Dexamphetamine effects on prepulse inhibition (PPI) and startle in healthy volunteers

Dental injuries in Swiss soccer supporters: A comparative study of regular fans, ultras, and hooligans for public health strategies

OBJECTIVES

Violence among soccer supporters continues to pose a significant public health concern in many parts of the world. In Switzerland, hooliganism is largely uninvestigated. This study aimed to examine incidents of violence and associated dental injuries among different groups of soccer supporters, as well as assess the impact of intoxicants on their behavior, using survey data from regular fans, ultras, and hooligans in the Swiss Football League.

MATERIAL AND METHODS

A cross-sectional survey using a standardized questionnaire was conducted among distinct factions of soccer supporters in the Swiss Football League in 2022. A total of 165 participants self-identified as belonging to one of three subgroups: "regular fan," "ultra," or "hooligan." Data were gathered on physical altercations, dental injuries, possession of mouthguards, intoxicant use, and medical assistance. Descriptive statistics, logistic regression models, and significance tests were used for data analysis (α = .05).

RESULTS

Hooligans had a higher frequency of dental injuries resulting from fights than ultras and regular fans. Hooligans with 11-20 fights per soccer season had a 9.6 times higher probability of dental trauma than those with 0-5 fights (p = .048). Possession of a mouthguard was associated with a lower risk of dental injuries for hooligans but an increased risk for ultras. Additionally, hooligans were found to differ significantly from other groups in their consumption of amphetamines and cocaine (p < .001).

CONCLUSIONS

The study found a strong link between physical altercations and dental injuries among soccer supporters. To promote better prevention, there is a necessity for enhanced educational initiatives facilitated by dentists to amplify the dissemination of mouthguards. Furthermore, it is crucial to raise awareness regarding their proper fitting to minimize the occurrence of combat-related dental injuries. Health authorities and other stakeholders should take a comprehensive approach to addressing some of the root causes of violent behavior, which include alcohol abuse and illicit substance consumption.

Comparative Analysis of Dopaminergic and Cholinergic Mechanisms of Sensory and Sensorimotor Gating in Healthy Individuals and in Patients With Schizophrenia

Sensory and sensorimotor gating provide the early processing of information under conditions of rapid presentation of multiple stimuli. Gating deficiency is observed in various psychopathologies, in particular, in schizophrenia. However, there is also a significant proportion of people in the general population with low filtration rates who do not show any noticeable cognitive decline. The review article presents a comparative analysis of existing data on the peculiarities of cholinergic and dopaminergic mechanisms associated with lowering gating in healthy individuals and in patients with schizophrenia. The differences in gating mechanisms in cohorts of healthy individuals and those with schizophrenia are discussed.

Intoxicated aggression: Do alcohol and stimulants cause dose-related aggression? A review

RATIONALE

Violence and drug use are significant public health challenges that are strongly linked. It is known that alcohol plays a major role in the causation of unnatural deaths and that stimulants like cocaine and amphetamine are often implicated in aggressive acts or violence. However, a clear causal relationship between these substances and aggression, and more specifically a blood concentration threshold at which intoxicated aggression emerges is lacking. In case of a crime and subsequent law enforcement, knowledge about dose-response relationships could be of pivotal importance when evaluating the role of alcohol and drugs in aggressive offences.

AIMS

The present review aimed to determine whether there is a causal relation between intoxication with these psychoactive substances and aggression, and to define blood concentration thresholds above which these substances elicit aggression.

METHODS

Empirical articles published between 2013 and 2017 and review papers containing the predefined search strings were identified through searches in the PubMed and Embase databases and additional reference list searches. The complete search query yielded 1578 publications. Initially all articles were manually screened by title and abstract. Articles with irrelevant titles, given the selected search terms and review aims were discarded. Remaining articles were carefully studied and those that did not comply with the main objectives of this review were discarded. At the end of this process, 167 titles were found eligible for review.

FINDINGS AND CONCLUSION

While placebo-controlled experimental studies clearly showed a causal link between alcohol and aggression, it is evident that such a link has not yet been established for cocaine and amphetamines. In case of alcohol, it is clear that there are various individual and contextual factors that may contribute to the occurrence of an aggressive act during intoxication. A clear threshold blood alcohol concentration has not been defined yet for alcohol, but a statistically significant increase of aggression has been demonstrated at a dose of 0.75 g/kg and higher. Future studies into intoxicated aggression should include multiple doses of alcohol and stimulants and take into account individual and contextual factors.

