (U = 541.5, p = 0.012) values in the right cingulum in MA dependence. None of the WM changes were significantly associated with aggression scores. This study provides evidence of frontal WM changes and increased levels of aggression in individuals with MA dependence. The lack of significant associations between WM and aggressive behaviour may reflect methodological issues in measuring such behaviour, or may indicate that the neurobiology of aggression is not simply correlated with WM damage but is more complex.

Monoamine-sensitive developmental periods impacting adult emotional and cognitive behaviors

Development passes through sensitive periods, during which plasticity allows for genetic and environmental factors to exert indelible influence on the maturation of the organism. In the context of central nervous system development, such sensitive periods shape the formation of neurocircuits that mediate, regulate, and control behavior. This general mechanism allows for development to be guided by both the genetic blueprint as well as the environmental context. While allowing for adaptation, such sensitive periods are also vulnerability windows during which external and internal factors can confer risk to disorders by derailing otherwise resilient developmental programs. Here we review developmental periods that are sensitive to monoamine signaling and impact adult behaviors of relevance to psychiatry. Specifically, we review (1) a serotonin-sensitive period that impacts sensory system development, (2) a serotonin-sensitive period that impacts cognition, anxiety- and depression-related behaviors, and (3) a dopamine- and serotonin-sensitive period affecting aggression, impulsivity and behavioral response to psychostimulants. We discuss preclinical data to provide mechanistic insight, as well as epidemiological and clinical data to point out translational relevance. The field of translational developmental neuroscience has progressed exponentially providing solid conceptual advances and unprecedented mechanistic insight. With such knowledge at hand and important methodological innovation ongoing, the field is poised for breakthroughs elucidating the developmental origins of neuropsychiatric disorders, and thus understanding pathophysiology. Such knowledge of sensitive periods that determine the developmental trajectory of complex behaviors is a necessary step towards improving prevention and treatment approaches for neuropsychiatric disorders.

Dopamine and serotonin signaling during two sensitive developmental periods differentially impact adult aggressive and affective behaviors in mice

Pharmacologic blockade of monoamine oxidase A (MAOA) or serotonin transporter (5-HTT) has antidepressant and anxiolytic efficacy in adulthood. Yet, genetically conferred MAOA or 5-HTT hypoactivity is associated with altered aggression and increased anxiety/depression. Here we test the hypothesis that increased monoamine signaling during development causes these paradoxical aggressive and affective phenotypes. We find that pharmacologic MAOA blockade during early postnatal development (P2-P21) but not during peri-adolescence (P22-41) increases anxiety- and depression-like behavior in adult (>P90) mice, mimicking the effect of P2-21 5-HTT inhibition. Moreover, MAOA blockade during peri-adolescence, but not P2-21 or P182-201, increases adult aggressive behavior, and 5-HTT blockade from P22-P41 reduced adult aggression. Blockade of the dopamine transporter, but not the norepinephrine transporter, during P22-41 also increases adult aggressive behavior. Thus, P2-21 is a sensitive period during which 5-HT modulates adult anxiety/depression-like behavior, and P22-41 is a sensitive period during which DA and 5-HT bi-directionally modulate adult aggression. Permanently altered DAergic function as a consequence of increased P22-P41 monoamine signaling might underlie altered aggression. In support of this hypothesis, we find altered aggression correlating positively with locomotor response to amphetamine challenge in adulthood. Proving that altered DA function and aggression are causally linked, we demonstrate that optogenetic activation of VTA DAergic neurons increases aggression. It therefore appears that genetic and pharmacologic factors impacting dopamine and serotonin signaling during sensitive developmental periods can modulate adult monoaminergic function and thereby alter risk for aggressive and emotional dysfunction.

Conduct Disorder as a Risk Factor for Violent Victimization and Offending among Regular Illicit Drug Users

This paper aimed to examine the prevalence, correlates and nature of violent crime by, and upon, regular drug users by conduct disorder (CD) status. Interview data was collected from 299 regular psychostimulant and/or opioid users. Conduct disorder significantly increased the lifetime and past 12 month risk of violent victimization and offending. While CD did not independently predict recent violent victimization, it did predict recent violent offending. Greater alcohol dependence and involvement in drug dealing were predictors of both recent victimization and offending. The study indicates that there is significant temporal stability between childhood CD behaviors and later violent behavior among individuals with substance use problems. The study also highlights that there is heterogeneity in the risk of violence exposure in drug using populations, a finding which has implications for early intervention and for treatment interventions among dependent drug user populations.

