Long-term alterations in neural and endocrine processes induced by motherhood in mammals

Abstract

The reproductive experience of pregnancy, lactation and motherhood can significantly remodel the female’s biological state, affecting endocrine, neuroendocrine, neural, and immunological processes. The brain, pituitary gland, liver, thymus, and mammary tissue are among the structures that are modified by reproductive experience. The present review that focuses on rodent research, but also includes pertinent studies in sheep and other species, identifies specific changes in these processes brought about by the biological states of pregnancy, parturition, and lactation and how the components of reproductive experience contribute to the remodeling of the maternal brain and organ systems. Findings indicate that prior parity alters key circulating hormone levels and neural receptor gene expression. Moreover, reproductive experience results in modifications in neural processes and glial support. The possible role of pregnancy-induced neurogenesis is considered in the context of neuroplasticity and behavior, and the effects of reproductive experience on maternal memory, i.e. the retention of maternal behavior, together with anxiety and learning are presented. Together, these sets of findings support the concept that the neural and biological state of the adult female is significantly and dramatically altered on a long-term basis by the experiences of parity and motherhood. Remodeling of the maternal brain and other biological systems is posited to help facilitate adaptations to environmental/ecological challenges as the female raises young and ages.

Gestational hormone profiles predict human maternal behavior at 1-year postpartum

“…For example, multiparous rodent and human mothers who have given birth more times exhibit more profound changes in cognitive function (Gatewood et al, 2005; Glynn, 2012). These findings also are consistent with the assertion that pregnancy exerts a lasting imprint on the female that will affect subsequent hormone exposures (Bridges, 2016; Fox et al, 2015; Glynn, 2012; Musey et al, 1987), an assertion for which some additional evidence exists. For instance, nulliparous rats are more sensitive to estrogen exposures at a molecular level than are multiparous rats (Bridges and Byrnes, 2006).…”

The birth of new neurons in the maternal brain: Hormonal regulation and functional implications

“…In this regard, it is worth noting that there are various hormonal and neurochemical differences between primiparous and multiparous rats (Numan and Insel, 2003; Bridges, 2015). For example, multiparty is associated with higher estradiol and lower prolactin during gestation as compared to primiparity (Bridges et al, 1993; Paris and Frye, 2008).…”

“…The neural modifications found in the maternal brain are numerous and widespread (Figure 1) consisting of neurochemical, neuroendocrine, activational, morphological, gene expression and functional changes within a distributed but interconnected circuitry (Theodosis et al, 1986; Xerri et al, 1994; Featherstone et al, 2000; Keyser-Marcus et al, 2001; Tomizawa et al, 2003; Rasia-Filho et al, 2004; Febo et al, 2005; Miranda and Liu, 2009; Sanna et al, 2009; Leuner et al, 2010; Canavan et al, 2011; Salmaso et al, 2011a; Salmaso et al, 2011b; Lonstein et al, 2014; Bridges, 2015; Cohen and Mizrahi, 2015; Corona and Levy, 2015; Elyada and Mizrahi, 2015) that includes the hypothalamus, amygdala, nucleus accumbens, olfactory bulb, hippocampus and various cortical areas (i.e. parietal, auditory, somatosensory, prefrontal).…”

Perinatal BPA exposure and reproductive axis function in CD-1 mice

“…In spontaneous estrous cycles, ovulation occurs through temporally mediated estrogen-induced positive feedback; in the forced-bred regimen, ovulation during postpartum estrus may be triggered by hormone changes at the time of parturition, [47] and in the early postpartum period [1] as well as cervical vaginal stimulation associated with labor [2]. In addition, prior parity or reproductive experience in rodents can result in altered circulating hormone levels and changes in sensitivity to neurotransmitters [48,49]. Therefore, if multiple pregnancies result in similar permanent changes, the hormonal milieu and regulation of a multiparous mouse may be very different from an agematched nulliparous female.…”