A Modified Delphi Consensus Study of the Screening, Diagnosis, and Treatment of Tardive Dyskinesia.

OBJECTIVE: A nominal group process followed by a modified Delphi method was used to survey expert opinions on best practices for tardive dyskinesia (TD) screening, diagnosis, and treatment and to identify areas lacking in clinical evidence. PARTICIPANTS: A steering committee of 11 TD experts met in nominal group format to prioritize questions to be addressed and identify core bibliographic materials and criteria for survey panelists. Of 60 invited experts, 29 (23 psychiatrists and 6 neurologists) agreed to participate. EVIDENCE: A targeted literature search of PubMed (search term: tardive dyskinesia) and recommendations of the steering committee were used to generate core bibliographic material. Inclusion criteria were as follows: (1) review articles, meta-analyses, guidelines, or clinical trials; (2) publication in English between 2007 and 2017; (3) > 3 pages in length; and (4) publication in key clinical journals with impact factors ≥ 2.0. Of 29 references that met these criteria, 18 achieved a score ≥ 5 (calculated as the number of steering committee votes multiplied by journal impact factor and number of citations divided by years since publication) and were included. CONSENSUS PROCESS: Two survey rounds were conducted anonymously through electronic media from November 2017 to January 2018; responses were collected, collated, and analyzed. Respondent agreement was defined a priori as unanimous (100%), consensus (75%-99%), or majority (50%-74%). For questions using a 5-point Likert scale, agreement was based on percentage of respondents choosing ≥ 4 ("agree completely" or "agree"). Round 1 survey included questions on TD screening, diagnosis, and treatment. Round 2 questions were refined per panelist feedback and excluded Round 1 questions with < 25% agreement and > 75% agreement (unless feedback suggested further investigation). CONCLUSIONS: Consensus was reached that (1) a brief, clinical assessment for TD should be performed at every clinical encounter in patients taking antipsychotics; (2) even mild movements in 1 body area may represent possible TD; (3) management requires an overall evaluation of treatment, including reassessment of antipsychotics and anticholinergics as well as consideration of vesicular monoamine transporter 2 (VMAT2) inhibitors; and (4) informed discussions with patients/caregivers are essential.

Prolonging the Reduction of Nicotine Self-Administration in Rats by Coadministering Chronic Nicotine With Amitifadine, a Triple Monoamine Reuptake Inhibitor With CYP2B6 Inhibitory Actions.

INTRODUCTION: Existing treatments can aid tobacco smoking cessation, but they have low efficacy. Because there is a network of neural systems involved in tobacco addiction, combination treatments may provide greater efficacy. Chronic nicotine and amitifadine have each been shown to significantly reduce nicotine self-administration in rats. This study was conducted to determine if the combination of chronic nicotine with amitifadine, a triple monoamine reuptake inhibitor with CYP2B inhibitory effects, would reduce nicotine self-administration to a greater extent than either alone or placebo. METHODS: This study tested the combination of nicotine plus amitifadine in young adult female Sprague-Dawley rats self-administering nicotine (0.03 mg/kg/infusion). This combination was compared with each treatment alone and the vehicle during continuing nicotine self-administration as well as during resumption of self-administration after a week of enforced abstinence, modeling a quit attempt. Finally, we studied the residual effects of these therapies after discontinuation of treatment. RESULTS: Treatment with either chronic nicotine or amitifadine alone significantly reduced nicotine self-administration relative to controls. The combination of the treatments significantly enhanced this effect. After treatment withdrawal, all of the groups showed increases in nicotine self-administration, but only the combined treatment group remained significantly below control rates of nicotine self-administration. CONCLUSIONS: This study showed the promise of amitifadine as a possible new treatment for smoking cessation and suggested that amitifadine is more effective when given with chronic nicotine. The improved efficacy of the amitifadine and nicotine combination may be potentiated by amitifadine's inhibitory effects on CYP2B, which slows nicotine metabolism. IMPLICATIONS: This study replicated the effects that chronic nicotine or chronic amitifadine, a triple reuptake inhibitor, significantly reduces nicotine self-administration in rats. It extends those findings by showing that the combination of chronic nicotine plus amitifadine causes significantly greater reduction in nicotine self-administration than either drug treatment alone. The combination of chronic amitifadine and chronic nicotine also causes a persistent significant reduction in nicotine self-administration after the end of treatment. The amitifadine and nicotine treatment should be assessed in humans to determine whether this combination provides greater efficacy in smoking cessation than transdermal nicotine treatment alone.

