High ambient temperature increases the toxicity and lethality of 3,4-methylenedioxymethamphetamine and methcathinone

Gut microbiota-derived trimethylamine N-oxide involved in methamphetamine-induced depression-like behaviors of male mice

Methamphetamine (METH)-provoked psychiatric symptoms are a major health concern, with depression being a prevalent symptom among METH abusers. Recently, gut microbiota-derived metabolites have been involved in various psychosis pathogenesis, but their roles in METH-induced depression remain unclear. This study investigates the implication of gut microbiota-derived metabolite trimethylamine N-oxide (TMAO) in METH-induced depressive-like behaviors (DLBs). We examined the circulating TMAO levels post-METH exposure besides exploring the impacts of TMAO on METH-triggered DLBs. Then, potential causes of TMAO alterations were explored, along with its effects on hippocampal neuronal damage and neuroinflammation. The findings showcased that METH-treated mice displayed DLBs accompanied by increased serum TMAO levels. Similarly, introducing TMAO to the drinking water elevated serum TMAO levels and induced DLBs. Although METH exposure did not notably alter the abundance of the gut microbiota, antibiotic (ABX) therapy suppressed the increased serum TMAO levels and the onset of DLBs. Additionally, choline and L-carnitine levels were elevated following METH exposure, which may be a potential mechanism for TMAO metabolic dysregulation. Elevated TMAO levels resulted in an elevation in Nissl-positive dead cells, the number of microglia, TNF-α, and IL-1β levels, along with TLR-4, NF-κB, and MyD88 expression in the hippocampal CA3 region. Inhibition of TMAO synthesis mitigated METH-provoked neuronal damage and neuroinflammation.

Effects of the designer drug 4-methylamphetamine on core temperature and serotonin levels in the striatum and hippocampus of rats

New psychoactive substances (NPS) are typically synthesized in clandestine laboratories in an attempt to chemically modify already federally regulated drugs in an effort to circumvent the law. Drugs derived from a phenethylamine pharmacophore, such as 4-chloroamphetamine and 3,4-methylenedioxymethamphetamine (MDMA), reliably induce thermogenesis and serotonergic deficits in the striatum and hippocampus of rodents. 4-methylamphetamine (4-MA), a relative newcomer to the NPS scene, was originally investigated in the mid-1900 s as a potential anorexigenic agent. With its phenethylamine pharmacophore, 4-MA was hypothesized to produce similar toxicological alterations as its chemical analogs. In the present study, three doses (1.0, 2.5, and 5.0 mg/kg, ip.) of 4-MA were administered to rats twice daily for two days. Core temperature data were calculated and analyzed as temperature area under the curve (TAUC). On the second day of dosing, a hypothermic response to 4-MA (2.5 and 5.0 mg/kg) was noted between 0.5 and 2.0 h post-treatment. Only the highest dose of 4-MA decreased body weight on the second day of treatment and maintained this reduction in weight for seven days after treatment ceased. None of the doses of 4-MA evaluated significantly altered serotonin levels in the hippocampus or striatum seven days after final treatment. The present findings demonstrate that the 4-methyl substitution to amphetamine generates a pharmacological and toxicological profile that differs from other similar phenethylamine analogs.

Cannabis and Other Substance Misuse: Implications and Regulations

Abusing controlled substances, including cannabis and various drugs, can result in severe intoxication and even death. Therefore, a comprehensive postmortem analysis is crucial for understanding the underlying causes of such fatalities. This narrative review discusses the characteristics of commonly abused controlled substances, the methodologies employed in postmortem analysis, lethal dosage levels, mechanisms of toxicity, side effects, and existing regulations. The focus centers on seven prevalent groups of controlled substances, namely cannabis, opioids, amphetamine-type stimulants, cocaine, new psychoactive substances, and hallucinogens. These groups have been linked to an increased risk of fatal overdose. Most substances in these groups exert neurotoxic effects by targeting the central nervous system (CNS). Consequently, strict regulation is essential to mitigate the potential harm posed by these substances. To combat abuse, prescribers must adhere to guidelines to ensure their prescribed medications comply with the outlined regulations. Through an enhanced understanding of controlled substance abuse and its consequences, more effective strategies can be developed to reduce its prevalence and associated mortality.

