Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0011570 (depression)
 172,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Reboxetine is the first commercially available norepinephrine reuptake inhibitor developed specifically as a first line therapy for major depressive disorder. In vitro and in vivo pharmacological studies indicated that reboxetine methanesulphonate has high affinity and selectivity for the human norepinephrine transporter over the serotonin and dopamine transporters. Pharmacological specificity is further demonstrated by the absence of affinity for 45 transmitter receptors and CNS targets. Pharmacokinetic studies demonstrated that reboxetine is suitable for twice daily administration (8-10 mg/day) and that it exhibits minimal drug-drug interactions. The starting dose of reboxetine should be reduced in the elderly, in patients with renal or hepatic impairment, or in patients receiving potent CYP3A inhibitors. A total of 20 phase II/III clinical studies comprising placebo-controlled, active comparator-controlled and open-label uncontrolled studies in both short-term and long-term treatment of major depression have been conducted. In the treatment of major depression, reboxetine was superior to placebo in 5 of 12 short- or long-term placebo-controlled studies and was comparable in efficacy to active comparators in 3 out of 3 active-controlled studies. Unlike conventional tricyclic antidepressants (TCAs), reboxetine had only minimal sedative and cardiovascular liabilities, probably due to increased pharmacological specificity of reboxetine as compared with TCAs. Unlike serotonin reuptake inhibitors, this selective and specific norepinephrine reuptake inhibitor demonstrated a distinct side-effect profile with diminishing sexual dysfunction and GI side effects. The availability of this agent has afforded patients suffering from major depressive disorder a new class of agents to combat the debilitating consequence of this psychiatric disease. The demonstrated pharmacological specificity of this compound has provided the psychopharmacology community with a tool to elucidate the role of norepinephrine in brain functions. Testing this agent in different animal models has enabled the exploration of the role of modulation of norepinephrine tone in the therapy of CNS disorders beyond depression.
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PMID:The selective norepinephrine reuptake inhibitor antidepressant reboxetine: pharmacological and clinical profile. 1497 12

Following exocytotic release of the biogenic amine neurotransmitters, norepinephrine and dopamine, are removed from the synaptic cleft by the respective transporter, norepinephrine transporter (NET) and dopamine transporter (DAT) located on the plasma membrane. The catecholamine transporters are the molecular targets for psychoactive drugs as well as drugs of abuse such as cocaine and amphetamine and the Parkinsonism-inducing neurotoxin, MPP+. Nicotine regulates the transport of catecholamines and MPP+ and may exert self-medicating effects for depression, schizophrenia and attention deficit hyperactivity disorder, and neuroprotective effects against MPP+ through the regulation of the transporters. The availability of cDNAs of these transporters has permitted detailed pharmacological studies in heterologous expression systems for determining the mechanisms of action of nicotine on transporters. Moreover, functional analysis of the effect of single amino acid substitution suggests that specific residues in DAT molecules may play a significant role in interaction with MPP+ and cocaine, and thus would promise a development of novel drugs with diverse chemical structures.
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PMID:Regulation of dopamine and MPP+ transport by catecholamine transporters. 1516 8

Reboxetine, 2-[alpha-(2-ethoxyphenoxy)benzyl]morpholine, is a highly selective norepinephrine transporter (NET) blocker that has been used for the treatment of depression. Its methyl analogue, 2-[alpha-(2-methoxyphenoxy)benzyl]morpholine (MRB), has been radiolabeled with C-11 for studies of the NET system with positron emission tomography (PET). The normethyl precursor, 2-[alpha-(2-hydroxyphenoxy)benzyl]morpholine (desethylreboxetine), was synthesized in 6% overall yield via a multi-step regio- and stereo-specific synthesis, starting from a mono-O-protected catechol. The resulting racemic mixture of desethylreboxetine was resolved by chiral HPLC to provide the (2S,3S) and (2R,3R) enantiomers in >98% enantiomeric excess. These enantiomers were then used as precursors for radiosynthesis to prepare enantiomerically pure individual 11C-labeled MRB enantiomers for comparative PET studies in baboons. Selective C-11 methylation at the phenolic oxygen with [11C]CH3I was achieved in the presence of excess base. After HPLC purification, racemic ((2S,3S)/(2R,3R)) or enantiomerically pure ((2S,3S) or (2R,3R)) [11C]MRB was obtained in 61-74% decay-corrected radiochemical yields from [11C]CH3I in a synthesis time of 40 min with a radiochemical purity of >96% and a specific activity of 1.7-2.3 Ci/micromol (63-85 GBq/micromol) corrected from the end of bombardment (EOB).
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PMID:Synthesis, enantiomeric resolution, and selective C-11 methylation of a highly selective radioligand for imaging the norepinephrine transporter with positron emission tomography. 1523 45

