The microRNA-485-3p concentration in salivary exosome-enriched extracellular vesicles is related to amyloid ß deposition in the brain of patients with Alzheimer's disease.

OBJECTIVES: Alzheimer's disease (AD) is an irreversible neurodegenerative disease characterized by progressive long-term memory loss and cognitive dysfunction. Neuroimaging tests for abnormal amyloid-ß (Aß) deposition are considered the most reliable methods for the diagnosis of AD; however, the cost for such testing is very high and generally not covered by national insurance systems. Accordingly, it is only recommended for individuals exhibiting clinical symptoms of AD supported by clinical cognitive assessments. Recently, it was suggested that dysregulated microRNA-485-3p (miRNA-485-3p) in the brain and cerebrospinal fluid is closely related to pathogenesis of AD. However, a relationship between circulating miRNA-485-3p in salivary exosome-enriched extracellular vesicles (EE-EV) and Aß deposition in the brain has not been observed. DESIGN & METHODS: Using quantitative real-time polymerase chain reaction, we analyzed miRNA-485-3p concentration in salivary EE-EV. We used receiver operating characteristic (ROC) curve analysis to evaluate its predictive value for Aß positron emission tomography (Aß-PET) positivity in patients with AD. RESULTS: Our results showed that the miRNA-485-3p concentration in salivary EE-EV isolated from patients with AD was significantly increased compared with that in the healthy controls (p < 0.0001). In the analysis of all participants, the miRNA-485-3p concentration was significantly increased in Aß-PET-positive participants compared to Aß-PET-negative participants (p < 0.0001). Further analysis using only AD patients also showed that the miRNA-485-3p concentration was significantly increased in Aß-PET-positive AD patients vs. Aß-PET-negative AD patients (p = 0.0063). The ROC curve analysis for differentiating Aß-PET-positive and negative participants showed that the area under the curve for miRNA-485-3p was 0.9217. CONCLUSION: These findings suggested that the miRNA-485-3p concentration in salivary EE-EV was closely related to Aß deposition in the brain and had high diagnostic accuracy for predicting Aß-PET positivity.

The role of microRNA-485 in neurodegenerative diseases.

Neurodegenerative diseases (NDDs) are age-related disorders characterized by progressive neurodegeneration and neuronal cell loss in the central nervous system. Neuropathological conditions such as the accumulation of misfolded proteins can cause neuroinflammation, apoptosis, and synaptic dysfunction in the brain, leading to the development of NDDs including Alzheimer's disease (AD) and Parkinson's disease (PD). MicroRNAs (miRNAs) are small noncoding RNA molecules that regulate gene expression post-transcriptionally via RNA interference. Recently, some studies have reported that some miRNAs play an important role in the development of NDDs by regulating target gene expression. MiRNA-485 (miR-485) is a highly conserved brain-enriched miRNA. Accumulating clinical reports suggest that dysregulated miR-485 may be involved in the pathogenesis of AD and PD. Emerging studies have also shown that miR-485 plays a novel role in the regulation of neuroinflammation, apoptosis, and synaptic function in the pathogenesis of NDDs. In this review, we introduce the biological characteristics of miR-485, provide clinical evidence of the dysregulated miR-485 in NDDs, novel roles of miR-485 in neuropathological events, and discuss the potential of targeting miR-485 as a diagnostic and therapeutic marker for NDDs.

Challenge exposure to whole cigarette smoke condensate upregulates locomotor sensitization by stimulating α4ß2 nicotinic acetylcholine receptors in the nucleus accumbens of rats.

Nicotine, the primary addictive substance in tobacco, produces the psychomotor, rewarding, and reinforcing effects of tobacco dependence by stimulating nicotinic acetylcholine receptors (nAChRs) in the brain. The present study determined that α4ß2 nAChRs regulate locomotor sensitization by altering dopamine concentration in the nucleus accumbens (NAc) after systemic challenge exposure to whole cigarette smoke condensate (WCSC). Rats were administered subcutaneous injection of WCSC (0.2 mg/kg nicotine/day) for 7 consecutive days and then re-exposed to WCSC after 3 days of withdrawal. Challenge exposure to WCSC significantly increased locomotor activity. This increase was decreased by the subcutaneous injection of the α4ß2 nAChR antagonist, DHßE (3 mg/kg), but not by the intraperitoneal injection of the α7 nAChR antagonist, MLA (5 mg/kg). In parallel with a decrease in locomotor activity, blockade of α4ß2 nAChRs with DHßE decreased dopamine concentration in the NAc which was elevated by challenge exposure to WCSC. These findings suggest that challenge WCSC leads to the expression of locomotor sensitization by elevating dopamine concentration via stimulation of α4ß2 nAChRs expressed in neurons of the NAc in rats.

