Neuroendocrine Regulation and Neural Circuitry of Parenthood: Integrating Neuropeptides, Brain Receptors, and...

Maternal behavior encompasses a range of biologically driven responses whose expression and duration vary across species. Maternal responses rely on robust adaptive changes in the female brain, enabling mothers to engage in caregiving, nourishing, and offspring protection. Morphological and functional changes in the maternal brain enhance sensitivity to offspring cues, eliciting maternal behaviors, rewarding responses, and social processing stimuli essential for parenting. Maternal behavior comprises a range of biological responses that extend beyond basic actions, reflecting a complex, evolutionarily shaped neurobiological adaptation. These behaviors can be broadly categorized into direct behaviors, which are explicitly aimed at the care of the offspring, and indirect behaviors that, overall, ensure the protection, nourishment, and survival of the newborn. The secretion of main neuropeptide hormones, such as oxytocin (OT), prolactin (PRL), and placental lactogens (PLs), during the peripartum period, is relevant for inducing and regulating maternal responses to offspring cues, including suckling behavior. Although PRL is primarily associated with reproductive and parental functions in vertebrates, it also modulates distinct neural functions during pregnancy that extend from lactogenesis to adult neurogenesis, neuroprotection, and neuroplasticity, all of which contribute to preparing the maternal brain for motherhood and parenting interactions. Parvocellular OT-containing neurons in the paraventricular nucleus (PVN) and in the anterior hypothalamic nucleus (AHN) project axon collaterals to the medial preoptic area, which, in turn, projects to the nucleus accumbens (NACC) and lateral habenula (lHb) via the retrorubral field (RRF) and the ventral tegmental area (VTA), which mediate the motivational aspects of maternal responses to offspring cues. The reshaping process of the brain and neural networks implicated in motherhood depends on several factors, such as up- and downregulation of neuronal gene expression of bioactive peptide hormones (i.e., OT, PRL, TIP-39, galanin, spexin, pituitary adenylate cyclase-activating polypeptide (PACAP), corticotropin-releasing hormone (CRH), peptide receptors, and transcription factors (i.e., c-fos and pSTAT)) in target neurons in hypothalamic nuclei, mesolimbic areas, the hippocampus, and the brainstem, which, overall, regulate the expression of maternal behavior to offspring cues, as shown in postpartum female rodents. In this review, we describe the modulatory neuropeptides, the neural networks underlying peptide transmission systems, and cell signaling involved in parenthood. We highlight the dysregulation of neuropeptide hormones and their receptors in the central nervous system in relation to psychiatric disorders.