Mechanisms of neurotransmitter release by amphetamines: a review

Prevalence of Methamphetamine (Mkpurummiri) use in south east Nigeria: a community-based cross-sectional study

BACKGROUND

Methamphetamine (MA) (Mkpurummiri) is seen as the most common, accessible and new drug of use/abuse in south east Nigeria. Despite the overwhelming evidence of the dire consequences of this drug to the users, there is lack of empirical research to determine its prevalence in this area where use is assumed to be common. This study aimed to determine the prevalence of MA use, characteristics of the users and the control measures.

METHODS

A descriptive cross-sectional survey research design was conducted from May through November 2023 among adolescents/adults at the age bracket of 15-64 years in the five states of south east, Nigeria. Three hundred and seventy-one (371) respondents were recruited using purposive/convenience sampling methods. A semi structured questionnaire was the instrument used. Data were analyzed using percentage, bivariate and multivariate logistics regression statistics. The Prevalence of MA was determined using percentages whereas the factors that are associated with MA use were expressed using multivariate logistics regression statistics AORs and 95%CIs. The level of significance was set at P < 0.05.

RESULTS

The prevalence of Methamphetamine (Mkpurummiri) was (21.8%). The most common reason for MA use was depression (86.5%), the most common route of administration was inhalation (64.9%). The most common characteristic of MA (Mkpurummiri) user was aggressive/violent behaviour (94.1%).The control measures were self-control (92.2%), parental monitoring (85.7%), drug education (83.1%) and legal control (80.8%). The multivariate logistics regression statistics AOR shows that off-campus were 3 times (AOR = 0.298; CI = 0.12-0.73 P = 0.008), family house 4 times (AOR = 0.241; CI = 0.09-0.65; P = 0.005 ≤ 0.05 ) less likely than on-campus to predict MA use. Recently married were 3.25 times (aOR = 3.25; CI = 1.47-7.18), divorced 3.45 times (aOR = 3.45; CI = 1.23-9.58), polygamy 2.3 times (aOR = 2.3; CI = 1.08-4.90; P = 0.031 ≤ 0.05 ), tradition 4.44 times (aOR = 4.44; CI = 1.77-11.15; P = 0.001 ≤ 0.05 ) , more likely than others to use MA.

CONCLUSIONS

MA use prevalence was relatively high, and marital status, living arrangements, family type and religion were the predictors. These findings underscore the need for concerted effort among the relevant government agencies, community stakeholders, families, religious bodies and school authorities to designing MA use policy/laws with special focus on adopting the punitive measure used in checking cocaine users. This may help to arrest and prosecute the manufacturers, distributors and users of MA.

Association between serum catecholamine levels and VNTR polymorphism in the promoter region of the monoamine oxidase A gene in forensic autopsy cases

Monoamine oxidase A (MAOA) catalyzes oxidative deamination of catecholamines. A functional variable number tandem repeat (VNTR) polymorphism in the promoter region of the MAOA gene has been previously reported. In the present study, we measured serum adrenaline (Adr), noradrenaline (Nad), and dopamine (DA) levels in 90 male and 34 female Japanese autopsy cases in which amphetamines or psychotropic drugs were not detected.We examined the frequencies of MAOA-uVNTR alleles in these cases and investigated the effects of the MAOA-uVNTR polymorphism on serum Adr, Nad, and DA levels. Evaluation indicated no significant association between MAOA-uVNTR polymorphism and serum Adr, Nad, or DA levels in males, although a significant association between MAOA-uVNTR polymorphism and serum Adr and DA levels were observed in females. Females with the 3/3 genotype had higher serum Adr and DA levels than those with a 4-repeat allele (3/4 and 4/4 genotypes) (p = 0.048 and 0.020, respectively). There was no significant association between MAOA-uVNTR polymorphism and serum Nad levels in females. The present study indicates that MAOA-uVNTR polymorphism influences serum Adr and DA levels only in females.

Adolescent stress differentially modifies dopamine and norepinephrine release in the medial prefrontal cortex of adult rats

Adolescent stress (AS) has been associated with higher vulnerability to psychiatric disorders such as schizophrenia, depression, or drug dependence. Moreover, the alteration of brain catecholamine (CAT) transmission in the medial prefrontal cortex (mPFC) has been found to play a major role in the etiology of psychiatric disturbances. We investigated the effect of adolescent stress on CAT transmission in the mPFC of freely moving adult rats because of the importance of this area in the etiology of psychiatric disorders, and because CAT transmission is the target of a relevant group of drugs used in the therapy of depression and psychosis. We assessed basal dopamine (DA) and norepinephrine (NE) extracellular concentrations (output) by brain microdialysis in in the mPFC of adult rats that were exposed to chronic mild stress in adolescence. To ascertain the role of an altered release or reuptake, we stimulated DA and NE output by administering either different doses of amphetamine (0.5 and 1.0 mg / kg s.c.), which by a complex mechanism determines a dose dependent increase in the CAT output, or reboxetine (10 mg/kg i.p.), a selective NE reuptake inhibitor. The results showed the following: (i) basal DA output in AS rats was lower than in controls, while no difference in basal NE output was observed; (ii) amphetamine, dose dependently, stimulated DA and NE output to a greater extent in AS rats than in controls; (iii) reboxetine stimulated NE output to a greater extent in AS rats than in controls, while no difference in stimulated DA output was observed between the two groups. These results show that AS determines enduring effects on DA and NE transmission in the mPFC and might lead to the occurrence of psychiatric disorders or increase the vulnerability to drug addiction.

Emission of 50-kHz ultrasonic vocalizations stimulated by antiparkinsonian dopaminomimetic drugs in hemiparkinsonian rats is associated with neuronal activation in subcortical regions that regulate the affective state

Dopamine replacement therapy (DRT) of Parkinson's disease (PD) may trigger non-motor complications, some of which affect hedonic homeostatic regulation. Management of iatrogenic alterations in the affective state in PD is unsatisfactory, partly because of the limitations in the experimental models that are used in the preclinical investigation of the neurobiology and therapy of these alterations. In this connection, we recently employed a new experimental approach consisting in measuring the emission of 50-kHz ultrasonic vocalizations (USVs), a marker of positive affect, in hemiparkinsonian rats treated with drugs used in the DRT of PD. To further strengthen our approach, we here evaluated how the acute and repeated (× 5, on alternate days) administration of apomorphine (2 mg/kg, i.p.) or L-3,4-dihydroxyphenilalanine (L-DOPA, 12 mg/kg, i.p.) modified the immunoreactivity for Zif-268, a marker of neuronal activation, in the nucleus accumbens (NAc), caudate-putamen (CPu) and medial prefrontal cortex (mPFC), which are brain regions that regulate emotional states and drugs' affective properties. Acute and repeated treatment with either apomorphine or L-DOPA stimulated the emission of 50-kHz USVs in hemiparkinsonian rats, and this effect was paired with increased Zif-268 immunoreactivity in the NAc and CPu, but not mPFC. These findings indicate that subcortical and cortical regions may differently regulate the emission of 50-kHz USVs in hemiparkinsonian rats treated with dopaminergic drugs used in the DRT of PD. Moreover, they provide further evidence that measuring 50-kHz USV emissions in hemiparkinsonian rats may be a relevant approach to investigate at the preclinical level the affective properties of antiparkinsonian drugs.

Ultra-low doses of methamphetamine suppress 5-hydroxytryptophan-induced head-twitch response in mice during aging

The head-twitch response (HTR) in mice is considered a behavioral assay for activation of 5-HT2A receptors in rodents. It can be evoked by direct-acting 5-HT2A receptor agonists such as (±)-2,5-dimethoxy-4-iodoamphetamine, 5-hydroxytryptamine precursors [e.g. 5-hydroxytryptophan (5-HTP)], and selective 5-hydroxytryptamine releasers (e.g. d-fenfluramine). The nonselective monoamine releaser methamphetamine by itself does not produce the HTR but can suppress both (±)-2,5-dimethoxy-4-iodoamphetamine- and d-fenfluramine-evoked HTRs across ages via concomitant activation of the inhibitory serotonergic 5-HT1A or adrenergic α2 receptors. Currently, we investigated: (1) the ontogenic development of 5-HTP-induced HTR in 20-, 30-, and 60-day-old mice; (2) whether pretreatment with ultra-low doses of methamphetamine (0.1, 0.25, and 0.5 mg/kg, intraperitoneally) can suppress the frequency of 5-HTP-induced HTR at different ages; and (3) whether the inhibitory serotonergic 5-HT1A or adrenergic α2 receptors may account for the potential inhibitory effect of methamphetamine on 5-HTP-induced HTR. In the presence of a peripheral decarboxylase inhibitor (carbidopa), 5-HTP produced maximal frequency of HTRs in 20-day-old mice which rapidly subsided during aging. Methamphetamine dose-dependently suppressed 5-HTP-evoked HTR in 20- and 30-day-old mice. The selective 5-HT1A-receptor antagonist WAY 100635 reversed the inhibitory effect of methamphetamine on 5-HTP-induced HTR in 30-day-old mice, whereas the selective adrenergic α2-receptor antagonist RS 79948 failed to reverse methamphetamine's inhibition at any tested age. These findings suggest an ontogenic rationale for methamphetamine's inhibitory 5-HT1A receptor component of action in its suppressive effect on 5-HTP-induced HTR during development which is not maximally active at a very early age.

