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Experimental Neurology Apr 2024The clinical manifestation of Parkinson's disease (PD) appears when neurodegeneration is already advanced, compromising the efficacy of disease-modifying treatment...
The clinical manifestation of Parkinson's disease (PD) appears when neurodegeneration is already advanced, compromising the efficacy of disease-modifying treatment approaches. Biomarkers to identify the early stages of PD are therefore of paramount importance for the advancement of the therapy of PD. In the present study, by using a mouse model of PD obtained by subchronic treatment with the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and the clearance inhibitor probenecid (MPTPp), we identified prodromal markers of PD by combining in vivo positron emission tomography (PET) imaging and ex vivo immunohistochemistry. Longitudinal PET imaging of the dopamine transporter (DAT) by [F]-N-(3-fluoropropyl)-2β-carboxymethoxy-3β-(4-iodophenyl) nortropane ([F]-FP-CIT), and brain glucose metabolism by 2-deoxy-2-[F]-fluoroglucose ([F]-FDG) were performed before MPTPp treatment and after 1, 3, and 10 MPTPp administrations, in order to assess relation between dopamine neuron integrity and brain connectivity. The results show that in vivo [F]-FP-CIT in the dorsal striatum was not modified after the first administration of MPTPp, tended to decrease after 3 administrations, and significantly decreased after 10 MPTPp administrations. Post-mortem immunohistochemical analyses of DAT and tyrosine hydroxylase (TH) in the striatum showed a positive correlation with [F]-FP-CIT, confirming the validity of repeated MPTPp-treated mice as a model that can reproduce the progressive pathological changes in the early phases of PD. Analysis of [F]-FDG uptake in several brain areas connected to the striatum showed that metabolic connectivity was progressively disrupted, starting from the first MPTPp administration, and that significant connections between cortical and subcortical regions were lost after 10 MPTPp administrations, suggesting an association between dopamine neuron degeneration and connectivity disruption in this PD model. The results of this study provide a relevant model, where new drugs that can alleviate neurodegeneration in PD could be evaluated preclinically.
Topics: Humans; Parkinson Disease; Dopamine; Probenecid; Dopaminergic Neurons; Fluorodeoxyglucose F18; Dopamine Plasma Membrane Transport Proteins; Corpus Striatum; Nerve Degeneration; Tropanes
PubMed: 38281587
DOI: 10.1016/j.expneurol.2024.114704 -
The Journal of Pharmacology and... Jan 20243,4-Methylenedioxymethamphetamine (MDMA) has shown efficacy as a medication adjunct for treating post-traumatic stress disorder (PTSD). However, MDMA is also used in...
3,4-Methylenedioxymethamphetamine (MDMA) has shown efficacy as a medication adjunct for treating post-traumatic stress disorder (PTSD). However, MDMA is also used in non-medical contexts that pose risk for cardiovascular and neurological complications. It is well established that MDMA exerts its effects by stimulating transporter-mediated release of the monoamines, 5‑hydroxytryptamine (5-HT), norepinephrine, and dopamine. Current research efforts are aimed at developing MDMA-like monoamine releasers with better efficacy and safety profiles. To this end, we investigated neurochemical and behavioral effects of novel analogs of the designer drug, 5-(2-methylaminopropyl)benzofuran (5-MAPB). We used transporter assays in rat brain synaptosomes to examine transmitter uptake inhibition and releasing properties for enantiomers of 5-(2-methylaminobutyl)benzofuran (5-MABB) and 6-(2-methylaminobutyl)benzofuran (6-MABB) as compared to MDMA. We then tested these same compounds in male Sprague-Dawley rats trained to discriminate MDMA (1.5 mg/kg) from saline. results revealed that isomers of 5- and 6-MABB are efficacious releasing agents at transporters for 5-HT (SERT), norepinephrine (NET), and dopamine (DAT). By contrast, isomers are efficacious releasers at SERT, partial releasers at NET, but lack releasing activity at DAT. results showed that all compounds produce dose-dependent increases in MDMA-lever responding and full substitution at the highest dose tested. The diminished NET and DAT releasing activities for isomers of 5- and 6-MABB are associated with reduced potency for inducing behavioral effects. Collectively, these findings indicate that the aminoalkyl benzofuran scaffold may be a viable template for developing compounds with MDMA-like properties. Despite the clinical utility of MDMA, the drug is associated with certain cardiovascular risks and metabolic side effects. Developing a therapeutic alternative with MDMA-like monoamine releasing activity is of interest. Our and findings indicate that the aminoalkyl benzofuran scaffold may be useful for developing compounds with MDMA-like properties.