The psychostimulant (±)-cis-4,4'-dimethylaminorex (4,4'-DMAR) interacts with human plasmalemmal and vesicular monoamine transporters.

(±)-cis-4,4'-Dimethylaminorex (4,4'-DMAR) is a new psychoactive substance (NPS) that has been associated with 31 fatalities and other adverse events in Europe between June 2013 and February 2014. We used in vitro uptake inhibition and transporter release assays to determine the effects of 4,4'-DMAR on human high-affinity transporters for dopamine (DAT), norepinephrine (NET) and serotonin (SERT). In addition, we assessed its binding affinities to monoamine receptors and transporters. Furthermore, we investigated the interaction of 4,4'-DMAR with the vesicular monoamine transporter 2 (VMAT2) in rat phaeochromocytoma (PC12) cells and synaptic vesicles prepared from human striatum. 4,4'-DMAR inhibited uptake mediated by human DAT, NET or SERT, respectively in the low micromolar range (IC50 values < 2 µM). Release assays identified 4,4'-DMAR as a substrate type releaser, capable of inducing transporter-mediated reverse transport via DAT, NET and SERT. Furthermore, 4,4'-DMAR inhibited both the rat and human isoforms of VMAT2 at a potency similar to 3,4-methylenedioxymethylamphetamine (MDMA). This study identified 4,4'-DMAR as a potent non-selective monoamine releasing agent. In contrast to the known effects of aminorex and 4-methylaminorex, 4,4'-DMAR exerts profound effects on human SERT. The latter finding is consistent with the idea that fatalities associated with its abuse may be linked to monoaminergic toxicity including serotonin syndrome. The activity at VMAT2 suggests that chronic abuse of 4,4'-DMAR may result in long-term neurotoxicity.

New Scaffold for Lead Compounds to Treat Methamphetamine Use Disorders.

Despite increased methamphetamine use worldwide, pharmacotherapies are not available to treat methamphetamine use disorder. The vesicular monoamine transporter-2 (VMAT2) is an important pharmacological target for discovery of treatments for methamphetamine use disorder. VMAT2 inhibition by the natural product, lobeline, reduced methamphetamine-evoked dopamine release, methamphetamine-induced hyperlocomotion, and methamphetamine self-administration in rats. Compared to lobeline, lobelane exhibited improved affinity and selectivity for VMAT2 over nicotinic acetylcholine receptors. Lobelane inhibited neurochemical and behavioral effects of methamphetamine, but tolerance developed to its behavioral efficacy in reducing methamphetamine self-administration, preventing further development. The lobelane analog, R-N-(1,2-dihydroxypropyl)-2,6-cis-di-(4-methoxyphenethyl)piperidine hydrochloride (GZ-793A), potently and selectively inhibited VMAT2 function and reduced neurochemical and behavioral effects of methamphetamine. However, GZ-793A exhibited potential to induce ventricular arrhythmias interacting with human-ether-a-go-go (hERG) channels. Herein, a new lead, R-3-(4-methoxyphenyl)-N-(1-phenylpropan-2-yl)propan-1-amine (GZ-11610), from the novel scaffold (N-alkyl(1-methyl-2-phenylethyl)amine) was evaluated as a VMAT2 inhibitor and potential therapeutic for methamphetamine use disorder. GZ-11610 was 290-fold selective for VMAT2 over dopamine transporters, suggesting that it may lack abuse liability. GZ-11610 was 640- to 3500-fold selective for VMAT2 over serotonin transporters and nicotinic acetylcholine receptors. GZ-11610 exhibited > 1000-fold selectivity for VMAT2 over hERG, representing a robust improvement relative to our previous VMAT2 inhibitors. GZ-11610 (3-30 mg/kg, s.c. or 56-300 mg/kg, oral) reduced methamphetamine-induced hyperactivity in methamphetamine-sensitized rats. Thus, GZ-11610 is a potent and selective inhibitor of VMAT2, may have low abuse liability and low cardiotoxicity, and after oral administration is effective and specific in inhibiting the locomotor stimulant effects of methamphetamine, suggesting further investigation as a potential therapeutic for methamphetamine use disorder.

Dopamine depletion shifts behavior from activity based reinforcers to more sedentary ones and adenosine receptor antagonism reverses that shift: Relation to ventral striatum DARPP32 phosphorylation patterns.