Neurological Effects of Stimulants and Hallucinogens

In this article, we will discuss the history, pharmacodynamics, and neurotoxicity of psychostimulants and hallucinogens. The drugs discussed are widely used and have characteristic toxidromes and potential for neurological injuries with which the practicing clinician should be familiar. Psychostimulants are a class of drugs that includes cocaine, methamphetamine/amphetamines, and cathinones, among others, which produce a crescendoing euphoric high. Seizures, ischemic and hemorrhagic strokes, rhabdomyolysis, and a variety of movement disorders are commonly encountered in this class. Hallucinogens encompass a broad class of drugs, in which the user experiences hallucinations, altered sensorium, distorted perception, and cognitive dysfunction. The experience can be unpredictable and dysphoric, creating a profound sense of anxiety and panic in some cases. Recognizing the associated neurotoxicities and understanding the appropriate management is critical in caring for these patient populations. Several of these agents are not detectable by standard clinical laboratory analysis, making identification and diagnosis an even greater challenge.

Dopamine reuptake and inhibitory mechanisms in human dopamine transporter

The dopamine transporter has a crucial role in regulation of dopaminergic neurotransmission by uptake of dopamine into neurons and contributes to the abuse potential of psychomotor stimulants1-3. Despite decades of study, the structure, substrate binding, conformational transitions and drug-binding poses of human dopamine transporter remain unknown. Here we report structures of the human dopamine transporter in its apo state, and in complex with the substrate dopamine, the attention deficit hyperactivity disorder drug methylphenidate, and the dopamine-uptake inhibitors GBR12909 and benztropine. The dopamine-bound structure in the occluded state precisely illustrates the binding position of dopamine and associated ions. The structures bound to drugs are captured in outward-facing or inward-facing states, illuminating distinct binding modes and conformational transitions during substrate transport. Unlike the outward-facing state, which is stabilized by cocaine, GBR12909 and benztropine stabilize the dopamine transporter in the inward-facing state, revealing previously unseen drug-binding poses and providing insights into how they counteract the effects of cocaine. This study establishes a framework for understanding the functioning of the human dopamine transporter and developing therapeutic interventions for dopamine transporter-related disorders and cocaine addiction.

The influence of drug class on reward in substance use disorders

In the United States, the societal costs associated with drug use surpass $500 billion annually. The rewarding and reinforcing properties that drive the use of these addictive substances are typically examined concerning the neurobiological effects responsible for their abuse potential. In this review, terms such as "abuse potential," "drug," and "addictive properties" are used due to their relevance to the methodological, theoretical, and conceptual framework for understanding the phenomenon of drug-taking behavior and the associated body of preclinical and clinical literature. The use of these terms is not intended to cast aspersions on individuals with substance use disorders (SUD). Understanding what motivates substance use has been a focus of SUD research for decades. Much of this corpus of work has focused on the shared effects of each drug class to increase dopaminergic transmission within the central reward pathways of the brain, or the "reward center." However, the precise influence of each drug class on dopamine signaling, and the extent thereof, differs considerably. Furthermore, the aforementioned substances have effects on several neurobiological targets that mediate and modulate their addictive properties. The current manuscript sought to review the influence of drug class on the rewarding effects of each of the major pharmacological classes of addictive drugs (i.e., psychostimulants, opioids, nicotine, alcohol, and cannabinoids). Our review suggests that even subtle differences in drug effects can result in significant variability in the subjective experience of the drug, altering rewarding and other reinforcing effects. Additionally, this review will argue that reward (i.e., the attractive and motivational property of a stimulus) alone is not sufficient to explain the abuse liability of these substances. Instead, abuse potential is best examined as a function of both positive and negative reinforcing drug effects (i.e., stimuli that the subject will work to attain and stimuli that the subject will work to end or avoid, respectively). Though reward is central to drug use, the factors that motivate and maintain drug taking are varied and complex, with much to be elucidated.

Methamphetamine and REM sleep deprivation interact to affect behavioral performance in adult and adolescent rats

Drug addiction may result in sleep problems. Importantly, sleep deprivation (SD) is known as an important risk factor for relapse to drug abuse as SD mimics the effects of psychostimulants on dopamine system of the brain. Moreover, aging may affect sleep and drug addiction. This study, therefore, set out to assess the effects of methamphetamine (METH) and REM sleep deprivation (RSD) on locomotor activity, anxiety-like behavior and spatial memory in adult and adolescent rats. Adult and adolescent male Wistar rats received a neurotoxic METH regimen; four subcutaneous injections of 6 mg/kg, at 2 h intervals. Five days later, the animals underwent a 48-h RSD episode using the multiple platforms method. They were then examined using the open field (OF), elevated plus maze (EPM) and Y-maze tasks. We found that the METH and RSD paradigms showed synergistic effects to increase locomotion and risk-taking behavior in both adult and adolescent animals, while only adolescent rats revealed RSD-induced anxiety-like behavior. Moreover, adolescent animals revealed greater sensitization for vertical activity following METH plus RSD episode. In addition, METH and RSD paradigms revealed synergistic effects to impair spatial working memory, but neither METH nor RSD alone affected performance of animals in the Y-maze task. Our findings may indicate that there are important relationships between METH and RSD to induce hyperlocomotion, risk-taking behavior and spatial memory impairment, particularly in adolescent animals. Moreover, it seems that adolescent rats may be more susceptible to anxiety-like behavior and hyperlocomotion than adults.

Neuromarkers in addiction: definitions, development strategies, and recent advances

Substance use disorders (SUDs) are the most costly and prevalent psychiatric conditions. Recent calls emphasize a need for biomarkers-measurable, stable indicators of normal and abnormal processes and response to treatment or environmental agents-and, in particular, brain-based neuromarkers that will advance understanding of the neurobiological basis of SUDs and clinical practice. To develop neuromarkers, researchers must be grounded in evidence that a putative marker (i) is sensitive and specific to the psychological phenomenon of interest, (ii) constitutes a predictive model, and (iii) generalizes to novel observations (e.g., through internal cross-validation and external application to novel data). These neuromarkers may be used to index risk of developing SUDs (susceptibility), classify individuals with SUDs (diagnostic), assess risk for progression to more severe pathology (prognostic) or index current severity of pathology (monitoring), detect response to treatment (response), and predict individualized treatment outcomes (predictive). Here, we outline guidelines for developing and assessing neuromarkers, we then review recent advances toward neuromarkers in addiction neuroscience centering our discussion around neuromarkers of craving-a core feature of SUDs. In doing so, we specifically focus on the Neurobiological Craving Signature (NCS), which show great promise for meeting the demand of neuromarkers.

Structural insights into vesicular monoamine storage and drug interactions

Biogenic monoamines-vital transmitters orchestrating neurological, endocrinal and immunological functions1-5-are stored in secretory vesicles by vesicular monoamine transporters (VMATs) for controlled quantal release6,7. Harnessing proton antiport, VMATs enrich monoamines around 10,000-fold and sequester neurotoxicants to protect neurons8-10. VMATs are targeted by an arsenal of therapeutic drugs and imaging agents to treat and monitor neurodegenerative disorders, hypertension and drug addiction1,8,11-16. However, the structural mechanisms underlying these actions remain unclear. Here we report eight cryo-electron microscopy structures of human VMAT1 in unbound form and in complex with four monoamines (dopamine, noradrenaline, serotonin and histamine), the Parkinsonism-inducing MPP+, the psychostimulant amphetamine and the antihypertensive drug reserpine. Reserpine binding captures a cytoplasmic-open conformation, whereas the other structures show a lumenal-open conformation stabilized by extensive gating interactions. The favoured transition to this lumenal-open state contributes to monoamine accumulation, while protonation facilitates the cytoplasmic-open transition and concurrently prevents monoamine binding to avoid unintended depletion. Monoamines and neurotoxicants share a binding pocket that possesses polar sites for specificity and a wrist-and-fist shape for versatility. Variations in this pocket explain substrate preferences across the SLC18 family. Overall, these structural insights and supporting functional studies elucidate the mechanism of vesicular monoamine transport and provide the basis to develop therapeutics for neurodegenerative diseases and substance abuse.