PubMed: 38272669
DOI: 10.1124/jpet.123.001837 -
ELife Jan 2024The neurotransmitter:sodium symporters (NSSs) are secondary active transporters that couple the reuptake of substrate to the symport of one or two sodium ions. One bound...
The neurotransmitter:sodium symporters (NSSs) are secondary active transporters that couple the reuptake of substrate to the symport of one or two sodium ions. One bound Na (Na1) contributes to the substrate binding, while the other Na (Na2) is thought to be involved in the conformational transition of the NSS. Two NSS members, the serotonin transporter (SERT) and the dopamine transporter (dDAT), also couple substrate uptake to the antiport of K by a largely undefined mechanism. We have previously shown that the bacterial NSS homologue, LeuT, also binds K, and could therefore serve as a model protein for the exploration of K binding in NSS proteins. Here, we characterize the impact of K on substrate affinity and transport as well as on LeuT conformational equilibrium states. Both radioligand binding assays and transition metal ion FRET (tmFRET) yielded similar K affinities for LeuT. K binding was specific and saturable. LeuT reconstituted into proteoliposomes showed that intra-vesicular K dose-dependently increased the transport velocity of [H]alanine, whereas extra-vesicular K had no apparent effect. K binding induced a LeuT conformation distinct from the Na- and substrate-bound conformation. Conservative mutations of the Na1 site residues affected the binding of Na and K to different degrees. The Na1 site mutation N27Q caused a >10-fold decrease in K affinity but at the same time a ~3-fold increase in Na affinity. Together, the results suggest that K binding to LeuT modulates substrate transport and that the K affinity and selectivity for LeuT is sensitive to mutations in the Na1 site, pointing toward the Na1 site as a candidate site for facilitating the interaction with K in some NSSs.
Topics: Sodium; Plasma Membrane Neurotransmitter Transport Proteins; Symporters; Binding Sites; Neurotransmitter Agents
PubMed: 38271216
DOI: 10.7554/eLife.87985 -
Medicina (Kaunas, Lithuania) Jan 2024Neuropsychiatric symptoms (NPS), including depression, anxiety, apathy, visual hallucinations, and impulse control disorders, are very common during the course of... (Review)
Review
Neuropsychiatric symptoms (NPS), including depression, anxiety, apathy, visual hallucinations, and impulse control disorders, are very common during the course of Parkinson's disease (PD), occurring even at the prodromal and premotor stages. Mild behavioral impairment (MBI) represents a recently described neurobehavioral syndrome, characterized by the emergence of persistent and impactful NPS in later life, reflecting arisk of dementia. Accumulating evidence suggests that MBI is highly prevalent in non-demented patients with PD, also being associated with an advanced disease stage, more severe motor deficits, as well as global and multiple-domain cognitive impairment. Neuroimaging studies have revealed that MBI in patients with PD may be related todistinct patterns of brain atrophy, altered neuronal connectivity, and distribution of dopamine transporter (DAT) depletion, shedding more light on its pathophysiological background. Genetic studies in PD patients have also shown that specific single-nucleotide polymorphisms (SNPs) may be associated with MBI, paving the way for future research in this field. In this review, we summarize and critically discuss the emerging evidence on the frequency, associated clinical and genetic factors, as well as neuroanatomical and neurophysiological correlates of MBI in PD, aiming to elucidate the underlying pathophysiology and its potential role as an early "marker" of cognitive decline, particularly in this population. In addition, we aim to identify research gaps, and propose novel relative areas of interest that could aid in our better understanding of the relationship of this newly defined diagnostic entity with PD.
Topics: Humans; Parkinson Disease; Anxiety; Anxiety Disorders; Cognitive Dysfunction; Polymorphism, Single Nucleotide
PubMed: 38256375
DOI: 10.3390/medicina60010115 -
International Journal of Molecular... Jan 2024Astrocytes are crucial in the regulation of neurotransmitter homeostasis, and while their involvement in the dopamine (DA) tripartite synapse is acknowledged, it...
