Evaluation of monoamine oxidase A and B type enzyme occupancy using non-radiolabelled tracers in rat brain

Monoamine oxidase (MAO) enzymes, type A and B metabolise the amine neurotransmitters of the body. Selective inhibition of either enzyme is an approach for treating neurodegenerative and stress-induced disorders, and inhibition of an enzyme is proportional to the binding of the MAO inhibitor. Conventionally, the binding of test compounds to enzymes is assessed by radiolabelled ligands in ex vivo and in vivo occupancy assays. Regulatory restrictions and turnaround time are the limitations of the methods that use radiolabelled ligands. But the use of non-radiolabelled tracers and sensitive mass spectrometry (LC-MS/MS) based assays accelerated the determination of target occupancy in pre-clinical species. A report on use of non-radiolabelled ligand in in vivo MAO occupancy assay is not available. The objectives of the present study were to optimise non-radiolabelled harmine and deprenyl as selective tracers in MAO-A and MAO-B occupancy assays and evaluate MAO occupancy of test compounds in rat brain. Tracer optimisation resulted in a detectable, stable, and low ratio (<3.0) of tracer concentrations between any two brain tissues. In occupancy assay, tracer was intravenously administered (10 μg/kg, harmine or 60 μg/kg, L-deprenyl) after the treatment with test compound (clorgyline or tranylcypromine or pargyline or phenelzine or thioperamide). Specific brain tissues were isolated at a defined interval and tracer concentrations were quantified using LC-MS/MS method. Pre-treatment with MAO inhibitors resulted in a decrease (maximum, 80-85%) in harmine or an increase (maximum, 85-300%) in L-deprenyl concentrations. But we considered the change in tracer concentration, relative to the vehicle and positive control groups to calculate MAO occupancy. The observed selectivity and ratio of occupancies (ED₅₀) of test compound towards MAO-A and MAO-B are comparable with the results from in vitro radiolabelled ligand-based inhibition assay. The results demonstrated the application of these non-radiolabelled tracers as suitable pre-clinical tools to determine MAO occupancy.

Large nest building and high marble-burying: Two compulsive-like phenotypes expressed by deer mice (Peromyscus maniculatus bairdii) and their unique response to serotoninergic and dopamine modulating intervention

This study aimed to further dissect the deer mouse (Peromyscus maniculatus bairdii) model of compulsive-like behavior with respect to two persistent-like behavioral phenotypes viz. large nest building (LNB) and high marble-burying (HMB), which may be relevant to understanding the neurobiology of different symptom dimensions in obsessive-compulsive and related disorders. Since LNB is sensitive to chronic, high dose escitalopram intervention but HMB is not, we assessed whether the two behaviors could be further distinguished based on their response to 4 weeks of uninterrupted serotoninergic intervention (i.e. escitalopram; ESC; 50 mg/kg/day), dopaminergic antagonism, i.e. flupentixol; FLU; 0.9 mg/kg/day), dopaminergic potentiation (i.e. rasagiline; RAS; 5 mg/kg/day), and their respective combinations with escitalopram (ESC/FLU and ESC/RAS). Here we show LNB to be equally responsive to chronic ESC and ESC/FLU. HMB was insensitive to either of these interventions but was responsive to ESC/RAS. Additionally, we report that scoring preoccupied interaction with marbles over several trials is an appropriate measure of compulsive-like behavioral persistence in addition to the standard marble burying test. Taken together, these data provide further evidence that LNB and HMB in deer mice have distinctive neurobiological underpinnings. Thus, the naturally occurring compulsive-like behaviors expressed by deer mice may be useful in providing a platform to test unique treatment targets for different symptom dimensions of OCD and related disorders.

Chronic harmine treatment has a delayed effect on mobility in control and socially defeated rats

INTRODUCTION

Depression is characterized by behavioral, cognitive and physiological changes, imposing a major burden on the overall wellbeing of the patient. Some evidence indicates that social stress, changes in growth factors (e.g., brain-derived neurotrophic factor (BDNF)), and neuroinflammation are involved in the development and progression of the disease. The monoamine oxidase A inhibitor drug harmine was suggested to have both antidepressant and anti-inflammatory properties and may, therefore, be a potential candidate for treatment of depression.

AIM

The goal of this study was to assess the effects of harmine on behavior, brain BDNF levels, and microglia activation in control rats and a rat model of social stress.

MATERIAL AND METHODS

Rats were submitted to 5 consecutive days of repeated social defeat (RSD) or control conditions. Animals were treated daily with harmine (15 mg/kg) or vehicle from day 3 until the end of the experiment. To assess the effects of harmine treatment on behavior, the sucrose preference test (SPT) was performed on days 1, 6, and 15, the open field test (OFT) on days 6 and 14, and the novel object recognition test (NOR) on day 16. Brain microgliosis was assessed using [11C]PBR-28 PET on day 17. Animals were terminated on day 17, and BDNF protein concentrations in the hippocampus and frontal cortex were analyzed using ELISA.

RESULTS

RSD significantly decreased bodyweight and increased anxiety and anhedonia-related parameters in the OFT and SPT on day 6, but these behavioral effects were not observed anymore on day 14/15. Harmine treatment caused a significant reduction in bodyweight gain in both groups, induced anhedonia in the SPT on day 6, and significantly reduced the mobility and exploratory behavior of the animals in the OFT mainly on day 14. PET imaging and the NOR test did not show any significant effects on microglia activation and memory, respectively. BDNF protein concentrations in the hippocampus and frontal cortex were not significantly affected by either RSD or harmine treatment.

DISCUSSION

Harmine was not able to reverse the acute effects of RSD on anxiety and anhedonia and even aggravated the effect of RSD on bodyweight loss. Moreover, harmine treatment caused unexpected side effects on general locomotion, both in RSD and control animals, but did not influence glial activation status and BDNF concentrations in the brain. In this model, RSD-induced stress was not strong enough to induce long-term effects on the behavior, neuroinflammation, or BDNF protein concentration. Thus, the efficacy of harmine treatment on these delayed parameters needs to be further evaluated in more severe models of chronic stress.

Long-Term Efficacy of Safinamide on Symptoms Severity and Quality of Life in Fluctuating Parkinson's Disease Patients

BACKGROUND

Parkinson's disease (PD) is characterized by a wide range of motor and non-motor symptoms. Levodopa is still the most effective drug; however, its long-term use is associated with motor complications which may deteriorate patient's quality of life. Safinamide is a unique treatment modulating both dopaminergic and glutamatergic systems. Previous results from two six months, double-blind, placebo-controlled studies demonstrated that safinamide has positive effects on both motor functions and quality of life in PD patients.

OBJECTIVE

To investigate the effects of safinamide 100 mg/day over two-year treatment on PD symptoms severity and quality of life, using data from the study 018.