Nicotine Rather Than Non-Nicotine Substances in 3R4F WCSC Increases Behavioral Sensitization and Drug-Taking Behavior in Rats.

INTRODUCTION: Nicotine increases reinforcing effects of cigarette smoking by upregulating glutamate and dopamine releases via stimulation of nicotinic acetylcholine receptors (nAChRs) in the dorsal striatum (CPu). The present study was conducted to evaluate whether non-nicotine substances in cigarette smoke potentiate nicotine-induced behaviors by increasing glutamate and dopamine concentrations in the CPu. AIMS AND METHODS: Changes in the levels of glutamate and dopamine in the CPu were analyzed using a glutamate colorimetric assay and dopamine enzyme-linked immunosorbent assay, respectively, after repeated administration of nicotine or whole cigarette smoke condensate (WCSC) in male Sprague-Dawley rats. Changes in locomotion and drug-taking behavior were analyzed using the measurements of locomotor activity and self-administration under a fixed ratio 1 schedule in response to repeated administration of nicotine or WCSC. RESULTS: Repeated subcutaneous (s.c.) injections of nicotine (0.25 mg/kg/day) for 7 consecutive days significantly increased the levels of glutamate and dopamine in the CPu. Similar results were obtained from repeated injections of WCSC (0.25 mg/kg nicotine/day, s.c.) extracted from 3R4F Kentucky reference cigarettes. Parallel with the increases in the neurotransmitter levels in the CPu, both nicotine and WCSC increased locomotor activity and self-administration (0.03 mg/kg nicotine/infusion). However, repeated injections of WCSC did not change the nicotine-induced increases in neurotransmitter levels, locomotor activity, and self-administration. CONCLUSIONS: Nicotine rather than non-nicotine substances in WCSC play a major role in potentiating behavioral sensitization and drug-taking behavior via elevation of glutamate and dopamine concentrations in the CPu of rats. IMPLICATIONS: WCSC does not augment the nicotine-induced increases in behavioral sensitization, drug-taking behavior, and glutamate and dopamine concentrations, suggesting that non-nicotine substances do not potentiate the nicotine-induced behaviors by increasing the concentrations of the neurotransmitters in the CPu. These findings imply that nicotine, but not non-nicotine substances in WCSC, may be a major contributor that induces tobacco dependence in rats.

miRNAs as Therapeutic Tools in Alzheimer's Disease.

Alzheimer's disease (AD), an age-dependent, progressive neurodegenerative disorder, is the most common type of dementia, accounting for 50-70% of all dementia cases. Due to the increasing incidence and corresponding socioeconomic burden of dementia, it has rapidly emerged as a challenge to public health worldwide. The characteristics of AD include the development of extracellular amyloid-beta plaques and intracellular neurofibrillary tangles, vascular changes, neuronal inflammation, and progressive brain atrophy. However, the complexity of the biology of AD has hindered progress in elucidating the underlying pathophysiological mechanisms of AD, and the development of effective treatments. MicroRNAs (miRNAs, which are endogenous, noncoding RNAs of approximately 22 nucleotides that function as posttranscriptional regulators of various genes) are attracting attention as powerful tools for studying the mechanisms of diseases, as they are involved in several biological processes and diseases, including AD. AD is a multifactorial disease, and several reports have suggested that miRNAs play an important role in the pathological processes of AD. In this review, the basic biology of miRNAs is described, and the function and physiology of miRNAs in the pathological processes of AD are highlighted. In addition, the limitations of current pharmaceutical therapies for the treatment of AD and the development of miRNA-based next-generation therapies are discussed.

Effects of ß-Phenylethylamine on Psychomotor, Rewarding, and Reinforcing Behaviors and Affective State: The Role of Dopamine D1 Receptors.