Microdialysis coupled with droplet microfluidics and mass spectrometry for determination of neurotransmitters in vivo with high temporal resolution

Monitoring the concentration fluctuations of neurotransmitters in vivo is valuable for elucidating the chemical signals that underlie brain functions. Microdialysis sampling is a widely used tool for monitoring neurochemicals in vivo. The volume requirements of most techniques that have been coupled to microdialysis, such as HPLC, result in fraction collection times of minutes, thus limiting the temporal resolution possible. Further the time of analysis can become long for cases where many fractions are collected. Previously we have used direct analysis of dialysate by low-flow electrospray ionization-tandem mass spectrometry (ESI-MS/MS) on a triple quadrupole mass spectrometer to monitor acetylcholine, glutamate, and γ-amino-butyric acid to achieve multiplexed in vivo monitoring with temporal resolution of seconds. Here, we have expanded this approach to adenosine, dopamine, and serotonin. The method achieved limits of detection down to 2 nM, enabling basal concentrations of all these compounds, except serotonin, to be measured in vivo. Comparative analysis with LC-MS/MS showed accurate results for all compounds except for glutamate, possibly due to interference for this compound in vivo. Pairing this analysis with droplet microfluidics yields 11 s temporal resolution and can generate dialysate fractions down to 3 nL at rates up to 3 fractions per s from a microdialysis probe. The system is applied to multiplexed monitoring of neurotransmitter dynamics in response to stimulation by 100 mM K+ and amphetamine. These applications demonstrate the suitability of the droplet ESI-MS/MS method for monitoring short-term dynamics of up to six neurotransmitters simultaneously.

Amphetamine Exposure during Embryogenesis Alters Expression and Function of Tyrosine Hydroxylase and the Vesicular Monoamine Transporter in Adult C. elegans

Amphetamines (Amph) are psychostimulants broadly used as physical and cognitive enhancers. However, the long-term effects of prenatal exposure to Amph have been poorly investigated. Here, we show that continuous exposure to Amph during early development induces long-lasting changes in histone methylation at the C. elegans tyrosine hydroxylase (TH) homolog cat-2 and the vesicular monoamine transporter (VMAT) homologue cat-1 genes. These Amph-induced histone modifications are correlated with enhanced expression and function of CAT-2/TH and higher levels of dopamine, but decreased expression of CAT-1/VMAT in adult animals. Moreover, while adult animals pre-exposed to Amph do not show obvious behavioral defects, when challenged with Amph they exhibit Amph hypersensitivity, which is associated with a rapid increase in cat-2/TH mRNA. Because C. elegans has helped reveal neuronal and epigenetic mechanisms that are shared among animals as diverse as roundworms and humans, and because of the evolutionary conservation of the dopaminergic response to psychostimulants, data collected in this study could help us to identify the mechanisms through which Amph induces long-lasting physiological and behavioral changes in mammals.

Vesicular monoamine transporter-2 inhibitor JPC-141 prevents methamphetamine-induced dopamine toxicity and blocks methamphetamine self-administration in rats

Previous research has demonstrated therapeutic potential for VMAT2 inhibitors in rat models of methamphetamine use disorder. Here, we report on the neurochemical and behavioral effects of 1-(2-methoxyphenethyl)-4-phenethypiperazine (JPC-141), a novel analog of lobelane. JPC-141 potently inhibited (Ki = 52 nM) [3H]dopamine uptake by VMAT2 in striatal vesicles with 50 to 250-fold greater selectivity for VMAT2 over dopamine, norepinephrine and serotonin plasmalemma transporters. Also, JPC-141 was 57-fold more selective for inhibiting VMAT2 over [3H]dofetilide binding to hERG channels expressed by HEK293, suggesting relatively low potential for cardiotoxicity. When administered in vivo to rats, JPC-141 prevented the METH-induced reduction in striatal dopamine content when given either prior to or after a high dose of METH, suggesting a reduction in METH-induced dopaminergic neurotoxicity. In behavioral assays, JPC-141 decreased METH-stimulated locomotor activity in METH-sensitized rats at doses of JPC-141 which did not alter locomotor activity in the saline control group. Moreover, JPC-141 specifically decreased iv METH self-administration at doses that had no effect on food-maintained responding. These findings support the further development of VMAT2 inhibitors as pharmacotherapies for individuals with methamphetamine use disorder.

Roles of cannabinoid CB1 and CB2 receptors in the modulation of psychostimulant responses

Addiction to psychostimulant drugs, such as cocaine, D-amphetamine, and methamphetamine, is a public health issue that substantially contributes to the global burden of disease. Psychostimulant drugs promote an increase in dopamine levels within the mesocorticolimbic system, which is central to the rewarding properties of such drugs. Cannabinoid receptors (CB1R and CB2R) are expressed in the main areas of this system and implicated in the neuronal mechanisms underlying the rewarding effect of psychostimulant drugs. Here, we reviewed studies focusing on pharmacological intervention targeting cannabinoid CB1R and CB2R and their interaction in the modulation of psychostimulant responses.

Restoration of norepinephrine release, cognitive performance, and dendritic spines by amphetamine in aged rat brain

Age-related dysfunctions in specific neurotransmitter systems likely play an important role in cognitive decline even in its most subtle forms. Therefore, preservation or improvement of cognition via augmentation of neurotransmission is a potential therapeutic strategy to prevent further cognitive deficits. Here we identified a particular neuronal vulnerability in the aged Fischer 344 rat brain, an animal model of neurocognitive aging. Specifically, we demonstrated a marked impairment in glutamate-stimulated release of norepinephrine (NE) in the hippocampus and cerebral cortex of aged rats, and established that this release was mediated by N-methyl-D-aspartate (NMDA) receptors. Further, we also demonstrated that this decrease in NE release is fully rescued by the psychostimulant drug amphetamine (AMPH). Moreover, we showed that AMPH increases dendritic spine maturation, and importantly shows preclinical efficacy in restoring memory deficits in the aged rat through its actions to potentiate NE neurotransmission at β-adrenergic receptors. Taken together, our results suggest that deficits in glutamate-stimulated release of NE may contribute to and possibly be a determinant of neuronal vulnerability underlying cognitive decline during aging, and that these deficits can be corrected with currently available drugs. Overall these studies suggest that repurposing of psychostimulants for age-associated cognitive deficits is a potential avenue to delay or prevent cognitive decline and/or frank dementia later in life.

Comparison of the Efficacy of Anti-Obesity Medications in Real-World Practice

Purpose

Anti-obesity medications (AOMs), along with lifestyle interventions, are effective means of inducing and maintaining weight loss in patients with obesity. Although the efficacy of AOMs has been reported, there have been no direct comparisons of these drugs. Therefore, in the present study, we aimed to compare the efficacy of all the AOMs available in Korea in a real-world setting.

Patients and Methods

The body weight and composition of 205 adults treated with phentermine, phentermine/topiramate, liraglutide, naltrexone/bupropion, lorcaserin, or orlistat for at least 6 months were analyzed at 2 month intervals. The prevalence of the achievement of a ≥5% weight loss and the changes in body composition were compared between participants using each AOM at each visit.

Results

A total of 132 (64.4%) participants achieved ≥5% weight loss within 6 months (prevalence of ≥5% weight loss after 6 months: phentermine, 87.2%; phentermine/topiramate, 67.7%; liraglutide, 58.1%; naltrexone/bupropion, 35.3%; lorcaserin, 75%; orlistat, 50%). At each visit, after adjustment for age, sex, and baseline body weight, phentermine use was associated with a significantly higher prevalence of ≥5% weight loss than the use of the other AOMs, except for liraglutide. There were significant differences in the body weight, body mass index and body fat mass among the AOM groups by visit (P for interaction <0.05), but not in their waist circumference, skeletal muscle mass, percentage body fat, or visceral fat area.

Conclusion

All the AOMs were effective at inducing and maintaining weight loss, in the absence of significant changes in muscle mass, over a 6 month period, and the short-term use of phentermine and the long-term use of phentermine/topiramate or liraglutide would be practical choices for the treatment of obesity. However, further, large-scale studies are necessary to confirm these findings.

Prenatal and postnatal methamphetamine exposure alters prefrontal cortical gene expression and behavior in mice

Methamphetamine is a highly abused psychostimulant that substantially impacts public health. Prenatal and postnatal methamphetamine exposure alters gene expression, brain development, and behavior in the offspring, although the underlying mechanisms are not fully defined. To assess these adverse outcomes in the offspring, we employed a mouse model of prenatal and postnatal methamphetamine exposure. Juvenile offspring were behaviorally assessed on the open field, novel object recognition, Y-maze, and forced swim tests. In addition, RNA sequencing was used to explore potential alterations in prefrontal cortical gene expression. We found that methamphetamine-exposed mice exhibited decreased locomotor activity and impaired cognitive performance. In addition, differential expression of genes involved in neurotransmission, synaptic plasticity, and neuroinflammation were found with notable changes in dopaminergic signaling pathways. These data suggest potential neural and molecular mechanisms underlying methamphetamine-exposed behavioral changes. The altered expression of genes involved in dopaminergic signaling and synaptic plasticity highlights potential targets for therapeutic interventions for substance abuse disorders and related psychiatric complications.

