Our previous work suggests that melatonin mediates a “seasonal switch” from gonadal regulation of aggression during LDs to adrenal regulation of aggression during SDs in Siberian hamsters (reviewed in Munley et al. 2018, Frontiers in Endocrinology). Most of our studies, however, used timed melatonin injections to experimentally manipulate endogenous levels of circulating melatonin. Because this technique systemically alters melatonin levels, it is difficult to distinguish how melatonin acts locally to facilitate this seasonal shift in neuroendocrine regulation. Furthermore, since melatonin receptors are present in several different tissues within the hypothalamic-pituitary-gonadal (HPG) and hypothalamic-pituitary-adrenal (HPA) axes, it possible that melatonin modulates seasonal changes in behavior via one or more tiers of these neuroendocrine pathways.
The goal of this project is to assess the role of adrenal MT1 melatonin receptors in regulating seasonal aggression in male Siberian hamsters. For this study, I am examining the effects of adrenal MT1 melatonin receptor overexpression on aggressive and non-aggressive social behaviors using lentiviral vectors. Unlike most mammals, which possess two subtypes of melatonin receptor (i.e., MT1 and MT2 melatonin receptors), Siberian hamsters only possess one functional melatonin receptor: the MT1 receptor. Thus, this species is ideal for elucidating how melatonin facilitates seasonal changes in aggression, since we can be confident that the actions of melatonin on aggression occur solely via the MT1 receptor subtype in these animals.
This project is being conducted in collaboration with Dr. Aaron Jasnow at the University of South Carolina School of Medicine.