Beta-phenylethylamine (ß-PEA) is a well-known and widespread endogenous neuroactive trace amine found throughout the central nervous system in humans. In this study, we demonstrated the effects of ß-PEA on psychomotor, rewarding, and reinforcing behaviors and affective state using the open-field test, conditioned place preference (CPP), self-administration, and ultrasonic vocalizations (USVs) paradigms. We also investigated the role of the dopamine (DA) D1 receptor in the behavioral effects of ß-PEA in rodents. Using enzyme-linked immunosorbent assay (ELISA) and Western immunoblotting, we also determined the DA concentration and the DA-related protein levels in the dorsal striatum of mice administered with acute ß-PEA. The results showed that acute ß-PEA increased stereotypic behaviors such as circling and head-twitching responses in mice. In the CPP experiment, ß-PEA increased place preference in mice. In the self-administration test, ß-PEA significantly enhanced self-administration during a 2 h session under fixed ratio (FR) schedules (FR1 and FR3) and produced a higher breakpoint during a 6 h session under progressive ratio schedules of reinforcement in rats. In addition, acute ß-PEA increased 50-kHz USV calls in rats. Furthermore, acute ß-PEA administration increased DA concentration and p-DAT and TH expression in the dorsal striatum of mice. Finally, pretreatment with SCH23390, a DA D1 receptor antagonist, attenuated ß-PEA-induced circling behavior and ß-PEA-taking behavior in rodents. Taken together, these findings suggest that ß-PEA has rewarding and reinforcing effects and psychoactive properties, which induce psychomotor behaviors and a positive affective state by activating the DA D1 receptor in the dorsal striatum.

Brain Microdialysis Coupled to LC-MS/MS Revealed That CVT-10216, a Selective Inhibitor of Aldehyde Dehydrogenase 2, Alters the Neurochemical and Behavioral Effects of Methamphetamine.

Methamphetamine (MA), a potent central nervous system stimulant, mainly affects the brain dopaminergic and serotoninergic systems. Monoamine oxidase, catechol-O-methyltransferase, and aldehyde dehydrogenase 2 (ALDH2) are important enzymes in the metabolism of dopamine (DA) and serotonin (5-HT); however, the role of ALDH2 in MA addiction remains unclear. This study focused on the real-time changes in DA, 5-HT, and their metabolites, including 3,4-dihydroxyphenylacetic aldehyde and salsolinol, which are metabolites directly related to ALDH2, to examine the effects of the inhibition of ALDH2 on hyperlocomotion induced by MA. Locomotor activity was evaluated in rats after administration of MA and/or CVT-10216 (a selective ALDH2 inhibitor). Moreover, the simultaneous quantification of DA, 5-HT, and their metabolites in brain microdialysates of the rats was performed using a derivatization-assisted LC-MS/MS method after full validation. The validation results proved the method to be selective, sensitive, accurate, and precise, with acceptable linearity within calibration ranges. Intraperitoneal (i.p.) administration of 10 or 20 mg/kg of CVT-10216 significantly decreased MA-induced hyperlocomotion (1 mg/kg, i.p.). The analytical results of rat brain microdialysates demonstrated that the administration of CVT-10216 significantly downregulated DA levels, which were increased upon exposure to MA. Moreover, the increase in 3-methoxytyramine levels following coadministration of CVT-10216 and MA could play a potential role in antagonizing the hyperlocomotion induced by MA. All of these findings suggest that the inhibition of ALDH2 protects against MA-induced hyperlocomotion and has therapeutic potential in MA addiction.

Repeated nicotine exposure increases the intracellular interaction between ERK-mGluR5 in the nucleus accumbens more in adult than adolescent rats.

