Hippocampal morphology is differentially affected by reproductive experience in the mother

Abstract

Pregnancy and mothering result in a number of hormonal, neurological, and behavioral changes that are necessary to ensure reproductive success. With subsequent reproductive experience (multiparity and mothering), further neurological and behavioral changes may result. Recent research has shown that previous motherhood enhances both hippocampus-dependent learning and memory and long-term potentiation (LTP); together with decreases in hippocampus volumes during pregnancy it is suggested that the hippocampus is affected by pregnancy and/or mothering. The present experiment aimed to investigate the effect of reproductive experience (nulli, primi-, and multiparity and mothering) on dendritic morphology in the CA1 and CA3 regions of the hippocampus. Brains were stained with a modified version of the single-section Golgi impregnation technique, and dendritic length, number of branch points, and spine density was analyzed for apical and basal regions of CA1 and CA3 pyramidal neurons. Primiparity and/or mothering resulted in dendritic remodeling in both the CA1 and CA3 hippocampal regions, and multiparity resulted in enhanced spine density in the basal CA1 region, which was positively correlated with number of male pups in a litter. These findings point to the effect of reproductive experience and offspring on plasticity in the hippocampus, an area not traditionally associated with motherhood.

Estrous cycle, pregnancy, and parity enhance performance of rats in object recognition or object placement tasks

“…Dams having had at least one litter typically outperform virgins on tasks of cognitive performance (Kinsley et al 1999, Love et al 2005, Bodensteiner et al 2006, Pawluski et al 2006a, Macbeth et al 2008. Primiparous or multiparous dams are found to have a greater spinal density on hippocampal dendrites compared with nulliparous dams (Pawluski & Galea 2006). Dendritic remodeling has also been detected in late-pregnant and postpartum rats (Kinsley et al 2006) Figure 4 Depicts circulating concentrations of 3a,5a-THP (top), estrogen (E 2 , middle), and corticosterone (bottom) in tail blood of primiparous (nZ10) and multiparous (nZ10) rats across gestation.…”

“…These levels increase steadily throughout gestation and do not decline until parturition is imminent (Concas et al 1998). The resulting endocrine milieu, as well as limbic morphology and function, are altered following pregnancy, parturition, and/or pup rearing (Featherstone et al 2000, Tomizawa et al 2003, Pawluski & Galea 2006. First, oxytocin associated with motherhood enhances longterm potentiation (LTP) of hippocampal tissue slices in culture and central infusions of oxytocin enhance longterm spatial memory in virgin mice (Tomizawa et al 2003).…”

“…First, oxytocin associated with motherhood enhances longterm potentiation (LTP) of hippocampal tissue slices in culture and central infusions of oxytocin enhance longterm spatial memory in virgin mice (Tomizawa et al 2003). Second, hippocampal spinal density is increased in pregnant compared with non-pregnant rats and is also altered by postpartum mothering (Kinsley et al 2006, Pawluski & Galea 2006. Third, neurogenesis in the subventricular zone of mice and rats is enhanced during pregnancy (Shingo et al 2003, Furuta & Bridges 2005.…”

“…The present study supports these findings, demonstrating a greater cognitive performance in multiparous, compared with nulliparous, dams. It cannot be ignored, however, that many studies to date have either found no cognitive and/or morphological differences between primiparous and multiparous dams, or have found differences that favor primiparous over multiparous dams (Wartella et al 2003, Love et al 2005, Pawluski & Galea 2006, Pawluski et al 2006a. One explanation may be that the beneficial effects of multiple pregnancies do not summate in a long-term manner.…”

Pup exposure elicits hippocampal cell proliferation in the prairie vole

“…Phenotypic identification confirms that the majority (approximately 50-69 percent) of BrdU labeled cells also possess a neuronal marker across conditions. Among other the rodent species the onset of parental behavior is known to be associated with changes in cell morphology [22,43] and neurogenesis [42,52] within the hippocampus. Furthermore, parity is associated with marked changes in hippocampal dependent memory and spatial tasks [21,24,31,45].…”