New hyperprolactinemia and anovulation model in common marmoset (Callithrix jacchus) and effect of cabergoline

We aimed to develop an anovulation model, using sulpiride-induced hyperprolactinemia in common marmosets. The serum prolactin level gradually increased during the twice-daily administration of sulpiride and reached a plateau after 4 days. Sulpiride produced as big a response at 10 mg kg(-1) as at 50 mg kg(-1). In this study, the length of the ovarian cycle was approximately 30 days in normal common marmosets. Serum progesterone and estradiol levels showed no consistent change during the first 2 months of treatment with sulpiride. When treatment with sulpiride had been continued for more than 2 months, serum progesterone and estradiol levels fell to within the range seen in the follicular phase of the normal cycle and absence of ovulation was recognized by laparoscopy. A single oral administration of cabergoline (at doses between 0.01 and 0.1 mg kg(-1)) dose dependently reduced the elevated serum prolactin level. Bromocriptine (at an oral dose of 10 mg kg(-1)) also reduced the serum prolactin level at 4 and 8 h after its administration. With bromocriptine, the prolactin level had recovered at 24 h, but with cabergoline at doses of 0.05 mg kg(-1) or more, it had still not recovered at 48 h. In anovulatory common marmosets, oral administration of cabergoline at a daily dose of 0.05 mg kg(-1) restored ovarian function and resulted in ovulation in 100% of the group (following a reduction in the serum prolactin level). Bromocriptine at a daily oral dose of 10 mg kg(-1) resulted in ovulation in 67% of the group, but this dose was about 200 times higher than the dose of cabergoline. We could produce an anovulatory model induced by sulpiride repeatedly administered over a long time period. It is suggested that, in this anovulatory model in common marmosets, cabergoline has a potent and long-lasting action as a dopamine D2 receptor agonist, and thus could be a useful drug for the treatment of galactorrhea and hyperprolactinemic amenorrhea and/or anovulation.