Amphetamine Research Articles

The protein kinase Cβ-selective inhibitor, enzastaurin, attenuates amphetamine-stimulated locomotor activity and self-administration behaviors in rats

Pathological amphetamine (AMPH) use is a serious public health concern with no pharmacological treatment options. Protein kinase Cβ (PKCβ) has been implicated in the mechanism of action of AMPH, such that inhibition of PKCβ attenuates AMPH-stimulated dopamine efflux in vivo. With this in mind, inhibition of PKCβ may be a viable therapeutic target for AMPH use disorder. The purpose of this study is to demonstrate that selective pharmacological inhibition of PKCβ alters AMPH-stimulated behaviors in rats. Rats were administered intracerebroventricular (i.c.v.) injections of the PKCβ-selective inhibitor enzastaurin 0.5, 3, 6, or 18h before evaluating AMPH-stimulated locomotion (0.32-3.2mg/kg). Rats were trained to make responses for different doses of AMPH infusions or sucrose under a fixed ratio 5 schedule of reinforcement, and the effects of enzastaurin pretreatment 3 or 18h prior to a self-administration session were determined. Also, the effect of enzastaurin on AMPH-stimulated PKC activity in the ventral striatum was evaluated. A large dose of enzastaurin (1nmol) decreased AMPH-stimulated locomotor activity 0.5h following enzastaurin administration. Small doses of enzastaurin (10-30pmol) attenuated AMPH-stimulated locomotor activity and shifted the AMPH dose-effect curve to the right following an 18-h pretreatment. Rats pretreated with enzastaurin 18h, but not 3, prior to a self-administration session showed a decrease in the number of responses for AMPH, shifted the ascending limb of the amphetamine dose effect curve, and produced no change in responses for sucrose. AMPH-stimulated PKC activity was decreased following a 0.5- or 18-h pretreatment, but not a 3-h pretreatment of enzastaurin. These results demonstrate that inhibition of PKCβ will decrease AMPH-stimulated behaviors and neurobiological changes and suggest that PKCβ is potentially a viable target for AMPH use disorder.

The Effects of Amphetamine and Methamphetamine on the Release of Norepinephrine, Dopamine and Acetylcholine From the Brainstem Reticular Formation.

Amphetamine (AMPH) and methamphetamine (METH) are widely abused psychostimulants, which produce a variety of psychomotor, autonomic and neurotoxic effects. The behavioral and neurotoxic effects of both compounds (from now on defined as AMPHs) stem from a fair molecular and anatomical specificity for catecholamine-containing neurons, which are placed in the brainstem reticular formation (RF). In fact, the structural cross-affinity joined with the presence of shared molecular targets between AMPHs and catecholamine provides the basis for a quite selective recruitment of brainstem catecholamine neurons following AMPHs administration. A great amount of investigations, commentary manuscripts and books reported a pivotal role of mesencephalic dopamine (DA)-containing neurons in producing behavioral and neurotoxic effects of AMPHs. Instead, the present review article focuses on catecholamine reticular neurons of the low brainstem. In fact, these nuclei add on DA mesencephalic cells to mediate the effects of AMPHs. Among these, we also include two pontine cholinergic nuclei. Finally, we discuss the conundrum of a mixed neuronal population, which extends from the pons to the periaqueductal gray (PAG). In this way, a number of reticular nuclei beyond classic DA mesencephalic cells are considered to extend the scenario underlying the neurobiology of AMPHs abuse. The mechanistic approach followed here to describe the action of AMPHs within the RF is rooted on the fine anatomy of this region of the brainstem. This is exemplified by a few medullary catecholamine neurons, which play a pivotal role compared with the bulk of peripheral sympathetic neurons in sustaining most of the cardiovascular effects induced by AMPHs.

