Photoperiodic Regulation of Leptin Synthesis in Anterior Pituitary Gland of Rats

Abstract

Purpose: The goal of this study was to perform an immunohistochemical evaluation, investigate the effects of photoperiod on leptin synthesis in the rat anterior pituitary cells. Material and Methods: For this purpose, 21 male Wistar rats were used. Animals were divided into three equal groups. Control rats in group I were kept under 12 hrs light: 12 hrs dark conditions (12L: 12D) for 10 weeks. Animals in group II were exposed to long photoperiods (18L: 6D), while rats in group III were exposed to short photoperiods (6L: 18D) for 10 weeks. At the end of experimental period, all animals were killed by decapitation. The pituitary glands of all rats were removed and processed for semi-quantitative evaluation of immunohistochemical leptin staining. Intensity of immunostaining was determined on a scale between 0 (no staining) and 5 (heavy staining). Statistical analysis was performed using the Kruskal-Wallis and Dunn's tests. Results: Immunostaining of leptin was moderate (3+) in control rats, strong (4+) in rats exposed to long photoperiods and minimal (1+) in animals exposed to short photoperiods, respectively. The present immunohistochemical findings suggest that leptin production in anterior pituitary cells increase after exposure to long photoperiods and decrease after exposure to short photoperiods. Conclusion: In view of the present findings, photoperiod seems to have effects on leptin synthesis in the anterior pituitary gland of rats.