The mesolimbic dopamine (DA) system plays a critical role in behavioral activation and effort-based decision-making. DA depletion produces anergia (shifts to low effort options) in animals tested on effort-based decision-making tasks. Caffeine, the most consumed stimulant in the world, acts as an adenosine A1/A2A receptor antagonist, and in striatal areas DA D1 and D2 receptors are co-localized with adenosine A1 and A2A receptors respectively. In the present work, we evaluated the effect of caffeine on anergia induced by the VMAT-2 inhibitor tetrabenazine (TBZ), which depletes DA. Anergia was evaluated in a three-chamber T-maze task in which animals can chose between running on a wheel (RW) vs. sedentary activities such as consuming sucrose or sniffing a neutral odor. TBZ-caffeine interactions in ventral striatum were evaluated using DARPP-32 phosphorylation patterns as an intracellular marker of DA-adenosine receptor interaction. In the T-maze, control mice spent more time running and much less consuming sucrose or sniffing. TBZ (4.0 mg/kg) reduced ventral striatal DA tissue levels as measured by HPLC, and also shifted preferences in the T-maze, reducing selection of the reinforcer that involved vigorous activity (RW), but increasing consumption of a reinforcer that required little effort (sucrose), at doses that had no effect on independent measures of appetite or locomotion in a RW. Caffeine at doses that had no effect on their own reversed the effects of TBZ on T-maze performance, and also suppressed TBZ-induced pDARPP-32(Thr34) expression as measured by western blot, suggesting a role for D2-A2A interactions. These results support the idea that DA depletion produces anergia, but does not affect the primary motivational effects of sucrose. Caffeine, possibly by acting on A2A receptors in ventral striatum, reversed the DA depletion effects. It is possible that caffeine, like selective adenosine A2A antagonists, could have some therapeutic benefit for treating effort-related symptoms.

Selective accumulation of biotin in arterial chemoreceptors: requirement for carotid body exocytotic dopamine secretion.

KEY POINTS: Biotin, a vitamin whose main role is as a coenzyme for carboxylases, accumulates at unusually large amounts within cells of the carotid body (CB). In biotin-deficient rats biotin rapidly disappears from the blood; however, it remains at relatively high levels in CB glomus cells. The CB contains high levels of mRNA for SLC5a6, a biotin transporter, and SLC19a3, a thiamine transporter regulated by biotin. Animals with biotin deficiency exhibit pronounced metabolic lactic acidosis. Remarkably, glomus cells from these animals have normal electrical and neurochemical properties. However, they show a marked decrease in the size of quantal dopaminergic secretory events. Inhibitors of the vesicular monoamine transporter 2 (VMAT2) mimic the effect of biotin deficiency. In biotin-deficient animals, VMAT2 protein expression decreases in parallel with biotin depletion in CB cells. These data suggest that dopamine transport and/or storage in small secretory granules in glomus cells depend on biotin. ABSTRACT: Biotin is a water-soluble vitamin required for the function of carboxylases as well as for the regulation of gene expression. Here, we report that biotin accumulates in unusually large amounts in cells of arterial chemoreceptors, carotid body (CB) and adrenal medulla (AM). We show in a biotin-deficient rat model that the vitamin rapidly disappears from the blood and other tissues (including the AM), while remaining at relatively high levels in the CB. We have also observed that, in comparison with other peripheral neural tissues, CB cells contain high levels of SLC5a6, a biotin transporter, and SLC19a3, a thiamine transporter regulated by biotin. Biotin-deficient rats show a syndrome characterized by marked weight loss, metabolic lactic acidosis, aciduria and accelerated breathing with normal responsiveness to hypoxia. Remarkably, CB cells from biotin-deficient animals have normal electrophysiological and neurochemical (ATP levels and catecholamine synthesis) properties; however, they exhibit a marked decrease in the size of quantal catecholaminergic secretory events, which is not seen in AM cells. A similar differential secretory dysfunction is observed in CB cells treated with tetrabenazine, a selective inhibitor of the vesicular monoamine transporter 2 (VMAT2). VMAT2 is highly expressed in glomus cells (in comparison with VMAT1), and in biotin-deficient animals VMAT2 protein expression decreases in parallel with the decrease of biotin accumulated in CB cells. These data suggest that biotin has an essential role in the homeostasis of dopaminergic transmission modulating the transport and/or storage of transmitters within small secretory granules in glomus cells.

Not All Antidepressants Are Created Equal: Differential Effects of Monoamine Uptake Inhibitors on Effort-Related Choice Behavior.

