RESUMO
Some recently published in vitro studies with two metabotropic glutamate 2/3 receptor (mGluR(2/3)) agonists [(-)-2-oxa-4-aminobicyclo[3.1.0] hexane-4,6-dicarboxylic acid (LY379268) and 1S,2S,5R,6S-2-aminobicyclo[3.1.0]hexane-2,6-bicaroxylate monohydrate (LY354740)] suggest that these compounds may also directly interact with dopamine (DA) D(2) receptors. The current in vitro and in vivo studies were undertaken to further explore this potential interaction with D(2) receptors. LY379268 and LY354740 failed to inhibit D(2) binding in both native striatal tissue homogenates and cloned receptors at concentrations up to 10 microM. LY379268 and LY354740 (up to 10 microM) also failed to stimulate [(35)S]GTPgammaS binding in D(2L)- and D(2S)-expressing clones in the presence of NaCl or N-methyl-d-glucamine. In an in vivo striatal D(2) receptor occupancy assay, LY379268 (3-30 mg/kg) or LY354740 (1-10 mg/kg) failed to displace raclopride (3 microg/kg i.v.), whereas aripiprazole (10-60 mg/kg) showed up to 90% striatal D(2) receptor occupancy. LY379268 (10 mg/kg) and raclopride (3 mg/kg) blocked d-amphetamine and phencyclidine (PCP)-induced hyperactivity in wild-type mice. However, the effects of LY379268 were lost in mGlu(2/3) receptor knockout mice. In DA D(2) receptor-deficient mice, LY379268 but not raclopride blocked both PCP and d-amphetamine-evoked hyperactivity. In the striatum and nucleus accumbens, LY379268 (3 and 10 mg/kg) was without effect on the DA synthesis rate in reserpinized rats and also failed to prevent S-(-)-3-(3-hydroxyphenyl)-N-propylpiperidine-induced reductions in DA synthesis rate. Taken together, the current data fail to show evidence of direct DA D(2) receptor interactions of LY379268 and LY354740 in vitro or in vivo. Instead, these results provide further evidence for a novel antipsychotic mechanism of action for mGluR(2/3) agonists.
Assuntos
Aminoácidos/farmacologia , Compostos Bicíclicos Heterocíclicos com Pontes/farmacologia , Compostos Bicíclicos com Pontes/farmacologia , Membrana Celular/efeitos dos fármacos , Receptores de Dopamina D2/metabolismo , Receptores de Glutamato Metabotrópico/agonistas , Animais , Ligação Competitiva , Células CHO , Membrana Celular/metabolismo , Cricetinae , Cricetulus , Domperidona/farmacologia , Dopamina/biossíntese , Antagonistas dos Receptores de Dopamina D2 , Feminino , Humanos , Masculino , Camundongos , Camundongos Knockout , Atividade Motora/efeitos dos fármacos , Ligação Proteica , Racloprida/farmacologia , Ensaio Radioligante , Ratos , Ratos Sprague-Dawley , Receptores de Dopamina D2/agonistas , Receptores de Dopamina D2/genética , TransfecçãoRESUMO
The selective serotonin reuptake inhibitor fluoxetine consists of equal amounts of R and S stereoisomers. In this study, we investigated the pharmacologic properties of the stereoisomers using transporter and receptor binding assays and in vivo microdialysis in freely moving rats. Binding to the transporter confirmed selectivity of R- and S-fluoxetine for the 5-HT transporter versus the dopamine (DA) and norepinephrine (NE) human transporters. Receptor binding studies demonstrated significant affinity of R-fluoxetine, but not S-fluoxetine, for human 5-HT(2A) and 5-HT(2C) receptor subtypes. Functional GTPgammaS binding studies indicated that R-fluoxetine is an antagonist at 5-HT(2A) and 5-HT(2C) receptors. In microdialysis studies, acute R- and S-fluoxetine increased extracellular levels of 5-HT, DA, and NE in prefrontal cortex (PFC), but R-fluoxetine caused significantly greater increases of catecholamines. R-fluoxetine increased extracellular levels of 5-HT and NE in PFC, nucleus accumbens, and hypothalamus, whereas it increased dopamine in PFC and hypothalamus, but not in DA-rich nucleus accumbens and striatum, thus indicating a regionally selective effect. The unexpected increases of extracellular catecholamines by a selective 5-HT uptake inhibitor like R-fluoxetine may be due to its antagonism of 5-HT(2C) receptors.