Stimulant Drugs and Stimulant Use Disorder

The authors aim to summarize several key points of stimulant drugs and stimulant use disorder, including their indications, short-term and long-term adverse effects, current treatment strategies, and association with opioid medications. The global prevalence of stimulant use has seen annual increase in the last decade. Multiple studies have shown that stimulant use and stimulant use disorder are associated with a range of individual and public health issues. Stimulant misuse has led to a significant increase of overdose deaths in the United States.

Post-translational mechanisms in psychostimulant-induced neurotransmitter efflux

The availability of monoamine neurotransmitters in the brain is under the control of dopamine, norepinephrine, and serotonin transporters expressed on the plasma membrane of monoaminergic neurons. By regulating transmitter levels these proteins mediate crucial functions including cognition, attention, and reward, and dysregulation of their activity is linked to mood and psychiatric disorders of these systems. Amphetamine-based transporter substrates stimulate non-exocytotic transmitter efflux that induces psychomotor stimulation, addiction, altered mood, hallucinations, and psychosis, thus constituting a major component of drug neurochemical and behavioral outcomes. Efflux is under the control of transporter post-translational modifications that synergize with other regulatory events, and this review will summarize our knowledge of these processes and their role in drug mechanisms.

Amphetamine increases vascular permeability by modulating endothelial actin cytoskeleton and NO synthase via PAR-1 and VEGF-R

Abuse of amphetamine-type stimulants is linked to cardiovascular adverse effects like arrhythmias, accelerated atherosclerosis, acute coronary syndromes and sudden cardiac death. Excessive catecholamine release following amphetamine use causes vasoconstriction and vasospasms, over time leading to hypertension, endothelial dysfunction or even cardiotoxicity. However, immediate vascular pathomechanisms related to amphetamine exposure, especially endothelial function, remain incompletely understood and were analyzed in this study. Pharmaco-pathological effects of acute d-amphetamine-sulfate (DAM) were investigated ex vivo using contraction-force measurements of rat carotid artery rings and in vitro using label-free, real-time electrochemical impedance spectroscopy (EIS) on endothelial and smooth muscle cells. Specific receptor and target blocking was used to identify molecular targets and to characterize intracellular signaling. DAM induced vasodilation represented by 29.3±2.5% decrease in vascular tone (p<0.001) involving vascular endothelial growth factor receptor (VEGF-R) and protease activated receptor 1 (PAR-1). EIS revealed that DAM induces endothelial barrier disruption (-75.9±1.1% of initial cellular impedance, p<0.001) also involving VEGF-R and PAR-1. Further, in response to DAM, Rho-associated protein kinase (ROCK) mediated reversible contraction of actin cytoskeleton resulting in endothelial barrier disruption. Dephosphorylation of Serine1177 (-50.8±3.7%, p<0.001) and Threonine495 (-44.8±6.5%, p=0.0103) of the endothelial NO synthase (eNOS) were also observed. Blocking of VEGF-R and PAR-1 restored baseline eNOS Threonine495 phosphorylation. DAM induced vasodilation, enhanced vascular permeability and actin cytoskeleton contraction and induced eNOS hypophosphorylation involving VEGF-R, PAR-1 and ROCK. These results may contribute to a better understanding of severe adverse cardiovascular effects in amphetamine abuse.

Dopamine Signaling in Substantia Nigra and Its Impact on Locomotor Function-Not a New Concept, but Neglected Reality

The mechanistic influences of dopamine (DA) signaling and impact on motor function are nearly always interpreted from changes in nigrostriatal neuron terminals in striatum. This is a standard practice in studies of human Parkinson's disease (PD) and aging and related animal models of PD and aging-related parkinsonism. However, despite dozens of studies indicating an ambiguous relationship between changes in striatal DA signaling and motor phenotype, this perseverating focus on striatum continues. Although DA release in substantia nigra (SN) was first reported almost 50 years ago, assessment of nigral DA signaling changes in relation to motor function is rarely considered. Whereas DA signaling has been well-characterized in striatum at all five steps of neurotransmission (biosynthesis and turnover, storage, release, reuptake, and post-synaptic binding) in the nigrostriatal pathway, the depth of such interrogations in the SN, outside of cell counts, is sparse. However, there is sufficient evidence that these steps in DA neurotransmission in the SN are operational and regulated autonomously from striatum and are present in human PD and aging and related animal models. To complete our understanding of how nigrostriatal DA signaling affects motor function, it is past time to include interrogation of nigral DA signaling. This brief review highlights evidence that changes in nigral DA signaling at each step in DA neurotransmission are autonomous from those in striatum and changes in the SN alone can influence locomotor function. Accordingly, for full characterization of how nigrostriatal DA signaling affects locomotor activity, interrogation of DA signaling in SN is essential.

Nalmefene attenuates reinstatement of methamphetamine-seeking behavior in rats through group II metabotropic glutamate receptors (mGluR2/3)

Nalmefene, an analog to naltrexone, is an antagonist at the μ opioid receptor and a partial agonist at the κ opioid receptor. Both agents are approved for the treatment of alcohol use disorder and opioid addiction. Here, we evaluated the potential of nalmefene for treating psychostimulant dependence using a methamphetamine (METH) self-administration rat model. Rats were trained to press a lever for 0.02-mg intravenous METH infusions paired with drug-associated cues (light and tone) under a fixed ratio 1 schedule. After a 10-day METH self-administration acquisition phase, rats underwent extinction training. A reinstatement test was conducted after fulfilment of the extinction criterion under saline infusions. Re-exposure to METH-associated cues or a priming injection of METH (1.0 mg/kg, i.p.) significantly reinstated METH-seeking behaviors. Pretreatment with nalmefene (10 mg/kg, i.p.) immediately before reinstatement tests significantly attenuated the METH-seeking behaviors induced by both cues and METH priming injection. To investigate the mechanism of effect of nalmefene, we also tested the ability of a group II metabotropic glutamate receptors (mGluR2/3) antagonist, LY341495, to the ameliorating effects of nalmefene. Pretreatment with LY341495 (1.0 mg/kg, i.p.) before nalmefene administration antagonized the effect of nalmefene on reinstatement. LY341495 alone did not affect the reinstatement of lever pressing. We found that nalmefene attenuates METH-seeking behaviors during withdrawal, and this attenuation of reinstatement is mediated by the activation of mGluR2/3. The present findings suggest that nalmefene could decrease incentive motivation for drug use in psychostimulant dependence.

Amphetamine Induces Sex-Dependent Loss of the Striatal Dopamine Transporter in Sensitized Mice

Dopamine transporter (DAT) controls dopamine signaling in the brain through the reuptake of synaptically released dopamine. DAT is a target of abused psychostimulants such as amphetamine (Amph). Acute Amph administration induces transient DAT endocytosis, which, among other Amph effects on dopaminergic neurons, elevates extracellular dopamine. However, the effects of repeated Amph abuse, leading to behavioral sensitization and drug addiction, on DAT are unknown. Hence, we developed a 14 d Amph-sensitization protocol in knock-in mice expressing HA-epitope-tagged DAT (HA-DAT) and investigated the effects of Amph challenge on sensitized HA-DAT animals. The Amph challenge resulted in the highest locomotor activity on Day 14 in both sexes, which was sustained for 1 h in male but not female mice. Strikingly, significant (by 30-60%) loss of the HA-DAT protein in the striatum was caused by the Amph challenge of sensitized males but not females. Amph also reduced V max of dopamine transport in the striatal synaptosomes of males without changing K m values. Consistently, immunofluorescence microscopy revealed a significant increase of HA-DAT colocalization with the endosomal protein VPS35 only in Amph-challenged males. Amph-induced loss of striatal HA-DAT in sensitized mice was blocked by chloroquine, vacuolin-1, and inhibitor of Rho-associated kinases ROCK1/2, indicative of the involvement of endocytic trafficking in the DAT protein loss. Interestingly, an apparent degradation of HA-DAT protein was observed in the nucleus accumbens and not in the dorsal striatum. We propose that Amph challenge in sensitized mice triggers Rho-mediated endocytosis and post-endocytic trafficking of DAT in a brain-region-specific and sex-dependent manner.

It's all about making new contacts: How being metabotropic and phasicity help D1-like receptors promote LTP in the PFC

D1-like receptors have two important qualities, they are all metabotropic and they activate with phasic dopamine. After analyzing the molecular implications of each of these qualities separately and then combining them for the specific case of the prefrontal cortex, we propose a model that explains why long term potentiation in this cortical area depends on the amount of contact between D1-like receptors and dopamine. This simple model also explains why in order to promote long term potentiation, dopamine transporters should be scarce in the prefrontal cortex. Additionally, it explains why stimulants like methamphetamine could have such detrimental cognitive effects on regular substance consumers.

