Leptin116-130 stimulates prolactin and luteinizing hormone secretion in fasted adult male rats

Leptin is a hormone secreted by adipocytes with an important role in the control of feeding behavior and neuroendocrine function. Leptin stimulates in vivo LH secretion in fasted female rats and in vitro PRL secretion. Recent data indicate that leptin(116-130), an active fragment of the native molecule, exerts effects similar to those of the native peptide on body weight and food intake. The present study was carried out to determine whether th is fragment is also able to stimulate LH and PRL secretion. Adult male rats fasted for 5 days were injected with saline or leptin(116-130) (15 mu g i.c.v.) and LH and PRL con centrations were measured thereafter at 15-min intervals during a 150-min period. Administration of leptin(116-130) increased the frequency of LH pulses (2.0 +/- 0.26 vs. 1.20 +/- 0.37/150 min; p less than or equal to 0.05), mean LH levels (0.24 +/- 0.06 vs. 0.07 +/- 0.03 ng/ml; p less than or equal to 0.05), LH pulse amplitude (0.33 +/- 0.10 vs. 0.10 +/- 0.05 ng/ml; p less than or equal to 0.05) and the net LH secretion estimated by area under curve (AUC: 36 +/- 8.5 vs. 9 +/- 3.9 ng/ml/150 min; p less than or equal to 0.01). In addition leptin(116-130) increased the frequency of PRL pulses (2.83 +/- 0.48 vs. 1.33 +/- 0.21/150 min; p less than or equal to 0.05), trough PRL levels (5.71 +/- 0.99 vs. 2.72 +/- 0.32 ng/ml; p less than or equal to 0.01), mean PRL levels (13.02 +/- 0.92 vs. 5.89 +/- 0.51 ng/ml; p less than or equal to 0.01) and net PRL secretion (AUC: 1,625 +/- 171 vs. 658 +/- 46 ng/ml/150 min; p less than or equal to 0.05). In conclusion, these data show that leptin(116-130) stimulates LH and PRL secretion in fasted adult male rats.