Irreversible Monoamine oxidase-B Research Articles

Detection of l-Methamphetamine and l-Amphetamine as Selegiline Metabolites.

Selegiline (SE) is a selective, irreversible monoamine oxidase-B inhibitor, used for reducing symptoms in early-stage Parkinson's disease. The metabolites of SE include l-methamphetamine, l-amphetamine and desmethylselegiline (DSE). The stereoisomers of SE metabolites, d-methamphetamine and d-amphetamine are highly addictive psychostimulants and some of the most abused drugs in South Korea. In order to differentiate medical SE users form illicit methamphetamine abusers, it is important to distinguish between the l-isomers and d-isomers in urine samples. A 52-year-old male, seemingly under the influence of intoxication and demonstrating abnormal behavior, was reported to the police. The initial urine test using a methamphetamine detection kit demonstrated a positive result. Given the initial results, the police officer requested a further analysis of the urine sample. The urine sample was screened using headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). Both methamphetamine and amphetamine were detected, in addition to SE and DSE. To quantitate methamphetamine and amphetamine by HS-SPME-GC-MS, we performed a standard addition method due to the matrix effect of the case sample. Consistent with previous studies, our results indicated that the ratio of amphetamine to methamphetamine was 0.27, which was in the range of SE ingestion. Furthermore, we confirmed l-methamphetamine and l-amphetamine by chiral derivatization using (R)-(-)-α-methoxy-α-(trifluoromethyl) phenylacetyl chloride.

Rasagiline antiremodeling action after myocardial infarction may be mediated by circadian rhythm and neurotrophic related gene expression changes

Rasagiline mesylate (RG) is a potent, selective, irreversible monoamine oxidase-B inhibitor, developed to prolong the action of dopamine in the brain. It may rescue degenerating dopamine neurons through inhibiting death signal transduction initiated by the mitochondria permeability transition pore. We have previously shown that it decreases post-experimental infarct remodeling (REM). We investigated whether this cardioprotective result could be due to centrally mediated actions. In a rat model undergoing experimental myocardial infarction (MI) by a permanent ligation of the left anterior descending coronary artery. RG was administered, intraperitoneally for 28 days (2 mg/kg) starting 24 hours after MI induction. Treatment with RG significantly ameliorated cardiac REM echocardiographically as we have previously shown. In order to identify potential new cardioprotective mechanisms of RG action after MI, a comparative RNA expression analysis of remote region cardiac tissue was performed in placebo (Normal saline- NS), RG and Sham samples. RNA-seq analysis results were also confirmed by real time PCR. Our analysis showed: – differential RNA expression of circadian rhythm in NS samples versus RG. Circadian related genes Per3, Ciart, Dbp, Hpd, Nr1d2, and Rev-erb were upregulated while Arntl gene was downregulated (all P < 0.01); – as regards neurotrophic genes, neuropeptide Y (Npy) and neurogranin (Nrgn) genes were downregulated in RG samples compared to NS while the Brain-Derived Neurotrophic Factor (Bdnf) was upregulated (all P < 0.01). Our findings indicate that MI injury influences in a protective manner the expression of circadian rhythm and neurotrophic factor genes in cardiac tissue; potential regulation of these genes is part of the novel cardioprotective mechanism of RG action described, further advocating the possible use of this drug post-MI.

Pharmacokinetics of monoamine oxidase B inhibitors in Parkinson’s disease: current status

ABSTRACTIntroduction: Brain function depends considerably on the neurotransmission of biogenic monoamines. Their metabolism employs monoamine oxidase-B in neuronal and glial cells. Inhibition of monoamine oxidase-B elevates biogenic amine levels. Accordingly, monoamine oxidase-B inhibitors provide a symptomatic effect via dopamine on motor symptoms in patients with Parkinson’s disease.Areas covered: This narrative review aims to describe the pharmacokinetic characteristics of the available reversible and irreversible monoamine oxidase B inhibitors for the treatment of Parkinson’s disease in daily practice. All these compounds are administered on a daily basis.Expert opinion: Reversibility or irreversibility of available monoamine oxidase-B inhibition is not relevant, due to their daily intake and half-life in clinical practice. Irreversible monoamine oxidase-B inhibitors slowed the progression of neuronal dying in experimental models of Parkinson’s disease. In patients, concomitant inhibition of monoamine oxidase-B caused less increase of levodopa dosages over five years. The curve of levodopa increment diverged from the placebo curve. This reduced need for L-dopa monotherapy may be discussed as an indirect biomarker for disease severity and reflects a disease-modifying effect. In case of a symptomatic effect only, parallel curves would have occurred. Long-term L-dopa treatment should be combined with monoamine oxidase-B inhibitors when tolerated by patients.