Pancreatic ganglia contain noradrenergic nerve terminals whose role in ganglionic transmission is unknown. Intracellular recordings from rabbit pancreatic neurons were used to study the effects of alpha-adrenergic agonists and antagonists on ganglionic transmission and to determine if endogenously released norepinephrine contributed to synaptic depression. Significant regional differences in alpha adrenergic effects were observed. In neurons from ganglia of the head/neck region norepinephrine or selective alpha(2) agonists presynaptically inhibited ganglionic transmission and this effect was antagonized by the alpha(2) antagonist yohimbine. In the majority of cells membrane hyperpolarization accompanied presynaptic inhibition during superfusion of alpha(2) agonists. Repetitive nerve stimulation evoked a presynaptic post-train depression (PTD) of ganglionic transmission in all neurons tested. A combination of nisoxetine (selective inhibitor of the norepinephrine transporter) and tyramine (releaser of endogenous catecholamines) increased PTD. Pretreatment with clonidine inhibited synaptic transmission and abolished PTD while yohimbine did not affect it. Pretreatment with guanethidine (>or=3.5 h) also failed reduce PTD while neurons unresponsive to alpha(2) adrenoceptor agonists routinely exhibited PTD, implying the presence of other inhibitory neurotransmitters sharing a common presynaptic mechanism with alpha(2) agonists. In the majority of neurons from ganglia of the body region superfusion of norepinephrine or the selective alpha(1) agonist phenylephrine evoked membrane depolarization and facilitated ganglionic transmission. These effects were antagonized by the alpha(1) antagonist prazosin. The remaining neurons exhibited either alpha(2)-mediated synaptic inhibition or no-response. In conclusion, inhibitory alpha(2) and excitatory alpha(1) adrenoceptors exist in pancreatic ganglia and predominate in the head/neck and body, respectively. Norepinephrine, released during repetitive nerve stimulation, may contribute to synaptic depression in the head/neck region and appeared to share a common mechanism with other, unidentified neurotransmitters mediating synaptic depression in both regions. These differences indicate a functional heterogeneity of pancreatic sympathetic innervation that may reflect the reported regional differences in exocrine and endocrine cells.
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PMID:Alpha-adrenergic modulation of synaptic transmission in rabbit pancreatic ganglia. 1612 10

