Noradrenergic regulation of cytosol estrogen receptors in female rat hypothalamus: possible role of alpha 2-noradrenergic receptors.
Because of the previous work demonstrating that the alpha 1-noradrenergic receptor antagonist, prazosin, decreases the concentration of cytosol estrogen receptors in rat mediobasal hypothalamus, a series of experiments was performed to determine the specificity of this effect to the alpha 1-noradrenergic system. Injection of the alpha 2-noradrenergic antagonist, yohimbine, caused a decrease in the concentration of estrogen receptors in mediobasal hypothalamus. In addition, the down-regulation of cytosol estrogen receptors by either the alpha 1-noradrenergic antagonist, prazosin, or the alpha 2-noradrenergic antagonist, yohimbine, could be blocked by pretreatment with the alpha 2-noradrenergic agonist, clonidine. The alpha 1-noradrenergic agonist, phenylephrine, was ineffective in blocking the effects of the alpha 1-noradrenergic antagonist, prazosin. These results add further support to the hypothesis that the alpha-noradrenergic system modulates the concentration of cytosol estrogen receptors in the rat hypothalamus. They suggest that the modulation may occur by way of alpha 2-noradrenergic receptors in addition to, or instead of, alpha 1-noradrenergic receptors.
D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D003000:Clonidine / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism*; D005260:Female; D007031:Hypothalamus / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism / Q000502:physiology*; D009994:Osmolar Concentration; D010656:Phenylephrine / Q000494:pharmacology; D011224:Prazosin / Q000037:antagonists & inhibitors / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D011960:Receptors, Estrogen / Q000187:drug effects / Q000378:metabolism*; D015016:Yohimbine / Q000037:antagonists & inhibitors / Q000494:pharmacology
D011942:Receptors, Adrenergic, alpha; D011960:Receptors, Estrogen; D010656:Phenylephrine; D015016:Yohimbine; D003000:Clonidine; D009638:Norepinephrine; D011224:Prazosin