Efficacy and safety of adjunctive rasagiline in Japanese Parkinson's disease patients with wearing-off phenomena: A phase 2/3, randomized, double-blind, placebo-controlled, multicenter study

IntroductionRasagiline, a selective, irreversible monoamine oxidase-B inhibitor, is in development in Japan as adjunctive therapy to levodopa. This Phase 2/3 trial evaluated the efficacy and safety of adjunctive rasagiline in Japanese patients with Parkinson's disease (PD) and wearing-off phenomena. MethodsPatients aged 30–79 years with diagnosed PD and stable levodopa use were randomized 1:1:1 to rasagiline (0.5/1 mg/day) or placebo for 26 weeks. The primary endpoint was change from baseline in mean daily OFF-time during the treatment period. ResultsIn total, 141, 134, and 129 patients were randomized to placebo, rasagiline 0.5 mg, or rasagiline 1 mg, respectively. Baseline characteristics were well balanced. Least squares (LS) mean differences vs. placebo for change from baseline in mean daily OFF-time were −0.84 h (rasagiline 1 mg/day) and −0.60 h (rasagiline 0.5 mg/day); both differences were statistically significant. LS mean differences vs. placebo for change from baseline in Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) Part II and Part III total scores (in ON-state) and Parkinson's Disease Questionnaire-39 Summary Index Score were: −1.27, −1.74, and −2.51 (0.5 mg/day) and −1.27, −2.14, and −3.84 (1 mg/day); all statistically significant. Treatment-emergent adverse events (TEAEs) occurred in 50.4/69.9/73.6% of the placebo, 0.5 mg/day, and 1 mg/day groups, respectively (most common TEAEs were nasopharyngitis [9.2/18.0/14.7%] and dyskinesia [7.1/8.3/16.3%]). ConclusionsAs an adjunct to levodopa, rasagiline reduced OFF-time and improved PD symptoms/signs (MDS-UPDRS scores) and quality of life in Japanese patients with PD and wearing-off phenomena. No important safety concerns were raised.

Selegiline Ameliorates Depression-Like Behavior in Mice Lacking the CD157/BST1 Gene, a Risk Factor for Parkinson's Disease.

Parkinson’s disease (PD), a neurodegenerative disorder, is accompanied by various non-motor symptoms including depression and anxiety, which may precede the onset of motor symptoms. Selegiline is an irreversible monoamine oxidase-B (MAO-B) inhibitor, and is widely used in the treatment of PD and major depression. However, there are few reports about the effects of selegiline on non-motor symptoms in PD. The aim of this study was to explore the antidepressant and anxiolytic effects of selegiline, using CD157/BST1 knockout (CD157 KO) mouse, a PD-related genetic model displaying depression and anxiety, compared with other antiparkinsonian drugs and an antidepressant, and was to investigate the effects of selegiline on biochemical parameters in emotion-related brain regions. A single administration of selegiline (1–10 mg/kg) dose-dependently reduced immobility time in the forced swimming test (FST) in CD157 KO mice, but not C57BL/6N wild-type (WT) mice. At 10 mg/kg, but not 3 mg/kg, selegiline significantly increased climbing time in CD157 KO mice. A single administration of the antiparkinsonian drugs pramipexole (a dopamine (DA) D2/D3 receptor agonist) or rasagiline (another MAO-B inhibitor), and repeated injections of a noradrenergic and specific serotonergic antidepressant (NaSSA), mirtazapine, also decreased immobility time, but did not increase climbing time, in CD157 KO mice. The antidepressant-like effects of 10 mg/kg selegiline were comparable to those of 10 mg/kg rasagiline, and tended to be stronger than those of 1 mg/kg rasagiline. After the FST, CD157 KO mice showed decreases in striatal and hippocampal serotonin (5-HT) content, cortical norepinephrine (NE) content, and plasma corticosterone concentration. A single administration of selegiline at 10 mg/kg returned striatal 5-HT, cortical NE, and plasma corticosterone levels to those observed in WT mice. In the open field test (OFT), repeated administration of mirtazapine had anxiolytic effects, and selegiline nonsignificantly ameliorated anxiety-like behaviors in CD157 KO mice. In the social interaction and preference tests, repeated mirtazapine ameliorated the high anxiety and low sociability of CD157 KO mice, whereas selegiline did not. These results indicate that selegiline has antidepressant and mild anxiolytic effects in CD157 KO mice, and suggest that it is an effective antiparkinsonian drug for depressive and anxiety symptoms in PD patients with a CD157 single nucleotide polymorphism (SNP).

