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Apamin blocks the direct relaxant effect of melatonin on rat ileal smooth muscle.
Reyes-Vázquez, C; Naranjo-Rodríguez, E B; García-Segoviano, J A; Trujillo-Santana, J T; Prieto-Gómez, B.
Afiliação
  • Reyes-Vázquez C; Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de México, México, D.F.
J Pineal Res ; 22(1): 1-8, 1997 Jan.
Article em En | MEDLINE | ID: mdl-9062863
The present study investigated the mechanisms of melatonin-induced inhibition of the ileal smooth muscle contraction. Rat isolated ileal smooth muscle strips were stimulated in an organ bath using carbachol (CAR) or potassium chloride (KCl) depolarization. Under these conditions, melatonin produced a concentration-dependent inhibition of muscle contraction (mean inhibitory concentration, IC50: 17.3 x 10(-6) M), which was not blocked by either tetrodotoxin (10(-6) M), hexamethonium (10(-4) M), or phentolamine (10(-6) M). The inhibitory effect of melatonin during CAR stimulation was blocked in a concentration-dependent manner by the presence of apamin (4.8 x 10(-9) M), a K(+)-channel blocker. By contrast, other K(+)-channel blockers such as 4-aminopyridine (10(-4) M to 5 x 10(-3) M), tetraethylammonium (10(-4) to 10(-1) M), and glibenclamide (10(-5) M) were ineffective. Additionally, the Ca(2+)-channel antagonists nitrendipine (IC50: 2.4 x 10(-9) M) and verapamil (IC50: 1.1 x 10(-7) M) also blocked the inhibitory action of melatonin. These results suggest that melatonin may interact with an apamin-sensitive, possibly Ca(2+)-activated, K+ channel and thus cause an inhibition of ileal smooth muscle contractions.
Assuntos
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Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Apamina / Íleo / Melatonina / Fármacos Neuromusculares Despolarizantes Limite: Animals / Humans / Male Idioma: En Revista: J Pineal Res Assunto da revista: ENDOCRINOLOGIA Ano de publicação: 1997 Tipo de documento: Article País de publicação: Reino Unido
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Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Apamina / Íleo / Melatonina / Fármacos Neuromusculares Despolarizantes Limite: Animals / Humans / Male Idioma: En Revista: J Pineal Res Assunto da revista: ENDOCRINOLOGIA Ano de publicação: 1997 Tipo de documento: Article País de publicação: Reino Unido