Astrocytes are crucial in the regulation of neurotransmitter homeostasis, and while their involvement in the dopamine (DA) tripartite synapse is acknowledged, it necessitates a more comprehensive investigation. In the present study, experiments were conducted on primary astrocyte cultures from the striatum and cortex of neonatal rats. The pharmacological intricacies of DA uptake, including dependence on time, temperature, and concentration, were investigated using radiolabelled [H]-DA. The mRNA expression of transporters DAT, NET, PMAT, and OCTs was evaluated by qPCR. Notably, astrocytes from both brain regions exhibited prominent mRNA expression of NET and PMAT, with comparatively lower expression of DAT and OCTs. The inhibition of DA uptake by the DAT inhibitor, GBR12909, and NET inhibitors, desipramine and nortriptyline, impeded DA uptake in striatal astrocytes more than in cortical astrocytes. The mRNA expression of NET and PMAT was significantly upregulated in cortical astrocytes in response to the DA receptor agonist apomorphine, while only the mRNA expression of NET exhibited changes in striatal astrocytes. Haloperidol, a DA receptor antagonist, and L-DOPA, a DA precursor, did not induce significant alterations in transporter mRNA expression. These findings underscore the intricate and region-specific mechanisms governing DA uptake in astrocytes, emphasizing the need for continued exploration to unravel the nuanced dynamics of astrocytic involvement in the DA tripartite synapse.
Topics: Animals; Rats; Dopamine; Animals, Newborn; Astrocytes; Corpus Striatum; Membrane Transport Proteins; RNA, Messenger
PubMed: 38255983
DOI: 10.3390/ijms25020911 -
Journal of Experimental Pharmacology 2024Viloxazine ER (viloxazine extended-release capsules; Qelbree), a nonstimulant attention-deficit/hyperactivity disorder (ADHD) treatment, has known activity as a...
Viloxazine Increases Extracellular Concentrations of Norepinephrine, Dopamine, and Serotonin in the Rat Prefrontal Cortex at Doses Relevant for the Treatment of Attention-Deficit/Hyperactivity Disorder.
BACKGROUND
Viloxazine ER (viloxazine extended-release capsules; Qelbree), a nonstimulant attention-deficit/hyperactivity disorder (ADHD) treatment, has known activity as a norepinephrine (NE) transporter (NET) inhibitor. In vitro studies have also shown direct pharmacological effects on specific serotonin (5-HT) receptors, but not on the serotonin transporter (SERT). An in vivo microdialysis study in rats showed viloxazine (50 mg/kg i.p.) increased extracellular 5-HT, NE, and dopamine (DA) in the prefrontal cortex (PFC), a key brain region in ADHD pathology. This study evaluated whether these effects occur at clinically relevant concentrations.
METHODS
Microdialysis experiments were conducted in freely-moving, Sprague-Dawley rats (males, 8 weeks). Viloxazine (1, 3, 10, 30 mg/kg) was administered intraperitoneally to establish the dose range in rats at which viloxazine plasma concentrations aligned with those of individuals with ADHD administered therapeutic doses of viloxazine ER. Concentrations of unbound viloxazine, NE, 5-HT, DA, and NE and 5-HT metabolites (3,5-dihydroxyphenylglycol [DHPG] and 5-hydroxyindoleacetic acid [5-HIAA]) were measured in PFC interstitial fluid. After identifying a therapeutically relevant dose (30 mg/kg), the experiment was repeated using 30 and 50 mg/kg viloxazine (as 50 mg/kg increased NE, 5-HT, and DA in prior studies).
RESULTS
Viloxazine unbound (free drug) plasma concentrations in rats at 30 mg/kg were comparable to free drug concentrations in individuals with ADHD taking clinically effective doses (based on validated population PK models). Viloxazine 30 mg/kg significantly increased extracellular NE, 5-HT, and DA PFC levels compared to vehicle. Concomitant decreases in DHPG, but not 5-HIAA, support the inhibitory effect of viloxazine on NET but not SERT.
CONCLUSION
At clinically relevant concentrations, viloxazine increases PFC NE, DA, and 5-HT. Prefrontal augmentation of 5-HT does not appear to result from 5-HT reuptake inhibition but may be related to activation of 5-HT neurons. The potential therapeutic role of serotonergic effects in ADHD treatment merits further exploration.
PubMed: 38249320
DOI: 10.2147/JEP.S433524 -
Journal of Pharmacological Sciences Feb 2024Attention-deficit/hyperactivity disorder (ADHD) is the most common childhood-onset psychiatric disorder. We investigated the effects of systemic administration of...