Simultaneous determination of MAO-A and -B activity following first time intake of an irreversible MAO-B inhibitor in patients with Parkinson's disease.

We determined monoamine oxidase-A (plasma) and -B (platelets) enzyme activity in chronic levodopa treated patients with Parkinson's disease after first time intake of an irreversible monoamine oxidase-B inhibitor. One patient received 10mg selegiline and eleven patients took 1mg rasagiline. A significant decrease of monoamine oxidase-B activity appeared 2 and 4h following monoamine oxidase-B inhibitor intake in comparison to baseline. We confirm with this design, that rasagiline and selegiline inhibit monoamine oxidase-B but not monoamine oxidase-A after single dosing.

Effect of long-term treatment with rasagiline on cognitive deficits and related molecular cascades in aged mice

The present study aimed to investigate the protective effects of prolonged treatment with the selective, irreversible monoamine oxidase-B inhibitor, novel anti-parkinsonian drug, rasagiline (Azilect) in aged animals. Our findings from behavioral experiments demonstrated that long-term treatment of aged mice with rasagiline (0.2 mg/kg) exerted significant beneficial effects on mood-related dysfunction and spatial learning and memory functions. At this dose of rasagiline, chronic drug administration significantly inhibited monoamine oxidase-B activity and caused an increase in striatal dopamine and serotonin levels, while decreasing their metabolism. In addition, rasagiline treatment elevated striatal mRNA expression levels of dopamine receptors D1 and D2. Furthermore, we found that rasagiline upregulated expression levels of the synaptic plasticity markers brain-derived neurotrophic factor, tyrosine kinase-B receptor, and synapsin-1, increased Bcl-2 to Bax antiapoptotic ratio and the activity of the antioxidant enzyme, catalase in brain of aged mice. The present study demonstrated that long-term treatment with rasagiline could affect behavioral deficits in aged mice and upregulate various neuroprotective parameters in the aging brain, indicating that the drug may have therapeutic potential for treatment of age-associated neurodegenerative disorders.

Rasagiline: a review of its use in the treatment of idiopathic Parkinson's disease.

Rasagiline (Azilect(®)) is an oral, second-generation, selective, irreversible monoamine oxidase-B (MAO-B) inhibitor approved in the US for the treatment of Parkinson's disease. In randomized, controlled trials, oral rasagiline 1 mg once daily was superior to placebo in the symptomatic treatment of early Parkinson's disease, both as monotherapy or as an adjunct to dopamine agonists. Comparisons of early-start and delayed-start treatment suggested a disease-modifying effect for rasagiline, but the results were equivocal. Rasagiline 0.5 or 1 mg/day was also superior to placebo as adjunctive therapy to levodopa in Parkinson's disease patients with motor fluctuations. Rasagiline was generally well tolerated in clinical trials, displaying a placebo-like tolerability profile in several studies. Cost-utility studies predicted that rasagiline, either as monotherapy or adjunctive therapy, would be a cost-effective treatment option. Therefore, oral rasagiline is a valuable therapeutic option for use in all stages of Parkinson's disease.