Intracellular interactions between protein kinases and metabotropic receptors in the striatum regulate behavioral changes in response to drug exposure. We investigated the difference in the degree of interaction between extracellular signal-regulated kinase (ERK) and metabotropic glutamate receptor subtype 5 (mGluR5) in the nucleus accumbens (NAc) after repeated exposure to nicotine in adult and adolescent rats. The results showed that repeated exposure to nicotine (0.5 mg/kg/day, s.c.) for seven consecutive days increased ERK phosphorylation more in adults than in adolescents. Furthermore, membrane expression of mGluR5 in gamma-aminobutyric acid (GABA) medium spiny neurons was higher in adults than adolescents as a result of repeated exposure to nicotine. Blockade of mGluR5 with MPEP (0.5 nmol/side) decreased the repeated nicotine-induced increase in ERK phosphorylation. Either blockade of mGluR5 or inhibition of ERK with SL327 (150 nmol/side) decreased the repeated nicotine-induced increase in the level of inositol-1,4,5-triphosphate (IP3 ), a key transducer associated with mGluR5-coupled signaling cascades. Similarly, interference of binding between activated ERK and mGluR5 by the blocking peptide, Tat-mGluR5-i (2 nmol/side), decreased the repeated nicotine-induced increases in IP3 and locomotor activity in adults. These findings suggest that the intracellular interaction between ERK and mGluR5 in the NAc is stronger in adult than in adolescent rats, which enhances the understanding of age-associated behavioral changes that occur after repeated exposure to nicotine.

Exposure to Commercial Cigarette Smoke Produces Psychomotor Sensitization Via Hyperstimulation of Glutamate Response in the Dorsal Striatum.

Cigarette smoke is a highly complex mixture of nicotine and non-nicotine constituents. Exposure to cigarette smoke enhances tobacco dependence by potentiating glutamatergic neurotransmission via stimulation of nicotinic acetylcholine receptors (nAChRs). We investigated the effects of nicotine and non-nicotine alkaloids in the cigarette smoke condensates extracted from two commercial cigarette brands in South Korea (KCSC A and KCSC B) on psychomotor behaviors and glutamate levels in the dorsal striatum. Repeated and challenge administration of KCSCs (nicotine content: 0.4 mg/kg, subcutaneous) increased psychomotor behaviors (ambulatory, rearing, and rotational activities) and time spent in psychoactive behavioral states compared to exposure to nicotine (0.4 mg/kg) alone. The increase in psychomotor behaviors lasted longer when exposed to repeated and challenge administration of KCSCs compared to nicotine alone. In parallel with sustained increase in psychomotor behaviors, repeated administration of KCSCs also caused long-lasting glutamate release in the dorsal striatum compared to nicotine alone. KCSC-induced changes in psychomotor behaviors and glutamate levels in the dorsal striatum were found to be strongly correlated. These findings suggest that non-nicotine alkaloids in commercial cigarette smoke synergistically act with nicotine on nAChRs, thereby upregulating glutamatergic response in the dorsal striatum, which contributes to the hypersensitization of psychomotor behaviors.

Transcriptional Profiling of Whisker Follicles and of the Striatum in Methamphetamine Self-Administered Rats.

Methamphetamine (MA) use disorder is a chronic neuropsychiatric disease characterized by recurrent binge episodes, intervals of abstinence, and relapses to MA use. Therefore, identification of the key genes and pathways involved is important for improving the diagnosis and treatment of this disorder. In this study, high-throughput RNA sequencing was performed to find the key genes and examine the comparability of gene expression between whisker follicles and the striatum of rats following MA self-administration. A total of 253 and 87 differentially expressed genes (DEGs) were identified in whisker follicles and the striatum, respectively. Multivariate and network analyses were performed on these DEGs to find hub genes and key pathways within the constructed network. A total of 129 and 49 genes were finally selected from the DEG sets of whisker follicles and of the striatum. Statistically significant DEGs were found to belong to the classes of genes involved in nicotine addiction, cocaine addiction, and amphetamine addiction in the striatum as well as in Parkinson's, Huntington's, and Alzheimer's diseases in whisker follicles. Of note, several genes and pathways including retrograde endocannabinoid signaling and the synaptic vesicle cycle pathway were common between the two tissues. Therefore, this study provides the first data on gene expression levels in whisker follicles and in the striatum in relation to MA reward and thereby may accelerate the research on the whisker follicle as an alternative source of biomarkers for the diagnosis of MA use disorder.

Mitigating Effects of Liriope platyphylla on Nicotine-Induced Behavioral Sensitization and Quality Control of Compounds.

