Abortion induction in the cat using prostaglandin F2 alpha and a new anti-prolactinic agent, cabergoline

This study in cats compared the effects of a natural prostaglandin F2 alpha (PGF2 alpha) and cabergoline, administered on and after day 30 after mating, with regard to the plasma progesterone concentration, the induction of abortion and the side effects of each regimen. PGF2 alpha, through a direct luteolytic action, induced abortion by an abrupt and rapid (24 h) decline in the plasma progesterone concentration. Using doses (2 mg per cat) comparable to the ones selected in a previous study, 100% of abortions (4/4) in cats treated from day 33 of gestation were obtained. Cabergoline (1.65 micrograms kg-1 day-1, administered subcutaneously for 5 days), through its antiprolactinic action induced abortion in 80% (4/5) of the cats treated on day 30 of gestation. The abortion was initiated by means of a reduction in plasma progesterone concentration to < 1 ng ml-1. This reduction was not as rapid (3-4 days), however, as that obtained with PGF2 alpha (24 h). Prostaglandins always induced significant side effects such as nausea, prostration, vomiting and diarrhoea, within 10 min following injection, whereas cabergoline never induced side effects or behavioural disturbances. In addition, cabergoline usually induced abortion through fetal resorption (75% of cases), without any clinical sign other than some vaginal discharge.