Show threadLorenAmelangJan 29, 2023

@nadel
"Perhaps now would be a reasonable time to raise questions brought up by the personal histories published so far."

I appreciate the invitation! I'm still thinking about this bit of the Gyuri Buzsaki episode:

"What make the hippocampus special is the granule cell. There is no such cell type in the neocortex. Granule cells keep dividing postnatally and the only cell type known whose life depends on circulating hormones (steroids)."

I've found a few interesting links, including:

Estrogen modulates place learning through estrogen receptors in the hippocampus - Lilia Zurkovsky 2006
(Where they implanted the hormones directly into the rat hippocampus...)

Estrogen Receptors, the Hippocampus, and Memory - Linda A. Bean 2014
(Where they used receptor knockout mice and viral vector delivery of different estrogen receptors to modify the sensitivity to estrogen.)

Do you know of anyone studying this in humans? I guess it would be difficult, since as I (barely and maybe wrongly) understand things, our estradiol level above the blood-brain barrier is higher and poorly correlated with the testable levels circulating below there. And hippocampal E2 is mostly created in the hippocampus itself...

Neurosteroids in Adult Hippocampus of Male and Female Rodents: Biosynthesis and Actions of Sex Steroids - Yasushi Hojo 2018
https://www.frontiersin.org/articles/10.3389/fendo.2018.00183/full

"Penetration of plasma E2 into the hippocampus, however, is not able to account for the level of hippocampal E2 because hippocampal E2 is much higher than that in plasma."

This graphic is fascinating:
https://www.frontiersin.org/files/Articles/357380/fendo-09-00183-HTML-r1/image_m/fendo-09-00183-g001.jpg

Would love to hear anyone's thoughts on the influence of estrogen on spatial awareness and memory!

#hippocampus #estrogen #estradiol #neurosteroids #biosynthesis #GranuleCell

Neurosteroids in Adult Hippocampus of Male and Female Rodents: Biosynthesis and Actions of Sex Steroids

The brain is not only the target of steroid hormones but also is able to locally synthesize steroids de novo. Evidence of the local production of steroids in the brain has been accumulating in various vertebrates, including teleost fish, amphibia, birds, rodents, non-human primates, and humans. In this review, we mainly focus on the local production of sex steroids in the hippocampal neurons of adult rodents (rats and mice), a center for learning and memory. From the data of the hippocampus of adult male rats, hippocampal principal neurons [pyramidal cells in CA1–CA3 and granule cells in dentate gyrus (DG)] have a complete system for biosynthesis of sex steroids. Liquid chromatography with tandem-mass-spectrometry (LC-MS/MS) enabled us to accurately determine the levels of hippocampal sex steroids including 17β-estradiol (17β-E2), testosterone (T), and dihydrotestosterone (DHT), which are much higher than those in blood. Next, we review the steroid synthesis in the hippocampus of female rats, since previous knowledge had been biased toward the data from males. Recently, we clarified that the levels of hippocampal steroids fluctuate in adult female rats across the estrous cycle. Accurate determination of hippocampal steroids at each stage of the estrous cycle is of importance for providing the account for the fluctuation of female hippocampal functions, including spine density, long-term potentiation (LTP) and long-term depression (LTD), and learning and memory. These funct...

Frontiers