This paper provides a review of safety and efficacy data as well as of pharmacological characteristics of atomoxetine, a new drug treatment for the Attention Deficit/Hyperactivity Disorder (ADHD). To date, the only pharmacological treatment available in France for children and adolescents diagnosed with ADHD is methylphenidate, a psychostimulant drug. However, the clinical response to methylphenidate may be absent or insufficient in about 20-30% drug-treated children while the occurrence of adverse effects with methylphenidate (sleep disturbances, loss of appetite, tics increase...) may sometimes require a dose reduction or even the discontinuation of the treatment. Atomoxetine is an alternative candidate drug for the treatment of ADHD. The drug has been developed with respect to the actual standards of investigation of drugs intended to a -pediatric use. Atomoxetine has been recently licensed in the USA for the treatment of ADHD. Atomoxetine is a potent inhibitor of the norepinephrine transporter that shows only mini-mal affinity for other neurotransmitter systems. Although pharmacokinetics of atomoxetine is influenced by the polymorphism of the CYP2D6 metabolic pathway, safety and -tolerability data reported during clinical trials did not show any difference in poor versus extensive metabolizers. In addition, atomoxetine does not inhibit nor induce the CYP2D6 enzymatic function. The major metabolite of atomoxetine is 4-hydroxyatomoxetine, a pharmacologically active metabolic found in very low plasma concentrations in pediatric patients, suggesting that it plays only a minor role in the norepinephrine reuptake inhibition. Preliminary studies were aimed to assess the effective dose range of atomoxetine and to evaluate its safety and efficacy on the reduction of ADHD symptoms in adults and children diagnosed with ADHD. Main data on the child and adolescent population were obtained in four double-blind, randomized, placebo-controlled trials: two identical pivotal trials, a multiple dose study, a once-daily dose study. The first two pivotal trials were carried out in ADHD children aged 7-13 years, treated with atomoxetine vs placebo for a duration of 9 weeks. Patients presenting comorbidities (ie conduct disorder, -anxiety, depression) as well as a history of previous treatment with methylphenidate were also eligible to participate. The primary outcome was the reduction of the score on the ADHD rating scale, ADHD-RS ; secondary criteria included the responder's rate (patients with an ADHD-RS score reduction of 25% or above), the Clinical Global Impression Scale and the Conners Parent Rating Scale. With a mean dose of 1.5 mg/kg/day, atomoxetine showed a significant reduction of mean ADHD-RS scores at endpoint (ANOVA, p<0.001) (table II). Yet, the clinical significance of both studies is limited since efficacy was scored only in a social/familial setting and not in classroom conditions. In addition, intermediate results from baseline to endpoint were not presented in the publication. The multiple dose trial showed a significant reduction of the symptom score at the 1.2 and 1.8 mg/kg/day doses. The objective of the last study was to assess the efficacy of a single daily dose of atomoxetine versus placebo during a 6 week-treatment. Patients were evaluated by parents, investigators, as well as by teachers. The superiority of atomoxetine was demonstrated as compared to the placebo and the effect size of the daily dosing was similar to that reported with multiple doses. Preliminary data on ADHD patients presenting comorbidities showed that atomoxetine alone signi-ficantly reduced the symptom scores of anxiety and depression and similarly to atomoxetine associated with fluoxetine. In ADHD children with the oppositional defiant disorder, oppositional symptoms were reduced in the group receiving atomoxetine 1.8 mg/kg/day. Preliminary results in children with ADHD and chronic tics or Tourette syndrome showed a significant reduction of ADHD symptoms and a tendency to the decrease of tics. Tolerance and safety data pooled from the child and adolescent trials were acceptable. Study discontinuations due to adverse events in the four registration studies were only 2.8%. The most frequent adverse effects reported were gastrointestinal symptoms and decreased appetite. Weight loss reported early in clinical studies tended to stabilize during the open-label extension phases lasting up to 9 months. A retrospective comparison showed that the adverse event profile of poor metabolizers was similar to that of extensive metabolizers. In summary, data presented suggest that atomoxetine is a safe and effective drug for the treatment of ADHD in children and adolescents. Further studies are expected to accurately define the place of atomoxetine in the treatment strategy of ADHD, a chronic and invalidating disorder affecting 3 to 7% of school-aged children.
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PMID:[Atomoxetine: a new treatment for Attention Deficit/Hyperactivity Disorder (ADHD) in children and adolescents]. 1614 49

Depressed patients may exhibit reduced heart rate variability (HRV), and antidepressants which block norepinephrine uptake may also lower HRV. This study compared paroxetine (PAR) and venlafaxine XR (VEN-XR) on HRV. Outpatients were randomly assigned to double-blind treatment with PAR up to 40 mg or VEN-XR up to 225 mg daily. HRV measures of parasympathetic control consisted of change in R-R interval during forced 10-second breaths and respiratory sinus arrhythmia (RSA) during paced breathing. Ex vivo estimates of serotonin and norepinephrine transporter occupancy were obtained before and after treatment, as were measures of depression, anxiety, and resilience. Plasma drug concentrations were measured at end point. Forty-nine patients entered treatment; 44 of whom were evaluable (n = 22 per group). Significant within-group reductions were noted in R-R interval variation and in RSA after VEN-XR only. Between-group analyses showed significant group-by-time interaction, with greater reduction in R-R interval variation and in RSA for VEN-XR compared with PAR. Improvement in resiliency correlated significantly with norepinephrine transporter occupancy for VEN-XR. Further comparisons of selective serotonin reuptake inhibitor and serotonin and norepinephrine reuptake inhibitor drugs on HRV are warranted.
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PMID:Effects of paroxetine and venlafaxine XR on heart rate variability in depression. 1616 Jun 26

4-(4-Chlorophenyl)piperidine analogues each bearing a thioacetamide side chain appendage similar to that found in the wake-promoting drug modafinil have been synthesized. The transporter inhibitory activity of both the cis and trans isomers of these 3,4-disubstituted piperidines in both their (+)- and (-)-enantiomeric forms was determined. These studies reveal that the (-)-cis analogues exhibit dopamine transporter/norepinephrine transporter (DAT/NET) selectivity as was previously reported for the (+)-trans analogues. On the other hand, the (-)-trans and the (+)-cis isomers show serotonin transporter (SERT) or SERT/NET selectivity. Among them, (+)-cis-5b shows a low nanomolar Ki for the NET with 39-fold and 321-fold lower potency at the DAT and SERT, respectively, thus making it a useful pharmacological research tool for exploring NET-associated behavioral signatures. On the other hand, several of the compounds described herein, such as (+)-trans-5c, show comparable activity at all three transporters. Because broad-spectrum transporter inhibitors have been hypothesized to exhibit a more rapid onset of action and/or a greater efficacy as antidepressant agents than those selective for SERT or SERT + NET, some of the present compounds will be valuable to study in animal models of depression.
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PMID:Further structure-activity relationship studies of piperidine-based monoamine transporter inhibitors: effects of piperidine ring stereochemistry on potency. Identification of norepinephrine transporter selective ligands and broad-spectrum transporter inhibitors. 1633 21

