Effects of Para-Chlorophenylalanine on Pregnancy in the Rat

To test the hypothesis that 5-hydroxytryptamine (5HT) may play a role in the onset of parturition, rats were given p -chlorophenylalanine (PCPA), an inhibitor of 5HT synthesis, via gavage. PCPA administration greatly affected pregnant rats. High dosages of PCPA (316 mg/kg/day on alternate days) induced total resorption between Days 12 and 15 and reduced maternal weight gain. Lower dosages of PCPA (158 mg/kg/day on Days 2, 4, 6, 8, 10, and 12 and 316 mg/kg/day on Days 14, 16, 18, 20, and 21) resulted in partial resorption, reduced maternal and fetal weight gain, immediate neonatal death, and cannibalism. 5HT was significantly reduced in maternal brain (97%), placentas (82%), whole fetuses (96%), and uteri (69%). Maternal adrenal hypertrophy occurred only when conceptuses were present. Because gestational length was not altered, we concluded that 5HT did not play a significant role in the onset of parturition.