The toxicology of homicide offenders and victims: A review

ISSUES

The toxicology of homicide offenders and victims, and homicide as a cause of death among psychoactive substance users.

APPROACH

Review of the toxicology of homicide, and homicide as a cause of death among psychoactive substance users.

KEY FINDINGS

A half or more of offenders are intoxicated by a psychoactive substance at the time of the homicide, with alcohol the most commonly reported substance. Levels of substances among victims are comparable with those seen among perpetrators. Among both offenders and victims, levels of substances far exceed population use. Among substance users, homicide specific mortality rates of substance users far exceed population rates. Reducing rates of alcohol and other drug consumption, at national and individual levels, can be expected to substantially reduce rates of, and risk for, homicide.

CONCLUSIONS AND IMPLICATIONS

Psychoactive substances are strongly associated with homicide. One of the major societal benefits that can be derived from active attempts to reduce alcohol and other drug use are reductions in homicide rates.

Comparative rates of violent crime among regular methamphetamine and opioid users: offending and victimization

AIMS

To determine the comparative levels of violent offending and victimization among regular methamphetamine and heroin users.

DESIGN

Cross-sectional Setting Sydney, Australia.

PARTICIPANTS

A total of 400 regular methamphetamine (METH) and heroin (HER) users (118 methamphetamine users: METH; 161 regular heroin users: HER; 121 regular users of both: BOTH).

FINDINGS

Eighty-two per cent reported a life-time history of committing violent crime, 41% in the past 12 months. There were no group differences in life-time violence, but the METH group were significantly more likely than the HER group to have committed violence in the past 12 months (odds ratio 1.94). Nearly all (95%) reported that they had been a victim of violent crime, 46% in the preceding 12 months, with no group differences. Those who had committed a violent crime in the past 12 months were 13.23 times more likely to have been a victim in that period. The majority believed it unlikely that they would be a victim of (78%), or commit (87%), a violent crime in the next 12 months.

CONCLUSIONS

Regular methamphetamine use appears to be associated with an increased risk of violent offending, but not victimization, compared with heroin use.

Mechanisms underlying aggressive and hostile behavior in amphetamine users

PURPOSE OF REVIEW

To review current evidence linking amphetamine use with aggression and to consider possible factors that might underlie this association.

RECENT FINDINGS

Although evidence that amphetamine use is related to increased levels of aggression continues to grow, the underlying processes or mechanisms remain somewhat elusive. In this review, three possible underlying factors are considered. Neurotoxic, pharmacological effects of amphetamine on the dopaminergic and serotonergic systems are related to aggressive, hostile behavior in both animal and human studies. Of particular interest is the converging evidence that amphetamine use is related to impairment in executive functions (including self-control) that are regulated by the prefrontal cortex. Taken together, these findings suggest that amphetamine users may have an impaired capacity to control or inhibit aggressive impulses. Furthermore, high levels of impulsivity related to amphetamine use may also play a role. Finally, amphetamine use is associated with increased positive symptoms of psychosis, particularly paranoia, that contribute to a perception of the environment as a hostile, threatening place.

SUMMARY

Taken separately, each of these factors may lead to an increase in aggression with increased use of amphetamine, but their interactive or synergistic effects may be particularly problematic.

Impulsivity and positive psychotic symptoms influence hostility in methamphetamine users

Methamphetamine (MA) use is associated with hostility, aggression, and positive psychotic symptoms. However, little is known of the processes or mechanisms that underlie this relationship. The present research was designed to investigate putative mediating and moderating variables between MA dependence and hostility in a sample of injecting MA users (N=237). Both positive symptoms of psychosis and higher levels of impulsivity functioned as mediators and moderators of this relationship. This pattern of findings suggests that MA use leads to greater hostility by increasing positive psychotic symptoms that contribute to a perception of the environment as a hostile and threatening place as well as by increasing impulsivity. Those who were high in positive symptoms and high in impulsivity were the most hostile. Individual differences in impulsivity and positive psychotic symptoms should be taken into account in the assessment and management of MA dependence.

