IN-VITRO PROLACTIN BUT NOT LH AND FSH RELEASE IS INHIBITED BY COMPOUNDS IN EXTRACTS OF AGNUS-CASTUS - DIRECT EVIDENCE FOR A DOPAMINERGIC PRINCIPLE BY THE DOPAMINE-RECEPTOR ASSAY

Women suffering from premenstrual mastodynia often respond to stimuli of prolactin (Pr1) release with a hypersecretion of this hormone. Pharmacological reduction of Pr1 release by dopamine agonists or treatment with extracts of Agnus castus (AC) improve the clinical situation of patients with such premenstrual symptoms. Extracts of AC contain compounds which inhibit in vivo Pr1 release in women as well as in vitro from dispersed rat pituitary cells. It is yet unknown whether this inhibitory action of AC is only exerted on Pr1 release or whether release of other pituitary hormones like LH and FSH is also affected. The effects of AC on LH and FSH release were examined in vitro using rat pituitary cell cultures. To rule out that the Pr1-inhibiting properties of AC are at least in part due to a cytotoxic component, pituitary cell cultures were subjected to the MTT test. To assess whether the Pr1 inhibitory effect of AC preparations is due to compounds acting as dopamine (DA) agonists, we used the corpus striatum membrane DA receptor binding assay. Our results demonstrate for the first time that AC extract contains an active principle that binds to the D-2 receptor. Thus, it is very likely that it is this dopaminergic principle which inhibits Pr1 release in vitro from rat pituitary cells. Furthermore we give evidence for the specificity of action of AC on hormone release, since gonadotropin secretion remained unaffected. The findings of the present study support the therapeutical usefulness of AC extracts for treatment of premenstrual mastodynia which is associated with hypersecretion of Pr1. Furthermore, the beneficial effects of AC appear to be due to the inhibition of pituitary Pr1 release.