Different roles of histamine receptor subtypes in ampullar & isthmic segments of human fallopian tube.

We have studied the influence of both menstrual cycle phase and subtype-selective histamine antagonists on the contractions produced by histamine isolated in human fallopian tubes. Histamine produced tonic contractions of the isolated preparations of both the ampullar and isthmic segments of the human fallopian tube were analyzed. The effects of both histamine and its antagonists were not dependent on the phase of the menstrual cycle. The isolated preparations of the ampullar segment from post menopausal patients were not responsive on histamine. When responding, the ampullar segments were slightly more sensitive to histamine than the isthmic segments. All three subtype selective histamine antagonists (pyrilamine, cimetidine and thioperamide) produced strong inhibition of histamine evoked contractions of the ampullar segment. On the other hand, only pyrilamine strongly inhibited histamine evoked contractions of the isthmic segment. The results of our study suggest that only H1 receptors were responsible for the histamine contractile effect on the isthmic segment and that all three subtypes of histamine receptors were involved in the effect of histamine on the ampullar segment of human fallopian tube.