METHODS

Data from 352 patients were analyzed to evaluate the effects of safinamide on OFF time and ON time (with no or non-troublesome dyskinesia) in the overall population and in subgroups of patients (receiving levodopa monotherapy or with other anti-Parkinson therapies), and the effects of safinamide on motor symptoms/clinical fluctuations (by means of UPDRS III and IV) and on health-related quality of life (using UPDRS II and PDQ-39 summary index score).

RESULTS

Safinamide, administered as add-on to standard therapy in fluctuating PD patients, significantly improved motor symptoms and clinical fluctuations in the overall population and in some subgroups of patients. Additionally, safinamide improved quality of life and activities of daily living, maintaining the efficacy in the long-term.

CONCLUSIONS

The findings of these analyses suggest that safinamide may be considered an appropriate adjunct therapy in patient not sufficiently controlled. Further investigations are desirable to confirm these results in usual care setting.

Monoamine oxidase inhibitors protect against coronary heart disease in rodent rat models: A pilot study

The present study designed to investigate the effect of monoamine oxidase inhibitor in the rat model of Coronary heart disease (cardiac hypertrophy). A total of 40 male adult Wistar rats having body weight 300-400 gram were equally distributed in two groups (Test group: Rats with Angiotensin II + monoamine oxidase inhibitor (Befloxatone); Reference group: Rats with cardiac hypertrophy induced by Angiotensin II). Rat model of cardiac hypertrophy were induced by Angiotensin II. Effect of Befloxatone on cardiac hypertrophy was evaluated by electrocardiography, hemodynamic and histological assessment. Vital signs such as pulse rate, and blood pressure were measured. Echocardiographic related variable including ejection fraction were also assessed in both the groups. Also, expression of monoamine oxidase was analyzed using by real-time-PCR and Western blot analysis. In results, we found following 1) monoamine oxidase inhibitor treatment prevents Angiotensin II induced increase in level of ANP and βeta-myosin, which are responsible for inducing cardiac hypertrophic responses; 2) monoamine oxidase inhibitor ameliorates Angiotensin II induced cell enlargement by reducing the surface area of cells; 3) monoamine oxidase inhibitor attenuates the hypertrophic response triggered by Angiotensin II; 4) monoamine oxidase inhibitor ameliorates increased heart rate and average arterial pressure induced by angiotensin II; 5) Overall finding suggested that monoamine oxidase inhibitor improves left ventricle hypertrophy and ejection fraction by inhibiting monoamine oxidase enzyme in heart. The finding of this study gives the new vision to cardiovascular researchers to develop anti- hypertrophy therapy based on monoamine oxidase inhibition.

Rasagiline monotherapy in early Parkinson's disease: A phase 3, randomized study in Japan

BACKGROUND

Rasagiline is a monoamine oxidase type-B inhibitor in development in Japan for Parkinson's disease (PD). The objective of this Phase 3, randomized, double-blind study was to evaluate the efficacy and safety of rasagiline in Japanese patients with early PD (NCT02337725).

METHODS

Patients were 30-79 years old with a diagnosis of PD within 5 years. Following a two-week placebo run-in period, patients were randomized 1:1 to receive rasagiline (1 mg/day) or placebo for up to 26 weeks. The primary endpoint was change from baseline in the MDS-UPDRS Part II + III total score (TS). Secondary endpoints included the MDS-UPDRS Parts II + III, III, II, and I TS and safety.

RESULTS

In total, 118 patients were randomized to rasagiline and 126 to placebo. Patient characteristics at baseline were similar in both groups. The change from baseline in the MDS-UPDRS Part II + III TS was significantly greater in the rasagiline vs. placebo group (rasagiline-placebo: -6.39, 95% CI: -8.530, -4.250; P < 0.0001). The mean changes from baseline in the MDS-UPDRS Part II + III, Part III and Part II TS were lower at treatment visits between weeks 6 and 26 in the rasagiline vs. placebo groups. The overall incidence of treatment-emergent adverse events (TEAEs) was 62.4% and 52.4% in the rasagiline and placebo groups, respectively; most frequent TEAE was nasopharyngitis (15.4% and 15.1%).

CONCLUSION

Treatment with oral rasagiline 1 mg/day was effective and well-tolerated in Japanese patients with early PD, with a significantly greater improvement in the MDS-UPDRS Part II + III TS vs. placebo, and a similar safety profile.

Body fat reduction without cardiovascular changes in mice after oral treatment with the MAO inhibitor phenelzine

BACKGROUND AND PURPOSE

Phenelzine is an antidepressant drug known to increase the risk of hypertensive crisis when dietary tyramine is not restricted. However, this MAO inhibitor inhibits other enzymes not limited to the nervous system. Here we investigated if its antiadipogenic and antilipogenic effects in cultured adipocytes could contribute to decreased body fat in vivo, without unwanted hypertensive or cardiovascular effects.

EXPERIMENTAL APPROACH

Mice were fed a standard chow and given 0.028% phenelzine in drinking water for 12 weeks. Body composition was determined by NMR. Cardiovascular dysfunction was assessed by heart rate variability analyses and by evaluation of cardiac oxidative stress markers. MAO activity, hydrogen peroxide release and triacylglycerol turnover were assayed in white adipose tissue (WAT), alongside determination of glucose and lipid circulating levels.

KEY RESULTS

Phenelzine-treated mice exhibited lower body fat content, subcutaneous WAT mass and lipid content in skeletal muscles than control, without decreased body weight gain or food consumption. A modest alteration of cardiac sympathovagal balance occurred without depressed aconitase activity. In WAT, phenelzine impaired the lipogenic but not the antilipolytic actions of insulin, MAO activity and hydrogen peroxide release. Phenelzine treatment lowered non-fasting blood glucose and phosphoenolpyruvate carboxykinase expression. In vitro, high doses of phenelzine decreased both lipolytic and lipogenic responses in mouse adipocytes.

CONCLUSION AND IMPLICATIONS

As phenelzine reduced body fat content without affecting cardiovascular function in mice, it may be of benefit in the treatment of obesity-associated complications, with the precautions of use recommended for antidepressant therapy.

Positron emission tomography measurement of brain MAO-B inhibition in patients with Alzheimer's disease and elderly controls after oral administration of sembragiline

PURPOSE

In Alzheimer's disease (AD), increased metabolism of monoamines by monoamine oxidase type B (MAO-B) leads to the production of toxic reactive oxygen species (ROS), which are thought to contribute to disease pathogenesis. Inhibition of the MAO-B enzyme may restore brain levels of monoaminergic neurotransmitters, reduce the formation of toxic ROS and reduce neuroinflammation (reactive astrocytosis), potentially leading to neuroprotection. Sembragiline (also referred as RO4602522, RG1577 and EVT 302 in previous communications) is a potent, selective and reversible inhibitor of MAO-B developed as a potential treatment for AD.

METHODS

This study assessed the relationship between plasma concentration of sembragiline and brain MAO-B inhibition in patients with AD and in healthy elderly control (EC) subjects. Positron emission tomography (PET) scans using [11C]-L-deprenyl-D2 radiotracer were performed in ten patients with AD and six EC subjects, who received sembragiline each day for 6-15 days.