Serotonin-releasing agents with reduced off-target effects

Increasing extracellular levels of serotonin (5-HT) in the brain ameliorates symptoms of depression and anxiety-related disorders, e.g., social phobias and post-traumatic stress disorder. Recent evidence from preclinical and clinical studies established the therapeutic potential of drugs inducing the release of 5-HT via the 5-HT-transporter. Nevertheless, current 5-HT releasing compounds under clinical investigation carry the risk for abuse and deleterious side effects. Here, we demonstrate that S-enantiomers of certain ring-substituted cathinones show preference for the release of 5-HT ex vivo and in vivo, and exert 5-HT-associated effects in preclinical behavioral models. Importantly, the lead cathinone compounds (1) do not induce substantial dopamine release and (2) display reduced off-target activity at vesicular monoamine transporters and 5-HT2B-receptors, indicative of low abuse-liability and low potential for adverse events. Taken together, our findings identify these agents as lead compounds that may prove useful for the treatment of disorders where elevation of 5-HT has proven beneficial.

Methamphetamine-induced lethal toxicity in zebrafish larvae

RATIONALE

The use of novel psychoactive substances has been steadily increasing in recent years. Given the rapid emergence of new substances and their constantly changing chemical structure, it is necessary to develop an efficient and expeditious approach to examine the mechanisms underlying their pharmacological and toxicological effects. Zebrafish (Danio rerio) have become a popular experimental subject for drug screening due to their amenability to high-throughput approaches.

OBJECTIVES

In this study, we used methamphetamine (METH) as an exemplary psychoactive substance to investigate its acute toxicity and possible underlying mechanisms in 5-day post-fertilization (5 dpf) zebrafish larvae.

METHODS

Lethality and toxicity of different concentrations of METH were examined in 5-dpf zebrafish larvae using a 96-well plate format.

RESULTS

METH induced lethality in zebrafish larvae in a dose-dependent manner, which was associated with initial sympathomimetic activation, followed by cardiotoxicity. This was evidenced by significant heart rate increases at low doses, followed by decreased cardiac function at high doses and later time points. Levels of ammonia in the excreted water were increased but decreased internally. There was also evidence of seizures. Co-administration of the glutamate AMPA receptor antagonist GYKI-52466 and the dopamine D2 receptor antagonist raclopride significantly attenuated METH-induced lethality, suggesting that this lethality may be mediated synergistically or independently by glutamatergic and dopaminergic systems.

CONCLUSIONS

These experiments provide a baseline for the study of the toxicity of related amphetamine compounds in 5-dpf zebrafish as well as a new high-throughput approach for investigating the toxicities of rapidly emerging new psychoactive substances.

Serotonin toxicity of serotonergic psychedelics

RATIONALE

In recent years, psychedelic substances with serotonergic mechanisms have accumulated substantial evidence that they may provide therapeutic benefits for people suffering with psychiatric symptoms. Psychiatric disorders targeted by these psychedelic-assisted therapies are managed with serotonergic drugs like selective serotonin reuptake inhibitors (SSRIs) as the current standard of care, so it is important to evaluate the potential risks of drug-drug interactions and serotonin toxicity (ST) between these agents.

OBJECTIVES

A critical evaluation of the scientific literature is necessary to delineate the risks of ST when combining psychedelics with available serotonergic pharmacotherapy options. This review article describes signs and symptoms of ST, characterizes mechanisms of ST risk, summarizes what is known about serotonergic psychedelic drug interactions, and outlines potential management strategies.

RESULTS

True ST typically occurs with a serotonergic drug overdose or in combinations in which a drug that can increase intrasynaptic serotonin is combined with a monoamine oxidase inhibitor (MAOI). Serotonergic psychotropics that do not contain MAOIs are low risk in combination with psychedelics that also do not contain MAOIs. Signs and symptoms warranting immediate medical attention include myoclonus, extreme and fluctuating vital signs, agitation or comatose mental state, muscle rigidity, pronounced hyperthermia (fever), and/or seizure activity.

CONCLUSIONS

Serotonin-related adverse reactions exist along a spectrum with serotonin syndrome being the most severe manifestations of ST. Due to varying serotonergic mechanisms of psychedelics and psychotropics, with varying propensities to increase intrasynaptic serotonin, some combinations may present a significant risk for serotonin toxicity (ST) while others are likely benign.

