Molecular neuroanatomy of the mouse medial preoptic area with reference to parental behavior

The medial preoptic area (MPOA), an anterior part of the hypothalamus, is one of the most important areas for the regulation of instinctively motivated behaviors, such as parental behavior, mating behavior and aggression. Consistent with its role in reproductive behaviors, the MPOA abundantly expresses gonadal steroid hormone receptors and shows distinct sexual dimorphism in its morphology. Despite the functional importance of the MPOA, the anatomical demarcations of the mouse MPOA subregions have been confusing and remained undefined because of their heterogeneity and complexity. In this review, I first introduce our histological examination showing differential expression of various molecules among the MPOA subregions. I also provide useful molecular markers to delineate the mouse MPOA subregions showing sexual dimorphism. Based on this anatomical study at the subregion level, I also summarize the current understanding of the role of the mouse MPOA and adjacent bed nucleus of the stria terminalis in parental motivation: the central part of the MPOA is essential for parental motivation, and this area exerts an inhibitory effect on the neural activity in the BNST rhomboid nucleus resulting in suppressed infanticide.