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Estradiol Regulation of α 1b ‐Adrenoceptor mRNA in Female Rat Hypothalamus‐Preoptic Area
Author(s) -
Karkanias G. B.,
Ansonoff M. A.,
Etgen A. M.
Publication year - 1996
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1046/j.1365-2826.1996.04716.x
Subject(s) - medicine , endocrinology , hypothalamus , preoptic area , ovariectomized rat , biology , messenger rna , hormone , chemistry , gene , biochemistry
Estradiol treatment for 48 h increases the density of α 1B ‐adrenoceptors in the hypothalamus‐preoptic area of ovariectomized female rats by five‐ to six‐fold. Present studies tested the hypothesis that estradiol elevation of hypothalamus‐preoptic area α 1B ‐adrenoceptor density is correlated with increased levels of mRNA for this receptor. We developed a semiquantitative reverse transcriptase‐polymerase chain reaction (RT‐PCR) protocol for measuring brain α 1b ‐adrenoceptor mRNA. The primers chosen yielded the predicted 409 base pair PCR product when used to amplify authentic α 1b ‐adrenoceptor cDNA. The identity of the RT‐PCR products from rat brain was confirmed by restriction digest analysis and sequencing. Moreover, there was a good correlation between the levels of α 1b ‐adrenoceptor mRNA measured by RT‐PCR in liver, whole brain and cerebellum with previous measurements using Northern blots and RNAse protection assays. We then performed RT‐PCR on total RNA from hypothalamic‐preoptic area tissue taken from ovariectomized control rats and from ovariectomized rats injected once or twice with 2 μg of estradiol benzoate at 24 or 24 and 48 h before sacrifice. Exposure to estradiol for either 24 or 48 h significantly increased levels of α 1b ‐adrenoceptor mRNA by 86–110% in the hypothalamus‐preoptic area of ovariectomized female rats when compared to oil‐treated controls. We also examined whether estradiol regulates α 1b ‐adrenoceptor mRNA in the cortex. Cortical α 1b ‐adrenoceptor mRNA levels were reduced to approximately 20% of control levels when measured 24 h after hormone injection. A similar decrease in cortical α 1b ‐adrenoceptor mRNA was observed 48 h after estrogen administration. In summary, estradiol treatment significantly increases the level of α 1b ‐adrenoceptor mRNA in the hypothalamus‐preoptic area, a brain region involved in the control of reproductive function. In the cortex, a brain region with relatively few estrogen receptors, the same estrogen treatment reduces α 1b ‐adrenoceptor mRNA levels.