Motivated behavior can be characterized by behavioral activation and high work output. Moreover, people with depression and other disorders show effort-related motivational symptoms, such as anergia, psychomotor retardation, and fatigue. Effort-based decision making is studied using tasks offering choices between high effort options leading to highly valued reinforcers vs low effort/low reward options, and such tasks could be useful as animal models of motivational symptoms. In the present studies the effort-related effects of the vesicular monoamine transport (VMAT-2) inhibitor tetrabenazine (TBZ) were investigated. TBZ blocks vesicular storage and also produces depressive symptoms in humans. Moreover, TBZ alters effort-based choice in rats, biasing animals toward low effort alternatives. The present studies investigated the ability of acute administration of various monoamine uptake inhibitors to reverse the effects of TBZ. Effort-related effects of TBZ were attenuated by the catecholamine uptake inhibitor and antidepressant bupropion, and this effect of bupropion was reversed by either D1 or D2 family antagonism. The effort-related effects of TBZ were also attenuated by the selective dopamine uptake blocker GBR12909. The 5-HT uptake inhibitor fluoxetine and the norepinephrine uptake inhibitor desipramine failed to reverse the effects of TBZ, and higher doses of these drugs, given alone or in combination with TBZ, led to further behavioral impairments. These results indicate that drugs acting on dopamine transmission are relatively effective at reversing the effort-related effects of TBZ, and are consistent with the hypothesis that drugs that enhance dopamine transmission may be effective at treating effort-related psychiatric symptoms in humans.

Reengineered tricyclic anti-cancer agents.

The phenothiazine and dibenzazepine tricyclics are potent neurotropic drugs with a documented but underutilized anti-cancer side effect. Reengineering these agents (TFP, CPZ, CIP) by replacing the basic amine with a neutral polar functional group (e.g., RTC-1, RTC-2) abrogated their CNS effects as demonstrated by in vitro pharmacological assays and in vivo behavioral models. Further optimization generated several phenothiazines and dibenzazepines with improved anti-cancer potency, exemplified by RTC-5. This new lead demonstrated efficacy against a xenograft model of an EGFR driven cancer without the neurotropic effects exhibited by the parent molecules. Its effects were attributed to concomitant negative regulation of PI3K-AKT and RAS-ERK signaling.

A New VMAT-2 Inhibitor NBI-641449 in the Treatment of Huntington Disease.

AIMS: To evaluate the effectiveness of a new VMAT-2 inhibitor NBI-641449 in controlling hyperkinetic movements of Huntington disease (HD) and to investigate its possible therapeutic effects. METHODS: We applied three different doses of NBI-641449 (1, 10, 100 mg/kg/day) for 2 weeks in 4-month-old YAC128 mice and wild-type (WT) mice. Rotarod performance and locomotive activities were tested during the administration of the drug. The concentration of dopamine (DA) and its metabolites was quantified in the striatal tissues by high-performance liquid chromatography (HPLC). Neuron survival in striatum and huntingtin protein aggregates were assessed with immunostaining. Expression levels of endoplasmic reticulum (ER) stress proteins were detected by immunoblotting. RESULTS: Rotarod performance was significantly improved after treatment with low or middle dose of NBI-641449 in YAC128 mice. Open field test showed that NBI-641449 treatment could attenuate the increased horizontal activity (HACTV), total vertical movement, moving time, and moving distance in YAC128 mice. High dose of NBI-641449 might cause sedative effects in WT and YAC128 mice. HPLC showed that NBI-641449 caused a dose-dependent decrease of DA, 3,4-dihydroxyphenylacetic acid, and homovanillic acid levels in the striatum. NeuN and DARPP-32 immunostaining revealed that NBI-641449 had no significant effect on the neuron survival in the striatum. However, NBI-641449 treatment reduced the huntingtin protein aggregates in the cortex of YAC128 mice. In addition, the levels of ER stress proteins were increased in YAC128 mice, which can be suppressed by NBI-641449. CONCLUSIONS: These findings suggest that this new VMAT-2 inhibitor NBI-641449 may have therapeutic potential for the treatment of HD.

The VMAT-2 inhibitor tetrabenazine alters effort-related decision making as measured by the T-maze barrier choice task: reversal with the adenosine A2A antagonist MSX-3 and the catecholamine uptake blocker bupropion.