Inhibition of LRRK2 kinase activity rescues deficits in striatal dopamine physiology in VPS35 p.D620N knock-in mice

Dysregulation of dopamine neurotransmission profoundly affects motor, motivation and learning behaviors, and can be observed during the prodromal phase of Parkinson's disease (PD). However, the mechanism underlying these pathophysiological changes remains to be elucidated. Mutations in vacuolar protein sorting 35 (VPS35) and leucine-rich repeat kinase 2 (LRRK2) both lead to autosomal dominant PD, and VPS35 and LRRK2 may physically interact to govern the trafficking of synaptic cargos within the endo-lysosomal network in a kinase-dependent manner. To better understand the functional role of VPS35 and LRRK2 on dopamine physiology, we examined Vps35 haploinsufficient (Haplo) and Vps35 p.D620N knock-in (VKI) mice and how their behavior, dopamine kinetics and biochemistry are influenced by LRRK2 kinase inhibitors. We found Vps35 p.D620N significantly elevates LRRK2-mediated phosphorylation of Rab10, Rab12 and Rab29. In contrast, Vps35 haploinsufficiency reduces phosphorylation of Rab12. While striatal dopamine transporter (DAT) expression and function is similarly impaired in both VKI and Haplo mice, that physiology is normalized in VKI by treatment with the LRRK2 kinase inhibitor, MLi-2. As a corollary, VKI animals show a significant increase in amphetamine induced hyperlocomotion, compared to Haplo mice, that is also abolished by MLi-2. Taken together, these data show Vps35 p.D620N confers a gain-of-function with respect to LRRK2 kinase activity, and that VPS35 and LRRK2 functionally interact to regulate DAT function and striatal dopamine transmission.

Ligand recognition and G-protein coupling of trace amine receptor TAAR1

Trace-amine-associated receptors (TAARs), a group of biogenic amine receptors, have essential roles in neurological and metabolic homeostasis1. They recognize diverse endogenous trace amines and subsequently activate a range of G-protein-subtype signalling pathways2,3. Notably, TAAR1 has emerged as a promising therapeutic target for treating psychiatric disorders4,5. However, the molecular mechanisms underlying its ability to recognize different ligands remain largely unclear. Here we present nine cryo-electron microscopy structures, with eight showing human and mouse TAAR1 in a complex with an array of ligands, including the endogenous 3-iodothyronamine, two antipsychotic agents, the psychoactive drug amphetamine and two identified catecholamine agonists, and one showing 5-HT1AR in a complex with an antipsychotic agent. These structures reveal a rigid consensus binding motif in TAAR1 that binds to endogenous trace amine stimuli and two extended binding pockets that accommodate diverse chemotypes. Combined with mutational analysis, functional assays and molecular dynamic simulations, we elucidate the structural basis of drug polypharmacology and identify the species-specific differences between human and mouse TAAR1. Our study provides insights into the mechanism of ligand recognition and G-protein selectivity by TAAR1, which may help in the discovery of ligands or therapeutic strategies for neurological and metabolic disorders.

Single-nucleus transcriptome profiling of prefrontal cortex induced by chronic methamphetamine treatment

Background

Methamphetamine (METH) addiction causes a huge burden on society. The prefrontal cortex (PFC), associated with emotion and cognitive behaviours, is also involved in addiction neurocircuitry. Although bulk RNA sequencing has shown METH-induced gene alterations in the mouse PFC, the impact on different cell types remains unknown.

Aims

To clarify the effects of METH treatment on different cell types of the PFC and the potential pathways involved in METH-related disorders.

Methods

We performed single-nucleus RNA sequencing (snRNA-seq) to examine the transcriptomes of 20 465 nuclei isolated from the PFC of chronic METH-treated and control mice. Main cell types and differentially expressed genes (DEGs) were identified and confirmed by RNA fluorescence in situ hybridization(FISH).

Results

Six main cell types were identified depending on the single-cell nucleus sequencing; of particular interest were the mature oligodendrocytes in the PFC. The DEGs of mature oligodendrocytes were enriched in the myelin sheath, adenosine triphosphate (ATP) metabolic process, mitochondrial function and components, and so on. The messenger RNA levels of Aldoc and Atp5l (FISH) and the protein level of the mitochondrial membrane pore subunit TOM40 (immunofluorescence) decreased in the mature oligodendrocytes. Fast blue staining and transmission electron microscopy image indicated myelin damage, and the myelin thickness decreased in METH brains.

Conclusions

snRNA-seq reveals altered transcriptomes of different cell types in mouse PFC induced by chronic METH treatment, underscoring potential relationships with psychiatric disorders.

Immunity on ice: The impact of methamphetamine on peripheral immunity

Methamphetamine (METH) regulation of the dopamine transporter (DAT) and central nervous system (CNS) dopamine transmission have been extensively studied. However, our understanding of how METH influences neuroimmune communication and innate and adaptive immunity is still developing. Recent studies have shed light on the bidirectional communication between the CNS and the peripheral immune system. They have established a link between CNS dopamine levels, dopamine neuronal activity, and peripheral immunity. Akin to dopamine neurons in the CNS, a majority of peripheral immune cells also express DAT, implying that in addition to their effect in the CNS, DAT ligands such as methamphetamine may have a role in modulating peripheral immunity. For example, by directly influencing DAT-expressing peripheral immune cells and thus peripheral immunity, METH can trigger a feed-forward cascade that impacts the bidirectional communication between the CNS and peripheral immune system. In this review, we aim to discuss the current understanding of how METH modulates both innate and adaptive immunity and identify areas where knowledge gaps exist. These gaps will then be considered in guiding future research directions.

Catechol oxidase nanozyme based colorimetric sensors array for highly selective distinction among multiple catecholamines

In order to effectively monitor multiple catecholamine (CA) neurotransmitters with extreme similar structures, a rapid, sensitive and selective detection strategy has become an urgent problem to be solved. In this paper, a novel colorimetric sensors array based on CuNCs protected by various ligands such as tannic acid, ascorbic acid and polymethylacrylic acid (CuNCs@TA, CuNCs@AA and CuNCs@PMAA) was constructed. All of these CuNCs could mimic catechol oxidase to selective catalyze catechol-type analogues (such as CAs) to corresponding quinones along with color changes. Furthermore, experiments and theory calculations demonstrated that Cr6+-modification on the surface of CuNCs facilitated the steady-state kinetics of enzymatic activity. Based on these CuNCs as sensing probes, this sensors array can quickly detect different CAs (such as epinephrine (EP), including dopamine (DA), norepinephrine (NE) and l-dopa) with similar structures. When those analogues were added to the CuNC-based colorimetric array sensors, different absorbance changes were produced at 485 nm. Linear discriminant analysis (LDA) showed that the tri-probe colorimetric array sensors could recognize and distinguish these analogues, and corresponding binary and ternary mixtures could be well categorized. The value of Factor 1 of an array with varied CA concentrations had a good linear correlation, and the detection limit (LOD) was as low as 10-8∼10-9 mol/L. Four CA analogues in real samples were identified by CuNCs-based colorimetric array sensors. This work provides a fast and convenient experimental basis for monitoring the complex structure CAs neurotransmitters.

Structural and functional perspectives on interactions between synthetic cathinones and monoamine transporters

Synthetic cathinone derivatives comprise a family of psychoactive compounds structurally related to amphetamine. Over the last decade, clandestine chemists have synthesized a consistent stream of innovative cathinone derivatives to outpace governmental regulatory restrictions. Many of these unregulated substances are produced and distributed as designer drugs. Two of the principal chemical scaffolds exploited to expand the synthetic cathinone family are methcathinone and α-pyrrolidinopentiophenone (or α-pyrrolidinovalerophenone, α-PVP). These compounds' main physiological targets are monoamine transporters, where they promote addiction by potentiating dopaminergic neurotransmission. This chapter describes techniques used to study the pharmacodynamic properties of cathinones at monoamine transporters in vitro. Biochemical techniques described include uptake inhibition and release assays in rat brain synaptosomes and in mammalian expression systems. Electrophysiological techniques include current measurements using the voltage clamp technique. We describe a Ca2+ mobilization assay wherein voltage-gated Ca2+ channels function as reporters to study the action of synthetic cathinones at monoamine transporters. We discuss results from systematic structure-activity relationship studies on simple and complex cathinones at monoamine transporters with an emphasis on identifying structural moieties that modulate potency and selectivity at these transporters. Moreover, different profiles of selectivity at monoamine transporters directly predict compounds associated with behavioral and subjective effects within animals and humans. In conclusion, clarification of the structural aspects of compounds which modulate potency and selectivity at monoamine transporters is critical to identify and predict potential addictive drugs. This knowledge may allow prompt allocation of resources toward drugs that represent the greatest threats after drugs are identified by forensic laboratories.