Setting the beat of an internal clock: Effects of dexamphetamine on different interval ranges of temporal processing in healthy volunteers

Drug studies are powerful models to investigate the neuropharmacological mechanisms underlying temporal processing in humans. This study administered dexamphetamine to 24 healthy volunteers to investigate time perception at different time scales, along with contributions from working memory. Healthy volunteers were administered 0.45 mg/kg dexamphetamine or placebo in a double-blind, crossover, placebo-controlled design. Time perception was assessed using three experimental tasks: a time-discrimination task, which asked participants to determine whether a comparison interval (1200 ± 0, 50, 100, 150, 200 ms) was shorter or longer than a standard interval (1200 ms); a retrospective time estimation task, which required participants to verbally estimate time intervals (10, 30, 60, 90 and 120 s) retrospectively; and a prospective time-production task, where participants were required to prospectively monitor the passing of time (10, 30, 60, 90 and 120 s). Working memory was assessed with the backwards digit span. On the discrimination task, there was a change in the proportion of long-to-short responses and reaction times in the dexamphetamine condition (but no association with working memory), consistent with an increase in the speed of an internal pacemaker, and an overestimation of durations in the timing of shorter intervals. There was an interaction between dexamphetamine, working memory, and performance on the estimation and production tasks, whereby increasing digit span scores were associated with decreasing interval estimates and increased produced intervals in the placebo condition, but were associated with increased interval estimates and decreased produced intervals after dexamphetamine administration. These findings indicate that the dexamphetamine-induced increase in the speed of the internal pacemaker was modulated by the basal working memory capacity of each participant. These findings in healthy humans have important implications for the role of dopamine, and its contributions to timing deficits, in models of psychiatric disorders.

Effects of Amphetamine on Sensorimotor Gating and Neurocognition in Antipsychotic-Medicated Schizophrenia Patients

Prepulse inhibition (PPI) of startle is being explored both as an indicator of target engagement for, and a biomarker predicting the sensitivity to, procognitive effects of drugs. We now report the effects of the pro-attentional drug, d-amphetamine, on PPI and neurocognition in antipsychotic-medicated schizophrenia patients and healthy subjects (HS) who were also tested in a targeted cognitive training (TCT) module. 44 HS and 38 schizophrenia patients completed a double-blind, placebo-controlled crossover study of the effects of a single dose of amphetamine (10 mg po) on PPI and MATRICS Consensus Cognitive Battery (MCCB) performance; TCT results were previously reported from 60 of these subjects. Moderators predicting AMPH sensitivity were assessed, including the rs4680 single-nucleotide polymorphism for catechol-O-methyltransferase (COMT). After placebo, patients exhibited PPI deficits with 60 ms prepulse intervals; these deficits were 'rescued' by amphetamine. The magnitude of amphetamine-enhanced PPI was greater in patients than in HS (p<0.032), and was associated with positive symptoms (p<0.007), antipsychotic load (p<0.015), hedonic effects of AMPH (p<0.003), and with the presence of at least one methionine allele in rs4680 (p<0.008). No significant effects of amphetamine on MCCB performance were detected in either group, though pro-attentional effects of amphetamine in patients were associated with greater amphetamine-enhanced TCT learning. Amphetamine acutely 'normalized' PPI in antipsychotic-medicated schizophrenia patients; no concurrent acute neurocognitive changes were detected by the MCCB. Findings suggest that in the context of appropriate antipsychotic medication, a low dose of amphetamine enhances brain processes associated with higher function in schizophrenia patients, without accompanying changes in MCCB performance.

Pharmacokinetic, Ambulatory, and Hyperthermic Effects of 3,4-Methylenedioxy-N-Methylcathinone (Methylone) in Rats

Methylone (3,4-methylenedioxy-N-methylcathinone) is a synthetic cathinone analog of the recreational drug ecstasy. Although it is marketed to recreational users as relatively safe, fatalities due to hyperthermia, serotonin syndrome, and multi-organ system failure have been reported. Since psychopharmacological data remain scarce, we have focused our research on pharmacokinetics, and on a detailed evaluation of temporal effects of methylone and its metabolite nor-methylone on behavior and body temperature in rats. Methylone [5, 10, 20, and 40 mg/kg subcutaneously (s.c.)] and nor-methylone (10 mg/kg s.c.) were used in adolescent male Wistar rats across three behavioral/physiological procedures and in two temporal windows from administration (15 and 60 min) in order to test: locomotor effects in the open field, sensorimotor gating in the test of prepulse inhibition (PPI), and effects on rectal temperature in individually and group-housed rats. Serum and brain pharmacokinetics after 10 mg/kg s.c. over 8 h were analyzed using liquid chromatography mass spectrometry. Serum and brain levels of methylone and nor-methylone peaked at 30 min after administration, both drugs readily penetrated the brain with serum: brain ratio 1:7.97. Methylone dose-dependently increased overall locomotion. It also decrease the amount of time spent in the center of open field arena in dose 20 mg/kg and additionally this dose induced stereotyped circling around the arena walls. The maximum of effects corresponded to the peak of its brain concentrations. Nor-methylone had approximately the same behavioral potency. Methylone also has weak potency to disturb PPI. Behavioral testing was not performed with 40 mg/kg, because it was surprisingly lethal to some animals. Methylone 10 and 20 mg/kg s.c. induced hyperthermic reaction which was more pronounced in group-housed condition relative to individually housed rats. To conclude, methylone increased exploration and/or decreased anxiety in the open field arena and with nor-methylone had short duration of action with effects typical for mixed indirect dopamine-serotonin agonists such as 3,4-metyhlenedioxymethamphetamine (MDMA) or amphetamine. Given the fact that the toxicity was even higher than the known for MDMA and that it can cause hyperthermia it possess a threat to users with the risk for serotonin syndrome especially when used in crowded conditions.

