Neither Amphetamine nor Sub-Anesthetic Ketamine Treatment during Adolescence Impairs Devaluation in Rats Tested during Adulthood.

BACKGROUND: Much of the existing animal literature on the devaluation task suggests that prior repeated exposure to drugs of abuse during adulthood can impair goal-directed action, but the literature on human drug users is mixed. Also, the initiation of drug use often occurs during adolescence, but examinations of the effects of drug exposure during adolescence on behavior in the devaluation task are lacking. METHODS: We examined whether repeated exposure during adolescence to amphetamine (3 mg/kg injections every-other day from post-natal day 27-45) or ketamine (twice daily 30 mg/kg injections from post-natal day 35-44) would impair behavior in a devaluation test when tested drug-free in adulthood. Rats were trained to press a left lever with a steady cue-light above it for one reinforcer and a right lever with a flashing cue-light above it for a different reinforcer. We tested whether any impairments in goal-directed action could be overcome by compensation between strategies by giving rats information based on lever-location and cue-lights during the test that was either congruent (allowing compensation) or incongruent (preventing compensation between strategies) with the configurations during training. RESULTS: Our results provided no evidence for impairment of goal-directed action during adulthood after adolescent amphetamine or ketamine exposure. CONCLUSIONS: We discuss possible reasons for this discrepancy with the prior literature, including (1) the age of exposure and (2) the pattern in the previous literature that most previous demonstrations of drug exposure impairing devaluation in laboratory animals may be attributed to either drug-associated cues present in the testing environment and/or accelerated habit learning in tasks that predispose laboratory animals towards habit formation with extended training (with training procedures that should resist the formation of habits in the current experiment). However, additional research is needed to examine the effects of these factors, as well a potential role for the particular doses and washout periods to determine the cause of our finding of no devaluation impairment after drug exposure.

Development of a novel rodent rapid serial visual presentation task reveals dissociable effects of stimulant versus nonstimulant treatments on attentional processes.

The rapid serial visual presentation (RSVP) task and continuous performance tasks (CPT) are used to assess attentional impairments in patients with psychiatric and neurological conditions. This study developed a novel touchscreen task for rats based on the structure of a human RSVP task and used pharmacological manipulations to investigate their effects on different performance measures. Normal animals were trained to respond to a target image and withhold responding to distractor images presented within a continuous sequence. In a second version of the task, a false-alarm image was included, so performance could be assessed relative to two types of nontarget distractors. The effects of acute administration of stimulant and nonstimulant treatments for ADHD (amphetamine and atomoxetine) were tested in both tasks. Methylphenidate, ketamine, and nicotine were tested in the first task only. Amphetamine made animals more impulsive and decreased overall accuracy but increased accuracy when the target was presented early in the image sequence. Atomoxetine improved accuracy overall with a specific reduction in false-alarm responses and a shift in the attentional curve reflecting improved accuracy for targets later in the image sequence. However, atomoxetine also slowed responding and increased omissions. Ketamine, nicotine, and methylphenidate had no specific effects at the doses tested. These results suggest that stimulant versus nonstimulant treatments have different effects on attention and impulsive behaviour in this rat version of an RSVP task. These results also suggest that RSVP-like tasks have the potential to be used to study attention in rodents.

Reassessment of amphetamine- and phencyclidine-induced locomotor hyperactivity as a model of psychosis-like behavior in rats.