Attention-deficit/hyperactivity disorder (ADHD) is the most common childhood-onset psychiatric disorder. We investigated the effects of systemic administration of monoamine reuptake inhibitors on long-term potentiation (LTP) formation and monoamine release in the medial prefrontal cortex (mPFC) of the stroke-prone spontaneously hypertensive rat (SHRSP)/Ezo, an animal model of ADHD, and its genetic control, Wistar Kyoto (WKY)/Ezo, to elucidate the functional changes in the mPFC monoamine neural system. Methylphenidate (dopamine (DA) and noradrenaline (NA) reuptake inhibitor) and desipramine (NA reuptake inhibitor) improved LTP formation defects in the mPFC of SHRSP/Ezo, suggesting that NA or both DA and NA are required for improvement of impaired LTP. Methylphenidate increased mPFC DA in both WKY/Ezo and SHRSP/Ezo, but the increase was greater in the former. GBR-12909 (DA reuptake inhibitor) increased mPFC DA in WKY/Ezo but had no effect in SHRSP/Ezo. This may be because DA transporter in SHRSP/Ezo is functionally impaired and contributes less to DA reuptake, so its inhibition did not increase DA level. Meanwhile, basal DA levels in the mPFC of SHRSP/Ezo were paradoxically decreased. These results suggest that functional changes in the DA and NA neural system in the frontal lobe are involved in the pathology of ADHD.
Topics: Humans; Rats; Animals; Child; Rats, Inbred WKY; Attention Deficit Disorder with Hyperactivity; Rats, Inbred SHR; Amines; Methylphenidate; Models, Animal; Dopamine
PubMed: 38246729
DOI: 10.1016/j.jphs.2023.12.002 -
Environmental Research Apr 2024The monoaminergic systems dopamine (DA) and serotonin (5-HT) play important roles in neuromodulation, such as motor control, cognitive, affective, and neuroendocrine...
The monoaminergic systems dopamine (DA) and serotonin (5-HT) play important roles in neuromodulation, such as motor control, cognitive, affective, and neuroendocrine functions. In the present research study, we addressed the hypothesis that exposure to Type I pyrethroid tefluthrin may specifically target the dopaminergic and serotoninergic systems. Tefluthrin could modify brain monoamine neurotransmitters, DA and 5-HT levels as well as dopaminergic and serotoninergic signaling pathways. Adult male Wistar rats were treated with tefluthrin [2.2, 4.4 and 5.5 mg/kg bw, equivalent to 1/10, 1/5 and 1/4 of the acute oral rat lethal dose 50 (LD) value] by oral gavage, six days. After last dose of tefluthrin, DA and 5-HT and metabolites levels were determined in brain regions (striatum, hippocampus, prefrontal cortex and hypothalamus). Tefluthrin induced a decrease of DA, 5-HT and metabolites contents, in a brain regional- and dose-related manner. The major decreases in DA and 5-HT contents were observed in prefrontal cortex tissue. Here, we studied that in vivo exposure to tefluthrin may alter DA and 5-HT neurotransmission in prefrontal cortex. Transcripts related to (i) dopaminergic [dopamine transporter 1 (Dat1), tyrosine hydroxylase (TH), dopamine receptors (Drd1, Drd2)], (ii) serotoninergic [serotonin transporter (SERT), tryptophan hydroxylase 2 (TPH2), serotonin receptors (5-HT1A, 5-HT2A)] and (iii) DA and 5-HT degradation [monoamine oxidases (MAOA, MAOB)] signaling pathways were investigated. Results showed that tefluthrin induced down-regulation of transcripts responsible for the synthesis and action of DA (TH, Drd1, Drd2) and 5-HT (SERT, TPH2). In contrast, tefluthrin treatment induced up-regulation of genes involved in DA transporter (Dat1), 5-HT receptors (5-HT1A, 5-HT2A) and monoamine oxidases (MAOA, MAOB). Given the integral roles of mitochondrial dysfunction and dopaminergic and serotoninergic alterations as hallmarks of neurodegenerative diseases, our data suggest that tefluthrin may be a candidate for pesticides contributing to neurodegenerative disorders pathogenesis by causing damage to the DA and 5-HT systems.
