Is melanin-concentrating hormone in the medial preoptic area a signal for the decline of maternal care in late postpartum?

• Melanin-concentrating hormone (MCH) in the hypothalamic area (LHA) stimulates maternal behavior in early postpartum period. • MCH in the medial preoptic area (MPOA) suppresses maternal behavior in middle to late postpartum period. • MCH in the MPOA is an endogenous neurochemical signal evolved to trigger the declining process of maternal care. • MCH in the MPOA is hypothesized to inhibit maternal approach motivation and/or increase maternal withdrawal. • MCH in the LHA and MPOA interacts with the mesolimbic dopamine D 1 /D 2 and serotonin 5-HT 2C receptors to affect maternal behavior. This manuscript proposes that melanin-concentrating hormone (MCH) in the medial preoptic area (MPOA) is an neurochemical signal evolved to trigger the declining process of maternal care. MCH in the MPOA appears only after parturition and is progressively increased with the progression of lactation, while maternal behavior declines progressively. Intra-MPOA injection of MCH decreases active maternal responses. MCH is also highly responsive to infant characteristics and maternal condition. Behavioral changes induced by MCH in late postpartum period are conducive to the decline of infant-directed maternal behavior. The MPOA MCH system may mediate the maternal behavior decline by suppressing the maternal approach motivation and/or increasing maternal withdrawal via its inhibitory action onto the mesolimbic dopamine D 1 /D 2 receptors and its stimulating action on serotonin 5-HT 2C receptors in the ventral tegmental area. Research into the MCH maternal effects will enhance our understanding of the neurochemical mechanisms underlying the maternal behavior decline. [ABSTRACT FROM AUTHOR]