RATIONALE: Depressed people show effort-related motivational symptoms, such as anergia, retardation, lassitude, and fatigue. Animal tests can model these motivational symptoms, and the present studies characterized the effort-related effects of the vesicular monoamine transport (VMAT-2) inhibitor tetrabenazine. Tetrabenazine produces depressive symptoms in humans and, at low doses, preferentially depletes dopamine. OBJECTIVES: The current studies investigated the effects of tetrabenazine on effort-based decision making using the T-maze barrier task. METHODS: Rats were tested in a T-maze in which the choice arms of the maze contain different reinforcement densities, and under some conditions, a vertical barrier was placed in the high-density arm to provide an effort-related challenge. The first experiment assessed the effects of tetrabenazine under different maze conditions: a barrier in the arm with 4 food pellets and 2 pellets in the no barrier arm (4-2 barrier), 4 pellets in one arm and 2 pellets in the other with no barrier in either arm (no barrier), and 4 pellets in the barrier arm with no pellets in the other (4-0 barrier). RESULTS: Tetrabenazine (0.25-0.75 mg/kg IP) decreased selection of the high cost/high reward arm when the barrier was present, but had no effect on choice under the no barrier and 4-0 barrier conditions. The effects of tetrabenazine on barrier climbing in the 4-2 condition were reversed by the adenosine A2A antagonist MSX-3 and the catecholamine uptake inhibitor and antidepressant bupropion. CONCLUSIONS: These studies have implications for the development of animal models of the motivational symptoms of depression and other disorders.

The VMAT-2 inhibitor tetrabenazine affects effort-related decision making in a progressive ratio/chow feeding choice task: reversal with antidepressant drugs.

Behavioral activation is a fundamental feature of motivation, and organisms frequently make effort-related decisions based upon evaluations of reinforcement value and response costs. Furthermore, people with major depression and other disorders often show anergia, psychomotor retardation, fatigue, and alterations in effort-related decision making. Tasks measuring effort-based decision making can be used as animal models of the motivational symptoms of depression, and the present studies characterized the effort-related effects of the vesicular monoamine transport (VMAT-2) inhibitor tetrabenazine. Tetrabenazine induces depressive symptoms in humans, and also preferentially depletes dopamine (DA). Rats were assessed using a concurrent progressive ratio (PROG)/chow feeding task, in which they can either lever press on a PROG schedule for preferred high-carbohydrate food, or approach and consume a less-preferred lab chow that is freely available in the chamber. Previous work has shown that the DA antagonist haloperidol reduced PROG work output on this task, but did not reduce chow intake, effects that differed substantially from those of reinforcer devaluation or appetite suppressant drugs. The present work demonstrated that tetrabenazine produced an effort-related shift in responding on the PROG/chow procedure, reducing lever presses, highest ratio achieved and time spent responding, but not reducing chow intake. Similar effects were produced by administration of the subtype selective DA antagonists ecopipam (D1) and eticlopride (D2), but not by the cannabinoid CB1 receptor neutral antagonist and putative appetite suppressant AM 4413, which suppressed both lever pressing and chow intake. The adenosine A2A antagonist MSX-3, the antidepressant and catecholamine uptake inhibitor bupropion, and the MAO-B inhibitor deprenyl, all reversed the impairments induced by tetrabenazine. This work demonstrates the potential utility of the PROG/chow procedure as a rodent model of the effort-related deficits observed in depressed patients.

VMAT2 identified as a regulator of late-stage ß-cell differentiation.

Cell replacement therapy for diabetes mellitus requires cost-effective generation of high-quality, insulin-producing, pancreatic ß cells from pluripotent stem cells. Development of this technique has been hampered by a lack of knowledge of the molecular mechanisms underlying ß-cell differentiation. The present study identified reserpine and tetrabenazine (TBZ), both vesicular monoamine transporter 2 (VMAT2) inhibitors, as promoters of late-stage differentiation of Pdx1-positive pancreatic progenitor cells into Neurog3 (referred to henceforth as Ngn3)-positive endocrine precursors. VMAT2-controlled monoamines, such as dopamine, histamine and serotonin, negatively regulated ß-cell differentiation. Reserpine or TBZ acted additively with dibutyryl adenosine 3',5'-cyclic AMP, a cell-permeable cAMP analog, to potentiate differentiation of embryonic stem (ES) cells into ß cells that exhibited glucose-stimulated insulin secretion. When ES cell-derived ß cells were transplanted into AKITA diabetic mice, the cells reversed hyperglycemia. Our protocol provides a basis for the understanding of ß-cell differentiation and its application to a cost-effective production of functional ß cells for cell therapy.

Effort-related motivational effects of the VMAT-2 inhibitor tetrabenazine: implications for animal models of the motivational symptoms of depression.

