Chronic and unpredictable stress can disrupt the female reproductive system by suppression for secretion of gonadotrophin-releasing hormone (GnRH) and gonadotrophin, resulted in ovarian malfunction and infertility. In the recent days, kisspeptin has been highly highlighted as a hypothalamic peptide which directly stimulates synthesis and release for GnRH. However, in spite of the key role of kisspeptin in the female reproductive system, little information is still available on the changes of its expression during ovarian cycle under stressed condition. Therefore, we induced chronic and unpredictable stress series to the female mice to analyze kisspeptin expression in the brain and ovary. Stressed mice exhibited changes of behavior and body weight gain during the stress assessment, which suggested that the present stress model in mice was successfully established. In the brain level, kisspeptin expression was attenuated than control. In the ovary level, the stressed mice displayed irregularly shrunk oocytes with broken zona pellucida throughout the follicle stages, pyknotic granulosa cells, decreased number of developing follicles and increased number of atretic follicles than the control. In case of kisspeptin expression in the whole ovary tissue, the expression level was decreased in the stressed mice. In detail, the less intensity of kisspeptin expression in the antral follicles phase was observed in the stressed mice than control mice, indicating that local function of kisspeptin during ovary cycle is highly associated with development of ovarian follicles. We expect that the present study has important implications for the fields of reproductive biology.

ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
  Ethics, animals and chemicals
  Stress-induced mice model
  Stress assessment by changes of behavior and bodyweight
  Tissue preparation
  Classification of ovarian follicles
  Immunohistochemistry
  Western blotting
 RESULTS
  Stress assessment by changes of behavior and bodyweight
  Ovarian follicular morphology
  Immunohistochemistry and western blotting forkisspeptin expression in the brain
  Immunohistochemistry and western blotting forkisspeptin expression in the ovary
 DISCUSSION
 CONFLICTS OF INTEREST
 REFERENCES

• Seung-Joon Kim(College of Veterinary Medicine, Kyungpook National University) Correspondence