T121. Effects of Developmental Omega-3 Fatty Acid Deficiency on Dendritic Spine Density and Plasticity in the Adult Rat Medial Prefrontal Cortex

Mood disorders are associated with omega-3 fatty acid deficits and structural and functional connectivity abnormalities within prefrontal cortex (PFC) networks. Reciprocal connections between the medial PFC (mPFC) and amygdala undergo robust synaptic pruning during adolescence in rats. Prior evidence suggests that the omega-3 fatty acids promote synaptogenesis and synaptic pruning. However, the role of omega-3 fatty acids in mPFC structural maturation and plasticity is not known. This study investigated whether developmental deficits in brain DHA accrual alter basal and amphetamine (AMPH)-induced increases in dendritic spine density in the adult rat mPFC.

F74. Impaired Fear Extinction in Omega-3 Fatty Acid Deficient Rats is Attenuated by Chronic Amphetamine Treatment

Mood disorders are associated altered prefrontal cortex (PFC) and amygdala (AMY) structural and functional connectivity, and deficits in the omega-3 fatty acid docosahexaenoic acid (DHA). Reciprocal connections between the rat PFC and basolateral AMY mediate conditioned fear acquisition and extinction, and this circuit undergoes robust synaptic pruning during adolescence. DHA promotes synaptogenesis and synaptic pruning, and chronic amphetamine (AMPH) treatment induces synaptic reorganization in the rat PFC. The present study investigated whether developmental deficits in brain DHA accrual and/or chronic AMPH exposure impact fear conditioning in young adulthood.

New Formulations of Stimulants: An Update for Clinicians.

In the last 15 years, there has been a marked increase in the number of available stimulant formulations with the emphasis on long-acting formulations, and the introduction of several novel delivery systems such as orally dissolving tablets, chewable tablets, extended-release liquid formulations, transdermal patches, and novel "beaded" technology. All of these formulations involve changes to the pharmaceutical delivery systems of the two existing compounds most commonly employed to treat attention-deficit/hyperactivity disorder (ADHD), amphetamine (AMP) and methylphenidate (MPH). In addition to these new formulations, our knowledge about the individual differences in response has advanced and contributes to a more nuanced approach to treatment. The clinician can now make increasingly informed choices about these formulations and more effectively individualize treatment in a way that had not been possible before. In the absence of reliable biomarkers that can predict individualized response to ADHD treatment, clinical knowledge about differences in MPH and AMP pharmacodynamics, pharmacokinetics, and metabolism can be utilized to personalize treatment and optimize response. Different properties of these new formulations (delivery modality, onset of action, duration of response, safety, and tolerability) will most likely weigh heavily into the clinician's choice of formulation. To manage the broad range of options that are now available, clinicians should familiarize themselves in each of these categories for both stimulant compounds. This review is meant to serve as an update and a guide to newer stimulant formulations and includes a brief review of ADHD and stimulant properties.

Determination of amphetamine-type stimulants in urine samples using microextraction by packed sorbent and gas chromatography-mass spectrometry

The aim of this work was the development, optimization and full validation of a method applying microextraction by packed sorbent (MEPS) coupled to gas chromatography–mass spectrometry (GC–MS) to determine amphetamine (AMP), methamphetamine (MAMP), 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxyethylmethamphetamine (MDMA), 3,4-methylenedioxy-N-methyl-α-ethylfenilethylamine (MBDB), and 3,4-methylenedioxy-N-ethylamphetamine (MDE) in urine samples.Using 200 μL of sample, the MEPS procedure was optimized concerning type of sorbent, sample dilution, number of strokes, activation of the ion exchange mechanism and composition of both washing and elution solvents.The method was fully validated according to the Food and Drug Administration and the Scientific Working Group of Forensic Toxicology guidelines for the validation of bioanalytical methods. The studied parameters included selectivity, calibration model and linearity, limits of detection and quantification, precision, accuracy, stability, dilution integrity and recoveries. Linearity was obtained in the range of 25–1000 ng/mL for MAMP, MBDB and MDE, 35–1000 ng/mL for AMP and MDMA, and 50–1000 ng/mL for MDA, with coefficients of determination (R2) >0.99 for all analytes. Both intra- and inter-day precision and accuracy were adequate, and coefficients of variation lower than 15% and mean relative errors (RE) within a range of ±15% of the theoretical concentrations were obtained for all compounds under study. Analyte recoveries ranged from 19 to 71%, allowing LLOQs ≤50 ng/mL.