Distinct and Dynamic Changes in the Temporal Profiles of Neurotransmitters in Drosophila melanogaster Brain following Volatilized Cocaine or Methamphetamine Administrations

Due to similarities in genetics, cellular response, and behavior, Drosophila is used as a model organism in addiction research. A well-described behavioral response examined in flies is the induced increase in locomotor activity after a single dose of volatilized cocaine (vCOC) and volatilized methamphetamine (vMETH), the sensitivity, and the escalation of the locomotor response after the repeated dose, the locomotor sensitization. However, knowledge about how vCOC and vMETH affect different neurotransmitter systems over time is scarce. We used LC-MS/MS to systematically examine changes in the concentration of neurotransmitters, metabolites and non-metabolized COC and METH in the whole head homogenates of male flies one to seven hours after single and double vCOC or vMETH administrations. vMETH leads to complex changes in the levels of examined substances over time, while vCOC strongly and briefly increases concentrations of dopamine, tyramine and octopamine followed by a delayed degradation into N-acetyl dopamine and N-acetyl tyramine. The first exposure to psychostimulants leads to significant and dynamic changes in the concentrations relative to the second administration when they are more stable over several hours. Further investigations are needed to understand neurochemical and molecular changes post-psychostimulant administration.

Specialized astrocytes mediate glutamatergic gliotransmission in the CNS

Multimodal astrocyte-neuron communications govern brain circuitry assembly and function1. For example, through rapid glutamate release, astrocytes can control excitability, plasticity and synchronous activity2,3 of synaptic networks, while also contributing to their dysregulation in neuropsychiatric conditions4-7. For astrocytes to communicate through fast focal glutamate release, they should possess an apparatus for Ca2+-dependent exocytosis similar to neurons8-10. However, the existence of this mechanism has been questioned11-13 owing to inconsistent data14-17 and a lack of direct supporting evidence. Here we revisited the astrocyte glutamate exocytosis hypothesis by considering the emerging molecular heterogeneity of astrocytes18-21 and using molecular, bioinformatic and imaging approaches, together with cell-specific genetic tools that interfere with glutamate exocytosis in vivo. By analysing existing single-cell RNA-sequencing databases and our patch-seq data, we identified nine molecularly distinct clusters of hippocampal astrocytes, among which we found a notable subpopulation that selectively expressed synaptic-like glutamate-release machinery and localized to discrete hippocampal sites. Using GluSnFR-based glutamate imaging22 in situ and in vivo, we identified a corresponding astrocyte subgroup that responds reliably to astrocyte-selective stimulations with subsecond glutamate release events at spatially precise hotspots, which were suppressed by astrocyte-targeted deletion of vesicular glutamate transporter 1 (VGLUT1). Furthermore, deletion of this transporter or its isoform VGLUT2 revealed specific contributions of glutamatergic astrocytes in cortico-hippocampal and nigrostriatal circuits during normal behaviour and pathological processes. By uncovering this atypical subpopulation of specialized astrocytes in the adult brain, we provide insights into the complex roles of astrocytes in central nervous system (CNS) physiology and diseases, and identify a potential therapeutic target.

Risk Factors of Suicidal Ideation in Iraqi Crystal Methamphetamine Users

Crystal methamphetamine, a potent psychostimulant, presents a complex clinical landscape. However, insights into the predisposing factors for suicidal tendencies among Iraqi users remain limited. Our study delves into these risks among 165 patients. Rigorous multivariable analysis was conducted, employing binary logistic regression, drawing from patients from Baghdad Medical City and Ibn-Rushd Teaching Hospital. Most participants were in their third decade (26.62 ± 0.53 years). Regarding suicidal ideation, our model demonstrated robust accuracy, supported by the Hosmer-Lemeshow goodness-of-fit test (NagelKerke's R2 = 0.49, accuracy = 79.4%, p = 0.885). Notably, chronic methamphetamine use exceeding a year (OR = 6.15, p = 0.001), absence of psychological trauma (OR = 4.58, p = 0.006), and incidence of visual hallucinations (OR = 4.52, p = 0.001) rendered users more susceptible to suicidal ideation. Furthermore, our investigation unveiled risk factors tied to psychotic features and withdrawal manifestations. The study underscores pivotal predictors of suicidal ideation, warranting interdisciplinary vigilance from psychiatrists, clinical psychologists, and social workers. By monitoring at-risk individuals, progression toward the intricate spectrum of suicide can be potentially averted. These findings illuminate the urgency of tailored interventions for crystal methamphetamine users, contributing to enhanced holistic care.

Modeling Parkinson's disease in LRRK2 rodents

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are associated with familial and sporadic forms of Parkinson's disease (PD). Sporadic PD and LRRK2 PD share main clinical and neuropathological features, namely hypokinesia, degeneration of nigro-striatal dopamine neurons and α-synuclein aggregates in the form of Lewy bodies. Animals harboring the most common LRRK2 mutations, i.e. p.G2019S and p.R1441C/G, have been generated to replicate the parkinsonian phenotype and investigate the underlying pathogenic mechanisms. Disappointingly, however, LRRK2 rodents did not consistently phenocopy hypokinesia and nigro-striatal degeneration, or showed Lewy body-like aggregates. Instead, LRRK2 rodents manifested non-motor signs and dysregulated transmission at dopaminergic and non-dopaminergic synapses that are reminiscent of behavioral and functional network changes observed in the prodromal phase of the disease. LRRK2 rodents also manifested greater susceptibility to different parkinsonian toxins or stressors when subjected to dual-hit or multiple-hit protocols, confirming LRRK2 mutations as genetic risk factors. In conclusion, LRRK2 rodents represent a unique tool to identify the molecular mechanisms through which LRRK2 modulates the course and clinical presentations of PD and to study the interplay between genetic, intrinsic and environmental protective/risk factors in PD pathogenesis.

Repeated Methamphetamine Administration Results in Axon Loss Prior to Somatic Loss of Substantia Nigra Pars Compacta and Locus Coeruleus Neurons in Male but Not Female Mice

Methamphetamine (meth) is a neurotoxic psychostimulant that increases monoamine oxidase (MAO)-dependent mitochondrial oxidant stress in axonal but not somatic compartments of substantia nigra pars compacta (SNc) and locus coeruleus (LC) neurons. Chronic meth administration results in the degeneration of SNc and LC neurons in male mice, and MAO inhibition is neuroprotective, suggesting that the deleterious effects of chronic meth begin in axons before advancing to the soma of SNc and LC neurons. To test this hypothesis, mice were administered meth (5 mg/kg) for 14, 21, or 28 days, and SNc and LC axonal lengths and numbers of neurons were quantified. In male mice, the SNc and LC axon lengths decreased with 14, 21, and 28 days of meth, whereas somatic loss was only observed after 28 days of meth; MAO inhibition (phenelzine; 20 mg/kg) prevented axonal and somatic loss of SNc and LC neurons. In contrast, chronic (28-day) meth had no effect on the axon length or numbers of SNc or LC neurons in female mice. The results demonstrate that repeated exposure to meth produces SNc and LC axonal deficits prior to somatic loss in male subjects, consistent with a dying-back pattern of degeneration, whereas female mice are resistant to chronic meth-induced degeneration.

Norepinephrine release in the cerebellum contributes to aversive learning

The modulation of dopamine release from midbrain projections to the striatum has long been demonstrated in reward-based learning, but the synaptic basis of aversive learning is far less characterized. The cerebellum receives axonal projections from the locus coeruleus, and norepinephrine release is implicated in states of arousal and stress, but whether aversive learning relies on plastic changes in norepinephrine release in the cerebellum is unknown. Here we report that in mice, norepinephrine is released in the cerebellum following an unpredicted noxious event (a foot-shock) and that this norepinephrine release is potentiated powerfully with fear acquisition as animals learn that a previously neutral stimulus (tone) predicts the aversive event. Importantly, both chemogenetic and optogenetic inhibition of the locus coeruleus-cerebellum pathway block fear memory without impairing motor function. Thus, norepinephrine release in the cerebellum is modulated by experience and underlies aversive learning.

Amphetamine-induced reverse transport of dopamine does not require cytosolic Ca2

Amphetamines (AMPHs) are substrates of the dopamine transporter (DAT) and reverse the direction of dopamine (DA) transport. This has been suggested to depend on activation of Ca2+-dependent pathways, but the mechanism underlying reverse transport via endogenously expressed DAT is still unclear. Here, to enable concurrent visualization by live imaging of extracellular DA dynamics and cytosolic Ca2+ levels, we employ the fluorescent Ca2+ sensor jRGECO1a expressed in cultured dopaminergic neurons together with the fluorescent DA sensor GRABDA1H expressed in cocultured "sniffer" cells. In the presence of the Na+-channel blocker tetrodotoxin to prevent exocytotic DA release, AMPH induced in the cultured neurons a profound dose-dependent efflux of DA that was blocked both by inhibition of DAT with cocaine and by inhibition of the vesicular monoamine transporter-2 with Ro-4-1284 or reserpine. However, the AMPH-induced DA efflux was not accompanied by an increase in cytosolic Ca2+ and was unaffected by blockade of voltage-gated calcium channels or chelation of cytosolic Ca2+. The independence of cytosolic Ca2+ was further supported by activation of N-methyl-D-aspartate-type ionotropic glutamate receptors leading to a marked increase in cytosolic Ca2+ without affecting AMPH-induced DA efflux. Curiously, AMPH elicited spontaneous Ca2+ spikes upon blockade of the D2 receptor, suggesting that AMPH can regulate intracellular Ca2+ in an autoreceptor-dependent manner regardless of the apparent independence of Ca2+ for AMPH-induced efflux. We conclude that AMPH-induced DA efflux in dopaminergic neurons does not require cytosolic Ca2+ but is strictly dependent on the concerted action of AMPH on both vesicular monoamine transporter-2 and DAT.