RESULTS

At steady state, the relationship between sembragiline plasma concentration and MAO-B inhibition resulted in an Emax of ∼80-90 % across brain regions of interest and in an EC50 of 1-2 ng/mL. Data in patients with AD and EC subjects showed that near-maximal inhibition of brain MAO-B was achieved with 1 mg sembragiline daily, regardless of the population, whereas lower doses resulted in lower and variable brain MAO-B inhibition.

CONCLUSIONS

This PET study confirmed that daily treatment of at least 1 mg sembragiline resulted in near-maximal inhibition of brain MAO-B enzyme in patients with AD.

Safinamide: A Review in Parkinson's Disease

Safinamide (Xadago^®) is an orally active, selective, reversible monoamine oxidase-B inhibitor with both dopaminergic and non-dopaminergic (glutamatergic) properties. In the EU, safinamide is approved for the treatment of mid- to late-stage fluctuating Parkinson's disease (PD) as add-on therapy to a stable dose of levodopa alone or in combination with other PD medications. Safinamide 50-100 mg/day administered as a fixed or flexible dose significantly increased daily 'on' time without dyskinesia (primary endpoint) in patients with mid- to late-stage PD with motor fluctuations in 24-week, placebo-controlled clinical trials. Other outcomes, including motor function, overall clinical status and health-related quality of life, were also generally improved with safinamide. Furthermore, in an 18-month extension of one study, although dyskinesia (primary endpoint) was not significantly improved with safinamide relative to placebo, treatment benefits in other outcomes were generally sustained over 24 months of treatment. Safinamide was generally well tolerated in clinical trials; dyskinesia was the most common adverse event. Although further studies are needed, including comparative and long-term studies, current evidence indicates that safinamide extends the treatment options available for use as add-on therapy to levodopa and other PD medications in patients with mid- to late-stage PD experiencing motor fluctuations.

Selective inhibition of MAO-A activity results in an antidepressant-like action of 2-benzoyl 4-iodoselenophene in mice

Depression is a leading cause of disability worldwide. For this reason, the aim of this study was to investigate the possible antidepressant-like activity of 2-benzoyl-4-iodoselenophene (C₁₇H₁₁IOSe), a selenophene compound, in two well-consolidated behavioral assays for screening antidepressant activity (forced swimming test and tail suspension test) in mice. In order to investigate the mechanism of action of C₁₇H₁₁IOSe, it was investigated the activities of cerebral enzymes: monoamine oxidase MAO A and B and Na⁺, K⁺ ATPase, and if an inhibitor of serotonin synthesis, p-chlorophenylalanine (pCPA) (100mg/kg) blocks the antidepressant-like effect of C₁₇H₁₁IOSe. Swiss mice received (C₁₇H₁₁IOSe) (5-50mg/kg) or canola oil by the intragastric (i.g.) route before behavioral tests. The results showed that C₁₇H₁₁IOSe at dose range of 5-50mg/kg decreased immobility time in the tail suspension test. In the forced swimming test, C₁₇H₁₁IOSe reduced the immobility time at the doses of 10 and 50mg/kg. C₁₇H₁₁IOSe differently affected the cerebral cortical Na⁺, K⁺ ATPase; the effects on this enzyme were dependent of the dose tested. At a dose of 10mg/kg, the compound increased Na⁺, K⁺ ATPase activity, while the activity was inhibited at a dose of 50mg/kg. pCPA blocked the antidepressant-like action of C₁₇H₁₁IOSe in mice. Therefore, C₁₇H₁₁IOSe (5-50mg/kg) selectively inhibited MAO-A activity in cerebral cortices of mice. The modulation of serotonergic system contributed to the antidepressant-like action of C₁₇H₁₁IOSe in mice.

Movement Disorders: A Brief Guide in Medication Management

Movement disorders can be challenging to manage and often use a specific set of medications. Because it is a complex and broad field within neurology, many providers are unfamiliar with the classes of medications. This paper details medications used for specific conditions, explains why these medications are helpful, and shares pearls and pitfalls related to each agent, focusing on parameters such as dose titration, side effect profiles, and specific drug-drug interactions and challenges. We focus on the most commonly encountered movement disorders, including essential tremor, Parkinson's disease, rapid eye movement sleep behavior disorder, and restless leg syndrome.

Design, synthesis and evaluation of novel dual monoamine-cholinesterase inhibitors as potential treatment for Alzheimer's disease

Current novel therapeutic approach suggests that multifunctional compounds with diverse biological properties and a single bioavailability and pharmacokinetic metabolism, will produce higher significant advantages in treatment of neurodegenerative diseases, such as Alzheimer's disease (AD). Based on this rational, a new class of cholinesterase (ChE)-monoamine oxidase (MAO) inhibitors were designed and synthesized by amalgamating the propargyl moiety of the irreversible selective MAO-B inhibitor, neuroprotective/neurorestorative anti-Parkinsonian drug, rasagiline, into the "N-methyl" position of the ChE inhibitor, anti-AD drug rivastigmine. Initially, we examined the MAO and ChE inhibitory effect of these novel compounds, MT series in vitro and in vivo. Among MT series, MT-031 exhibited higher potency as a dual MAO-A and ChE inhibitor compared to other compounds in acute-treated mice. Additionally, MT-031 was found to increase the striatal levels of dopamine (DA), serotonin (5-HT) and norepinephrine (NE), and prevent the metabolism of DA and 5-HT. Finally, we have demonstrated that MT-031 exerted neuroprotective effect against H2O2-induced neurotoxicity and reactive oxygen species generation in human neuroblastoma SH-SY5Y cells. These findings provide evidence that MT-031 is a potent brain permeable novel multifunctional, neuroprotective and MAO-A/ChE inhibitor, preserves in one molecule entity some of the beneficial properties of its parent drugs, rasagiline and rivastigmine, and thus may be indicated as novel therapeutic approach for AD.

Targeting Dopaminergic System for Treating Nicotine Dependence

BACKGROUND

Smoking is the world's leading cause of preventable death among populations. Cigarette smoking increases the risk of numerous health problems, including heart diseases, stroke, atherosclerosis and many types of cancer, including lung, stomach and bladder cancers.

OUTCOMES

Many individuals find it difficult to stop smoking because of the addictive effects of nicotine and the presence of several monoamine oxidase (MAO) inhibitors in the tobacco smoke extract.

OBJECTIVE

The development of novel, safe and effective medications for smoking cessation is a high public health priority.

RESULTS

The role of mesocorticolimbic dopaminergic pathways in withdrawal symptoms and general reinforcement processes clearly recommends dopaminergic system as a potential target for the treatment of nicotine addiction.

CONCLUSION

This review article discusses the new pharmacological treatments of nicotine dependence, which are targeting dopaminergic neurotransmission. This includes blockade of dopamine transporter and inhibition of MAO as pharmacotherapy for the treatment of nicotine dependence.

