Estrogen receptor-alpha immunoreactivity in the arcuate hypothalamus of young and middle-aged female mice.
BACKGROUND
Changes in the neuroendocrine regulation of gonadal function, via altered hypothalamic sensitivity to peripheral hormones, are known to schedule reproductive maturation in the young and influence reproductive senescence. Estrogen (E) is a key hormone in this process. While changes in circulating levels of E over the life span are well documented, less is known about the corresponding changes in E sensitivity over the lifespan, especially during middle-age, when the initial signs of reproductive senescence emerge.


OBJECTIVE
Taking Estrogen Receptor (ER)-alpha-immunoreactive cells as an index of hypothalamic sensitivity to E, this investigation aims to quantify alterations occurring at middle age in comparison to young age.


METHODS
We counted ER-alpha-immunoreactive (IR) cells in the Arcuate hypothalamus of 6-week-old (young) and 18-month-old (middle-aged) C57BL/6J female mice, sacrificed at vaginal opening and diestrous, respectively. An automated imaging microscopy system (AIMS) was employed to generate counts of ER-alpha-IR cells for each sampled section of the Arcuate nucleus (ARC).


RESULTS
This study shows a 21% reduction in the number of ER-alpha-IR cells and an 18% reduction in total ARC cell populations with aging. However, the calculated percentage of ER-alpha IR cells is similar in both young and middle aged mice, 30% and 29%, respectively.


CONCLUSIONS
Both ER-alpha IR cell populations and total cell populations within the ARC hypothalamus decline by middle age in comparison to young age. Despite such a significant decrease in ER-alpha immunoreactive and total cells, both young and middle age mice maintain a similar ratio of ER-alpha IR cells to total cells in the ARC hypothalamus.
Semel Institute for Neuroscience and Human Behavior, University of California at Los Angeles, Los Angeles, CA 90095, USA. fyaghmaie@mednet.ucla.edu
Farzin
F
Yaghmaie
Omar
O
Saeed
Steven A
SA
Garan
Mark A
MA
Voelker
Hal
H
Sternberg
Paola S
PS
Timiras
D000367:Age Factors; D000375:Aging / Q000378:metabolism*; D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000166:cytology / Q000378:metabolism*; D002452:Cell Count; D047628:Estrogen Receptor alpha / Q000378:metabolism*; D005260:Female; D007031:Hypothalamus / Q000166:cytology / Q000378:metabolism; D007150:Immunohistochemistry; D051379:Mice; D008810:Mice, Inbred C57BL
D047628:Estrogen Receptor alpha