d-6-Methyl-8-cyanomethylergoline (I) (compound 6605 VÚFB) prevents pregnancy in rats when given orally up to the 7th day after copulation (Řežábek, Semonský & Kucharczyk, 1969). A similar effect was seen with the chemically related compounds, ergocristine, ergocryptine, ergocornine, ergosine and ergovaline (Shelesnyak, 1957; Kraicer & Shelesnyak, 1965). All the evidence shows that these drugs interfere with the secretion of hypophysial luteotrophic hormone (lih), which is necessary for the correct function of corpora lutea (Shelesnyak, 1957; Zeilmaker & Carlsen, 1962; Lindner & Shelesnyak, 1967). Moreover, Lobel, Shelesnyak & Tic (1966) observed histological changes in the ovary associated with a drop in the levels of lth and a rise in fsh and lh after ergocornine. This indicated that ergocornine might have a direct or indirect influence on the secretion of hypophysial gonadotrophins.
Since the action of compound 6605 VÚFB on pregnancy appears to resemble that of ergocornine, we decided to study the effects of the compound on the increase in the secretion of gonadotrophins which takes place after unilateral ovariectomy in rats. (Peterson, Edgren & Jones, 1964; Benson, Sorrentino & Evans, 1969). We also considered the possible interaction of compound 6605 VÚFB with methallibure (ICI 33828), which is known to inhibit gonadotrophin secretion (Paget, Walpole & Richardson, 1961).