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This Article Accepted manuscript (PDF) All Versions of this Article: JOE-07-0602v1 198/1/147    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Zieba, D. Articles by Murawski, M. Search for Related Content PubMed PubMed Citation Articles by Zieba, D. Articles by Murawski, M.

D Zieba, Sheep and Goat Breeding, Agricultural University, Krakow, Poland
M Szczesna, Sheep and Goat Breeding, Agricultural University, Krakow, Poland
B Klocek-Gorka, Sheep and Goat Breeding, Agricultural University, Krakow, Poland
E Molik, Sheep and Goat Breeding, Agricultural University, Krakow, Poland
T Misztal, Endocrinology, Polish Academy of Sciences, Jablonna, Poland
G Williams, Animal Science, Texas A&M University, Beeville, United States
K Romanowicz, Endocrinology, Polish Academy of Sciences, Jablonna, Poland
E Stepien, Independent Laboratory of Molecular Biology and Research, John Paul II Hospital, Krakow, Poland
D Keisler, Animal Science, University of Missouri, Columbia, United States
M Murawski, Sheep and Goat Breeding, Agricultural University, Krakow, Poland

Correspondence: Dorota Zieba, Email: rzzieba{at}cyf-kr.edu.pl

Abstract

Recent studies have demonstrated photoperiodic changes in leptin sensitivity of seasonal mammals. Herein we examined the interaction of season (long-; LD vs short-day; SD) and recombinant ovine leptin (roleptin) on melatonin and prolactin (PRL) secretions and mRNA expression of suppressor of cytokine signaling-3 (SOCS-3) in the mediobasal-arcuate nucleus (MB-ARC) region in sheep. Ewes (n=24), were utilized in a replicated switchback design involving 12 ewes/season and were assigned randomly to one of three groups. Ewes were infused intracerebrventricularly 3 times with following treatments: 1) Control, 2) L1; roleptin, 0.5 µg/kg BW, and 3) L2; roleptin, 1.0 µg/kg BW. Jugular blood samples were collected every 15-minute intervals for 6 hours. At the conclusion of sampling, a washout period (about 3 days) elapsed before ewes were re-randomized and the treatments were repeated. Ewes were then euthanized and MB-ARC were collected for RT-PCR processing. Leptin treatments increased (P < 0.001) circulating leptin concentrations vs controls during both seasons. Overall mean plasma melatonin concentrations were greater (P < 0.001) during LD than SD. However, leptin treatments increased melatonin concentrations during SD in a dose-dependent manner and decreased it during LD. Circulating PRL decreased (P < 0.001) in response to leptin during LD. Leptin increased (P < 0.001) SOCS-3 expression in MB-ARC during LD in a dose-dependent manner. Data provide evidence that melatonin and PRL secretions are inversely regulated by leptin during SD and LD. However, the increase in expression of SOCS-3 in the MB-ARC during LD compared to SD fails to fully explain these effects.