The study of anxiety and fear involves complex interrelationships between psychiatry and the autonomic nervous system. Altered noradrenergic signaling is linked to certain types of depression and anxiety disorders, and treatment often includes specific transporter blockade. The norepinephrine transporter is crucial in limiting catecholaminergic signaling. Norepinephrine transporter-deficient mice have increased circulating catecholamines and elevated heart rate and blood pressure. We hypothesized, therefore, that reduced norepinephrine clearance would heighten the autonomic cardiovascular response to anxiety and fear. In separate experiments, norepinephrine transporter-deficient (norepinephrine transporter-/-) mice underwent tactile startle and trace fear conditioning to measure hemodynamic responses. A dramatic tachycardia was observed in norepinephrine transporter-/- mice compared with controls following both airpuff or footshock stimuli, and pressure changes were also greater. Interestingly, in contrast to normally elevated home cage levels in norepinephrine transporter-deficient mice, prestimulus heart rate and blood pressure were actually higher in norepinephrine transporter+/+ animals throughout behavioral testing. Upon placement in the behavioral chamber, norepinephrine transporter-deficient mice demonstrated a notable bradycardia and depressor effect that was more pronounced in females. Power spectral analysis indicated an increase in low frequency oscillations of heart rate variability; in mice, suggesting increased parasympathetic tone. Finally, norepinephrine transporter-/- mice exhibited sexual dimorphism in freeze behavior, which was greatest in females. Therefore, while reduced catecholamine clearance amplifies immediate cardiovascular responses to anxiety- or fear-inducing stimuli in norepinephrine transporter-/- mice, norepinephrine transporter deficiency apparently prevents protracted hemodynamic escalation in a fearful environment. Conceivably, chronic norepinephrine transporter blockade with transporter-specific drugs might attenuate recognition of autonomic and somatic distress signals in individuals with anxiety disorders, possibly lessening their behavioral reactivity, and reducing the cardiovascular risk factors associated with persistent emotional arousal.
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PMID:Norepinephrine transporter-deficient mice respond to anxiety producing and fearful environments with bradycardia and hypotension. 1651 44

The norepinephrine transporter (NET) terminates noradrenergic signalling by rapid re-uptake of neuronally released norepinephrine (NE) into presynaptic terminals. NET exerts a fine regulated control over NE-mediated behavioural and physiological effects including mood, depression, feeding behaviour, cognition, regulation of blood pressure and heart rate. NET is a target of several drugs which are therapeutically used in the treatment or diagnosis of disorders among which depression, attention-deficit hyperactivity disorder and feeding disturbances are the most common. Individual genetic variations in the gene encoding the human NET (hNET), located at chromosome 16q12.2, may contribute to the pathogenesis of those diseases. An increasing number of studies concerning the identification of single nucleotide polymorphisms in the hNET gene and their potential association with disease as well as the functional investigation of naturally occurring or induced amino acid variations in hNET have contributed to a better understanding of NET function, regulation and genetic contribution to disorders. This review will reflect the current knowledge in the field of NET from its initial discovery until now.
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PMID:The norepinephrine transporter in physiology and disease. 1672 47

The norepinephrine transporter (NET) is located in the plasma membrane of noradrenergic neurons, where it functions to take up synaptically released norepinephrine (NE). The NET thus serves as the primary mechanism for the inactivation of noradrenergic signaling. Some potent and selective or mixed NET inhibitors (e.g., reboxetine and atomoxetine) have been successfully developed to treat a variety of mental disorders such as depression and attention deficit hyperactivity disorder (ADHD). However, to date, only a very limited number of NET-selective inhibitors are available. New potent and selective NET inhibitors may find application in the treatment of mental disorders or in PET imaging, and may enhance our basic understanding of these illnesses. In the present review, both previously reported and newly designed NET inhibitors, as well as their therapeutic and imaging potential, will be discussed. Two types of molecules, the conformationally constrained tropanes and the piperidine-based nocaine/modafinil hybrid ligands, represent new leads and provide good opportunities for discovering novel potent and selective NET inhibitors that are useful as therapies and imaging agents for the NET.
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PMID:Norepinephrine transporter inhibitors and their therapeutic potential. 1687 20


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