Australian Journal of Basic and Applied Sciences 2019 June; 13(6): pages 62-73 DOI: 10.22587/ajbas.2019.13.6.7 Original paper AENSI Publications Journal home page: www.ajbasweb.com Australian Journal of Basic and Applied Sciences ISSN: 1991-8178, EISSN: 2309-8414 Comparative Study Between Lemon Peel Extract and Testosterone Supplementation on the Hippocampus of Orchiectomized Rat *Lubna Taher Mahmoud Eid., Mostafa Mahmoud El-Habeby., Neveen Mohamed El-Sherif., Manar Ali Faried Department of Anatomy and Embryology, Faculty of Medicine, Menoufia University, Menoufia, Egypt. Correspondence Author: Lubna Taher Mahmoud. Department of Anatomy and Embryology, Faculty of Medicine, Menoufia University, Menoufia, Egypt. E-mail: lubna.taher.90@gmail.com Received date: 20 May 2019, Accepted date: 20 June 2019, Online date: 29 June 2019 Copyright: © 2019 Lubna Taher Mahmoud et al., This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Keywords: lemon peel extract, hippocampus, orchiectomy, testosterone replacement INTRODUCTION Physiologically, androgens are involved in development, differentiation, and survival of neurons (Hammond et al., 2001) . With aging, the testosterone level in men begins to decline (Feldman et al., 2002) leading to changes in androgen responsive tissues as the hippocampus, prostate, heart, and skin (Moore and Urban, 2004) . Therefore, the hippocampus is a target for testosterone action and hence is vulnerable to gradual age-related decline of testosterone level in men (Elnegris and Mohamed, 2012). The hippocampus plays a crucial role in the consolidation of memories (Jacobs et al., 2013); consequently, a brain lesion causing hippocampal damage results in anterograde amnesia (Gregory et al., 2014). Orchiectomy is a way of studying the consequences of testosterone deficiency in animal models (Mohamed et al., 2014). Androgen depletion leads to apoptosis of neurons (Hammond et al., 2001) with the release of some proteins, including proapoptotic and antiapoptotic proteins. Moreover, testosterone deficiency leads to excess production of reactive oxygen species (ROS) and reduction of antioxidant agents responsible for the metabolism of ROS (Abdel Moneim, 2014). Abstract Background: The hippocampus is a sensitive region of the brain for testosterone action thus is vulnerable to post orchiectomy and age-related testosterone deficiency. Objectives: The current work aimed to study the histological changes in the hippocampus of experimentally orchiectomized rats. Moreover, to the best of our knowledge, this research is the first attempt to assess the beneficial role of lemon peel extract supplementation in comparison with testosterone replacement. Methods: Thirty adult male albino rats were divided into five groups; sham control, lemon peel treated (200 mg/kg/day orally), orchiectomy (ORX), orchiectomy treated with lemon peel and orchiectomy treated with testosterone (100mg/kg i.m once). Thirty days later, the hippocampal sections were subjected to histological and immunohistochemical analyses for the expression of inducible nitric oxide (iNOS), Bax, glial fibrillary acidic protein (GFAP) and microtubule associated protein (Tau1). In addition, Total serum testosterone level was measured. Results: Orchiectomy produced neurodegeneration with significant decrease of the pyramidal layer thickness, number of the pyramidal cells and their Nissl’s granules content. Immunohistochemically, there was a significant upregulation of iNOS, a marker for oxidative stress, Bax, a proapoptotic marker, and GFAP, a marker for reactive astrocytes, with significant downregulation of Tau1, a microtubule associated protein, immunoreaction. In addition, serum total testosterone level was significantly decreased compared to the sham control group. Both testosterone and lemon peel treated groups ameliorated the orchiectomy induced hippocampal neurodegeneration via a significant downregulation of iNOS, Bax and GFAP expression and a significant upregulation of Tau1 expression. Moreover, the pyramidal layer thickness, the number of its pyramidal cells and their Nissl’s granules content were significantly increased in both treated groups compared to the orchiectomized one. Furthermore, serum total testosterone level was significantly increased compared to the orchiectomized group. Conclusion: testosterone depletion due to orchiectomy produced hippocampal neurodegenerative changes. Administration of testosterone or lemon peel extract improved these changes.