[Miosis induced by histamine injected into the anterior chamber of isolated pig eyes].
Miotic effects were shown when the histamine (0.1 nM, 10 microL) was injected into the anterior chamber of isolated pig eyes. This miosis was camparable to that by acetylcholine (0.1 nM) or pilocarpine (0.01 M). The miotic effect induced concentration dependently by histamine was inhibited by pretreatment with H1 receptor antagonist chlorpheniramine (1 microM, 10 microL), but not by H2 receptor antagonist cimetidine (1 microM, 10 microL). H2 receptor agonist dimaprit (1 mM, 10 microL) caused no change of pupil diameter. The results suggest that histamine induces miotic effects via H1 receptor in isolated pig eyes.