CDNF and MANF in the brain dopamine system and their potential as treatment for Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disease characterized by gradual loss of midbrain dopamine neurons, leading to impaired motor function. Preclinical studies have indicated cerebral dopamine neurotrophic factor (CDNF) and mesencephalic astrocyte-derived neurotrophic factor (MANF) to be potential therapeutic molecules for the treatment of PD. CDNF was proven to be safe and well tolerated when tested in Phase I-II clinical trials in PD patients. Neuroprotective and neurorestorative effects of CDNF and MANF were demonstrated in animal models of PD, where they promoted the survival of dopamine neurons and improved motor function. However, biological roles of endogenous CDNF and MANF proteins in the midbrain dopamine system have been less clear. In addition to extracellular trophic activities, CDNF/MANF proteins function intracellularly in the endoplasmic reticulum (ER), where they modulate protein homeostasis and protect cells against ER stress by regulating the unfolded protein response (UPR). Here, our aim is to give an overview of the biology of endogenous CDNF and MANF in the brain dopamine system. We will discuss recent studies on CDNF and MANF knockout animal models, and effects of CDNF and MANF in preclinical models of PD. To elucidate possible roles of CDNF and MANF in human biology, we will review CDNF and MANF tissue expression patterns and regulation of CDNF/MANF levels in human diseases. Finally, we will discuss novel findings related to the molecular mechanism of CDNF and MANF action in ER stress, UPR, and inflammation, all of which are mechanisms potentially involved in the pathophysiology of PD.

Neuroprotective activity of green synthesized silver nanoparticles against methamphetamine-induced cell death in human neuroblastoma SH-SY5Y cells

The present study aimed to investigate the neuroprotective activity of the black peel pomegranate extract, and silver nanoparticles (AgNPs) biosynthesized using the extract. We pretreated the human neuroblastoma SH-SY5 cells with the extract and AgNPs and evaluated the neuroprotective activity of these agents against methamphetamine (Meth) cytotoxicity. The NPs were spherical with 19 ± 8 nm size, - 28 mV surface charge, and 0.20 PDI. Meth killed the cells by increasing proapoptotic (Bax, PTEN, AKT, PI3K, NF-κB, P53, TNF-α, Cyt C, and Cas 3) and decreasing the antiapoptotic genes (Bcl-2) expression. Exposure to Meth caused DNA fragmentation and increased the intercellular ROS and malondialdehyde (MDA) levels while reducing the mitochondrial membrane potential (MMP). A 4-h pretreatment of the cells with the extract and AgNPs could retain the viability of the cells above 80% by increasing the Bcl-2 expression up to fourfold and inhibiting the cell death pathways. ROS, MDA, and MMP levels in the pretreated cells were close to the control group. The percentage of necrosis in cells pretreated with the extract and AgNPs declined to 32% and 8%, respectively. Our promising findings indicated that AgNPs could reduce Meth-induced oxidative stress and prevent necrotic and apoptotic cell death by regulating related genes' expression.

Synaptotagmin-1-dependent phasic axonal dopamine release is dispensable for basic motor behaviors in mice

In Parkinson's disease (PD), motor dysfunctions only become apparent after extensive loss of DA innervation. This resilience has been hypothesized to be due to the ability of many motor behaviors to be sustained through a diffuse basal tone of DA; but experimental evidence for this is limited. Here we show that conditional deletion of the calcium sensor synaptotagmin-1 (Syt1) in DA neurons (Syt1 cKODA mice) abrogates most activity-dependent axonal DA release in the striatum and mesencephalon, leaving somatodendritic (STD) DA release intact. Strikingly, Syt1 cKODA mice showed intact performance in multiple unconditioned DA-dependent motor tasks and even in a task evaluating conditioned motivation for food. Considering that basal extracellular DA levels in the striatum were unchanged, our findings suggest that activity-dependent DA release is dispensable for such tasks and that they can be sustained by a basal tone of extracellular DA. Taken together, our findings reveal the striking resilience of DA-dependent motor functions in the context of a near-abolition of phasic DA release, shedding new light on why extensive loss of DA innervation is required to reveal motor dysfunctions in PD.

Methamphetamine increases force of contraction in isolated human atrial preparations through the release of noradrenaline

We measured the cardiac contractile effects of the sympathomimetic amphetamine-like drug methamphetamine alone and in the presence of cocaine or propranolol in human atrial preparations. For a more comprehensive analysis, we also examined the effects of methamphetamine in preparations from the left and right atria of mice and, for comparison, analyzed the cardiac effects of amphetamine itself. In human atrial preparations, methamphetamine and amphetamine increased the contractile force, the relaxation rate, and the rate of tension development, and shortened the time to maximum tension and the time to relaxation. Likewise, in mice preparations, methamphetamine and amphetamine increased the contractile force in the left atrium and increased the beating rate in the right atrium. The effect in human atrial preparations started at 1µM, therefore methamphetamine was less effective and potent than isoproterenol in increasing contractile force. These positive inotropic effects of methamphetamine were greatly attenuated by 10µM cocaine and abolished by 10µM propranolol. The inotropic effects of methamphetamine in human atrial preparations were associated with, and are believed to be mediated at least in part by, an increase in the phosphorylation state of the inhibitory subunit of troponin. In conclusion, the sympathomimetic central stimulant drug methamphetamine (as well as amphetamine) increased contractile force and protein phosphorylation, presumably through a release of noradrenaline in isolated human atrial preparations. Thus, methamphetamine acts as an indirect sympathomimetic in the human atrium.

The Stage-Based Model of Addiction-Using Drosophila to Investigate Alcohol and Psychostimulant Responses

Addiction is a progressive and complex disease that encompasses a wide range of disorders and symptoms, including substance use disorder (SUD), for which there are few therapeutic treatments. SUD is the uncontrolled and chronic use of substances despite the negative consequences resulting from this use. The progressive nature of addiction is organized into a testable framework, the neurobiological stage-based model, that includes three behavioral stages: (1) binge/intoxication, (2) withdrawal/negative affect, and (3) preoccupation/anticipation. Human studies offer limited opportunities for mechanistic insights into these; therefore, model organisms, like Drosophila melanogaster, are necessary for understanding SUD. Drosophila is a powerful model organism that displays a variety of SUD-like behaviors consistent with human and mammalian substance use, making flies a great candidate to study mechanisms of behavior. Additionally, there are an abundance of genetic tools like the GAL4/UAS and CRISPR/Cas9 systems that can be used to gain insight into the molecular mechanisms underlying the endophenotypes of the three-stage model. This review uses the three-stage framework and discusses how easily testable endophenotypes have been examined with experiments using Drosophila, and it outlines their potential for investigating other endophenotypes.

Maternal use of methamphetamine alters cardiovascular function in the adult offspring

Methamphetamine is one of the most commonly used illicit drugs during pregnancy. Most studies investigating the impact of maternal use of methamphetamine on children have focused on neurological outcomes. In contrast, cardiovascular outcomes in these children have not been characterized. Recent studies in rodents provide evidence that prenatal exposure to methamphetamine induces changes in cardiac gene expression, changes in the heart's susceptibility to ischemic injury, and changes in vascular function that may increase the risk of developing cardiovascular disorders later in life. Importantly, these changes are sex-dependent. This review summarizes our current understanding of how methamphetamine use during pregnancy impacts the cardiovascular function of adult offspring and highlights gaps in our knowledge of the potential cardiovascular risks associated with prenatal exposure to methamphetamine.

Neuropathologic Features in Chronic Methamphetamine Use

ABSTRACT

Methamphetamine is a psychostimulant that exerts its euphoric and stimulant effects by increasing cytosolic monoamine concentration at the nerve terminal. In addition to its known systemic cardiovascular effects, there is compelling evidence to suggest a direct neurotoxic effect of methamphetamine; however, the existing body of literature includes very few human tissue studies. This exploratory analysis used postmortem human brain specimens to examine histologic and immunohistochemical features associated with chronic methamphetamine use. This retrospective cohort study included 60 decedents who were autopsied at the University of Iowa Hospitals and Clinics between the years 2015 and 2021. Logistic regression models demonstrated no definite pathologic changes in the hippocampi of individuals with a history of chronic methamphetamine use. Decedents with a history of methamphetamine use had a marginally increased odds of basal ganglia arteriosclerosis, which did not reach statistical significance (odds ratio, 3.33; 95% confidence interval, 0.6-19.2; P = 0.17), which may be independent of the systemic hypertensive effects of methamphetamine. Future studies that include targeted examination of brain regions of interest, such as the basal ganglia and specifically the striatum, may prove revealing.