[The use of the monoamine oxidase inhibitor isocarboxazide in treatment-resistant depression]

The antidepressant efficacy of isocarboxazide is well established; however, the clinical use early became restricted and today the use of isocarboxazide in Denmark is very limited. Isocarboxazide is safe when keeping a low tyramine-containing diet and avoiding concomitant treatment with certain drugs. The risk of developing oedema can be reduced by vitamin B6 treatment. Normal dosage isocarboxazide may be prescribed for all patients because isocarboxazide is not metabolized through the CYP2D6 enzyme complex like most other antidepressants. It is recommended to include isocarboxazide in the official treatment algorithms for patients who are resistant to conventional antidepressant therapy and electroconvulsive therapy.

Monoamine oxidase-A is an important source of oxidative stress and promotes cardiac dysfunction, apoptosis, and fibrosis in diabetic cardiomyopathy

Oxidative stress is closely associated with the pathophysiology of diabetic cardiomyopathy (DCM). The mitochondrial flavoenzyme monoamine oxidase A (MAO-A) is an important source of oxidative stress in the myocardium. We sought to determine whether MAO-A plays a major role in modulating DCM. Diabetes was induced in Wistar rats by single intraperitoneal injection of streptozotocin (STZ). To investigate the role of MAO-A in the development of pathophysiological features of DCM, hyperglycemic and age-matched control rats were treated with or without the MAO-A-specific inhibitor clorgyline (CLG) at 1 mg/kg/day for 8 weeks. Diabetes upregulated MAO-A activity; elevated markers of oxidative stress such as cardiac lipid peroxidation, superoxide dismutase activity, and UCP3 protein expression; enhanced apoptotic cell death; and increased fibrosis. All these parameters were significantly attenuated by CLG treatment. In addition, treatment with CLG substantially prevented diabetes-induced cardiac contractile dysfunction as evidenced by decreased QRS, QT, and corrected QT intervals, measured by ECG, and LV systolic and LV end-diastolic pressure measured by microtip pressure transducer. These beneficial effects of CLG were seen despite the persistent hyperglycemic and hyperlipidemic environments in STZ-induced experimental diabetes. In summary, this study provides strong evidence that MAO-A is an important source of oxidative stress in the heart and that MAO-A-derived reactive oxygen species contribute to DCM.

[The development from drug to designer drug]

Synthetic "designer drugs" with hallucinogenic properties have become increasingly popular among recreational drug users in recent years. Some of the designer drugs are chemically modified drugs previously used in treatment of depression and chronic fatigue. The drugs are available from a large number of internet distributers. There is very little knowledge of the clinical symptoms and how intoxicated people should be treated. We present a review of published literature (including 284 intoxicated patients) and experiences from the Danish poison centre concerning two chemical derivatives of earlier registered drugs.

[Seven cases of parathyroidectomy for secondary hyperparathyroidism using methylene blue: suggestion for the method of methylene blue infusion]

BACKGROUND

Intraoperative staining of the parathyroid glands with intravenously administered methylene blue is well described and has been demonstrated as an effective and safe method to facilitate parathyroidectomy. However, there have been several literatures of the development of postoperative neurological toxicity in patients who received methylene blue infusion during parathyroidectomy. We report the method of methylene blue infusion during parathyroidectomy at our institution.

METHODS

Seven adult patients who had undergone parathyroidectomy for secondary hyperparathyroidism associated with chronic renal failure were included in this study. Methylene blue was administered at a constant rate of 4 mg x kg(-1) x hr(-1) with a 1% solution just before the start of operation. The infusion was stopped after the first parathyroid gland was identified.

RESULTS

The mean dose of methylene blue used was 2.2 +/- 0.8 mg x kg(-1). Consequently, the dose of methylene blue by this method could be decreased to less than half of the previously administered dose (6 mg x kg(-1)) at our institution.

CONCLUSIONS

The dose of methylene blue used should be kept to the minimum required to identify the parathyroid glands in each case.

[Dopaminergic treatment in Parkinson's disease: what has each therapeutic family got to offer?]

Different families of dopaminergic agents have allowed to increase the availability of dopamine within the central nervous system by different mechanisms of action. Each drug family has specific efficacious properties, as well as a different profile of adverse events. The knowledge in detail of these specificities is mandatory to avoid severe systemic or neuropsychiatric complications. Despite these limitations, the development of new drugs within the past 20 years has prolonged survival in Parkinson's disease, increasing the time with preserved daily day functionality compared with the levodopa era, when this drug was the only dopaminergic drug available. The correct combination of dopaminergic drugs with different mechanisms of action allows the management of Parkinson's disease motor symptoms within safety dose ranges, and up to day, this appears as the best algorithm to maintain functionality for longer periods of time.

Current place of monoamine oxidase inhibitors in the treatment of depression

This paper reviews the discovery and history of the use of irreversible monoamine oxidase (MAO) inhibitors (MAOIs) such as phenelzine, tranylcypromine and isocarboxazid, as well as the second generation selective and reversible MAOIs such as the MAO-A inhibitor, moclobemide and the MAO-B inhibitor, selegiline. Data for review were identified from a literature search of OvidSP Medline and PsycInfo performed in July 2012, using the subject terms and keywords of 'monoamine oxidase inhibitors', 'major depression', 'depressive disorder' and 'depression (emotion)'. The search was limited to papers published in the English language and from 2007 onward only. Irreversible MAOIs have the potential to treat the most challenging mood disorder patients including those with treatment-resistant depression, atypical depression and bipolar depression. Unfortunately, the use of irreversible MAOIs has been declining sharply due to lack of marketing and the excessive fears of clinicians. Moreover, few clinicians now have any experience, let alone comfort, in prescribing this class of antidepressants. The newer MAOIs are available as another option for the treatment of major depression but have not replaced the irreversible MAOIs for the specific sub-types of depression for which they are now recommended in most consensus guidelines and treatment algorithms. The pharmacology, drug interactions and dietary recommendations associated with the use of MAOIs are reviewed. With the appropriate dietary restrictions and attention to potential drug interactions with serotonin and noradrenaline agents this class of drugs can be used effectively and safely. The MAOIs still represent an important element in our therapeutic armamentarium. Despite recommendations by opinion leaders and consensus guidelines for the use of MAOIs in specific sub-types of depression, the prescription rate of MAOIs is far less than expected and is decreasing. The "bad reputation" and the lack of industry support for this class of agents (especially the irreversible MAOIs) must be overcome in order to continue to provide a potentially useful treatment for a very vulnerable yet substantial sub-population of mood disorder patients.