Do cosmetic treatments increase the incorporation of amphetamines into hair?

According to several studies, the concentration of drugs in hair may decrease by bleaching or dyeing; however, at the same time, treated hair could incorporate greater quantity of drugs from sweat or sebum than intact hair. The aim of this study is to assess the incorporation of amphetamine (AP), methamphetamine (MA) and 3,4-methylenedioxy-methamphetamine (MDMA) from sweat or sebum to virgin, dyed, and bleached hair. Drug-free head hair samples (from 20 volunteers) were divided into four locks, one of them was left untreated, another was subjected to dyeing treatment, and the last two were subjected to different degree of bleaching. Virgin, dyed, mildly as well as severely bleached locks of hair were exposed to artificial sweat or sebum containing AP, MA, and MDMA (500 ng/g), at 37 °C for a time period of 8 and 24 h, respectively. After the exposure, all the hair samples were tested by GC/MS in SIM mode, applying an already published method. Drug concentrations in hair ranged 0.41 to 2.20 ng/mg from artificial sweat, while only reached 0.27 ng/mg from artificial sebum. The differences of each drug concentration (AP, MA, MDMA) between different kind of hair were statistically compared: virgin hair vs. dyed hair, virgin hair vs mildly bleached hair, virgin hair vs. severely bleached hair. The differences between different drugs concentration within each kind of hair (virgin, dyed, mildly and severely bleached) were, as well, statistically compared: AP vs. MA, AP vs. MDMA, MA vs. MDMA. In all cases, differences were calculated between locks of hair from the same volunteer. The paired samples Student's t-test was applied in cases where the concentration differences followed the normal law. In these cases the extent of the difference was calculated with a confidence interval of 95%. The paired samples Wilcoxon's t -test was applied in cases where the concentration differences did not follow the normal law. Regarding the incorporation of AP, MA and MDMA from artificial sweat in vitro, the analysis provides evidence that the mean concentration for each drug in dyed or bleached hair is higher than the mean concentration in virgin hair, and that the differences between means are likely to be between 0.15 and 0.57 ng/mg, depending on the drug and the compared pairs. The incorporation of different drugs in the same kind of hair shows little differences in virgin and dyed hair, but the mean concentration of MDMA in bleached hair is higher than the mean concentration of AP; the differences between means are likely to be between 0.08 and 0.16 ng/mg. Regarding the incorporation of AP, MA and MDMA from artificial sebum in vitro, the differences between mean concentrations are lower for every compared pair, in relation to the incorporation from sweat. AP is not incorporated into hair from sweat or sebum to a greater extent than MDMA. Higher positivity rates for AP have been found in dyed or bleached hair in relation to virgin hair, detecting both significant [1] and non-significant [2] differences in the target populations. Based on these facts and the quantitative results of in vitro incorporation of amphetamine derivatives in hair, when interpreting the results from cosmetically treated hair, consideration should be given not only to the possibility that the treatment will lead to a decrease in drug concentration, but also to an increase. This consideration is particularly relevant if the detected levels are close to the cut-off.

Stress changes amphetamine response, D2 receptor expression and epigenetic regulation in low-anxiety rats

