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Home | Pregnancy Timeline | News Alerts |News Archive Jun 8, 2015

"Maternite" 1890 by Mary Cassatt





Motherhood permanently alters your brain

Motherhood permanently alters the brain and its response to hormone therapy later in a woman's life.

Dr. Lissa Galea of the University of Buffalo, has scientific interest in how hormones affect brain and behavior. She has oberved in her career that one hormone not receiving much attention were estrogens used in hormonal therapy. Yet they have been shown to have variable effects on brain function through three forms: estradiol (or oestradiol), estrone (also known as oestrone) and estriol (also called oestriol).

Hormone therapy (HT) is prescribed to alleviate some of the symptoms of menopause in women who are more likely to be diagnosed with Alzheimer's disease — though not other forms of dementia. HT has been prescribed to treat cognitive decline in post-menopausal women with varying degrees of effectiveness.

Estradiol (oestradiol in American and British English) is the most potent of the estrogens, and is the predominant estrogen in young women. While estrone is a weaker estrogen predominantly found in post-menopausal women.

Dr. Galea presented her latest findings on hormone therapy and brain function at the 9th Annual Canadian Neuroscience Meeting.

New research by Dr. Galea, at the University of British Columbia, suggests estrogens used in HT and influenced by previous motherhood could be critical in explaining why HT has variable effects.

Research in women, confirmed by Dr. Galea's research in rats, shows that the form of estrogen called estradiol (predominant in young women) has many beneficial effects. However, the beneficial effects of estrone depended on whether or not the rats had previously been mothers. Yet, estrone-based HT was found to impair learning in middle-aged rats that had been mothers — but improve learning in rats that were never moms.

Dr. Galea's latest results were presented at the 9th Annual Canadian Neuroscience Meeting, on May 25th 2015 in Vancouver British Columbia.

"Our most recent research shows that previous motherhood alters cognition and neuroplasticity in response to hormone therapy, demonstrating that motherhood permanently alters the brain."

Liisa Galea PhD, Professor, Laboratory of Behavioural Neuroendocrinology, Department of Psychology, University of British Columbia, Vancouver, BC

Dr. Galea's interests lay in how hormones affect brain and behavior. She has oberved that one hormone not receiving much attention are estrogens used in HT hormone therapy. (HT) has been shown to have variable effects on brain function. There are three forms of estrogens: estradiol, estrone and estriol. Estradiol is the most potent of estrogens, and it is the predominant form in young women, while estrone is a weaker estrogen and is the predominant form in post-menopausal women.

A systematic review of published scientific literature indicates estradiol-based HT may have more beneficial effects, while estrone-based HTs may have more detrimental effect on cognition and risk of dementia in women.


Dr. Galea focuses on a specific
brain region
called the hippo-
campus, important in memory
and spatial abilities such as
navigation. Both estradiol and
estrone increase the production
of new cells in a part of the
hippocampus called the dentate
gyrus. However, only estradiol
significantly increased the survival of new neurons increasing the expression of zif268, a protein involved in neuroplasticity.

Estradiol improved performance of young female rats in a test called the water maze. The water maze tests memory and orientation as rats must swim to a submerged platform relying on visual cues to orient themselves. Rats receiving estradiol based HT found the platform significantly better than those rats receiving estrone-based HT.

Finally, Dr. Galea's previous research had shown that motherhood causes changes in the architecture of connections in the hippocampus, so her team investigated whether the different forms of estrogens could have different effects on rats that had experienced motherhood once (primiparous rats) and on those who had not (nulliparous rats).

Galea's team found that estrone-based HT improved learning in middle-aged rats who had never had a litter, but impaired learning in rats of the same age who had had even one litter.

As estrone is a component of the most common form of HT prescribed for women in the US, her findings might also have implications on the treatment of age-related neuro-degenerative disorders in women. "Hormones have a profound impact on our mind. Pregnancy and motherhood are life-changing events resulting in marked alterations in the psychology and physiology of a woman. Our results argue that these factors should be taken into account when treating brain disorders in women," concludes Dr. Galea.

From Dr Galea's University of British Columbia website:

Since 1994, I have studied the effects of gonadal hormones on cognition in the male and female rodent. I found that spatial learning in the female rodent is related to both adult and developing levels of gonadal hormones (Galea et al., 1996). Endogenous high levels of estrogen are negatively correlated with spatial performance in the adult female meadow vole and laboratory rat. We have found that high levels of estradiol impaired working and reference memory performance (at different doses) on the working/ reference memory version of the radial arm maze, relative to controls (Galea et al., 2001; Holmes et al., 2002). In contrast, lower levels of estradiol facilitated working memory performance in this same task relative to controls. We found similar effects of estradiol on working memory performance in prefrontal cortex dependent non-spatial delayed alternation task in female rats (Wide et al., 2004). Thus, estradiol has a dissociable effect on differential memory processes, with high levels impairing reference and working memory, and medium levels facilitating working memory in tasks in which performance relies on the integrity of either the hippocampus or prefrontal cortex. Recently we have found that estradiol infused into the prefrontal cortex or hippocampus facilitates working memory but at very different doses, suggesting that the different estrogen receptor distribution in these areas may influence how estradiol affects working memory (Sinopoli et al., 2006). We also found that estradiol infused into the hippocampus impaired working memory 24 h later suggesting that estrogen-regulated gene transcription in the hippocampus, but not prefrontal cortex, interferes with working memory performance (Sinopoli, Floresco, and Galea, 2006). In addition, we have recently found that low estradiol facilitates response and cue-based learning rather than affecting behavioural flexibility per se in a set-shfiting task (Block et al., 2006 abst).

About the Canadian Neuroscience Meeting
The Canadian Association for Neuroscience is holding its 9th Annual Meeting in Vancouver, May 24 to 27 2015. Held yearly since 2007, it brings together researchers working in all fields of neuroscience research. Organized by neuroscientists and for neuroscientists, it highlights the best and most novel neuroscience research in Canada every year.
About the Canadian Association for Neuroscience:

The Canadian Association for Neuroscience is the largest association dedicated to the promotion of all fields of neuroscience research in Canada. The association has been organizing a yearly annual meeting since 2007. Learn more about our meeting at: http://can-acn.org/meeting2015

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