Linezolid: Pharmacokinetic and Pharmacodynamic Evaluation of Coadministration with Pseudoephedrine HCl, Phenylpropanolamine HCl, and Dextromethorphan HBr

Linezolid is a novel oxazolidinone antibiotic with mild reversible monoamine oxidase inhibitor (MAOI) activity. The potential for interaction with over-the-counter (OTC) medications requires quantification. The authors present data evaluating the pharmacokinetic and pharmacodynamic responses to coadministration of oral linezolid with sympathomimetics (pseudoephedrine and phenylpropanolamine) and a serotonin reuptake inhibitor (dextromethorphan). Following coadministration with linezolid, minimal but statistically significant increases were observed in pseudoephedrine and phenylpropanolamine plasma concentrations; a minimal but statistically significant decrease was observed in dextrorphan (the primary metabolite of dextromethorphan) plasma concentrations. Increased blood pressure (BP) was observed following the coadministration of linezolid with either pseudoephedrine or phenylpropanolamine; no significant effects were observed with dextromethorphan. None of these coadministered drugs had a significant effect on linezolid pharmacokinetics. Minimal numbers of adverse events were reported. Potentiation of sympathomimetic activity by linezolid was judged not to be clinically significant, but patients sensitive to the effects of increased BP due to predisposing factors should be treated cautiously. No restrictions are indicated for the coadministration of dextromethorphan and linezolid.

Tyramine Pressor Sensitivity During Treatment With the Selegiline Transdermal System 6 mg/24 h in Healthy Subjects

The oral tyramine pressor test was administered to healthy males during treatment with a selegiline transdermal system (STS; 6 mg/24 h). The tyramine sensitivity factor (TSF) was calculated from the ratio of baseline and on-treatment tyramine pressor doses. The tyramine sensitivity factor value following 9 days of treatment with the selegiline transdermal system was 1.85 +/- 0.10. Extended treatment, 33 days, produced a small, clinically non-meaningful increase in this value. The tyramine sensitivity factor for the selegiline transdermal system was similar to that following treatment with 10 mg/d of oral selegiline capsules but more than 20 times less than observed during tranylcypromine treatment. A larger increase in the tyramine sensitivity factor was observed following extended selegiline transdermal system treatment at a higher dose (12 mg/24 h), which was significantly decreased following coadministration of tyramine capsules with a meal. These results suggest a wide tyramine safety margin for the selegiline transdermal system and provide evidence that the 6-mg/24-h selegiline transdermal system can be administered safely without dietary tyramine restrictions.

Selegiline Transdermal System: An Examination of the Potential for CYP450-Dependent Pharmacokinetic Interactions With 3 Psychotropic Medications

Selegiline transdermal system (STS) is a recently approved monoamine oxidase inhibitor antidepressant. This article reports results from 3 studies examining the potential for cytochrome P450-dependent pharmacokinetic interactions between STS and 3 psychotropic medications that might be coadministered. Three open-label, randomized, Latin square, 3-sequence crossover design studies were conducted with healthy volunteers to determine the pharmacokinetic parameters of STS 6 mg/24 h and test drug (alprazolam, olanzapine, or risperidone) when administered alone and concomitantly. All pharmacokinetic parameters of interest were unaltered following selegiline or test drug monotherapy when compared to concomitant therapy. This was confirmed by least squares mean ratios and their 90% confidence intervals of log(e)-transformed C(max) and AUC(tau) values, using either standard bioequivalence criteria of 80% to 125% or study-defined 70% to 143% boundary criteria. These results demonstrate that STS 6 mg/24 h may provide an antidepressant option that is unlikely to result in CYP450-mediated pharmacokinetic drug-drug interactions.

[Rasagiline in monotherapy in patients with early stages of Parkinson's disease and in combined and adjunct therapy to levodopa with moderate and advanced stages]

Rasagiline is effective in the early stages of the disease and has shown a possible effect of modifying disease progression at a dose of 1 mg. The accurate management of dopaminergic drugs in Parkinson's disease is able to delay the appearance of motor fluctuations and dyskinesias. The combination of different drugs that provide a more continuous dopaminergic stimulation (rasagiline, dopamine agonists) not only exerts a benefit through diminishing the impact of pulsatile stimulation on post-synaptic dopamine receptors, but allows to decrease total daily levodopa requirements. The combination of rasagiline with other dopaminergic drugs has demonstrated to be as efficacious as entacapone for improving both the frequency and severity of motor fluctuations. Likewise, new evidences have shown that the earlier introduction of rasagiline is associated with a delay in introducing other dopaminergic drugs, thus indicating that the symptomatic benefit of rasagiline on daily motor function is not only present in the early Parkinson's disease stages, but is maintained over time.

Evaluation of the safety and tolerability of rasagiline in the treatment of the early stages of Parkinson's disease

OBJECTIVE

Rasagiline is a second-generation, irreversible MAO-B inhibitor (MAOB-I) previously shown to be efficacious and well-tolerated compared to placebo in the treatment of early Parkinson's disease (PD). ACTOR (ACceptabilité TOlérance Rasagiline) was a 15-week, multi-center, randomized, double-blind study aimed to assess the safety and tolerability of rasagiline compared to the dopaminergic agonist pramipexole in the treatment of early PD.

METHODS

Patients with early, untreated idiopathic PD were randomized to receive 1 mg rasagiline (n = 53) or 1.5 mg pramipexole (n = 56) daily. The primary outcome was the number of patients experiencing a 'clinically important adverse event' (classified as a serious adverse event, an event leading to withdrawal or severe according to the patient). Safety outcomes were evaluated by the investigator and the patient. Analysis of the primary criterion was a comparative analysis using the chi-squared test. The Wilcoxon Mann-Whitney test was conducted to test the severity of patient-reported adverse events. Other tests performed include a covariance analysis and Student's t-tests.

RESULTS

Mean disease duration was 3.4 months, and mean age was 62.6 years. Of patients taking pramipexole, 44.6% reported at least one 'clinically important' adverse event compared to 32.1% of patients taking rasagiline; non-inferiority of rasagiline was reached, with a difference in proportions of -12.6% [confidence interval of -27.8%; 2.6%]. There were no significant differences in clinical effectiveness between the treatments, measured by clinical and patient global impression of improvement (CGI-I, PGI-I) and PDQ-8 scales. A significant decrease in the incidence of gastrointestinal symptoms (p = 0.015) and sleep disorders (p = 0.027) was reported by physicians in the rasagiline group compared to the pramipexole group; the propensity to sleepiness improved significantly in the rasagiline group (p = 0.020), and worsened in the pramipexole group (p = 0.042).

LIMITATIONS

Limitations of this study include the limited sample size due to the lower than anticipated recruitment and the accidental inclusion of a patient who had taken contraindicated medication.

CONCLUSIONS

In this study, the safety profile of rasagiline had clinically favorable differences in gastrointestinal and sleep adverse events compared to pramipexole, whilst showing comparable clinician and patient-rated clinical effectiveness as a monotherapy for the treatment of early idiopathic PD.