The aim of this study was to assess the influence of chronic restraint stress on amphetamine (AMPH)-related appetitive 50-kHz ultrasonic vocalisations (USVs) in rats differing in freezing duration in a contextual fear test (CFT), i.e. HR (high-anxiety responsive) and LR (low-anxiety responsive) rats. The LR and the HR rats, previously exposed to an AMPH binge experience, differed in sensitivity to AMPH's rewarding effects, measured as appetitive vocalisations. Moreover, chronic restraint stress attenuated AMPH-related appetitive vocalisations in the LR rats but had no influence on the HR rats' behaviour. To specify, the restraint LR rats vocalised appetitively less in the AMPH-associated context and after an AMPH challenge than the control LR rats. This phenomenon was associated with a decrease in the mRNA level for D2 dopamine receptor in the amygdala and its protein expression in the basal amygdala (BA) and opposite changes in the nucleus accumbens (NAc) - an increase in the mRNA level for D2 dopamine receptor and its protein expression in the NAc shell, compared to control conditions. Moreover, we observed that chronic restraint stress influenced epigenetic regulation in the LR and the HR rats differently. The contrasting changes were observed in the dentate gyrus (DG) of the hippocampus - the LR rats presented a decrease, but the HR rats showed an increase in H3K9 trimethylation. The restraint LR rats also showed higher miR-494 and miR-34c levels in the NAc than the control LR group. Our study provides behavioural and biochemical data concerning the role of differences in fear-conditioned response in stress vulnerability and AMPH-associated appetitive behaviour. The LR rats were less sensitive to the rewarding effects of AMPH when previously exposed to chronic stress that was accompanied by changes in D2 dopamine receptor expression and epigenetic regulation in mesolimbic areas.

Swimming Induced Paralysis to Assess Dopamine Signaling in Caenorhabditis elegans.

The swimming assay described in this protocol is a valid tool to identify proteins regulating the dopaminergic synapses. Similar to mammals, dopamine (DA) controls several functions in C. elegans including learning and motor activity. Conditions that stimulate DA release (e.g., amphetamine (AMPH) treatments) or that prevent DA clearance (e.g., animals lacking the DA transporter (dat-1) which are incapable of reaccumulating DA into the neurons) generate an excess of extracellular DA ultimately resulting in inhibited locomotion. This behavior is particularly evident when animals swim in water. In fact, while wild-type animals continue to swim for an extended period, dat-1 null mutants and wild-type treated with AMPH or inhibitors of the DA transporter sink to the bottom of the well and do not move. This behavior is termed "Swimming Induced Paralysis" (SWIP). Although the SWIP assay is well established, a detailed description of the method is lacking. Here, we describe a step-by-step guide to perform SWIP. To perform the assay, late larval stage-4 animals are placed in a glass spot plate containing control sucrose solution with or without AMPH. Animals are scored for their swimming behavior either manually by visualization under a stereoscope or automatically by recording with a camera mounted on the stereoscope. Videos are then analyzed using a tracking software, which yields a visual representation of thrashing frequency and paralysis in the form of heat maps. Both the manual and automated systems guarantee an easily quantifiable readout of the animals' swimming ability and thus facilitate screening for animals bearing mutations within the dopaminergic system or for auxiliary genes. In addition, SWIP can be used to elucidate the mechanism of action of drugs of abuse such as AMPH.

EAAT3 endocytosis activated by psychostimulants in diverse populations of neurons

The primary mechanism of action of psychostimulants, including amphetamine (AMPH), has largely been attributed generally to an increase in extracellular dopamine. Dopamine potentiation has been ascribed to several mechanisms including endocytosis of the dopamine transporter, DAT. We have found that this cascade involves entry of AMPH into the cell through DAT, stimulation of an intracellular GPCR for trace amines, TAAR1, and activation of the small GTPase, RhoA. Changes in extracellular glutamate concentrations have also been reported in response to AMPH and we have found that the neuronal glutamate transporter, EAAT3, also undergoes endocytosis via this cascade in dopamine neuron cultures, in acute brain slices and in vivo. EAAT3 is broadly expressed in neuronal populations throughout the brain, suggesting additional actions of AMPH on glutamatergic signaling in cells other than dopamine neurons. AMPH is a transported inhibitor of DAT as well as the norepinephrine transporter, NET, so we explored AMPH‐induced EAAT3 trafficking in NET(+) neurons. By total internal reflection fluorescence (TIRF) microscopy we found that AMPH can cause endocytosis of EAAT3 as well as NET. We developed NET(+) primary cultures derived from E15 murine locus coeruleus. Catecholamine neurotransmitters enter these cells through a desipramine‐sensitive pathway, indicating that this transport is mediated by NET. These cultures also exhibit sodium‐dependent and dihydrokainate‐insensitive tritiated‐glutamate uptake that is mediated by EAAT3. Pretreatment with AMPH decreases both NET and EAAT3 transport capacity in these cultures. Furthermore, through the use of a RhoA inhibitor, we determined that this loss depends on activation of RhoA, as seen previously for AMPH‐mediated internalization of DAT and EAAT3 in midbrain dopamine neuronal cultures. These data indicate that TAAR1 agonists, such as AMPH and dopamine, can affect glutamate signaling through internalization of EAAT3 in noradrenergic as well as dopaminergic neurons.Support or Funding InformationThis work was supported by Intramural Research at the NIH, NIMH.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Enhanced Dopamine in Prodromal Schizophrenia (EDiPS): a new animal model of relevance to schizophrenia

