Failure of Nicotine to Alter the Estrus Cycle in the White Rat.

Ten white female rats of the Wistar strain were injected twice daily with nicotine hydrochloride in a dose of 2 to 3 mg. per kg. in 1 to 1,000 solution. This amount was sufficient to produce convulsions of varying degree, usually becoming less as the experiment progressed. Injections were begun at the age of 2 to 4 weeks, and an equal number of litter mates were injected with equal volumes of 0.85% NaCl solution as controls. Beginning at the age of 3 months in one set of 7 nicotine and 7 control rats, and at 5 months in a set of 3 nicotine and 3 control rats, vaginal smears were examined daily, between 4:30 P. M. and 6:00 P. M., for a period of approximately 3 months. During the course of the experiment, one of the control group was accidentally killed, and another became pregnant, and could not supply data for the test for the period of pregnancy, and until estrus began again after taking away the young. These accidents account for the discrepancy between the total rat days of nicotine and control groups. Comparison of the 2 groups of rats was made by 2 methods, as follows:

Method I. A value of 2 was assigned to each day of complete cornification of the vaginal epithelium, as indicated by the smear, and a value of 1 to each day upon which the smears contained nucleated epithelium (non-cornified) but no leucocytes. The total value for estrus days for the nicotine group was 659 and for the controls, 635. The total rat days for the nicotine group was 1242, and for the controls. 1118. By dividing the value of the estrus days by the total rat days, the “estrus index” may be obtained.