[The role of the MAO-B inhibitor razagiline in the treatment of Parkinson's disease]

The features of the new selective MAO-B inhibitor razagiline (azilect) are reviewed against the background of latest advances in the field of treatment of Parkinson's disease (PD). The authors present the results of treatment of 20 patients in the full-blown stage of disease (mean age of patients 61.4±7.0 years). One of the objectives was to study the effect of razagiline on speech disorders in PD. A battery of scales was used to assess the global efficacy of treatment and the effect of the drug on the groups of symptoms. The high symptomatic effect of the drug used as monotherapy in early stages and in the combination with levodopa drugs in the full-blown stages of disease was revealed. It has been concluded that razagiline has a neuroprotective effect and modifies the course of PD. It exerts an effect on axial symptoms of PD: reduces speech disorders, postural instability, frequency of freezing episodes, severity of pharmacological dyskinesias.

Failure to improve cigarette smoking abstinence with transdermal selegiline + cognitive behavior therapy

AIMS

To examine the effectiveness of transdermal selegiline for producing cigarette smoking abstinence.

DESIGN

Adult smokers were randomly assigned to receive selegiline transdermal system (STS) or placebo given for 8 weeks. All participants received cognitive behavior therapy (CBT). Follow-ups were conducted at 25 and 52 weeks.

SETTING

Community smoking cessation clinic.

PARTICIPANTS

243 adult smokers (> or =18 years of age; > or =10 cigarettes/day).

MEASURES

Expired-air carbon monoxide confirmed 7-day point prevalence abstinence.

FINDINGS

STS was not superior to placebo. More women than men were abstinent at 52 week follow-up (28% vs 16%, P < 0.05). Behavioral activation (BAS) moderated treatment response (P = 0.01). The survival rate through week 52 for those with high 'drive' scores on the BAS was 47% if assigned to selegiline and 34% if assigned to placebo. The survival rate for those with low 'drive scores' on the BAS was 35% if assigned to selegiline compared to 53% if assigned to placebo.

CONCLUSION

Transdermal selegiline does not appear generally effective in aiding smoking cessation though there may be a selective effect in those smokers with low 'behavioral activation'.

The role of rasagiline in the treatment of Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder, affecting 1% to 2% of people older than 60 years. Treatment of PD consists of symptomatic therapies while neuroprotective strategies have remained elusive. Rasagiline is a novel, potent, and irreversible monoamine oxidase type B (MAO-B) inhibitor which has been approved for treatment of PD. Rasagiline inhibits MAO-B more potently than selegiline and has the advantage of once-daily dosing. In several large, randomized, placebo-controlled trials, rasagiline has demonstrated efficacy as monotherapy in early PD and as adjunctive therapy in advanced PD. In addition, rasagiline has been shown to have neuroprotective effects in in vitro and in vivo studies. The recently completed delayed-start ADAGIO (Attenuation of Disease Progression with Azilect Given Once-daily) trial suggests a potential disease-modifying effect for rasagiline 1 mg/day, though the clinical import of this finding has yet to be established.

Transdermal selegiline in patients receiving electroconvulsive therapy

BACKGROUND

Concurrent use of monoamine oxidase inhibitors (MAOIs) during a course of electroconvulsive therapy (ECT) is controversial.

OBJECTIVE

In this report, the authors present outcomes of this concurrent treatment approach.

METHOD

The authors present two cases of patients taking the newest MAOI approved for depression, namely, transdermal selegiline, while receiving ECT.

RESULTS

The authors conclude that there is no evidence of complications or adverse events associated with concurrent use of ECT and low-dose transdermally administered selegiline.

CONCLUSION

The authors further conclude that beginning a low dose of transdermal selegiline before finishing a course of ECT is a viable option for relapse prevention in the treatment of depression.

A double-blind, placebo-controlled, randomized clinical trial of oral selegiline hydrochloride for smoking cessation in nicotine-dependent cigarette smokers

AIM

The primary aim of this study was to determine the safety and efficacy of the monoamine oxidase-B (MAO-B) inhibitor selegiline hydrochloride (SEL, l-Deprenyl; Eldepryl) as an aid for smoking cessation in cigarette smokers.

METHODS

One hundred and one nicotine-dependent adult cigarette smokers without current psychiatric or substance use disorders participated in this 8-week randomized, double-blind, placebo-controlled trial. Participants received either SEL (5mg bid, n=51) or placebo (PLO, n=50), in combination with brief (<10 min) manualized smoking cessation counseling. The main smoking outcome measures were 7-day point prevalence abstinence at end of trial (EOT), 4-week continuous smoking abstinence at end of trial (CA), and 7-day point prevalence abstinence at 6-month follow-up (6MFU). Abstinence was determined by an absence of self-reported cigarette smoking and biochemically verified by expired breath carbon monoxide and plasma cotinine levels.

RESULTS

Rates of smoking abstinence did not differ by medication group (EOT: SEL=16%, PLO=20%, p=0.57; CA: SEL=14%, PLO=18%, p=0.56; 6MFU: SEL=12%, PLO=16%, p=0.54). Adverse events were modest and comparable between medication groups. Participants receiving SEL were more likely than those receiving PLO to report dry mouth (25.5% versus 8.2%, p<0.05).

CONCLUSIONS

Our results suggest that SEL was safe and well-tolerated by adult cigarette smokers, but did not improve smoking abstinence rates compared to PLO.

A double-blind, delayed-start trial of rasagiline in Parkinson's disease

BACKGROUND

A therapy that slows disease progression is the major unmet need in Parkinson's disease.

METHODS

In this double-blind trial, we examined the possibility that rasagiline has disease-modifying effects in Parkinson's disease. A total of 1176 subjects with untreated Parkinson's disease were randomly assigned to receive rasagiline (at a dose of either 1 mg or 2 mg per day) for 72 weeks (the early-start group) or placebo for 36 weeks followed by rasagiline (at a dose of either 1 mg or 2 mg per day) for 36 weeks (the delayed-start group). To determine a positive result with either dose, the early-start treatment group had to meet each of three hierarchical end points of the primary analysis based on the Unified Parkinson's Disease Rating Scale (UPDRS, a 176-point scale, with higher numbers indicating more severe disease): superiority to placebo in the rate of change in the UPDRS score between weeks 12 and 36, superiority to delayed-start treatment in the change in the score between baseline and week 72, and noninferiority to delayed-start treatment in the rate of change in the score between weeks 48 and 72.

RESULTS

Early-start treatment with rasagiline at a dose of 1 mg per day met all end points in the primary analysis: a smaller mean (+/-SE) increase (rate of worsening) in the UPDRS score between weeks 12 and 36 (0.09+/-0.02 points per week in the early-start group vs. 0.14+/-0.01 points per week in the placebo group, P=0.01), less worsening in the score between baseline and week 72 (2.82+/-0.53 points in the early-start group vs. 4.52+/-0.56 points in the delayed-start group, P=0.02), and noninferiority between the two groups with respect to the rate of change in the UPDRS score between weeks 48 and 72 (0.085+/-0.02 points per week in the early-start group vs. 0.085+/-0.02 points per week in the delayed-start group, P<0.001). All three end points were not met with rasagiline at a dose of 2 mg per day, since the change in the UPDRS score between baseline and week 72 was not significantly different in the two groups (3.47+/-0.50 points in the early-start group and 3.11+/-0.50 points in the delayed-start group, P=0.60).

