[Abortifacient activity of caffeic acid and its antiprogestational action in early pregnant mice].
Fourteen out of fifteen 6-d pregnant mice were found aborted after ig caffeic acid (CFA) l0 mg/kg bid for 3d. The ED50 of abortifacient effect of CFA was 2.13 (mg/kg bid×3 d). The interceptive action of CFA was counteracted by the simultaneous sc megestrol (MG) 50 mg/kg bid ×3 d, ip hCG 10 IU/(mouse∙d)×3d or ig tiapride 50 mg/kd bid ×4 d. 
 CFA inhibited significantly the decidual cell reaction (DCR). This effect was no longer observed when MG was given simultaneously. Moreover, CFA had no effect on DCR of the sex-hormone-treated ovariectomized mice. The plasma progesterone level of the pregnant mice decreased markedly after ig CFA. 
 Histomorphologic examination of the ovaries from aborted or pseudopregnant mice treated by CFA revealed a serious atrophy of the corpora lutea and degeneration and necrosis of the decidual tissue. Even when MG was injected simultaneously, the trivial degeneration of the decidual tissue was still seen.