Abstract
The inhibitory effects of various ergot alkaloids on pseudopregnancy (1), decidualization (2), early pregnancy (3), and lactation (4) in the rat have been well documented by several investigators. In general, these effects were attributed to a specific inhibition of prolactin secretion, as prolactin was shown to partially reverse the effects of ergocornine (1), and plasma prolactin levels decreased after treatment with the drug (5). Recently, Wuttke et al. (9) reported a significant decrease in the plasma LH levels in rats also treated with 50 or 200 μg of ergocornine (5). The present study was undertaken to examine the effects of one of the ergot alkaloids, ergotamine tartrate, on ovulation, estrus, and LH secretion in adult cycling rats.
Materials and Methods. Adult female Charles River rats weighing 180-210 g were used in the present experiments. The animals were housed in rooms with constant temperature and a 14-hr light (5 AM to 7 PM EST) and 10-hr darkness schedule. The estrous cycle was checked by daily vaginal smears, and only animals exhibiting two consecutive cycles of 4 days were used in the study.
Ergotamine tartrate (Sigma Chemical Co.) was administered intraperitoneally as a suspension in 0.9% saline at 12:30 PM on the day of proestrus. Control rats received saline at this time. Blood samples were obtained under light ether anesthesia between 5:30 and 6 PM on the day of proestrus, as well as at 11 AM on the day of estrus. Luteinizing hormone, when given, was injected intraperitoneally at 4 PM during proestrus. One group of treated animals was subjected to mechanical stimulation of cervix at 6:30 PM on the day of proestrus.
All the animals were autopsied between 11 AM and 12 noon on the day of estrus.
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