CONCLUSIONS

Early treatment with rasagiline at a dose of 1 mg per day provided benefits that were consistent with a possible disease-modifying effect, but early treatment with rasagiline at a dose of 2 mg per day did not. Because the two doses were associated with different outcomes, the study results must be interpreted with caution. (ClinicalTrials.gov number, NCT00256204.)

Downregulation of oligodendrocyte transcripts is associated with impaired prefrontal cortex function in rats

Abnormalities of brain white matter and oligodendroglia are among the most consistent findings in schizophrenia (Sz) research. Various gene expression microarray studies of post-mortem Sz brains showed a downregulation of myelin transcripts, while imaging and microscopy studies demonstrated decreases in prefrontal cortical (PFC) white matter volume and oligodendroglia density. Currently, the extent to which reduced oligodendrocyte markers contribute to pathophysiological domains of Sz is unknown. We exposed adolescent rats to cuprizone (CPZ), a copper chelator known to cause demyelination in mice, and examined expression of oligodendrocyte mRNA transcripts and PFC-mediated behavior. Rats on the CPZ diet showed decreased expression of mRNA transcripts encoding oligodendroglial proteins within the medial PFC, but not in the hippocampus or the striatum. These rats also displayed a specific deficit in the ability to shift between perceptual dimensions in the attentional set-shifting task, a PFC-mediated behavioral paradigm modeled after the Wisconsin Card Sorting Test (WCST). The inability to shift strategies corresponds to the deficits exhibited by Sz patients in the WCST. The results demonstrate that a reduction in oligodendrocyte markers is associated with impaired PFC-mediated behaviors. Thus, CPZ exposure of rats can serve as a model to examine the contribution of oligodendrocyte perturbation to cognitive deficits observed in Sz.

Aromatic L-amino acid decarboxylase deficiency: clinical features, drug therapy and follow-up

BACKGROUND

Aromatic L-amino acid decarboxylase (AADC) deficiency is a disorder of biogenic amine metabolism resulting in generalized combined deficiency of serotonin, dopamine and catecholamines. Main clinical features are developmental delay, muscular hypotonia, dystonia, oculogyric crises and additional extraneurological symptoms. Response to therapy has been variable and unsatisfactory; the overall prognosis is guarded.

METHODS

To gain more insight into this rare disorder we collected clinical and laboratory data of nine German patients. All patients were clinically examined by one investigator, and their responses to different drug regimes were evaluated by the patients' charts.

RESULTS

Symptoms were obvious from early infancy. Later, main neurological features were truncal muscular hypotonia, hypokinesia, oculogyric crises and rigor. Three patients had single seizures. All patients presented distinct extraneurological symptoms, such as hypersalivation, hyperhidrosis, nasal congestion, sleep disturbances and hypoglycaemia. In CSF all patients revealed the pattern typical of AADC with decreased concentrations of homovanillic and 5-hydroxyindoleacetic acid and elevated concentration of 3-ortho-methyldopa. Diagnosis was confirmed by measurement of AADC activity in plasma in all patients. Drug regimes consisted of vitamin B6, dopamine agonists, MAO inhibitors and anticholinergics in different combinations. No patient achieved a complete recovery from neurological symptoms, but partial improvement of mobility and mood could be achieved in some.

CONCLUSION

AADC deficiency is a severe neurometabolic disorder, characterized by muscular hypotonia, dystonia, oculogyric crises and additional extraneurological symptoms. Medical treatment is challenging, but a systematic trial of the different drugs is worthwhile.

Treatment of Parkinson's disease in Thailand: review of the literature and practical recommendations

The mainstay of treatment for Parkinson's Disease (PD) remains symptomatic despite the rapid expansion in knowledge of its neurodegenerative process. Therapeutic options, both medical and surgical, have been markedly improved over the past decades, resulting in better motor function, activities of daily living, and quality of life for PD patients. The principle of PD management should be individualized and the selection of treatments should aim to control symptoms as well as to prevent or delay motor complications. In Thailand, various pharmacologic and surgical options are available, including different formulations of levodopa, dopamine agonists, monoamine oxidase B inhibitor, cathechol-O-methyltransferase inhibitor pallidotomy, and lastly deep brain stimulation. The use of dopamine agonists in early PD has a levodopa-sparing effect and reduces the incidence of motor complications. Continuous dopaminergic stimulation (CDS), which mimics physiological activation of dopaminergic receptors, has been proposed as a strategy to prevent motor complications. Based on current evidence, practical guidelines in the medical management of different types of motor complications are outlined in the present article according to what are available in Thailand. Surgical interventions should be reserved for patients with intractable motor complications after careful patient selection.

Serum prolactin as a tool for the follow-up of treated DHPR-deficient patients

Deficiency of dihydropteridine reductase causes a variant form of phenylketonuria associated with a devastating neurological disease characterized by mental retardation, hypokinesis and other features relating to basal ganglia disorder. Hyperphenylalaninaemias with tetrahydrobiopterin deficiency make up about 1-3% of all hyperphenylalaninaemias. We describe three patients from Calabria, a southern region of Italy, who have a dihydropteridine reductase deficiency, caused by the same mutation (p.L14P) also found in the nearby region of Sicily. We report the evolution of clinical and biochemical data during the treatment of these patients where we used prolactin serum determination to adapt the specific therapy. This report suggests that serum prolactin levels can be a good biomarker for optimal dosage of hydroxylated precursors in long-term treatment monitoring.

The effect of short-term administration of (-)-deprenyl and isatin on the expressions of some genes in the mouse brain cortex

BACKGROUND

Isatin (indoledione 2,3) is an endogenous indole found in the mammalian brain, peripheral tissues, and body fluids. It exhibits many neurophysiological and neuropharmacological effects. It shares some common molecular targets with (-)-deprenyl, a neuroprotective pharmacological drug. Some isatin effects imply a possible influence of gene expression; however, no isatin-responsive genes have yet been identified.

MATERIAL/METHODS

In this study the effects of a three-week administration of isatin (20 mg/kg) or (-)-deprenyl (1 mg/kg) on the expressions of several putative isatin/deprenyl-responsive genes in the mouse cortex were compared using real-time PCR.

RESULTS

Both treatments caused similarly significant decreases in superoxide dismutase (SOD) mRNA. Treatment of mice with either drug decreased glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA, although only in the deprenyl-treated mice was this significant (p<0.01). No significant changes were found in cortex mRNA content of monoamine oxidase A or monoamine oxidase B.