Locomotor hyperactivity induced by psychotomimetic drugs, such as amphetamine and phencyclidine, is widely used as an animal model of psychosis-like behaviour and is commonly attributed to an interaction with dopamine release and N-methyl-D-aspartate (NMDA) receptors, respectively. However, what is often not sufficiently taken into account is that the pharmacological profile of these drugs is complex and may involve other neurotransmitter/receptor systems. Therefore, this study aimed to assess the effect of three antagonists targeting different monoamine pathways on amphetamine- and phencyclidine-induced locomotor hyperactivity. A total of 32 rats were pre-treated with antagonists affecting dopaminergic, noradrenergic and serotonergic transmission: haloperidol (0.05 mg/kg), prazosin (2 mg/kg) and ritanserin (1 mg/kg), respectively. After 30 min of spontaneous activity, rats were injected with amphetamine (0.5 mg/kg) or phencyclidine (2.5 mg/kg) and distance travelled, stereotypy and rearing recorded in photocell cages over 90 min. Pre-treatment with haloperidol or prazosin both reduced amphetamine-induced hyperactivity although pre-treatment with ritanserin had only a partial effect. None of the pre-treatments significantly altered the hyperlocomotion effects of phencyclidine. These findings suggest that noradrenergic as well as dopaminergic neurotransmission is critical for amphetamine-induced locomotor hyperactivity. Hyperlocomotion effects of phencyclidine are dependent on other factors, most likely NMDA receptor antagonism. These results help to interpret psychotomimetic drug-induced locomotor hyperactivity as an experimental model of psychosis.

Pharmacokinetics, Safety, and Tolerability of SHP465 Mixed Amphetamine Salts After Administration of Multiple Daily Doses in Children Aged 4-5 Years with Attention-Deficit/Hyperactivity Disorder.

BACKGROUND: Given the limited treatment options for younger children with attention-deficit/hyperactivity disorder (ADHD), a clinical study for SHP465 treatment was warranted. OBJECTIVES: We aimed to evaluate the pharmacokinetics, safety, and tolerability of SHP465 mixed amphetamine salts (MAS) 6.25 mg after multiple once-daily doses in children aged 4-5 years with ADHD. METHODS: In this open-label multicenter study, SHP465 MAS 6.25 mg once daily was administered for 28 days to children aged 4-5 years with ADHD; baseline ADHD Rating Scale-5 total score ≥ 28 (boys) or ≥ 24 (girls) and Clinical Global Impression-Severity scale score ≥ 4. Blood samples were collected in the pharmacokinetic-rich group predose on day 1 week 1 and day 7 week 4 (predose, postdose at 2, 5, 8, 12, 16, 24, and 48 hours); and in the pharmacokinetic-sparse group predose on day 1 weeks 1, 2, and 3 and 24 hours postdose on day 7 week 4 . Key pharmacokinetic parameters included maximum plasma drug concentration (Cmax), plasma trough drug concentration, time to Cmax during a dosing interval (tmax), area under the concentration-time curve from time 0 to time of last collected sample, area under the concentration-time curve over the dosing interval (24 h) at steady state (AUCtau,ss), first-order rate constant associated with the terminal phase of elimination, terminal half-life (t1/2), total clearance of drug from plasma after oral administration, and apparent volume of distribution at steady state. Safety endpoints included treatment-emergent adverse events and vital signs. RESULTS: Mean ± standard deviation age and body mass index of 24 participants (66.7% male) were 4.8 ± 0.41 years and 17.2 ± 3.18 kg/m2, respectively. The most common ADHD was the combined presentation (91.7%); ratings were 50% markedly ill and 45.8% moderately ill on the Clinical Global Impression-Severity scale. Plasma d-amphetamine and l-amphetamine steady state was attained by predose on treatment day 8, consistent with the half-life. Peak steady-state plasma concentration (median tmax) for both d-amphetamine and l-amphetamine occurred at 7.92 h postdose on day 7 week 4 and thereafter declined monoexponentially, with a geometric mean t1/2 of 10.4 and 12.3 h for d-amphetamine and l-amphetamine, respectively. For both d-amphetamine and l-amphetamine, Cmax and AUCtau,ss were comparable between children aged 4 years (n = 3) and children aged 5 years (n = 8) regardless of sex. In total, 14 treatment-emergent adverse events were reported by 45.8% (11/24) of participants. Five treatment-emergent adverse events, reported for four (16.7%) participants, were considered treatment related; affect lability occurred in two (8.3%) participants, and insomnia, accidental overdose, and increased blood pressure each occurred in one (4.2%) participant. CONCLUSIONS: In children aged 4-5 years with ADHD, following multiple once-daily administrations of SHP465 MAS 6.25 mg, the pharmacokinetic profile of plasma d-amphetamine and l-amphetamine was generally consistent among participants. Between-individual variability of plasma d-amphetamine and l-amphetamine steady-state exposure was low to moderate. SHP465 MAS was generally well tolerated in this study. TRIAL REGISTRATION: ClinicalTrials.gov, NCT03327402 (31 October, 2017).