In this study we investigated the mitigating effects of Liriope platyphylla Wang et Tang extract on behavioral sensitization and the quantification of its major compounds. The extract of L. platyphylla reduces the expression of tyrosine hydroxylase (TH) protein, which is increased by nicotine, back to normal levels, and increases the expression of dopamine transporter (DAT) protein, which is reduced by nicotine, back to normal levels in PC12 cells. In this study, rats received nicotine (0.4 mg/kg, subcutaneously) only for seven days and then received extract of L. platyphylla (200 or 400 mg/kg, oral) 1 h prior to nicotine administration for an additional seven days. The extract of L. platyphylla reduced locomotor activity compared to the nicotine control group in rats. The extract of L. platyphylla significantly attenuated the repeated nicotine-induced DAT protein expression in the nucleus accumbens (NAc), but there was no effect on increased TH protein expression in the dorsal striatum. These findings suggest that L. platyphylla extract has a mitigating effect on nicotine-induced behavioral sensitization by modulating DAT protein expression in the NAc. For quality control of L. plathyphylla, spicatoside A and D, which are saponin compounds, were quantified in the L. platyphylla extract. The amounts of spicatoside A and D in L. platyphylla extract obtained from ultra-high-performance liquid chromatography with tandem mass spectrometry were 0.148 and 0.272 mg/g, respectively. The identification of these compounds in L. platyphylla, which can be used for quality control, provides important information for the development of drugs to treat nicotine dependence.

The Abuse Potential of Novel Synthetic Phencyclidine Derivative 1-(1-(4-Fluorophenyl)Cyclohexyl)Piperidine (4'-F-PCP) in Rodents.

The dissociative anesthetic phencyclidine (PCP) and PCP derivatives, including 4'-F-PCP, are illegally sold and abused worldwide for recreational and non-medical uses. The psychopharmacological properties and abuse potential of 4'-F-PCP have not been fully characterized. In this study, we evaluated the psychomotor, rewarding, and reinforcing properties of 4'-F-PCP using the open-field test, conditioned place preference (CPP), and self-administration paradigms in rodents. Using Western immunoblotting, we also investigated the expression of dopamine (DA)-related proteins and DA-receptor-mediated downstream signaling cascades in the nucleus accumbens (NAc) of 4'-F-PCP-self-administering rats. Intraperitoneal administration of 10 mg/kg 4'-F-PCP significantly increased locomotor and rearing activities and increased CPP in mice. Intravenous administration of 1.0 mg/kg/infusion of 4'-F-PCP significantly enhanced self-administration during a 2 h session under fixed ratio schedules, showed a higher breakpoint during a 6 h session under progressive ratio schedules of reinforcement, and significantly altered the expression of DA transporter and DA D1 receptor in the NAc of rats self-administering 1.0 mg/kg 4'-F-PCP. Additionally, the expression of phosphorylated (p) ERK, pCREB, c-Fos, and FosB/ΔFosB in the NAc was significantly enhanced by 1.0 mg/kg 4'-F-PCP self-administration. Taken together, these findings suggest that 4'-F-PCP has a high potential for abuse, given its robust psychomotor, rewarding, and reinforcing properties via activation of DAergic neurotransmission and the downstream signaling pathways in the NAc.

Four Novel Synthetic Tryptamine Analogs Induce Head-Twitch Responses and Increase 5-HTR2a in the Prefrontal Cortex in Mice.

Tryptamines are monoamine alkaloids with hallucinogenic properties and are widely abused worldwide. To hasten the regulations of novel substances and predict their abuse potential, we designed and synthesized four novel synthetic tryptamine analogs: Pyrrolidino tryptamine hydrochloride (PYT HCl), Piperidino tryptamine hydrochloride (PIT HCl), N,N-dibutyl tryptamine hydrochloride (DBT HCl), and 2-Methyl tryptamine hydrochloride (2-MT HCl). Then, we evaluated their rewarding and reinforcing effects using the conditioned place preference (CPP) and self-administration (SA) paradigms. We conducted an open field test (OFT) to determine the effects of the novel compounds on locomotor activity. A head-twitch response (HTR) was also performed to characterize their hallucinogenic properties. Lastly, we examined the effects of the compounds on 5-HTR1a and 5-HTR2a in the prefrontal cortex using a quantitative real-time polymerase chain reaction (qRT-PCR) assay. None of the compounds induced CPP in mice or initiated SA in rats. PYT HCl and PIT HCl reduced the locomotor activity and elevated the 5-HTR1a mRNA levels in mice. Acute and repeated treatment with the novel tryptamines elicited HTR in mice. Furthermore, a drug challenge involving a 7-day abstinence from drug use produced higher HTR than acute and repeated treatments. Both the acute treatment and drug challenge increased the 5-HTR2a mRNA levels. Ketanserin blocked the induced HTR. Taken together, the findings suggest that PYT HCl, PIT HCl, DBT HCl, and 2-MT HCl produce hallucinogenic effects via 5-HTR2a stimulation, but may have low abuse potential.

