Sf. Chiu et Pm. Wise, PROLACTIN RECEPTOR GENE-EXPRESSION IN SPECIFIC HYPOTHALAMIC NUCLEI INCREASES WITH AGE, The journals of gerontology. Series A, Biological sciences and medical sciences, 51(3), 1996, pp. 220-224
Increasing prolactin levels or increasing responsiveness to prolactin
may contribute to reproductive aging by influencing the secretory patt
erns of hypothalamic GnRH, pituitary gonadotropins, and/or ovarian ste
roids. Some studies have documented changes in the levels of prolactin
in peripheral plasma. The goal of this study was to determine whether
prolactin receptor mRNA levels in the brain change with aging, which
may lead to increasing responsiveness to prolactin. Young (2-4 months)
and middle-aged (9-11 months), demonstrating 3 consecutive estrous cy
cles, and old (16-19 months) and very old (20-21 months) rats, exhibit
ing repeated pseudopregnancies, were bilaterally ovariectomized. They
were implanted with Silastic capsules containing estradiol-17 beta one
week later, and killed 2 days after capsule implantation. Changes in
prolactin receptor gene expression were assessed using in situ hybridi
zation. The level of prolactin receptor mRNA in choroid plexus, perive
ntricular area of the preoptic muscles, and arcuate nucleus increased
significantly by the time the animals were old. In the lateral ventrom
edial nucleus, prolactin receptor gene expression did not change signi
ficantly during aging, even in the oldest group of rats. These finding
s suggest that changes in the prolactin receptor gene may influence th
e ability of prolactin to exert effects and may allow animals to be mo
re responsive to prolactin than young rats.