Electrochemical vaginal-oral potentials during the menstrual cycle in women

Electrochemical potentials were measured with non-polarizable salt electrodes (agar KCl-AgCL) during successive menstrual cycles in eight women. Four of them did not use any contraceptive, two were TCu users and the other two took oral contraceptives. Vaginal-tongue potentials presented biphasic cyclic changes. The vagina became positive in the middle of the menstrual cycle in all the women except those who were using contraceptive pills. Vaginal-oral potentials became positive (+) 24 hours after ingestion of oral contraceptives and up to 24 hours after discontinuation.