Muscarinic cholinergic modulation of hypothalamic estrogen binding sites.

Studies from other laboratories have demonstrated that agents which interact with the dopaminergic and noradrenergic neurotransmitter systems alter the concentrations of cytosolic hypothalamic estrogen receptors. These results have led to the hypothesis that catecholamine systems are involved intimately with the regulation of brain estrogen receptors. The present study was undertaken to determine if agents from a different neurotransmitter system similarly affect [3H]estradiol binding. The data presented here show that the muscarinic cholinergic agonist, bethanechol, increases the number of cytosolic hypothalamic estradiol binding sites in ovariectomized female rats by as much as 38% above control values. Pretreatment with atropine sulfate, a highly specific muscarinic antagonist, blocked the bethanechol effect. Interestingly, bethanechol failed to alter the concentration of estradiol binding sites in castrated male rats. The results of the present experiments show not only that pharmacological modulation of cytosolic hypothalamic estradiol binding sites is not limited to drugs which interact with catecholaminergic systems, but that such effects may be sex-specific.