Topics: Rats; Male; Animals; Dopamine; Pyrethrins; Serotonin; Rats, Wistar; Brain; Oxidoreductases; Cyclopropanes; Hydrocarbons, Fluorinated
PubMed: 38244974
DOI: 10.1016/j.envres.2024.118239 -
Psychopharmacology Feb 2024Dopamine antagonists induce dopamine receptor supersensitivity. This may manifest in late-appearing movement disorders (tardive dyskinesia (TD). VMAT-2 inhibitors reduce... (Meta-Analysis)
Meta-Analysis Review
RATIONALE
Dopamine antagonists induce dopamine receptor supersensitivity. This may manifest in late-appearing movement disorders (tardive dyskinesia (TD). VMAT-2 inhibitors reduce dopaminergic transmission but have limited activity at postsynaptic receptors and so may have antipsychotic activity with lower risk of tardive dyskinesia.
METHODS
We conducted a systematic database search from inception to September 2022 for articles describing the use of VMAT-2 inhibitors in psychosis. Inclusion criteria were as follows: Population: adults diagnosed with psychosis or schizophrenia; Intervention: treatment with tetrabenazine, deutetrabenazine or valbenazine; Comparison: comparison with placebo or/and antipsychotic drug; Outcomes: with efficacy outcomes (e.g. Brief Psychiatric Rating Scale (BPRS) change or clinician assessment) and adverse effects ratings (e.g. rating scale or clinician assessment or dropouts); and Studies: in randomised controlled trials and non-randomised studies.
RESULTS
We identified 4892 records relating to VMAT-2 inhibitor use of which 5 (173 participants) met our a priori meta-analysis inclusion criteria. VMAT-2 inhibitors were more effective than placebo for the outcome 'slight improvement' (risk ratio (RR) = 1.77 (95% CI 1.03, 3.04)) but not for 'moderate improvement' (RR 2.81 (95% CI 0.27, 29.17). VMAT-2 inhibitors were as effective as active comparators on both measures for-'slight improvement' (RR 1.05 (95% CI 0.6, 1.81)) and 'moderate improvement' (RR 1.11 (95% CI 0.51, 2.42). Antipsychotic efficacy was also suggested by a narrative review of 37 studies excluded from the meta-analysis.
CONCLUSIONS
VMAT-2 inhibitors may have antipsychotic activity and may offer promise for treatment of psychosis with the potential for a reduced risk of TD.
Topics: Adult; Humans; Antipsychotic Agents; Psychotic Disorders; Schizophrenia; Tardive Dyskinesia; Tetrabenazine; Vesicular Monoamine Transport Proteins
PubMed: 38238580
DOI: 10.1007/s00213-023-06488-3 -
International Journal of Molecular... Dec 2023Drug addiction is a chronic biochemical drug use disorder that affects the human brain and behavior and leads to the uncontrolled use of legal or illicit drugs. It has...
Drug addiction is a chronic biochemical drug use disorder that affects the human brain and behavior and leads to the uncontrolled use of legal or illicit drugs. It has been shown that three factors are involved in the development of addiction: genetic factors, a diverse environment, and the effect of medication on gene expression. The comprehensive approach and holistic analysis of the problem are due to the multigenic and multifactorial nature of addiction. Dopamine, one of the major neurotransmitters in the brain, is believed to be the "culprit" that leads to a drug abuse-induced "high". That is why, in our research, we focused mainly on the genes related to dopaminergic reuptake. In the present study, we chose methylation of the dopamine transporter gene based on molecular reasons related to the dopaminergic theory of addiction. This study included two groups: 226 stimulant-dependent and 290 non-stimulant-dependent subjects. The analysis consisted of a case-control comparison of people addicted to psychostimulants compared to a control group of healthy and non-addicted people. There were differences in the levels of statistical significance between the groups. Our research shows lower methylation of islands 1, 9, and 14 in addicted people and greater methylation of islands 32 and 33. The difference in individual CpG methylation islands of the gene under study provides valuable information about the DNA methylation process in patients addicted to psychostimulants. Pearson's linear correlation analysis in stimulant dependence showed a negative correlation between total methylation island levels and the NEO-FFI Neuroticism scale. In subjects with neuroticism, the methylation level was statistically significantly lower. Pearson's linear correlation analysis of stimulant-dependent subjects showed a positive correlation between total methylation island levels and the NEO-FFI Openness scale and the NEO-FFI Conscientiousness scale.
Topics: Humans; Dopamine Plasma Membrane Transport Proteins; Central Nervous System Stimulants; DNA Methylation; Illicit Drugs; Dopamine; Personality
PubMed: 38203701
DOI: 10.3390/ijms25010532