Cellular and molecular signatures of motherhood in the adult and ageing brain

Pregnancy is marked by robust changes involving all organ systems, including brain changes to volume, structure, connectivity, and neuroplasticity. Although some brain changes are restricted to pregnancy and the postpartum, others are long-lasting. Few studies have examined possible mechanisms of these change or and the effects of multiple pregnancies. Here, we characterized various cellular and molecular signatures of parity (nulliparous, primiparous, biparous) in the hippocampus, an important area for cognitive and emotional regulation. We investigated density of neural stems cells(Sox2), microglia (Iba-1), and levels of a synaptic protein (PSD-95), cell signalling pathways, neuroinflammation, and the tryptophan-kynurenine (TRP-KYN) pathway, 1 week after weaning (7 months) and in middle-age (13 months). Parity increased PSD-95 levels in both age groups and prevented the age-related decrease in neural stem cell density observed in nulliparous rats. Biparity increased cell signalling phosphoproteins (pp706sk, S6RP) and number of microglia in the dentate gyrus, regardless of age. Parity resulted in transient changes to the TRP-KYN system. Thus, previous parity has lasting effects on synaptic plasticity and alters the trajectory of hippocampal aging. ### Competing Interest Statement The authors have declared no competing interest.