Stimulation of prolactin secretion by chronic, but not acute, administration of leptin in the rat

Leptin, the product of obese (ob) gene, has been reported to affect the sec retion of all six anterior pituitary hormones, but data are especially scar ce regarding the interplay between leptin and prolactin (PRL). Thus, in thi s study we examined and compared in vivo the effects of acute and chronic a dministrations of recombinant mouse leptin on PRL secretion in male rats. N ormally-fed and 3-day-fasted rats received an intraperitoneal bolus injecti on of leptin [1.0 mg/kg body weight (BW)] or vehicle only. The leptin treat ment was without effect on; plasma PRL levels up to 5 h postadministration. Food deprivation for 3 days significantly decreased both PRL and leptin le vels. This decrease in plasma PRL was prevented by a 3-day constant infusio n of 75 mug/kg BW/day of leptin, which maintained plasma leptin levels simi lar to those of normally-fed rats. The administration of three times the hi gher dose of leptin (225 mug/kg BW/day) to fasted rats led to further incre ases in both PRL and leptin in the plasma. Thus, a dose-dependent stimulato ry effect of chronic leptin treatment on PRL secretion was indicated. This study demonstrates that chronic, but not acute, administration of leptin st imulates PRL secretion in the rat. (C) 2000 Elsevier Science B.V. All right s reserved.