Patterns of risky behaviors associated with methamphetamine use among young Thai adults: a latent class analysis

PURPOSE

Methamphetamine (MA) is the leading illicit drug in Thailand among youth and young adults. Sexual risk behaviors are associated with methamphetamine use, but few data are available on the daily context of methamphetamine use. We developed an inductive behavioral typology that young Thais engage in while using methamphetamine.

METHODS

We conducted a cross-sectional study in Chiang Mai, Thailand, in 2005-2006 among 1,162 street-recruited methamphetamine smokers 18-25 years of age. Data collected included sociodemographic characteristics, sexual behaviors, and drug use patterns. Latent class analysis was used to describe patterns of activities in which participants reported engaging directly after using MA. Logistic regression was used to examine univariate correlates of class membership, separately by gender.

RESULTS

Participants were 75% male with a median age of 19 years. More than half of participants reported frequent alcohol use (>or=4 days/week) and half of the sample reported smoking MA >or=2 days/ week. Three classes of activities emerged for male participants (n = 863): "work" (job related); "high-risk behaviors" (motorcycle riding, fighting, sex); and "combined" (all activities). Two classes emerged for the women (n = 299): "work" (housework) and "high-risk behaviors." "High-risk behaviors" and "combined" (men only) classes were associated with more frequent alcohol and methamphetamine use compared with the "work" class.

CONCLUSIONS

Our study found a distinct typology of behaviors associated with substance abuse among young adults in Thailand. Behavioral typologies allow a better understanding of the nuances of "risky" behaviors and might prove useful in targeting interventions.

Evaluation of a peer network intervention trial among young methamphetamine users in Chiang Mai, Thailand

Since the 1990s, there has been a proliferation of methamphetamine use in Thailand, particularly among young people. Simultaneously, risky sexual behaviors among this population have increased. This study examined the effects of a peer network intervention and a life-skills intervention on methamphetamine and HIV risk behaviors among 18-25 year olds in Chiang Mai, Thailand. Between April 2005 and June 2007, we conducted a randomized behavioral trial to compare the efficacy of a peer educator, network-oriented intervention with a best practice, life-skills curriculum on methamphetamine use, sexual behaviors, and incident sexually transmitted infections (STIs). Follow-up occurred at 3-, 6-, 9-, and 12 months. Both conditions consisted of seven, 2h, small group sessions. Longitudinal analyses of the three outcomes were conducted by fitting repeated measures logistic regression models using generalized estimating equations. Participants (N=983) attended a median of six sessions, with no differences between arms. At each follow-up visit, retention was greater than 85%. Participants were 75% male and were a median of 19 years old. Over time, participants in both conditions showed a significant and dramatic decline in self-reported methamphetamine use (99% at baseline vs. 53% at 12 months, p<0.0001) and significant increase in consistent condom use (32% baseline vs. 44% at 12 months, p<0.0001). Incident STIs were common, with no differences between arms. Chlamydia had the highest incidence rate, 9.85/100 person years and HIV had a low incidence rate of 0.71/100 person years. Among young Thais, we found that a peer educator, network-oriented intervention was associated with reductions in methamphetamine use, increases in condom use, and reductions in incident STIs over 12 months. We also found parallel reductions with the life-skills condition. To our knowledge, this is the first such trial targeting this population. Small group interventions are an effective means of reducing methamphetamine use and sexual risk among Thai youth.

Major physical and psychological harms of methamphetamine use

ISSUES

The major physical and psychological health effects of methamphetamine use, and the factors associated with such harms.

APPROACH

Comprehensive review.

KEY FINDINGS

Physical harms reviewed included toxicity and mortality, cardiovascular/cerebrovascular pathology, dependence and blood-borne virus transmission. Psychological harms include methamphetamine psychosis, depression, suicide, anxiety and violent behaviours.