One of the most robust neurochemical abnormalities reported in patients living with schizophrenia is an increase in dopamine (DA) synthesis and release in the dorsal striatum (DS). Importantly, it appears that this increase progresses as a patient transitions from a prodromal stage to the clinical diagnosis of schizophrenia. Here we have recreated this pathophysiology in an animal model by increasing the capacity for DA synthesis preferentially within the DS. To achieve this we administer a genetic construct containing the rate-limiting enzymes in DA synthesis—tyrosine hydroxylase (TH), and GTP cyclohydrolase 1 (GCH1) (packaged within an adeno-associated virus)—into the substantia nigra pars compacta (SNpc) of adolescent animals. We refer to this model as “Enhanced Dopamine in Prodromal Schizophrenia” (EDiPS). We first confirmed that the TH enzyme is preferentially increased in the DS. As adults, EDiPS animals release significantly more DA in the DS following a low dose of amphetamine (AMPH), have increased AMPH-induced hyperlocomotion and show deficits in pre-pulse inhibition (PPI). The glutamatergic response to AMPH is also altered, again in the DS. EDiPS represents an ideal experimental platform to (a) understand how a preferential increase in DA synthesis capacity in the DS relates to “positive” symptoms in schizophrenia; (b) understand how manipulation of DS DA may influence other neurotransmitter systems shown to be altered in patients with schizophrenia; (c) allow researchers to follow an “at risk”-like disease course from adolescence to adulthood; and (d) ultimately allow trials of putative prophylactic agents to prevent disease onset in vulnerable populations.

Influence of non-metallic atoms on the absorption of amphetamines on B12N12 nano-cages

Density functional theory (DFT) calculations at B3LYP/6-31+G(d) level were employed to investigate the influence of the non-metal encapsulation of the second row of the periodic table of elements on the optoelectronic response properties. Besides, the adsorption of amphetamine (AMP) on the surface of B12N12 nano-cage quantum theory of atoms in molecules (QTAIM) was employed to analyze the topology of electron density and bonding properties of the studied systems. It is demonstrated that the energy gap of the encapsulated nano-cages reduces significantly as compared to pristine B12N12 leading to an increase in the electrical conductance of the nano-cage. Aside from that, encapsulation drastically enhances the interaction of AMP with B12N12 nano-cage. Among non-metals of the second row of the periodic table, fluorine has the highest influence on the adsorption energy of the AMP and also on the surface of B12N12 nano-cage. However, carbon in triplet-state encapsulation greatly enhances the sensitivity of the B12N12 nano-cage to AMP. Finally, QTAIM results indicated that encapsulation increases the covalent character of N–B bonding.

Efeito modulador da Ritalina® (metilfenidato) sobre a ação carcinogênica da doxorrubicina em Drosophila melanogaster

Introdução: A Ritalina® (metilfenidato) é um estimulante do sistema nervoso central, derivado da anfetamina. Ficou conhecida por seu uso em crianças e adultos diagnosticados com transtornos de déficit de atenção e hiperatividade, e alternativamente para tratamento de narcolepsia, obesidade e como estimulante para estudantes. Objetivo: Avaliar o efeito carcinogênico e/ou anticarcinogênico da Ritalina®. Método: Para tanto, larvas wts+/+mwh foram tratadas com o indutor tumoral doxorrubicina (0,4 mM) e com três diferentes concentrações de Ritalina® (100; 200 e 400 μM). Resultados: Mostraram que a Ritalina® apresentou atividade anticarcinogênica, visto que houve diferença estatisticamente significativa (p<0,05) nas frequências de tumores identificados com a presença da referida substância, quando comparadas à frequência de tumores no controle positivo isolado. Conclusão: Sendo assim, é possível inferir que, nas presentes condições experimentais, a Ritalina® apresentou efeito modulador sobre danos induzidos pela doxorrubicina, reduzindo a frequência de tumores em todas as concentrações testadas em células somáticas de Drosophila melanogaster.