Comparison of neuroprotective and neurorestorative capabilities of rasagiline and selegiline against lactacystin‐induced nigrostriatal dopaminergic degeneration

Nigrostriatal neurodegeneration in Parkinson's disease (PD) has been postulated to be caused by various pathological conditions, such as mitochondrial defects, oxidative stress, and ubiquitin-proteasome system (UPS) dysfunction. Pharmacological strategies designed to interfere with these pathological pathways may effectively counteract the degeneration. Rasagiline and selegiline are selective and irreversible monoamine oxidase-B inhibitors that possess significant protective properties on dopamine neurons in various pre-clinical models of PD. In the present study, the neuroprotective and neurorestorative effects of rasagiline and selegiline were compared in an animal model of PD produced by inhibition of the UPS. C57BL/6 male mice were microinjected bilaterally with UPS inhibitor lactacystin (1.25 mug/side), into the medial forebrain bundle. Administration of rasagiline (0.2 mg/kg, i.p. once per day) or selegiline (1 mg/kg, i.p. once per day), started 7 days before or after (up to 28 days) after lactacystin microinjection. We found that both rasagiline and selegiline exerted a significant neuroprotective effect against lactacystin-induced neurodegeneration; but only rasagiline managed to restore the nigrostriatal degeneration. Furthermore, rasagiline showed a modest protection against lactacystin-induced inhibition of proteasomal activity. Our study indicates that compared with selegiline, rasagiline is more potent in protecting neurodegeneration induced by UPS impairment and may, therefore, exert disease-modifying effects in PD.

Rasagiline is neuroprotective in a transgenic model of multiple system atrophy

Rasagiline is a novel selective irreversible monoamine oxidase-B (MAO-B) inhibitor recently introduced for the symptomatic treatment of Parkinson disease. Like other propargylamines rasagiline has also shown neuroprotective effects independent of MAO-B-inhibition in various in vitro and in vivo models. The present study was performed to test the potential of rasagiline as a disease-modifying agent in multiple system atrophy (MSA) using a transgenic mouse model previously described by our group. (PLP)-α-synuclein transgenic mice featuring glial cytoplasmic inclusion pathology underwent 3-nitropropionic acid intoxication to model full-blown MSA-like neurodegeneration. Two doses of rasagiline were used (0.8 and 2.5 mg/kg) for a treatment period of 4 weeks. Rasagiline-treated animals were compared to placebo saline-treated mice by evaluation of motor behaviour and neuropathology. Motor behavioural tests including pole test, stride length test and general motor score evaluation showed improvements in motor deficits associated with 2.5 mg/kg rasagiline therapy. Immunohistochemistry and histology showed significant reduction of 3-NP-induced neuronal loss in striatum, substantia nigra pars compacta, cerebellar cortex, pontine nuclei and inferior olives of MSA mice receiving 2.5 mg/kg rasagiline. The results of the study indicate that rasagiline confers neuroprotection in a transgenic mouse model of MSA and may therefore be considered a promising disease-modifying candidate for human MSA.

Neuroprotective and neurotoxic effects of monoamine oxidase-B inhibitors and derived metabolites under ischemia in PC12 cells

Selegiline and rasagiline are selective and irreversible monoamine oxidase-B inhibitors that exert neuroprotective effects in various preclinical models. The aim of the present study was to examine the effect of selegiline and its major metabolite, l-methamphetamine in comparison to rasagiline and its major metabolite, 1- R-aminoindan on oxygen–glucose deprivation induced cell death in nerve growth factor (NGF)-differentiated pheochromocytoma (PC12) cells. Our results show that selegiline reduces oxygen–glucose deprivation induced cell death by 30%. When the cultures were treated with rasagiline at similar concentrations, cell death induced by oxygen–glucose deprivation was reduced by 45–55%. l-methamphetamine, a major selegiline metabolite, but not 1- R-aminoindan, the major rasagiline metabolite, enhanced oxygen–glucose deprivation-induced cell death by 70%. Under normoxic conditions, both metabolites lack neurotoxicity. Concomitant exposure of the cultures under oxygen–glucose deprivation, to a combination of either selegiline and l-methamphetamine or rasagiline and 1- R-aminoindan, indicated that l-methamphetamine, but not 1- R-aminoindan, blocked the neuroprotective effect of the parental drug. These results suggest there may be a neuroprotective advantage of rasagiline over selegiline.

