ISSN:
1600-079X
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
Reyes-Vázquez C, Naranjo-Rodríguez EB, García-Segoviano JA, Trujillo-Santana J, Prieto-Gómez B. Apamin blocks the direct relaxant effect of melatonin on rat ileal smooth muscle. J. Pineal Res. 1997; 22:1–8. © Munksgaard, Copenhagen〈section xml:id="abs1-1"〉〈title type="main"〉AbstractThe 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 (KC1) depolarization. Under these conditions, melatonin produced a concentration-dependent inhibition of muscle contraction (mean inhibitory concentration, IC50: 17.3 times 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 times 10-9 M), a K+-channel blocker. By contrast, other K+-channel blockers such as 4-aminopyridine (lf-4M to 5 times 10-3 M), tetraethylammonium (10-4 M to 10-1 M), and glibenclamide (10-5 M) were ineffective. Additionally, the Ca2+-channel antagonists nitrendipine (IC50: 2.4 times 10-9 M) and verapamil (IC50: 1.1 times 10-7 M) also blocked the inhibitory action of melatonin. These results suggest that melatonin may interact with an apamin-sensitive, possibly Ca2+-activated, K+ channel and thus cause an inhibition of ileal smooth muscle contractions.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1600-079X.1997.tb00295.x
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