Assuntos
Dopamina/biossíntese , Fluoxetina/farmacologia , Hipotálamo/efeitos dos fármacos , Norepinefrina/biossíntese , Córtex Pré-Frontal/efeitos dos fármacos , Serotonina/biossíntese , Animais , Cães , Relação Dose-Resposta a Droga , Espaço Extracelular/efeitos dos fármacos , Espaço Extracelular/metabolismo , Humanos , Hipotálamo/metabolismo , Masculino , Microdiálise/métodos , Córtex Pré-Frontal/metabolismo , Ligação Proteica/efeitos dos fármacos , Ligação Proteica/fisiologia , Ratos , Ratos Sprague-Dawley , Receptores de Serotonina/metabolismo , EstereoisomerismoRESUMO
The selective norepinephrine (NE) transporter inhibitor atomoxetine (formerly called tomoxetine or LY139603) has been shown to alleviate symptoms in Attention Deficit/Hyperactivity Disorder (ADHD). We investigated the mechanism of action of atomoxetine in ADHD by evaluating the interaction of atomoxetine with monoamine transporters, the effects on extracellular levels of monoamines, and the expression of the neuronal activity marker Fos in brain regions. Atomoxetine inhibited binding of radioligands to clonal cell lines transfected with human NE, serotonin (5-HT) and dopamine (DA) transporters with dissociation constants (K(i)) values of 5, 77 and 1451 nM, respectively, demonstrating selectivity for NE transporters. In microdialysis studies, atomoxetine increased extracellular (EX) levels of NE in prefrontal cortex (PFC) 3-fold, but did not alter 5-HT(EX) levels. Atomoxetine also increased DA(EX) concentrations in PFC 3-fold, but did not alter DA(EX) in striatum or nucleus accumbens. In contrast, the psychostimulant methylphenidate, which is used in ADHD therapy, increased NE(EX) and DA(EX) equally in PFC, but also increased DA(EX) in the striatum and nucleus accumbens to the same level. The expression of the neuronal activity marker Fos was increased 3.7-fold in PFC by atomoxetine administration, but was not increased in the striatum or nucleus accumbens, consistent with the regional distribution of increased DA(EX). We hypothesize that the atomoxetine-induced increase of catecholamines in PFC, a region involved in attention and memory, mediates the therapeutic effects of atomoxetine in ADHD. In contrast to methylphenidate, atomoxetine did not increase DA in striatum or nucleus accumbens, suggesting it would not have motoric or drug abuse liabilities.
Assuntos
Transtorno do Deficit de Atenção com Hiperatividade/metabolismo , Dopamina/metabolismo , Norepinefrina/metabolismo , Córtex Pré-Frontal/efeitos dos fármacos , Propilaminas/farmacologia , Animais , Cloridrato de Atomoxetina , Transtorno do Deficit de Atenção com Hiperatividade/tratamento farmacológico , Sinergismo Farmacológico , Humanos , Masculino , Córtex Pré-Frontal/metabolismo , Ratos , Ratos Sprague-DawleyRESUMO
Compounds that block both serotonin (5-HT) and norepinephrine (NE) transporters have been proposed to have improved antidepressant efficacy. We compared the ability of four dual transporter inhibitors-chlorimipramine, duloxetine, milnacipran and venlafaxine-to block monoamine transporters in vitro and in vivo and increase extracellular monoamines in rat brain. Inhibition of radioligand binding to clonal human monoamine transporters in vitro and in vivo in rats was determined. Extracellular concentrations of 5-HT and NE in rat prefrontal cortex (PFC) were quantified using the microdialysis technique. All compounds blocked binding to human 5-HT and NE transporters, although chlorimipramine and venlafaxine had markedly greater affinity for 5-HT than NE transporters. In vivo, chlorimipramine and duloxetine potently blocked both transporters, milnacipran blocked both with lower potency and venlafaxine only blocked the 5-HT transporter. Chlorimipramine and duloxetine increased robustly and approximately equally monoamine extracellular concentrations. Milnacipran produced only small increases in NE, whereas venlafaxine increased 5-HT markedly at the lower doses and both monoamines at high doses. Thus, the dual transporter inhibitors blocked 5-HT and NE transporters in vitro and in vivo with varying potency. Chlorimipramine, duloxetine, and high dose venlafaxine acted as dual transporter inhibitors in rat PFC and increased extracellular concentrations of the monoamines, indicating functional dual transporter inhibition.
Assuntos
Inibidores da Captação Adrenérgica/farmacologia , Monoaminas Biogênicas/metabolismo , Proteínas de Transporte/metabolismo , Espaço Extracelular/metabolismo , Inibidores Seletivos de Recaptação de Serotonina/farmacologia , Animais , Química Encefálica/efeitos dos fármacos , Clomipramina/farmacologia , Cicloexanóis/farmacologia , Ciclopropanos/farmacologia , Relação Dose-Resposta a Droga , Cloridrato de Duloxetina , Técnicas In Vitro , Masculino , Microdiálise , Milnaciprano , Norepinefrina/metabolismo , Córtex Pré-Frontal/efeitos dos fármacos , Córtex Pré-Frontal/metabolismo , Ensaio Radioligante , Ratos , Ratos Sprague-Dawley , Serotonina/metabolismo , Serotoninérgicos/farmacologia , Tiofenos/farmacologia , Cloridrato de Venlafaxina , alfa-Metiltirosina/farmacologia , p-Cloroanfetamina/farmacologiaRESUMO
A series of 1-aryloxy-3-piperidinylpropan-2-ols possessing potent dual 5-HT1A receptor antagonism and serotonin reuptake inhibition was discovered. 1-(1H-Indol-4-yloxy)-3-(4-benzo[b]thiophen-2-ylpiperidinyl)propan-2-ols exhibited selective and high affinities at the 5-HT1A receptor and serotonin reuptake site in vitro. In vivo evaluation of this series of compounds demonstrated elevated extracellular serotonin levels from the basal and quick recovery of neuron firing that was presumably suppressed by the initial acute activation of 5-HT1A somatodendritic autoreceptors.
