Dibenamine enhancement of histamine-induced relaxation of the rabbit mesenteric artery.

Helically cut strips of rabbit mesenteric artery relax when exposed to histamine if their histamine H1 receptors are first blocked by 7 X 10(-6) M mepyramine. Relaxations are potentiated by 20 min pretreatment with 10(-6) M dibenamine. This dibenamine regimen also enhances relaxation of the strips to the selective H2 receptor agonist dimaprit, and to a lesser extent to papaverine which does not act on histamine receptors. This enhancement occurs both at 38 degrees and 22 degrees, and in mesenteric artery strips from rabbits reserpinized to deplete amine stores. Histamine has a greater relaxant effect on mesenteric artery strips at 22 degrees than at 38 degrees, normally. Dibenamine-treated strips do not relax more at the lower temperature, however. Thus, dibenamine nonselectively enhances relaxations of mesenteric artery and may enhance histamine-induced relaxations by an additional mechanism.