4-MeO-PCP and 3-MeO-PCMo, new dissociative drugs, produce rewarding and reinforcing effects through activation of mesolimbic dopamine pathway and alteration of accumbal CREB, deltaFosB, and BDNF levels.

RATIONALE: A high number of synthetic dissociative drugs continue to be available through online stores, leading to their misuse. Recent inclusions in this category are 4-MeO-PCP and 3-MeO-PCMo, analogs of phencyclidine. Although the dissociative effects of these drugs and their recreational use have been reported, no studies have investigated their abuse potential. OBJECTIVES: To examine their rewarding and reinforcing effects and explore the mechanistic correlations. METHODS: We used conditioned place preference (CPP), self-administration, and locomotor sensitization tests to assess the rewarding and reinforcing effects of the drugs. We explored their mechanism of action by pretreating dopamine receptor (DR) D1 antagonist SCH23390 and DRD2 antagonist haloperidol during CPP test and investigated the effects of 4-MeO-PCP and 3-MeO-PCMo on dopamine-related proteins in the ventral tegmental area and nucleus accumbens. We also measured the levels of dopamine, phosphorylated cyclic-AMP response element-binding (p-CREB) protein, deltaFosB, and brain-derived neurotrophic factor (BDNF) in the nucleus accumbens. Additionally, we examined the effects of both drugs on brain wave activity using electroencephalography. RESULTS: While both 4-MeO-PCP and 3-MeO-PCMo induced CPP and self-administration, only 4-MeO-PCP elicited locomotor sensitization. SCH23390 and haloperidol inhibited the acquisition of drug CPP. 4-MeO-PCP and 3-MeO-PCMo altered the levels of tyrosine hydroxylase, DRD1, DRD2, and dopamine, as well as that of p-CREB, deltaFosB, and BDNF. All drugs increased the delta and gamma wave activity, whereas pretreatment with SCH23390 and haloperidol inhibited it. CONCLUSION: Our results indicate that 4-MeO-PCP and 3-MeO-PCMo induce rewarding and reinforcing effects that are probably mediated by the mesolimbic dopamine system, suggesting an abuse liability in humans.

25B-NBOMe, a novel N-2-methoxybenzyl-phenethylamine (NBOMe) derivative, may induce rewarding and reinforcing effects via a dopaminergic mechanism: Evidence of abuse potential.

An increasing number of N-2-methoxybenzyl-phenethylamine (NBOMe) derivatives are being misused worldwide, including the potent hallucinogen 2-(4-bromo-2,5-dimethoxyphenyl)-N-(2-methoxybenzyl)ethanamine (25B-NBOMe). However, the number of studies characterizing the abuse potential and psychopharmacological properties of 25B-NBOMe is limited; thus, we examined its rewarding and reinforcing effects using conditioned place preference (CPP) and self-administration (SA) tests. Pretreatment with SCH23390 (SCH), Haloperidol (HAL), and ketanserin (KS), antagonists of dopamine D1 (DRD1 ), dopamine D2 (DRD2 ), and serotonin 2A (5-HT2A receptor) receptors, respectively, was utilized during a CPP test to investigate the involvement of the dopaminergic and serotonergic systems in 25B-NBOMe-mediated effects. We also examined the effects of 25B-NBOMe on the expression of dopamine-related proteins in the nucleus accumbens (NAcc) and ventral tegmental area (VTA). Then, we measured the dopamine level, phosphorylated CREB (p-CREB), deltaFosB (ΔFosB), and brain-derived neurotrophic factor (BDNF) in the NAcc. In addition, we explored the involvement of 5-HT2A receptors in the 25B-NBOMe-induced head twitch response (HTR). We also examined the effects of 25B-NBOMe on brain wave activity using electroencephalography. 25B-NBOMe elicited CPP and SA. SCH and HAL blocked 25B-NBOMe-induced CPP, whereas KS did not. Moreover, 25B-NBOMe altered the DRD1 , DRD2 , and dopamine transporter expression and increased dopamine levels. It also induced changes in p-CREB, ΔFosB, and BDNF expression. 25B-NBOMe induced HTR and increased 5-HT2A receptor mRNA levels, effects inhibited by KS. Furthermore, 25B-NBOMe altered delta and gamma wave activity, which was normalized by SCH and HAL. These findings show that 25B-NBOMe may induce rewarding and reinforcing effects via a dopaminergic mechanism, suggesting its abuse potential.