Splice-Site Variants in the Gene Encoding GABA-A Receptor Delta Subunit Are Associated with Amphetamine Use in Patients under Methadone Maintenance Treatment.

Chronic opioid use disorder patients often also use other substances such as amphetamines. The gene-based analysis method was applied in the genomic database obtained from our previous study with 343 methadone maintenance treatment (MMT) patients. We found that the gene encoding gamma-aminobutyric acid type A receptors (GABA-A receptor) delta subunit isoforms (GABRD) was associated with amphetamine use in heroin dependent patients under MMT in Taiwan. A total of 15% of the 343 MMT patients tested positive for amphetamine in the urine toxicology test. Two genetic variants in the GABRD, rs2889475 and rs2376805, were found to be associated with the positive urine amphetamine test. They are located in the exon 1 of the splice variant and altered amino acid compositions (T126I, C/T, for rs2889475, and R252Q, G/A, for rs2376805). The CC genotype carriers of rs2889475 showed a four times higher risk of amphetamine use than those with TT genotype. The GG genotype carriers of rs2376805 showed a three times higher risk of amphetamine use than the AA genotype carriers. To our knowledge, this is the first report that demonstrated an association of the delta splice variant isoform in the GABA-A receptor with an increased risk of amphetamine use in MMT patients. Our results suggest that rs2889475 and rs2376805 may be indicators for the functional role and risk of amphetamine use in MMT patients.

Assessing Palatability of a New Amphetamine Extended-Release Tablet Formulation for the Treatment of ADHD.

INTRODUCTION/OBJECTIVE: ADHD is, for many people, a lifelong disease that requires chronic medication use. Stimulant therapy is often recommended as first-line treatment for ADHD. Adherence to stimulant treatment among patients diagnosed with ADHD is poor. Major regulatory agencies have recommended measurement of palatability for new tablet formulations. A new amphetamine extended-release tablet (AMPH ER TAB) for the treatment of attention-deficit/hyperactivity disorder (ADHD) was developed. The AMPH ER TAB has a bubblegum flavor and can be chewed or swallowed whole. In 2016, the FDA developed a draft guidance document on the topic of chewable drug tablet formulation palatability. METHODS: A palatability study of the AMPH ER TAB using the 2016 FDA guidance was conducted. Subjects were asked to assess the taste, aftertaste, and mouthfeel of the tablet formulation using a short questionnaire. Scores from the questionnaire were rated and presented. RESULTS: The substudy assessed 35 subjects with a mean age of 38 (±11) years. Subjects were predominantly male, non-Hispanic, and White. Most subjects rated the oral sensation/mouth feel and taste of the tablet as positive (pleasant to very pleasant) (70.1% and 83.6%, respectively). Additionally, 86.6% of the subjects rated the strength of the taste as neutral (moderate taste) or positive (mild to no taste). Finally, 82.1% of all subjects rated the aftertaste as positive (pleasant to very pleasant) and 92.5% of subjects rated the strength of the aftertaste as neutral or positive (mild to no taste). The trends in evaluation scores for each question were similar regardless of whether the ER chewable tablet was administered under fasted or fed conditions. CONCLUSION: The positive palatability data presented here will be useful for future "real-world" assessments of adherence to treatment with the AMPH ER TAB. Enhanced adherence may bolster the argument that taste, mouthfeel, and aftertaste are critical determinants of treatment adherence.

The Chronic Oral Administration of Clobenzorex or Amphetamine Decreases Motor Behavior and Induces Glial Activation in the Striatum Without Dopaminergic Degeneration.