Rasagiline, a monoamine oxidase-B inhibitor, protects NGF-differentiated PC12 cells against oxygen-glucose deprivation

In our in vitro model, rasagiline a selective irreversible monoamine oxidase-B (MAO-B) inhibitor, protected nerve growth factor (NGF)-differentiated PC12 cells from cell death under oxygen and glucose deprivation (OGD). The severity of the OGD insult, as expressed by cell death, was time-dependent. Exposure of the cells to OGD for 3 hr followed by 18 hr of reoxygenation caused about 30-40% cell death. Under these conditions, the neuroprotective effect of rasagiline was dose-dependent: rasagiline reducing OGD-induced cell death by 68% and 80% at 100 nM and 1 microM, respectively. The neuroprotective effect of rasagiline was also observed when added after the OGD insult (55% reduction in cell death). Under rasagiline treatment, there was a lesser decrease in ATP content in cultures exposed to OGD compared with that in untreated cultures. OGD followed by reoxygenation resulted in a several fold increase in PGE(2) release into the extracellular medium. Rasagiline (100 nM-1 microM) markedly inhibited OGD-induced PGE(2) release. Clorgyline, a monoamine oxidase-A (MAO-A) inhibitor, did not protect NGF-differentiated PC12 cells against OGD-induced cell death. As NGF-differentiated PC12 cells contain exclusively MAO type A, these data suggest that the neuroprotective effect of rasagiline under OGD conditions is independent of MAO inhibition.

Effects of l-deprenyl treatment on noradrenergic innervation and immune reactivity in lymphoid organs of young F344 rats

Sympathetic noradrenergic (NA) neuronal activities in the thymus, spleen and mesenteric lymph nodes (MLN) and immune responses in the spleen were examined in young male F344 rats treated daily with 0, 0.25 mg, or 2.5 mg/kg body weight of l-deprenyl, an irreversible monoamine oxidase-B (MAO-B) inhibitor. Rats were treated daily for 1, 15, or 30 days, and sacrificed 7 days after the last deprenyl treatment. Deprenyl treatment increased norepinephrine (NE) content in the spleen without modifying the pattern and density of NA innervation in the splenic white pulp. The concentration of NE was unaltered in the thymus, but it was increased in the MLN of deprenyl-treated rats. One day of treatment with deprenyl decreased splenic NK cell activity while 15 days of deprenyl treatment enhanced splenic NK cell activity. Deprenyl elevated Con A-induced T lymphocyte proliferation following 30 days of treatment, but did not alter spleen cell Con A-induced IL-2 production or the percentage of CD5+ T cells in the spleen. A moderate decrease in the percentage of sIgM+ B cells was observed in the spleens of 15- and 30-day deprenyl-treated rats. These results suggest that deprenyl has sympathomimetic action on sympathetic NA nerve fibers in the spleen; the enhancement of NA neuronal activity may contribute to the modulation of immune responses in the spleen.

L-deprenyl-induced increase in IL-2 and NK cell activity accompanies restoration of noradrenergic nerve fibers in the spleens of old F344 rats

Previously, we have hypothesized a causal relationship between some measures of immunosenescence and the age-related decline in sympathetic noradrenergic (NA) nerve fibers in spleen and lymph nodes of F344 rats. In the present study, we investigated this interrelationship further by measuring NK cell activity, Con A-induced IL-2 production, norepinephrine (NE) concentration, and morphological localization of NA and neuropeptide-Y (NPY) nerve fibers in the spleens of old (21 months old) male F344 rats after 10 weeks of daily treatment with low doses of l-deprenyl, an irreversible monoamine oxidase-B inhibitor, followed by a 9-day wash-out period. NK cell activity and Con A-induced IL-2 production were increased in deprenyl-treated old rats in comparison to untreated and saline-treated old rats. Deprenyl treatment did not alter the percentage of CD5+ T-cells, but moderately increased the percentage of sIgM + B-cells in the spleens of old rats. In addition to changes in immune responses, NE content and the volume density of NA and NPY nerve fibers were partially augmented in the spleens of deprenyl-treated old rats. In a separate study, various concentrations of deprenyl were added in vitro to spleen cells from young and old F344 rats to examine the direct effects of the drug on Con A-induced IL-2 production. In contrast to in vivo treatment, in vitro addition of deprenyl did not alter the Con A-induced IL-2 production by splenocytes from old rats. Together, these results suggest that the ability of deprenyl to enhance certain immune responses are interlinked to the restoration of sympathetic NA and NPY nerve fibers in the spleens of old rats.

