ABSTRACT
Reserpine has proved to be a drug of extreme value in pharmacological research, mainly because of its ability to deplete tissue stores of amines. Yohimbine is a related drug and has not been as intensively investigated. In this study yohimbine was shown to deplete uterine muscle of catecholamines in vitro, but also to have a marked alpha-adrenergic blocking action on suitable test preparations. It was shown to inhibit contractions of the isolated rat uterus and evidence f is presented to indicate that this is a consequence of the release of catecholamines. An antagonistic action of yohimbine to the stimulating effects of 5-HT on the rat I uterus was observed. Traditionally yohimbine has been claimed to possess aphrodisiac properties and in the present study its effects on the reproductive system of the female mouse and rat were investigated. The oestrous cycle was prolonged and ovulation was suppressed. It is suggested that yohimbine exerts its effects on the reproductive tract mainly via action on the brain, but that part of Its action may be due to a marked increase in vascularity of the sex organs.