Described as amphetamine-like due to their structural and stimulant similarities, clobenzorex is one of the five most-commonly used drugs in Mexico for the treatment of obesity. Various studies have shown that amphetamines induce dopaminergic neurotoxicity and neuroinflammation in the striatum, symptoms which are associated with motor damage. For this reason, the present study aimed to evaluate the effect of chronic clobenzorex administration on motor behaviors, TH immunoreactivity, gliosis, and the neurodegenerative process in the striatum and substantia nigra pars compacta (SNpc). The present research was conducted on three experimental groups of male Wistar rats: the vehicle group, the amphetamine group (2 mg/kg), and the clobenzorex group (30 mg/kg). All groups were subject to oral administration every 24 h for 31 days. Motor activity and motor coordination were evaluated in the open field test and the beam walking test, respectively. The animals were euthanized after the last day of treatment to enable the extraction of their brains for the evaluation of tyrosine hydroxylase (TH) levels, the immunoreactivity of the glial cells, and the neurodegeneration of both the striatum and SNpc via amino-cupric-silver stain. The results obtained show that amphetamine and clobenzorex administration decrease motor activity and motor coordination in the beam walking test and cause increased gliosis in the striatum, while no significant changes were observed in terms of immunoreactivity to TH and neurodegeneration in both the striatum and SNpc. These results suggest that the chronic administration of clobenzorex may decrease motor function in a manner similar to amphetamine, via the neuroadaptive and non-neurotoxic changes caused to the striatum under this administration scheme.

The Abuse Characteristics of Amphetamine-Type Stimulants in Patients Receiving Methadone Maintenance Treatment and Buprenorphine Maintenance Treatment.

OBJECTIVE: The purpose of this study was to retrospectively investigate the abuse characteristics of amphetamine-type stimulants (ATS) in patients receiving methadone maintenance treatment (MMT) and buprenorphine maintenance treatment (BMT). METHODS: A total of 58 MMT and 51 BMT patients abusing ATS were recruited from the drug maintenance treatment clinic of Ningbo Addiction Research and Treatment Center from January 2018 to December 2019. They were assessed using the amphetamine abuse questionnaire (AAQ), addiction severity index (ASI) and Barratt impulsiveness scale (BIS). Moreover, 40 MMT control patients, 40 BMT control patients and 20 healthy controls were also assessed using the BIS. All information was collected using the amphetamine abuse questionnaire (AAQ), Chinese version of addiction severity index (ASI-C) and Chinese version of Barratt impulsiveness scale (BIS-C) conducted by qualified psychologists. RESULTS: The interval of amphetamine use in the MMT group was shorter than the BMT group (P < 0.05). The drug use subscale score of ASI was higher in the MMT group than the BMT group (P < 0.05). The respective and total scores of attentional impulsiveness, motor impulsiveness and non-planning impulsiveness in BIS in the MMT group were all higher than the MMT control group (P < 0.05). The scores of motor impulsiveness and non-planning impulsiveness in the BMT group were higher than the BMT control group (P < 0.05). The respective and total scores in BIS in the MMT control group and the BMT control group were all higher than those in the healthy controls. CONCLUSION: The patients showing amphetamine abuse in maintenance therapy had a greater impulsiveness than those having other simple maintenance treatments, and patients under MMT may be more addicted to amphetamines in comparison with those having BMT.

Time-dependent changes in striatal monoamine levels and gene expression following single and repeated amphetamine administration in rats.

