Biochimica et Biophysica Acta (BBA) - General Subjects
ReviewInfluence of different estrogens on neuroplasticity and cognition in the hippocampus
Section snippets
What is adult neurogenesis and how to study it?
The birth and maturation of new neurons in adulthood, adult neurogenesis, has been found in nearly all mammalian species studied to date, including humans [6], [7], [8], [9], [10], [11], [12], [13]. Adult neurogenesis has been confirmed in at least two main areas: the subventricular zone (new cells from this area migrate to the olfactory bulbs along the rostral migratory stream) and the dentate gyrus of the hippocampus (see Fig. 1). The subgranular zone of the dentate gyrus contains progenitor
Influence of estrogens on other forms of hippocampal synaptic plasticity
The naturally occurring fluctuation in estrogens that occurs across the estrous cycle can dramatically influence the morphology of the hippocampus in female rats. For example estrogens influence the density of dendritic spines in the CA1 region of the hippocampus. Dendritic spines can be classified by their shape into filopodial, thin, stubby, fenestrated or mushroom-shaped spines [143]. Small spines (filopodial and thin) have small head diameters and may be associated with learning processes
Influence of estrogens on cognition
The role of estrogens in eliciting and maintaining reproductive behaviors is well established in the literature. Recently the effects of estrogens on non-reproductive behaviors, such as cognition, have moved to the forefront of research [156]. The relationship between estrogens and cognition is immensely complex and depends on many factors each of which requires unique consideration. These factors include the brain structures and memory systems being recruited by the cognitive task [164], [165]
Conclusions
Endogenous and exogenous fluctuations in estrogens influence neuroplasticity and function of the hippocampus throughout the lifespan. Specifically adult hippocampal neurogenesis in female rats responds to estrogens throughout the lifespan, in a time- and dose-dependent manner. Many of estrogens' effects on the hippocampus are attributed to activation of classical estrogen receptors α and β, although more recent work also implicates nonclassical receptors in the hippocampus. Estrogens rapidly
Acknowledgments
Cindy Barha is a Michael Smith Senior Graduate Studentship. Research from our laboratory reviewed in this paper was made possible by operating grants from NSERC, CIHR and PARF (Pacific Alzheimer Research Foundation). LAMG is a Michael Smith Senior Scholar.
References (215)
Hippocampus: cognitive processes and neural representations that underlie declarative memory
Neuron
(2004)- et al.
Hippocampal formation: shedding light on the influence of sex and stress on the brain
Brain Res. Rev.
(2007) Gonadal hormone modulation of neurogenesis in the dentate gyrus of adult male and female rodents
Brain Res. Rev.
(2008)- et al.
Progenitor cells in the adult zebrafish nervous system express a Brn-1-related POU gene, tai-ji
Mech. Dev.
(1998) - et al.
Sex and seasonal differences in the rate of cell proliferation in the dentate gyrus of adult wild meadow voles
Neuroscience
(1999) - et al.
Stem and progenitor cells: the premature desertion of rigorous definitions
Trends Neurosci.
(2003) - et al.
Differentiation of newly born neurons and glia in the dentate gyrus of the adult rat
Neuroscience
(1993) - et al.
Hippocampus-dependent learning promotes survival of new neurons in the dentate gyrus at a specific time during cell maturation
Neuroscience
(2007) - et al.
Repeated estradiol administration alters different aspects of neurogenesis and cell death in the hippocampus of female, but not male, rats
Neuroscience
(2008) BrdU immunohistochemistry for studying adult neurogenesis: paradigms, pitfalls, limitations, and validation
Brain Res. Rev.
(2007)