Endocytic down-regulation of the striatal dopamine transporter by amphetamine in sensitized mice in sex-dependent manner

Dopamine transporter (DAT) controls dopamine signaling in the brain through the reuptake of synaptically released dopamine. DAT is a target of abused psychostimulants such as amphetamine (Amph). Acute Amph is proposed to cause transient DAT endocytosis which among other Amph effects on dopaminergic neurons elevates extracellular dopamine. However, the effects of repeated Amph abuse, leading to behavioral sensitization and drug addiction, on DAT traffic are unknown. Hence, we developed a 14-day Amph-sensitization protocol in knock-in mice expressing HA-epitope tagged DAT (HA-DAT) and investigated effects of Amph challenge on HA-DAT in sensitized animals. Amph challenge resulted in the highest locomotor activity on day 14 in both sexes, which was however sustained for 1 hour in male but not female mice. Strikingly, significant (by 30-60%) reduction in the amount of the HA-DAT protein in striatum was observed in response to Amph challenge of sensitized males but not females. Amph reduced Vmax of dopamine transport in striatal synaptosomes of males without changing Km values. Consistently, immunofluorescence microscopy revealed a significant increase of HA-DAT co-localization with the endosomal protein VPS35 only in males. Amph-induced HA-DAT down-regulation in the striatum of sensitized mice was blocked by chloroquine, vacuolin-1 (inhibitor of PIKfive kinase), and inhibitor of Rho-associated kinases (ROCK1/2), indicative of the involvement of endocytic trafficking in DAT down-regulation. Interestingly, HA-DAT protein down-regulation was observed in nucleus accumbens and not in dorsal striatum. We propose that Amph challenge in sensitized mice leads to ROCK-dependent endocytosis and post-endocytic traffic of DAT in a brain-region-specific and sex-dependent manner.

Movement disorders associated with substance use in adults living in precarious housing or homelessness

OBJECTIVE

Many individuals living in precarious housing or homelessness have multimorbid illnesses, including substance use, psychiatric, and neurological disorders. Movement disorders (MDs) associated substance use are amongst the poorly studied subtopics of drug-induced MDs. The aim of the present study was, therefore, to determine the proportion affected and severity of different signs of MDs, as well as their associations with substance use in a community-based sample of precariously housed and homeless individuals.

METHODS

Participants were recruited from an impoverished urban neighborhood and were assessed for substance dependence and self-reported substance use (alcohol, cannabis, cocaine, methamphetamine, nicotine, and opioids), as well as for the severity of signs of MDs (akathisia, dyskinesia, dystonia, and parkinsonism). Adjusted regression models were used to estimate the associations of the severity of signs with the frequency of substance use over the past 4 weeks and with the baseline diagnosis of substance dependence.

RESULTS

The proportion of the sample with clinically relevant signs of MDs in any of the four categories was 18.6% (n = 401), and these participants demonstrated lower levels of functioning than those without signs. Of the different types of substance use, only methamphetamine (its frequency of use and dependence) was significantly associated with greater severity of overall signs of MDs. Frequency of methamphetamine use significantly interacted with age and sex, whereby older female participants exhibited the greatest overall severity with increased methamphetamine use. Of the different signs of MDs, methamphetamine use frequency was positively associated with the severity of trunk/limb dyskinesia and hypokinetic parkinsonism. Relative to no use, concurrent use of antipsychotics demonstrated lower severity of trunk/limb dyskinesia and greater severity of hypokinetic parkinsonism with methamphetamine use, and greater severity of dystonia with cocaine use.

CONCLUSIONS

Our study found a high proportion of MDs in a relatively young sample, and their severity was consistently associated with methamphetamine use, moderated by participant demographics and antipsychotic use. These disabling sequelae represent an important and understudied neurological condition that may affect quality of life and will require further study.

Antibody-Conjugated Electrospun Nanofibers for Electrochemical Detection of Methamphetamine

Multifunctional electrospun nanofibers (ENs) with improved properties have increased attention nowadays. Their insoluble forms in water with decreased hydrophobicity are desired for the immobilization of biological molecules. Also, the addition of functional groups on the backbone provides the conjugation of biomolecules onto the surface of ENs via covalent bonds to increase their stability. Here, poly(vinylidene fluoride) (PVDF) was chosen to prepare a platform, which is insoluble in water, and polyethylenimine (PEI) was used to add amine groups on the surface of ENs to bind biological molecules via covalent conjugation. So, PVDF-PEI nanofibers were prepared on a glassy carbon electrode to immobilize an antimethamphetamine antibody (Anti-METH) as a model biomolecule. The obtained PVDF-PEI/Anti-METH was used for the bioelectrochemical detection of methamphetamine (METH), a common illicit drug. Bioelectrochemical detection of METH on PVDF-PEI/Anti-METH-coated electrodes was carried out by voltammetry in the range of 2.0-50 ng/mL METH. Moreover, the effect of dansyl chloride (DNC) derivatization of METH on the sensitivity of PVDF-PEI/Anti-METH was tested. Finally, METH analysis was carried out in synthetic body fluids. The obtained results showed that PVDF-PEI ENs can be adopted as an immobilization matrix for the biorecognition elements of biobased detection systems, and the derivative of METH (METH-DNC) increased the sensitivity of PVDF-PEI/Anti-METH.

Sexual satiety modifies methamphetamine-induced locomotor and rewarding effects and dopamine-related protein levels in the striatum of male rats

RATIONALE

Drug and natural rewarding stimuli activate the mesolimbic dopaminergic system. Both methamphetamine (Meth) and copulation to satiety importantly increase dopamine (DA) release in the nucleus accumbens (NAc), but with differences in magnitude. This paper analyzes the interaction between Meth administration and the intense sexual activity associated with sexual satiety.

OBJECTIVES

To evaluate possible changes in Meth-induced behavioral effects and striatal DA-related protein expression due to sexual satiety.

METHODS

Meth-induced locomotor activity and conditioned place preference (CPP) were tested in sexually experienced male rats that copulated to satiety (S-S) or ejaculated once (1E) the day before or displayed no sexual activity (control group; C). DA receptors and DA transporter expression were determined by western blot in the striatum of animals of all sexual conditions treated with specific Meth doses.

RESULTS

Meth's locomotor and rewarding effects were exacerbated in S-S animals, while in 1E rats, only locomotor effects were enhanced. Sexual activity, by itself, modified DA-related protein expression in the NAc core and in the caudate-putamen (CPu), while Meth treatment alone changed their expression only in the NAc shell. Meth-induced changes in the NAc shell turned in the opposite direction when animals had sexual activity, and additional changes appeared in the NAc core and CPu of S-S rats.

CONCLUSION

Sexual satiety sensitizes rats to Meth's behavioral effects and the Meth-induced striatal DA-related protein adaptations are modified by sexual activity, evidencing cross-sensitization between both stimuli.

Catecholaminergic axon innervation and morphology in flat-mounts of atria and ventricles of mice

Sympathetic efferent axons regulate cardiac functions. However, the topographical distribution and morphology of cardiac sympathetic efferent axons remain insufficiently characterized due to the technical challenges involved in immunohistochemical labeling of the thick walls of the whole heart. In this study, flat-mounts of the left and right atria and ventricles of FVB mice were immunolabeled for tyrosine hydroxylase (TH), a marker of sympathetic nerves. Atrial and ventricular flat-mounts were scanned using a confocal microscope to construct montages. We found (1) In the atria: A few large TH-immunoreactive (IR) axon bundles entered both atria, branched into small bundles and then single axons that eventually formed very dense terminal networks in the epicardium, myocardium and inlet regions of great vessels to the atria. Varicose TH-IR axons formed close contact with cardiomyocytes, vessels, and adipocytes. Multiple intrinsic cardiac ganglia (ICG) were identified in the epicardium of both atria, and a subpopulation of the neurons in the ICG were TH-IR. Most TH-IR axons in bundles traveled through ICG before forming dense varicose terminal networks in cardiomyocytes. We did not observe varicose TH-IR terminals encircling ICG neurons. (2) In the left and right ventricles and interventricular septum: TH-IR axons formed dense terminal networks in the epicardium, myocardium, and vasculature. Collectively, TH labeling is achievable in flat-mounts of thick cardiac walls, enabling detailed mapping of catecholaminergic axons and terminal structures in the whole heart at single-cell/axon/varicosity scale. This approach provides a foundation for future quantification of the topographical organization of the cardiac sympathetic innervation in different pathological conditions.