As drug addiction may result from pathological usurpations of learning and memory's neural mechanisms, we focused on the amphetamine-induced time-dependent neurochemical changes associated with neural plasticity. We used juvenile rats as the risk for drug abuse is higher during adolescence. Experiment 1 served to define the appropriate amphetamine dose and the neurochemical effects of a single administration. In experiment 2, rats received seven amphetamine or saline injections in the open-field test throughout a twelve-day period. We measured the mRNA levels of the brain-derived neurotrophic factor (BDNF), its tropomyosin receptor kinase B (TrkB), the cAMP response element-binding protein (CREB), the microRNA-132, the Rho GTPase-activating protein 32 (p250GAP), the corticotropin-releasing factor (CRF), and monoamines and amino-acids contents in the nucleus accumbens and the dorsal striatum 45, 90, and 180 min after the last injection. We found that amphetamine changed gene expression only at certain time points and in a dose and region-dependent manner. Repeated but not single administrations upregulated accumbal and striatal BDNF (180 min) and striatal pri-miR-132 (90 min) expression, while downregulated accumbal CREB levels (90 min). As only some drug users develop addiction, we compared brain parameters between low and high amphetamine responders. Prone subjects characterized by having reduced striatal 5-HT metabolism, higher accumbal BDNF and TrkB expression, and lower levels of CREB in the dorsal striatum and p250GAP in both regions. Thus, individual differences in drug-induced changes in neurotransmission and gene expression in nigrostriatal and mesolimbic dopaminergic pathways may underlie the plasticity adaptations associated with behavioral sensitization to amphetamine.

Brief history of the medical and non-medical use of amphetamine-like psychostimulants.

The alkaloid ephedrine derived from Ephedra vulgaris is at the origin of psychostimulant-drugs as amphetamine. These drugs have been principally utilized for medical treatments in the past, while their utilization has been largely reduced from the 1970s when the high risk of addiction and abuse has been recognized. The first reported treatments were as anti-asthmatics and to contrast narcolepsy until their recreational stimulant and anorexic effects were reported. Benzedrine and Pervitin use were of great importance during the Second World War due to their abundant utilization among military troops. Nowadays the use of selective amphetamine-like drugs is limited to ADHD treatment.

An efficient and label-free LC-MS/MS method for assessing drug's activity at dopamine and serotonin transporters using transporter-transfected HEK293T cells.

BACKGROUND: Dopamine transporter (DAT) and serotonin transporter (SERT) are targets for many psychoactive substances. Functional assays including uptake inhibition and release assays often involve radiolabeled compounds like [3H]-dopamine and [3H]-serotonin to assess drug activity at transporters, which have high requirements on handling radioactive samples. AIMS: The aim of this study was to establish a label-free method to assess drug activity at DAT and SERT. METHODS: A liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method was established using transporter-transfected human embryonic kidney 293T (HEK293T) cells. This method was evaluated by testing the effects of amphetamine and cocaine in the assay procedure. RESULTS: The limits of detection of this method were 0.2 nM for both dopamine (DA) and serotonin (5-HT), with good linearities in the range of 0.5-160 nM. Amphetamine and cocaine's IC50 and EC50 on DAT and SERT determined by this method were consistent with previous reports. CONCLUSIONS: A rapid, reliable and label-free LC-MS/MS method for assessing drug activity was established, which affords an attractive alternative for those laboratories that do not have a radiation license or capabilities.

Behavioral Battery for Testing Candidate Analgesics in Mice. I. Validation with Positive and Negative Controls.

This study evaluated a battery of pain-stimulated, pain-depressed, and pain-independent behaviors for preclinical pharmacological assessment of candidate analgesics in mice. Intraperitoneal injection of dilute lactic acid (IP acid) served as an acute visceral noxious stimulus to produce four pain-related behaviors in male and female ICR mice: stimulation of 1) stretching, 2) facial grimace, 3) depression of rearing, and 4) depression of nesting. Additionally, nesting and locomotion in the absence of the noxious stimulus were used to assess pain-independent drug effects. These six behaviors were used to compare effects of two mechanistically distinct but clinically effective positive controls (ketoprofen and oxycodone) and two negative controls that are not clinically approved as analgesics but produce either general motor depression (diazepam) or motor stimulation (amphetamine). We predicted that analgesics would alleviate all IP acid effects at doses that did not alter pain-independent behaviors, whereas negative controls would not. Consistent with this prediction, ketoprofen (0.1-32 mg/kg) produced the expected analgesic profile, whereas oxycodone (0.32-3.2 mg/kg) alleviated all IP acid effects except depression of rearing at doses lower than those that altered pain-independent behaviors. For the negative controls, diazepam (1-10 mg/kg) failed to block IP acid-induced depression of either rearing or nesting and only decreased IP acid-stimulated behaviors at doses that also decreased pain-independent behaviors. Amphetamine (0.32-3.2 mg/kg) alleviated all IP acid effects but only at doses that also stimulated locomotion. These results support utility of this model as a framework to evaluate candidate-analgesic effects in a battery of complementary pain-stimulated, pain-depressed, and pain-independent behavioral endpoints. SIGNIFICANCE STATEMENT: Preclinical assays of pain and analgesia often yield false-positive effects with candidate analgesics. This study used two positive-control analgesics (ketoprofen, oxycodone) and two active negative controls (diazepam, amphetamine) to validate a strategy for distinguishing analgesics from nonanalgesics by profiling drug effects in a battery of complementary pain-stimulated, pain-depressed, and pain-independent behaviors in male and female mice.