IMPLICATIONS

While high-profile health consequences, such as psychosis, are given prominence in the public debate, the negative sequelae extend far beyond this. This is a drug class that causes serious heart disease, has serious dependence liability and high rates of suicidal behaviours.

CONCLUSION

The current public image of methamphetamine does not portray adequately the extensive, and in many cases insidious, harms caused.

Methamphetamine administration causes death of dopaminergic neurons in the mouse olfactory bulb

BACKGROUND

Methamphetamine (METH) is an addictive drug that can cause neurological and psychiatric disorders. In the rodent brain, toxic doses of METH cause damage of dopaminergic terminals and apoptosis of nondopaminergic neurons. The olfactory bulb (OB) is a brain region that is rich with dopaminergic neurons and terminals.

METHODS

Rats were given a single injection of METH (40 mg/kg) and sacrificed at various time points afterward. The toxic effects of this injection on the OB were assessed by measuring monoamine levels, tyrosine hydroxylase (TH) immunocytochemistry, terminal deoxynucleotidyl transferase-mediated deoxyribonucleotide triphosphate (dNTP) nick end labeling (TUNEL) histochemistry, and caspase-3 immunochemistry.

RESULTS

Methamphetamine administration caused marked decreases in dopamine (DA) levels and TH-like immunostaining in the mouse OB. The drug also caused increases in TUNEL-labeled OB neurons, some of which were also positive for TH expression. Moreover, there was METH-induced expression of activated caspase-3 in TH-positive cells. Finally, the METH injection was associated with increased expression of the proapoptotic proteins, Bax and Bid, but with decreased expression of the antideath protein, Bcl2.

CONCLUSIONS

These observations show, for the first time, that METH can cause loss of OB DA terminals and death of DA neurons, in part, via mechanisms that are akin to an apoptotic process.

Methamphetamine causes alterations in the MAP kinase-related pathways in the brains of mice that display increased aggressiveness

Aggressive behaviors have been reported in patients who suffer from some psychiatric disorders, and are common in methamphetamine (METH) abusers. Herein, we report that multiple (but not single) injections of METH significantly increased aggressiveness in male CD-1 mice. This increase in aggressiveness was not secondary to METH-induced hyperactivity. Analysis of protein expression using antibody microarrays and Western blotting revealed differential changes in MAP kinase-related pathways after multiple and single METH injections. There were statistically significant (p<0.05) decreases in MEK1, Erk2p, GSK3alpha, 14-3-3e, and MEK7 in the striata of mice after multiple injections of METH. MEK1 was significantly decreased also after a single injection of METH, but to a much lesser degree than after multiple injections of METH. In the frontal cortex, there was a statistically significant decrease in GSK3alpha after multiple (but not single) injections of METH. These findings suggest that alterations in MAP kinase-related pathways in the prefronto-striatal circuitries might be involved in the manifestation of aggressive behaviors in mice.

Repeated Catha edulis oral administration enhances the baseline aggressive behavior in isolated rats

The effects of repeated oral administration of the psychostimulant plant, Catha edulis and its active principle, cathinone on rats were studied using isolation induced aggression paradigm. The behavioral responses were videotaped and scored later by offline data analyses. Rats were decapitated at the end of the behavioral experiment and in the relevant brain regions, monoamines were assessed. The results demonstrate that isolation of male rats produces a baseline aggression. Treatments with the psychostimulant plant, Catha edulis or commercial S-(--)-cathinone enhanced significantly: The locomotor activities and the baseline aggression behaviors compared with vehicle treated rats. Neurochemical correlates revealed a significant depletion of serotonin (5-HT) and its corresponding metabolites (5-HIAA) in both the anterior and posterior striatum. There was also a reduction in the level of homovanillic acid (HVA) in the hippocampus. Additionally, elevation of dopamine level was observed in the nucleus accumbens, especially, in those rats treated with Catha edulis extract. Cathinone, on the other hand, increased the level of HVA in the posterior striatum and decreased HVA in the nucleus accumbens. In conclusion, the present data demonstrate that repeated administration of Catha edulis or S-(--)-cathinone enhances aggression in rats, presumably by decreasing the level of serotonin and its corresponding metabolites. Besides, the data obtained do not rule out the involvement of dopamine in aggression behavior.