Motivated behaviors are often characterized by a high degree of behavioral activation, and work output and organisms frequently make effort-related decisions based upon cost/benefit analyses. Moreover, people with major depression and other disorders often show effort-related motivational symptoms such as anergia, psychomotor retardation, and fatigue. It has been suggested that tasks measuring effort-related choice behavior could be used as animal models of the motivational symptoms of depression, and the present studies characterized the effort-related effects of the vesicular monoamine transport (VMAT) inhibitor tetrabenazine. Tetrabenazine produces depressive symptoms in humans and, because of its selective inhibition of VMAT-2, it preferentially depletes dopamine (DA). Rats were assessed using a concurrent fixed-ratio 5/chow feeding choice task that is known to be sensitive to dopaminergic manipulations. Tetrabenazine shifted response choice in rats, producing a dose-related decrease in lever pressing and a concomitant increase in chow intake. However, it did not alter food intake or preference in parallel free-feeding choice studies. The effects of tetrabenazine on effort-related choice were reversed by the adenosine A2A antagonist MSX-3 and the antidepressant bupropion. A behaviorally active dose of tetrabenazine decreased extracellular DA in nucleus accumbens and increased expression of DARPP-32 in accumbens medium spiny neurons in a pattern indicative of reduced transmission at both D1 and D2 DA receptors. These experiments demonstrate that tetrabenazine, which is used in animal models to produce depression-like effects, can alter effort-related choice behavior. These studies have implications for the development of animal models of the motivational symptoms of depression and related disorders.

The vesicular monoamine transporter (VMAT-2) inhibitor tetrabenazine induces tremulous jaw movements in rodents: implications for pharmacological models of parkinsonian tremor.

Tetrabenazine (TBZ) is a reversible inhibitor of vesicular monoamine storage that is used to treat Huntington's disease. TBZ preferentially depletes striatal dopamine (DA), and patients being treated with TBZ often experience parkinsonian side effects. The present studies were conducted to investigate the ability of TBZ to induce tremulous jaw movements (TJMs), which are a rodent model of parkinsonian tremor, and to determine if interference with adenosine A2A receptor transmission can attenuate TJMs and other motor effects of TBZ. In rats, TBZ (0.25-2.0mg/kg) significantly induced TJMs, which primarily occurred in the 3.0-7.5-Hz frequency range. The adenosine A2A antagonist MSX-3 (1.25-10.0mg/kg) significantly attenuated the TJMs induced by 2.0mg/kg TBZ in rats, and also significantly reduced the display of catalepsy and locomotor suppression induced by TBZ. In mice, TBZ (2.5-10.0mg/kg) dose dependently induced TJMs, and adenosine A2A receptor knockout mice showed significantly fewer TJMs compared to wild-type controls. MSX-3 (2.5-10.0mg/kg) also significantly reduced TBZ-induced TJMs in CD1 mice. To provide a cellular marker of these pharmacological conditions, we examined c-Fos expression in the ventrolateral neostriatum (VLS). TBZ (2.0mg/kg) significantly increased the number of c-Fos-positive cells in the VLS, which is indicative of reduced DA D2 receptor transmission, and 10.0mg/kg MSX-3 significantly attenuated the TBZ-induced c-Fos expression. These results indicate that TBZ induces tremor as measured by the TJM model, and that pharmacological antagonism and genetic deletion of adenosine A2A receptors are capable of attenuating this oral tremor.

Tetrabenazine inhibition of monoamine uptake and methamphetamine behavioral effects: locomotor activity, drug discrimination and self-administration.

Tetrabenazine (TBZ), a benzoquinolizine derivative, binds with high affinity to the vesicular monoamine transporter-2 (VMAT2), inhibiting uptake of cytosolic monoamines. The current study aimed to provide preclinical evidence supporting the potential use of TBZ as a treatment for methamphetamine abuse. Effects of TBZ on function of the dopamine transporter (DAT) and serotonin transporter (SERT) in striatal and hippocampal synaptosomes, respectively, and on VMAT2 function in isolated striatal synaptic vesicles were determined. Effect of TBZ (acute, 0.1-3.0 mg/kg, s.c.; repeated, 1.0 mg/kg for 7 days) on locomotor activity in methamphetamine-sensitized rats was assessed. Ability of TBZ (0.1-3.0 mg/kg; s.c.) or vehicle to decrease the discriminative effect of methamphetamine also was determined. Ability of TBZ (acute, 0.1-1.0 mg/kg, s.c.; repeated, 0.1 or 1.0 mg/kg for 7 days) to specifically decrease methamphetamine self-administration was determined; for comparison, a separate group of rats was assessed for effects of TBZ on food-maintained responding. Results show that TBZ was 11-fold more potent inhibiting DAT than SERT, and 2.5-fold more potent inhibiting VMAT2 than DAT. Results from behavioral studies showed that the lowest dose of TBZ transiently increased methamphetamine self-administration, whereas higher TBZ doses decreased methamphetamine self-administration. Also, TBZ at high doses decreased methamphetamine locomotor sensitization and discriminative stimulus effects, as well as food-maintained responding. Thus, despite acting as a potent VMAT2 inhibitor, these preclinical results indicate that TBZ lacks behavioral specificity as an inhibitor of methamphetamine-induced reinforcement, diminishing its viability as a suitable treatment for methamphetamine abuse.

