Anterior pituitary-stimulating action of yohimbine

Abstract

1. Immature female rats treated with i-mg. doses of yohimbine-HCl show no precocious sexual development. 2. Female rats treated with this drug for periods ranging from 40 to 101 days with dosages ranging from 1 to 4 mg. per day, responded to lower dosages (1 and 1 mg.) with periods of prolonged estrus while with higher dosages (3 and 4 mg.) a condition resembling pseudopregnancy resulted. These animals exhibited atypical sexual behavior during periods of heat. 3. Adult castrated female rats showed no cornification of the vaginal epithelium in spite of chronic administration of the drug, showing that the prolonged estrus observed in normal rats was not due to hyperemia. 4. Hypophysectomised female rats showed no estrous condition when treated with yohimbine, demonstrating that the drug had no direct effect upon ovarian tissue. 5. Adult normal and castrated male rats with immature ovaries devoid of corpora lutea implanted into the anterior chamber of the eye showed on treatment with yohimbine, the development of normal appearing corpora. 6. The results reported in this investigation present evidence that the alkaloid yohimbine stimulates the anterior lobe of the pituitary causing it to release excessive amounts of its principles, especially the luteinizing hormone. © 1942 by The Endocrine Society.