Adult Neurogenesis during Lactation and Maternal Behavior: Implications of melanin-concentrating hormone (MCH) and Melatonin

Abstract

The transition period for maternity is marked by drastic physiological and behavioral adaptations that aim to supply the increase in energy demand and meet the needs of the offspring through breastfeeding and maternal care. These changes are mediated by extensive remodeling of the neural circuits. The continuous generation of new neurons (neurogenesis) emerges as an essential mechanism of neuroplasticity that contributes to the maternal brain. To date, there are no studies that have tracked how levels of neurogenesis and alteration throughout lactation. Also, little is known about the dynamics of hypothalamic neurogenesis during lactation and whether it also has implications for maternal behavior. Hormones and neuropeptides linked to energy balance play a critical role in the metabolic adaptations induced by lactogenesis and expression of maternal behavior. The melanin-concentrating hormone (MCH) is a peptide that acts in the regulation of energy balance. Notably, during lactation, the MCH is synthesized in the preoptic area (MPOA), a region critical to the expression of maternal behavior. This pattern of MCH expression may be related to neurogenic processes. Melatonin, a hormone synthesized by the pineal gland during the nighttime, among other functions, is involved in the regulation of food consumption, energy metabolism, and neural plastic processes. Serum levels of maternal melatonin are increasing during the gestational period; however, how their levels fluctuate during lactation, a period of high energy demand, it is not clear. Changes in energy homeostasis drastically influence hippocampal and hypothalamic neurogenesis, since melatonin and MCH plays an essential role in eating behavior and energetic metabolism. These factors may modulate the neurogenesis process during lactation. In this proposal, we aimed to understand how the process of hippocampal and hypothalamic neurogenesis fluctuate during the lactation period and the possible correlations with melatonin and MCH levels.