Monoamine carboxylate transporters are involved in BI-1-associated cancer metastasis in HT1080 colon fibrosarcoma cells.

The overexpression of BI-1 induces an acidic extracellular pH due to alterations of mitochondrial function, leading to cancer metastasis through anaerobic glucose metabolism. In this study, ion transporters such as sodium hydrogen exchangers (NHE) and monoamine carboxylate transporters (MCTs) were studied in BI-1-overexpressing HT1080 cells (BI-1 cells). The extracellular pH became acidic as culture time of BI-1 cells increased, while intracellular pH stayed relatively stable at pH 7.2. The expression of MCTs increased in BI-1 cells as culture time passed. 5-(N-ethyl-N-isopropyl) amiloride or dimethylamiloride, NHE inhibitor, abrogated the elevated MCT expression, indicating that MCT followed NHE activation. An MCT inhibitor, lonidamine, regulated the acidification of extracellular pH, also inhibiting both increased cancer cell migration and infiltration and MMP2/9 activity. The inhibition of either NHE or MCT affected the intracellular pH, leading to a severely acidic intracellular pH and cell death. In BI-1 cells, the activation of ion transporters such as NHE or MCT may offer a survival strategy against metabolism-associated acidic stresses. These findings suggest that BI-1 can lead cancer invasion and metastasis by inducing extracellular environment acidic.

The novel pyrrolidine nor-lobelane analog UKCP-110 [cis-2,5-di-(2-phenethyl)-pyrrolidine hydrochloride] inhibits VMAT2 function, methamphetamine-evoked dopamine release, and methamphetamine self-administration in rats.

Both lobeline and lobelane attenuate methamphetamine self-administration in rats by decreasing methamphetamine-induced dopamine release via interaction with vesicular monoamine transporter-2 (VMAT2). A novel derivative of nor-lobelane, cis-2,5-di-(2-phenethyl)-pyrrolidine hydrochloride (UKCP-110), and its trans-isomers, (2R,5R)-trans-di-(2-phenethyl)-pyrrolidine hydrochloride (UKCP-111) and (2S,5S)-trans-di-(2-phenethyl)-pyrrolidine hydrochloride (UKCP-112), were evaluated for inhibition of [(3)H]dihydrotetrabenazine binding and [(3)H]dopamine uptake by using a rat synaptic vesicle preparation to assess VMAT2 interaction. Compounds were evaluated for inhibition of [(3)H]nicotine and [(3)H]methyllycaconitine binding to assess interaction with the major nicotinic receptor subtypes. In addition, compounds were evaluated for inhibition of methamphetamine-evoked endogenous dopamine release by using striatal slices. The most promising compound, UKCP-110, was evaluated for its ability to decrease methamphetamine self-administration and methamphetamine discriminative stimulus cues and for its effect on food-maintained operant responding. UKCP-110, UKCP-111, and UKCP-112 inhibited [(3)H]dihydrotetrabenazine binding (K(i) = 2.66 ± 0.37, 1.05 ± 0.10, and 3.80 ± 0.31 µM, respectively) and had high potency inhibiting [(3)H]dopamine uptake (K(i) = 0.028 ± 0.001, 0.046 ± 0.008, 0.043 ± 0.004 µM, respectively), but lacked affinity at nicotinic receptors. Although the trans-isomers did not alter methamphetamine-evoked dopamine release, UKCP-110 inhibited (IC(50) = 1.8 ± 0.2 µM; I(max) = 67.18 ± 6.11 µM) methamphetamine-evoked dopamine release. At high concentrations, UKCP-110 also increased extracellular dihydroxyphenylacetic acid. It is noteworthy that UKCP-110 decreased the number of methamphetamine self-infusions, while having no effect on food-reinforced behavior or the methamphetamine stimulus cue. Thus, UKCP-110 represents a new lead in the development of novel pharmacotherapies for the treatment of methamphetamine abuse.

Tetrabenazine, a monoamine-depleting drug used in the treatment of hyperkinetic movement disorders.