Assuntos
Antidepressivos/farmacologia , Piperidinas/farmacologia , Propanóis/farmacologia , Inibidores Seletivos de Recaptação de Serotonina/farmacologia , Antagonistas do Receptor 5-HT1 de Serotonina , Animais , Antidepressivos/administração & dosagem , Antidepressivos/química , Encéfalo/efeitos dos fármacos , Avaliação Pré-Clínica de Medicamentos , Técnicas In Vitro , Masculino , Conformação Molecular , Piperidinas/administração & dosagem , Piperidinas/química , Propanóis/administração & dosagem , Propanóis/química , Ratos , Ratos Sprague-Dawley , Inibidores Seletivos de Recaptação de Serotonina/administração & dosagem , Inibidores Seletivos de Recaptação de Serotonina/química , Estereoisomerismo , Relação Estrutura-AtividadeRESUMO
A series of 1-(1H-indol-4-yloxy)-3-(4-arylpiperidinyl)propan-2-ols possessing potent dual 5-HT(1A) receptor antagonism and serotonin reuptake inhibition was discovered. The fused aryl ring moiety contributed to the robust dual activities irrespective of the regiochemistry associated with its connectivity to the piperidine central ring.
Assuntos
Antidepressivos de Segunda Geração/síntese química , Propanóis/farmacologia , Inibidores Seletivos de Recaptação de Serotonina/síntese química , Antagonistas do Receptor 5-HT1 de Serotonina , Antidepressivos de Segunda Geração/farmacologia , Compostos Heterocíclicos de 4 ou mais Anéis/síntese química , Compostos Heterocíclicos de 4 ou mais Anéis/farmacologia , Propanóis/síntese química , Ligação Proteica , Inibidores Seletivos de Recaptação de Serotonina/farmacologia , Estereoisomerismo , Relação Estrutura-AtividadeRESUMO
A series of 1-aryloxy-3-piperidinylpropan-2-ols possessing potent dual 5-HT(1A) receptor antagonism and serotonin reuptake inhibition was discovered. 1-(1H-Indol-4-yloxy)-3-(4-benzo[b]thiophen-2-ylpiperidinyl)propan-2-ols exhibited selective and high affinity at the 5-HT(1A) receptor and serotonin reuptake inhibition at nanomolar concentrations for dual activities.
Assuntos
Antidepressivos de Segunda Geração/química , Antidepressivos de Segunda Geração/farmacologia , Propanóis/química , Propanóis/farmacologia , Inibidores Seletivos de Recaptação de Serotonina/farmacologia , Antagonistas do Receptor 5-HT1 de Serotonina , Antidepressivos de Segunda Geração/síntese química , Guanosina 5'-O-(3-Tiotrifosfato)/metabolismo , Indóis/química , Indóis/farmacologia , Paroxetina/farmacologia , Propanóis/síntese química , Receptor 5-HT1A de Serotonina/metabolismo , Inibidores Seletivos de Recaptação de Serotonina/síntese química , Inibidores Seletivos de Recaptação de Serotonina/química , Relação Estrutura-AtividadeRESUMO
Potent 5-HT1A/SSRIs at low nanomolar and subnanomolar concentrations were identified in a series of 1-(1H-indol-4-yloxy)-3-(4-benzo[b]thiophen-2-ylpiperidinyl)propan-2-ols. Incorporation of an alpha-Me group in the piperidine ring with its specific stereochemistry enhanced binding affinity at the 5-HT reuptake site and in vitro 5-HT(1A) antagonist functional activity.
Assuntos
Piperidinas/síntese química , Piperidinas/farmacologia , Propanóis/síntese química , Propanóis/farmacologia , Receptor 5-HT1A de Serotonina/efeitos dos fármacos , Inibidores Seletivos de Recaptação de Serotonina/síntese química , Inibidores Seletivos de Recaptação de Serotonina/farmacologia , Antagonistas da Serotonina/síntese química , Antagonistas da Serotonina/farmacologia , Guanosina 5'-O-(3-Tiotrifosfato)/metabolismo , Indicadores e Reagentes , Paroxetina/farmacologia , Estereoisomerismo , Relação Estrutura-AtividadeRESUMO
A series of 1-aryloxy-3-piperidinylpropan-2-ols possessing potent dual 5-HT(1A) receptor antagonism and serotonin reuptake inhibition was discovered. Modification of potential metabolic sites of 1-(1H-indol-4-yloxy)-3-(4-benzo[b]thiophen-2-ylpiperidinyl)propan-2-ols further improved the in vitro binding affinities and functional antagonism.