Effect of suppressing prolactin in the mouse on liveweight, food intake and ovulation rate

The involvement, if any, of prolactin in the relationship between appetite and ovulation rate was studied in mice. Injections of 0, 50, 100 or 150 micrograms of bromocriptine were given twice-daily to 46-day-old virgin mice for a minimum of 15 days. Between days 5 and 12 of treatment, mice receiving either 50, 100 or 150 micrograms of bromocriptine consumed 3.1, 4.3 and 6.2 g more food, respectively, than did mice in the control group. Liveweights and liveweight gain, however, were unaffected by bromocriptine injections. From day 0 to 12 of treatment mice grew 0.16, 0.15, 0.21 and 0.16 g/day in the 0, 50, 100 and 150 micrograms bromocriptine groups, respectively, (P greater than 0.05). Plasma prolactin concentrations were suppressed, but ovulation rates were similar in the 50, 100 and 150 micrograms bromocriptine groups compared with the control (median prolactin concentrations and mean ovulation rates were 32.9, 32.5 and 31.6 ng/ml and 14.4, 15.1 and 15.7 ova, respectively, compared with 217.2 ng/ml and 14.9 ova in the control). The results do not support the hypothesis that prolactin directly mediates a relationship between appetite and ovulation rate in the post-pubertal mouse.