Effects of steroid hormones on neurogenesis in the hippocampus of the adult female rodent during the estrous cycle, pregnancy, lactation and aging.

Adult neurogenesis exists in most mammalian species, including humans, in two main areas: the subventricular zone (new cells migrate to the olfactory bulbs) and the dentate gyrus of the hippocampus. Many factors affect neurogenesis in the hippocampus and the subventricular zone, however the focus of this review will be on factors that affect hippocampal neurogenesis, particularly in females. Sex differences are often seen in levels of hippocampal neurogenesis, and these effects are due in part to differences in circulating levels of steroid hormones such as estradiol, progesterone, and corticosterone during the estrous cycle, in response to stress, with reproduction (including pregnancy and lactation), and aging. Depletion and administration of these same steroid hormones also has marked effects on hippocampal neurogenesis in the adult female, and these effects are dependent upon reproductive status and age. The present review will focus on current research investigating how hippocampal neurogenesis is altered in the adult female rodent across the lifespan.