Atropine sulfate modulates estrogen binding by female, but not male, rat hypothalamus

Studies have shown that pharmacological manipulation of the dopamine, norepinephrine and muscarinic cholinergic neurotransmitter systems modulates the number of neural estrogen binding sites. Previously, we reported that the muscarinic agonist, bethanechol, increased estrogen receptor binding by hypothalamic cytosols from female, but not male, rats. Moreover, pretreatment with atropine prevented the bethanechol-induced effect. The experiments reported here were executed with the expectation that atropine alone would either decrease or fail to alter estrogen binding. However, the present data show that atropine increases estrogen binding by female, but not male, hypothalamic cytosols. Thus, it appears that a muscarinic antagonist and agonist can similarly affect the concentration of estrogen binding sites in female rat hypothalamus.