Abstract：The pineal gland, which is a neuroendocrine organ, is influenced by both the dark-light cycle and the seasonal cycle and plays an important role in the neuroendocrine control of reproductive physiology in a variety of species. This article provides an overview of how photoperiodic information controls seasonal variations in animal reproductive activity through the endocrine activity of the pineal gland and focuses on the role and mode of action of melatonin. Moreover, this review is to update current knowledge about the clock genes in the pineal gland such as period circadian clock (per), cryptochrome (cry), clock circadian regulator (clock) and aryl hydrocarbon receptor nuclear translocator like (arntl or bmal).These clock genes have been found in a variety of vertebrate clock structures including the avian pineal gland. This article provides a better understanding of the molecular mechanisms and physiological correlations of the pineal gland regulates seasonally reproduction.