BACKGROUND: Few drugs are available for the management of hyperkinetic movement disorders such as the dystonias, choreas, dyskinesias, and tics. Those that are available (primarily neuroleptics) are associated with a wide range of potentially serious adverse effects, including induction of tardive movement disorders. Tetrabenazine (TBZ) is a monoamine-depleting agent initially studied in the 1950s and currently approved by the US Food and Drug Administration for the treatment of chorea in Huntington's disease. OBJECTIVE: This article reviews the chemistry, pharmacology, pharmacokinetics, therapeutic use, tolerability, drug-interaction potential, and dosing and administration of TBZ. METHODS: MEDLINE was searched (1950-February 2010) for English-language articles investigating any aspect of TBZ. Search terms included tetrabenazine, Ro 1-9569, Nitoman, benzoquinolizines, and reserpine. The reference lists of the identified articles were searched for other pertinent publications, particularly those that were not indexed in the 1950s and 1960s. RESULTS: In the search for a chemical compound that was simpler than reserpine while preserving reserpine-like psychotropic activity, TBZ was identified in the 1950s as one member of a large group of benzoquinolizine derivatives. TBZ acts by depletion of the monoamines serotonin, norepinephrine, and dopamine in the central nervous system (CNS). It does this by reversibly inhibiting vesicle monoamine transporter type 2 and thus preventing monoamine uptake into presynaptic neurons. Clinical studies suggest that TBZ may have therapeutic applications in a wide range of hyperkinetic movement disorders. TBZ has been associated with numerous adverse effects, some of them serious and potentially fatal; these include parkinsonism, other extrapyramidal symptoms (particularly akathisia), depression and suicidality, neuroleptic malignant syndrome, and sedation. TBZ is subject to important drug-drug interactions with inhibitors and inducers of cytochrome P450 (CYP) 2D6, reserpine, and lithium. It is one of very few drugs whose dosing is based, in part, on the results of genotyping (in its case, genotyping for CYP2D6 metabolizer status). CONCLUSIONS: TBZ is a complicated drug in terms of its mechanism of action and its activities against the 3 major monoamines in the CNS, making it difficult to predict its efficacy and tolerability in patients with hyperkinetic movement disorders. It is associated with numerous adverse effects and several important drug-drug interactions. Much work remains to be done to determine the therapeutic potential of TBZ in the treatment of hyperkinetic movement disorders.

Quinlobelane: a water-soluble lobelane analogue and inhibitor of VMAT2.

Replacing the phenyl groups in the structure of the VMAT2 inhibitor, lobelane with either pyridyl, quinolyl or indolyl groups affords novel analogues with improved water solubility. The synthetic methodologies reported herein also underscore the paucity of hydrogenation methods that offer selectivity in the synthesis of the different classes of heteroaromatic lobelane analogues. The quinolyl group was the only replacement for the phenyl group in lobelane that retained VMAT2 inhibition.

Biogenic amine depletion causes chronic muscular pain and tactile allodynia accompanied by depression: A putative animal model of fibromyalgia.

Fibromyalgia is a prevalent and burdensome disorder characterized by chronic widespread pain and complex comorbid symptoms. To develop better treatments for pain-centered fibromyalgia symptoms, there is still a need for animal models which mimic the features of fibromyalgia patients. In the present study, we have established a fibromyalgia animal model by utilizing a never-before-published pharmacological effect of reserpine. Repeated administration of reserpine (1mg/kg s.c., once daily, for three consecutive days) causes a significant decrease in the muscle pressure threshold and tactile allodynia, which are sustained for 1week or more in both male and female rats. This treatment regimen decreases the amount of biogenic amines (dopamine, norepinephrine, and 5-hydroxytryptamine) in the spinal cord, thalamus, and prefrontal cortex, which are deeply involved in pain signal processing. It also significantly increases immobility time in the forced swim test, which is indicative of depression, a common comorbid symptom of fibromyalgia. Pregabalin, duloxetine, and pramipexole significantly attenuated the reserpine-induced decrease in muscle pressure threshold, but diclofenac did not. The validity of the use of this reserpinized animal as a fibromyalgia model is demonstrated from three different aspects, i.e., face validity (manifestation of chronic pain and comorbid symptoms), construct validity (dysfunction of biogenic amine-mediated central nervous system pain control is involved), and predictive validity (similar responses to treatments used in fibromyalgia patients). This animal model is expected to contribute to the better understanding of fibromyalgia pathophysiology and the evaluation of drugs, especially those which would activate biogenic amine system.