Inhibitory effect of the plant flavonoid galangin on rat vas deferens in vitro.

Flavonoids are phenolic compounds that are widely distributed in higher plants and therefore are ingested by humans and animals with their regular foods, but also have various pharmacological properties. In the present study we have investigated the effect of galangin, a member of the flavonol class, on the contractile response elicited by electrical field stimulation (EFS) in the rat isolated vas deferens. Galangin (10(-8)-3 x 10(-4) M) produced a concentration- dependent inhibition of the EFS-evoked contractile response, with only a minimal inhibitory effect on phenylephrine-induced contractions. The inhibitory effect of galangin was unaffected by atropine (10(-6) M) plus hexamethonium (10(-4) M), a combination of the NK(1) receptor antagonist SR 140333 (10(-7) M), the NK(2) receptor antagonist SR 48968 (10(-6) M) and the NK(3) receptor antagonist SR 142801 (10(-7) M), L-NAME (3 x 10(-4) M), naloxone (10(-6) M) or yohimbine (10(-7) M). However, the vanilloid receptor antagonist capsazepine (10(-5) M) significantly reduced the inhibitory effect of galangin. It is concluded that the galangin inhibits excitatory transmission of the rat vas deferens with a mechanism involving, at least in part, vanilloid receptors.