The potent psychomotor, rewarding and reinforcing properties of 3-fluoromethamphetamine in rodents.

3-fluoromethamphetamine (3-FMA), a derivative of methamphetamine (METH), produces behavioral impairment and deficits in dopaminergic transmission in the striatum of mice. The abuse potential of 3-FMA has not been fully characterized. The aim of this study was to evaluate the effects of 3-FMA on locomotor activity as well as its rewarding and reinforcing properties in the conditioned place preference (CPP) and self-administration procedures. Intravenous (i.v.) administration of 3-FMA (0.5 and 1.0 mg/kg) significantly increased locomotor activity in a dose-dependent manner in rats. In the CPP procedure, intraperitoneal administration of 3-FMA (10 and 30 mg/kg) produced a significant alteration in place preference in mice. In the self-administration paradigms, 3-FMA showed drug-taking behavior at the dose of 0.1 mg/kg/infusion (i.v.) during 2 hr sessions under fixed ratio schedules and high breakpoints at the dose of 0.3 and 1.0 mg/kg/infusion (i.v.) during 6 hr sessions under progressive ratio schedule of reinforcement in rats. A priming injection of 3-FMA (0.4 mg/kg, i.v.), METH (0.2 mg/kg, i.v.), or cocaine (2.0 mg/kg, i.v.) reinstated 3-FMA-seeking behavior after an extinction period in 3-FMA-trained rats during 2 hr session. Taken together, these findings demonstrate robust psychomotor, rewarding and reinforcing properties of 3-FMA, which may underlie its potential for compulsive use in humans.

Integrated Non-targeted and Targeted Metabolomics Uncovers Dynamic Metabolic Effects during Short-Term Abstinence in Methamphetamine Self-Administering Rats.

Persistent neurochemical disturbances by repeating drug reward and withdrawal lead to addiction. Particularly, drug withdrawal, usually starting within hours of the last dose, is considered as a critical step in the transition to addiction and a treatment clue. The aim of this study was to uncover metabolic effects associated with methamphetamine (MA) short-term abstinence using both non-targeted and targeted metabolomics. Metabolic alterations were investigated in rat plasma collected immediately after 16 days of MA self-administration and after 12 and 24 h of abstinence. Principal component analysis revealed that the highest level of separation occurred between the 24 h and saline (control) groups based on the significantly changed ion features, 257/320/333 and 331/409/388, in the SA/12 h/24 h groups in positive and negative modes of UPLC-QTOF-ESI-MS, respectively. Targeted metabolomics revealed dynamic changes in the biosynthesis/metabolism of amino acids, including the phenylalanine, tyrosine, and tryptophan biosynthesis and the valine, leucine, and isoleucine biosynthesis. Integrating non-targeted and targeted metabolomics data uncovered rapid and distinct changes in the metabolic pathways involved in energy metabolism, the nervous system, and membrane lipid metabolism. These findings provide essential knowledge of the dynamic metabolic effects associated with short-term MA abstinence and may help identify early warning signs of MA dependence.

Interactions of Glutamatergic Neurotransmission and Brain-Derived Neurotrophic Factor in the Regulation of Behaviors after Nicotine Administration.

Nicotine causes tobacco dependence, which may result in fatal respiratory diseases. The striatum is a key structure of forebrain basal nuclei associated with nicotine dependence. In the striatum, glutamate release is increased when α7 nicotinic acetylcholine receptors expressed in the glutamatergic terminals are exposed to nicotine, and over-stimulates glutamate receptors in gamma amino-butyric acid (GABA)ergic neurons. These receptor over-stimulations in turn potentiate GABAergic outputs to forebrain basal nuclei and contribute to the increase in psychomotor behaviors associated with nicotine dependence. In parallel with glutamate increases, nicotine exposure elevates brain-derived neurotrophic factor (BDNF) release through anterograde and retrograde targeting of the synapses of glutamatergic terminals and GABAergic neurons. This article reviews nicotine-exposure induced elevations of glutamatergic neurotransmission, the bidirectional targeting of BDNF in the striatum, and the potential regulatory role played by BDNF in behavioral responses to nicotine exposure.

