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Induction of Pseudopregnancy in the Rat with No Rise in Serum Prolactin

1972; Oxford University Press; Volume: 90; Issue: 2 Linguagem: Inglês

10.1210/endo-90-2-438

1945-7170

W. Wuttke, J. Meites,

Growth Hormone and Insulin-like Growth Factors

Ergocornine (EC) was injected in a dose of 50 ug/100 g BW into cycling female rats on the afternoon of the last day of diestrus, on the following morning and afternoon of proestrus and on the morning of estrus, to prevent any rise in serum prolactin. Control rats were given the injection vehicle only. The uterine cervix of EC-treated and control rats was stimulated by a glass rod on the morning of estrus to induce pseudopregnancy. In the control rats, serum prolactin values fell by 1.5 hr but rose significantly at 5.5 and 7.5 hr after cervical stimulation and remained elevated for the next 2 days of pseudopregnancy. In another group of control rats, serum prolactin was elevated for the first 3 days of pseudopregnancy and then declined to levels as low or even lower than in cycling rats on the days of diestrus. In EC-injected rats, there was no rise in serum prolactin levels after cervical stimulation. Serum LH values increased significantly by 10 min and remained elevated for 5.5 hr after cervical stimulation in both EC-injected and control rats, but none of the treatments altered serum FSH levels. The average length of pseudopregnancy in the control rats was 14.3 ± 0.3 days, and 10.7 ± 0.2 days in the EC-injected rats. These results suggest that pseudopregnancy in rats can be induced by mechanical stimulation of the uterine cervix in the presence of minimal levels of serum prolactin and a rise in serum LH. A possible reduction in luteolytic activity by prolactin as a result of its depressed release by ergocornine also may contribute to the pseudopregnancy observed in these animals. (Endocrinology90: 438, 1972)