Pentadecapeptide BPC 157 counteracts L-NAME-induced catalepsy. BPC 157, L-NAME, L-arginine, NO-relation, in the suited rat acute and chronic models resembling 'positive-like' symptoms of schizophrenia.

In the suited rat-models, we focused on the stable pentadecapeptide BPC 157, L-NAME, NOS-inhibitor, and L-arginine, NOS-substrate, relation, the effect on schizophrenia-like symptoms. Medication (mg/kg intraperitoneally) was L-NAME (5), L-arginine (100), BPC 157 (0.01), given alone and/or together, at 5 min before the challenge for the acutely disturbed motor activity (dopamine-indirect/direct agonists (amphetamine (3.0), apomorphine (2.5)), NMDA-receptor non-competitive antagonist (MK-801 (0.2)), or catalepsy, (dopamine-receptor antagonist haloperidol (2.0)). Alternatively, BPC 157 10 µg/kg was given immediately after L-NAME 40 mg/kg intraperitoneally. To induce or prevent sensitization, we used chronic methamphetamine administration, alternating 3 days during the first 3 weeks, and challenge after next 4 weeks, and described medication (L-NAME, L-arginine, BPC 157) at 5 min before the methamphetamine at the second and third week. Given alone, BPC 157 or L-arginine counteracted the amphetamine-, apomorphine-, and MK-801-induced effect, haloperidol-induced catalepsy and chronic methamphetamine-induced sensitization. L-NAME did not affect the apomorphine-, and MK-801-induced effects, haloperidol-induced catalepsy and chronic methamphetamine-induced sensitization, but counteracted the acute amphetamine-induced effect. In combinations (L-NAME + L-arginine), as NO-specific counteraction, L-NAME counteracts L-arginine-induced counteractions in the apomorphine-, MK-801-, haloperidol- and methamphetamine-rats, but not in amphetamine-rats. Unlike L-arginine, BPC 157 maintains its counteracting effect in the presence of the NOS-blockade (L-NAME + BPC 157) or NO-system-over-stimulation (L-arginine + BPC 157). Illustrating the BPC 157-L-arginine relationships, BPC 157 restored the antagonization (L-NAME + L-arginine + BPC 157) when it had been abolished by the co-administration of L-NAME with L-arginine (L-NAME + L-arginine). Finally, BPC 157 directly inhibits the L-NAME high dose-induced catalepsy. Further studies would determine precise BPC 157/dopamine/glutamate/NO-system relationships and clinical application.

Suppressing effect of the novel positive allosteric modulator of the GABAB receptor, COR659, on locomotor hyperactivity induced by different drugs of abuse.