5-Methoxy-α-methyltryptamine (5-MeO-AMT), a tryptamine derivative, induces head-twitch responses in mice through the activation of serotonin receptor 2a in the prefrontal cortex.

5-Methoxy-α-methyltryptamine (5-MeO-AMT) is a tryptamine derivative that is used recreationally because of its reported hallucinogenic and mood elevating effects. Studies suggest that the psychopharmacological effects of tryptamines involve serotonin receptor 2a (5-HTR2a) activation in the brain. The head-twitch response (HTR) is widely used as a behavioral correlate for assessing 5-HTR2a agonist activity of a drug. Thus, we investigated whether 5-MeO-AMT induces HTR in mice and explored its mechanism of action. 5-MeO-AMT (0.3, 1, 3, 10 mg/kg) was administered once a day for 7 days, and the HTR was measured after 1 day (acute) and 7 days (repeated) of administration. Another cohort of mice was treated with 5-HTR2a antagonist ketanserin (KS) before 5-MeO-AMT administration. We measured 5-HTR2a and 5-HTR2c mRNA levels in the prefrontal cortex of the mice treated acutely or repeatedly with 5-MeO-AMT. We performed western blotting to determine the effects of the drug on the expression of G protein (Gq/11), protein kinase C gamma (PKC-γ), and extracellular signal-regulated kinases 1/2 (ERK1/2), in addition to PKC-γ and ERK1/2 phosphorylation. Additionally, we evaluated potential rewarding and reinforcing effects of 5-MeO-AMT using locomotor sensitization, conditioned place preference (CPP), and self-administration (SA) paradigms. Acute 5-MeO-AMT administration elicited the HTR, while repeated administration resulted in tolerance. KS blocked the 5-MeO-AMT-induced HTR. 5-MeO-AMT increased 5-HTR2a mRNA levels and induced PKC-γ phosphorylation in the prefrontal cortex. 5-MeO-AMT did not induce locomotor sensitization, CPP, or SA. This study shows that 5-MeO-AMT induces HTR through 5-HTR2a activation in the prefrontal cortex, and may have low potential for abuse.

Activation of Protein Kinase G After Repeated Cocaine Administration Is Necessary for the Phosphorylation of α-Amino-3-Hydroxy-5-Methyl-4-Isoxazolepropionic Acid Receptor GluA1 at Serine 831 in the Rat Nucleus Accumbens.

Phosphorylation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors in the striatum plays a crucial role in regulating the receptor-coupled signaling cascades leading to behavioral changes associated with psychostimulant exposure. The present study determined if activation of protein kinase G (PKG) contributes to the phosphorylation of AMPA receptor GluA1 subunit at the position of serine 831 (GluA1-S831) in the rat nucleus accumbens (NAc) after repeated cocaine administration. The results demonstrated that repeated intraperitoneal (i.p.) injections of cocaine (20 mg/kg) once a day for seven consecutive days significantly increased the level of phosphorylated (p)GluA1-S831. This increase was decreased by the intra-NAc infusion of either the cyclic guanosine monophosphate (cGMP) analog, Rp-8-Br-PET-cGMPS (5 nmol/1 µL), or the PKG inhibitor, KT5823 (2 nmol/1 µL). Repeated cocaine administration increased PKG binding activity to GluA1. This increase in GluA1-S831 phosphorylation after repeated cocaine administration was decreased by the intra-NAc infusion of the synthetic peptide (Tat-tagged interfering peptide (Tat-GluA1-i)), that interferes with the binding of PKG to GluA1. Intra-NAc infusion of the interfering peptide also reduced the repeated cocaine-induced increase in locomotor activity. These findings suggest that activated PKG, after repeated exposure to cocaine, binds to AMPA receptor GluA1 and is required for the phosphorylation of S831, contributing to behavioral changes.