EVIDENCE FOR A DOMINANT ROLE OF PROLACTIN IN THE LUTEOTROPHIC COMPLEXOF PSEUDOPREGNANT GOATS

Eight pseudopregnant goats, characterized by the presence of aseptic f luid in the uterus and a persistent corpus luteum, were treated with 2 mg bromocriptine for 4 days to study the effects of a temporary decre ase in prolactin secretion on plasma progesterone levels. During treat ment a significant decline in prolactin and progesterone concentration s occurred in all animals. After treatment, fluid was retained in the uterus and progesterone levels increased again in five does (Group I) whereas in three goats (Group II) uterine fluid was discharged and pla sma progesterone values reached values lower than 3.3 nmol l(-1). Mean prolactin concentrations before, during, and after treatment were sig nificantly higher in does of Group I. Luteinizing hormone (LH) pulse f requency on the third day before and on the fourth day during treatmen t did not differ significantly between the two groups. LH pulse amplit ude was higher during bromocriptine treatment but there was no signifi cant difference between the two groups. Because the effects of bromocr iptine on luteal function cannot be explained by a diminished LH suppo rt, it is concluded that prolactin prays a dominating role in the lute otrophic complex during caprine pseudopregnancy.