COR659 is a recently synthesized positive allosteric modulator (PAM) of the GABAB receptor. Similarly to all GABAB PAMs tested to date, COR659 has been reported to suppress different alcohol-related behaviors in rodents. The present study was designed to assess whether the anti-addictive properties of COR659 extend to drugs of abuse other than alcohol. Specifically, it investigated the effect of COR659 on cocaine-, amphetamine-, nicotine-, and morphine-induced locomotor hyperactivity in mice. To this aim, independent groups of CD1 mice were acutely pretreated with COR659 (0, 10, and 20 mg/kg; i.p.), then acutely treated with cocaine (0 and 10 mg/kg, s.c.), amphetamine (0 and 5 mg/kg; s.c.), nicotine (0 and 0.05 mg/kg; s.c.), or morphine (0 and 20 mg/kg; s.c.), and finally exposed for 60 min to a photocell-equipped motility cage. When given alone, both doses of COR659 were ineffective on spontaneous locomotor activity. Pretreatment with COR659 reduced, or even suppressed, the increase in motility counts induced by cocaine, amphetamine, nicotine, and morphine. Since locomotor hyperactivity is an attribute common to drugs of abuse, the results of the present study constitute the first line of evidence on the extension of the preclinical, anti-addictive profile of COR659 to cocaine, amphetamine, nicotine, and morphine.

Exercise craving potentiates excitatory inputs to ventral tegmental area dopaminergic neurons.

Physical exercise, which can be addictogenic on its own, is considered a therapeutic alternative for drug craving. Exercise might thus share with drugs the ability to strengthen excitatory synapses onto ventral tegmental area (VTA) dopaminergic neurones, as assessed by the ratio of AMPA receptor (AMPAR)-mediated excitatory postsynaptic currents (EPSCs) to NMDA receptor (NMDAR)-mediated EPSCs. As did acute cocaine, amphetamine, or Δ9 -tetrahydrocannabinol (THC) pretreatments, an acute 1-h wheel-running session increased the AMPAR/NMDAR ratio in VTA dopaminergic neurones. To dissect the respective influences of wheel-running seeking and performance, mice went through an operant protocol wherein wheel-running was conditioned by nose poking under fixed ratio schedules of reinforcement. Conditioned wheel-running increased the AMPAR/NMDAR ratio to a higher extent than free wheel-running, doing so although running performance was lower in the former paradigm than in the latter. Thus, the cue-reward association, rather than reward consumption, played a major role in this increase. The AMPAR/NMDAR ratio returned to baseline levels in mice that had extinguished the cued-running motivated task, but it increased after a cue-induced reinstatement session. The amplitude of this increase correlated with the intensity of exercise craving, as assessed by individual nose poke scores. Finally, cue-induced reinstatement of running seeking proved insensitive to acute cocaine or THC pretreatments. Our study reveals for the first time that the drive for exercise bears synaptic influences on VTA dopaminergic neurones which are reminiscent of drug actions. Whether these influences play a role in the therapeutic effects of exercise in human drug craving remains to be established.

Δ9-tetrahydrocannabinol: Drug discrimination abuse liability testing in female Lister Hooded rats: Trials, tribulations and triumphs.

INTRODUCTION: The assessment of the abuse potential of CNS-active drugs is a regulatory requirement. Drug discrimination is one of the nonclinical tests that contribute to this assessment by providing information on a drug's potential to induce a discriminative stimulus comparable to that of a known drug of abuse. AIM: The objective was to validate drug discrimination in the rat for the purpose of supporting regulatory submissions for novel drugs with potential cannabinoid-like activity. METHODS: Ten female Lister hooded rats were trained to discriminate no-drug from Δ9-THC (1.5 mg/kg, IP) under a FR10 schedule of reinforcement. Once trained, a Δ9-THC dose-response curve was obtained using doses of 0.25, 0.75, 1.5, and 3 mg/kg, IP. This was followed by evaluation of amphetamine (0.3 mg/kg, SC); morphine (3 mg/kg, IP); midazolam (2.5 mg/kg, PO); and the synthetic cannabinoids WIN55,212-2 (0.75 to 2 mg/kg, IP), CP-47,497 (0.5 to 2 mg/kg, IP), and JWH-018 (1 mg/kg, IP) for their discriminative stimulus similarity to Δ9-THC. RESULTS: Pharmacological specificity was demonstrated by achieving the anticipated dose-response curve for Δ9-THC, and a vehicle-like response for the non-cannabinoid drugs. Although full generalisation was obtained for JWH-018, in contrast to published literature, WIN55,212-2 and CP-47,497 failed to generalise to Δ9-THC. DISCUSSION: Based on the literature review performed in light of the results obtained, contrasting and unpredictable behavioural responses produced by cannabinoids in animals and humans raises the question of the reliability and relevance of including drug discrimination and self-administration studies within an abuse potential assessment for novel cannabinoid-like drugs.