Restoration of sympathetic noradrenergic nerve fibers in the spleen by low doses of l-deprenyl treatment in young sympathectomized and old Fischer 344 rats

It is well-established that noradrenergic (NA) nerve fibers in spleen and lymph nodes influence cell-mediated immune responses. Such responses are diminished in young animals following chemical sympathectomy and in older animals accompanying an age-related decline in NA nerve fibers in spleen and lymph nodes. The purpose of this study was to determine whether treatment with deprenyl, an irreversible monoamine oxidase-B (MAO-B) inhibitor, would hasten the process of splenic NA reinnervation following chemical sympathectomy in young rats and would reverse the age-related loss of sympathetic NA fibers in the spleen of old rats. To examine the effects of deprenyl in young sympathectomized rats, 3-month-old male Fischer 344 (F344) rats were treated with 6-hydroxydopamine (6-OHDA) and administered 0, 0.25, 1.0, 2.5, or 5.0 mg deprenyl/kg body weight (BW)/day intraperitoneally (i.p.) for 1, 15, or 30 days. In another study, 21-month-old male F344 rats were treated with 0, 0.25, or 1.0 mg deprenyl/kg BW/day i.p. for 9 weeks. At the end of the treatment period, spleens were removed and NA innervation was assessed by fluorescence histochemistry, immunocytochemistry, and quantitation of norepinephrine (NE) by high performance liquid chromatography with electrochemical detection (HPLC-EC). In the spleens of young sympathectomized rats, there was faint fluorescence or absence of fluorescence and tyrosine hydroxylase-positive (TH+) fibers around the central arteriole and in the periarteriolar lymphatic sheath of the white pulp one day after administration of 6-OHDA, indicating a severe loss of NA innervation compared with unlesioned control animals. Treatment of sympathectomized rats with 1.0 mg, 2.5 mg, and 5.0 mg/kg deprenyl for 30 days increased the density of NA innervation estimated by both fluorescence histochemistry and immunocytochemistry compared with vehicle-treated controls recovering spontaneously from 6-OHDA. Splenic NE concentration was increased in the hilar region of sympathectomized rats treated with 2.5 mg and 1.0 mg/kg deprenyl after 15 and 30 days, respectively, compared with untreated and vehicle-treated sympathectomized rats. The spleens of untreated and saline-treated old rats showed a reduction in the density of NA innervation in the white pulp compared with young animals. Treatment of old rats for 9 weeks with 1.0 mg/kg deprenyl induced moderate to intense fluorescent fibers and linear TH+ nerve fibers around the central arteriole and in other compartments of the white pulp, and increased splenic NE concentration in the hilar region and NE content in the whole spleen. Taken together, these results provide strong evidence for a neurorestorative property of deprenyl on sympathetic NA innervation of the spleen, which may lead to an improvement in cell-mediated immune responses.

The effect of l-deprenyl, d-deprenyl and MDL72974 on mitochondrial respiration: a possible mechanism leading to an adaptive increase in superoxide dismutase activity

