The alkaloid yohimbine has long been considered in scientific and folk useage to have both aphrodisiac and genital stimulating qualities. Yet, to our knowledge, no controlled observational studies of its effect on copulatory behavior have been reported.
Males of two castrated and two intact groups of adult Sprague-Dawley rats were observed individually with an estrus female during five weekly standardized tests of sexual behavior. One castrate and one intact group received yohimbine HCL subcutaneously, 20 mg/kg body weight for 10 days, and then 10mg/kg for the following 25 days. The two remaining groups served as controls and received only the injection vehicle.
When the behaviour of the animals treated with yohimbine was compared with that of their respective controls no significant differences in the latencies to mounting, intromission, or ejaculation, or in the frequencies of these components were observed. Gross morphological studies revealed no significant differences in total body weight, weights of the ventral prostate, seminal vesicles, or pituitary. Hyperemia of the genito-urinary system was not evident. The weights of the testes were depressed in the yohimbine treated animals when compared to the controls.
In the male rat direct observation has failed to confirm previous reports of the aphrodisiac qualities of yohimbine. Further, morphological evident for the stimulating effect of yohimbine was not found.