Omega-3 decreases D1 and D2 receptors expression in the prefrontal cortex and prevents amphetamine-induced conditioned place preference in rats

Amphetamine (AMPH) abuse is a serious public health problem due to the high addictive potential of this drug, whose use is related to severe brain neurotoxicity and memory impairments. So far, therapies for psychostimulant addiction have had limited efficacy. Omega-3 polyunsaturated fatty acids (n-3 PUFA) have shown beneficial influences on the prevention and treatment of several diseases that affect the central nervous system. Here, we assessed the influence of fish oil (FO), which is rich in n-3 PUFA, on withdrawal and relapse symptoms following re-exposure to AMPH. Male Wistar rats received d,l-AMPH or vehicle in the conditioned place preference (CPP) paradigm for 14 days. Then, half of each experimental group was treated with FO (3 g/kg, p.o.) for 14 days. Subsequently, animals were re-exposed to AMPH-CPP for three additional days, in order to assess relapse behavior. Our findings have evidenced that FO prevented relapse induced by AMPH reconditioning. While FO prevented AMPH-induced oxidative damages in the prefrontal cortex, molecular assays allowed us to observe that it was also able to modulate dopaminergic cascade markers (DAT, TH, VMAT-2, D1R and D2R) in the same brain area, thus preventing AMPH-induced molecular changes. To the most of our knowledge, this is the first study to show a natural alternative tool which is able to prevent psychostimulant relapse following drug withdrawal. This non-invasive and healthy nutraceutical may be considered as an adjuvant treatment in detoxification clinics.

Identification of whole blood mRNA and microRNA biomarkers of tissue damage and immune function resulting from amphetamine exposure or heat stroke in adult male rats.

This work extends the understanding of how toxic exposures to amphetamine (AMPH) adversely affect the immune system and lead to tissue damage. Importantly, it determines which effects of AMPH are and are not due to pronounced hyperthermia. Whole blood messenger RNA (mRNA) and whole blood and serum microRNA (miRNA) transcripts were identified in adult male Sprague-Dawley rats after exposure to toxic AMPH under normothermic conditions, AMPH when it produces pronounced hyperthermia, or environmentally-induced hyperthermia (EIH). mRNA transcripts with large increases in fold-change in treated relative to control rats and very low expression in the control group were a rich source of organ-specific transcripts in blood. When severe hyperthermia was produced by either EIH or AMPH, significant increases in circulating organ-specific transcripts for liver (Alb, Fbg, F2), pancreas (Spink1), bronchi/lungs (F3, Cyp4b1), bone marrow (Np4, RatNP-3b), and kidney (Cesl1, Slc22a8) were observed. Liver damage was suggested also by increased miR-122 levels in the serum. Increases in muscle/heart-enriched transcripts were produced by AMPH even in the absence of hyperthermia. Expression increases in immune-related transcripts, particularly Cd14 and Vcan, indicate that AMPH can activate the innate immune system in the absence of hyperthermia. Most transcripts specific for T-cells decreased 50–70% after AMPH exposure or EIH, with the noted exception of Ccr5 and Chst12. This is probably due to T-cells leaving the circulation and down-regulation of these genes. Transcript changes specific for B-cells or B-lymphoblasts in the AMPH and EIH groups ranged widely from decreasing ≈ 40% (Cd19, Cd180) to increasing 30 to 100% (Tk1, Ahsa1) to increasing ≥500% (Stip1, Ackr3). The marked increases in Ccr2, Ccr5, Pld1, and Ackr3 produced by either AMPH or EIH observed in vivo provide further insight into the initial immune system alterations that result from methamphetamine and AMPH abuse and could modify risk for HIV and other viral infections.