Neurotoxicity of MDMA: Main effects and mechanisms

Preclinical and clinical studies indicate that 3,4-methylenedioxymethamphetamine (MDMA; 'ecstasy'), in addition to having abuse potential, may elicit acute and persistent abnormalities of varying severity at the central level. Importantly, neurotoxic effects of MDMA have been demonstrated in experimental animals. Accordingly, central toxicity induced by MDMA may pose a serious harm for health, since MDMA is among the substances that are used for recreational purposes by young and adult people. This review provides a concise overview of recent findings from preclinical and clinical studies that evaluated the central effects of MDMA, and the mechanisms involved in the neurotoxicity induced by this amphetamine-related drug.

Methcathinone decreases dopamine transporter function: Role of protein kinase C

Methcathinone (MCAT) is a psychostimulant of abuse that can cause both persistent striatal dopaminergic and serotonergic, as well as hippocampal serotonergic, deficits. Evidence suggests that the rapid effects of stimulants that are structurally and mechanistically similar to MCAT on monoamine transporter function may contribute to the abuse liability and/or persistent monoaminergic deficits caused by these agents. Thus, effects of MCAT on 1) striatal dopamine (DA) transporter (DAT); and 2) striatal and hippocampal serotonin transporter (SERT) function, as determined in tissues from adult male rats, were assessed. As reported previously, a single administration of MCAT rapidly (within 1 hr) decreases striatal [³ H]DA uptake. Similarly, incubation of rat synaptosomes with MCAT at 37℃ (but not 4˚C) decreased striatal [³ H]DA uptake. Incubation with MCAT likewise decreased [³ H]5HT but not vesicular [³ H]DA uptake. MCAT incubation in vitro was without effect on [³ H]DA uptake in striatal synaptosomes prepared from MCAT-treated rats. The decrease in [³ H]DA uptake caused by MCAT incubation: (a) reflected a decrease in V_max , with minimal change in K_m , and (b) was attenuated by co-incubation with the cell-permeable calcium chelator, N,N'-[1,2-ethanediylbis(oxy-2,1-phenylene)]bis[N-[2-[(acetyloxy)methoxy]-2-oxoethyl]-1,1'-bis[(acetyloxy)methyl] ester-glycine (BAPTA-AM), as well as the non-selective protein kinase-C (PKC) inhibitors bisindolylmaleimide-1 (BIM-1) and 2-[1-3(Aminopropyl)indol-3-yl]-3(1-methyl-1H-indol-3-yl)maleimide (or Bisindolylmaleimide VIII; Ro-31-7549). Taken together, these results suggest that in vitro MCAT incubation may model important aspects of MCAT administration in vivo, and that calcium and PKC contribute to the in vitro effects of MCAT on DAT.

Ecstasy : la deuxième vague…

La molécule de MDMA (3,4-méthylènedioxyméthamphétamine ou ecstasy) a plus de 100 ans. Sa consommation a explosé dans les années 1990, essentiellement dans un cadre « festif » ou « récréatif ». Elle a ensuite considérablement diminué au début des années 2000 et connaît actuellement un regain d’intérêt certain. Sa consommation a volontiers été considérée comme anodine avant qu’il n’apparaisse clairement qu’elle pouvait provoquer des décès, en l’absence même de « surdose ». Les mécanismes de toxicité sont multiples, complexes et imparfaitement élucidés. L’interaction avec les principaux neuromédiateurs est certaine. L’ecstasy est classée dans les produits empathogènes. Sa consommation vise à favoriser les relations sociales. De nombreux effets secondaires sont possibles. Les conditions de consommation, en ambiance confinée, avec une activité physique soutenue et prolongée favorisent la survenue des effets secondaires. Les effets secondaires bénins sont tolérés et considérés comme étant le « prix à payer » dans la recherche des effets psychogènes. En raison de son tropisme, les principales complications de la consommation d’ecstasy sont psychiatriques et neurologiques, mais aussi cardiovasculaires, respiratoires et métaboliques. Cependant, les formes graves de l’intoxication sont marquées par un tableau d’hyperthermie maligne responsable de complications multiples et pouvant conduire au décès. Tous les auteurs insistent sur la possibilité de complications, de formes graves, voire de décès après la consommation d’une dose unique de MDMA. Il n’y a pas de traitement spécifique. Le traitement symptomatique est au premier plan. Hydratation et sédation sont les clés de ce traitement.