l-Deprenyl is an irreversible monoamine oxidase-B inhibitor with a complex pharmacological profile. For instance, l-deprenyl administration to rat and mice increases cytosolic CuZn- and mitochondrial Mn-superoxide dismutase activities in the striatum. CuZn- and Mn-superoxide dismutase are enzymes involved in defense against superoxide (O 2 ⋅) radicals. Hence, an increase in CuZn- and Mn-superoxide dismutase activities is suggestive of oxidative stress. The major intracellular site of O 2 ⋅ radicals formation is the mitochondrial respiratory chain. Several reports indicated that alterations in mitochondrial respiratory functions enhances O 2 ⋅ production. We observed that l-deprenyl induced a dose-dependent inhibition of oxygen (O 2) consumption (state 3) during ATP synthesis in presence of complex I (pyruvate and malate) and complex II (succinate) substrates in fresh mitochondrial preparations. d-Deprenyl produced a similar inhibitory profile whereas MDL72974, a selective monoamine oxidase-B inhibitor, was less effective. Administration of d-deprenyl or MDL72974 to mice resulted in an increase in both striatal CuZn- and -Mn-superoxide dismutase activities. Accordingly, we propose that the impairment of mitochondrial respiratory functions which stimulates O 2 ⋅ formation could modulate CuZn- and Mn-superoxide dismutase activities, through a mechanism that appears to be independent of monoamine oxidase-B inhibition.

Enantioselective gas chromatographic assay of 2-alkylamines using N-(trifluoroacetyl)prolyl derivatives and a chiral capillary column

The chromatographic properties of (R)-(+)-N-(trifluoroacetyl)prolyl and (S)-(-)-N-(trifluoroacetyl)prolyl derivatives on a chiral gas chromatography capillary column were assessed for the measurement of enantiomeric purities of 2-butylamine, 2-pentylamine, 2-hexylamine, 2-heptylamine and 2-octylamine and their N-methyl analogues, which are used as precursors in the synthesis of some selective, specific, irreversible monoamine oxidase-B inhibitors. Using a Chirasil-Val column it was possible to separate all four diastereomers of the primary amines, and three of the four isomers of the secondary amines. Quantitation of the enantiomers is facilitated even with enantiomerically impure reagent when compared to the use of an achiral phase.

Absence of acute cocaine interactions with the MAO-B inhibitor selegiline

Selegiline, an irreversible monoamine oxidase-B (MAO-B) inhibitor, is under investigation as a treatment for cocaine relapse prevention. To evaluate its safety, human volunteers ( n = 5) received intravenous cocaine (0, 20 and 40 mg, 1 h apart) following treatment with placebo or selegiline (10 mg, p.o.). Cocaine increased heart rate, blood pressure, pupil diameter and subjective indices of euphoria and craving. Selegiline produced no measurable effects, except for miosis, and did not alter the effects of cocaine. These data suggest that selegiline may be safely administered in combination with cocaine, and that selegiline is unlikely to increase reinforcing effects of cocaine.

Inhibition of monoamine oxidases by haloperidol and its metabolites: pharmacological implications for the chemotherapy of schizophrenia.

The effect of haloperidol and its metabolites on human platelet monoamine oxidase B (MAO-B) and human placenta monoamine oxidase A (MAO-A) in vitro has been investigated. We found that 4-(4-chlorophenyl)-1-[4-(4-fluorophenyl)-4-oxobutyl]-pyridinium (HP+), 4-(4-chlorophenyl)-1-[4-(4-fluorophenyl)-4-oxobutyl]-1,2,3,6- tetrahydropyridine (HTP) and 4-chlorophenyl-1,2,3,6-tetrahydropyridine (CPTP) are potent inhibitors of MAO. HP+ appeared to be a reversible, uncompetitive and selective MAO-B inhibitor with a Ki of 0.83 microM. HTP was found to be an irreversible, uncompetitive and selective MAO-B inhibitor (Ki of 1.84 microM). CPTP inhibits both MAO-A and MAO-B. Some other haloperidol metabolites, i.e. 4-(4-chlorophenyl)-4-hydroxypyridine (CPHP), 4-(4-chlorophenyl)-1-[4-(4-fluorophenyl)-4-oxobutyl]-1,2,3,6- tetrahydropyridine N-oxide (HTPNO) and reduced haloperidol (RHAL), do not inhibit MAO to any appreciable degree at concentrations up to 100 microM. The results suggest that haloperidol metabolites may contribute to the reduction of platelet MAO-B activity in schizophrenic patients undergoing neuroleptic chemotherapy. An examination of the literature reveals that schizophrenic patients with low platelet MAO activity exhibit a strong association with the use of haloperidol. Other possible pharmacological implications of the inhibition of MAO activity are discussed.