Dynamic interactions of ceftriaxone and environmental variables suppress amphetamine seeking

Extrasynaptic glutamate within the nucleus accumbens (NAc) is a driver of relapse. Cocaine, ethanol, and methamphetamine reduce the expression of cystine-glutamate antiporter (xCT) and primary glial glutamate transporter 1 (GLT1) leading to increased extrasynaptic glutamate. Ceftriaxone (CTX) restores xCT and GLT1 expression and effectively suppresses cocaine and ethanol reinstatement, however, the effects of CTX on amphetamine (AMP) reinstatement are not determined. Rodents were reared in an enriched condition (EC), isolated (IC), or standard condition (SC) and trained in AMP self-administration (0.1 mg/kg/infusion). EC, IC, and SC rats received injections of SAL or CTX (200 mg/kg) after daily extinction sessions. Then rats were tested in cue- and AMP-induced reinstatement tests. We hypothesized that EC rearing would reduce reinstatement by altering GLT1 or xCT expression in the NAc and medial prefrontal cortex (mPFC). In Experiment 2, pair-housed rats received once-daily AMP (1.0 mg/kg i.p.) or SAL for eight days followed by once-daily CTX (200 mg/kg i.p.) or SAL injections for 10 days. CTX treatment reduced cue-induced drug seeking in EC rats but not IC or SC rats. In an AMP-induced reinstatement test, CTX reduced AMP-induced drug seeking in EC and SC rats, but not IC rats. Western blot analyses revealed that AMP self-administration and non-contingent repeated AMP exposure did not downregulate GLT1 or xCT in the NAc or mPFC. Therefore, the ability for EC housing to reduce amphetamine seeking may work through other mechanisms.

A genetic deletion of the serotonin transporter differentially influences the behavioural effects of MDMA.

While (±)-3,4-methylenedioxymethamphetamine (MDMA) primarily induces serotonin release, it also affects dopamine and noradrenaline transmission. It is, however, unclear what role each of these neurotransmitters play in the behavioural profile of MDMA. In this study we used the drug discrimination (DD) and the acoustic startle (ASR) paradigms to examine the behaviour of rats with and without a genetic deletion of the serotonin transporter SERT (SERT-/- and SERT+/+ rats). In DD, rats were trained to respond on different levers following an injection of 1.5 mg/kg MDMA, or saline. After acquisition, they were given a challenge dose of 0.5 mg/kg amphetamine (AMPH). In the ASR paradigm, SERT+/+ and SERT-/- rats were given 0, 5 or 10 mg/kg MDMA. In DD, significantly fewer SERT-/- rats acquired MDMA discrimination. When the acquirers were challenged with AMPH, SERT+/+ showed partial, while SERT-/- rats showed full generalisation to MDMA. In the ASR paradigm, MDMA significantly reduced prepulse inhibition and startle habituation in SERT+/+ rats, while having no effect in SERT-/- rats. Together these data suggest that in wildtype rats the interoceptive cues of MDMA are primarily mediated by serotonin and to a lesser extent by dopamine and noradrenaline, while the effects in the startle paradigm are almost exclusively mediated via serotonin. Together, these data contribute to our understanding of the complex pharmacodynamics of MDMA.

Modafinil reduces amphetamine preference and prevents anxiety-like symptoms during drug withdrawal in young rats: Involvement of dopaminergic targets in VTA and striatum

