Effects of maternal behavior induction and pup exposure on neurogenesis in adult, virgin female rats

Abstract

The states of pregnancy and lactation bring about a range of physiological and behavioral changes in the adult mammal that prepare the mother to care for her young. Cell proliferation increases in the subventricular zone (SVZ) of the female rodent brain during both pregnancy and lactation when compared to that in cycling, diestrous females. In the present study, the effects of maternal behavior induction and pup exposure on neurogenesis in nulliparous rats were examined in order to determine whether maternal behavior itself, independent of pregnancy and lactation, might affect neurogenesis. Adult, nulliparous, Sprague-Dawley, female rats were exposed daily to foster young in order to induce maternal behavior. Following the induction of maternal behavior each maternal subject plus females that were exposed to pups for a comparable number of test days, but did not display maternal behavior, and subjects that had received no pup exposure were injected with bromodeoxyuridine (BrdU, 90 mg/kg, i.v.). Brain sections were double-labeled for BrdU and the neural marker, NeuN, to examine the proliferating cell population. Increases in the number of double-labeled cells were found in the maternal virgin brain when compared with the number of double-labeled cells present in non-maternal, pup-exposed nulliparous rats and in females not exposed to young. No changes were evident in the dentate gyrus of the hippocampus as a function of maternal behavior. These data indicate that in nulliparous female rats maternal behavior itself is associated with the stimulation of neurogenesis in the SVZ.

Neuroendocrine regulation of maternal behavior

“…Although suppression of neurogenesis was associated with deficits in maternal behavior in female mice (Larsen and Grattan, 2010), the precise relationship between neurogenesis in the induction or maintenance of maternal care is not firmly established. However, in nulliparous rats the onset of maternal behavior induced by repeated pup exposure is associated with an increase in neurogenesis in the SVZ (Furuta and Bridges, 2009). Whether the actual induction of maternal behavior is caused by the increase in neurogenesis or whether animals that displayed increases in neurogenesis also have higher levels of neurogenesis is unknown.…”

Hippocampal adult neurogenesis: Its regulation and potential role in spatial learning and memory

“…Furthermore, social isolation reduces hippocampal cell proliferation and cell survival in prairie voles ( Microtus ochrogaster ) and rats (Fowler et al, 2002; Lieberwirth et al, 2012; Spritzer et al, 2011). It should be noted that contrary to aversive social experiences (e.g., exposure to social defeat, resident-intruder, and social isolation), non-stressful social interactions including exposure to male pheromones, maternal experience, and interactions with conspecific pups increase hippocampal neurogenesis in mice, prairie voles, and rats (Furuta and Bridges, 2009; Mak et al, 2007; Ruscio et al, 2008) (for reviews see Gheusi et al, 2009; Lieberwirth and Wang, 2012). …”

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

“…However, ‘sensitized’ virgin rats exposed to pups and induced to display maternal behavior have a greater number of newly born neurons in the SVZ as compared to non-maternal, pup-exposed virgins and virgins not exposed to young (Furuta and Bridges, 2009). These data suggest that maternal behavior itself, independent of pregnancy and lactation, is associated with the stimulation of adult neurogenesis in the rat SVZ.…”