Effects of Neonatal Dexamethasone Exposure on Adult Neuropsychiatric Traits in Rats

The effects of early life stress in utero or in neonates has long-term consequences on hypothalamic-pituitary-adrenal (HPA) stress axis function and neurodevelopment. These effects extend into adulthood and may underpin a variety of mental illnesses and be related to various developmental and cognitive changes. We examined the potential role of neonatal HPA axis activation on adult psychopathology and dopamine sensitivity in the mature rat using neonatal exposure to the synthetic glucocorticoid receptor agonist and stress hormone, dexamethasone. We utilized a comprehensive battery of assessments for behaviour, brain function and gene expression to determine if elevated early life HPA activation is associated with adult-onset neuropsychiatric traits. Dexamethasone exposure increased startle reactivity under all conditions tested, but decreased sensitivity of sensorimotor gating to dopaminergic disruption–contrasting with what is observed in several neuropsychiatric diseases. Under certain conditions there also appeared to be mild long-term changes in stress and anxiety-related behaviours with neonatal dexamethasone exposure. Electrophysiology revealed that there were no consistent neuropsychiatric abnormalities in auditory processing or resting state brain function with dexamethasone exposure. However, neonatal dexamethasone altered auditory cortex glucocorticoid activation, and auditory cortex synchronization. Our results indicate that neonatal HPA axis activation by dexamethasone alters several aspects of adult brain function and behaviour and may induce long-term changes in emotional stress-reactivity. However, neonatal dexamethasone exposure is not specifically related to any particular neuropsychiatric disease.

Further Advances in Optimizing (2-Phenylcyclopropyl)methylamines as Novel Serotonin 2C Agonists: Effects on Hyperlocomotion, Prepulse Inhibition, and Cognition Models

A series of novel compounds with two halogen substituents have been designed and synthesized to further optimize the 2-phenylcyclopropylmethylamine scaffold in the quest for drug-like 5-HT2C agonists. Compound (+)-22a was identified as a potent 5-HT2C receptor agonist, with good selectivity against the 5-HT2B and the 5-HT2A receptors. ADMET assays showed that compound (+)-22a possessed desirable properties in terms of its microsomal stability, and CYP and hERG inhibition, along with an excellent brain penetration profile. Evaluation of (+)-22a in animal models of schizophrenia-related behaviors revealed that it had a desirable activity profile, as it reduced d-amphetamine-stimulated hyperlocomotion in the open field test, it restored d-amphetamine-disrupted prepulse inhibition, it induced cognitive improvements in the novel object recognition memory test in NR1-KD animals, and it produced very little catalepsy relative to haloperidol. These data support the further development of (+)-22a as a drug candidate for the treatment of schizophrenia.

The effects of dexamphetamine on the resting-state electroencephalogram and functional connectivity

The catecholamines-dopamine and noradrenaline-play important roles in directing and guiding behavior. Disorders of these systems, particularly within the dopamine system, are associated with several severe and chronically disabling psychiatric and neurological disorders. We used the recently published group independent components analysis (ICA) procedure outlined by Chen et al. (2013) to present the first pharmaco-EEG ICA analysis of the resting-state EEG in healthy participants administered 0.45 mg/kg dexamphetamine. Twenty-eight healthy participants between 18 and 41 were recruited. Bayesian nested-domain models that explicitly account for spatial and functional relationships were used to contrast placebo and dexamphetamine on component spectral power and several connectivity metrics. Dexamphetamine led to reductions across delta, theta, and alpha spectral power bands that were predominantly localized to Frontal and Central regions. Beta 1 and beta 2 power were reduced by dexamphetamine at Frontal ICs, while beta 2 and gamma power was enhanced by dexamphetamine in posterior regions, including the parietal, occipital-temporal, and occipital regions. Power-power coupling under dexamphetamine was similar for both states, resembling the eyes open condition under placebo. However, orthogonalized measures of power coupling and phase coupling did not show the same effect of dexamphetamine as power-power coupling. We discuss the alterations of low- and high-frequency EEG power in response to dexamphetamine within the context of disorders of dopamine regulation, in particular schizophrenia, as well as in the context of a recently hypothesized association between low-frequency power and aspects of anhedonia. Hum Brain Mapp 37:570-588, 2016. © 2015 Wiley Periodicals, Inc.