Drug abuse and addiction are overwhelming health problems mainly during adolescence. Based on a previous study of our research group, the rats that received modafinil (MD) during the adolescence showed less preference for amphetamine (AMPH) in adulthood. Our current hypothesis is that MD will show beneficial effects against AMPH preference and abstinence symptoms during adolescence, a critical lifetime period when drug hedonic effects are more pronounced. We investigated the influence of MD pretreatment on AMPH preference in conditioned place preference (CPP) paradigm in adolescent rats and anxiety-like symptoms during drug withdrawal (48 h after the last AMPH dose) in elevated plus maze (EPM) task. Besides that, oxidative and molecular status were evaluated in the ventral tegmental area (VTA) and striatum. Our findings showed, as it was expected, that adolescent animals developed AMPH preference together with anxiety-like symptoms during the drug withdrawal while the MD pretreatment prevented those behaviors. Besides promoting benefits on reward parameters, MD was able to preserve VTA and striatum from oxidative damages. This was observed by the increased catalase activity and reduced generation of reactive species and lipid peroxidation, which were inversely modified by AMPH exposure. At molecular level, MD exerted an interesting modulatory activity on the VTA and induced an up-regulation in striatal dopaminergic targets (TH, DAT, D1R and D2R). So far, during the adolescence, MD presented beneficial behavioral outcomes that could be attributed to its modulatory activity on the striatal dopaminergic system in an attempt to maintain the adequate dopamine levels.

Role of nitric oxide in psychostimulant-induced neurotoxicity.

In recent decades, consumption of psychostimulants has been significantly increased all over the world, while exact mechanisms of neurochemical effects of psychomotor stimulants remained unclear. It is assumed that the neuronal messenger nitric oxide (NO) may be involved in mechanisms of neurotoxicity evoked by psychomotor stimulants. However, possible participation of NO in various pathological states is supported mainly by indirect evidence because of its short half-life in tissues. Aim of this review is to describe the involvement of NO and the contribution of lipid peroxidation (LPO) and acetylcholine (ACH) release in neurotoxic effects of psychostimulant drugs. NO was directly determined in brain structures by electron paramagnetic resonance (EPR). Both NO generation and LPO products as well as release of ACH were increased in brain structures following four injections of amphetamine (AMPH). Pretreatment of rats with the non-selective inhibitor of NO-synthase (NOS) N-nitro-L-arginine or the neuronal NOS inhibitor 7-nitroindazole significantly reduced increase of NO generation as well as the rise of ACH release induced by AMPH. Both NOS inhibitors injected prior to AMPH had no effect on enhanced levels of LPO products. Administration of the noncompetitive NMDA receptor antagonist dizocilpine abolished increase of both NO content and concentration of LPO products induced by of the psychostimulant drug. Dizocilpine also eliminated the influence of AMPH on the ACH release. Moreover, the neurochemical and neurotoxic effects of the psychostimulant drug sydnocarb were compared with those of AMPH. Single injection of AMPH showed a more pronounced increase in NO and TBARS levels than after an equimolar concentration of sydnocarb. The findings demonstrate the crucial role of NO in the development of neurotoxicity elicited by psychostimulants and underline the key role of NOS in AMPH-induced neurotoxicity.

Sex hormones mediate the behavioral and neurochemical response to d-amphetamine: A [11C]-(+)-PHNO study in healthy female subjects

Psychostimulants have been shown to affect brain regions involved in the process of learning and memory consolidation. It has been shown that females are more sensitive to the effects of drugs than males. The aim of our study was to investigate how prenatal methamphetamine (MA) exposure and application of amphetamine (AMP) in adulthood would affect spatial learning of adult female and male rats. Mothers of the tested offspring were exposed to injections of MA (5 mg/kg) or saline (SA) throughout the entire gestation period. Cognitive functions of adult rats were evaluated in the Morris Water Maze (MWM) tests. Adult offspring were injected daily with AMP (5 mg/kg) or SA through the period of MWM testing. Our data from the MWM tests demonstrates the following. Prenatal MA exposure did not change the learning ability of adult male and female rats. However, AMP administration to adult animals affected cognitive function in terms of exacerbation of spatial learning (increasing the latency to reach the hidden platform, the distance traveled and the search error) only in female subjects. There were sex differences in the speed of swimming. Prenatal MA exposure and adult AMP treatment increased the speed of swimming in female groups greater than in males. Overall, the male subjects showed a better learning ability than females. Thus, our results indicate that the adult AMP treatment affects the cognitive function and behavior of rats in a sex-specific manner, regardless of prenatal exposure.