Amphetamine reduces reward encoding and stabilizes neural dynamics in rat anterior cingulate cortex.

Psychostimulants such as d-amphetamine (AMPH) often have behavioral effects that appear paradoxical within the framework of optimal choice theory. AMPH typically increases task engagement and the effort animals exert for reward, despite decreasing reward valuation. We investigated neural correlates of this phenomenon in the anterior cingulate cortex (ACC), a brain structure implicated in signaling cost-benefit utility. AMPH decreased signaling of reward, but not effort, in the ACC of freely-moving rats. Ensembles of simultaneously recorded neurons generated task-specific trajectories of neural activity encoding past, present, and future events. Low-dose AMPH contracted these trajectories and reduced their variance, whereas high-dose AMPH expanded both. We propose that under low-dose AMPH, increased network stability balances moderately increased excitability, which promotes accelerated unfolding of a neural 'script' for task execution, despite reduced reward valuation. Noise from excessive excitability at high doses overcomes stability enhancement to drive frequent deviation from the script, impairing task execution.

Chronic risperidone administration leads to greater amphetamine-induced conditioned place preference.

Risperidone is an atypical antipsychotic drug used increasingly in children to manage symptoms of ADHD and conduct disorder. In rats, developmental risperidone administration is accompanied by increased locomotor activity during adulthood, as well as heightened sensitivity to the locomotor stimulating effects of amphetamine. This study compared sensitivity to the rewarding effects of amphetamine, as measured by conditioned place preference (CPP), between groups of rats administered chronic risperidone (3.0 mg/kg, s.c.) during development (postnatal days 14-42) or adulthood (postnatal days 77-105). Locomotor activity in a novel test cage and amphetamine-induced CPP were measured beginning three and four weeks, respectively, after the final risperidone injection. Female rats administered risperidone early in life were more active than any other group tested. Previous risperidone administration enhanced amphetamine CPP regardless of sex, and this effect appeared more prominent in the developmentally treated group. The density of forebrain dopamine transporters, a primary target of amphetamine, was also quantified in rats administered risperidone early in life and found to be reduced in the medial anterior, posterior, and ventral caudate nucleus. These results suggest that chronic risperidone treatment modifies later locomotor activity and sensitivity to the reinforcing effects of amphetamine, perhaps via a mechanism related to decreased forebrain dopamine transporter density.

Revealing Metabolic Perturbation Following Heavy Methamphetamine Abuse by Human Hair Metabolomics and Network Analysis.

Methamphetamine (MA) is a highly addictive central nervous system stimulant. Drug addiction is not a static condition but rather a chronically relapsing disorder. Hair is a valuable and stable specimen for chronic toxicological monitoring as it retains toxicants and metabolites. The primary focus of this study was to discover the metabolic effects encompassing diverse pathological symptoms of MA addiction. Therefore, metabolic alterations were investigated in human hair following heavy MA abuse using both targeted and untargeted mass spectrometry and through integrated network analysis. The statistical analyses (t-test, variable importance on projection score, and receiver-operator characteristic curve) demonstrated that 32 metabolites (in targeted metabolomics) as well as 417 and 224 ion features (in positive and negative ionization modes of untargeted metabolomics, respectively) were critically dysregulated. The network analysis showed that the biosynthesis or metabolism of lipids, such as glycosphingolipids, sphingolipids, glycerophospholipids, and ether lipids, as well as the metabolism of amino acids (glycine, serine and threonine; cysteine and methionine) is affected by heavy MA abuse. These findings reveal crucial metabolic effects caused by MA addiction, with emphasis on the value of human hair as a diagnostic specimen for determining drug addiction, and will aid in identifying robust diagnostic markers and therapeutic targets.