CONCLUSIONS

The results suggest that isatin and (-)-deprenyl have some common target genes and this supports the idea that isatin may be an endogenous partial functional agonist of (-)-deprenyl. Since GAPDH mRNA expression is sensitive to the pharmacological treatments, these results also question the applicability of GAPDH as a reference gene in gene expression studies.

The monoamine oxidase inhibitor phenelzine enhances the discriminative stimulus effect of nicotine in rats

In addition to delivering nicotine, tobacco smoke also inhibits monoamine oxidase (MAO). Although MAO inhibitors (MAOIs) can increase nicotine self-administration in rodents, the effects of MAOIs on the discriminative stimulus effect of nicotine are not known. This study examined the effects of three MAOIs (phenelzine, clorgyline and pargyline) with varying selectivity for MAOA and MAOB in the nicotine drug discrimination procedure in rats. Adult male Sprague-Dawley rats were trained to discriminate nicotine (0.3 mg/kg, subcutaneously) from saline in a standard, two-lever food-reinforced operant task. Once the discrimination was acquired, the ability of each MAOI to substitute for or alter the discriminative stimulus effect of nicotine was determined. In substitution tests, nicotine (0.03-0.3 mg/kg) produced full, dose-dependent substitution. Although the selective MAOA inhibitor clorgyline (3-56 mg/kg) and the selective MAOB inhibitor pargyline (3-56 mg/kg) did not elicit any nicotine-appropriate responding, partial substitution was obtained with the nonselective MAO inhibitor phenelzine (1-17 mg/kg). Phenelzine (10 mg/kg) also enhanced the discriminative stimulus effect of a low dose of nicotine (0.056 mg/kg) and prolonged the time course effect of the nicotine-training dose. These findings indicate that concomitant inhibition of MAOA and MAOB can enhance the discriminative stimulus effect of nicotine in rats.

The selegiline transdermal system in major depressive disorder: a systematic review of safety and tolerability

BACKGROUND

Monoamine oxidase inhibitors (MAOIs) are highly efficacious antidepressants, but safety concerns have limited their broad use.

METHODS

We reviewed key safety and tolerability data from all clinical trials of patients with major depressive disorder (MDD) accrued during the clinical development of the selegiline transdermal system (STS), as reported to the Food and Drug Administration. This review includes data from both controlled and uncontrolled clinical trials involving STS-treated (n=2036) and placebo-treated (n=668) patients.

RESULTS

Except for the initial trial, subsequent trials, which involved STS doses ranging from 3 mg/24 h to 12 mg/24 h, lacked tyramine restrictions, and no acute hypertensive reactions occurred during study treatment. Safety experience with STS 6 mg/24 h supports this therapeutic dose without tyramine dietary modifications, but until more data are available for STS doses 9 mg/24 h and 12 mg/24 h, foods that are rich sources of tyramine should be avoided. The principal side effects of STS therapy were local dermal reactions and insomnia, both of which were dose-related. Side effects associated with MAOI treatment, such as sexual dysfunction and excessive weight gain, were uncommon.

CONCLUSIONS

A comprehensive review of safety from the clinical development program suggests that the STS is safe and well tolerated, with an improved safety margin compared with orally administered MAOIs.

The guinea pig forced swim test as a new behavioral despair model to characterize potential antidepressants

RATIONALE

Behavioral despair is a model of high predictivity for antidepressant activity in murids. For some drug targets, guinea pigs exhibit a higher homology to their human counterparts compared to murids.

OBJECTIVES

In this paper, we established a model of behavioral despair namely, the forced swim test (FST) in guinea pigs.

MATERIALS AND METHODS

Male guinea pigs underwent the FST similar to rats. Animals received intraperitoneal injections of either vehicle or drugs 24, 4, and 0.5 h before testing. We tested the tricyclic antidepressants desipramine and amitriptyline, the monoamine oxidase inhibitor tranylcypromine, the selective serotonin reuptake inhibitors fluoxetine and paroxetine, and the neurokinin 1 (NK(1)) receptor antagonist, L-733,060, and for comparison the antipsychotic clozapine and the stimulant methamphetamine.

RESULTS

Desipramine (> or =3 mg/kg) and amitriptyline (>10 mg/kg) increased the latency to immobility (LTI) to greater than 230 s, and tranylcypromine (10 mg/kg) it to greater than 190 s. Paroxetine (>0.3 mg/kg) and fluoxetine (>10 mg/kg) also increased LTI significantly but only to greater than 120 s. Methamphetamine (3 mg/kg) completely eliminated immobility, whereas clozapine (5-20 mg/kg) had no effect. L-733,060 (10 mg/kg) increased LTI to 270 s. Doses producing significant effects in FST were investigated in the open field. Antidepressants did not affect locomotion, whereas methamphetamine induced hyperlocomotion.

CONCLUSIONS

We demonstrate the suitability of a modified procedure of the FST for a nonmurid species: the guinea pig. Known antidepressants showed similar effects as in rats and mice. It is interesting to note that the NK(1) antagonist L-733,060 increased forced swimming, suggesting its antidepressant potential. Thus, the guinea pig FST allows the study of antidepressant activity also in NK(1) antagonists that cannot be studied appropriately in murids.

Gestational exposure to nicotine and monoamine oxidase inhibitors influences cocaine-induced locomotion in adolescent rats

RATIONALE

Many pregnant women continue to smoke, despite a strong association between maternal smoking and neurobehavioral deficits in the offspring. Although gestational nicotine (GN) treatment in rodents is used as the primary animal model of maternal smoking, tobacco smoke contains more than 4,000 constituents, including monoamine oxidase inhibitors (MAOIs).

OBJECTIVES

The aim of this study was to determine whether there are interactions between the effects of gestational exposure to nicotine and MAOIs on cocaine-induced locomotor sensitization in adolescent rats.

MATERIALS AND METHODS

Pregnant rats were implanted on day 4 of gestation with osmotic minipumps delivering saline, nicotine (3 mg/kg per day), the MAOIs clorgyline and deprenyl (1 and 0.25 mg/kg per day, respectively), or nicotine/clorgyline/deprenyl (GMN). Adolescent female offspring were tested for cocaine-induced locomotor sensitization. Animals were treated with saline or cocaine (5 or 15 mg/kg, intraperitoneally) daily from postnatal (P) days 32-36 and challenged with cocaine (15 mg/kg) on P51 (day 20).

RESULTS

Group differences were observed in chronic but not acute effects of cocaine. Whereas gestational MAOI treatment, with or without nicotine, increased ambulatory response to cocaine on day 5, the opposite was found for vertical activity. Different adaptive responses were observed on cocaine challenge day. GNM animals exhibited enhanced locomotor activity in the cocaine-associated environment before cocaine challenge on day 20. In contrast, only GN animals exhibited significant locomotor sensitization to the cocaine challenge.

CONCLUSIONS

Gestational nicotine and MAOIs both influence brain development. Such interactions may sensitize adolescents to drug abuse and should be considered in animal models of maternal smoking.