Research progress on the role of melatonin and its receptors in animal reproduction: A comprehensive review

Abstract

Melatonin and its receptors play a crucial role in the regulation of the animal reproductive process, primarily in follicular development. However, the role that melatonin performs in regulating hormones related with reproduction remains unclear. Melatonin and its receptors are present both in female and male animals' organs, such as ovaries, heart, brain and liver. Melatonin regulates ovarian actions and is a key mediator of reproductive actions. Melatonin has numerous effects on animal reproduction, such as protection of gametes and embryos, response to clock genes, immune-neuroendocrine, reconciliation of seasonal variations in immune function, and silence or blockage of genes. The growth ratio of reproductive illnesses in animals has raised a remarkable concern for the government, animal caretakers and farm managers. In order to resolve this challenging issue, it is very necessary to conduct state-of-the-art research on melatonin and its receptors because melatonin has considerable physiognomies. This review article presents a current contemporary research conducted by numerous researchers from the entire world on the role of melatonin and its receptors in animal reproduction, from the year 1985 to the year 2017. Furthermore, this review shows scientific research challenges related to melatonin receptors and their explanations based on the findings of 172 numerous research articles, and also represents significant proficiencies of melatonin in order to show enthusiastic study direction for animal reproduction researchers.

Effects of Melatonin Administration to Pregnant Ewes under Heat-Stress Conditions, in Redox Status and Reproductive Outcome

“…Two high-affinity G-protein-coupled receptors, melatonin MT1 and MT2 receptors, are expressed in sheep oocytes, cumulus cells, and granulosa cells [56], and the presence of MT1 receptors was found in sheep blastocysts, confirming the direct impact of melatonin on embryo development [53]. Moreover, the exogenous melatonin treatment of bovine granullosa cells has been shown to suppress apoptosis through interaction of MT1 and MT2 in a time-and dose-dependent manner [57], leading to the conclusion that MT1 is a crucial factor for the survival of granulosa cells [58].This impact is further confirmed by the clear correlation that was found in the present study between the GSH assayed at D23 (i.e., on the 7th day of pregnancy when the blastocyst has already developed) and the number of foetuses measured on D50 (Figure 11).…”

Effects of Photoperiod Regime on Meat Quality, Oxidative Stability, and Metabolites of Postmortem Broiler Fillet (M. Pectoralis major) Muscles

“…Particularly, l-tyrosine has a positive impact on reducing levels of stress hormones [50] and ameliorates negative effects of sleep deprivation [51,52], and l-tryptophan has been well-established as a precursor for melatonin and serotonin [53,54]. Melatonin has a key role in regulation of circadian rhythm, and its production is suppressed by light exposure [55,56]. Given this relationship of these amino acids to stress and diurnal rhythm, the present study provides some evidence for a mechanism of extreme lengths of photoperiods on increasing oxidative stress.…”

Insights into Potential Targets for Therapeutic Intervention in Epilepsy

“…Melatonin regulates several mammalian biological processes such as circadian rhythm [483], sleep [484], reproduction [485], retinal physiology [478], glucose homeostasis [486], memory [487], blood pressure control [488], immune function [489] and free-radical scavenging [490]. Furthermore, other results suggest that melatonin has antinociceptive [491], antidepressant [492], antioxidant [493] and anxiolytic effects [494].…”