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J Pharmacol Exp Ther ; 334(2): 545-55, 2010 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-20439438

RESUMO

Voltage-gated calcium channel (Ca(v))2.2 (N-type calcium channels) are key components in nociceptive transmission pathways. Ziconotide, a state-independent peptide inhibitor of Ca(v)2.2 channels, is efficacious in treating refractory pain but exhibits a narrow therapeutic window and must be administered intrathecally. We have discovered an N-triazole oxindole, (3R)-5-(3-chloro-4-fluorophenyl)-3-methyl-3-(pyrimidin-5-ylmethyl)-1-(1H-1,2,4-triazol-3-yl)-1,3-dihydro-2H-indol-2-one (TROX-1), as a small-molecule, state-dependent blocker of Ca(v)2 channels, and we investigated the therapeutic advantages of this compound for analgesia. TROX-1 preferentially inhibited potassium-triggered calcium influx through recombinant Ca(v)2.2 channels under depolarized conditions (IC(50) = 0.27 microM) compared with hyperpolarized conditions (IC(50) > 20 microM). In rat dorsal root ganglion (DRG) neurons, TROX-1 inhibited omega-conotoxin GVIA-sensitive calcium currents (Ca(v)2.2 channel currents), with greater potency under depolarized conditions (IC(50) = 0.4 microM) than under hyperpolarized conditions (IC(50) = 2.6 microM), indicating state-dependent Ca(v)2.2 channel block of native as well as recombinant channels. TROX-1 fully blocked calcium influx mediated by a mixture of Ca(v)2 channels in calcium imaging experiments in rat DRG neurons, indicating additional block of all Ca(v)2 family channels. TROX-1 reversed inflammatory-induced hyperalgesia with maximal effects equivalent to nonsteroidal anti-inflammatory drugs, and it reversed nerve injury-induced allodynia to the same extent as pregabalin and duloxetine. In contrast, no significant reversal of hyperalgesia was observed in Ca(v)2.2 gene-deleted mice. Mild impairment of motor function in the Rotarod test and cardiovascular functions were observed at 20- to 40-fold higher plasma concentrations than required for analgesic activities. TROX-1 demonstrates that an orally available state-dependent Ca(v)2 channel blocker may achieve a therapeutic window suitable for the treatment of chronic pain.


Assuntos
Analgésicos/farmacologia , Bloqueadores dos Canais de Cálcio/farmacologia , Canais de Cálcio Tipo N/fisiologia , Indóis/farmacologia , Triazóis/farmacologia , Analgésicos/efeitos adversos , Analgésicos/farmacocinética , Animais , Barorreflexo/efeitos dos fármacos , Disponibilidade Biológica , Bloqueadores dos Canais de Cálcio/efeitos adversos , Bloqueadores dos Canais de Cálcio/farmacocinética , Canais de Cálcio Tipo N/genética , Canais de Cálcio Tipo R/fisiologia , Proteínas de Transporte de Cátions/fisiologia , Linhagem Celular , Cães , Gânglios Espinais/efeitos dos fármacos , Gânglios Espinais/fisiologia , Hiperalgesia/tratamento farmacológico , Hipotensão Ortostática/induzido quimicamente , Indóis/efeitos adversos , Indóis/farmacocinética , Masculino , Camundongos , Camundongos Knockout , Neurônios/efeitos dos fármacos , Neurônios/fisiologia , Dor/tratamento farmacológico , Dor/etiologia , Técnicas de Patch-Clamp , Ratos , Ratos Sprague-Dawley , Triazóis/efeitos adversos , Triazóis/farmacocinética
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