Apamin blocks the direct relaxant effect of melatonin on rat ileal smooth muscle
Por:
Reyes-Vázquez C., Naranjo-Rodríguez E.B., García-Segoviano J.A., Trujillo-Santana J., Prieto-Gómez B.
Publicada:
1 ene 1997
Resumen:
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, IC 50: 17.3 × 10 -6 M), which was not blocked by either tetrodotoxin (10 -6 M), hexamethonium (10 -4M), or phentolamine (10 -6M). The inhibitory effect of melatonin during CAR stimulation was blocked in a concentration-dependent manner by the presence of apamin (4.8 × 10 -9 M), a K +-channel blocker. By contrast, other K +-channel blockers such as 4-aminopyridine (10 -4M to 5 × 10 -3 M), tetraethylammonium (10 -4 M to 10 -1 M), and glibenclamide (10 -5 M) were ineffective. Additionally, the Ca 2+-channel antagonists nitrendipine (IC 50: 2.4 × 10 -9 M) and verapamil (IC 50: 1.1 × 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. © Munksgaard.
Filiaciones:
Reyes-Vázquez C.:
Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico
Departamento de Fisiología, Facultad de Medicina, División de Investigación, Apartado Postal 70-250, México, 04510, D.F., Mexico
Naranjo-Rodríguez E.B.:
Sección de Farmacología, Departamento de Farmacia, Universidad Nacional Autónoma de México, Mexico
García-Segoviano J.A.:
Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico
Trujillo-Santana J.:
Departamento de Anatomía, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico
Prieto-Gómez B.:
Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico
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