HISTAMINE CONTENT OF THE RAT UTERUS CONTAINING AN IUCD

Abstract

The contraceptive action of a foreign body in the uterus is still only partially understood, but a number of changes are known to be brought about by an IUCD. The decidual cell reaction is inhibited in the rat uterine horn con¬ taining an IUCD (Doyle & Margolis, 1964) and it has been suggested (Shel¬ esnyak, 1966; Marcus, 1964) that this inhibition may be due to a depletion of the histamine available for stimulation of the decidual response. This paper presents measurements of histamine in control and IUCD-containing uterine horns of the rat. Female rats of the Holtzmann strain were used. L0 designates the day spermatozoa were found in the vaginal smear. IUCDs, when present, con¬ sisted of about 1 cm of 3-0 surgical silk suture inserted with an atraumatic needle into one horn. Uterine histamine was extracted by the method of Code & Mclntyre (1956) and assayed on the guinea-pig ileum. For each measurement on whole uterine horns, five to eight horns were transected at the utero-tubal and utero-cervical junctions and pooled. In addition, some measurements were made on pools of anti-mesometrial tissue, obtained by cutting eight to twelve whole horns longitudinally with scissors into approximately two halves and using only the half opposite the mesometrium. In every case, the measurements on IUCDcontaining horns were compared with the measurements on the control horns from the same animals. The anti-histamine, diphenhydramine (Benadryl), at a concentration of 106 g/ml, completely abolished the contractile response to large doses of the uterine extract. The log dose-response curve was linear, and parallel lines were